Neurotransmitter release is triggered by a calcium- induced rearrangement in the Synaptotagmin-1/SNARE complex primary interface

• 成果类型: Article
• 署名作者: Toulme, Estelle; Lazaro, Andrea Salazar; Trimbuch, Thorsten; Rizo, Josep; Rosenmund, Christian
• 署名单位: Free University of Berlin; Humboldt University of Berlin; Charite Universitatsmedizin Berlin; Free University of Berlin; Humboldt University of Berlin; University of Texas System; University of Texas Southwestern Medical Center; University of Texas System; University of Texas Southwestern Medical Center; University of Texas System; University of Texas Southwestern Medical Center
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-12061
• DOI: 10.1073/pnas.2409636121
• 发表日期: 2024-10-15
• 关键词: 3-dimensional structure; ca2+-triggered fusion; phospholipid-binding; vesicle docking; c2b domain; transmission; exocytosis; synapses; terminus; snap-25

摘要

The Ca2+ sensor synaptotagmin-1 (Syt1) triggers neurotransmitter release together with the neuronal sensitive factor attachment protein receptor (SNARE) complex formed by syntaxin-1, SNAP25, and synaptobrevin. Moreover, Syt1 increases synaptic vesicle (SV) priming and impairs spontaneous vesicle release. The Syt1 C2B domain binds to the SNARE complex through a primary interface via two regions (I and II), but how exactly this interface mediates distinct functions of Syt1 and the mechanism underlying Ca2+ triggering of release are unknown. Using mutagenesis and electrophysiological experiments, we show that region II is functionally and spatially subdivided: Binding of C2B domain arginines to SNAP- 25 acidic residues at one face of region II is crucial for Ca2+- evoked release but not for vesicle priming or clamping of spontaneous release, whereas other SNAP- 25 and syntaxin-1 acidic residues at the other face mediate priming and clamping of spontaneous release but not evoked release. Mutations that disrupt region I impair the priming and clamping functions of Syt1 while, strikingly, mutations that enhance binding through this region increase vesicle priming and clamping of spontaneous release, but strongly inhibit evoked release and vesicle fusogenicity. These results support previous findings that the primary interface mediates the functions of Syt1 in vesicle priming and clamping of spontaneous release and, importantly, show that Ca2+ triggering of release requires a rearrangement of the primary interface involving dissociation of region I, while region II remains bound. Together with biophysical studies presented in [K. Jaczynska etal., bioRxiv [Preprint] (2024). https://doi. org/10.1101/2024.06.17.599417 (Accessed 18 June 2024)], our data suggest a model whereby this rearrangement pulls the SNARE complex to facilitate fast SV fusion.