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Probing the process of quantal transmitter release with clostridial neurotoxins
9th Meeting of the BSN
PROBING THE PROCESS OF QUANTAL TRANSMITTER RELEASE WITH CLSTRIDIAL NEUROTOXINS J.O. Dolly, A.C. Ashton, P. DanielsHolgate and J.M. Edwardson* Depts. Biochem., Imperial College, London and *Pharmacol., Univ. Cambridge U.K. Intra-neuronally, botulinum (BoNT) and+tetanus (TeTX) neurotoxins block Ca* -dependent release of all transmitters tested, and diminish exocytosis from permeabilised chromaffin or PC12 cells. Yet, exposure of permeabilised pancreatic acinar cells to BoNT type A or its isolated light chain failed to reduce appreciably amylase secretion elicited by CaZ and ATP or GTPyS. BoNT and TeTX iniibited transmitter release at and outside ac‘tive zones mes. A23187. a Ca reversed the inhibition of release at active zones produced by BoNT type A but not E. Unlike BoNT A, inhibition of synaptosomal transmitter release by BoNT B or TeTX,at and outside active was antagonised partially by zones, disassembly of microtubules. Thus, these toxins provide an armoury of probes for secretion because of their spectrum of action.
THE MECHANISM OF GLUTAMATE RELEASE
s19
TRANSMITTER
David G. Nicholls, Jennifer Pocock, Talvinder Sihra, Harvey McMahon, Anne Barria and EleanorCc-y Dept.of Biochemistry Dundee, Scotlend The synaptosome has proved vowed elucidation of sspects of glutamaterg taleas is triggered by C$+ entry through a noninactivating channel whii can be inhibited by a nQvel toxin from the spMer Agelenqxsis apetta. There is a localized interaction beMeet Ca2’ and the exocytaic trigger before equilibration occurs with the bulk cytoplasm. KCl-evoked releaseisbiphasic,sugg&ngthepmsenceofWopoolsof vesicles. Botulinurn A toxin PreferentkJly inhibits the slow phase of release, consistent with a cytoskeletel interactkIn. Protein kinase C modulates the release of glutamate by controlling the Intensity or duration of action potentials which can be induced by 4-aminopyddine, consistent with a locus of action at a K+&armel. B& supports release to the same extent as C$*. This is @lifkhI because the calmodulm-mediated phosphotylation d the presynaptic synapsin phosphoproteins is greatly reduced under tlWW conditions, questioning an obligatory role of this process in vesicle liberation under these condkions. In Contrast the phosphatase inhibitor okadiac acid is highly inhibitory.
PROBING THE PROCESS OF QUANTAL TRANSMITTER RELEASE WITH CLSTRIDIAL NEUROTOXINS J.O. Dolly, A.C. Ashton, P. DanielsHolgate and J.M. Edwardson* Depts. Biochem., Imperial College, London and *Pharmacol., Univ. Cambridge U.K. Intra-neuronally, botulinum (BoNT) and+tetanus (TeTX) neurotoxins block Ca* -dependent release of all transmitters tested, and diminish exocytosis from permeabilised chromaffin or PC12 cells. Yet, exposure of permeabilised pancreatic acinar cells to BoNT type A or its isolated light chain failed to reduce appreciably amylase secretion elicited by CaZ and ATP or GTPyS. BoNT and TeTX iniibited transmitter release at and outside ac‘tive zones mes. A23187. a Ca reversed the inhibition of release at active zones produced by BoNT type A but not E. Unlike BoNT A, inhibition of synaptosomal transmitter release by BoNT B or TeTX,at and outside active was antagonised partially by zones, disassembly of microtubules. Thus, these toxins provide an armoury of probes for secretion because of their spectrum of action.
THE MECHANISM OF GLUTAMATE RELEASE
s19
TRANSMITTER
David G. Nicholls, Jennifer Pocock, Talvinder Sihra, Harvey McMahon, Anne Barria and EleanorCc-y Dept.of Biochemistry Dundee, Scotlend The synaptosome has proved vowed elucidation of sspects of glutamaterg taleas is triggered by C$+ entry through a noninactivating channel whii can be inhibited by a nQvel toxin from the spMer Agelenqxsis apetta. There is a localized interaction beMeet Ca2’ and the exocytaic trigger before equilibration occurs with the bulk cytoplasm. KCl-evoked releaseisbiphasic,sugg&ngthepmsenceofWopoolsof vesicles. Botulinurn A toxin PreferentkJly inhibits the slow phase of release, consistent with a cytoskeletel interactkIn. Protein kinase C modulates the release of glutamate by controlling the Intensity or duration of action potentials which can be induced by 4-aminopyddine, consistent with a locus of action at a K+&armel. B& supports release to the same extent as C$*. This is @lifkhI because the calmodulm-mediated phosphotylation d the presynaptic synapsin phosphoproteins is greatly reduced under tlWW conditions, questioning an obligatory role of this process in vesicle liberation under these condkions. In Contrast the phosphatase inhibitor okadiac acid is highly inhibitory.