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The neural cell adhesion molecule (NCAM) in development and plasticity of the nervous system
Experimental Gerontology, Vol. 33, Nos. 7/8, pp. 853– 864, 1998 Copyright © 1998 Elsevier Science Inc. Printed in the USA. All rights reserved 0531-5565/98 $19.00 1 .00
PII S0531-5565(98)00040-0
THE NEURAL CELL ADHESION MOLECULE (NCAM) IN DEVELOPMENT AND PLASTICITY OF THE NERVOUS SYSTEM
L.C.B. RØNN, B.P. HARTZ and E. BOCK The Protein Laboratory, Institute for Molecular Pathology, University of Copenhagen, Denmark
Abstract—The neural cell adhesion molecule (NCAM) is a member of the immunoglobulin superfamily and is strongly expressed in the nervous system. NCAM is found in three major forms, of which two—NCAM-140 and NCAM-180 —are transmembrane proteins, while the third—NCAM-120 —is attached to the membrane via a glycosylphosphatidyl inositol anchor. In addition, soluble NCAM forms exist in brain, cerebrospinal fluid, and plasma. NCAM mediates cell adhesion through homophilic as well as through heterophilic interactions. Following NCAM binding, transmembrane signalling is believed to be activated, resulting in increased intracellular calcium. By mediating cell adhesion to other cells and to the extracellular matrix and by activating intracellular signaling pathways, NCAM influences cell migration, neurite extension, and fasciculation, and possibly formation of synapses in the brain. From studies on NCAM knock-out mice, NCAM have been shown to be crucial for the formation of the olfactory bulb and the mossy fiber system in the hippocampus. In addition, NCAM is important for neuronal plasticity in the adult brain associated with learning and regeneration. © 1998 Elsevier Science Inc. Key Words: NCAM, synaptic plasticity, cell adhesion, neurite extension, learning, regeneration, signal transduction, long-term potentiation
STRUCTURE OF THE NCAM PROTEIN THE NEURAL CELL adhesion molecule (NCAM) belongs to the cell adhesion molecules of the immunoglobulin (Ig) superfamily (IgSF) characterized by the Ig domain (Williams and Barclay, 1988; Bru¨mmendorf and Rathjen, 1995). The Ig domain contains approximately 100 amino acids forming two b-sheets. Based on structure, Ig domains can be classified to the constant type 1 (C1-set), the constant type 2 (C2-set), the variable type (V-set), or the intermediate set (I-set) of Ig domains, the I-set being a recently characterized structure intermediate between the V- and the C-forms. The N-terminal Ig1 of NCAM was recently shown to belong to the I-set by NMR (Thomsen et al., 1996), together with the M5 domain of titin (Pfuhl and Pastore, 1995), telokin Correspondence to: Lars Christian B. Rønn, The Protein Laboratory, Institute for Molecular Pathology, Panum Institute Bld. 6.2., Blegdamsvej 3, DK-2200, Copenhagen N, Denmark; Fax: 145-35-36-01-16; E-mail: [email protected] (Received 1 May 1998; Accepted 28 May 1998) 853
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FIG. 1. (A) NCAM structure. In brain, NCAM is found in three major forms that are either transmembrane (NCAM-180, NCAM-140) or attached to the membrane via a glycosylphosphatidyl inositol (GPI) anchor (NCAM-120). In addition, soluble truncated or shedded forms of NCAM (NCAMs1, 2, and 3) exist. (B) The three major forms of NCAM are generated by alternative splicing. Exon 15 encodes a signal for GPI linkage. Use of exon 15 results in the expression of NCAM-120 without transmembrane and cytoplasmic domains. In contrast, omitting exon 15 results in the expression of the transmembrane forms NCAM-140 and NCAM-180. The cytoplasmic part of NCAM-180 is larger than that of NCAM-140, due to the use of exon 18 in mRNAs encoding this isoform. Further diversity of the mRNA species results from the alternative splicing of the exons a, b, c, AAG, and VASE. In addition, NCAM is modified posttranslationally, particularly important being the addition of polysialic acid (PSA) to the fifth Ig domain.
(Holden et al., 1992), and the first domain of VCAM (Wang et al., 1995). In addition to these, a number of other domains of the IgSF has been predicted, based on conservation of structurally important residues, to be of the I-set type including the second and the third Ig domains of NCAM, the third and the fifth Ig domains of mouse L1, the third Ig domain of mouse contactin, and the fifth Ig domain of Drosophila neuroglian. Indeed, the I-set structure appears to be characteristic for neuronal cell adhesion molecules (Thomsen et al., 1996). Three major forms of NCAM generated by alternative splicing are found (Murray et al., 1986; Walsh and Dickson, 1989). In all three forms, the extracellular portion of the protein contains five Ig domains and two fibronectin homology (FnIII) domains (Fig. 1). One NCAM form is attached to the membrane by a glycosylphosphatidyl inositol (GPI) anchor (NCAM-120). The two other major forms contain a transmembrane domain and a short (NCAM-140) or a longer (NCAM-180) cytoplasmic domain. In addition, alternative splicing may generate further variability by the optional insertion of four exons, a, b, c, and AAG between exons 12 and 13 encoding the stretch between the two FnIII domains and by the insertion of the so-called “variable domain alternatively spliced exon” (VASE) between exons 7 and 8 encoding the fourth Ig domain (Small et
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al., 1988). All NCAM forms are encoded by a single gene located in chromosome 9 in mouse, chromosome 8 in the rat, and chromosome 11 in humans. Recently, a transmembrane NCAMlike molecule, NCAM2, was cloned from a human fetal brain cDNA library (Paoloni-Giacobino et al., 1997). The NCAM2 gene was located to the human chromosome 21, but the function of NCAM2 remains to be determined. In addition to structural variations in the NCAM transcripts modulated by alternative splicing, the molecule is submitted to a series of posttranslational modifications. Thus, the NCAM protein can be modified by phosphorylation, sulphation, and glycosylation (Sorkin et al., 1984; Linnemann et al., 1985; Krog and Bock, 1992; Gegelashvili et al., 1993). Notably, fractions of the NCAM proteins carry the L2/HNK-1 carbohydrate epitope and/or polysialic acid (PSA). The L2/HNK-1 epitope is a sulphated glucoronyl residue recognized by the monoclonal antibodies L2 and HNK-1, and the epitope is supposed to be functionally important, as the antibodies have been reported to interfere with cell adhesion. The epitope is shared by a number of neuronal cell adhesion molecules including L1 and myelin associated glycoprotein (MAG) as well as by other glycoproteins and glycolipids. In contrast, NCAM is responsible for the majority of PSA expressed in the brain. Thus, in NCAM knock-out mice PSA expression is reduced by approximately 85% (Cremer et al., 1994). However, it has been reported that PSA is also expressed by polysialyltransferase (Mu¨hlenhoff et al., 1996), one of the two enzymes known to synthesize the PSA moiety on NCAM, as well as by the a-subunit of a sodium channel (Zuber et al., 1992), and by an intracellular protein of certain cancer-cells (Martersteck et al., 1996). PSA consists of long homopolymers of a2– 8-linked N-acetyl neuraminic residues attached to N-linked carbohydrates on the fifth Ig domain of NCAM (Zuber et al., 1992; Rougon, 1993). PSA-NCAM can be synthesized by two polysialyltransferases (Eckhardt et al., 1995; Nakayama et al., 1995; Scheidegger et al., 1995; Yoshida et al., 1995; Nakayama and Fukuda, 1996), polysialyltransferase-1 (PST) and sialyltransferase-X (STX), the expression of which are differentially regulated in a tissue-specific manner (Angata et al., 1997; Phillips et al., 1997). PSA-NCAM is widely expressed in the embryonic and early postnatal brain; hence, the term “embryonic NCAM” (eNCAM), constituting up to 30% of the NCAM protein by weight. The expression decreases to approximately 10% by weight in the adult brain (Edelman and Chuong, 1982; Rougon et al., 1982). Therefore, embryonic NCAM appears as a broad smeared band in Western blotting due to the different lengths of the attached PSA chains, while distinct bands are seen in Western blottings of NCAM from adult brain. Concomitant with the decreased PSA-NCAM expression during development, the fraction of NCAM molecules containing the alternatively spliced VASE exon increases from a few percent in the embryonic brain to approximately 50% in the adult brain (Small and Akeson, 1990). In the brain, NCAM is primarily expressed by neurons. However, low amounts of NCAM is also expressed by glial cells (Noble et al., 1985). In addition to membrane-attached NCAM, soluble NCAM forms exist in the cerebrospinal fluid and in plasma (Bock et al., 1987; Olsen et al., 1993). The main form of soluble NCAM (NCAM-s3) appears as a double band in Western blotting with an Mr of 110/115 representing the extracellular part of NCAM-120 released by phospholipase activity as well as the extracellular part of all NCAM forms released by extracellular proteolysis. In addition, shedded NCAMs with Mrs of approximately 140 (NCAM-s2) and 180 (NCAM-s1) exist. These forms are recognized by antibodies against cytoplasmic epitopes of NCAM (Olsen et al., 1993). A fraction of these latter forms are associated with lipids.
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FIG. 2. Hypothetical regulation of homophilic NCAM binding by polysialylation. (A) Interaction between Ig1- and Ig2-mediated homophilic binding of PSA-NCAM. (B) Reciprocal interaction between all five Ig domains of NCAM in the absence of PSA.
NCAM FUNCTIONS: CELL ADHESION AND SIGNAL TRANSDUCTION The classical role of NCAM is to mediate cell adhesion through a homophilic action, NCAM on one cell binding to NCAM on another. The site(s) of homophilic NCAM binding is controversial, and has been proposed to be mediated by a reciprocal interaction between the third Ig domain of two NCAM molecules on opposing membranes (Rao et al., 1992, 1993, 1994), or by a reciprocal interaction between all five Ig domains, the fifth Ig domain binding the first Ig domain, the second Ig domain binding the fourth Ig domain, and the third Ig domain binding the third Ig domain (Ranheim et al., 1996). Recently, the nature of the homophilic NCAM binding was addressed by investigating the binding between individual NCAM domains by plasmon surface resonance analysis. Here, binding was demonstrated between the first and the second Ig domains, suggesting that a double reciprocal interaction between these two domains mediates homophilic NCAM binding (Kiselyov et al., 1996). It is possible that several mechanisms of homophilic NCAM binding exist, the preferred binding conformation being dictated by the glycosylation and/or alternative splicing of NCAM, for example homophilic binding of mature NCAM forms without extensive polysialylation may involve all five Ig domains while the presence of PSA on the fifth Ig domain in embryonic NCAM may favor interaction of the first and the second Ig domains by sterically preventing interactions involving the fifth and the fourth Ig domains (Fig. 2). Whatever the mechanisms, it is believed that homophilic NCAM binding activates signal transduction. In vitro, NCAM or NCAM antibodies have been shown to result in increased intracellular calcium in certain neuronal cells (Schuch et al., 1989; von Bohlen und Halbach et al., 1992). Moreover, homophilic NCAM interactions stimulate neurite extension, apparently by activating a signal transduction pathway resulting in a calcium influx through voltage-dependent calcium channels (Doherty et al., 1991). It has been proposed that NCAM binds to the fibroblast growth factor receptor (FGF-R), thereby activating intracellular signaling (Williams et al., 1994; Saffell et al., 1997). The FGF-Rs contain a
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so-called CAM-homology domain (CHD) with three adjacent sequences with homology to sequences in NCAM, L1 and N-cadherin, respectively. By binding the CHD, these three CAMs may activate a common signal transduction pathway (Doherty and Walsh, 1996; Hall et al., 1996). The presumed NCAM binding region of the CHD in the FGF-R is homologous to the alternatively spliced VASE exon. Interestingly, adult NCAM forms containing the VASE exon are poor stimulators of neurite extension (Doherty et al., 1992), possibly because the presence of VASE in NCAM prevents binding of NCAM to the VASE-like sequence in the FGF-R. Others have presented evidence that NCAM mediated stimulation of neurite outgrowth requires p59fyn tyrosine kinase activity. Hence, NCAM specific stimulation of neurite extension is absent in neurons from fyn knock-out mice (Beggs et al., 1994). Moreover, NCAM-140 is reported to interact constitutively with the p59fyn, this complex in turn recruiting p125FAK following homophilic NCAM binding (Beggs et al., 1997). Presently, it is not known whether both of these pathways are activated under similar circumstances or whether crosstalk may occur. In addition to the FGF-R, the cell adhesion molecules L1 (Kadmon et al., 1990a) and TAG-1/axonin-1 (Milev et al., 1996) are believed to bind NCAM in heterophilic interactions. The NCAM-L1 binding may depend on an interaction between a carbohydrate on L1 and a lectin-like domain in the fourth Ig domain of NCAM (Kadmon et al., 1990a; Horstkorte et al., 1993). NCAM may thus strengthen homophilic L1 binding in a so-called assisted-homophilic interaction (Kadmon et al., 1990b). The presence of PSA on NCAM is thought to inhibit the homophilic L1 binding as well as homophilic NCAM binding, and thereby to decrease cell– cell adhesion (Acheson et al., 1991; Tang et al., 1994). However, under certain conditions PSA may function directly as a receptor (Joliot et al., 1991) and thereby possibly promote, rather than inhibit, cell adhesion. In addition to mediating cell– cell binding, NCAM can bind components of the extracellular matrix including collagens (Probstmeier et al., 1989), chondroitin sulphate proteoglycans (Grumet et al., 1993), and heparan sulphates (Cole et al., 1986) notably agrin (Storms et al., 1996). The overall adhesive behavior of a given NCAM expressing neuron thus depends on the expression of various NCAM ligands in the environment, including the extracellular matrix and other neurons and glial cells as well as on the splicing and glycosylation state of the expressed NCAM. THE ROLE OF NCAM IN DEVELOPMENT OF THE NERVOUS SYSTEM During development, NCAM expression is regulated in a manner suggesting that NCAM may be involved in morphogenesis (Edelmann and Crossin, 1991). The overall decrease in PSANCAM expression and the parallel increase in the fraction of NCAM copies containing the VASE exon with development is generally thought to change NCAM from being a plasticity promoter to a stability promoter (Rutishauser and Landmesser, 1996). It is believed that PSA-NCAM or eNCAM allows structural remodeling by decreasing cell adhesion mediated by NCAM and L1 as a necessary prerequisite for activity-dependent formation of proper neuronal connections to occur in the developing brain. In the adult brain, most NCAM molecules carry low amounts of PSA and, therefore, tend to stabilize persisting structures through strong homophilic bindings. During development, PSA-NCAM expression correlates in time and space with axon outgrowth, branching, and contact formation in the corticospinal (Daston et al., 1996) and the retinotectal (Fraser et al., 1984; Yin et al., 1995; Williams et al., 1996) systems as well as in the formation of the neuromuscular junction (Landmesser et al., 1990; Tang et al., 1994). In transgenic mice without NCAM expression, the olfactory system develops abnormally resulting in a dramatically reduced olfactory bulb when compared to wild-type mice (To-
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masiewicz et al., 1993; Cremer et al., 1994). This effect can be phenocopied by removing PSA enzymatically by endo-N in wild-type mice (Ono et al., 1994), strongly suggesting that the expression of PSA-NCAM is crucial for the normal migration of olfactory granule cell precursors. In the hippocampal region of NCAM null mutants, the mossy fiber system does not fasciculate normally, which in turn, leads to secondary effects on the generation of synapses in the CA3 region (Cremer et al., 1997). In this region, polysialylation of NCAM thus appears to promote fasciculation of the mossy fiber axons in contrast to the defasciculating role normally attributed to PSA-NCAM. Despite these and other abnormalities in the nervous system of NCAM mutants, these mice develop relatively well, suggesting that other molecules may partially substitute for NCAM. In addition to the as yet poorly investigated NCAM2, L1, and N-cadherin are plausible candidates for partially substituting NCAM as they, as mentioned above, have been proposed to share signaling pathways (Doherty and Walsh, 1996) although the expression patterns of these CAMs are not similar to that of NCAM. In addition to the above-mentioned transgenic mice, a targeted mutation to express only secreted, soluble NCAM forms have been produced. However, this mutation appeared to be dominant lethal during embryogenesis, with severe morphological malformations being observed in chimeric embryos (Rabinowitz et al., 1996). This indicates that soluble NCAM forms have the potential to influence morphological development through heterophilic NCAM binding. NCAM IN LEARNING-ASSOCIATED PLASTICITY Generally, it is believed that in a learning process neuronal connections are subject to structural changes to establish long-term memory. Several recent studies indicate a role for NCAM in learning and establishment of long-term memory (Fields and Itoh, 1996). First, intracranial injection of NCAM antibodies have been shown to inhibit consolidation of a passive avoidance task, when administered in a discrete time window after the learning session. This has been shown in rats (Doyle et al., 1992a; Alexinsky et al., 1997) as well as in chicks (Scholey et al., 1993). In rats, injection of antibodies in the six to eight hours posttraining period impaired establishment of long-term memory for a passive avoidance response, when tested at the 48-h recall time. In chicks, amnesia for a passive avoidance response was observed when the injection of NCAM antibodies was performed in the five to eight hours posttraining period, but only when the recall was tested 24 h following training. In addition, it has been shown that NCAM is synthesized, among with other glycoproteins, in a glycoprotein-dependent phase of establishment of long-term memory occurring six to eight hours after the learning session (Scholey et al., 1993; Mileusnic et al., 1995). Second, NCAM knock-out mice have shown deficiency in spatial learning when tested in a Morris water maze (Cremer et al., 1994). However, it is not known whether this deficit in learning is due to defects in plasticity mechanisms or developmental defects. Third, changes in the posttranslational modification of NCAM have been observed following learning. In the adult brain, PSA-NCAM is only expressed in restricted areas including the olfactory system and the dentate gyrus in the hippocampal formation (Fig. 3), areas thought to be characterized by a high level of structural remodeling in the adult (Miragall et al., 1988; Seki and Arai, 1991). An increased degree of polysialylation of NCAM has been demonstrated in granule cells of the dentate gyrus in the adult rat after learning of a passive avoidance response (Doyle et al., 1992b; Fox et al., 1995) and after spatial learning in a Morris water maze (Murphy et al., 1996). Increased polysialylation of NCAM has, likewise, been observed in the entorhinal cortex after Morris water maze learning (O’Connell et al., 1997) suggesting that PSA-NCAM expression is activated in a cortico-hippocampal pathway follow-
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FIG. 3. (A) Immunohistochemistry showing PSA expression in the hippocampal formation in P80 rat brain. (B, C) PSA expression in the granule cell layer of the dentate gyrus (DG) and in the mossy fibers (mf) 0 h (B) and 12 h (C) after water-maze learning. (A.G. Foley, L.C.B. Rønn, and C.M. Regan, unpublished observations).
ing learning. The increase in polysialylation was observed only in the 10 –12-h posttraining period for both types of learning, and was probably due to polysialylation of NCAM on preexisting neurons rather than to increased neurogenesis (Fox et al., 1995). This increased polysialylation of NCAM has been shown to affect primarily one isoform of NCAM, NCAM180 (Doyle et al., 1992b). Because an increase in PSA-NCAM is thought to decrease cell adhesion and to stimulate neurite outgrowth, polysialylation of NCAM may allow structural remodeling of neuronal connections during establishment of long-term memory (Regan and Fox, 1995). Furthermore, impaired acquisition and retention of spatial memory has been observed in the rat following enzymatic removal of PSA with endo-neuraminidase (Becker et al., 1996). Interestingly, the expression of PSA-NCAM can be rapidly modulated by neuronal activity (Kiss et al., 1994; Muller et al., 1996; Rafuse and Landmesser, 1996). Finally, studies in the marine mollusc Aplysia california provide additional evidence for a role for NCAM in learning and memory. In vitro, learning-related formation of new synaptic connections is associated with downregulation of the Aplysia cell adhesion molecule, apCAM (Bailey et al., 1992; Mayford et al., 1992; Zhu et al., 1995), which probably is an Aplysia NCAM homologue. Presumably, this downregulation is a result of both decreased synthesis and increased endocytosis (Bailey et al., 1992; Mayford et al., 1992). The downregulation of apCAM may destabilize adhesive contacts between neurons in synapses, and thereby lead to a redistribution of membrane component and allow new synaptic connections to form. Furthermore, it has been shown that apCAM antibodies inhibit induction of long-term changes in synaptic structures. In Drosophila, another NCAM homologue, Fasciclin II, is crucial for the formation and stabilization of synapses in the neuromuscular junction (Schuster et al., 1996 a, b). In vitro, the role of NCAM in synaptic plasticity has been studied in hippocampal slice preparations. In this system, locally applied NCAM antibodies have been shown to inhibit the generation of long-term potentiation (LTP) in the CA1 region (Lu¨thi et al., 1994; Rønn et al., 1995). The effect is manifested within seconds after high-frequency stimulation, raising the possibility that NCAM may influence the phase during or immediately after LTP-induction. Such an action may depend on the presence of PSA-NCAM as the removal of PSA with endo-N prevents the induction of LTP in the acute hippocampal slice preparation (Becker et al., 1996)
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and in organotypic slice cultures (Muller et al., 1996). In slices from NCAM-deficient mice a strong inhibition of LTP induction has been observed when compared to slices from wild-type mice. In organotypic slice cultures from NCAM-deficient mice, inhibition of LTP was likewise observed (Muller et al., 1996), although in this case the effect was manifested as a slowly decaying LTP, suggesting that under these circumstances, the lack of NCAM affected early maintenance of LTP. Following induction of LTP in vivo, an increase in extracellular NCAM has been reported (Fazeli et al., 1994), possibly as the result of increased proteolytic activity two to three hours following LTP induction. TOWARDS AN UNDERSTANDING OF NCAM STRUCTURE AND FUNCTION In recent years, a number of studies have contributed significantly to the understanding of the structure and function of NCAM. As the structure of individual domains of NCAM is being elucidated, a better understanding of the binding properties of NCAM will undoubtedly result. In vitro studies have shown that cell adhesion molecules including NCAM not only function as cell glues; rather, ligation of NCAM activates intracellular signaling pathways, which in turn, influences behavioral responses of neurons such as neurite extension. In addition to this outside-in signaling, neuronal activity may affect polysialylation of NCAM, thereby effecting an inside-out signaling with important impact on the adhesive properties of the cell. By interfering with normal NCAM function it has been shown that NCAM is important not only during brain development but also in synaptic plasticity in the adult brain associated with regeneration and learning, but the mechanisms are poorly understood. It, therefore, remains to be determined how the signaling and adhesive functions of NCAM is involved in neuronal development and plasticity in vivo. REFERENCES ACHESON, A., SUNSHINE, J.L., and RUTISHAUSER, U. NCAM polysialic acid can regulate both cell– cell and cell–substrate interactions. J. Cell Biol. 114, 143–153, 1991. ALEXINSKY, T., PRZYBYSLAWSKI, J., MILEUSNIC, R., ROSE, S.P., and SARA, S.J. Antibody to day-old chick brain glycoprotein produces amnesia in adult rats. Neurobiol. Learn. Mem. 67, 14 –20, 1997. ANGATA, K., NAKAYAMA, J., FREDETTE, B., CHONG, K., RANSCHT, B., and FUKUDA, M. Human STX polysialyltransferase forms the embryonic form of the neural cell adhesion molecule. Tissue-specific expression, neurite outgrowth, and chromosomal localization in comparison with another polysialyltransferase, PST. J. Biol. Chem. 272, 7182–7190, 1997. BAILEY, C.H., CHEN, M., KELLER, F., and KANDEL, E.R. Serotonin-mediated endocytosis of apCAM: An early step of learning-related synaptic growth in Aplysia. Science 256, 645– 649, 1992. BECKER, C.G., ARTOLA, A., GERARDY-SCHAHN, R., BECKER, T., WELZL, H., and SCHACHNER, M. The polysialic acid modification of the neural cell adhesion molecule is involved in spatial learning and hippocampal long-term potentiation. J. Neurosci. Res. 45, 143–152, 1996. BEGGS, H.E., SORIANO, P., and MANESS, P.F. NCAM-dependent neurite outgrowth is inhibited in neurons from Fyn-minus mice. J. Cell Biol. 127, 825– 833, 1994. BEGGS, H.E., BARAGONA, S.C., HEMPERLY, J.J., and MANESS, P.F. NCAM140 interacts with the focal adhesion kinase p125fak and the SRC-related tyrosine kinase p59fyn. J. Biol. Chem. 272, 8310 – 8319, 1997. BOCK, E., EDVARDSEN, K., GIBSON, A., LINNEMANN, D., LYLES, J.M., and NYBROE, O. Characterization of soluble forms of NCAM. FEBS Lett. 225, 33–36, 1987. ¨ MMENDORF, T. and RATHJEN, F.G. Cell adhesion molecules 1: Immunoglobulin superfamily. Prot. Profile 2, BRU 963–1108, 1995. COLE, G.J., LOEWY, A., and GLASER, L. Neuronal cell– cell adhesion depends on interactions of N-CAM with heparin-like molecules. Nature 320, 445– 447, 1986. CREMER, H., LANGE, R., CHRISTOPH, A., PLOMANN, M., VOPPER, G., ROES, J., BROWN, R., BALDWIN, S.,
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KRAEMER, P., SCHEFF, S., BAERHELS, D., RAJEWSKY, K., and WILLE, W. Inactivation of the N-CAM gene in mice results in size reduction of the olfactory bulb and deficiets in spatial learning. Nature 367, 455– 459, 1994. CREMER, H., CHAZAL, G., GORIDIS, C., and REPRESA, A. NCAM is essential for axonal growth and fasciculation in the hippocampus. Mol. Cell. Neurosci. 8, 323–335, 1997. DASTON, M.M., BASTMEYER, M., RUTISHAUSER, U., and O’LEARY, D.D. Spatially restricted increase in polysialic acid enhances corticospinal axon branching related to target recognition and innervation. J. Neurosci. 16, 5488 –5497, 1996. DOHERTY, P., ASHTON, S.V., MOORE, S.E., and WALSH, F.S. Morphoregulatory activities of NCAM and N-cadherin can be accounted for by G protein-dependent activation of L- and N-type neuronal calcium-channels. Cell 67, 21–33, 1991. DOHERTY, P., MOOLENAAR, C.E., ASHTON, S.V., MICHALIDES, R.J., and WALSH, F.S. The VASE exon downregulates the neurite growth-promoting activity of NCAM 140. Nature 356, 791–793, 1992. DOHERTY, P. and WALSH, F.S. CAM-FGF receptor interactions: A model for axonal growth. Mol. Cell. Neurosci. 8, 99 –111, 1996. DOYLE, E., NOLAN, P.M., BELL, R., and REGAN, C.M. Intraventricular infusions of anti-neural cell adhesion molecules in a discrete posttraining period impair consolidation of a passive avoidance response in the rat. J. Neurochem. 59, 1570 –1573, 1992a. DOYLE, E., NOLAN, P.M., BELL, R., and REGAN, C.M. Hippocampal NCAM180 transiently increases sialylation during the aquisition and consolidation of a passive avoidance response in the adult rat. J. Neurosci. Res. 31, 513–523, 1992b. ECKHARDT, M., MUHLENHOFF, M., BETHE, A., KOOPMAN, J., and FROSCH, M. Molecular characterization of eukaryotic polysialyltransferase-1. Nature 373, 715–718, 1995. EDELMAN, G.M. and CHUONG, C.M. Embryonic to adult conversion of neural cell adhesion molecules in normal and staggerer mice. Proc. Natl. Acad. Sci. USA 79, 7036 –7040, 1982. EDELMANN, G.M. and CROSSIN, K.L. Cell adhesion molecules: Implications for a molecular histology. Annu. Rev. Biochem. 60, 155–190, 1991. FAZELI, M.S., BREEN, K., ERRINGTON, M.L., and BLISS, T.V.P. Increase in extracellular NCAM and amyloid precursor protein following induction of long-term potentiation in the dentate gyrus of anaesthetized rats. Neurosci. Lett. 169, 77– 80, 1994. FIELDS, R.D. and ITOH, K. Neural cell adhesion molecule in activity-dependent development and synaptic plasticity. Trends Neurosci. 19, 473– 480, 1996. FOX, G.B., O’CONNELL, A.W., MURPHY, K.J., and REGAN, C.M. Memory consolidation induces a transient and time-dependent increase in the frequency of neural cell adhesion molecule polysialylated cells in the adult rat hippocampus. J. Neurochem. 65, 2796 –2799, 1995. FRASER, S.E., MURRAY, B.A., CHUONG, C.M., and EDELMAN, G.M. Alteration of the retinotectal map in Xenopus by antibodies to neural cell adhesion molecules. Proc. Natl. Acad. Sci. USA 81, 4222– 4226, 1984. GEGELASHVILI, G., ANDERSSON, A.M., SCHOUSBOE, A., and BOCK, E. Cyclic AMP regulates NCAM expression and phosphorylation in cultured mouse astrocytes. Eur. J. Cell Biol. 62, 343–351, 1993. GRUMET, M., FLACCUS, A., and MARGOLIS, R.U. Functional characterization of chondroitin sulfate proteoglycans of brain: Interactions with neurons and neural cell adhesion molecules. J. Cell Biol. 120, 815– 824, 1993. HALL, H., WALSH, F.S., and DOHERTY, P. A role for the FGF receptor in the axonal growth response stimulated by cell adhesion molecules. Cell Adhes. Commun. 3, 441– 450, 1996. HOLDEN, H.M., ITO, M., HARTSHORNE, D.J., and RAYMENT, I. X-ray structure determination of telokin, the C-terminal domain of myosin light chain kinase, at 2.8 A resolution. J. Mol. Biol. 227, 840 – 851, 1992. HORSTKORTE, R., SCHACHNER, M., MAGYAR, J.P., VORHERR, T., and SCHMITZ, B. The fourth immunoglobulin-like domain of NCAM contains a carbohydrate recognition domain for oligomannosidic glycans implicated in association with L1 and neurite outgrowth. J. Cell Biol. 121, 1409 –1421, 1993. JOLIOT, A.H., TRILLER, A., VOLOVITCH, M., PERNELLE, C., and PROCHIANTZ, A. Alpha-2,8-Polysialic acid is the neuronal surface receptor of antennapedia homeobox peptide. New Biol. 3, 1121–1134, 1991. KADMON, G., KOWITZ, A., ALTEVOGT, P., and SCHACHNER, M. Functional cooperation between the neural adhesion molecules L1 and N-CAM is carbohydrate dependent. J. Cell Biol. 110, 209 –218, 1990a. KADMON, G., KOWITZ, A., ALTEVOGT, P., and SCHACHNER, M. The neural cell adhesion molecule N-CAM enhances L1-dependent cell-cell interactions. J. Cell Biol. 110, 193–208, 1990b. KISELYOV, V.V., BEREZIN, V., MAAR, T.E., SOROKA, V., EDVARDSEN, K., SCHOUSBOE, A., and BOCK, E. The first Ig-like NCAM domain is involved in double reciprocal interaction with the second Ig-like NCAM domain and in heparin binding. J. Biol. Chem. 272, 10125–10134, 1996.
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KISS, J.Z., WANG, C., OLIVE, S., ROUGON, G., LANG, J., BAETENS, D., and HARRY, D. Activity-dependent mobilization of the adhesion molecule polysialic NCAM to the cell surface of neurons and endocrine cells. EMBO J. 13, 5284 –5292, 1994. KROG, L. and BOCK, E. Glycosylation of neural cell adhesion molecules of the immunoglobulin superfamily. APMIS Suppl. 27, 53–70, 1992. LANDMESSER, L., DAHM, L., TANG, J.C., and RUTISHAUSER, U. Polysialic acid as a regulator of intramuscular nerve branching during embryonic development. Neuron 4, 655– 667, 1990. LINNEMANN, D., LYLES, J.M., and BOCK, E. A developmental study of the biosynthesis of the neural cell adhesion molecule. Dev. Neurosci. 7, 230 –238, 1985. ¨ THI, A., LAURENT, J.P., FIGUROV, A., MULLER, D., and SCHACHNER, M. Hippocampal long-term potentiLU ation and neural cell adhesion molecules L1 and NCAM. Nature 372, 777–779, 1994. MARTERSTECK, C.M., KEDERSHA, N.L., DRAPP, D.A., TSUI, T.G., and COLLEY, K.J. Unique alpha 2, 8-polysialylated glycoproteins in breast cancer and leukemia cells. Glycobiology 6, 289 –301, 1996. MAYFORD, M., BARZILAI, A., KELLER, F., SCHACHER, S., and KANDEL, E.R. Modulation of an NCAM-related adhesion molecule with long-term synaptic plasticity in Aplysia. Science 256, 638 – 644, 1992. MILEUSNIC, R., ROSE, S.P., LANCASHIRE, C., and BULLOCK, S. Characterisation of antibodies specific for chick brain neural cell adhesion molecules which cause amnesia for a passive avoidance task. J. Neurochem. 64, 2598 –2606, 1995. MILEV, P., MAUREL, P., HARING, M., MARGOLIS, R.K., and MARGOLIS, R.U. TAG-1/axonin-1 is a high-affinity ligand of neurocan, phosphacan/protein-tyrosine phosphatase-zeta/beta, and N-CAM. J. Biol. Chem. 271, 15716 – 15723, 1996. MIRAGALL, F., KADMON, G., HUSMANN, M., and SCHACHNER, M. Expression of cell adhesion molecules in the olfactory system of the adult mouse: Presence of the embryonic form of N-CAM. Dev. Biol. 129, 516 –531, 1988. ¨ HLENHOFF, M., ECKHARDT, M., BETHE, A., FROSCH, M., and GERARDY-SCHAHN, R. Autocatalytic MU polysialylation of polysialyltransferase-1. EMBO J. 15, 6943– 6950, 1996. MULLER, D., WANG, C., SKIBO, G., TONI, N., CREMER, H., CALAORA, V., ROUGON, G., and KISS, J.Z. PSA-NCAM is required for activity-induced synaptic plasticity. Neuron 17, 413– 422, 1996. MURPHY, K.J., O’CONNELL, A.W., and REGAN, C.M. Repetitive and transient increases in hippocampal neural cell adhesion molecule polysialylation state following multitrial spatial training. J. Neurochem. 67, 1268 –1274, 1996. MURRAY, B.A., HEMPERLY, J.J., PREDIGER, E.A., EDELMAN, G.M., and CUNNINGHAM, B.A. Alternatively spliced mRNAs code for different polypeptide chains of the chicken neural cell adhesion molecule (N-CAM). J. Cell Biol. 102, 189 –193, 1986. NAKAYAMA, J., FUKUDA, M.N., FREDETTE, B., RANSCHT, B., and FUKUDA, M. Expression cloning of a human polysialyltransferase that forms the polysialylated neural cell adhesion molecule present in emryonic brain. Proc. Natl. Acad. Sci. USA 922, 7031–7035, 1995. NAKAYAMA, J. and FUKUDA, M. A human polysialyltransferase directs in vitro synthesis of polysialic acid. J. Biol. Chem. 271, 1829 –1832, 1996. NOBLE, M., ALBRECHTSEN, M., MOLLER, C., LYLES, J., BOCK, E., GORIDIS, C., and RUTISHAUSER, U. Glial cells express N-CAM/D2-CAM-like polypeptides in vitro. Nature 316, 725–728, 1985. O’CONNELL, A.W., FOX, G.B., BARRY, T., FOLEY, A.G., MURPHY, K.J., FICHERA, G., KELLY, J., and REGAN, C.M. Spatial learning activates neural cell adhesion molecule polysialylation in a cortico-hippocampal pathway within the medial temporal lobe. J. Neurochem. 68, 2538 –2546, 1997. OLSEN, M., KROG, L., EDVARDSEN, K., SKOVGAARD, L.T., and BOCK, E. Intact transmembrane isoforms of the neural cell adhesion molecule are released from the plasma membrane. Biochem. J. 295, 833– 840, 1993. ONO, K., TOMASIEWICZ, H., MAGNUSON, T., and RUTISHAUSER, U. N-CAM mutation inhibits tangential neuronal migration and is phenocopied by enzymatic removal of polysialic acid. Neuron 13, 595– 609, 1994. PAOLONI-GIACOBINO, A., CHEN, H., and ANTONARAKIS, S.E. Cloning of a novel human neural cell adhesion molecule gene (NCAM2) that maps to chromosome region 21q21 and is potentially involved in Down syndrome. Genomics 43, 43–51, 1997. PFUHL, M. and PASTORE, A. Tertiary structure of an immunoglobulin-like domain from the giant muscle protein titin: A new member of the I set. Structure 3, 391– 401, 1995. PHILLIPS, G.R., KRUSHEL, L.A., and CROSSIN, K.L. Developmental expression of two rat sialyltransferases that modify the neural cell adhesion molecule, N-CAM. Dev. Brain Res. 102, 143–155, 1997. PROBSTMEIER, R., KUHN, K., and SCHACHNER, M. Binding properties of the neural cell adhesion molecule to different components of the extracellular matrix. J. Neurochem. 53, 1794 –1801, 1989.
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RABINOWITZ, J.E., RUTISHAUSER, U., and MAGNUSON, T. Targeted mutation of Ncam to produce a secreted molecule results in a dominant embryonic lethality. Proc. Natl. Acad. Sci. USA 93, 6421– 6424, 1996. RAFUSE, V.F. and LANDMESSER, L. Contractile activity regulates isoform expression and polysialylation of NCAM in cultured myotubes: Involvement of Ca21 and protein kinase C. J. Cell Biol. 132, 969 –983, 1996. RANHEIM, T.S., EDELMAN, G.M., and CUNNINGHAM, B.A. Homophilic adhesion mediated by the neural cell adhesion molecule involves multiple immunoglobulin domains. Proc. Natl. Acad. Sci. USA 93, 4071– 4075, 1996. RAO, Y., WU, X.F., GARIEPY, J., RUTISHAUSER, U., and SIU, C.H. Identification of a peptide sequence involved in homophilic binding in the neural cell adhesion molecule NCAM. J. Cell Biol. 118, 937–949, 1992. RAO, Y., WU, X.F., YIP, P., GARIEPY, J., and SIU, C.H. Structural characterization of a homophilic binding site in the neural cell adhesion molecule. J. Biol. Chem. 268, 20630 –20638, 1993. RAO, Y., ZHAO, X., and SIU, C.H. Mechanism of homophilic binding mediated by the neural cell adhesion molecule NCAM. Evidence for isologous interaction. J. Biol. Chem. 269, 27540 –27548, 1994. REGAN, C.M. and FOX, G.B. Polysialylation as a regulator of neural plasticity in rodent learning and aging. Neurochem. Res. 20, 593–598, 1995. RØNN, L.C.B., BOCK, E., LINNEMANN, D., and JAHNSEN, H. NCAM-antibodies modulate induction of long-term potentiation in rat hippocampal CA1. Brain Res. 677, 145–151, 1995. ROUGON, G., DEAGOSTINI-BAZIN, H., HIRN, M., and GORIDIS, C. Tissue- and developmental stage-specific forms of a neural cell surface antigen linked to differences in glycosylation of a common polypeptide. EMBO J. 1, 1239 –1244, 1982. ROUGON, G. Structure, metabolism and cell biology of polysialic acids. Eur. J. Cell Biol. 61, 197–207, 1993. RUTISHAUSER, U. and LANDMESSER, L. Polysialic acid in the vertebrate nervous system: A promoter of plasticity in cell– cell interactions. Trends Neurosci. 19, 422– 427, 1996. SAFFELL, J.L., WILLIAMS, E.J., MASON, I.J., WALSH, F.S., and DOHERTY, P. Expression of a dominant negative FGF receptor inhibits axonal growth and FGF receptor phosphorylation stimulated by CAMs. Neuron 18, 231–242, 1997. SCHEIDEGGER, E.P., STERNBERG, L.R., ROTH, J., and LOWE, J.B. A human STX cDNA confers polysialic acid expression in mammalian cells. J. Biol. Chem. 270, 22685–22688, 1995. SCHOLEY, A.B., ROSE, S.P.R., ZAMANI, M.R., BOCK, E., and SCHACHNER, M. A role for the neural cell adhesion molecule (NCAM) in a late, consolidating phase of glycoprotein synthesis 6 hours following passive avoidance training of the young chick. Neuroscience 55, 499 –509, 1993. SCHUCH, U., LOHSE, M.J., and SCHACHNER, M. Neural cell adhesion molecules influence second messenger systems. Neuron 3, 13–20, 1989. SCHUSTER, C.M., DAVIS, G.W., FETTER, R.D., and GOODMAN, C.S. Genetic dissection of structural and functional components of synaptic plasticity. I. Fasciclin II controls synaptic stabilization and growth. Neuron 17, 641– 654, 1996a. SCHUSTER, C.M., DAWIS, G.W., FETTER, R.D., and GOODMAN, C.S. Genetic dissection of structural and functional components of synaptic plasticity. II. Fasciclin II controls presynaptic structural plasticity. Neuron 17, 655– 667, 1996b. SEKI, T. and ARAI, Y. The persistent expression of a highly sialylated NCAM in the dentate gyrus of the adult rat. Neurosci. Res. 12, 503–513, 1991. SMALL, S.J., HAINES, S.L., and AKESON, R.A. Polypeptide variation in an N-CAM extracellular immunoglobulinlike fold is developmentally regulated through alternative splicing. Neuron 1, 1007–1017, 1988. SMALL, S.J. and AKESON, R. Expression of the unique NCAM VASE exon is independently regulated in distinct tissues during development. J. Cell Biol. 111, 2089 –2096, 1990. SORKIN, B.C., HOFFMAN, S., EDELMAN, G.M., and CUNNINGHAM, B.A. Sulfation and phosphorylation of the neural cell adhesion molecule, N-CAM. Science 225, 1476 –1478, 1984. STORMS, S.D., KIM, A.C., TRAN, B.T., COLE, G.J., and MURRAY, B.A. NCAM-mediated adhesion of transfected cells to agrin. Cell Adhes. Commun. 3, 497–509, 1996. TANG, J., RUTISHAUSER, U., and LANDMESSER, L. Polysialic acid regulates growth cone behavior during sorting of motor axons in the plexus region. Neuron 13, 405– 414, 1994. THOMSEN, N.K., SOROKA, V., JENSEN, P.H., BEREZIN, V., KISELYOV, V.V., and BOCK, E. The threedimensional structure of the first domain of neural cell adhesion molecule. Nat. Struct. Biol. 3, 581–585, 1996. TOMASIEWICZ, H., ONO, K., YEE, D., THOMPSON, C., GORIDIS, C., RUTISHAUSER, U., and MAGNUSON, T. Genetic deletion of a neural cell adhesion molecule variant (N-CAM-180) produces distinct defects in the central nervous system. Neuron 11, 1163–1174, 1993.
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VON BOHLEN UND HALBACH, F., TAYLOR, J., and SCHACHNER, M. Cell type specific effects of the neural cell adhesion molecules L1 and N-CAM on diverse second messenger systems. Eur. J. Neurosci. 4, 896 –909, 1992. WALSH, F.S. and DICKSON, G. Generation of multiple N-CAM polypeptides from a single gene. Bioessays 11, 83– 88, 1989. WANG, J.H., PEPINSKY, R.B., STEHLE, T., LIU, J.H., KARPUSAS, M., and BROWNING, B. The crystal structure of an N-terminal two-domain fragment of vascular cell adhesion molecule 1 (VCAM-1): A cyclic peptide based on the domain 1 C-D loop can inhibit VCAM-1-alpha 4 integrin interaction. Proc. Natl. Acad. Sci. USA 92, 5714 –5718, 1995. WILLIAMS, A.F. and BARCLAY, A.N. The immunoglobulin superfamily—Domains for cell surface recognition. Annu. Rev. Immunol. 6, 381– 405, 1988. WILLIAMS, D.K., GANNON-MURAKAMI, L., ROUGON, G., and UDIN, S.B. Polysialylated neural cell adhesion molecule and plasticity of ipsilateral connections in Xenopus tectum. Neuroscience 70, 277–285, 1996. WILLIAMS, E.J., FURNESS, J., WALSH, F.S., and DOHERTY, P. Activation of the FGF receptor underlies neurite outgrowth stimulated by L1, NCAM, and N-cadherin. Neuron 13, 583–594, 1994. YIN, X., WATANABE, M., and RUTISHAUSER, U. Effect of polysialic acid on the behavior of retinal ganglion cell axons during growth into the optic tract and tectum. Development 121, 3439 –3446, 1995. YOSHIDA, Y., KOJIMA, N., KUROSAWA, N., HAMAMOTO, T., and TSUJI, S. Molecular cloning of Sia alpha 2,3Gal beta 1,4GlcNAc alpha 2,8-sialyltransferase from mouse brain. J. Biol. Chem. 270, 14628 –14633, 1995. ZHU, H., WU, F., and SCHACHER, S. Changes in expression and distribution of Aplysia cell adhesion molecules can influence synapse formation and elimination in vitro. J. Neurosci. 15, 4173– 4183, 1995. ZUBER, C., LACKIE, P.M., CATTERALL, W.A., and ROTH, J. Polysialic acid is associated with sodium channels and the neural cell adhesion molecule N-CAM in adult rat brain. J. Biol. Chem. 267, 9965–9971, 1992.
PII S0531-5565(98)00040-0
THE NEURAL CELL ADHESION MOLECULE (NCAM) IN DEVELOPMENT AND PLASTICITY OF THE NERVOUS SYSTEM
L.C.B. RØNN, B.P. HARTZ and E. BOCK The Protein Laboratory, Institute for Molecular Pathology, University of Copenhagen, Denmark
Abstract—The neural cell adhesion molecule (NCAM) is a member of the immunoglobulin superfamily and is strongly expressed in the nervous system. NCAM is found in three major forms, of which two—NCAM-140 and NCAM-180 —are transmembrane proteins, while the third—NCAM-120 —is attached to the membrane via a glycosylphosphatidyl inositol anchor. In addition, soluble NCAM forms exist in brain, cerebrospinal fluid, and plasma. NCAM mediates cell adhesion through homophilic as well as through heterophilic interactions. Following NCAM binding, transmembrane signalling is believed to be activated, resulting in increased intracellular calcium. By mediating cell adhesion to other cells and to the extracellular matrix and by activating intracellular signaling pathways, NCAM influences cell migration, neurite extension, and fasciculation, and possibly formation of synapses in the brain. From studies on NCAM knock-out mice, NCAM have been shown to be crucial for the formation of the olfactory bulb and the mossy fiber system in the hippocampus. In addition, NCAM is important for neuronal plasticity in the adult brain associated with learning and regeneration. © 1998 Elsevier Science Inc. Key Words: NCAM, synaptic plasticity, cell adhesion, neurite extension, learning, regeneration, signal transduction, long-term potentiation
STRUCTURE OF THE NCAM PROTEIN THE NEURAL CELL adhesion molecule (NCAM) belongs to the cell adhesion molecules of the immunoglobulin (Ig) superfamily (IgSF) characterized by the Ig domain (Williams and Barclay, 1988; Bru¨mmendorf and Rathjen, 1995). The Ig domain contains approximately 100 amino acids forming two b-sheets. Based on structure, Ig domains can be classified to the constant type 1 (C1-set), the constant type 2 (C2-set), the variable type (V-set), or the intermediate set (I-set) of Ig domains, the I-set being a recently characterized structure intermediate between the V- and the C-forms. The N-terminal Ig1 of NCAM was recently shown to belong to the I-set by NMR (Thomsen et al., 1996), together with the M5 domain of titin (Pfuhl and Pastore, 1995), telokin Correspondence to: Lars Christian B. Rønn, The Protein Laboratory, Institute for Molecular Pathology, Panum Institute Bld. 6.2., Blegdamsvej 3, DK-2200, Copenhagen N, Denmark; Fax: 145-35-36-01-16; E-mail: [email protected] (Received 1 May 1998; Accepted 28 May 1998) 853
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FIG. 1. (A) NCAM structure. In brain, NCAM is found in three major forms that are either transmembrane (NCAM-180, NCAM-140) or attached to the membrane via a glycosylphosphatidyl inositol (GPI) anchor (NCAM-120). In addition, soluble truncated or shedded forms of NCAM (NCAMs1, 2, and 3) exist. (B) The three major forms of NCAM are generated by alternative splicing. Exon 15 encodes a signal for GPI linkage. Use of exon 15 results in the expression of NCAM-120 without transmembrane and cytoplasmic domains. In contrast, omitting exon 15 results in the expression of the transmembrane forms NCAM-140 and NCAM-180. The cytoplasmic part of NCAM-180 is larger than that of NCAM-140, due to the use of exon 18 in mRNAs encoding this isoform. Further diversity of the mRNA species results from the alternative splicing of the exons a, b, c, AAG, and VASE. In addition, NCAM is modified posttranslationally, particularly important being the addition of polysialic acid (PSA) to the fifth Ig domain.
(Holden et al., 1992), and the first domain of VCAM (Wang et al., 1995). In addition to these, a number of other domains of the IgSF has been predicted, based on conservation of structurally important residues, to be of the I-set type including the second and the third Ig domains of NCAM, the third and the fifth Ig domains of mouse L1, the third Ig domain of mouse contactin, and the fifth Ig domain of Drosophila neuroglian. Indeed, the I-set structure appears to be characteristic for neuronal cell adhesion molecules (Thomsen et al., 1996). Three major forms of NCAM generated by alternative splicing are found (Murray et al., 1986; Walsh and Dickson, 1989). In all three forms, the extracellular portion of the protein contains five Ig domains and two fibronectin homology (FnIII) domains (Fig. 1). One NCAM form is attached to the membrane by a glycosylphosphatidyl inositol (GPI) anchor (NCAM-120). The two other major forms contain a transmembrane domain and a short (NCAM-140) or a longer (NCAM-180) cytoplasmic domain. In addition, alternative splicing may generate further variability by the optional insertion of four exons, a, b, c, and AAG between exons 12 and 13 encoding the stretch between the two FnIII domains and by the insertion of the so-called “variable domain alternatively spliced exon” (VASE) between exons 7 and 8 encoding the fourth Ig domain (Small et
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al., 1988). All NCAM forms are encoded by a single gene located in chromosome 9 in mouse, chromosome 8 in the rat, and chromosome 11 in humans. Recently, a transmembrane NCAMlike molecule, NCAM2, was cloned from a human fetal brain cDNA library (Paoloni-Giacobino et al., 1997). The NCAM2 gene was located to the human chromosome 21, but the function of NCAM2 remains to be determined. In addition to structural variations in the NCAM transcripts modulated by alternative splicing, the molecule is submitted to a series of posttranslational modifications. Thus, the NCAM protein can be modified by phosphorylation, sulphation, and glycosylation (Sorkin et al., 1984; Linnemann et al., 1985; Krog and Bock, 1992; Gegelashvili et al., 1993). Notably, fractions of the NCAM proteins carry the L2/HNK-1 carbohydrate epitope and/or polysialic acid (PSA). The L2/HNK-1 epitope is a sulphated glucoronyl residue recognized by the monoclonal antibodies L2 and HNK-1, and the epitope is supposed to be functionally important, as the antibodies have been reported to interfere with cell adhesion. The epitope is shared by a number of neuronal cell adhesion molecules including L1 and myelin associated glycoprotein (MAG) as well as by other glycoproteins and glycolipids. In contrast, NCAM is responsible for the majority of PSA expressed in the brain. Thus, in NCAM knock-out mice PSA expression is reduced by approximately 85% (Cremer et al., 1994). However, it has been reported that PSA is also expressed by polysialyltransferase (Mu¨hlenhoff et al., 1996), one of the two enzymes known to synthesize the PSA moiety on NCAM, as well as by the a-subunit of a sodium channel (Zuber et al., 1992), and by an intracellular protein of certain cancer-cells (Martersteck et al., 1996). PSA consists of long homopolymers of a2– 8-linked N-acetyl neuraminic residues attached to N-linked carbohydrates on the fifth Ig domain of NCAM (Zuber et al., 1992; Rougon, 1993). PSA-NCAM can be synthesized by two polysialyltransferases (Eckhardt et al., 1995; Nakayama et al., 1995; Scheidegger et al., 1995; Yoshida et al., 1995; Nakayama and Fukuda, 1996), polysialyltransferase-1 (PST) and sialyltransferase-X (STX), the expression of which are differentially regulated in a tissue-specific manner (Angata et al., 1997; Phillips et al., 1997). PSA-NCAM is widely expressed in the embryonic and early postnatal brain; hence, the term “embryonic NCAM” (eNCAM), constituting up to 30% of the NCAM protein by weight. The expression decreases to approximately 10% by weight in the adult brain (Edelman and Chuong, 1982; Rougon et al., 1982). Therefore, embryonic NCAM appears as a broad smeared band in Western blotting due to the different lengths of the attached PSA chains, while distinct bands are seen in Western blottings of NCAM from adult brain. Concomitant with the decreased PSA-NCAM expression during development, the fraction of NCAM molecules containing the alternatively spliced VASE exon increases from a few percent in the embryonic brain to approximately 50% in the adult brain (Small and Akeson, 1990). In the brain, NCAM is primarily expressed by neurons. However, low amounts of NCAM is also expressed by glial cells (Noble et al., 1985). In addition to membrane-attached NCAM, soluble NCAM forms exist in the cerebrospinal fluid and in plasma (Bock et al., 1987; Olsen et al., 1993). The main form of soluble NCAM (NCAM-s3) appears as a double band in Western blotting with an Mr of 110/115 representing the extracellular part of NCAM-120 released by phospholipase activity as well as the extracellular part of all NCAM forms released by extracellular proteolysis. In addition, shedded NCAMs with Mrs of approximately 140 (NCAM-s2) and 180 (NCAM-s1) exist. These forms are recognized by antibodies against cytoplasmic epitopes of NCAM (Olsen et al., 1993). A fraction of these latter forms are associated with lipids.
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FIG. 2. Hypothetical regulation of homophilic NCAM binding by polysialylation. (A) Interaction between Ig1- and Ig2-mediated homophilic binding of PSA-NCAM. (B) Reciprocal interaction between all five Ig domains of NCAM in the absence of PSA.
NCAM FUNCTIONS: CELL ADHESION AND SIGNAL TRANSDUCTION The classical role of NCAM is to mediate cell adhesion through a homophilic action, NCAM on one cell binding to NCAM on another. The site(s) of homophilic NCAM binding is controversial, and has been proposed to be mediated by a reciprocal interaction between the third Ig domain of two NCAM molecules on opposing membranes (Rao et al., 1992, 1993, 1994), or by a reciprocal interaction between all five Ig domains, the fifth Ig domain binding the first Ig domain, the second Ig domain binding the fourth Ig domain, and the third Ig domain binding the third Ig domain (Ranheim et al., 1996). Recently, the nature of the homophilic NCAM binding was addressed by investigating the binding between individual NCAM domains by plasmon surface resonance analysis. Here, binding was demonstrated between the first and the second Ig domains, suggesting that a double reciprocal interaction between these two domains mediates homophilic NCAM binding (Kiselyov et al., 1996). It is possible that several mechanisms of homophilic NCAM binding exist, the preferred binding conformation being dictated by the glycosylation and/or alternative splicing of NCAM, for example homophilic binding of mature NCAM forms without extensive polysialylation may involve all five Ig domains while the presence of PSA on the fifth Ig domain in embryonic NCAM may favor interaction of the first and the second Ig domains by sterically preventing interactions involving the fifth and the fourth Ig domains (Fig. 2). Whatever the mechanisms, it is believed that homophilic NCAM binding activates signal transduction. In vitro, NCAM or NCAM antibodies have been shown to result in increased intracellular calcium in certain neuronal cells (Schuch et al., 1989; von Bohlen und Halbach et al., 1992). Moreover, homophilic NCAM interactions stimulate neurite extension, apparently by activating a signal transduction pathway resulting in a calcium influx through voltage-dependent calcium channels (Doherty et al., 1991). It has been proposed that NCAM binds to the fibroblast growth factor receptor (FGF-R), thereby activating intracellular signaling (Williams et al., 1994; Saffell et al., 1997). The FGF-Rs contain a
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so-called CAM-homology domain (CHD) with three adjacent sequences with homology to sequences in NCAM, L1 and N-cadherin, respectively. By binding the CHD, these three CAMs may activate a common signal transduction pathway (Doherty and Walsh, 1996; Hall et al., 1996). The presumed NCAM binding region of the CHD in the FGF-R is homologous to the alternatively spliced VASE exon. Interestingly, adult NCAM forms containing the VASE exon are poor stimulators of neurite extension (Doherty et al., 1992), possibly because the presence of VASE in NCAM prevents binding of NCAM to the VASE-like sequence in the FGF-R. Others have presented evidence that NCAM mediated stimulation of neurite outgrowth requires p59fyn tyrosine kinase activity. Hence, NCAM specific stimulation of neurite extension is absent in neurons from fyn knock-out mice (Beggs et al., 1994). Moreover, NCAM-140 is reported to interact constitutively with the p59fyn, this complex in turn recruiting p125FAK following homophilic NCAM binding (Beggs et al., 1997). Presently, it is not known whether both of these pathways are activated under similar circumstances or whether crosstalk may occur. In addition to the FGF-R, the cell adhesion molecules L1 (Kadmon et al., 1990a) and TAG-1/axonin-1 (Milev et al., 1996) are believed to bind NCAM in heterophilic interactions. The NCAM-L1 binding may depend on an interaction between a carbohydrate on L1 and a lectin-like domain in the fourth Ig domain of NCAM (Kadmon et al., 1990a; Horstkorte et al., 1993). NCAM may thus strengthen homophilic L1 binding in a so-called assisted-homophilic interaction (Kadmon et al., 1990b). The presence of PSA on NCAM is thought to inhibit the homophilic L1 binding as well as homophilic NCAM binding, and thereby to decrease cell– cell adhesion (Acheson et al., 1991; Tang et al., 1994). However, under certain conditions PSA may function directly as a receptor (Joliot et al., 1991) and thereby possibly promote, rather than inhibit, cell adhesion. In addition to mediating cell– cell binding, NCAM can bind components of the extracellular matrix including collagens (Probstmeier et al., 1989), chondroitin sulphate proteoglycans (Grumet et al., 1993), and heparan sulphates (Cole et al., 1986) notably agrin (Storms et al., 1996). The overall adhesive behavior of a given NCAM expressing neuron thus depends on the expression of various NCAM ligands in the environment, including the extracellular matrix and other neurons and glial cells as well as on the splicing and glycosylation state of the expressed NCAM. THE ROLE OF NCAM IN DEVELOPMENT OF THE NERVOUS SYSTEM During development, NCAM expression is regulated in a manner suggesting that NCAM may be involved in morphogenesis (Edelmann and Crossin, 1991). The overall decrease in PSANCAM expression and the parallel increase in the fraction of NCAM copies containing the VASE exon with development is generally thought to change NCAM from being a plasticity promoter to a stability promoter (Rutishauser and Landmesser, 1996). It is believed that PSA-NCAM or eNCAM allows structural remodeling by decreasing cell adhesion mediated by NCAM and L1 as a necessary prerequisite for activity-dependent formation of proper neuronal connections to occur in the developing brain. In the adult brain, most NCAM molecules carry low amounts of PSA and, therefore, tend to stabilize persisting structures through strong homophilic bindings. During development, PSA-NCAM expression correlates in time and space with axon outgrowth, branching, and contact formation in the corticospinal (Daston et al., 1996) and the retinotectal (Fraser et al., 1984; Yin et al., 1995; Williams et al., 1996) systems as well as in the formation of the neuromuscular junction (Landmesser et al., 1990; Tang et al., 1994). In transgenic mice without NCAM expression, the olfactory system develops abnormally resulting in a dramatically reduced olfactory bulb when compared to wild-type mice (To-
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masiewicz et al., 1993; Cremer et al., 1994). This effect can be phenocopied by removing PSA enzymatically by endo-N in wild-type mice (Ono et al., 1994), strongly suggesting that the expression of PSA-NCAM is crucial for the normal migration of olfactory granule cell precursors. In the hippocampal region of NCAM null mutants, the mossy fiber system does not fasciculate normally, which in turn, leads to secondary effects on the generation of synapses in the CA3 region (Cremer et al., 1997). In this region, polysialylation of NCAM thus appears to promote fasciculation of the mossy fiber axons in contrast to the defasciculating role normally attributed to PSA-NCAM. Despite these and other abnormalities in the nervous system of NCAM mutants, these mice develop relatively well, suggesting that other molecules may partially substitute for NCAM. In addition to the as yet poorly investigated NCAM2, L1, and N-cadherin are plausible candidates for partially substituting NCAM as they, as mentioned above, have been proposed to share signaling pathways (Doherty and Walsh, 1996) although the expression patterns of these CAMs are not similar to that of NCAM. In addition to the above-mentioned transgenic mice, a targeted mutation to express only secreted, soluble NCAM forms have been produced. However, this mutation appeared to be dominant lethal during embryogenesis, with severe morphological malformations being observed in chimeric embryos (Rabinowitz et al., 1996). This indicates that soluble NCAM forms have the potential to influence morphological development through heterophilic NCAM binding. NCAM IN LEARNING-ASSOCIATED PLASTICITY Generally, it is believed that in a learning process neuronal connections are subject to structural changes to establish long-term memory. Several recent studies indicate a role for NCAM in learning and establishment of long-term memory (Fields and Itoh, 1996). First, intracranial injection of NCAM antibodies have been shown to inhibit consolidation of a passive avoidance task, when administered in a discrete time window after the learning session. This has been shown in rats (Doyle et al., 1992a; Alexinsky et al., 1997) as well as in chicks (Scholey et al., 1993). In rats, injection of antibodies in the six to eight hours posttraining period impaired establishment of long-term memory for a passive avoidance response, when tested at the 48-h recall time. In chicks, amnesia for a passive avoidance response was observed when the injection of NCAM antibodies was performed in the five to eight hours posttraining period, but only when the recall was tested 24 h following training. In addition, it has been shown that NCAM is synthesized, among with other glycoproteins, in a glycoprotein-dependent phase of establishment of long-term memory occurring six to eight hours after the learning session (Scholey et al., 1993; Mileusnic et al., 1995). Second, NCAM knock-out mice have shown deficiency in spatial learning when tested in a Morris water maze (Cremer et al., 1994). However, it is not known whether this deficit in learning is due to defects in plasticity mechanisms or developmental defects. Third, changes in the posttranslational modification of NCAM have been observed following learning. In the adult brain, PSA-NCAM is only expressed in restricted areas including the olfactory system and the dentate gyrus in the hippocampal formation (Fig. 3), areas thought to be characterized by a high level of structural remodeling in the adult (Miragall et al., 1988; Seki and Arai, 1991). An increased degree of polysialylation of NCAM has been demonstrated in granule cells of the dentate gyrus in the adult rat after learning of a passive avoidance response (Doyle et al., 1992b; Fox et al., 1995) and after spatial learning in a Morris water maze (Murphy et al., 1996). Increased polysialylation of NCAM has, likewise, been observed in the entorhinal cortex after Morris water maze learning (O’Connell et al., 1997) suggesting that PSA-NCAM expression is activated in a cortico-hippocampal pathway follow-
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FIG. 3. (A) Immunohistochemistry showing PSA expression in the hippocampal formation in P80 rat brain. (B, C) PSA expression in the granule cell layer of the dentate gyrus (DG) and in the mossy fibers (mf) 0 h (B) and 12 h (C) after water-maze learning. (A.G. Foley, L.C.B. Rønn, and C.M. Regan, unpublished observations).
ing learning. The increase in polysialylation was observed only in the 10 –12-h posttraining period for both types of learning, and was probably due to polysialylation of NCAM on preexisting neurons rather than to increased neurogenesis (Fox et al., 1995). This increased polysialylation of NCAM has been shown to affect primarily one isoform of NCAM, NCAM180 (Doyle et al., 1992b). Because an increase in PSA-NCAM is thought to decrease cell adhesion and to stimulate neurite outgrowth, polysialylation of NCAM may allow structural remodeling of neuronal connections during establishment of long-term memory (Regan and Fox, 1995). Furthermore, impaired acquisition and retention of spatial memory has been observed in the rat following enzymatic removal of PSA with endo-neuraminidase (Becker et al., 1996). Interestingly, the expression of PSA-NCAM can be rapidly modulated by neuronal activity (Kiss et al., 1994; Muller et al., 1996; Rafuse and Landmesser, 1996). Finally, studies in the marine mollusc Aplysia california provide additional evidence for a role for NCAM in learning and memory. In vitro, learning-related formation of new synaptic connections is associated with downregulation of the Aplysia cell adhesion molecule, apCAM (Bailey et al., 1992; Mayford et al., 1992; Zhu et al., 1995), which probably is an Aplysia NCAM homologue. Presumably, this downregulation is a result of both decreased synthesis and increased endocytosis (Bailey et al., 1992; Mayford et al., 1992). The downregulation of apCAM may destabilize adhesive contacts between neurons in synapses, and thereby lead to a redistribution of membrane component and allow new synaptic connections to form. Furthermore, it has been shown that apCAM antibodies inhibit induction of long-term changes in synaptic structures. In Drosophila, another NCAM homologue, Fasciclin II, is crucial for the formation and stabilization of synapses in the neuromuscular junction (Schuster et al., 1996 a, b). In vitro, the role of NCAM in synaptic plasticity has been studied in hippocampal slice preparations. In this system, locally applied NCAM antibodies have been shown to inhibit the generation of long-term potentiation (LTP) in the CA1 region (Lu¨thi et al., 1994; Rønn et al., 1995). The effect is manifested within seconds after high-frequency stimulation, raising the possibility that NCAM may influence the phase during or immediately after LTP-induction. Such an action may depend on the presence of PSA-NCAM as the removal of PSA with endo-N prevents the induction of LTP in the acute hippocampal slice preparation (Becker et al., 1996)
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and in organotypic slice cultures (Muller et al., 1996). In slices from NCAM-deficient mice a strong inhibition of LTP induction has been observed when compared to slices from wild-type mice. In organotypic slice cultures from NCAM-deficient mice, inhibition of LTP was likewise observed (Muller et al., 1996), although in this case the effect was manifested as a slowly decaying LTP, suggesting that under these circumstances, the lack of NCAM affected early maintenance of LTP. Following induction of LTP in vivo, an increase in extracellular NCAM has been reported (Fazeli et al., 1994), possibly as the result of increased proteolytic activity two to three hours following LTP induction. TOWARDS AN UNDERSTANDING OF NCAM STRUCTURE AND FUNCTION In recent years, a number of studies have contributed significantly to the understanding of the structure and function of NCAM. As the structure of individual domains of NCAM is being elucidated, a better understanding of the binding properties of NCAM will undoubtedly result. In vitro studies have shown that cell adhesion molecules including NCAM not only function as cell glues; rather, ligation of NCAM activates intracellular signaling pathways, which in turn, influences behavioral responses of neurons such as neurite extension. In addition to this outside-in signaling, neuronal activity may affect polysialylation of NCAM, thereby effecting an inside-out signaling with important impact on the adhesive properties of the cell. By interfering with normal NCAM function it has been shown that NCAM is important not only during brain development but also in synaptic plasticity in the adult brain associated with regeneration and learning, but the mechanisms are poorly understood. It, therefore, remains to be determined how the signaling and adhesive functions of NCAM is involved in neuronal development and plasticity in vivo. REFERENCES ACHESON, A., SUNSHINE, J.L., and RUTISHAUSER, U. NCAM polysialic acid can regulate both cell– cell and cell–substrate interactions. J. Cell Biol. 114, 143–153, 1991. ALEXINSKY, T., PRZYBYSLAWSKI, J., MILEUSNIC, R., ROSE, S.P., and SARA, S.J. Antibody to day-old chick brain glycoprotein produces amnesia in adult rats. Neurobiol. Learn. Mem. 67, 14 –20, 1997. ANGATA, K., NAKAYAMA, J., FREDETTE, B., CHONG, K., RANSCHT, B., and FUKUDA, M. Human STX polysialyltransferase forms the embryonic form of the neural cell adhesion molecule. Tissue-specific expression, neurite outgrowth, and chromosomal localization in comparison with another polysialyltransferase, PST. J. Biol. Chem. 272, 7182–7190, 1997. BAILEY, C.H., CHEN, M., KELLER, F., and KANDEL, E.R. Serotonin-mediated endocytosis of apCAM: An early step of learning-related synaptic growth in Aplysia. Science 256, 645– 649, 1992. BECKER, C.G., ARTOLA, A., GERARDY-SCHAHN, R., BECKER, T., WELZL, H., and SCHACHNER, M. The polysialic acid modification of the neural cell adhesion molecule is involved in spatial learning and hippocampal long-term potentiation. J. Neurosci. Res. 45, 143–152, 1996. BEGGS, H.E., SORIANO, P., and MANESS, P.F. NCAM-dependent neurite outgrowth is inhibited in neurons from Fyn-minus mice. J. Cell Biol. 127, 825– 833, 1994. BEGGS, H.E., BARAGONA, S.C., HEMPERLY, J.J., and MANESS, P.F. NCAM140 interacts with the focal adhesion kinase p125fak and the SRC-related tyrosine kinase p59fyn. J. Biol. Chem. 272, 8310 – 8319, 1997. BOCK, E., EDVARDSEN, K., GIBSON, A., LINNEMANN, D., LYLES, J.M., and NYBROE, O. Characterization of soluble forms of NCAM. FEBS Lett. 225, 33–36, 1987. ¨ MMENDORF, T. and RATHJEN, F.G. Cell adhesion molecules 1: Immunoglobulin superfamily. Prot. Profile 2, BRU 963–1108, 1995. COLE, G.J., LOEWY, A., and GLASER, L. Neuronal cell– cell adhesion depends on interactions of N-CAM with heparin-like molecules. Nature 320, 445– 447, 1986. CREMER, H., LANGE, R., CHRISTOPH, A., PLOMANN, M., VOPPER, G., ROES, J., BROWN, R., BALDWIN, S.,
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861
KRAEMER, P., SCHEFF, S., BAERHELS, D., RAJEWSKY, K., and WILLE, W. Inactivation of the N-CAM gene in mice results in size reduction of the olfactory bulb and deficiets in spatial learning. Nature 367, 455– 459, 1994. CREMER, H., CHAZAL, G., GORIDIS, C., and REPRESA, A. NCAM is essential for axonal growth and fasciculation in the hippocampus. Mol. Cell. Neurosci. 8, 323–335, 1997. DASTON, M.M., BASTMEYER, M., RUTISHAUSER, U., and O’LEARY, D.D. Spatially restricted increase in polysialic acid enhances corticospinal axon branching related to target recognition and innervation. J. Neurosci. 16, 5488 –5497, 1996. DOHERTY, P., ASHTON, S.V., MOORE, S.E., and WALSH, F.S. Morphoregulatory activities of NCAM and N-cadherin can be accounted for by G protein-dependent activation of L- and N-type neuronal calcium-channels. Cell 67, 21–33, 1991. DOHERTY, P., MOOLENAAR, C.E., ASHTON, S.V., MICHALIDES, R.J., and WALSH, F.S. The VASE exon downregulates the neurite growth-promoting activity of NCAM 140. Nature 356, 791–793, 1992. DOHERTY, P. and WALSH, F.S. CAM-FGF receptor interactions: A model for axonal growth. Mol. Cell. Neurosci. 8, 99 –111, 1996. DOYLE, E., NOLAN, P.M., BELL, R., and REGAN, C.M. Intraventricular infusions of anti-neural cell adhesion molecules in a discrete posttraining period impair consolidation of a passive avoidance response in the rat. J. Neurochem. 59, 1570 –1573, 1992a. DOYLE, E., NOLAN, P.M., BELL, R., and REGAN, C.M. Hippocampal NCAM180 transiently increases sialylation during the aquisition and consolidation of a passive avoidance response in the adult rat. J. Neurosci. Res. 31, 513–523, 1992b. ECKHARDT, M., MUHLENHOFF, M., BETHE, A., KOOPMAN, J., and FROSCH, M. Molecular characterization of eukaryotic polysialyltransferase-1. Nature 373, 715–718, 1995. EDELMAN, G.M. and CHUONG, C.M. Embryonic to adult conversion of neural cell adhesion molecules in normal and staggerer mice. Proc. Natl. Acad. Sci. USA 79, 7036 –7040, 1982. EDELMANN, G.M. and CROSSIN, K.L. Cell adhesion molecules: Implications for a molecular histology. Annu. Rev. Biochem. 60, 155–190, 1991. FAZELI, M.S., BREEN, K., ERRINGTON, M.L., and BLISS, T.V.P. Increase in extracellular NCAM and amyloid precursor protein following induction of long-term potentiation in the dentate gyrus of anaesthetized rats. Neurosci. Lett. 169, 77– 80, 1994. FIELDS, R.D. and ITOH, K. Neural cell adhesion molecule in activity-dependent development and synaptic plasticity. Trends Neurosci. 19, 473– 480, 1996. FOX, G.B., O’CONNELL, A.W., MURPHY, K.J., and REGAN, C.M. Memory consolidation induces a transient and time-dependent increase in the frequency of neural cell adhesion molecule polysialylated cells in the adult rat hippocampus. J. Neurochem. 65, 2796 –2799, 1995. FRASER, S.E., MURRAY, B.A., CHUONG, C.M., and EDELMAN, G.M. Alteration of the retinotectal map in Xenopus by antibodies to neural cell adhesion molecules. Proc. Natl. Acad. Sci. USA 81, 4222– 4226, 1984. GEGELASHVILI, G., ANDERSSON, A.M., SCHOUSBOE, A., and BOCK, E. Cyclic AMP regulates NCAM expression and phosphorylation in cultured mouse astrocytes. Eur. J. Cell Biol. 62, 343–351, 1993. GRUMET, M., FLACCUS, A., and MARGOLIS, R.U. Functional characterization of chondroitin sulfate proteoglycans of brain: Interactions with neurons and neural cell adhesion molecules. J. Cell Biol. 120, 815– 824, 1993. HALL, H., WALSH, F.S., and DOHERTY, P. A role for the FGF receptor in the axonal growth response stimulated by cell adhesion molecules. Cell Adhes. Commun. 3, 441– 450, 1996. HOLDEN, H.M., ITO, M., HARTSHORNE, D.J., and RAYMENT, I. X-ray structure determination of telokin, the C-terminal domain of myosin light chain kinase, at 2.8 A resolution. J. Mol. Biol. 227, 840 – 851, 1992. HORSTKORTE, R., SCHACHNER, M., MAGYAR, J.P., VORHERR, T., and SCHMITZ, B. The fourth immunoglobulin-like domain of NCAM contains a carbohydrate recognition domain for oligomannosidic glycans implicated in association with L1 and neurite outgrowth. J. Cell Biol. 121, 1409 –1421, 1993. JOLIOT, A.H., TRILLER, A., VOLOVITCH, M., PERNELLE, C., and PROCHIANTZ, A. Alpha-2,8-Polysialic acid is the neuronal surface receptor of antennapedia homeobox peptide. New Biol. 3, 1121–1134, 1991. KADMON, G., KOWITZ, A., ALTEVOGT, P., and SCHACHNER, M. Functional cooperation between the neural adhesion molecules L1 and N-CAM is carbohydrate dependent. J. Cell Biol. 110, 209 –218, 1990a. KADMON, G., KOWITZ, A., ALTEVOGT, P., and SCHACHNER, M. The neural cell adhesion molecule N-CAM enhances L1-dependent cell-cell interactions. J. Cell Biol. 110, 193–208, 1990b. KISELYOV, V.V., BEREZIN, V., MAAR, T.E., SOROKA, V., EDVARDSEN, K., SCHOUSBOE, A., and BOCK, E. The first Ig-like NCAM domain is involved in double reciprocal interaction with the second Ig-like NCAM domain and in heparin binding. J. Biol. Chem. 272, 10125–10134, 1996.
862
L.C.B. RØNN et al.
KISS, J.Z., WANG, C., OLIVE, S., ROUGON, G., LANG, J., BAETENS, D., and HARRY, D. Activity-dependent mobilization of the adhesion molecule polysialic NCAM to the cell surface of neurons and endocrine cells. EMBO J. 13, 5284 –5292, 1994. KROG, L. and BOCK, E. Glycosylation of neural cell adhesion molecules of the immunoglobulin superfamily. APMIS Suppl. 27, 53–70, 1992. LANDMESSER, L., DAHM, L., TANG, J.C., and RUTISHAUSER, U. Polysialic acid as a regulator of intramuscular nerve branching during embryonic development. Neuron 4, 655– 667, 1990. LINNEMANN, D., LYLES, J.M., and BOCK, E. A developmental study of the biosynthesis of the neural cell adhesion molecule. Dev. Neurosci. 7, 230 –238, 1985. ¨ THI, A., LAURENT, J.P., FIGUROV, A., MULLER, D., and SCHACHNER, M. Hippocampal long-term potentiLU ation and neural cell adhesion molecules L1 and NCAM. Nature 372, 777–779, 1994. MARTERSTECK, C.M., KEDERSHA, N.L., DRAPP, D.A., TSUI, T.G., and COLLEY, K.J. Unique alpha 2, 8-polysialylated glycoproteins in breast cancer and leukemia cells. Glycobiology 6, 289 –301, 1996. MAYFORD, M., BARZILAI, A., KELLER, F., SCHACHER, S., and KANDEL, E.R. Modulation of an NCAM-related adhesion molecule with long-term synaptic plasticity in Aplysia. Science 256, 638 – 644, 1992. MILEUSNIC, R., ROSE, S.P., LANCASHIRE, C., and BULLOCK, S. Characterisation of antibodies specific for chick brain neural cell adhesion molecules which cause amnesia for a passive avoidance task. J. Neurochem. 64, 2598 –2606, 1995. MILEV, P., MAUREL, P., HARING, M., MARGOLIS, R.K., and MARGOLIS, R.U. TAG-1/axonin-1 is a high-affinity ligand of neurocan, phosphacan/protein-tyrosine phosphatase-zeta/beta, and N-CAM. J. Biol. Chem. 271, 15716 – 15723, 1996. MIRAGALL, F., KADMON, G., HUSMANN, M., and SCHACHNER, M. Expression of cell adhesion molecules in the olfactory system of the adult mouse: Presence of the embryonic form of N-CAM. Dev. Biol. 129, 516 –531, 1988. ¨ HLENHOFF, M., ECKHARDT, M., BETHE, A., FROSCH, M., and GERARDY-SCHAHN, R. Autocatalytic MU polysialylation of polysialyltransferase-1. EMBO J. 15, 6943– 6950, 1996. MULLER, D., WANG, C., SKIBO, G., TONI, N., CREMER, H., CALAORA, V., ROUGON, G., and KISS, J.Z. PSA-NCAM is required for activity-induced synaptic plasticity. Neuron 17, 413– 422, 1996. MURPHY, K.J., O’CONNELL, A.W., and REGAN, C.M. Repetitive and transient increases in hippocampal neural cell adhesion molecule polysialylation state following multitrial spatial training. J. Neurochem. 67, 1268 –1274, 1996. MURRAY, B.A., HEMPERLY, J.J., PREDIGER, E.A., EDELMAN, G.M., and CUNNINGHAM, B.A. Alternatively spliced mRNAs code for different polypeptide chains of the chicken neural cell adhesion molecule (N-CAM). J. Cell Biol. 102, 189 –193, 1986. NAKAYAMA, J., FUKUDA, M.N., FREDETTE, B., RANSCHT, B., and FUKUDA, M. Expression cloning of a human polysialyltransferase that forms the polysialylated neural cell adhesion molecule present in emryonic brain. Proc. Natl. Acad. Sci. USA 922, 7031–7035, 1995. NAKAYAMA, J. and FUKUDA, M. A human polysialyltransferase directs in vitro synthesis of polysialic acid. J. Biol. Chem. 271, 1829 –1832, 1996. NOBLE, M., ALBRECHTSEN, M., MOLLER, C., LYLES, J., BOCK, E., GORIDIS, C., and RUTISHAUSER, U. Glial cells express N-CAM/D2-CAM-like polypeptides in vitro. Nature 316, 725–728, 1985. O’CONNELL, A.W., FOX, G.B., BARRY, T., FOLEY, A.G., MURPHY, K.J., FICHERA, G., KELLY, J., and REGAN, C.M. Spatial learning activates neural cell adhesion molecule polysialylation in a cortico-hippocampal pathway within the medial temporal lobe. J. Neurochem. 68, 2538 –2546, 1997. OLSEN, M., KROG, L., EDVARDSEN, K., SKOVGAARD, L.T., and BOCK, E. Intact transmembrane isoforms of the neural cell adhesion molecule are released from the plasma membrane. Biochem. J. 295, 833– 840, 1993. ONO, K., TOMASIEWICZ, H., MAGNUSON, T., and RUTISHAUSER, U. N-CAM mutation inhibits tangential neuronal migration and is phenocopied by enzymatic removal of polysialic acid. Neuron 13, 595– 609, 1994. PAOLONI-GIACOBINO, A., CHEN, H., and ANTONARAKIS, S.E. Cloning of a novel human neural cell adhesion molecule gene (NCAM2) that maps to chromosome region 21q21 and is potentially involved in Down syndrome. Genomics 43, 43–51, 1997. PFUHL, M. and PASTORE, A. Tertiary structure of an immunoglobulin-like domain from the giant muscle protein titin: A new member of the I set. Structure 3, 391– 401, 1995. PHILLIPS, G.R., KRUSHEL, L.A., and CROSSIN, K.L. Developmental expression of two rat sialyltransferases that modify the neural cell adhesion molecule, N-CAM. Dev. Brain Res. 102, 143–155, 1997. PROBSTMEIER, R., KUHN, K., and SCHACHNER, M. Binding properties of the neural cell adhesion molecule to different components of the extracellular matrix. J. Neurochem. 53, 1794 –1801, 1989.
NCAM IN DEVELOPMENT AND PLASTICITY
863
RABINOWITZ, J.E., RUTISHAUSER, U., and MAGNUSON, T. Targeted mutation of Ncam to produce a secreted molecule results in a dominant embryonic lethality. Proc. Natl. Acad. Sci. USA 93, 6421– 6424, 1996. RAFUSE, V.F. and LANDMESSER, L. Contractile activity regulates isoform expression and polysialylation of NCAM in cultured myotubes: Involvement of Ca21 and protein kinase C. J. Cell Biol. 132, 969 –983, 1996. RANHEIM, T.S., EDELMAN, G.M., and CUNNINGHAM, B.A. Homophilic adhesion mediated by the neural cell adhesion molecule involves multiple immunoglobulin domains. Proc. Natl. Acad. Sci. USA 93, 4071– 4075, 1996. RAO, Y., WU, X.F., GARIEPY, J., RUTISHAUSER, U., and SIU, C.H. Identification of a peptide sequence involved in homophilic binding in the neural cell adhesion molecule NCAM. J. Cell Biol. 118, 937–949, 1992. RAO, Y., WU, X.F., YIP, P., GARIEPY, J., and SIU, C.H. Structural characterization of a homophilic binding site in the neural cell adhesion molecule. J. Biol. Chem. 268, 20630 –20638, 1993. RAO, Y., ZHAO, X., and SIU, C.H. Mechanism of homophilic binding mediated by the neural cell adhesion molecule NCAM. Evidence for isologous interaction. J. Biol. Chem. 269, 27540 –27548, 1994. REGAN, C.M. and FOX, G.B. Polysialylation as a regulator of neural plasticity in rodent learning and aging. Neurochem. Res. 20, 593–598, 1995. RØNN, L.C.B., BOCK, E., LINNEMANN, D., and JAHNSEN, H. NCAM-antibodies modulate induction of long-term potentiation in rat hippocampal CA1. Brain Res. 677, 145–151, 1995. ROUGON, G., DEAGOSTINI-BAZIN, H., HIRN, M., and GORIDIS, C. Tissue- and developmental stage-specific forms of a neural cell surface antigen linked to differences in glycosylation of a common polypeptide. EMBO J. 1, 1239 –1244, 1982. ROUGON, G. Structure, metabolism and cell biology of polysialic acids. Eur. J. Cell Biol. 61, 197–207, 1993. RUTISHAUSER, U. and LANDMESSER, L. Polysialic acid in the vertebrate nervous system: A promoter of plasticity in cell– cell interactions. Trends Neurosci. 19, 422– 427, 1996. SAFFELL, J.L., WILLIAMS, E.J., MASON, I.J., WALSH, F.S., and DOHERTY, P. Expression of a dominant negative FGF receptor inhibits axonal growth and FGF receptor phosphorylation stimulated by CAMs. Neuron 18, 231–242, 1997. SCHEIDEGGER, E.P., STERNBERG, L.R., ROTH, J., and LOWE, J.B. A human STX cDNA confers polysialic acid expression in mammalian cells. J. Biol. Chem. 270, 22685–22688, 1995. SCHOLEY, A.B., ROSE, S.P.R., ZAMANI, M.R., BOCK, E., and SCHACHNER, M. A role for the neural cell adhesion molecule (NCAM) in a late, consolidating phase of glycoprotein synthesis 6 hours following passive avoidance training of the young chick. Neuroscience 55, 499 –509, 1993. SCHUCH, U., LOHSE, M.J., and SCHACHNER, M. Neural cell adhesion molecules influence second messenger systems. Neuron 3, 13–20, 1989. SCHUSTER, C.M., DAVIS, G.W., FETTER, R.D., and GOODMAN, C.S. Genetic dissection of structural and functional components of synaptic plasticity. I. Fasciclin II controls synaptic stabilization and growth. Neuron 17, 641– 654, 1996a. SCHUSTER, C.M., DAWIS, G.W., FETTER, R.D., and GOODMAN, C.S. Genetic dissection of structural and functional components of synaptic plasticity. II. Fasciclin II controls presynaptic structural plasticity. Neuron 17, 655– 667, 1996b. SEKI, T. and ARAI, Y. The persistent expression of a highly sialylated NCAM in the dentate gyrus of the adult rat. Neurosci. Res. 12, 503–513, 1991. SMALL, S.J., HAINES, S.L., and AKESON, R.A. Polypeptide variation in an N-CAM extracellular immunoglobulinlike fold is developmentally regulated through alternative splicing. Neuron 1, 1007–1017, 1988. SMALL, S.J. and AKESON, R. Expression of the unique NCAM VASE exon is independently regulated in distinct tissues during development. J. Cell Biol. 111, 2089 –2096, 1990. SORKIN, B.C., HOFFMAN, S., EDELMAN, G.M., and CUNNINGHAM, B.A. Sulfation and phosphorylation of the neural cell adhesion molecule, N-CAM. Science 225, 1476 –1478, 1984. STORMS, S.D., KIM, A.C., TRAN, B.T., COLE, G.J., and MURRAY, B.A. NCAM-mediated adhesion of transfected cells to agrin. Cell Adhes. Commun. 3, 497–509, 1996. TANG, J., RUTISHAUSER, U., and LANDMESSER, L. Polysialic acid regulates growth cone behavior during sorting of motor axons in the plexus region. Neuron 13, 405– 414, 1994. THOMSEN, N.K., SOROKA, V., JENSEN, P.H., BEREZIN, V., KISELYOV, V.V., and BOCK, E. The threedimensional structure of the first domain of neural cell adhesion molecule. Nat. Struct. Biol. 3, 581–585, 1996. TOMASIEWICZ, H., ONO, K., YEE, D., THOMPSON, C., GORIDIS, C., RUTISHAUSER, U., and MAGNUSON, T. Genetic deletion of a neural cell adhesion molecule variant (N-CAM-180) produces distinct defects in the central nervous system. Neuron 11, 1163–1174, 1993.
864
L.C.B. RØNN et al.
VON BOHLEN UND HALBACH, F., TAYLOR, J., and SCHACHNER, M. Cell type specific effects of the neural cell adhesion molecules L1 and N-CAM on diverse second messenger systems. Eur. J. Neurosci. 4, 896 –909, 1992. WALSH, F.S. and DICKSON, G. Generation of multiple N-CAM polypeptides from a single gene. Bioessays 11, 83– 88, 1989. WANG, J.H., PEPINSKY, R.B., STEHLE, T., LIU, J.H., KARPUSAS, M., and BROWNING, B. The crystal structure of an N-terminal two-domain fragment of vascular cell adhesion molecule 1 (VCAM-1): A cyclic peptide based on the domain 1 C-D loop can inhibit VCAM-1-alpha 4 integrin interaction. Proc. Natl. Acad. Sci. USA 92, 5714 –5718, 1995. WILLIAMS, A.F. and BARCLAY, A.N. The immunoglobulin superfamily—Domains for cell surface recognition. Annu. Rev. Immunol. 6, 381– 405, 1988. WILLIAMS, D.K., GANNON-MURAKAMI, L., ROUGON, G., and UDIN, S.B. Polysialylated neural cell adhesion molecule and plasticity of ipsilateral connections in Xenopus tectum. Neuroscience 70, 277–285, 1996. WILLIAMS, E.J., FURNESS, J., WALSH, F.S., and DOHERTY, P. Activation of the FGF receptor underlies neurite outgrowth stimulated by L1, NCAM, and N-cadherin. Neuron 13, 583–594, 1994. YIN, X., WATANABE, M., and RUTISHAUSER, U. Effect of polysialic acid on the behavior of retinal ganglion cell axons during growth into the optic tract and tectum. Development 121, 3439 –3446, 1995. YOSHIDA, Y., KOJIMA, N., KUROSAWA, N., HAMAMOTO, T., and TSUJI, S. Molecular cloning of Sia alpha 2,3Gal beta 1,4GlcNAc alpha 2,8-sialyltransferase from mouse brain. J. Biol. Chem. 270, 14628 –14633, 1995. ZHU, H., WU, F., and SCHACHER, S. Changes in expression and distribution of Aplysia cell adhesion molecules can influence synapse formation and elimination in vitro. J. Neurosci. 15, 4173– 4183, 1995. ZUBER, C., LACKIE, P.M., CATTERALL, W.A., and ROTH, J. Polysialic acid is associated with sodium channels and the neural cell adhesion molecule N-CAM in adult rat brain. J. Biol. Chem. 267, 9965–9971, 1992.