Autoinhibition of Munc18-1 modulates synaptobrevin binding and helps to enable Munc13-dependent regulation of membrane fusion

  1. Ewa Sitarska
  2. Junjie Xu
  3. Seungmee Park
  4. Xiaoxia Liu
  5. Bradley Quade
  6. Karolina Stepien
  7. Kyoko Sugita
  8. Chad A Brautigam
  9. Shuzo Sugita
  10. Josep Rizo  Is a corresponding author
  1. European Molecular Biology Laboratory, Germany
  2. University of Texas Southwestern Medical Center, United States
  3. University of Toronto, Canada

Abstract

Munc18-1 orchestrates SNARE complex assembly together with Munc13-1 to mediate neurotransmitter release. Munc18-1 binds to synaptobrevin, but the relevance of this interaction and its relation to Munc13 function are unclear. NMR experiments now show that Munc18-1 binds specifically and non-specifically to synaptobrevin. Specific binding is inhibited by a L348R mutation in Munc18-1 and enhanced by a D326K mutation designed to disrupt the 'furled conformation' of a Munc18-1 loop. Correspondingly, the activity of Munc18-1 in reconstitution assays that require Munc18-1 and Munc13-1 for membrane fusion is stimulated by the D326K mutation and inhibited by the L348R mutation. Moreover, the D326K mutation allows Munc13-1-independent fusion and leads to a gain-of-function in rescue experiments in C. elegans unc-18 nulls. Together with previous studies, our data support a model whereby Munc18-1 acts as a template for SNARE complex assembly and autoinhibition of synaptobrevin binding contributes to enabling regulation of neurotransmitter release by Munc13-1.

Article and author information

Author details

  1. Ewa Sitarska

    Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
    Competing interests
    The authors declare that no competing interests exist.
  2. Junjie Xu

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Seungmee Park

    Department of Physiology, University of Toronto, Toronto, Canada
    Competing interests
    The authors declare that no competing interests exist.
  4. Xiaoxia Liu

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Bradley Quade

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Karolina Stepien

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Kyoko Sugita

    Department of Physiology, University of Toronto, Toronto, Canada
    Competing interests
    The authors declare that no competing interests exist.
  8. Chad A Brautigam

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    Competing interests
    The authors declare that no competing interests exist.
  9. Shuzo Sugita

    Department of Physiology, University of Toronto, Toronto, Canada
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-9182-873X
  10. Josep Rizo

    Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
    For correspondence
    Jose.Rizo-Rey@UTSouthwestern.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1773-8311

Funding

National Institutes of Health (R35 NS097333)

  • Josep Rizo

Welch Foundation (I-1304)

  • Josep Rizo

Canadian Institute of Health Research (MOP-130573)

  • Shuzo Sugita

National Institutes of Health (S10OD018027)

  • Josep Rizo

National Institutes of Health (S10RR026461)

  • Josep Rizo

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, Stanford University Medical Center, United States

Publication history

  1. Received: December 15, 2016
  2. Accepted: May 4, 2017
  3. Accepted Manuscript published: May 6, 2017 (version 1)
  4. Version of Record published: June 8, 2017 (version 2)

Copyright

© 2017, Sitarska 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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  1. Ewa Sitarska
  2. Junjie Xu
  3. Seungmee Park
  4. Xiaoxia Liu
  5. Bradley Quade
  6. Karolina Stepien
  7. Kyoko Sugita
  8. Chad A Brautigam
  9. Shuzo Sugita
  10. Josep Rizo
(2017)
Autoinhibition of Munc18-1 modulates synaptobrevin binding and helps to enable Munc13-dependent regulation of membrane fusion
eLife 6:e24278.
https://doi.org/10.7554/eLife.24278

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