Synaptotagmin-1 drives synchronous Ca2+-triggered fusion by C2B-domain-mediated synaptic-vesicle-membrane attachment

• Published in: Nature neuroscience Vol. 21; no. 1; pp. 33 - 40
• Main Authors: Chang, Shuwen, Trimbuch, Thorsten, Rosenmund, Christian
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.01.2018; Nature Publishing Group
• Subjects: 631/378/548/2589; 631/378/548/2590; Action potential; Animal Genetics and Genomics; Attachment; Behavioral Sciences; Binding sites; Biological Techniques; Biomedical and Life Sciences; Biomedicine; Calcium; Calcium-binding protein; Electron microscopy; Freezing; Machinery and equipment; Membrane fusion; Mutants; Mutation; Neurobiology; Neurosciences; Neurotransmitter release; Phospholipids; SNAP receptors; Synaptotagmin; Translocation
• ISSN: 1097-6256; 1546-1726; 1546-1726
• DOI: 10.1038/s41593-017-0037-5

The synaptic vesicle (SV) protein synaptotagmin-1 (Syt1) is the Ca 2+ sensor for fast synchronous release. Biochemical and structural data suggest that Syt1 interacts with phospholipids and SNARE complex, but the manner in which these interactions translate into SV fusion remains poorly understood. Using flash-and-freeze electron microscopy, which triggers action potentials with light and coordinately arrests synaptic structures with rapid freezing, we found that synchronous-release-impairing mutations in the Syt1 C 2 B domain (K325, 327; R398, 399) also disrupt SV-active-zone plasma-membrane attachment. Single action potential induction rescued membrane attachment in these mutants within less than 10 ms through activation of the Syt1 Ca 2+ -binding site. The rapid SV membrane translocation temporarily correlates with resynchronization of release and paired pulse facilitation. On the basis of these findings, we redefine the role of Syt1 as part of the Ca 2+ -dependent vesicle translocation machinery and propose that Syt1 enables fast neurotransmitter release by means of its dynamic membrane attachment activities. Synaptotagmin-1 (Syt1) controls synaptic vesicle–membrane attachment activities via its C2B domain. These correlate with release synchronization and synaptic short-term facilitation, revealing a mechanism for Syt1-mediated synchronous release.