Journal
NATURE STRUCTURAL & MOLECULAR BIOLOGY
Volume 13, Issue 4, Pages 323-330Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/nsmb1076
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Funding
- NIGMS NIH HHS [GM 56827] Funding Source: Medline
- NIMH NIH HHS [MH61876] Funding Source: Medline
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In nerve terminals, exocytosis is mediated by SNARE proteins and regulated by Ca2+ and synaptotagmin-1 ( syt). Ca2+ promotes the interaction of syt with anionic phospholipids and the target membrane SNAREs ( t-SNAREs) SNAP-25 and syntaxin. Here, we have used a defined reconstituted fusion assay to determine directly whether syt-t-SNARE interactions couple Ca2+ to membrane fusion by comparing the effects of Ca2+-syt on neuronal ( SNAP-25, syntaxin and synaptobrevin) and yeast ( Sso1p, Sec9c and Snc2p) SNAREs. Ca2+-syt aggregated neuronal and yeast SNARE liposomes to similar extents via interactions with anionic phospholipids. However, Ca2+-syt was able to bind and stimulate fusion mediated by only neuronal SNAREs and had no effect on yeast SNAREs. Thus, Ca2+-syt regulates fusion through direct interactions with t-SNAREs and not solely through aggregation of vesicles. Ca2+-syt drove assembly of SNAP-25 onto membrane-embedded syntaxin, providing direct evidence that Ca2+-syt alters t-SNARE structure.
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