ausblenden:
Schlagwörter:
exocytosis
fusion
reconstitution
SNARE
synaptic vesicle
fusion in-vitro
membrane-fusion
neurotransmitter release
synaptotagmin-i
snare complex
calcium-dependence
3-dimensional
structure
synaptic transmission
transmitter release
secretory
vesicles
Biochemistry & Molecular Biology
Cell Biology
Zusammenfassung:
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 Ca2+ 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 Ca2+-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 Ca2+ concentrations. Thus, the reconstituted assay resolves both the stimulatory and inhibitory function of complexin and mimics key aspects of synaptic vesicle fusion. The EMBO Journal (2012) 31, 3270-3281. doi:10.1038/emboj.2012.164; Published online 15 June 2012
