1. Neuroscience
  2. Structural Biology and Molecular Biophysics
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Ring-like oligomers of Synaptotagmins and related c2 domain proteins

  1. Maria N Zanetti
  2. Oscar D Bello
  3. Jing Wang
  4. Jeff Coleman
  5. Yiying Cai
  6. Charles V Sindelar
  7. James E Rothman  Is a corresponding author
  8. Shyam S Krishnakumar  Is a corresponding author
  1. Yale School of Medicine, United States
Research Article
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Cite this article as: eLife 2016;5:e17262 doi: 10.7554/eLife.17262

Abstract

We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca2+-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca2+ involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca2+ influx.

Article and author information

Author details

  1. Maria N Zanetti

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.

  2. Oscar D Bello

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.

  3. Jing Wang

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.

  4. Jeff Coleman

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.

  5. Yiying Cai

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.

  6. Charles V Sindelar

    Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.

  7. James E Rothman

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    For correspondence
    james.rothman@yale.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-8653-8650

  8. Shyam S Krishnakumar

    Department of Cell Biology, Yale School of Medicine, New Haven, United States
    For correspondence
    shyam.krishnakumar@yale.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-6148-3251

Funding

National Institute of General Medical Sciences (GM071458)

  • James E Rothman

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, Howard Hughes Medical Institute, Stanford University, United States

Publication history

  1. Received: April 26, 2016
  2. Accepted: July 18, 2016
  3. Accepted Manuscript published: July 19, 2016 (version 1)
  4. Version of Record published: August 8, 2016 (version 2)

Copyright

© 2016, Zanetti 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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    Circular oligomerization is an intrinsic property of synaptotagmin

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    Previously, we showed that synaptotagmin1 (Syt1) forms Ca2+-sensitive ring-like oligomers on membranes containing acidic lipids and proposed a potential role in regulating neurotransmitter release (Zanetti et al., 2016). Here, we report that Syt1 assembles into similar ring-like oligomers in solution when triggered by naturally occurring polyphosphates (PIP2 and ATP) and magnesium ions (Mg2+). These soluble Syt1 rings were observed by electron microscopy and independently demonstrated and quantified using fluorescence correlation spectroscopy. Oligomerization is triggered when polyphosphates bind to the polylysine patch in C2B domain and is stabilized by Mg2+, which neutralizes the Ca2+-binding aspartic acids that likely contribute to the C2B interface in the oligomer. Overall, our data show that ring-like polymerization is an intrinsic property of Syt1 with reasonable affinity that can be triggered by the vesicle docking C2B-PIP2 interaction and raise the possibility that Syt1 rings could pre-form on the synaptic vesicle to facilitate docking.

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