2013 Fiscal Year Final Research Report

Dissociation of synaptotagmin from SNARE complexes

Research Project

Project/Area Number	23590259
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Research Field	General physiology
Research Institution	Okayama University
Principal Investigator	NISHIKI Teiichi 岡山大学, 医歯(薬)学総合研究科, 准教授 (70423340)
Project Period (FY)	2011 – 2013
Keywords	神経科学 / 刺激分泌連関 / シナプス小胞 / カルシウムイオン / 開口放出
Research Abstract	Synaptotagmin, a synaptic vesicle protein containing two C2 domains (C2A, C2B), is a putative Ca2+ sensor for neurotransmitter release that cooperates with SNARE complexes. Whereas experiments using soluble fragments have shown that synaptotagmin-SNARE interactions require Ca2+ binding to both C2 domains, Ca2+ binding to C2B is more critical for release. Therefore, it is still unknown how synaptotagmin transduces Ca2+ signals to SNARE-mediated exocytosis. In this study, we showed that Ca2+ binding to the C2B domain released synaptotagmin from syntaxin within SNARE complexes at 37 degrees Celsius when using native proteins, proteins expressed in mammalian cells, or bacterial-expressed proteins reconstituted into liposomes. Together with the previous functional analysis, our findings indicate that synaptotagmin dissociates from SNARE complexes by Ca2+ during transmitter release and, thus, acts as a clamp that suppresses SNARE activity until Ca2+ influx.