Calcium‐Dependent Dissociation of Synaptotagmin from Synaptic SNARE Complexes
: The formation of the synaptic core (SNARE) complex constitutes a crucial step in synaptic vesicle fusion at the nerve terminal. The interaction of synaptotagmin I with this complex potentially provides a means of conferring Ca2+‐dependent regulation of exocytosis. However, the subcellular compartm...
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Published in | Journal of neurochemistry Vol. 74; no. 1; pp. 367 - 374 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Oxford UK
Blackwell Science Ltd
01.01.2000
Blackwell |
Subjects | |
Online Access | Get full text |
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Summary: | : The formation of the synaptic core (SNARE) complex constitutes a crucial step in synaptic vesicle fusion at the nerve terminal. The interaction of synaptotagmin I with this complex potentially provides a means of conferring Ca2+‐dependent regulation of exocytosis. However, the subcellular compartments in which interactions occur and their modulation by Ca2+ influx remain obscure. Sodium dodecyl sulfate (SDS)‐resistant core complexes, associated with synaptotagmin I, were enriched in rat brain fractions containing plasma membranes and docked synaptic vesicles. Depolarization of synaptosomes triggered [3H]GABA release and Ca2+‐dependent dissociation of synaptotagmin from the core complex. In perforated synaptosomes, synaptotagmin dissociation was induced by Ca2+ (30‐300 μM) but not Sr2+ (1 mM); it apparently required intact membrane bilayers but did not result in disassembly of trimeric SNARE complexes. Synaptotagmin was not associated with unstable v‐SNARE/t‐SNARE complexes, present in fractions containing synaptic vesicles and cytoplasm. These complexes acquired SDS resistance when N‐ethylmaleimide‐sensitive fusion protein (NSF) was inhibited with N‐ethylmaleimide or adenosine 5′‐O‐(3‐thiotriphosphate), suggesting that constitutive SNARE complex disassembly occurs in undocked synaptic vesicles. Our findings are consistent with models in which the Ca2+‐triggered release of synaptotagmin precedes vesicle fusion. NSF may then dissociate ternary core complexes captured by endocytosis and recycle/prime individual SNARE proteins. |
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Bibliography: | ATPγS, adenosine 5 (3‐thiotriphosphate); BSA, bovine serum albumin; MBP‐syt I, synaptotagmin I fused to maltose binding protein; NEM ethylmaleimide; NSF, NEM‐sensitive fusion protein; PAGE, polyacrylamide gel electrophoresis; SDS, sodium dodecyl sulfate; SNAP, soluble NSF attachment protein; SNAP‐25, synaptosomal‐associated protein of 25 kDa; SNARE, soluble NSF attachment protein receptor; VAMP, vesicle‐associated membrane protein. N Abbreviations used O ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0022-3042 1471-4159 |
DOI: | 10.1046/j.1471-4159.2000.0740367.x |