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Complexin arrests a pool of docked vesicles for fast Ca 2+ ‐dependent release
Author(s) -
Malsam Jörg,
Parisotto Daniel,
Bharat Tanmay A M,
Scheutzow Andrea,
Krause Jean Michel,
Briggs John A G,
Söllner Thomas H
Publication year - 2012
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2012.164
Subject(s) - library science , biology , computer science
Regulated exocytosis requires that the assembly of the basic membrane fusion machinery is temporarily arrested. Synchronized membrane fusion is then caused by a specific trigger—a local rise of the Ca 2+ concentration. Using reconstituted giant unilamellar vesicles (GUVs), we have analysed the role of complexin and membrane‐anchored synaptotagmin 1 in arresting and synchronizing fusion by lipid‐mixing and cryo‐electron microscopy. We find that they mediate the formation and consumption of docked small unilamellar vesicles (SUVs) via the following sequence of events: Synaptotagmin 1 mediates v‐SNARE‐SUV docking to t‐SNARE‐GUVs in a Ca 2+ ‐independent manner. Complexin blocks vesicle consumption, causing accumulation of docked vesicles. Together with synaptotagmin 1, complexin synchronizes and stimulates rapid fusion of accumulated docked vesicles in response to physiological Ca 2+ concentrations. Thus, the reconstituted assay resolves both the stimulatory and inhibitory function of complexin and mimics key aspects of synaptic vesicle fusion.