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

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The synaptic vesicle (SV) protein synaptotagmin-1 (Syt1) is the Ca2+ 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 C2B 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 Ca2+-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 Ca2+-dependent vesicle translocation machinery and propose that Syt1 enables fast neurotransmitter release by means of its dynamic membrane attachment activities.

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We thank A. Plested, M. Herman, J. Rizo, C. Garner and T. Südhof for discussions and comments on the manuscript, S. Watanabe and E. Jorgensen for technical support, the Charité viral core facility for virus production, and B. Söhl-Kielszinski for sample preparation. This work was supported by ERC grant SynVGLUT, Berlin Institute of Health, Stiftung Charite, German Research Council grants SFB958, Ro1296/7-1 and TRR186.

Author information


  1. Institut für Neurophysiologie, Charité - Universitätsmedizin, Berlin, Germany

    • Shuwen Chang
    • , Thorsten Trimbuch
    •  & Christian Rosenmund
  2. NeuroCure Cluster of Excellence Cluster, Berlin, Germany

    • Shuwen Chang
    • , Thorsten Trimbuch
    •  & Christian Rosenmund


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S.C. performed experiments and analyzed data. T.T. produced molecular reagents. S.C. and C.R. designed the experiments and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Christian Rosenmund.

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