Synaptotagmin-7 places dense-core vesicles at the cell membrane to promote Munc13-2- and Ca2+-dependent priming

  1. Bassam Tawfik
  2. Joana S Martins
  3. Sébastien Houy
  4. Cordelia Imig
  5. Paulo S Pinheiro
  6. Sonja M Wojcik
  7. Nils Brose
  8. Benjamin H Cooper
  9. Jakob Balslev Sørensen  Is a corresponding author
  1. University of Copenhagen, Denmark
  2. Max Planck Institute of Experimental Medicine, Germany

Abstract

Synaptotagmins confer calcium-dependence to the exocytosis of secretory vesicles, but how coexpressed synaptotagmins interact remains unclear. We find that synaptotagmin-1 and synaptotagmin-7 when present alone act as standalone fast and slow Ca2+-sensors for vesicle fusion in mouse chromaffin cells. When present together, synaptotagmin-1 and synaptotagmin-7 are found in largely non-overlapping clusters on dense-core vesicles. Synaptotagmin-7 stimulates Ca2+-dependent vesicle priming and inhibits depriming, and it promotes ubMunc13-2- and phorbolester-dependent priming, especially at low resting calcium concentrations. The priming effect of synaptotagmin-7 increases the number of vesicles fusing via synaptotagmin-1, while negatively affecting their fusion speed, indicating both synergistic and competitive interactions between synaptotagmins. Synaptotagmin-7 places vesicles in close membrane apposition (<6 nm); without it, vesicles accumulate out of reach of the fusion complex (20-40 nm). We suggest that a synaptotagmin-7-dependent movement toward the membrane is involved in Munc13-2/phorbolester/Ca2+-dependent priming as a prelude to fast and slow exocytosis triggering.

Data availability

All data generated or analysed during this study are or will be included in the manuscript and supporting files.

Article and author information

Author details

  1. Bassam Tawfik

    Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1193-8494
  2. Joana S Martins

    Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
    Competing interests
    No competing interests declared.
  3. Sébastien Houy

    Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-3639-1931
  4. Cordelia Imig

    Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7351-8706
  5. Paulo S Pinheiro

    Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
    Competing interests
    No competing interests declared.
  6. Sonja M Wojcik

    Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
    Competing interests
    No competing interests declared.
  7. Nils Brose

    Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
    Competing interests
    Nils Brose, Reviewing editor, eLife.
  8. Benjamin H Cooper

    Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
    Competing interests
    No competing interests declared.
  9. Jakob Balslev Sørensen

    Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
    For correspondence
    jakobbs@sund.ku.dk
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5465-3769

Funding

University of Copenhagen 2016 excellence program (KU2016)

  • Jakob Balslev Sørensen

Novo Nordisk Foundation (NNF19OC0058298)

  • Jakob Balslev Sørensen

Lundbeckfonden (R221-2016-1202)

  • Jakob Balslev Sørensen

Independent Research Fund Denmark (0134-00141A)

  • Jakob Balslev Sørensen

Lundbeckfonden (R34-A3740)

  • Paulo S Pinheiro

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

Ethics

Animal experimentation: Mice were kept in an AAALAC-accredited stable at the University of Copenhagen operating a 12h/12h light/dark cycle with access to water and food ad libitum. Permission to keep and breed KO mice were obtained from the Danish Animal Experiments Inspectorate (permissions 2006/562-43 and 2018-15-0202-00157).

Reviewing Editor

  1. Axel T Brunger, Stanford University, United States

Version history

  1. Received: November 2, 2020
  2. Accepted: March 19, 2021
  3. Accepted Manuscript published: March 22, 2021 (version 1)
  4. Version of Record published: March 31, 2021 (version 2)

Copyright

© 2021, Tawfik 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. Bassam Tawfik
  2. Joana S Martins
  3. Sébastien Houy
  4. Cordelia Imig
  5. Paulo S Pinheiro
  6. Sonja M Wojcik
  7. Nils Brose
  8. Benjamin H Cooper
  9. Jakob Balslev Sørensen
(2021)
Synaptotagmin-7 places dense-core vesicles at the cell membrane to promote Munc13-2- and Ca2+-dependent priming
eLife 10:e64527.
https://doi.org/10.7554/eLife.64527

Share this article

https://doi.org/10.7554/eLife.64527

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