Abstract

Sec1/Munc18-family (SM) proteins are required for SNARE-mediated membrane fusion, but their mechanism(s) of action remain controversial. Using single-molecule force spectroscopy, we found that the SM protein Munc18-1 catalyzes step-wise zippering of three synaptic SNAREs (syntaxin, VAMP2, and SNAP-25) into a four-helix bundle. Catalysis requires formation of an intermediate template complex in which Munc18-1 juxtaposes the N-terminal regions of the SNARE motifs of syntaxin and VAMP2, while keeping their C-terminal regions separated. SNAP-25 binds the templated SNAREs to induce full SNARE zippering. Munc18-1 mutations modulate the stability of the template complex in a manner consistent with their effects on membrane fusion, indicating that chaperoned SNARE assembly is essential for exocytosis. Two other SM proteins, Munc18-3 and Vps33, similarly chaperone SNARE assembly via a template complex, suggesting that SM protein mechanism is conserved.

Data availability

All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 2-10.

Article and author information

Author details

  1. Junyi Jiao

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

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

    Department of Molecular Biology, Princeton University, Princeton, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-1897-0510
  4. Richard W Baker

    Department of Molecular Biology, Princeton University, Princeton, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Yonggang Xu

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

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

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

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

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

    Department of Molecular Biology, Princeton University, Princeton, United States
    Competing interests
    The authors declare that no competing interests exist.
  11. Frederick M Hughson

    Department of Molecular Biology, Princeton University, Princeton, United States
    For correspondence
    hughson@princeton.edu
    Competing interests
    The authors declare that no competing interests exist.
  12. Yongli Zhang

    Department of Cell Biology, Yale University School of Medicine, New Haven, United States
    For correspondence
    yongli.zhang@yale.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7079-7973

Funding

National Institute of General Medical Sciences (R01GM093341)

  • Yongli Zhang

National Institute of General Medical Sciences (R01GM120193)

  • Yongli Zhang

National Institute of General Medical Sciences (R01GM071574)

  • Frederick M Hughson

National Institute of General Medical Sciences (T32GM007223)

  • Junyi Jiao

Deutsche Forschungsgemeinschaft (PO2195/1-1)

  • Sarah A Port

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

Reviewing Editor

  1. Josep Rizo, University of Texas Southwestern Medical Center, United States

Version history

  1. Received: September 6, 2018
  2. Accepted: December 11, 2018
  3. Accepted Manuscript published: December 12, 2018 (version 1)
  4. Version of Record published: January 4, 2019 (version 2)

Copyright

© 2018, Jiao 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. Junyi Jiao
  2. Mengze He
  3. Sarah A Port
  4. Richard W Baker
  5. Yonggang Xu
  6. Hong Qu
  7. Yujian Xiong
  8. Yukun Wang
  9. Huaizhou Jin
  10. Travis J Eisemann
  11. Frederick M Hughson
  12. Yongli Zhang
(2018)
Munc18-1 catalyzes neuronal SNARE assembly by templating SNARE association
eLife 7:e41771.
https://doi.org/10.7554/eLife.41771

Share this article

https://doi.org/10.7554/eLife.41771

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