The role of receptor-stimulated inositol phospholipid hydrolysis in the autonomic nervous system

Pharmac. Ther. Vol.38, pp. 387 to 417, 1988

0163-7258/88$0.00+ 0.50 Copyright© 1988PergamonPressplc

Printed in Great Britain.All rightsreserved Associate Editor: T. C. CUNNANE

THE ROLE OF RECEPTOR-STIMULATED INOSITOL PHOSPHOLIPID HYDROLYSIS IN THE AUTONOMIC NERVOUS SYSTEM STEPHEN P. WATSON* and PHILIP P. GODFREY~ tDepartment of Pharmacology, University of Oxford, South Parks Road, Oxford OX I 3QT, U.K. *Department of Clinical Pharmacology, Radcliffe Infirmary, Woodstock Road, Oxford 0)(2 6HE, U.K.

ABBREVIATIONS PI PIP PIP2 Ins 1,4,5-triP Ins 1,3,4-triP Ins 1,3,4,5-tetraP

Phosphatidylinositol Phosphatidylinositol 4-monophosphate Phosphatidylinositol 4,5-bisphosphate Inositol 1,4,5-trisphosphate Inositol 1,3,4-trisphosphate Inositol 1,3,4,5-tetrakisphosphate

1. I N T R O D U C T I O N This review summarises the recent developments in our understanding of the inositol phospholipid pathway with emphasis on its role in the autonomic nervous system. The inositol phospholipid pathway is described and the evidence supporting second messenger roles for diacylglycerol and inositol trisphosphate is presented (Section 2). The role of inositol phospholipid hydrolysis in tissues innervated by the autonomic nervous system, i.e. smooth muscle, heart and exocrine glands (Section 3) and within the autonomic nerves themselves, is discussed (Section 4). Possible targets for therapeutic intervention are suggested (Section 5). 2. T H E I N O S I T O L P H O S P H O L I P I D P A T H W A Y The general features of the biochemistry and pharmacology of receptor-mediated metabolism of the inositol-phospholipids have been worked out using a wide variety of different tissues and cell-lines. Comprehensive lists of tissues and their cell surface receptors coupled to phospholipase C can be found in several excellent reviews (Michell, 1975; Berridge, 1984; Berridge and Irvine, 1984; Downes and Michell, 1985; Hokin, 1985; Fisher and Agranoff, 1987). 2.1. HISTORICALDEVELOPMENTOF THE INOSITOL PHOSPHOLIPIDPATHWAY More than 30 years have passed since the initial observations by Hokin and Hokin (1955) of acetylcholine-stimulated [32p]orthophosphate incorporation into phosphatidylinositol (PI) and phosphatidic acid in pigeon pancreas. This observation was subsequently refined and extended to many other tissues but the importance of this 'PI' response remained undefined (for review of early experiments see Hokin, 1985). In the mid-1970s Lapetina and Michell (1973) hypothesised that this response may be related to the mobilisation of intracellular Ca 2+. This idea was subsequently expanded upon by Michell (1975) in a monumental review which generated enormous worldwide efforts aimed at testing this hypothesis. Michell noted that all receptors which evoke a 'PI' response also stimulate an increase in free intracellular Ca 2+, and he hypothesised that it was the 387

388

S. P. WATSON and P. P. GODFREY

hydrolysis of PI which led to this increase in Ca 2+. At the turn of the present decade, however, the concept that PI hydrolysis is the initial event which takes place following receptor activation was brought into question following observations that the polyphosphoinositides are metabolised more rapidly than phosphatidylinositol (Abdel-Latif et al., 1977; Michell et al., 1981). Subsequently, Berridge (1983) demonstrated that inositol bisphosphate and inositol trisphosphate are generated prior to inositol monophosphate following agonist stimulation, and he therefore suggested that inositol trisphosphate was ideally suited to be the second messenger involved in Ca 2+ mobilisation. Direct support for his hypothesis was then rapidly provided by the studies of Streb et al. (1983) and Burgess et al. (1984) following the purification of inositol trisphosphate from red blood cells by Irvine using the procedure of Downes et al. (1982). During the late 1970s and early 1980s Nishizuka and his colleagues identified a novel protein kinase named protein kinase C (for review see Nishizuka, 1984). An important breakthrough was made when it was realised that the activity of this kinase could be enhanced by 1,2-diacylglycerol, the other product of inositol phospholipid hydrolysis (Nishizuka, 1983, 1984). This led to the hypothesis that receptor-stimulated inositol phospholipid hydrolysis induces cellular activation through the synergistic interaction of Ca 2+ and protein kinase C (Nishizuka, 1983, 1984). Evidence for this model was obtained from studies on the human platelet (Kaibuchi et al., 1983). Subsequently, it has been shown that the two limbs of this second messenger pathway do not always interact in a synergistic manner; additive, negative feedback and independent interactions have all been described. 2.2. METABOLISMOF THE INOSITOLPHOSPHOLIPIDSAND THE PRODUCTION OF SECONDMESSENGERS Research into the metabolic pathways of the inositol lipids has been continuous since the discovery of PI by Folch (1942). PI (depicted in Fig. l) is a glycerolipid with fatty acids, usually stearate and arachidonate (Van Rooijen et al., 1985), esterified onto the sn-1 and sn-2 positions respectively, m y o - I n o s i t o l is attached, via a phosphodiester bond, to the sn-3 position of the glycerol molecule. PI can be phosphorylated by PI-kinase to form phosphatidylinositol 4-monophosphate (PIP) which can be further phosphorylated by PIP-kinase to yield phosphatidylinositol 4,5-bisphosphate (PIP2); PIP2 can be converted back to PI via specific phosphomonoesterases (for reviews see Irvine, 1982; Fisher and Agranoff, 1987). The interconversion of PI to PIP can take place within the plasma membrane or in membranes of intracellular organelles. The conversion of PIP to PIP2 takes place only in the plasma membrane (Seyfred and Wells, 1984; Lundberg et al., 1985; Phosphatidylinositoi CH2OOCRl(stearic)

I

(ar ac h.) R 2 C O 0 =,- C'= H

~

OH OH

Phospholipase C

myo-lnositol 1,4,5-triphosphate

,OH OH40--~(O?,o- o.

-o.O ,;P-o-F

o.

u.

HO

FIG. 1. The structure of phosphatidylinositol and

myo-inositol

1,4,5-trisphosphate.

lnositol phospholipid hydrolysisin the autonomic nervous system

389

Cockcroft et al., 1985). There is a rapid recycling of PI to PIP2 and PIP2 back to PI (the so-called futile cycle) and, as a consequence, the phosphates in positions 4 and 5 come into rapid (less than 60 min) isotopic equilibrium with the ATP pool in tissues prelabelled with [32p]orthophosphate. In contrast, the incorporation of [32p]orthophosphate into position 1 requires de novo synthesis of PI, which is a much slower process. PI accounts for about 5-10% of membrane phospholipids, while PIP and PIP2 are present in substantially lower quantities, each making up between 1 to 10% of the total PI pool (Downes and Michell, 1982). Activation of cells by a ligand results in an initial phospholipase C mediated cleavage of PIP2 to give inositol 1,4,5-trisphosphate (Ins 1,4,5-triP) and 1,2-diacylglycerol, both of which act as intracellular second messengers. This breakdown of PIP2 is very rapid and a substantial reduction in [32p]PIP2, and increase in [3H]inositol trisphosphate can be observed within 5 sec after agonist addition (Michell et al., 1981; Weiss et al., 1982; Berridge, 1983; Downes and Wusteman, 1983; Martin, 1983; Dougherty et al., 1984; Watson et al., 1984). Although a rapid, early hydrolysis of PIP2 is well documented, it is controversial whether PI and PIP are also hydrolysed by phospholipase C. Kinetic analysis of the formation and degradation of inositol phosphates has indicated that, at very early times, PIP may also be hydrolysed by phospholipase C in addition to PIP2 (Berridge, 1983; Downes and Wusteman, 1983; Aub and Putney, 1984). These studies suggested, however, that PI itself is not broken down by phospholipase C at these early times, and that the reduction in PI levels seen in stimulated tissues (Hokin-Neaverson, 1977; Jones et al., 1979) is due to replenishment of the polyphosphoinositide pool. There is some evidence, however, from work in platelets (Wilson et al., 1985), hepatocytes (Litosch et al., 1983) and pituitary cells (Imai and Gershengorn, 1986) for a switch from PIP2 hydrolysis to PI hydrolysis by phospholipase C at later times of stimulation. Whether this occurs in all tissues, however, and to what extent is uncertain. It may be that the frequency and magnitude of this mechanism will depend on the relative importance of the two limbs of this second messenger system at both early and later times of stimulation. For example, in GH3 pituitary cell line secretion is initially thought to be a Ca2+-dependent process while at later times it appears to be related to activation of protein kinase C (Martin and Kowalchyk, 1984a,b). The enzyme activity involved in the breakdown of the inositol phospholipids is a phosphoinositide-specific phospholipase C. Phospholipase C activity resides in both cytosolic and membrane compartments in most cells and has the capacity to hydrolyse all of the phosphoinositides (Irvine, 1982). However, under conditions resembling those found in the cytoplasm of intact cells (neutral pH; free Ca 2+ concentration of about 100 nM; ions at intracellular concentrations) the enzyme preferentially attacks PIP2 (Irvine et al., 1984a; Wilson et al., 1984). Multiple forms of the enzyme exist (Hoffman and Majerus, 1982; Low et al., 1984) and it is unclear which form is involved in agonist-stimulated inositol phospholipid hydrolysis and whether it is cytosolic or membrane bound. If the cytosolic phospholipase C is involved in agonist-stimulated inositol phospholipid hydrolysis it must be able to associate rapidly with the membrane following receptor activation. The hydrolysis of PIP2 by a partially purified preparation of phospholipase C liberates Ins 1,4,5-triP (for structure see Fig. 1; the numbers refer to the positions of the phosphates on the inositol ring) and a small amount of cycIns 1,4,5-triP (Wilson et al., 1986). The physiological importance of the cyclic isomer, however, is uncertain since conflicting reports exist whether this isomer is formed following receptor activation in intact tissues (c.f. Ishii et al., 1986 and Hawkins et al., 1987). Ins 1,4,5-triP undergoes two routes of metabolism. It is either dephosphorylated to inositol 1,4-bisphosphate, or phosphorylated to inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5-tetraP) (Batty et al., 1985; Irvine et al., 1986a; Downes et al., 1986). The latter pathway has been shown to be activated following the release of Ca 2+ in intact cells and may therefore represent a homeostatic process preventing the excessive release of intracellular Ca 2+ (Biden and Wollheim, 1986; Roussier et al., 1987; Yamaguchi et al., 1987). Similarly, the activity of inositol trisphosphatase in permeabilised porcine artery has been shown to be stimulated by an increase in

390

S.P. WATSONand P. P. GODFREY

Ca 2+ from 0.1 #M to 1/~M (Sasaguri et al., 1985). Ins 1,3,4,5-tetraP is dephosphorylated to inositol 1,3,4-trisphosphate (Ins 1,3,4-triP) (Downes et al., 1986; Hawkins et al., 1986). Ins 1,3,4-triP and Ins 1,4,5-triP can be separated by high performance liquid chromatography but not by simple anion exchange on Dowex columns (Irvine et al., 1984b). Since the majority of studies discussed in this review have separated inositol phosphates using Dowex columns the term inositol trisphosphate will be used to represent the mixture of the two isomers. Ins 1,4,5-triP and Ins 1,3,4-triP are both sequentially dephosphorylated to a variety of inositol bisphosphates and monophosphates (Storey et al., 1984; Drummond, 1987). Within the first 5 sec following agonist stimulation there is a marked formation of Ins 1,4,5-triP, Ins i,4-bisP and Ins 1,3,4,5-tetraP (Batty et al., 1985; Sugiya et al., 1987; Trimble et al., 1987a). In contrast the formation of Ins 1,3,4-triP and other inositol bisphosphates and monophosphates lags behind and their levels do not usually increase during the first 10see following agonist stimulation (Burgess et al., 1985; Downes et al., 1986). Ins 1,3,4-triP is metabolised at a much slower rate than Ins 1,4,5-triP and consequently after much longer periods of stimulation this isomer accounts for the majority of the radioactivity in the inositol trisphosphate fraction (Burgess et al., 1985; Irvine et al., 1985: Downes et al., 1986). This kinetic pattern of formation of inositol phosphates has bee~ observed in the parotid gland (Hawkins et al., 1986), guinea-pig ileum (Bielkiewicz. Vollrath et al., 1987), hepatocytes (Hansen et al., 1986) and pancreas (Merritt et al. 1986a). There have also been a number of reports describing the presence of inositol pentaphos. phate and inositol hexaphosphate in cells (Heslop et al., 1985), but their levels do no' increase following agonist-induced hydrolysis of inositol phospholipids. It is likely tha their function is unrelated to the inositol phospholipid cycle. The inositol phospholipid pathway is summarised in Fig. 2, and examples of receptor: found within the autonomic nervous system which stimulate inositol phospholipk metabolism are shown in Table 1.

Metabolism of Intermediates

Formationof

Action of

Second Messengers

Second Messengers

[~

Ca2+ J

I<~

:i:[<-'~:::::l::("

l~P3v"-e - ) ~ - ~ 1 , --53 , --~4 , 5~ 1 P 4

~4

Cellular Activation FIG, 2. The inosito[ phospholipid pathway. The binding of an agonist to its cell surface receptor (rec) is thought to stimulate the exchange of GTP for GDP on an associatedG-protein and thus in turn activate phospho]ipaseC (PLC). The phosphodiesteratichydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by PLC generatesthe two secondmessengersinositol 1,4,5-trisphosphate (1,4,51P3) and 1,2-diacylglycerol (DG). 1,4,5IP3 mobilises Ca 2+ from endoplasmic reticular stores and DG activates protein kinase C (PKC) leading to the phosphorylation of several cellular proteins. 1,4,5IP3 is metabolised to inositol 1,3,4,5-tetrakisphosphate (1,3,4,51P4) or to inositol 1,4-bisphosphate (1,4IP2). These products are further hydrolysed to inositol 1,3,4-trisphosphate (l,3,4-triP), a combination of inositol bisphosphates (IP2s) [including, inositol 1,4-bisphosphate (1,4IP2)] and inositol monophosphates (IPs) and finally to free inositol (I). DG is metabolised to phosphatidic acid (PA) and then to CDP-DG before being reconverted to phosphatidylinositol (PI) for phosphorylation to phosphatidylinositol 4-monophosphate (PIP) and to PIP2.

Inositol phospholipid hydrolysis in the autonomic nervous system

391

TABLE 1. Examples o f Receptors Coupled to Inositol Phospholipid Metabolism Found Within the Autonomic Nervous System

Receptor Muscarinic: MI, M2 Adrenergic: alpha-I Histamine: H1 5-HT2 Tachykinin: NKI Tachykinin: NK2 Tachykinin: NK3 Vasopressin: V1 Cholestcystokinin Secretin Angiotensin 1I NGF VIP

Tissue Heart, smooth muscle exocrine glands, ganglia Heart, smooth muscle exocrine glands Guinea-pig ileum A7r5 smooth muscle cells Guinea-pig ileum Guinea-pig myenteric plexus Hamster urinary bladder Cervical ganglia Pancreas Pancreas Aorta Cervical ganglia Cervical ganglia

Reference See text See text Donaldson and Hill (1985) Doyle et al. (1986) Watson and Downes (1983) Bristow et al. (1986) Guard et aL (1988) Horwitz et al. (1986) Rubin (1984) Trimble et al. (1987b) Danthuluri and Deth (1986) Lakshamanan (1979) Audiger et al. (1986)

2.3. THE ROLE OF GTP-BINDING PROTEINS IN RECEPTOR ACTIVATION OF PHOSPHOLIPASE C

Although it is well established that receptors which activate or inhibit adenylate cyclase do so through guanine-nucleotide-binding regulatory proteins (Gilman, 1984), the evidence for a similar coupling mechanism for receptors linked to phospholipase C has only recently emerged. The first indication for the participation of a G-protein in receptor activation of phospholipase C came following the observation of Gomperts (1983) that GTP induces the activation of permeabilised neutrophils through a Ca2÷-dependent mechanism. A similar observation was subsequently observed in the human platelet by Haslam and Davidson (1984a) who further showed that this GTP effect was associated with the activation of phospholipase C (Haslam and Davidson, 1984b). This led to the hypothesis that receptors couple to phospholipase C through a novel G-protein. This idea was rapidly confirmed by the demonstration that GTP or its stable analogues, GTP-7-S or GTPp[NH]ppG, stimulate inositoi phospholipid hydrolysis in a cell free system, and that agonist-induced inositol phospholipid hydrolysis in broken membranes has an absolute requirement for GTP or its stable analogues (Cockcroft and Gomperts, 1985). More recently GTP or its stable analogues have been shown to induce, or to potentiate agonist-induced, inositol phospholipid hydrolysis in a variety of other systems including permeabilised pancreatic acinar cells (Merritt et al., 1986b), and membranes prepared from blowfly salivary glands (Litosch and Fain, 1985), hepatocytes (Wallace and Fain, 1985; Uhling et al., 1986), GH 3 cells (Lucas et al., 1985), porcine aorta (Sasaguri et al., 1985) and pancreatic islet cells (Dunlop and Larkins, 1986). The nature of the G-protein coupled to phospholipase C has been investigated using two bacterial toxins, cholera toxin (from Vibrio cholerae) and pertussis toxin (from Bordetella pertussis). Both toxins ADP-ribosylate a number of G-proteins. Cholera toxin induces the ADP-ribosylation of Gs, the G-protein responsible for receptor coupling to adenylate cyclase, leading to its permanent activation (Gilman, 1984). Cholera toxin, however, has no direct effect on receptor-stimulation of phospholipase C (Taylor and Merritt, 1986). Pertussis toxin, which ADP-ribosylates and inactivates the two G-proteins Gi, which is coupled to adenylate cyclase inhibition (Gilman, 1984), and Go, which is of unknown function (Sternweis and Robishaw, 1984), blocks phospholipase C activation in a few isolated cases, e.g. neutrophils (Brandt et al., 1985; Bradford and Rubin, 1986), and mast cells (Nakamura and Ui, 1985). In the majority of cells, however, phospholipase C activity is unaffected by pretreatment with this toxin, e.g. porcine artery (Sasaguri et al., 1986), exocrine pancreas (Merritt et al., 1986b), cultured chick heart cells (Masters et al., 1985) and pancreatic islet cells (Dunlop and Larkins, 1986), making it unlikely that G~ or Go is responsible for phospholipase C activation in these tissues.

392

S. P, WATSONand P. P. GODFREY

Among the more promising candidates for the G-protein coupled to phospholipase C are the family of ras proteins, i.e. N-ras, Harvey-ras and Kirsten-ras. These proteins have molecular weights of approx. 21 kDa and bind GTP. Increased levels of mutated forms of these proteins are found in approx. 10-20% of human cancers. The role of these proteins in the cell is poorly defined, although recent studies by Fleichsman et al. (1986) and Wakelam et al. (1986) suggest that they participate in the activation of phospholipase C. For example, in NIH 3T3 fibroblasts bombesin induces about a 16% increase in inositol phosphates during a 45-min incubation. In the same cells transformed with dexamethasone, leading to a marked change in the levels of N-ras, bombesin induces an approximation 120% increase in the formation of inositol phosphates in the same time period (Wakelam et al., 1986). The precise coupling arrangement between the surface receptor, ras protein and phospholipase C is not known, Recently a number of G-proteins with molecular weights in the region of 21 kDa29 kDa and which are distinct from the ras proteins have been identified in platelets, uterus, and brain (Evans et al., 1986; Bhullar and Haslam, 1987; Lapetina and Reep, 1987; Waldc et al., 1987). The function of these proteins in cell activation, and their relationship, if any to the activation of phospholipase C, is clearly a very important area of current research More detailed discussions of the role of G-proteins in the activation of phospholipas~ C can be found in the following reviews: Litosch and Fain (1986); Taylor and Merrit (1986); Cockcroft (1987). 2.4. THE ROLE OF DIACYLGLYCEROL AS A SECOND MESSENGER Hydrolysis of the three major inositol phospholipids, i.e. PI, PIP and PIP2, results ii the formation of an inositol phosphate and diacylglycerol. Approximately 80% of th, newly generated diacylglycerol has a stearic acid and an arachidonic acid residue il positions 1 and 2 respectively. The high lipophilicity of these fatty acid substitution prevents the passage of the diacylglycerol into the cytosol, and thus the molecule remain 'compartmentalised' in the plasma membrane. Diacylglycerol undergoes two routes o metabolism. It is either phosphorylated by diacylglycerol-kinase to phosphatidic acfi (Lapetina and Cuatrecasas, 1979) or sequentially deacylated to monoacylglycerol am glycerol (Bell et al., 1979). The relative importance of these two metabolic routes i uncertain, although recent studies in the neutrophil using an inhibitor of diacylglycerol kinase, R59022, indicate that its conversion to phosphatidic acid is the major route c metabolism in this tissue (Muid et al,, 1987). Whilst 'compartmentalised' in the plasm membrane diacylglycerol activates protein kinase C. Activation involves the translocatio of protein kinase C from the cytosol to the membrane where the enzyme forms a comple with diacylglycerol, phosphatidylserine and Ca 2+ (Nishizuka, 1984). Full activation of th enzyme can occur without an increase in intracellular Ca 2÷ (Rink et al., 1983). Th activated protein kinase C is then able to phosphorylate target proteins in the vicinity ( the membrane on serine and threonine residues (for review on protein kinase C se Nishizuka, 1984). Multiple forms of protein kinase C exist which, although highl homologous in their sequence, appear to be derived from distinct genes on separal chromosomes (Coussens et al., 1986; Ohne et al., 1986). The role of protein kinase C has been studied using a variety of membrane-permeab agents to activate the enzyme. These stimuli can be divided into three groups, examplt of which are shown in Fig. 3: short-chain diacylglycerols, e.g. dioctanoylglycerol (Lapeti~ et al., 1985) and 1-oleoyl 2-acetyl glycerol (Kaibuchi et al., 1983); phorbol esters whic contain a diacylglycerol-like moiety and are the most potent tumour promoters identifie~ e.g. phorbol dibutyrate, phorbol 12-acetate, 13-myristate (for review see Ashendel, 1985 agents which do not contain a diacylglycerol-like moiety, e.g. the tumour promote mezerein, teleocidin and aplysiatoxin (Ashendel, 1985). It is important to realise that tt greater hydrophilicities of these agents will enable their distribution to sites in the c¢ inaccessible to the endogenous diacylglycerols. The use of inhibitors of protein kinase is therefore essential to confirm a physiological role for the enzyme in responses mediate

Inositol phospholipid hydrolysis in the autonomic nervous system

~"~

o, H I

11o

393

TPA

"°" ~,~.,~o-c~° CH20H

i

TM

OAG

Lo.

Lo.

FIG. 3. The structure of several types of stimulants of protein kinase C. TPA--phorbol 12-myristate,13-acetate: OAG--l-oleoyl,2-acetylglycerol: DC8---dioctanoylglycerol.

by the above agents. At present, however, the currently available inhibitors are relatively non-specific in their action since they inhibit either by interfering with membrane structure, e.g. phenothiazines, local anaesthetics, polymyxin B, or at the level of ATP, e.g. H-7 and staurosporine (for minireview see Hidaka and Hagiwara, 1987; Watson et al., 1987). The inhibitors should only be used, therefore, with caution and the correct use of controls is essential. There are several other mechanisms which regulate the activity of protein kinase C but their functional significance is uncertain. The proteolytic breakdown of protein kinase C by Ca2÷-dependent proteases leads to activation (Kishimoto et al., 1983). The intact enzyme (approx. molecular weight is 77-80 kDa) is cleaved to sub-units of approx. 28 and 51 kDa. The former contains the binding sites for diacylglycerol, Ca z+ and phosphatidylserine, and the latter contains the catalytic sub-unit (Lee and Bell, 1986). The 51 kDa fragment retains full catalytic activity and, since it no longer requires diacylglycerol, Ca 2+ and phosphatidylserine, is able to diffuse through the cytosol and phosphorylate proteins inaccessible to the parent enzyme. Proteolytic activation of protein kinase C induced by phorbol esters has been described in platelets (Tapley and Murray, 1984) and neutrophils (Melloni et al., 1986), but the physiological relevance of this phenomenon is uncertain. The development of antibodies selective to the 28 and 51 kDa sub-units will be important in addressing this question (Parker et al., 1986). Protein kinase C is also activated by unsaturated long-chain fatty acids, e.g. arachidonic acid, and it is possible that stimulus-induced formation of these fatty acids may constitute a further pathway of activation (McPhail et al., 1984). The activity of protein kinase C can also be altered by endogenous proteins including a Ca 2+ binding protein of 40 kDa, purified from bovine brain, which acts as a potent and specific inhibitor of the enzyme (Hucho et al., 1987). Protein kinase C has been shown to phosphorylate a large number of pure or partially purified proteins, but caution should be adopted in extrapolating these results to intact cells. The choice of conditions markedly effect the degree of phosphorylation observed and in the intact cell the 'compartmentalisation' of protein kinase C will limit the number of possible substrates. It is therefore essential to investigate which proteins undergo phosphorylation in intact cells following the activation of the enzyme. Clearly many of the proteins phosphorylated by protein kinase C will depend on the function of the ceil-type in question, although there are targets which are common to most cells, including: (i) Cell-surface receptors. The phosphorylation of receptors by protein kinase C can lead to an alteration in their distribution and in the affinity of agonists and antagonists (for

394

S.P. WATSONand P. P. GODFREY

review see Sibley et al., 1987). In many instances this effect is the molecular basis of homologous or heterologous receptor desensitisation (Sibley et al., 1987). (ii) Ion channels and transporters. The activation of protein kinase C has been shown to stimulate Na+-H + exchange (Berk et al., 1987), the Na+-K÷-ATPase pump (Lynch et al., 1986), and to alter the activity of various membrane ion channels including the activation of a novel Ca 2+ channel which has so far only been identified in the central nervous system (for minireview see Kaczmarek, 1987). (iii) GTP-binding proteins. The activation of protein kinase C can lead to an increase or a decrease in the coupling of cell surface receptors to adenylate cyclase or phospholipase C. In many instance this effect is thought to be mediated by the phosphorylation of the G-protein which links the receptor to these two enzymes (Orellana et al., 1987; Watanabc et al., 1985). (iv) Autophosphorylation. The importance of autophosphorylation of protein kinase 15 is uncertain, but may be linked to the termination of the protein kinase C signal (Woll et al., 1985).

2.4.1. The Role of Ins 1,4,5-triP as a Second Messenger Ins 1,4,5-triP has been shown to release Ca z+ from endoplasmic reticulum (equivalen structure in smooth muscle is the sarcoplasmic reticulum) but not mitochondrial stores ii a wide variety of cells (Streb et aL, 1983; Burgess et al., 1984; for review see Berridge am Irvine, 1984). The mechanism of this release is uncertain. Binding sites for Ins 1,4,5-tril on intracellular organelles of adrenal cortex and liver have been described (Baukal et al. 1985; Spat et al., 1986) and the release of Ca 2÷ does not appear to require the presenc, of ATP, therefore ruling out the involvement of protein phosphorylation (Burgess et al 1984; Taylor and Putney, 1985). In rat liver (Dawson et al., 1986) and vascular smoot] muscle (Saida and van Breeman, 1987) the release of Ca z÷ by Ins 1,4,5-triP requires th presence of GTP, suggesting the involvement of a novel GTP binding protein locatec presumably, on the endoplasmic reticular membrane. A maximally effective concentration of Ins 1,4,5-triP releases approx. 50% of th non-mitochondrial stores of intracellular Ca2+; the concentration response curve takin place over the range 10-1000 nM (Streb et al., 1983; Burgess et al., 1984; Berridge an Irvine, 1984). cyclns i,4,5-triP has a similar potency to Ins 1,4,5-triP at mobilisin intracellular Ca 2+ (Majerus et al., 1986), while other naturally occurring inositol pho~ phates have either much lower potencies, i.e. Ins 1,3,4,5-tetraP, Ins 1,3,4-trip and inosiU 4,5-bisphosphate, or are inactive (all other bisphosphates and monophosphates) (Irvine al., 1986b; Burgess et al., 1984). Ca 2+ can also enter the cell from the extracellular medium through a number of differel pathways. In excitable cells Ca 2+ enters through voltage-dependent ion channels or t Na+-Ca 2+ exchange. In non-excitable cells the pathway of Ca 2+ entry is less clear and number of mechanisms have been proposed: (i) Ins 1,4,5-triP. Putney (1986b) has suggested that the release of Ca 2+ from intr; cellular stores by Ins 1,4,5-triP triggers the refilling of the store by the entry of extr~ cellular Ca 2+. The maintained presence of Isn 1,4,5-triP then promotes further relea of Ca 2+ from the store. This 'capacitative model' has been advanced to explain tl rapid refilling of Ca 2+ stores which occurs following agonist stimulation of the r parotid gland and which takes place without an increase in intracellular Ca 2+ (Poggk and Putney, 1982). The possibility that IP3 can also open Ca 2÷ channels in the plasma membrane has beq widely investigated without success except for a single study in T-lymphocytes (Kuno al Gardner, 1987). (ii) Ins 1,3,4,5-tetraP. Irvine and Moor (1986) have provided evidence that I 1,3,4,5-triP stimulates the entry of extracellular Ca ~+ in sea urchin eggs, but only followi~ the release of intracellular Ca -'+ by Ins 1,4,5-triP.

Inositol phospholipidhydrolysisin the autonomicnervous system

395

This observation suggests a possible mechanism for the refilling of the intracellular Ca 2÷ store in the 'capacitative model' proposed by Putney (1986b) and which is described above. Thus Ins 1,3,4,5-tetraP may stimulate the refilling of the intracellular Ca 2÷ store from the extracellular fluid following the emptying of the store by Ins 1,4,5-triP. In this model Ins 1,3,4,5-tetraP can only function in the presence of Ins 1,4,5-triP, which agrees with the results of Irvine and Moor (1986). (iii) Ca 2÷. The mobilisation of Ca 2÷ in the neutrophil has been shown to promote the opening of Ca 2÷ channels in the plasma membrane (von Tscharner et al., 1986). (iv) G-protein. Treatment of adrenal glomerulosa cells with pertussis toxin inhibits the entrance of extracellular Ca 2÷ induced by angiotensin II (Kojima et al., 1986), and this effect appears to be unrelated to any action of the toxin on the adenylate cyclase or inositol phospholipid pathways in this tissue (Kojima et al., 1986). The possibility that a G-protein may directly open an ion channel through which Ca 2÷ ions can pass is therefore worthy of consideration. (v) Phosphatidic acid. Phosphatidic acid is able to translocate Ca 2+ across lipid bilayers (Serhan et al., 1981) and to stimulate contraction of dispersed smooth muscle cells from the stomach of the toad Bufo marinus (Salmon and Honeyman, 1980). The hypothesis has therefore been suggested that phosphatidic acid may be a second messenger involved with Ca 2÷ entry (Putney, 1981). Arguments against a second messenger role for phosphatidic acid, however, have since emerged (Holmes and Yoss, 1983; Watson et al., 1985). It is beyond the scope of this review to discuss the above hypotheses in detail, but it should be borne in mind that there is likely to be more than one mechanism of Ca > entry. The liberated Ca 2÷ has many functions in the cell. It activates Ca 2÷ calmodulindependent kinases I and II (Nairn et al., 1985), myosin light chain kinase (Adelstein and Eisenberg, 1980) and also other calmodulin-dependent enzymes including cAMP phosphodiesterase (Hidaka et al., 1984) and phospholipase A 2. The latter enzyme liberates arachidonic acid for conversion to lipoxygenase and cyclo-oxygenase products which further alter cell activity through cell surface receptors. Some of these receptor sub-types are coupled to phospholipase C (Siess et al., 1983). The movement of many ions across cell membranes is also intimately related to changes in intracellular Ca 2÷ (Putney, 1979). For example, Ca 2÷ stimulates the opening of K ÷ channels in the parotid gland (Marier et al., 1978), lacrimal gland (Parod and Putney, 1978) and arterial smooth muscle (Benham and Bolton, 1986).

3. TISSUES INNERVATED BY THE AUTONOMIC NERVOUS SYSTEM 3.1. SMOOTHMUSCLE Contraction in smooth muscle is initiated through an elevation of intracellular Ca 2+ leading to the activation of the calmodulin-dependent enzyme, myosin light chain kinase, the phosphorylation of myosin light chains, actin-myosin cross-bridge formation and contraction (for review see Adelstein and Eisenberg, 1980). The Ca 2+ is derived from both intraceilular and extracellular sources (for reviews see Bolton, 1979; Kuriyama et al., 1982) and the relative importance of these two sources depends on the smooth muscle, and can vary with different stimuli and during the time course of the response. In electrically excitable smooth muscles, Ca 2+ can enter the cell during the action potential through transient Ca 2+ channels, and each action potential is associated with a phasic contraction. Small changes in membrane potential can alter the frequency of the action potentials in spontaneously active tissues and depolarisation can evoke potentials in quiescent tissues. Depolarisation to a more positive potential can activate sustained Ca 2+ channels (voltage sensitive Ca 2÷ channels) in electrically excitable and non-excitable smooth muscles and this can lead to a substantial entry of Ca 2+ into the cells. The voltage sensitive Ca 2+ channels are more sensitive to Ca 2+ antagonists than the transient Ca 2+ channels. J.P.T 38 3--1

396

S.P. WATSONand P. P. GODFREY

Both electrically excitable and non-excitable smooth muscles possess intracellular Ca z+ stores. Some of the stored Ca 2÷ may be bound to the inside of the plasma membrane, but most of it is thought to be held within the sarcoplasmic reticulum (Williams et al., 1985). The extent of the sarcoplasmic reticulum varies widely in different smooth muscles and can be superficial, in close contact with the plasma membrane, or more extensive, penetrating deeply into the cytoplasm. The release of Ca 2+ from the sarcoplasmic reticulum does not appear to be triggered by depolarisation per se, and two other mechanisms have been proposed, a Ca2+-activated Ca 2+ release, which could be involved in the ability of the spikes to release stored Ca 2+ (Itoh et aL, 1981) and release induced by Ins 1,4,5-triP. In normal conditions contraction in response to applied agonists, or to repetitive nerve stimulation, often consists of two stages: an initial transient (phasic) component followed by a more sustained (tonic) component. In most smooth muscles it appears that release of intracellular Ca 2+ is required for the phasic component since contraction can be observed in zero Ca2+-EGTA medium or in the presence of Ca 2+ antagonists, e.g. D600, nifedipine (Bolton, 1979; Kuriyama et al., 1982). The sensitivity of this phasic component to the removal of Ca :+ , however, varies widely in different smooth muscles. For example, in rabbit mesenteric artery the full extent of the phasic component of contraction is retained following long incubations in zero CaZ+-EGTA medium while, in contrast, ir guinea-pig ileum and taeni coli the phasic response is rapidly diminished following Ca 2+ removal and is lost within minutes (Hurwitz, 1975; Ito et al., 1979; Brading and Sneddon 1980; Itoh et al., 1983; Kanmura et al., 1983; for reviews see Bolton, 1979; Kuriyama e, al., 1982). It appears therefore that in the latter two tissues, in contrast to the rabbi~ mesenteric artery, the intracellular Ca ,-+ store is rapidly depleted in zero Ca2+-EGT~ medium. This may be related to how much of the sarcoplasmic reticulum is close to th~ synaptic membrane and how much penetrates deeply into the cytoplasm. It is difficult t~ evaluate whether the entrance of extracellular Ca 2+ contributes to the phasic response o smooth muscles which show an immediate decrease in contraction following Ca 2+ remova since this could also be related to a rapid depletion of intracellular Ca 2+. Ca -,+ entry from the extracellular fluid is required for the tonic component ofcontractio~ in most smooth muscles. Ca `,+ enters through the sustained and transient Ca 2+ channel and by N a + - C a 2+ exchange (Kuriyama et al., 1982). This Ca 2+ can either distribute to th. cytoplasm, where it will be available to activate the contractile machinery, or can be takeJ up into intracellular stores from where it can be released by Ins 1,4,5-triP or bl Ca2+-induced Ca 2+ release. The sequence of events which are thought to occur following receptor activation i~ electrically excitable smooth muscles, therefore, are as follows: there is an initial increas in action potential frequency usually triggered by the onset of depolarisation induce, through the opening of receptor-operated channels. The depolarisation may increas sufficiently to stimulate the opening of voltage-sensitive Ca 2+ channels. In non-excitabl smooth muscles there may be an absence of action potentials and the opening c receptor-operated ion channels does not lead to depolarisation except, perhaps, with ver high agonist concentrations. Receptor-stimulated hydrolysis of inositol phospholipids has been described in man types of smooth muscle or associated cell lines including artery (Lapetina et al., 1976~ Sasaguri et al., 1985; Hashimoto et al., 1986; Chiu et al., 1987), trachea (Hashimoto et al 1985; Grandardy et al., 1986; Takuwa et al., 1986), ileum (Jafferji and Michell, 197~ Watson and Downes, 1983; Donaldson and Hill, 1985), taeni caecum (Nelemans and de Hertog, 1987), uterus (Flint et al., 1986), vas deferens (Lapetina et al., 1976c; Fox an Friedman, 1987), iris (Howe et al., 1986; Akhtar and Abdel-Latif, 1986) and bladd~ (Bristow et al., 1986). In nearly all cases the hydrolysis of inositol phospholipids associated with muscle contraction, although exceptions exist (see alpha-adrenergi action on taeni coli described below). To our knowledge the only neurotransmitter whic appears to stimulate smooth muscle contraction without evoking inositol phospholipi hydrolysis is ATP, which initiates contraction through the opening of an ion channel i intimate contact with its receptor through which Na + and Ca 2+ can pass (Benham an

Inositol phospholipid hydrolysis in the autonomic nervous system

397

Tsien, 1987). An increase in receptor-induced inositol phospholipid hydrolysis may explain the mechanism of denervation supersensitivity in smooth muscle (Akhtar and AbdelLatif, 1986). A good deal of evidence indicates that the activation of smooth muscle is associated with the release of intracellular Ca 2+ (see above) and that inositol trisphosphate may be involved in this release. Ins 1,4,5-triP has been shown to mobilise Ca 2+ from the sarcoplasmic reticulum of skinned arterial smooth muscle (Suematsu et al., 1984; Suematsu et al., 1985; Somylo et al., 1985; Hashimoto et al., 1986), taeni caecum (Iino, 1987) and trachea (Hashimoto et al., 1985) and microsomes derived from uterine sarcoplasmic reticulum (Carsten and Miller, 1985). In many of these cases the release of Ca 2+ by Ins 1,4,5-triP has been shown to stimulate contraction (Somylo et al., 1985; Hashimoto et al., 1986; Walker et al., 1987). The importance of this Ins 1,4,5-triP-induced Ca 2+ release relative to Ca2+-activated Ca 2+ release in smooth muscle is uncertain and probably varies in different preparations. For tissues in which the initial increase of intracellular C a 2+ is derived from intracellular rather than extracellular sources it is possible to rule out Ca 2+ as the trigger for this initial release. Whether Ca2+-induced Ca 2+ release contributes to the further release of Ca 2+, however, is uncertain (Suematsu et al., 1985). In the taeni caecum the action of Ins 1,4,5-triP is potentiated by submicromolar concentrations of Ca 2+ (Iino, 1987), but in porcine artery the action of Ins 1,4,5-triP is inhibited by micromolar concentrations of Ca 2+ (Suematsu et al., 1984; Suematsu et al., 1985). There is little evidence to support a role for either inositol trisphosphate or protein kinase C in the regulation of receptor-operated channels or in triggering the onset of depolarisation which leads to the opening of the voltage sensitive Ca 2+ channels. The release of intracellular Ca 2+ appears to stimulate an increase in the frequency of outward currents in both excitable and non-excitable smooth muscle (Benham and Bolton, 1986). This outward current is thought to represent the oscillatory opening of K + channels in the membrane and would therefore tend to lead to hyperpolarisation. Indeed, in the guinea-pig taeni caecum the activation of alpha~-adrenoceptors stimulates inositol phospholipid hydrolysis and induces membrane hyperpolarisation through an increase in outward K + current (Nelemans and den Herzog, 1987). The activation of protein kinase C has little immediate effect on resting tension in smooth muscles (see below), suggesting that the opening of receptor operated or voltage operated C a 2+ channels is not under direct regulatory control by protein kinase C (Spedding, 1987). The role of protein kinase C in smooth muscle is uncertain. Prolonged incubations with phorbol esters in arterial smooth muscle produce a very slow contraction which usually takes between 1-3 hr to reach peak tension and has a latency of onset between 10-30 min (Rasmussen et al., 1984; Forder et al., 1985; Baraban et al., 1985; Itoh et al., 1986; Sybertz et al., 1986; Miller et al., 1986; Spedding, 1987). In some arterial muscles, e.g. coronary and ear artery, the latency of onset of this contraction is significantly decreased to approx. 5-15 rain by conditions favouring increased Ca 2+ entry (Forder et al., 1985; Miller et al., 1986) and the response is inhibited by Ca 2+ antagonists, e.g. nitrendipine (Forder et al., 1985). In other arterial smooth muscles, e.g. aorta, the contraction induced by phorbol esters appears to be largely Ca2+-independent (Sybertz et al., 1986; Spedding, 1987; Chiu et al., 1987, but see Gleason and Flaim, 1986). A slow Ca2+-independent contraction to phorbol esters is also observed in chemically skinned carotid artery and mesenteric artery (Chatterjee and Tejeda, 1986; Itoh et al., 1986). The molecular mechanism of the contractile response to phorbol esters is not known, but it does not appear to be related to the phosphorylation of myosin light chains (Chatterjee and Tejeda, 1986). Its slow nature would appear to rule out a direct role for protein kinase C in the contractile response in arterial tissue, although a modulatory role during either the phasic or tonic components of contraction is a possibility. The studies of Danthuluri and Deth (1986) provide support for such a modulatory role for protein kinase C during the tonic component of angiotensin II-induced contraction in rat aorta. The contractile response to angiotensin II and the formation of phosphatidic acid are both transient responses but, following the addition of the phorbol ester,

398

S.P. WATSONand P. P. GODFREY

tetradecanoyl-13-acetate, the normally transient contraction is converted to a more sustained, tonic pattern (Danthuluri and Deth, 1986). Similarly, in rabbit mesenteric artery and porcine carotid artery, phorbol esters cause an initial potentiation followed by inhibition of the contractile response to K + or Ca 2+ ionophore (Itoh et al., 1986). Potentiation could be observed within a few minutes following the addition of phorbol ester while inhibition was only observed after much longer periods (more than 30 min) ot the contractile response (Itoh et al., 1986). In trachea, Park and Rasmussen (1985) have shown a remarkable synergism betweer~ Ca 2+ and activators of protein kinase C. The Ca 2+ ionophores, e.g. ionomycin and A23187 produce a transient contraction in trachea while activators of protein kinase C, e.g phorbol 12-acetate, 13-myristate and mezerein, produce a slow contraction similar to thai described above on arterial tissue (Park and Rasmussen, 1985; Park and Rasmussen, 1986) When added together, however, these two sets of stimuli interact synergistically to produc( a rapid and sustained response which is very reminiscent of that seen with carbachol suggesting that protein kinase C may be involved in the tonic component of contractior (Park and Rasmussen, 1985). Synergism has also been observed in trachea betweer depolarising concentrations of K + and phorbol esters (Menkes et al., 1986b). Thi: synergism is inhibited by Ca z+ antagonists, suggesting that it is also dependent on the entr~ of Ca 2+ through voltage sensitive Ca 2+ channels. Interestingly, Menkes et al. (1986b) fount that on their own phorbol esters decreased the resting tension of the trachea. In iris smoott muscle phorbol esters and Ca 2+ ionophores also interact synergistically, although the tim, course of contraction was considerably slower compared with agonist stimulation (How~ et al., 1986). In other smooth muscles, e.g. guinea-pig ileum and guinea-pig taeni caecum, phorbe esters have no effect on either resting tension or contractile responses (Salmon et al., 1986 Spedding, 1987). Earlier reports by Baraban et al. (1985) that phorbol esters inhibi contraction in guinea-pig ileum have not been confirmed (Salmon et al., 1986). There is relatively little information regarding the proteins phosphorylated by protei: kinase C in smooth muscle. The activation of muscarinic receptors in trachea (Park an~ Rasmussen, 1986) and iris (Howe et al., 1986) stimulates the phosphorylation of sever~ proteins, many of which are also phosphorylated following challenge with phorbol estel The nature and function of most of these proteins is not known. Partially purified protei kinase C has been shown to phosphorylate caldesmon (Umekawa and Hidaka, 1985' myosin light chains (Nishikawa et al., 1983) and myosin light chain kinase (Nishikawa al., 1985) in broken cell conditions, but whether this also occurs following cell activatio and its importance is uncertain. In iris smooth muscle phorbol esters stimulate th phosphorylation of myosin light chains but the magnitude of this effect is only 50% ( that induced by carbachol, and the dependence on the entrance of extraceUular Ca 2 suggests that it may be an indirect action (Howe et al., 1986, 1987). In porcine caroti artery (Chatterjee and Tejeda, 1986) and trachea (Park and Rasmussen, 1986) phorb( esters induce a small but significant phosphorylation of myosin light chains which appeal to be unrelated to the onset of contraction (Chatterjee and Tejeda, 1986). It is clearl essential to compare the sites of phosphorylation of myosin light chains by both protei kinase C and myosin light chain kinase with those observed in intact smooth muscle. I the platelet, protein kinase C and myosin light chain kinase phosphorylate myosin ligl chains at distinct sites (Nawa et al., 1983). In summary, there is no convincing evidence to suggest a direct role for protein kina: C in the initiation or termination of contraction in smooth muscle, although the studi~ of Park and Rasmussen (1985), showing the remarkable synergism between prote~ kinase C and Ca 2+ mobilisation in the trachea, are worthy of further investigatio: Protein kinase C is likely to indirectly modify contraction in smooth muscle, however, phosphorylating cell surface receptors or their associated G-proteins. For exampl phorbol esters have been shown to inhibit inositol phosphate and cAMP formatic induced by cell surface receptors in various smooth muscles (Cotecchia et al., 1985; Lee: Lundberg et al., 1985; McMillan et al., 1986; Owen, 1986; Aiyer et al., 1987). Prote

Inositol phospholipidhydrolysisin the autonomic nervous system

399

kinase C may also modify contraction through the stimulation of Na÷-H ÷ exchange leading to an increase in intracellular pH (Berk et al., 1987).

3.2. HEART There have been a number of recent reports describing the ability of cell surface receptors, e.g. alpha-adrenergic, muscarinic, vasopressin and angiotensin II, to stimulate the hydrolysis of inositol phospholipids in atrial and ventricular muscle (Brown and Brown, 1984; Poggioli et aL, 1986; Leung et al., 1986; Otani et al., 1986; Quist and Satumtira, 1987). Similarly, Poggioli et al. (1986) have reported that K*-depolarisation or electrical stimulation (five stimuli in 15 sec) triggers inositol phospholipid hydrolysis in ventricular tissue; Quist and Satumtira (1987), however, were unable to find any effect of electrical stimulation on inositol phospholipid metabolism in papillary muscle, even though a wide range of stimulation frequencies (0.5-2 Hz) and long incubation periods (15~5 min) were used. Similarly, we have been unable to find any effect of electrical stimulation on inositol phospholipid metabolism in guinea-pig ventricles even though a wide range of stimulation parameters were tried (Stoker and Watson, unpublished). The physiological importance of inositol phospholipid metabolism in cardiac tissue is uncertain. The majority of studies have reported that Ins 1,4,5-triP is unable to stimulate the release of Ca 2÷ from cardiac sarcoplasmic reticulum (Movesian et al., 1985). In contrast, however, Fabiato (1986) has reported that Ins 1,4,5-triP release Ca 2÷ from the sarcoplasmic reticulum of skinned heart cells and that the time course of this release is approximately twenty times slower than Ca2*-induced Ca 2÷ release. It would appear therefore that Ca 2÷ rather than inositol trisphosphate is likely to cause the release of intracellular Ca 2÷ in the heart, although a modulatory role for inositol trisphosphate should not be ruled out (Ochs, 1986). There is relatively little data describing the effect of protein kinase C activation in cardiac tissue. The activation of protein kinase C leads to the marked phosphorylation of a 15 kDa protein associated with the sarcolemma of unknown function (Presti et al., 1985). In addition, the activation of protein kinase C by phorbol ester or by 1-oleoyl, 2-acetyl glycerol decreases the number and affinity of binding sites for [3H]CGP-12177, a beta-adrenergic ligand (Limas and Limas, 1985). This effect is associated with an increase in the number of CGP-12177 binding sites in a cytosol fraction devoid of plasma membrane markers (Limas and Limas, 1985), indicating that protein kinase C promotes the removal of beta-adrenergic receptors from the plasma membrane, presumably as a consequence of receptor phosphorylation. A similar phenomenon has been reported for beta-receptors in other tissues (Sibley et al., 1984). The physiological relevance of this 'heterologous desensitisation' of beta-receptors in cardiac tissue is uncertain since it is not yet known whether this effect occurs following receptor-stimulated hydrolysis of inositol phospholipids. The functional consequences of the activation of receptors linked to inositol phospholipid hydrolysis in the heart is controversial. There are reports that alpha 1-adrenergic receptors increase the force of contraction and that this may result from an increase in the slow inward Ca 2÷ current and an increased sensitivity of the myofibrils to Ca 2÷ (for review see Bruckner et al., 1985). This inotropic effect of alpha-receptors is much smaller in magnitude and qualitatively distinct from that induced by beta-receptors. The molecular mechanisms underlying this action are not known, but clearly the possible role of inositol trisphosphate and diacylglycerol in mediating these effects is an important area of future research. The role of muscarinic-stimulated inositol phospholipid metabolism in cardiac tissue is difficult to study in isolation since muscarinic receptors also inhibit the formation of cAMP in this tissue (Brown and Brown, 1984), and it is this latter effect which probably accounts for the majority of the actions mediated by muscarinic receptor activation.

400

S.P. WATSONand P. P. GODFREY 3.3. EXOCRINE GLANDS

In recent years the exocrine glands have provided popular model systems to study the relationships between receptor activation and physiological cellular responses. The main reasons for this are the electrical inexcitability of the cells thus, biochemical responses are not complicated by electrical events; and the physiological simplicity of the glands so that viable homogeneous in vitro preparations can be easily produced and investigated. In each of the exocrine tissues, the salivary glands (of which the rat parotid glands has been the most extensively studied), the exocrine pancreas, the lacrimal glands, the sweat glands and gastric mucosal cells, the major physiological response of the cell is the secretion of protein and water. The biochemical events linking receptor activation and the secretion of protein and water have been termed stimulus-secretion coupling (Rubin, 1974) and stimulus-permeability coupling (Putney, 1979), respectively. It has recently become clear that turnover of the phosphoinositides and the production of second messengers derived from PIP2 play important roles in these responses. Breakdown of PIP2 and formation of Ins 1,4,5-triP has been observed in salivary glands in response to stimulation with muscarinic cholinergic (Weiss et al., 1982; Irvine et al.. 1985; Downes et al., 1986; Sugiya et al., 1987), alphal-adrenergic (Weiss et al., 1982; Aul~ and Putney, 1985; Doughney et al., 1987), 5-HT (Berridge et al., 1983) and substance F agonists (Weiss et al., 1982; Sugiya et al., 1987). Similar responses occur in lacrimal glands to muscarinic cholinergic and alpha-adrenergic stimulation (Godfrey and Putney, 1984', and in pancreatic acinar cells following activation by muscarinic cholinergic agonist~, (Rubin et al., 1984; Merritt et al., 1986a) or by cholecystokinin (Lin et al., 1986) or iL, synthetic analogue caerulein (Rubin, 1984). In each of these tissues, the initial agonist-mediated event is a breakdown of PIP2 to yield the two second messengers Ins 1,4,5-triP and diacylglycerol (Downes et al., 1986; Merritt et al., 1986a, Sugiya et al., 1987). Another early consequence of receptor activation in a number of cell types is a rise ir free arachidonic acid levels, resulting from activation of phospholipase A 2 o r diacylglycerol-lipase. Phospholipase A 2 is a Ca2+-dependent enzyme and is thought to be activated by the rise in intracellular Ca 2+ following receptor stimulation (Billah et al. 1980). The arachidonic acid produced is then used to synthesise prostaglandins anc leukotrienes, which have a wide variety of physiological actions (Moncada and Vane 1978). Interest in a role for arachidonate products in exocrine gland function increasec when it was found that phospholipase A 2 w a s activated following receptor-stimulatior in rat pancreas (Halenda and Rubin, 1982) and that in mouse pancreas exogenou~ arachidonate and prostaglandins can stimulate amylase release (Marshall et al., 1980) However, others have found that exogenous arachidonate and inhibitors of prostaglandir and leukotriene synthesis had no effect on either protein secretion or K + fluxes in eithe~ rat parotid, lacrimal or pancreas cells (Putney et al., 1981) and suggested that the earlie: effects in mouse pancreas were due to arachidonate acting on ductal cells (Putney et al. 1981). Although the metabolism of the inositol phosphates and inositol lipids in exocrin~ cells have been studied in considerable detail there is much less information on th~ mechanisms by which Ins 1,4,5-triP and diacyiglycerol produce the physiologica responses, secretion of water electrolytes and proteins. The sequence of events tha follow activation of PI-linked receptors in exocrine glands is thought to be as follows breakdown of PIP2 leads to the production of the second messengers Ins 1,4,5-triP Ins 1,3,4,5-tetraP and diacylglycerol. Ins 1,4,5-triP (and perhaps Ins 1,3,4,5-tetraP) the~ act to elevate Ca + release from the endoplasmic reticulum and calcium influx from th, extracellular space. The increase in Ca z+ then stimulates a K + efflux across the basolatera membrane which results in a chloride rich secretion of fluid into the luminal space Diacylglycerol activates protein kinase C and enhances the phosphorylation of severa cellular proteins. The activation of protein kinase C and the elevation of Ca 2+ interac synergistically to bring about, via an unknown mechanism, the exocytosis of the proteil components of the secretion.

Inositol phospholipid hydrolysis in the autonomic nervous system

401

It has long been known that Ca 2+ ions are an absolute requirement for stimulation of exocrine gland secretion. Following receptor activation there is a rapid biphasic mobilisation of calcium (internal release followed by influx; Putney, 1979). There is good evidence that the internal release is due to the action of Ins 1,4,5-triP. In pancreatic cells permeabilised by a low Ca 2+ technique Ins 1,4,5-triP caused a rapid release of sequestered Ca 2+ into the medium; the ECs0 for Ins 1,4,5-triP was about 0.4/~M (Streb et al., 1983). The Ca 2+ was released from a non-mitochondrial site, probably the endoplasmic reticulum (Streb et al., 1983). Similar results, using Quin 2 to measure the released C a 2+, were found in permeabilised parotid cells where a rapid increase in Quin 2 fluorescence was observed following addition of Ins 1,4,5-triP (Putney et al., 1986a). Although Ins 1,4,5-triP has been shown to mobilise Ca 2+ in permeabilised cells there is still no direct evidence that it does so in intact exocrine cells. Recently, Merritt and Rink (1987) have shown that Ca 2÷ levels rise in parotid cells within 100msec following stimulation with the muscarinic agonist carbachol. Currently the earlier time point at which Ins 1,4,5-triP levels have been measured is 5 sec (Hawkins et al., 1986). Clearly changes in Ins 1,4,5-triP levels within 100 msec of stimulation need to be shown for this proposed transduction pathway to be substantiated. In the parotid cell, using a technique called "cross-receptor inactivation" (Putney, 1979), it has been shown that the three separate receptors (muscarinic, alphal-adrenergic and tachykinin) each regulate the same Ca 2+ pool (Putney, 1977). A similar lack of additivity between the agonists was later observed for PI turnover (Weiss and Putney, 1981) and suggests that the different receptors regulate a common step (either the G-protein or phospholipase C) in the phosphoinositide pathway. An interesting characteristic of the receptor-regulated Ca2+pool in parotid glands is that extracellular Ca 2+ is required to refill the internal pool once it is discharged by an agonist (Putney, 1986a). When a cholinergic agonist was applied in the presence of extracellular E G T A a characteristic transient C a 2+ response occurred (Aub et al., 1982; Merritt and Rink, 1987). If the cholinergic stimulus was removed and substance P applied, no response was seen unless the extracellular Ca 2+ was replaced for at least 2 min (Aub et al., 1982). If the extracellular Ca 2+ is replaced in the absence of any stimulus no increase in intracellular Ca 2+ is observed (Poggioli and Putney, 1982). Taken together, the data suggests that the receptor-regulated Ca 2÷ pool can communicate directly with the extracellular space. These observations led Putney (1986b) to propose the 'capacitative' model for receptor-mediated Ca 2+ influx (see Section 2.5). Following receptor activation there is a large transient increase in internal Ca 2+ (due to release of intracellular stores), then a smaller sustained phase which is dependent on extracellular Ca 2÷ (Putney, 1979; Merritt and Rink, 1987). The next stage in the physiological response of the cell following the rise in intracellular free Ca 2÷ is a net efflux of K + ions. By using S6Rb+ as a tracer, transient and sustained phases of K + efflux, similar to the Ca 2+ response, have been observed in parotid and lacrimal though not pancreatic acinar cells (Putney, 1979). Electrophysiological studies have indicated that K + efflux is through Ca2+-activated K + channels (Petersen and Maruyama, 1984) which are sensitive to internal Ca :+ (Suzuki et al., 1985); a rise in intracellular free C a 2+ increasing the open-state probability of the channel (Petersen, 1986). These observations led Petersen (1986) to formulate a hypothesis regarding the mechanism by which Ca 2+ levels modulate fluid secretion. Secretagogues evoking an increase in internal Ca 2+ activate K + and CI channels causing a loss of cellular KC1. The KC1 is taken up via a N a + - K + - 2 C I co-transport mechanism in the basolateral membrane and the Na + uptake activates Na+-K+-ATPase. The three transport proteins (K + channels, Na+-pump and co-transporter) act together as an electrogenic C1- pump and CI- exits into the lumen via luminal Ca 2÷ activated C1- channels; Na + follows through the paracellular shunt pathway. When stimulation stops the K + and C1- channels close and the N a + - K + pump together with the co-transporter operate as a KC1 pump, restoring the lost intracellular KCI and stopping secretion (Petersen, 1986).

402

S.P. WATSONand P. P. GODFREY

In addition to activating ion channels phosphoinositide-linked receptors also enhance protein secretion. In vitro this secretion is assayed by following the release of alpha-amylase into the medium. In salivary glands the major mechanism by which amylase is secreted is through activation of beta-adrenergic receptors leading to enhancement of cAMP levels (Butcher and Putney, 1980; Machado-de-Domenech and Soling, 1987). However, activation of muscarinic, alphal-adrenergic and substance P receptors also enhances amylase secretion and this is via a cAMP independent mechanism (Leslie et al., 1976). Activation of muscarinic receptors brings about a translocation of protein kinase C from cytosol to particulate cellular fractions (Wooten and Wrenn, 1984, Machado-de-Domenech and Soling, 1987). The activation of protein kinase C results in the phosphorylation of a distinct set of proteins (Burnham et al., 1986), most of which are of unknown function, although it has been recently found that Na+-K+-ATPase is phosphorylated by protein kinase C (Lynch et al., 1986; Collins et al., 1987; Hootman et al., 1987). The Na+-K +ATPase is intimately involved in the regulation of ion fluxes (Petersen, 1986) so, although protein kinase C is not directly involved in activating ion movements (Putney et al., 1984), it may have 'downstream' regulatory effects. Phorbol esters have been shown to evoke amylase secretion in both rat parotid and rat pancreas and in both circumstances the response is independent of Ca 2+ (Putney et al., 1984; Merritt and Rubin, 1985). cAMP is not involved in this effect, since phosphodiesterase inhibitors do not potentiate the response (Putney et al., 1984). When submaximal concentrations of phorbol ester and calcium ionophore are given in combination there is greater than additive secretion (Putney et al., 1984; Merritt and Rubin, 1985). This synergistic effect between Ca 2+ and protein kinase C appears to be a widespread phenomenon (Nishizuka, 1984) and is consistent with the idea that secretion is activated by the combined effects of both the IP3 and diacylglycerol activated pathways (Putney, 1986). In conclusion, activation of phosphoinositide-linked receptors in exocrine glands enhances the production of two second messenger, Ins 1,4,5-triP and diacylglycerol. Ins 1,4,5-triP elevates intracellular free Ca 2+ which then opens membrane ion channels resulting in movement of water and electrolytes. Diacylglycerol activates protein kinase C to phosphorylate various cellular proteins which, in concert with Ca 2+, provoke enzyme secretion. 4, ROLE OF THE INOSITOL PHOSPHOLIPID PATHWAY IN POST-GANGLIONIC NEURONES 4.1. GANGLIA Although receptors that stimulate the turnover of inositol phospholipids have beer studied extensively in the central nervous system at both the pharmacological anc electrophysiological levels, there is much less information on inositide linked receptors ir peripheral nerves. The primary transmission of information through sympathetic ganglia is by rapk cholinergic action via nicotinic receptors. These receptors are not coupled to inosito phospholipid turnover (Pickard et al., 1977; Briggs et al., 1985). However, there ar~ muscarinic receptors on the cell body, and several years ago it was shown that cholinergi( agonists stimulate incorporation of 32p into PI in cervical ganglia and that this respons( is blocked by atropine (Lapetina et al., 1976b; Hawthorne and Pickard, 1979). This indirec evidence for muscarinic receptor-mediated PIP2 breakdown has now been confirmed witt direct measurements of inositol phosphate production in isolated cervical ganglia (Horwit~ et al., 1985; Horwitz et al., 1986; Bone et al., 1984). In addition, during the course of the latter study, Bone et al. (1984) observed that vasopressin, via Vt receptors, also stimulate( a rapid formation of IP3 and that this stimulation was much greater than that produce( by the muscarinic agonist bethanecol. The endogenous molecule that activates these V receptors does not appear to be vasopressin itself, but instead an as yet uneharacterise( vasopressin-like peptide (Hanley et al., 1984).

Inositol phospholipid hydrolysisin the autonomicnervous system

403

In addition to acetylcholine and vasopressin, stimulation of phosphoinositide turnover has also been observed in ganglia in response to vasocactive intestinal polypeptide (Audiger et al., 1986; Durroux et al., 1987), nerve growth factor (Lakshamanan, 1978, 1979), bradykinin (Bone and Michell, 1985) and the tachykinins (Bone and Michell, 1985). These responses have thus far been poorly characterised. Depolarization of the ganglia induced by elevation of the extracellular K ÷ concentration (Bone and Michell, 1985) or by enhancing electrical activity (Briggs et al., 1985) also stimulated the formation of inositoi phosphates. Although part of this effect is due to release of endogenous acetylcholine, a portion of the response is insensitive to atropine and also to vasopressin antagonists (Bone and Michell, 1985). The mediator of this Ca2+-dependent response is unknown, but it could be related to the opening of voltage-sensitive Ca 2÷ channels since a similar effect in rat cerebral cortex (Kendall and Nahorski, 1985) was blocked by calcium channel antagonists. Currently the physiological significance of acetylcholine and vasopressin stimulated PIP2 breakdown in ganglia is not known. Muscarinic receptor activation in sympathetic nerves causes a slow excitatory post-synaptic potential (slow e.p.s.p.), a depolarising effect that enhances transmission through the ganglion (Brown, 1984). This effect is brought about through the inhibition of a hyperpolarising K ÷ current (the M-current) by closing a specific subset of voltage-sensitive K ÷ channels (Brown, 1984). Vasopressin acts in a similar manner (Bone and Michell, 1985) and, in addition, reduces the amplitude of the fast e.p.s.p, in superior cervical ganglia (Kiraly et al., 1986). Whether these effects are brought about through the formation of Ins 1,4,5-triP and diacylglycerol is not known. 4.2. NEUROTRANSMITTERRELEASEFROMNERVETERMINALS IN THE AUTONOMICNERVOUSSYSTEM The sequence of events which take place in the autonomic nerve terminal leading to the release of acetylcholine, noradrenaline, ATP and peptide neurotransmitters are thought to be as follows (Illes, 1986). The arrival of the action potential at the terminal leads to depolarisation of the varicosity with subsequent opening of dihydropyridine insensitive Ca 2+ channels. The enhanced influx of Ca 2+ is thought to trigger neurotransmitter release either as a direct consequence of the increase in cytoplasmic Ca 2+ or through the activation of Ca2+-calmodulin-dependent protein kinases. The inward Ca 2+ current decays in a voltage- and time-dependent manner, and the increased intracellular Ca 2+ concentration is returned to resting levels through the extrusion of Ca 2+ from the terminal or by Ca 2+ sequestration into intracellular organelles. The final steady Ca 2+ balance is re-established over a much longer time period by means of membrane Ca 2+ transporters, e.g. Na+-Ca 2+ exchange. Potentially, therefore, presynaptic receptors can modify transmitter release by altering the magnitude or the time course of the Ca 2+ signal, or through a resetting of the sensitivity of the Ca2+-regulated steps involved with release. A change in the pattern of the Ca 2+ signal can be brought about directly through the phosphorylation of Ca 2+ channels or the processes involved with the termination of the Ca 2+ signal, i.e. sequestration or extrusion from the cell, or indirectly through an alteration in the properties of other membrane ion channels and transporters. For example, an increase in the duration of the action potential, an increase in the probability of the action potential invading the varicosity, or a decrease in the outward K + current would all tend to lead to an increase in the opening time of the Ca 2+ channels. The activation of presynaptic receptors produces either inhibition (alpha 2-adrenergic, opiate, muscarinic, tachykinins, purines and prostaglandins) or facilitation (betaadrenergic) of electrically-induced neurotransmitter release (Illes, 1986). In addition, Kilbinger (1984) has identified a muscarinic receptor in myenteric neurones which stimulates the resting release of acetylcholine. Although the various presynaptic receptors have been well characterised in terms of their pharmacology, the second messenger events which take place following their activation have been poorly characterised, largely due to

404

S.P. WATSONand P. P. GODFREY

the difficulties involved in studying the biochemical events in the nerve terminal in isolation from similar events in the postsynaptic site. One approach to this problem is to study events in the cell body or in other tissues which contain the same sub-type of receptor and extrapolate the results to the nerve terminal. Of the identified presynaptic receptor sub-types, only tachykinin and muscarinic receptors have been shown to couple to inositol phospholipid metabolism, the other receptors being coupled to cAMP formation (betaadrenergic) or cAMP inhibition (alpha 2-adrenergic, opiate, purines). In addition, however, muscarinic receptors are also coupled to cAMP inhibition and it is believed that this event is mediated by the same sub-type of receptor (M 1 or M2) which induces inositol phospholipid hydrolysis, i.e. the same receptor sub-type can stimulate two distinct second messenger pathways (Brown and Brown, 1984). There is only a single report describing the existence of substance P receptors on nerve terminals within the autonomic nervous system (Kilbinger et al., 1986) and clearly this requires verification. We are left, therefore, with the unsatisfactory situation that, at present, there is no fully established sub-type ot presynaptic receptor which is known to couple only to inositol phospholipid metabolism from which to infer the effects of this pathway on transmitter release. The predominantly inhibiting presynaptic action of muscarinic receptors could be a consequence of a decrease in cAMP or an increase in inositol phospholipid metabolism. The consequence of activation of protein kinase C or an increase in the levels of In, 1,4,5-triP in the presynaptic terminal therefore, can only be inferred, at present, througt the use of appropriate pharmacological probes. Surprisingly, however, there are, to ouJ knowledge, only two reports describing the effect of phorbol esters on neurotransmitteJ release in autonomic nerves and no reports on the action of membrane-permeabk diacylglycerols. In guinea-pig sinus node (Shuntoh and Tanaka, 1986) and guinea-pi~ ileum (Tanaka et al., 1984), phorbol esters potentiate electrically evoked release o ' noradrenaline and acetylcholine respectively, but have no effect on the basal release o: either neurotransmitter. Similarly, phorbol esters potentiate Ca 2÷ ionophore-inducec noradrenaline release from the guinea-pig sinus node (Shuntoh and Tanaka, 1986). Simila~ results have been observed for the release of noradrenaline from hippocampal neurone~ (Allgaier et al., 1987) and for the release of acetylcholine at the neuromuscular junctior of the frog (Shapira et al., 1987) and mice (Murphy and Smith, 1987). In all cases th~ activation of protein kinase C facilitated electrically-induced release of neurotransmitter The molecular mechanism of this effect is not known although it may be useful to drav a parallel with the ability of protein kinase C to facilitate release in exocrine tissues (se~ Section 3.3) and to alter the activity of many membrane ion channels (see Kaczmarek 1987). Protein kinase C has also been shown to phosphorylate a partially purifie( preparation of tyrosine hydroxylase, the rate limiting enzyme in the synthesis of nora drenaline (Albert et al., 1984). It is not known whether this occurs in intact cells. No dat~ is available describing the action of Ins 1,4,5-triP in autonomic nerve terminals.

5. PATHOLOGY OF A L T E R E D INOSITIDE METABOLISM Although a direct link between abnormalities in inositide metabolism and clinica manifestations of disease is very difficult to prove, circumstantial evidence implicatin alterations in inositol and inositide turnover has been found in: (1) diabetic neuropathy; (2) the therapeutic action of Li ÷ in the treatment of manic-depressive psychoses; (3) the pathogenesis of oncogene related tumours. 5.1. PERIPHERAL DIABETIC NEUROPATHY

The development of peripheral neuropathy is one of the major complications of diabete and is thought to be related to metabolic abnormalities in nerve resulting from chroni insulin deficiency and/or hyperglycaemia.

Inositol phospholipid hydrolysis in the autonomic nervous system

405

The neuropathy, which is manifested as a decrease in nerve conductance, is accompanied by a reduction in nerve Na÷/K÷-ATPase (Greene and Lattimer, 1984), an increase in sorbitol concentration (Mayhew et al., 1983) and a reduction in myo-inositol levels, which has been observed in both human and animal diabetic nerves (Greene et al., 1975; Mayhew et al., 1983). With the observation in peripheral nerve from diabetic rabbits that protein kinase C activators normalise the reduced Na+/K÷-ATPase activity (Greene and Lattimer, 1986), a hypothesis linking the inositol deficiency to the reduced nerve conductance via alterations in phosphoinositide turnover was proposed (Greene et al., 1985). It was postulated that glucose, at hyperglycaemic concentrations, reduces nerve myoinositol by competitively inhibiting its uptake. Increased polyol (mostly sorbitol) pathway activity, also a consequence of hyperglycaemia, further contributes to reduced nerve myo-inositol. The decrease in nerve myo-inositol leads to a reduction in Na÷/K÷-ATPase activity, possibly via alterations in phosphoinositide turnover and abnormal levels of the second messengers IP 3 and diacylglycerol. The uptake ofmyo-inositol is sodium-dependent and so a reduction in Na+/K÷-ATPase activity reinforces the defect in myo-inositol uptake and thereby the abnormal metabolic cycle is maintained (Greene et al., 1985). There have been a few small-scale attempts to reverse the clinical symptoms of neuropathy by supplementing the diet with myo-inositol, with limited success. A large, carefully-controlled study is clearly required to establish whether this is a viable therapy. Also, much research needs to be done to establish whether the reduced myo-inositol levels and Na÷/K+-ATPase activity can be linked together through alterations in phosphoinositide metabolism. 5.2. THE USE OF LI + IN THERAPEUTICS One of the most intriguing aspects of inositide metabolism to have been uncovered recently is the selective inhibitory action of lithium ions on several of the enzyme activities that hydrolyse the inositol phosphates (Drummond, 1987). Li ÷ is used extensively to treat manic-depressive psychoses, yet its precise biochemical action is unclear. The link with inositide metabolism was first established by Sherman and co-workers who found that Li*, at therapeutically relevant concentrations (0.1-1.0 raM) inhibited the enzyme myo-inositol l-phosphate (Hallcher and Sherman, 1980). When given in vivo Li* caused a dramatic increase in brain myo-inositol 1-phosphate (Allison et al., 1976) and a decrease in myo-inositol levels (Allison and Stewart, 1971). It was proposed that Li* was exerting its therapeutic effect by reducing the brain myo-inositoi levels to such an extent that P! resynthesis was compromised, leading to an inhibition of agonist-stimulated phosphoinositide turnover. If an overactive inositidelinked receptor was producing the clinical symptoms of mania, these receptors would be selectively regulated by Li* (Sherman et al., 1981; Berridge et al., 1982). Evidence supporting this hypothesis is sparse, though it has been shown that Li ÷ inhibits the resynthesis of PI in vitro in cholinergically-stimulated parotid glands (Downes and Stone, 1986) and TRH-stimulated GH3 pituitary cells (Drummond and Raeburn, 1984). PIP2 synthesis in both cell types, however, was unaffected. Recently there have been two preliminary reports suggesting that in vivo treatment of rats with Li ÷ reduces cerebral phosphoinositide turnover in response to a variety of agonists when assayed in vitro (Godfrey et al., 1986; Kendall and Nahorski, 1986). Thus, despite an apparent lack of effect in steady-state levels of PIP2, Li + may be able to reduce the flux round the inositol phospholipid cycle following agonist stimulation. Li ÷ is remarkably selective to the brain in its therapeutic action. This may be related to the poor ability of inositol to cross the blood-brain barrier (Spector and Lorenzo, 1975). Thus, in Li*-treated rats a reduction in inositol levels is only seen in brain and not in the periphery (Allison and Stewart, 1971). However, this does not mean that Li + is without effect on peripheral tissues. Lithium's major side-effect is a toxic action on kidney function, which occurs at concentrations above 2 mM, only two- to three-fold higher than the therapeutic dose (Wood and Goodwin, 1987). It has also been shown in vitro that pretreatment

406

S.P. WATSONand P. P. GODFREY

with 2 mM LiC1 substantially attenuates the relaxation of tracheal smooth muscle following carbachol or histamine stimulation (Menkes et al., 1986a) with half maximal effects at 1 mM Li ÷. However, these authors did not investigate the cellular inositol levels and it would be interesting to see whether inositol levels equivalent to those in plasma (0.1 raM; Sherman et al., 1981) would reverse the actions of lithium in these cells. In the study ot Downes and Stone (1986) the inhibitory action of 10 mM LiC1 on PI synthesis in parotid cells could only be fully reversed by inositol concentrations above 10mM. However. 10mM LiC1 in vivo would be a fatal concentration and perhaps more physiologicalb relevant experiments should be done, using 0.5-1.0 mM LiCI, to complement their study At present we can, therefore, only say that lithium ions have inhibitory actions on certai~ aspects of inositol and phosphoinositide metabolism in both central and peripheral tissues The relationship of these changes to effects of Li + on physiological and pathological cellular responses though, are still very uncertain. 5.3. ONCOGENES AND THE INOSITOL PHOSPHOLIPID PATHWAY Cancerous growths are often caused by an overproduction of a normal cellular proteir involved with the growth cycle, or the expression of a mutant form of this protein whict is not subject to the normal feedback controls preventing excessive cell growth. In man~ of these instances the increased expression of this protein has been shown to have profound stimulatory effect on the inositol phospholipid pathway (Fleischman et al., 1986 Wakelan et al., 1986). The hypothesis has therefore been proposed that some oncogene: encode for proteins involved in the inositol phospholipid cycle (Berridge, 1987). In al cases, however, it is unclear whether the stimulatory effect on phosphoinositide metabolisn is directly related to the increased expression of the protein, or whether it is a genera consequence of the stimulation of the growth cycle. The answer to this question must awai the full characterisation of the role of these proteins in the cell. As discussed in Section 2.3, increased expression of r a s - p r o t e i n s , which are thought t~ be responsible for approx. 20% of intestinal carcinomas (Bos et al., 1987; Forrester et al. 1987), leads to a marked enhancement of agonist-induced hydrolysis of inositol phospho lipids (Wakelam et al., 1986). The suggestion has been put forward therefore that ra proteins may be involved in the coupling mechanism linking the activated state of th, receptor to phospholipase C (Wakelam et al., 1986). Similarly, an increase in the levels o the polyphosphoinositides has been shown to precede the onset of growth in a number o tumour-derived cell lines (Shavoni et al., 1986). This effect is thought to be brought abou through the stimulation of PI-kinase and PIP-kinase and is correlated with an increase i~ the levels of various tyrosine kinases in the cell, e.g. src and ros (Shavoni et al., 198f Sugimoto et al., 1984; Whitman et al., 1985; Berridge, 1987). This effect does not appea to result from a direct phosphorylation of the lipids by these kinases as originally though (Sugimoto et al., 1984), but appears to be related to phosphorylation of an, as yel uncharacterised intermediate protein (Berridge, 1987). For a more detailed discussion of this topic see Berridge (1987).

6. FUTURE DEVELOPMENTS AND THERAPEUTIC IMPLICATIONS During the 1980s there has been a dramatic increase in our understanding of th inositol phospholipid pathway and its role in cellular activation. The hydrolysis of relatively minor membrane lipid, PIP2, has been shown to generate two second messenger: Ins 1,4,5-triP, which mobilises intracellular Ca 2÷, and diacylglycerol, which activate protein kinase C. There still remain, however, many unanswered questions relating to th role of this pathway in transmembrane signalling, including: (1) The mechanism whereby phosphoinositide-linked receptors stimulate Ca 2+ entry i non-excitable cells, e.g. exocrine tissues (see Section 2.5 for a discussion of currer theories).

Inositol phospholipid hydrolysisin the autonomic nervous system

407

(2) The events which lead to the onset of depolarisation in many excitable cells, e.g. guinea-pig ileum by phosphoinositide-linked receptors. (3) The relationship between inositol phospholipid hydrolysis, which occurs within seconds, and the onset of normal or cancerous cellular division, which takes place after a lag of many hours. It has been hypothesised that certain oncogenes may encode for proteins which play a fundamental role in receptor-stimulated hydrolysis of inositol phospholipids. (4) The nature of the G-protein or G-proteins which link the activated state of the receptor to phospholipase C. The sensitivity of some but not all receptor-evoked increases in inositol phospholipid to pertussis toxin (see Section 2.3) suggests that there is more than one type of G-protein linking the receptor to phospholipase C. The exciting possibility is that there may be a complete family of G-proteins which subserve this role and that each G-protein only interacts with a limited number of receptors. (5) It is unclear whether phosphoinositide-linked receptors also stimulate other second messenger pathways. For example, it is thought that a single sub-type of cardiac muscarinic receptor is able to stimulate inositol phospholipid hydrolysis, to decrease cellular levels of cAMP and to open a particular class of K ÷ channels (Brown and Brown, 1984; Birnbaumer, 1987). It is thought that these effects are mediated through the activation of three distinct G-proteins. If this is the case, then the role of the G-protein in cell activation should not simply be seen as relaying information from the receptor to the effector pathway, but more as a level of integration whereby the message received from the activation of a particular receptor is dependent on the availability and the type of G-proteins in the membrane. An important feature of the phosphoinositide pathway is its potential versatility. Protein kinase C and Ca :+ have been shown to interact in an additive, independent, synergistic or negative feedback manner depending on the tissue under study. Moreover, there are many enzymes involved in the synthesis of the polyphosphoinositides and in the degradation of the inositol phosphates and diacylglycerol which could be suitable targets for negative or positive feedback processes. A change in the activity of any one of these enzymes could induce a marked change in the relative amounts of the second messengers, Ins i,4,5-triP, diacylglycerol and Ins 1,3,4,5-tetraP, and thus change the emphasis of the signal across the membrane. For example, it is controversial whether there is a switch from the hydrolysis of PIP2, thus generating Ins 1,4,5-triP and diacylglycerol, to the hydrolysis of PI, thus generating only diacylglycerol (see Section 2.2). Similarly, in many cells the activity of Ins 1,4,5-triP-kinase is increased following the elevation of the intracellular Ca 2÷ levels to approx. 1 pM (see Section 2.2). If Ins 1,3,4,5-tetraP is involved in the entrance of intracellular Ca 2÷, as suggested by the work of Irvine and Moor (1986), then this mechanism would enable a shift in the mobilisation of Ca 2÷ from intracellular to extracellular sources. The importance of these potential control mechanisms is likely to vary from one tissue to next depending on the role of the various intracellular messengers in the tissue. Thus it can be seen that many different combinations of these second messengers can be obtained through the hydrolysis of a family of membrane inositol phospholipids. The high degree of versatility in this system should be viewed as highly encouraging from the viewpoint of potential targets for therapeutic intervention. Novel agents which selectively inhibit an enzyme involved in this cycle could have profound effects in some cells but very little action in others, depending on the role of that enzyme in the cell. It is perhaps useful therefore to close this review with just a few examples of potential targets for therapeutic intervention at the level of this pathway: (i) Agents (antagonists) which prevent the interaction of Ins 1,4,5-triP with its receptors on the endoplasmic reticulum may represent a novel class of anti-hypertensives. For many blood vessels the source of Ca 2÷ utilised for contraction is predominantly intracellular and this would help to accentuate the selectivity of such agents.

408

S.P. WATSONand P. P. GODFREY

(ii) If, as hypothesised, an increase in the levels of the polyphosphoinositides is essential for the onset of cell growth, then inhibitors of PI- or PIP-kinase may represent novel anti-cancer agents. (iii) Inhibitors of diacylglycerol-kinase would be expected to potentiate the action of protein kinase C in cells which utilise this pathway of diacylglycerol-metabolism. This may be of therapeutic use in the treatment of diabetes by potentiating glucose-induced secretion of insulin. Acknowledgements--We would like to thank the members of the Departments of Pharmacology and Clinical Pharmacology for many useful discussions during the preparation of this manuscript, with particular thanks tc Dr A. Brading for help with the section on smooth muscle. PPG acknowledges support from The Wellcome Trust

REFERENCES ABDEL-LATIF, A. A., AKHTAR, R. A. and HAWTHORNE, J. N. (1977) Acetylcholine increases the breakdown oJ triphosphoinositide of rabbit iris muscle prelabelled with [32p]phosphate. Biochem. J. 162: 61-73. ADELSTEIN, R. S. and EISENBERG,E. (1980) Regulation and kinetics of the actin-myasin-ATP interaction. Ann Rev. Biochem. 49: 921-956. A1YER, N., NAMBI,P., WHITMAN, M., STASASEN,F. L. and CROOKE, S. T. (1987) Phorbol ester-mediated inhibitiol of vasopressin and fl-adrenergic responses in a vascular smooth muscle cell line. Mol. Pharmacol. 31 180-184. AKHTAR, R. A. and ABDEL-LATIF,A. A. (1986) Surgical sympathetic denervation increases alpha-adrenoceptor mediated accumulation of myo-inositol trisphosphate and muscle contraction in rabbit iris dilator smootl muscle. J. Neurochem. 46: 96-104. ALBERT, K. A., HELMER-MATYJEK,E., NAIRN, A. C,, MULLER, T. H., HAYCOCK,J., GREENE, L. A., GOLDSTEIN,M and GREENGARD, P. (1984) Calcium/phospholipid-dependent protein kinase (protein kinase C) phos phorylates and activates tyrosine hydroxylates. Proc. Natl. Acad. Sci. 81: 7713-7717. ALLGA1ER, C., HERTTING, G., Hug YU, HUANG and JACKISCH, R. (1987) Protein kinase C activation an. alpha2-autoreceptor modulated release of noradrenaline. Br. J. Pharmac. 92: 161-172. ALLISON, J. H. and STEWART,M. A. (1971) Reduced brain inositol in lithium-treated rats. Nature (London) 232 267 268. ALLISON, J. H., BLISSNER, M. W., HOLLAND, W. H., HIPPS, P. P. and SHERMAN,W. R. (1976) Increased brai myo-inositol l-phosphate in lithium-treated rats. Biochem. Biophys. Res. Commun. 76: 664-670. ASHENDEL, C. L. (1985) The phorbol ester receptor: a phospholipid-regulated protein kinase. Biochim. Biophy: Acta 822: 219-242. AUB, D. L. and PUTNEY,J. W. JR (1984) Metabolism of inositol phosphates in parotid cells: Implications for th pathways of the phosphoinositide effect and for the possible messenger role of inositol trisphospbate. Li) Sci. 34: 1347-1355. AUB, D. L. and PUTNEY, J. W. JR (1985) Properties of receptor-controlled inositol trisphosphate formation i parotid acinar cells. J. Biochem. 225: 263-266. AuB, D. L., McKINNEY, J. S. and PUTNEY, J. W. JR (1982) Nature of the receptor-regulated calcium pool in t~ rat parotid gland. J. Physiol. (Lond.) 331: 557-565. AUD1GER, S., BARBERIS,C. and JARD, S. (1986) Vasoactive intestinal polypeptide increases inositol phospholipi breakdown in the rat superior cervical ganglion. Brain Res. 376:363 367. BARABAN, J. M., GOULD, R. J., PEROUTKA, S. J. and SNYDER, S. H. (1985) Phorbol ester effects on neurt transmission: interaction with neurotransmitters and calcium in smooth muscle. ,°roe. Natl. Aead. Sei. 8. 604 607, BATTY, I. R., NAHORSKI, S. R. and IRV1NE, R. F. (1985) Rapid formation of inositol 1,3,4,5-tetrakisphospha following muscarinic receptor stimulation of rat cerebral cortical slices. Bioehem. J. 232:211-215. BAUKAL, A. J., GUILLEMETTE, G., RUBIN, R., SPAT, A. and KATT, K. J. (1985) Binding sites for inosit, trisphosphate in the bovine adrenal cortex. Biochem. Biophys. Res. Commun. 133: 532-538. BELL, R. L., KENNERLY, D. A., STANFORD, N. and MAJERUS, P. W. (1979) Diglyceride lipase: a pathway fi arachidonate release from human platelets. Proc. Natl. Acad. Sci. 76: 3238-3241. BENHAM, C. D. and BOLTON,T. B. (1986) Spontaneous transient outward currents in single visceral and vascuL smooth muscle cells of the rabbiL J. Physiol. 381: 385~,06. BENHAM, C. D. and TSIEN, R. W. (1987) A novel receptor-operated Ca2+-permeable channel activated by A'I in smooth muscle. Nature 328: 275-278. BERK, B. C., ARONOW, M. S., BROCK, T. A., CRAGOE, E. JR, GIMBRONE,M. A. JR and ALEXANDER,R. W. (198 Angiotensin ll-stimulated Na+/H + exchange in cultured vascular smooth muscle cells: evidence for prote kinase C-dependent and independent pathways. J. Biol. Chem. 262: 5057-5064. BERRIDGE, M. J. (1983) Rapid accumulation of inositol trisphosphate reveals that agonists hydrolyse pol phosphoinositides instead of phosphatidylinositol. Bioehem. J. 212: 849-858. BERRIDGE, M. J. (1984) lnositol trisphosphate and diacylglycerol as second messengers. Biochem. J. 21 849-858. BERRIDGE, M. J. (1987) Inositol lipids and cell proliferation. Biochem. Biophys. Acta 907: 33~15. BERRIDGE, M. J. and IRVINE, R. F. (1984) Inositol trisphosphate, a novel second messenger in cellular sigr transduction. Nature 312:315-321. BERRIDGE, M. J., DOWNES, C. P. and HANLEY, M. R. (1982) Lithium amplifies agonist-dependent phosphatidl inositol responses in brain and salivary glands. Biochem. d 206: 587-595.

Inositol phospholipid hydrolysis in the autonomic nervous system

409

BERRIDGE, M. J., DAWSON, R. M. C., DOWNES, C. P., HESLOP, J. P. and IRVINE, R. F. (1983) Changes in the levels of inositol phosphates after agonist-dependent hydrolysis of membrane phosphoinositides. Bioehem. J. 212: 473-482. BHULLAR, R. P. and HASLAM, R. J. (1987) Detection of 23-27 kDa GTP-binding proteins in platelets and other cells. Biochem. J. 245: 617~520. BIDEN, T. J. and WOLLHEIM,C. B. (1986) Ca 2÷ regulates the inositol tris/tetrakisphosphate pathway in intact and broken preparations of insulin-secreting RINm5F cells. J. Biol. Chem. 261:11931-11934. BIELKIEWICZ-VOLLRATH,B., CARPENTER,J. R., SCHULZ, R. and COOK, D. A. (1987) Early production of 1,4,5-inositol trisphosphate and 1,3,4-inositol tetrakisphosphate by histamine and carbachol in ileal smooth muscle. Mo/ec. pharmacol. 31:513 522. BILLAH, M. M., LAPETINA, E. G. and CUATRECASAS,P. (1980) Phospholipase A2 and phospholipase C activities in platelets: Differential substrate specificity, Ca 2+ requirement, pH dependence, and cellular localization. J. Biol. Chem. 255:10227 10231. BIRNaAUMER, L. (1987) Which G proteins are the active mediators in signal transduction. Trends Pharmacology Sci. 8: 209-211. BOLTON,T. B. (1979) Mechanisms of action of transmitters and other substances on smooth muscle. Physiol. Rev. 59:606 718. BONE, E. A. and MICHELL, R. H. (1985) Accumulation of inositol phosphates in sympathetic ganglia. Effect of depolarization and of amine and peptide neurotransmitters. Biochem. J. 227: 263-269. BONE, E. A., FRETTEN, P., PALMER, S., KIRK, C. J. and MICHELL, R, H. (1984) Rapid accumulation of inositol phosphates in isolated rat superior cervical sympathetic ganglia exposed to V~, vasopressin and muscarinic cholinergic stimuli. Biochem. J. 221: 803-811. Bos, J. L., FEARON, E. R., HAMILTON,S. R., VERLAAN-DE-VRIES,M., VANDEREB, A. J. and VOGELSTEIN,B. (1987) Prevalence of ras gene mutations in human colon-rectal cancers. Nature 327: 293-297. BRADFORD, P. G. and RUBIN, R. P. (1986) Guanine nucleotide regulation of phospholipase C activity in permeabilised rabbit neutrophils. Inhibition by pertussis toxin and sensitization to sub micromolar calcium concentrations. Biochem. J. 239: 97-102. BRADING, A. F. and SNEDDON,P. (1980) Evidence for multiple sources of calcium for activation of the contractile mechanism of guinea-pig taeni coli on stimulation with carbachol. BE. J. Pharmac. 70: 229-240, BRANDT, S. J., DOUGHERTY, R. W., LAPETINA, E. G. and NIEDEL, J. E. (1985) Pertussis toxin inhibits chemotactic peptide-stimulated generation of inositol phosphates and lysosomal enzyme secretion in human leukemic (HL-60) cells. Proc. Natl. Acad. Sci. 82: 3277-3280. BRIGGS, C. A., HORWITZ, J., MCALFEE, D. A,, TSYMBALOR,S. and PERLMAN, R. L. 0985) Effects of neuronal activity on inositol phospholipid metabolism in the rat autonomic nervous system. J. Neurochem. 44: 731 739. BRISTOW, D. R., CURTIS, N. R., SUMAN-CHAUHAN, N., WATLING,K. J. and WILLIAMS,n. J. (1986) Effects of tachykinins on inositol phospholipid hydrolysis in slices of hamster urinary bladder. Br. J. Pharmac. 90: 211-217. BROWN, D. A. (1984) Slow cholinergic excitation--a mechanism for increasing neuronal excitability. Trends Neurosci. 6: 302-307. BROWN, J. H. and BROWN, S. L. (1984) Agonists differentiate muscarinic receptors that inhibit cyclic AMP formation from those that stimulate phosphoinositide metabolism. J. Biol. Chem. 259: 3777-3781. BRUCKNER, R., MUGGE, A. and SCHOLZ,H. (1985) Existence and functional role of alphal-adrenoceptors in the mammalian heart. J. Mol. Cell. Cardiol. 17: 639-645S. BURGESS, G. M., GODFREY, P. P., McKINNEV, J. S., BERRIDGE,M. J., IRVINE, R. F. and PUTNEY, J. W. JR (1984) The second messenger linking receptor activation to internal Ca release in liver. Nature 309: 63-66. BURGESS, G. M., McKINNEV, J. S., IRVINE, R. F. and PUTNEV,J. W. JR (1985) Inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate formation in Ca2+-mobilising-hormone-activated cells. Biochem. J. 232: 237-243. BURNHAM, D. B., MUNOWITZ, P., HOOTMAN, S. R. and WILLIAMS, J. A. (1986) Regulation of protein phosphorylation in pancreatic acini. Distinct effects of Ca `'+ ionophore A23187 and 12-o-tetradecanoylphorbol13-acetate. Biochem. J. 235: 125-131. BUTCHER, F. R. and PUTNEY,J. W. (1980) Regulation of parotid gland function by cyclic nucleotides and calcium. Advances in Cyclic Nucleotide Res. 13: 215-249. CARSTEN, M. E. and MILLER, J. D. (1985) Ca 2+ release by inositol trisphosphate from Ca2+-transporting microsomes derived from uterine sarcoplasmic reticulum. Biochem. Biophys. Res. Commun. 130: 1027-1031. CHATTERJEE, M. and TEJEDA, M. (1986) Phorbol-ester-induced contraction in chemically skinned vascular smooth muscle. Ann. J. Physiol. 251: 356-361. Cmu, A. T., BOZARTH,J. M. and TIMMERMANS,P. B. M. W. M. (1987) Relationship between phosphatidylinositol turnover and Ca 2+ mobilisation induced by alpha-1 adrenoceptor stimulation in the rat aorta. J. Pharmacol. Exp. TheE. 240: 123-130. COCKCROET. S. (1987) Polyphosphoinositide phosphodiesterase: regulation by a novel guanine nucleotide binding protein, Gp. Trends Biochem. Sci. 12: 75-78. COCKCROFT, S. and GOMPERTS, B. D. (1985) Role of guanine nucleotide binding protein in the activation of polyphosphoinositide phosphodiesterase. Nature 314: 534-536. COCKCROFT, S., TAYLOR,J. A. and JUDAH,J. D. (I 985) Subcellular localisation of inositol lipid kinases in rat liver. Biochim. Biophys. Acta 845: 163-170. COLLINS, S. A., PON, D. J. and SEN, A. K. (1987) Phosphorylation of the alpha-subunit of Na+-K+-ATPase by carbachol in tissue slices and the role of phosphoproteins in stimulus-secretion coupling. Biochem. Biophys. Acta. 927: 392-401. COTECCHIA,S., LEEB-LUNDBERG,L., HAGEN,P.-O., LEFKOWITZ,R. J. and CARON,M. G. (1985) Phorbol ester effects on alphal-adrenoceptor binding and phosphatidylinositol metabolism in cultured vascular smooth and muscle cells. Life Sei. 37: 2389-2398.

410

S. P. WATSONand P. P. GODFREY

COUSSENS, L., PARKER, P. J., RHEE, L., YANG-FENG, T. L., CHEN, E., WATERFIELD, M. D., FRANCKE, U. and ULLRICH,A. (1986) Multiple, distinct forms of bovine and human protein kinase C suggests diversity in cellular signalling pathways. Science 233: 859-866. DANTHULURI, N. R. and DETH, R. C, (1986) Acute desensitisation to angiotensin II: evidence for a requiremenl of agonist-induced diacylglycerol production during tonic contraction of rat aorta. Eur. J. Pharmacol. 126 135 139. DAWSON, A. P., COMERFORD, J. G. and FULTON, D. V. (1986) The effect of GTP on inositol 1,4,5-trisphosphate stimulated Ca -'+ efflux from a rat liver microsomal fraction, ls a GTP-dependent protein phosphorylatioI involved. Biochem. J. 234: 311-315. DONALDSON, J. and HILL, S. J. (1985) Histamine-induced inositol phospholipid breakdown in the longitudina smooth muscle of guinea-pig ileum. Br. J. Pharmac. 85: 499-512. DOUGHERTY, R. W., GODFREY,P. P., HOYLE, P. C., PUTNEY,J. W. JR and FREER, R. J. (1984) Secretagogue-induce~ phosphoinositide metabolism in human leucocytes. Biochem. J. 222: 307-314. DOUGHNEY, C., DORMER, R. L. and MCPHERSON, M. A. (1987) Adrenergic regulation of formation of inosito phosphates in rat submandibular acini. Biochem. J. 241: 705-709. DOWNES, C. P. and MICHELL, R. H. (1982) Phosphatidynositol 4-bisphosphate and phosphatidylinositol 4,5-bis phosphate: Lipids in search of a function. Cell Calcium 3: 467-502; 6: 313-316. DOWNES, C. P. and MICHELL, R. H. (1985) Inositol phospholipid breakdown as a receptor controlled generato of second messengers. Molecular Mechanisms in Cellular Regulation. Molecular Aspects of Transmernbran Signalling 4: 3-56. DOWNES, C. P. and STONE,M. A. (1986) Lithium-induced reduction in intracellular inositol supply in cholinel gically stimulated parotid gland. Biochem. J. 234:199 204. DOWNES, C. P. and WUSTEMAN,M. M. (1983) Breakdown of polyphosphoinositides and not phosphatidylinositc accounts for muscarinic agonist stimulated inositol phospholipid metabolism in rat parotid glands. Biochen J. 216: 633-690. DOWNES, C. P., MUSSAT,M. C. and MICnELL, R. H. (1982) The inositol trisphosphate phosphomonoesterase the human erythrocyte membrane. Biochem. d. 203:169 177. DOWNES, C. P., HAWKINS,P. T. and IRVINE,R. F. (1986) Inositol 1,3,4,5-tetrakisphosphate and not phosphatidyl nositol-3,4-bisphosphate is the probable precursor of inositol 1,3,4-trisphosphate in agonist-stimulate parotid gland. Biochem. J. 238:501 506. DOYLE, V. M., CREBA,J. A., RUEGG, U. T. and HOYER, D. (1986) Serotonin increases the production of inosit~ phosphates and mobilises calcium via the 5-HT2 receptor in A7r5 smooth muscle cells. Naunyn-Schmied~ berg's Arch. Pharmacol. 333:98 103. DguiiOND, A.H.(1987)Lithiumandinositollipid-linkedsignallingmechanisms. TrendsPharmac. Sci.8:129 13 DRUMMOND, A. H. and RAEBURN,C. A. (1984) The interaction of lithium with thyrotropin releasing hormon stimulated lipid metabolism in GH3 pituitary tumor cells. Biochem. J. 224: 129-136. DUNLOP, M. E. and LARKINS,R. G. (1986) Muscarinic-agonist and guanine nucleotide activation of polyphosphq inositide phosphodisterase in isolated islet-cell membranes. Biochem. J. 240: 731-737. DURROUX,T., BARBERIS,C. and JARD,S. (1987) Vasoactive intestinal polypeptide and carbachol act synergistical to induce the hydrolysis of inositol containing phospholipids in the rat superior cervical ganglion. Neuros~ Lett. 75:211 215. EVANS, T., BROWN, M. L., FRASER, E. D. and NORTHUP, J. K. (1986) Purifications of the major GTP-bindit proteins from human placental membranes, d. Biol. Chem. 261: 7052-7059. FABIATO, A. (1986) Inositol (l,4,5)-trisphosphate-induced release of Ca 2+ from the sarcoplasmic reticulum skinned cardiac cells. Biophys. J. 49: 190a. FISHER, S. K. and AGRANOFF, B. W. (1987) Receptor activation and inositol lipid hydrolysis in neural tissu~ J. Neurochern. 48: 999-1017. FLEISCHMAN, L. F., CHAHWALA, S. B. and CANTLEY, L. (1986) Ras-transformed cells: altered levels of phc phatidylinositol 4,5-bisphosphate and metabolites. Science 231: 407-410. FLINT, A. P. F., LEAT, W. M. F., SHELDRICK, E. L. and STEWART,H. J. (1986) Stimulation of phosphoinositi hydrolysis by oxytocin and the mechanism by which oxytocin controls prostaglandin synthesis in the ovi endometrium. Biochem. J. 237: 797-805. FOLCH, J. (1942) Brain cephalin, a mixture of phosphatidylserine, phosphatidylethanolamine and a fracti, containing an inositol phosphatide. J. Biol. Chem. 146: 35-44. FORDER,J., SCRIABINE,A. and RASMUSSEN,H. (1985) Plasma membrane calcium flux, protein kinase C activati and smooth muscle contraction. J. Pharmacol. Exp. Ther. 235: 267-273. FORRESTER, K., ALMAGUERA,K. HAN, GRIZZLE, W. E. and PERUCHO, M. (1987) Detection of high incidence K-ras oncogenes during human colon tumorgenesis. 327: 298-303. Fox, A. W. and FRIEDMAN,P. A. (1987) Evidence for spare alphal-adrenoceptors for the accumulation of inosi phosphates in smooth muscle. J. Pharm. Pharmacol. 39: 68-71. GILMAN, A. G. (1984) G. proteins and dual control of adenylate cyclase. Cell 36: 577-579. GLEASON, M. M. and FLAIM, S. F. (1986) Phorbol ester contracts rabbit thoracic aorta by increasing intracellu calcium and by activating calcium flux. Biochem. Biophys. Res. Commun. 138: 1362-1369. GODFREY, P. P., GRAHAME-SM1TH,D. G., McCLUE, S. J. and YOUNG, M. M. (1986) Chronic lithium treatm~ inhibits 5-hydroxytryptamine and carbachol stimulated phosphoinositide metabolism in rat brain slic Br. J. Pharmac. 87: l l7P. GODFREY, P. P. and PUTNEY, J. W. JR (1984) Receptor-mediated metabolism of the phosphoinositides a phosphatidic acid in rat lacrimal acinar cells. Biochem. J. 218: 187-195. GOMPERTS, B. D. (1983) Involvement of guanine-nucleotide binding protein in the gating of Ca 2+ by receptc Nature 306:67 69. GRANDARDY, B. M., Cuss, F. M., SAMPSON,A. S,, PALMER, J. B, and BARNES,P. J. (1986) Phosphatidylinosi response to cholinergic agonists in airway smooth muscle: relationship to contraction and muscari receptor occupancy. J. Pharmacol, Exp. Ther. 238: 273-279.

Inositol phospholipid hydrolysis in the autonomic nervous system

411

GREENE,D. A. and LATTIMER,S. A. (1984) Impaired energy utilisation and Na +-K +-ATPase in diabetic peripheral nerve. Am. J. Physiol. 246: EDII-EDI8. GREENE, D. A. and LATTIMER, S. A. (1986) Protein kinase C agonists acutely normalise decreased ouabaininhibitable respiration in diabetic rabbit nerve. Implications for Na+-K+-ATPase regulation and diabetic complications. Diabetes 35: 242-245. GREENE, D. A., DE JESUS,P. V. and WINEGRAD,A. I. (1975) Effects of insulin and dietary myo-inositol on impaired peripheral motor nerve conduction velocity in acute streptozotocin diabetes. J. Clin. Invest. 55: 1326-1336. GREENE, D. A., LATTIMER, S. A., ULaRECHT, J. and CARROLL, P. (1985) Glucose-induced alterations in nerve metabolism: current perspective on the pathogenesis of diabetic neuropathy, and future directions for research and therapy. Diabetes Care 8: 290-299. GUARD, S., WATLING, K. J. and WATSON, S. P. (1988) Neurokinin-3 receptors are linked to inositol phospholipid hydrolysis in the guinea-pig ileum. Br. J. Pharmacol. 94: 148-154. HALENDA, S. P. and RUalN, R. P. (1982) Phospholipid turnover in isolated rat pancreatic acini: consideration of the relative roles of phospholipase A2 and phospholipase C. Biochem. J. 208: 713-721. HALLCHER, L. M. and SHERMAN,W. R. (1980) The effects of lithium ion and other agents on the activity of myo-inositol-l-phosphatase from bovine brain. J. Biol. Chem. 223: 10890-10901. HANLEY, M. R.. BENTON, H., PLIGHTMAN, S. L., TODD, K., BONE, G. A., PALMER, S., KIRK, C. J. and MICHELL, R. H. (1984) A vasopressin-like peptide in the mammalian sympathetic nervous system. Nature 309: 258-261. HANSEN, C. A., MAH, S. and WlLLIAMSON,J. R. (1986) Formation and metabolism of inositol 1,3,4,5-tetrakisphosphate in liver. J. Biol. Chem. 261: 8100--8103. HASmMOTO, T., HIRATA, M. and ITO, Y. (1985) A role for inositol 1,4,5-trisphosphate in the initiation of agonist-induced contractions of dog tracheal smooth muscle. Br. J. Pharmacol. 86: 191-199. HASHIMOTO, T., HIRATA, M., ITOH, T., KANMURA, Y. and KURIYAMA, H. (1986) Inositol 1,4,5-trisphosphate activates pharmacomechanical coupling in smooth muscle of the rabbit mesenteric artery. J. Physiol. 370: 605-6 18. HASLAM, R. J. and DAVIDSON, M. M. L. (1984a) A receptor-induced diacylglycerol formation in permeabilised platelets: possible role for a GTP-binding protein. J. Rec. Res. 4: 605-629. HASLAM, R. J. and DAVIDSON, M. M. L. (1984b) Guanine nucleotides decrease the free [Ca 2+] required for secretion of serotonin from permeabilised blood platelets. Evidence of a role for a GTP-binding protein in platelet activation. Febs. Lett. 174: 90-95. HAWKINS, P. T., STEPHENS, L. and DOWNES, C. P. (1986) Rapid formation of inositol 1,3,4,5-tetrakis(P) and inositol 1,3,4-tris(P) in rat parotid glands may both result indirectly from receptor-stimulated release of inositol 1,4,5-tri(P) from phosphatidylinositol 4,5-bis(P). Biochem. J. 238: 507-516. HAWKINS, P. T., BERRIE,C. P., MORRIS, A. J. and DOWNES,C. P. (1987) Inositol 1,2-cyclic-4,5-trisphosphate is not a product of muscarinic receptor-stimulated phosphatidylinositol 4,5-bisphosphate hydrolysis in rat parotid glands. Biochem. J. 243: 211-218. HAWTHORNE, J. N. and PICKARD, M. R. (1979) Phospholipids in synaptic function. J. Neurochem. 32: 5-14. HESLOP, J. P., IRVINE, R. F., TASHJ1AN, A. H. JR and BERRIDGE, M. J. (1985) Inositol tetrakis- and pentakisphosphates in GH4 cells. J. Exp. Biol. ll9: 395-401. HIDAKA, H. and HAGIWARA,M. (1987) Pharmacology of the isoquinoline sulfonamide protein kinase C inhibitors. Trends Pharmacol. Sci. 8: 162-163. HIDAKA, H., TANAKA, T. and ITOH, H. (1984) Selective inhibitors of three forms of cyclic nucleotide phosphodiesterases. Trends Pharmacology Sci. 5:237 239. HOEEMAN, S. L. and MAJERUS, P. W. (1982) Identification and properties of two distinct phosphatidylinositol specific phospholipase C enzymes from sheep seminal vesicular glands. J. Biol. Chem. 257: 6461-6469. HOKIN, L. E. (1985) Receptors and phosphoinositide generated second messengers. Biochem. 54: 205-235. HOKIN, L. E. and HOK1N, M. R. (1955) Effects of acetylcholine on the turnover of phosphonyl units in individual phospholipids of pancreas slices and brain cortex slices. Biochem, Biophys. Aeta 18:102-110. HOKIN-NEAVERSON, M. R. (1977) Metabolism and role of phosphatidylinositol in acetylcholine-stimulated membrane function. Adv. Exp. Med. Biol. 83: 429-446. HOLMES, R. P. and Yoss, N. L. (1983) Failure of phosphatidic acid to translocate Ca 2+ across phosphatidylcholine membranes. Nature 305: 637-638. HOOTMAN, S. R., BROWN, M. E. and WILLIAMS,J. A. (1987) Phorbol esters and A23187 regulate Na+-K+-pump activity in pancreatic acinar cells. Am. J. Physiol. 252: G499-GS05. HORWITZ, J., TSYMBALOV,S. and PERLMAN,R. L. (1985) Muscarine stimulates the hydrolysis of inositol-containing phospholipids in the superior cervical ganglion. J. Pharmacol. Exp. Ther. 233: 235-241. HORWITZ, J., ANDERSON,C. H. and PERLMAN,R. L. (1986) Comparison of the effects of muscarine and vasopressin on inositol phospholipid metabolism in the superior cervical ganglion of the rat. J, Pharmacol. Exp. Ther. 237: 312-317. HowE, P. H. and ABDEL-LATIF,A. A. (1987) Phorbol-ester induced protein phosphorylations and contraction in sphincter smooth muscle of rabbit iris. FEBS Lett. 215: 279-284. HowE, P. H., AKHTAR, R. A., NADERI, S. and ABDEL-LATIE,A. A. (1986) Correlative studies on the effect of carbachol on myo-inositol trisphosphate accumulation, myosin light chain phosphorylation and contraction in smooth muscle of rabbit iris. J. Pharmacol. Exp. Ther. 239: 574-583. HUCHO, F., KRUGER, H., PRIBILLA,I. and OBERD1ECK,U. (1987) A 40 kDa inhibitor and protein kinase C purified from bovine brain. FEBS Lett. 211: 207-210. HURWITZ, C. (1975) Characterization of calcium pools utilized for contraction in smooth muscle, lnserm. 50: 369-380. hNo, M. (1987) Calcium dependent inositol trisphosphate-induced calcium release in the guinea-pig taeni caeci. Biochem. Biophys. Res. Commun. 142: 47-52. ILLES, P. (1986) Mechanisms of receptor-mediated modulation of transmitter release in noradrenergic cholinergic and sensory neurones. Neuroscience 17: 909-928. JpT. 383--J

412

S. P. WATSONand P. P. GODFREY

IMAI, A. and GERSHENGORN, M. C. (1986) Phosphatidylinositol-4,5-bisphosphate turnover is transient while phosphatidylinisotol turnover is persistent in thyrotropin-releasing hormone stimulated rat pituitary. Proe. Natl. Acad. Sci. 83: 8540-8544. 1RVINE, R. F. (1982) The enzymology of stimulated inositol lipid turnover. Cell Calcium 3: 295-309. IRVINE, R. F. and MOOR, R. M. (1986) Micro-injection of inositol 1,3,4,5-tetrakisphosphate activates sea urchin eggs by a mechanism dependent on external Ca 2+. Biochem. J. 240: 917-920. IRVINE, R. F., ANGGARD, E. E., LETCHER, A. J. and DOWNES, C. P. (1985) Metabolism of inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate in rat parotid glands. Biochem. J. 229: 505-511. IRVINE, R. F., LETCHER, A. J. and DAWSON,R. M. C. (1984a) Phosphatidylinositol-4,5-bisphosphate phosphodiesterase and phosphomonoesterase activities of rat brain. Some properties and possible control mechanisms. Biochem. J. 218: 177-185. IRVINE, R. F., LETCHER, A. J., HESLOP, J. P. and BERRIDGE, M. J. (1986a) The inositol tris/tetrakisphosphate pathway-demonstration of ins (1,4,5)P3 3-kinase activity in animal tissues. Nature 320: 631~34. IRVINE, R. F., LETCHER, A. J., LANDER, D. J. and BERRIDGE, M. J. (1986b) Specificity of inositol phosphatestimulated Ca 2+ mobilization from Swiss-mouse 3T3 cells. Biochem. J. 240: 301-304. IRVINE, R. F., LETCHER, A. J., LANDER, D. J. and DOWNES, C. P. (1984b) Inositol trisphosphates in carbacholstimulated rat parotid glands. Biochem. J. 223: 237-243. IsHIl, H., CONNOLLY,T. M., BROSS, T. E. and MAJERUS, P. W. (1986) Inositol cyclic trisphosphate (inosito] 1,2-(cyclic)-4,5-trisphosphate) is formed upon thrombin stimulation of human platelets. Proc. Natl. Acad Sci. 83: 639745401. ITO, Y., KITAMURA, K. and KURIYAMA,M. (1979) Effects of acetylcholine and catecholamines on the smootl: muscle cell of the porcine coronary artery. J. Physiol. (Lond.) 294:595--611. ITOH, T., KURIYAMA,H. and SUZUKI, H. (1981) Excitation-contraction coupling in smooth muscle of th~ guinea-pig mesenteric artery. J. Physiol. 321: 513-535. ITOH, T., KURIYAMA,H. and SUZUKI,H. (1983) Differences and similarities in the noradrenaline- and caffeine-in duced mechanical responses in the rabbit mesenteric artery. J. Physiol. 337: 6094529. ITOH, T., KANMURA, Y., KURIYAMA, H. and SUMIMOTO,K. (1986) A phorbol ester has dual actions on tht mechanical response in the rabbit mesenteric and porcine coronary arteries. J. Physiol. 375: 515-534. JAEFERJI, S. S. and MICHELL, R. H. (1976) Muscarinic cholinergic stimulation of phosphatidylinositol turnover il the longitudinal smooth muscle of the guinea-pig ileum. Biochem. J. 154: 653~57. JONES, L. M., COCKROFT, S. and MICHELL, R. H. (1979) Stimulation of phosphatidylinositol turnover i, various tissues by cholinergic and adrenergic agonists by histamine and by caerulein. Biochem. J. 182 669-676. KACZMAREK,L. K. (1987) The role of protein kinase C in the regulation of ion channels and neurotransmitte release. Trenda Neurosci. 10: 30-34. KA1BUCHI, K., TAKAI, Y., SAWAMURA,M., HOSHJIMA, M., JUJIKURA, T. and NISmZUKA, Y. (1983) Synergisti functions of protein phosphorylation and calcium mobilization in platelet activation. J. Biol. Chem. 2 ~ 6701-6704. KANMURA, Y., lyon, T., SUZUKI, H., Iro, Y. and KURIVAMA,H. (1983) Effects of nifedipine on smooth muscl cells of the rabbit mesenteric artery. J. Pharmacol. Exp. Ther. 226: 238-248. KENDALL, D. A. and NAHORSKI, S. R. (1985) Dihydropyridine calcium channel activators and antagonist influence depolarization-evoked inositol phospholipid hydrolysis in brain. Eur. J. Pharmacol. 115: 31-3( KENDALL, D. A. and NAHORSKI, S. R. (1986) Effects of lithium treatment on agonist-stimulated inositc phospholipid hydrolysis in rat brain slices. Br. J. Pharmac. 88: 255P. KILaINGER, H. (1984) Facilitation and inhibition by muscarinic agonists of acetylcholine release from guinea-pi myenteric neurones: mediation through different types of neuronal muscarinic receptors. Trends Pharmaco Sci. Suppl. 49 52. KILBINGER, H., STAUSS, P., ERLHOF, I. and HOLZER, P. (1986) Antagonist discrimination between subtypes c tachykinin receptors in the guinea-pig ileum. Naunyn Schmiedeberg's Arch. Pharmacol. 334: 181-187. KIRALY, M., AUDIGER,S., TRmOLLET, E., BARBERIS,C., DOLIVO, M. and DREIFUSS,J. J. (1986) Biochemical an electrophysiological evidence of functional vasopressin receptors in the rat superior cervical ganglion. Pro, Natl. Aead. Sci. 83: 5335-5339. KISHIMOTO, A., KAJIKAWA, N., SI-IIOTA,A. and NISmZUKA, Y. (1983) Proteolytic activation of Ca2+-activate~ phospholipid-dependent protein kinase by calcium-dependent protease. J. Biol. Chem. 258: 1156-1164. KOJIMA, I., SHIBATA, H. and OGArA, E. (1986) Pertussis toxin blocks angiotensin II-induced calcium influ but not inositol trisphosphate production in adrenal glomerulosa cell. FEBS Lett. 2114: 347-351. KUNO, M. and GARDNER, P. (1987) Ion channels activated by inositol 1,4,5-trisphosphate in plasma membrar of human T-lymphocytes. Nature 326: 301-304. KURIYAMA, H., ITO, Y., SUZUKI,H., KITAMURA,K. and ITOH, T. (1982) Factors modifying contraction-relaxatic cycle in vascular smooth muscles. Am. J. Physiol. 243: H641-H660. LAKSr~MANAN,J. (1978) Nerve growth factor induced turnover of phosphatidylinositol in rat superior cervic; ganglia. Biochem. Biophys. Res. Commun. 82: 767-775. LAKSHMANAN, J. (1979) Post-synaptic Pl-effect of nerve growth factor in rat superior cervical ganglia. Neurochem. 32: 1599-1601. LAPETINA, E. G. and CUATRECAOSAS,P. (1979) Stimulation of phosphatidic acid production in platelets preced, the formation of arachidoante and parallels the release of serotin. Biochim. Biophys. Acta. 573:394-40 LAPETINA, E. G. and MICHELL, R. H. (1973) Phosphatidylinositol metabolism in cells receiving extracellul~ stimulation. FEBS Lett. 31: 1-10. LAPE'rINA, E. G. and REEl', B. R. (1987) Specific binding of [alpha-32p]GTP to cytosolic and membran bound proteins of human platelets correlates with the activation of phospholipase C. Proc. Natl Acad. Sc 84:2261 2265. LAPETmA, E. G., BRILEV, P. A. and ROBERTIS,E. (1976a) Effect of adrenergic agonists on phosphatidylinosit labelling in heart and aorta, Biochim. Biophys. Acta 431: 624-4529.

lnositol phospholipid hydrolysis in the autonomic nervous system

413

LAPETINA,E. G., BROWN,W. E. and MICHELL, R. H. (1976b) Muscarinic cholinergic stimulation of phosphatidylinositol turnover in isolated rat superior cervical sympathetic ganglia. J. Neurochem. 26: 649-651. LAPETINA, E. G., GROSMAN, M. and CANESSADE SCARNATI,O. (1976C) Phosphatidylinositol-cleaving activity in smooth muscle from rat vaN deferens. Int. J. Biochem. 7: 507-513. LAPETINA, E. G., REEP, B., GANONG, B. R. and BELL, R. M. (1985) Exogenous sn-l,2-diacylglycerols containing saturated fatty acids function as bioregulators of protein kinase C in human platelets. J. Biol. Chem. 260: 1358-1361. LEE, M. H. and BELL, R. M. (1986) The lipid binding, regulatory domain of protein kinase C. J. Biol. Chem. 261: 14867-14870. LEEB-LUNDBERG, L. M. F., COTECCHIA, S., LOMASNEY,J. W., DEBERNARDIS,J. F., LEFKOW1TZ, R. J. and CARON, M. G. (1985) Phorbol esters promote alphal-adrenergic receptor phosphorylation and receptor uncoupling from inositol phospholipid metabolism. Proc. Natl Acad. Sci. 82: 5651-5655. LESLIE, B. A., PUTNEY,J. W. and SHERMAN,J. M. (1976) Alpha-adrenergic and cholinergic mechanisms for amylase secretion by rat parotid gland in vitro. J. Physiol. 260: 351-370. LEUNG, E., JOHNSON, C. I. and WOODCOCK,E. A. (1986) Stimulation of phosphatidylinositol metabolism in arterial and ventricular myocytes. Life Sci. 39:2215-2220. LIMAS, C. J. and LIMAS, C. (1985) Phorbol ester and diacylglycerol-mediated desensitisation of cardiac betaadrenergic receptors. Circ. Res. 57: 443~49. LIN, C. W., BIANCH1,B. R., GRANT, D., MILLER, T., DANAHER,E. A., TUFANO, M. D., KOPECKA, H. and NADZAN, A. M. (1986) Cholecystokinin receptors: Relationships among phosphoinositide breakdown, amylase release and receptor affinity in pancreas. J. Pharmacol. Exp. Ther. 236: 729-737. LITOSCH, I. and FAIN, J. N. (1985) 5-Methyltryptamine stimulates phospholipase C-mediated salivary gland membranes. J. Biol. Chem. 260: 16052-16055. LITOSCH, I. and FAIN, J. N. (1986) Regulation of phosphoinositide breakdown by guanine nucleotides. Life Sci. 39: 187-194. L1TOSCH, I., LIN, S. H. and FAIN, J. N. (1983) Rapid changes in hepatocyte phosphoinositides induced by vasopressin. J. Biol. Chem. 258:13727 13732. Low, M. G., CARROLL, R. C. and WEGLICKI,W. B. (1984) Multiple forms of phosphoinositide-specific phospholipase C of different relative molecular masses in animal tissues. Biochem. J. 221: 813-820. LUCAS, D. O., BAJJALICH, S. M., KOWALCHYK, J. A, and MARTIN, T. F. J. (1985) Direct stimulation by thyrotropin-releasing hormone (TRH) of polyphosphoinositide hydrolysis in GH3 cell membranes by a guanine nucleotide-modulated mechanism. Biochem. Biophys. Res. Commun. 132: 721-728. LUNDBERG,G. A., JERGIL, B. and SUNDLER, R. (1985) Subcellular localization and enzymatic properties of rat liver phosphatidylinositol-4-phosphate kinase. Biochim. Acta 846: 379-387. LYNCH, C. J., WILSON,P. l., BLACKMORE,P. F. and EXTON,J. H. (1986) The hormone-sensitive hepatic Na+-pump. Evidence for regulation by diacylglycerol and tumour promoters. J. Biol. Chem. 261:14551 14556. MACHADO-DE-DOMENECH,E. and SOLING,H. D. (1987) Effects of stimulation of muscarnic and of catecholamine receptors on the intracellular distribution of protein kinase C in guinea-pig exocrine glands. Biochem. J. 242: 749-754. MAJERUS, P. W,, CONNOLLY, T. M., DECKMAN, H., ROSS, T. S., BROSS,T. E., ISHII, H., BASSAL,V. S. and WILSON, O. B. (1986) The metabolism of phosphoinositide-derived messenger molecules. Science 234: 1519-1526. MARIER, S. H., PUTNEY, J. W. and VAN DE WALLE, C. M. (1978) Control of calcium channels by membrane receptors in the rat parotid gland. J. Physiol. 279: 141-151. MARSHALL, P. J., DIXON, J. F. and HOKIN, L. E. (1980) Evidence for a role in stimulus-secretion coupling of prostaglandins derived from release of arachidonyl residues as a result of phosphatidylinositol breakdown. Proc. Natl. Acad. Sci. 77: 3292-3296. MARTIN, T. F. J. (1983) Thyrotropin-releasing hormone rapidly activates the phosphodiester hydrolysis of polyphosphoinositides in GH3 pituitary cells. J. biol. Chem. 258: 14816-14822. MARTIN, Z. F. J. and KOWALCHYK,J. A. (1984a) Evidence for the role of calcium and diacylglycerol as dual second messengers in thyrotropin-releasing hormone action: involvement of diacylglycerol. Endocrinology 115: 1517 1526. MARTIN, T. F. J. and KOWALCHYK,J. A. (1984b) Evidence for the role of calcium and diacylglycerol as dual second messengers in thyrotropin-releasing hormone action: involvement of Ca 2+. Endocrinology 115:1527-1536. MASTERS, S. B., MARTIN, M. W., HARDEN, T. K. and BROWN, J. H. (1985) Pertussis toxin does not inhibit muscarinic-receptor-mediated phosphoinositide hydrolysis or calcium mobilisation. Biochem. J. 227: 933-937. MAYHEW, J. A., GILLON, K. R. W. and HAWTHORNE,J. N. (1983) Free and lipid inositol, sorbitol and sugars in sciatic nerve obtained post-mortem from diabetic patients and control subjects. Diabetologia 24: 13-15. MCMILLAN, M., CHERNOW, B. and ROTH, B. L. (1986) Phorbol esters inhibit alpha 1-adrenergic receptorstimulated phosphoinositide hydrolysis and contraction in rat aorta: evidence for a link between vascular contraction and phosphoinositide turnover. Biochem. Biophys. Res. Commun. 134: 970-974. MCPHAIL, L. C., CLAYTON, C. C. and SNYDERMAN,R. (1984) A potential second messenger role for unsaturated fatty acids: activation of Ca2÷-dependent protein kinase. Science 224: 622-624. MELLONI, E., PONTREMOLI, S., MICHETTI, M., SACCO, O., SPARRATORE, B. and HORECKER, B. L. (1986) The involvement of calpain in the activation of protein kinase C in neutrophils stimulated by phorbol myristic acid. J. Biol. Chem. 261: 4101-4105. MENKES, H. A., BARABAN,J. M., FREED, A. N. and SNYDER, S. H. (1986a) Lithium dampens neurotransmitter response in smooth muscle: relevance to action in affective illness. Proc. Natl Acad. Sci. 83: 5727-5730. MENKES,H. A., BARABAN,J. M. and SNYDER, S. I-I. (1986b) Protein kinase C regulates smooth muscle tension in guinea-pig trachea and ileum. Eur. J. Pharmacol. 122: 19-27. MERRITT, J. E. and RINK, T. J. (1987) Rapid increases in cystolic free calcium in response to muscarinic stimulation of rat parotid acinar cells. J. Biol. Chem. 262: 4958-4960.

414

S. P. WATSONand P. P. GODFREY

MERRITT,J. E. and RUaIN, R. P. (1985) Pancreatic amylase secretion and cytoplasmic free calcium. Effects ot ionomycin, phorbol dibutyrate and diaglycerols alone and in combination. Biochem. J. 230: 151-159. MERRITT, J. E., TAYLOR, C. W., RUalN, R. P. and PUTNEV,J. W. JR (1986a) Isomers of inositol trisphosphate in exocrine pancreas. Biochem. J. 238: 825-829. MERRITT, J. E., TAYLOR, C. W., RUalN, R. P. and PuTt,fLY, J. W. JR (1986b) Evidence suggesting that a Hove guanine nucleotide regulatory protein couples receptors to phospholipase C in exocrine pancreas. Biochem J. 236: 337-343. MICHELL, R. H. (1975) Inositol phospholipids and cell surface receptor function. Biochim. Biophys. Acta. 415 81- 147. MICHELL, R. H., KIRK, C. J., JONES, L. M., DOWNES, C. P. and CREBA,J. A. (1981) The stimulation of inosito lipid metabolism that accompanies calcium mobilisation in stimulated cells: defined characteristics am unanswered questions. Phil. Trans. R. Soc. Lond. B296: 123-138. MILLER, J. R., HAWKINS, D. J. and WELLS, J. N. (1986) Phorbol diesters alter the contractile responses of porcin. coronary artery. J. Pharmaeol. Exp. Ther. 239: 38~,2. MONCADA, S. and VANE, J. R. (1978) Pharmacology and endogenous roles of prostaglandin endoperoxides thromboxane A2, and prostacyclin. Pharmaeol. Rev. 30:293 331. MOVESIAN, M. A., THOMAS,A. P,, SELAK, M. and WILLIAMSON,J. R. (1985) Inositol trisphosphate does not releas Ca 2+ from permeabilised cardiac myocytes and sarcoplasmic reticulum. FEBS Lett. 185: 328-332. MUID, R. E., PENFIEED,A. and DALE, M. M. (1987) The diacylglycerol kinase inhibitor, R59022, enhances th superoxide generation from human neutrophils included by stimulation of f-met-leu-phe, IgG and C3] receptors. Biochem. Biophys. Res. Commun. 143: 630~638. MURPHY, R. L. W. and SMITH, M. E, (1987) Effect of diacylglycerol and phorbol ester on acetylcholine releas and action at the neuromuscular junction in mice. Br. J. Pharmacol. 90: 327-334. NA1RN, A. C., HEMMINGS,H. C., JR and GREENGARD,P. (1985) Protein kinases in the brain. Ann. Rev. Biochen 54:931 977. NAKAMURA,T. and UI, M. (1985) Simultaneous inhibitions of inositol phospholipid breakdown, arachidonic aci release, and histamine secretion in mast cells by islet-activating protein, pertussin toxin. A possib] involvement of the toxin-specific substrate in the Ca2+-mobilizing receptor-mediated biosignaling systen J. Biol. Chem. 260: 3584~3593. NAWA, M., NISHIKAWA, M., ADEESTEIN, R. S. and HIDAKA, H. (1983) Phorbol ester-induced activation c human platelets is associated with protein kinase C phosphorylation of myosin light chains. Nature 3(k 490492. NELEMANS, A. and DEN HERTOG, A. (1987) Changes in membrane potential and phosphoinostides durin alphal-adrenoceptor stimulation in smooth muscle cells of guinea-pig taeni caeci. Eur. J. Pharmacol. 131 215 223. NISHIKAWA, M., H1DAKA, H. and AOELSTEIN, R. S. (1983) Protein kinase C modulates in vitro phosphory ation of the smooth muscle heavy meromyosin by myosin light chain kinase. J. Biol. Chem. 25! 8808 8814. NISHIKAWA, M., SHIRAKAWA,S. and ADELSTEIN, R. S. (1985) Phosphorylation of smooth muscle myosin ligl chain kinase by protein kinase C. J. Biol. Chem. 260: 8978-8983. NISHIZUKA, Y. (1983) calcium, phospholipid turnover and transmembrane signalling. Phil. Trans. R. Soc. Lon B302:101 112. NISHIZUKA, Y. (1984) The role of protein kinase C in cell surface receptor signal transduction and tumo~ promotion. Nature 308:693 698. OCHS, R. (1986) lnositol trisphosphate and muscle. Trends Biochem. Sci. 11: 388. OHNE, S., KAWASAKI,H. IMAJOH,S., SUZUKI, K., INAGAKI,M., YOKOKURA, H., SAKOH, T. and HIDAKA, H. (198 Tissue-specific expression of three distinct types of rabbit protein kinase C. Nature 325: 161-166. ORELLANA, S., SOLSKI, P. A. and HEELER BROWN, J. (1987) Guanosine 5'-o-(thiotriphosphate)-dependent inosit trisphosphate formation in the membrane is inhibited by phorbol ester and protein kinase C. J. Biol. CheJ 262:1638 1643. OTANI, H., OTANI, H. and DAS, D. K. (1986) Evidence that phosphoinositide response is mediated ] alphal-adrenoceptor stimulation, but not linked with excitation-contraction coupling in cardiac musc Biochem. Biophys. Res. Commmun. 136:863 869. OWEN, N. C. (1986) Effect of catecholamines on Na+/H + exchange in vascular smooth cells. J. Cell. Biol. l( 2053- 2060. PARK, S. and RASMUSSEN,H. (1985) Activation of tracheal smooth muscle contraction: synergism between Ca and activators of protein kinase C. Proc. Natl. Acad. Sci. 82: 8835-8839. PARK, S. and RASMUSSEN,H. (1986) Carbachol-induced protein phosphorylation changes in bovine trach~ smooth muscle. J. Biol. Chem. 261: 15734-15739. PARKER, P. J., COUSSENS, L., TUTTY, N., RHEE, L., YOUNG, S., CHEN, E., STABLE, S., WATERFIELD, M. D. a U LLRICH,A. (1986) The complete primary structure of protein kinase C--the major phorbol ester receptq Science 23: 853-859. PAROD, R. J. and PUTNEY, J. W., JR (1978) Role of calcium in the receptor-mediated control of potassit permeability in the rat lacrimal gland. J. Physiol. 281: 371-381. PETERSEN,O. H. (1986) Calcium-activated potassium channels and fluid secretion by exocrine glands. Am. Physiol. 251: GI GI3. PETERSEN, O. H. and MARUYAMAY. (1984) Calcium-activated potassium channels and their role in secretk Nature 307: 693-696. PICKARD, M. R., HAWTHORNE,J. N., HAYASHI,E. and YAMADA,S. (1977) Effects of surugatoxin and other nicoti~ and muscarinic antagonists on phosphatidylinositol metabolism in active sympathetic ganglia. Bioche Phurmacol. 26: 448~450. POGGIOLt, J. and PUTNEY, J. W., JR (1982) Net calcium fluxes in parotid acinar ceils. Evidence for hormone-sensitive calcium pool in or near the plasma membrane. Pflug. Arch. 392: 239-243.

lnositol phospholipid hydrolysis in the autonomic nervous system

415

POGGIOLI, J., SULPICE,J. C. and VASSORT,G. (1986) Inositol phosphate production following alpha-adrenergic, muscarinic and electrical stimulation in isolated rat heart. FEBS Lett. 206: 292-298. PRESTI, C. F., SCOTT, B. T. and JONES, L. R. (1985) Identification of an endogenous protein kinase C activity and its intrinsic 15-kilodalton substrate in purified canine cardiac sarcolemmal vesicles. J. Biol. Chem. 260: 13879-13889. PUTNEY, J. W. (1977) Muscarinic alpha-adrenergic and peptide receptors regulate the same calcium influx sites in the parotid gland. J. Physiol. 268: 139-149. PUTNEY, J. W. (1979) Stimulus-permeability coupling: role of calcium in the receptor regulation of membrane permeability. Pharmaeol. Rev. 30: 209-245. PUTNEY, J. W. (1981) Recent hypotheses regarding the phosphatidylinositol effect. Life Sci. 29:1183 1194. PUTNEY, J. W. (1986a) Identification of cellular activation mechanisms associated with salivary secretions. Ann. Ree. Physiol. 48: 75-88. PUTNEY, J. W. (1986b) A model for receptor-regulated calcium entry. Cell Calcium 7: 1-12. PUTNEY, J. W., DEWITT, L. M., HOYLE, P. C. and MAcKINNEY, J. S. (1981) Calcium, prostaglandin and the phosphatidylinositol effect in exocrine gland cell. Cell Calcium 2: 561-571. PUTNEY, J. W., MCKINNEY, J. S., AUB, D. L. and LESLIE, B. A. (1984) Phorbol ester-induced protein secretion in rat parotid gland. Relationship to the role of inositol lipid breakdown and protein kinase C activation in stimulation-secretion coupling. Molecular Pharmacol. 26: 261-266. PUTNEY, J. W., JR, AUB, D. L., TAYLOR, C. W. and MERRITT, J. E. (1986) Formation and biological actions of inositol 1,4,5-trisphosphate. Fed. Proc. 45: 2634-2638. QulsT, E. E. and SATUMTIRA,N. (1987) Muscarinic receptor stimulated phosphoinositide turnover in cardiac atrial tissue. Bioehem. Pharmacol. 36: 499-505. RASMUSSEN, H., FORDER, J., KOJIMA, 1. and SCRIABINE, A. (1984) TPA-induced contraction of isolated rabbit vascular smooth muscle. Biochem. Biophys. Res. Commun. 122: 776-784. RINK, T. J., SANCHEZ,A. and HALLAM,T. U. (1983) Agonist selectivity and second messenger concentration in Ca 2+-mediated secretion. Nature 305:317 319. ROUSSlER, M. F., CAPPONI, A. M. and VALLOTTON,M. B. (1987) Metabolism of inositol-l,4,5-trisphosphate in permeabilized rat aortic smooth-muscle cells. Dependence on calcium concentration. Biochem. J. 245: 305-307. RUBXN, R. P. (1974) Calcium and the Secretory Process. Plenum Press, New York. RUBIN, R. P. (1984) Stimulation of inositol trisphosphate accumulation and amylase secretion by caerulein in pancreatic acini. J. Pharmacol. Exp. Ther. 231: 623-627. RUBIN, R. P., GODFREY, P. P., CHAPMAN, D. A. and PUTNEY, S. W. (1984) Secretagogue-induced formation of inositol phosphates in rat exocrine pancreas. Biochem. J. 219: 655-659. SAIDA, K. and VAN BREEMAN,C. (1987) GTP requirement for inositol-l,4,5-trisphosphate-induced Ca 2+ release from sarcoplasmic reticulum in smooth muscle. Biochem. Biophys. Res. Commun. 144:1313 1316. SALMON, D. M. W. and HONEYMAN,T. W. (1980) Proposed mechanism of cholinergic action in smooth muscle. Nature 284: 344-345. SALMON, D. M. W., MALLOWS, R. S. E., MELLAR, S. J. and BOLTON,T. B. (1986) Are diacylglycerols involved in the response of smooth muscle to neurotransmitters? Biochem. Soc. Trans. 14: 1150-1151. SASAGURI,T., HIRATA,M. and KURIYAMA,H. (1985) Dependence on Ca 2+ of the activities of phosphatidylinositol 4,5-bisphosphate phosphodiesterase and inositol 1,4,5-trisphosphate phosphatase in smooth muscles of the porcine coronary artery. Biochem. J. 231: 497-503. SASAGURI, T., HIRATA, M., ITOH, T., KOGA, T. and KUR1YAMA,H. (1986) Guanine nucleotide binding protein involved in muscarinic responses in the pig coronary artery is insensitive to islet-activating protein. Biochem. J. 239: 567-574. SERHAN, C., ANDERSON, P., GOODMAN, E., DUNGAM, P. and WEISSMANN,G. (1981) Phosphatidate and oxidized fatty acids are calcium ionophores; studies employing arsenzo III in liposomes. J. Biol. Chem. 256: 2736-2741. SEYFRED,M. A. and WELLS, W. W. (1984) Subcellular site and mechanism of vasopressin-stimulated hydrolysis of phosphoinositides in rat hepatocytes. J. Biol. Chem. 259: 7666-7672. SHAPIRA, R., SILBERBERG,S. D., GINSBURG, S. and RAHAMIMOFF, R. (1987) Activation of protein kinase C augments evoked transmitter release. Nature 325: 58-60. SHAVONI,Y., TEUERSTEIN,I. and LEVY,J. (1986) Phosphoinositide phospheryl 12 precedes growth in rat mammary tumours. Biochem. Biophys. Res. Commun. 134: 876-882. SHERMAN,W. R., LEAVITT, A. L., HONCHER, M. P., HALLCHER, L. M. and PHILLIPS, B. E. (1981) Evidence that lithium alters phosphoinositide metabolism; chronic administration elevates primarily D-myo-inositol-1phosphate in cerebral cortex of the rat. J. Neuroehem. 36:1947 1951. SHUNTOHH. and TANAKA,C. (1986) Activation of protein kinase C potentiates norepinephrine release from sinus node. Am. J. Physiol. 251: C833-C840. SIBLEY, D. R., NAMBI, P., PETERS, J. R. and LEFKOWITZ, R. J. (1984) Phorbol esters promote beta-adrenergic receptor phosphorylation and adenylate cyclase desensitisation in duck erythrocytes. Biochem. Biophys. Res. Commun. 121: 973-979. SmLEY, D. R., BEBIVUC,J. L., CARON, M. G. and LEEKOWlTZ,R. L. (1987) Regulation of transmembrane signalling by receptor phosphorylation. Cell 48:913 922. SIESS, W., SIEGEL, F. and LAPETINA, E. G. (1983) Arachidonic acid stimulates the formation of 1,2-diacylglycerol and phosphatidic acid in human platelets: degree of phospholipase C activation correlates with protein phosphorylation platelet shape change, serotonin release and aggregation. J. Biol. Chem. 258:11236-11242. SOMYLO, A. V., BOND, M., SOMYLO, A. P. and SCARVA,A. (1985) Inositol trisphosphate-induced calcium release and contraction in vascular smooth muscle. Proc. Natl Acad. Sci. 82: 5231-5235. SPAT, A., FAmATO, A. and RUBIN, R. P. (1986) Binding of inositol trisphosphate by a liver microsomal fraction. Biochem. J. 233: 929-932. SPECTOR, R. and LORENZO, A. V. (1975) myo-lnositol transport in the central nervous system. Am. J. Physiol. 228: 1510-1518.

416

S. P. WATSONand P. P. GODFREY

SPEDDING, M. (1987) Interaction of phorbol esters with Ca 2+ channels in smooth muscle. Br. J. Pharmacol. 91: 377 384. STERNWEIS, P. C. and ROnlSHAW,J. D. (1984) Isolation of 2 proteins with high aMnity for guanine nucleotides from membranes of bovine brain. J. Biol. Chem. 259: 13806-13813. STOREY, D. J., SHEARS,S. B., KIRK, C. J. and MICHELL, R. H. (1984) Stepwise enzymatic dephosphorylation of inositol 1,4,5-trisphosphate to inositol in liver. Nature 312: 374-376. STREB, H., IRVINE, R. F., BERRIDGE, M. J. and SCHULZ, I. (1983) Release of Ca 2+ from a non-mitochondrial intracellular store in pancreatic acinar cells by inositol 1,4,5-trisphosphate. Nature 306: 67-69. SUEMATSU,E., HIRATA, M., HASHIMOTO,T. and KURIYAMA,H. (1984) Inositol 1,4,5-trisphosphate Ca 2+ from intracellular storage sites in skinned single cells of porcine coronary artery. Biochem. Biophys. Res. Commun 120:481~485. SUEMATSU,E., HIRATA,M., SASAGURI,T., HASHIMOTO,T. and KURIYAMA,M. (1985) Roles of Ca 2+ on the inosito] 1,4,5-trisphosphate-induced release of Ca :+ from saponin-permeabilised single cells of the porcine coronar~ artery. Cutup. Biochem. Physiol. 82A: 645649. SUGIMOTO,Y., WHITMAN,M., CANTLEY,L. C. and ERIKSON,R. L. (1984) Evidence that the Rous sarcoma viru,, transforming gene product phosphorylates phosphotidylinositol and diacylglycerol. Proc. Natl. /tcad. Sei (U.S.A.) 81: 2117-2121. SUGIYA, H., TENNES, K. A. and PUTNEY,J. W., JR (1987) Homologous desensitization of substance-P-induced inositol polyphosphate formation in rat parotid acinar cells. Biochem. J. 244:647 653. SUZUKI,K., PETERSEN,C. C. H. and PETERSEN,O. H. (1985) Hormonal activation of single K + channels via internal messenger in isolated pancreatic acinar cells. FEBS Lett. 192:307 312. SYBERTZ, E. J., DESIDERO,D. M., TETZLOFF,G. and CHUI, P. J. S. (1986) Phorbol dibutyrate contractions in rabbi1 aorta: calcium dependence and sensitivity to nitrovasodilators and 8-BR-cyclic GMP. J. Pharmacol. Exp Ther. 239:78 83. TAKUWA, Y., TAKUWA,N. and RASMUSSEN,H. (1986) Carbachol induces a rapid and sustained hydrolysis o: polyphosphoinositides in bovine tracheal smooth muscle measurements of the mass of polyphospho inositides, 1,2-diacylglycerol, and phosphatidic acid. J. Biol. Chem. 261: 14670-15675. TANAKA,C., TANIYAMA,K. and KUSONOKI,M. (1984) A phorbol ester and A23187 act synergistically to release acetylcholine from the guinea-pig ileum. FEBS Lett. 175: 165-169. TAPLEY, P. M. and MURRAY,A. W. (1984) Modulation of Ca2+-activated, phospholipid-dependent proteir kinase in platelets treated with a tumour-promoting phorbol ester. Biochem. Biophys. Res. Commun. 122 158 164. TAYLOR, C. W. and MERRITT,J. E. (1986) Receptor coupling to polyphosphoinositide turnover: parallel with thi adenylate cyclase system. Trends Pharmacol. Sci. 7:238 242. TAYLOR, C. W. and PUTNEY,J. W., JR (1985) Size of the inositol 1,4,5-trisphosphate-sensitive calcium pool ir guinea-pig hepatocytes. Biochem. J. 232: 435~438. TRIMBLE, E. R., BAUZZONE,R., MEEHAN, C. J. and BIDEN, T. J. (1987a) Rapid increases in inositol 1,4,5-tris phosphate, inositol 1,3,4,5-tetrakisphosphate and cytosolic free Ca 2+ in agonist-stimulated pancreatic acin of the rat. Biochem. J. 242: 289-292. TRIMBLE, E. R., BRUZZONE,R., BIDEN,T. J., MEEHAN,C. J., ANDREU, D. and MERR1FIELD,R. B. (1987b) Secretir stimulates cyclic AMP and inositol trisphosphate production in rat pancreatic acinar tissue by two full3 independent mechanisms. Proc. Natl Acad. Sei. U.S.A. 84: 3146-3150. UHLING~R. J., PIPIC, V., JIANG,H. and EXTON,J. H. (1986) Hormone-stimulated polyphosphoinositide breakdowi in rat liver plasma membranes. J. Biol. Chem. 261: 214(~2146. UMEKAWA,H. and H1DAKA,H. (1985) Phosphorylation of caldesmon by protein kinase C. Biochem. Biophys. Res Commun. 132: 56-62. VAN ROOIJEN, L. A. A., HAJRE, A. K. and AGRANOFF, B. W. (1985) Tetraenoic species are conserved il muscarinically enhanced inositide turnover. J. Neurochem. 44: 54(~543. VON TSCHARNER,V., PROD'HUMB., BAGGIOLINI,M. and REUTER,H. (1986) Ion channels in human neutrophil: activated by a rise in free cytosolic calcium concentration. Nature 324: 369-372. WAKELAM,M. J. O., DAVIES,S. A., HOUSLAY,M. D., MCKAY, I., MARSHALL,C. J. and HALL, A. (1986) Norma p21 n-ras couples bombesin and other growth factor receptors to inositol phosphate production. Nature 323 173-176. WALDO,G. L., EVANS,T., FRASER,E. n., NORTHUP,J. K., MARTIN,M. W. and HARDEN,T. K. (1987) Identificatiot and purification from bovine brain of a guanine-nucleotide-binding protein distinct from Gs, Gl and GO Bioehem. J. 246: 431-439. WALKER,J. W., SOMYLO,A. V., GOLDMAN,Y. E., SOMYLO,A. P. and TRENTHAM,n. R. (1987) Kinetics of smootl and skeletal muscle activation by laser pulse photolysis of caged inositol 1,4,5-trisphosphate. Nature 327 249 252. WALLACE, M. A. and FAIN, J. N. (1985) Guanosine 5'-o-thiophosphate stimulates phospholipase C activity il plasma membranes of rat hepatocytes. J. Biol. Chem. 2611: 9527-9530. WAXANABE,Y., HORN, F., BAUER, S. and JAKOBS,K. H. (1985) Protein kinase C interferes with N-mediate~ inhibition of human platelet adenylate cyclase. FEBS Lefts. 192:23 27. WATSON, S. P. and DOWNES,C. P. (1983) Substance P-induced hydrolysis of inositol phospholipids in guinea-pil ileum and rat hypothalamus. Fur. J. Pharmacol. 93: 245-253. WATSON, S. P., McCONNELL, R. T. and LAPETINA,E. G. (1984) The rapid formation of inositol phosphates il human platelets by thrombin is inhibited by prostacyclin. J. Biol. Chem. 259: 13199-13203. WATSON, S. P., McCoNYeLL, R. T. and LAPETINA,E. G. (1985) Decanoylysophosphatidic acid induces platele aggregation through an extracellular action: Evidence against a second messenger role for lysophosphatidi, acid. Biochem. J. 232: 61-66. WATSON, S. P., MCNALLY, J., SHIPMAN,L. J. and GODFREY,P. P. (1988) The action of the protein kinase ( inhibitor, staurosporine, on human platelets; evidence against a regulatory role for protein kinase C in th formation of inositol trisphosphate by thrombin. Biochem. J. 249: 345-350.

Inositol phospholipid hydrolysis in the autonomic nervous system

417

WEISS,S. J. and PUTNEY,S. W. (1981) The relationship of phosphatidylinositol turnover to receptors and calcium channels in rat parotid acinar cells, Biochem. J. 194: 463-468. WEISS, S. J., MCKINNEY,J. S. and PUTN~Y,J. W., JR (1982) Receptor mediated net breakdown of phosphatidylinositol-4,5-biphosphate in parotid acinar cells. Biochem, J. 206: 555-560. WHITMAN, M., KAPLAN, D., SCHAFFHAUSEN,B., CANTLEY, L. and ROBERTS,T. M. (1985) Association of phosphatidylinositol kinase activity with polyoma middle-T competant for transformation. Nature 315: 239-242. WILLIAMS,D. A., FOGARTY,K, E., TSIEN,R. Y. and FAY, F. S. (1985) Calcium gradients in single smooth muscle cells revealed by the digital imaging microscope using Fura-2. Nature 318: 558-561. WILSON,D, B., BROSS,T. E., HOFFMAN,S. L. and MAJERUS,P. W. (1984) Hydrolysis of polyphosphoinositides by purified sheep seminal vesicle phospholipase C enzymes. J. Biol. Chem. 259:11718-11724. WILSON,D. B., NEUFELD,E. J. and MAJERUS,P. W. (1985) Phosphoinositide interconversion in thrombin-stimulated human platelets. J. Biol. Chem. 260: 1046--1051. WILSON,D, B., BROSS,T. E., SHERMAN,W. R., BERGER,R. A. and MAJERUS,P. W. (1986) Inositol cyclic phosphates are produced by cleavage of phosphatidylphosphoinositols (polyphosphoinositides) with purified sheep seminal vesicle phospholipase C enzymes. Proc. Natl Acad. Sci. U.S.A. 82: 4013-4017. WOLF,M., CUATRECASAS,P. and SAYHOUN,N. (1985) Interaction of protein kinase C with membranes is regulated by Ca 2+, phorbol esters and ATP. J. Biol. Chem. 260: 15718-15722. WOOD, A, J. and GOODWIN,(3. M. (1987) A review of the biochemical and neuropharmacological actions of lithium. Psychological Medicine 17: 579~500. WOOTEN, M. W. and WRENN, R, W. (1984) Phorbol ester-induces intracellular translocation of phospholipid/Ca2e-dependent protein kinase and stimulates amylase secretion in isolated pancreatic icini. FEBS Lett. 171: 183-186. YAMAGUCHI,K., HIRATA,M. and KURIYAMA,H. (1987) Calmodulin activates inositol 1,4,5-trisphosphate-3-kinase activity in pig aortic smooth muscle. Bioehem, .I. 244: 787-791.