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A synaptotagmin suppressor screen indicates SNARE binding controls the timing and Ca2+ cooperativity of vesicle fusion

  1. Zhuo Guan
  2. Maria Bykhovskaia
  3. Ramon A Jorquera
  4. Roger Bryan Sutton
  5. Yulia Akbergenova
  6. J Troy Littleton Is a corresponding author
  1. Massachusetts Institute of Technology, United States
  2. Wayne State University School of Medicine, United States
  3. Universidad Central del Caribe, United States
  4. Texas Tech University Health Sciences Center, United States
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Cite as: eLife 2017;6:e28409 doi: 10.7554/eLife.28409

Abstract

The synaptic vesicle Ca2+ sensor Synaptotagmin binds Ca2+ through its two C2 domains to trigger membrane interactions. Beyond membrane insertion by the C2 domains, other requirements for Synaptotagmin activity are still being elucidated. To identify key residues within Synaptotagmin required for vesicle cycling, we took advantage of observations that mutations in the C2B domain Ca2+-binding pocket dominantly disrupt release from invertebrates to humans. We performed an intragenic screen for suppressors of lethality induced by expression of Synaptotagmin C2B Ca2+-binding mutants in Drosophila. This screen uncovered essential residues within Synaptotagmin that suggest a structural basis for several activities required for fusion, including a C2B surface implicated in SNARE complex interaction that is required for rapid synchronization and Ca2+ cooperativity of vesicle release. Using electrophysiological, morphological and computational characterization of these mutants, we propose a sequence of molecular interactions mediated by Synaptotagmin that promote Ca2+ activation of the synaptic vesicle fusion machinery.

Article and author information

Author details

  1. Zhuo Guan

    Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Maria Bykhovskaia

    Department of Neurology, Wayne State University School of Medicine, Detroit, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Ramon A Jorquera

    Neuroscience Department, Universidad Central del Caribe, Bayamon, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon 0000-0002-5460-1755
  4. Roger Bryan Sutton

    Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Yulia Akbergenova

    Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. J Troy Littleton

    Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
    For correspondence
    troy@mit.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon 0000-0001-5576-2887

Funding

National Institutes of Health (NS40296)

  • J Troy Littleton

National Institutes of Health (MH099557)

  • Maria Bykhovskaia

National Institutes of Health (AR063634)

  • Roger Bryan Sutton

National Institutes of Health (MH104536)

  • J Troy Littleton

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Axel T Brunger, Reviewing Editor, Stanford University Medical Center, United States

Publication history

  1. Received: May 5, 2017
  2. Accepted: September 11, 2017
  3. Accepted Manuscript published: September 12, 2017 (version 1)

Copyright

© 2017, Guan et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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