1. Biochemistry and Chemical Biology

Sec17/Sec18 can support membrane fusion without help from completion of SNARE zippering

  1. Hongki Song
  2. Thomas L Torng
  3. Amy S Orr
  4. Axel T Brunger
  5. William T Wickner  Is a corresponding author
  1. Geisel School of Medicine at Dartmouth, United States
  2. Stanford University, United States
https://doi.org/10.7554/eLife.67578
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  1. Hongki Song
  2. Thomas L Torng
  3. Amy S Orr
  4. Axel T Brunger
  5. William T Wickner
(2021)
Sec17/Sec18 can support membrane fusion without help from completion of SNARE zippering
eLife 10:e67578.
https://doi.org/10.7554/eLife.67578
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Abstract

Membrane fusion requires R-, Qa-, Qb-, and Qc-family SNAREs that zipper into RQaQbQc coiled coils, driven by the sequestration of apolar amino acids. Zippering has been thought to provide all the force driving fusion. Sec17/aSNAP can form an oligomeric assembly with SNAREs with the Sec17 C-terminus bound to Sec18/NSF, the central region bound to SNAREs, and a crucial apolar loop near the N-terminus poised to insert into membranes. We now report that Sec17 and Sec18 will drive robust fusion without requiring zippering completion. Zippering-driven fusion is blocked by deleting the C-terminal quarter of any Q-SNARE domain or by replacing the apolar amino acids of the Qa-SNARE which face the center of the 4-SNARE coiled coils with polar residues. These blocks, singly or combined, are bypassed by Sec17 and Sec18, and SNARE-dependent fusion is restored without help from completing zippering.

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All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 1, 2, 3 4, 5, and 6.

The following previously published data sets were used

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Author details

  1. Hongki Song

    Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, United States
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3761-5434

  2. Thomas L Torng

    Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, United States
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2295-2777

  3. Amy S Orr

    Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, United States
    Competing interests
    No competing interests declared.

  4. Axel T Brunger

    Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
    Competing interests
    Axel T Brunger, Reviewing editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5121-2036

  5. William T Wickner

    Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, United States
    For correspondence
    William.T.Wickner@dartmouth.edu
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-8431-0468

Funding

National Institutes of Health (R35GM118037)

  • William T Wickner

National Institutes of Health (R37MH63105)

  • Axel T Brunger

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

Copyright

© 2021, Song 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. Hongki Song
  2. Thomas L Torng
  3. Amy S Orr
  4. Axel T Brunger
  5. William T Wickner
(2021)
Sec17/Sec18 can support membrane fusion without help from completion of SNARE zippering
eLife 10:e67578.
https://doi.org/10.7554/eLife.67578

Share this article

https://doi.org/10.7554/eLife.67578

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Further reading

    1. Biochemistry and Chemical Biology

    Fusion of tethered membranes can be driven by Sec18/NSF and Sec17/αSNAP without HOPS

    Hongki Song, William T Wickner
    Research Advance Updated

    Yeast vacuolar membrane fusion has been reconstituted with R, Qa, Qb, and Qc-family SNAREs, Sec17/αSNAP, Sec18/NSF, and the hexameric HOPS complex. HOPS tethers membranes and catalyzes SNARE assembly into RQaQbQc trans-complexes which zipper through their SNARE domains to promote fusion. Previously, we demonstrated that Sec17 and Sec18 can bypass the requirement of complete zippering for fusion (Song et al., 2021), but it has been unclear whether this activity of Sec17 and Sec18 is directly coupled to HOPS. HOPS can be replaced for fusion by a synthetic tether when the three Q-SNAREs are pre-assembled. We now report that fusion intermediates with arrested SNARE zippering, formed with a synthetic tether but without HOPS, support Sec17/Sec18-triggered fusion. This zippering-bypass fusion is thus a direct result of Sec17 and Sec18 interactions: with each other, with the platform of partially zippered SNAREs, and with the apposed tethered membranes. As these fusion elements are shared among all exocytic and endocytic traffic, Sec17 and Sec18 may have a general role in directly promoting fusion.

    1. Biochemistry and Chemical Biology

    Membrane Fusion: Molecular machinery turns full circle

    Josep Rizo, Klaudia Jaczynska, Karolina P Stepien
    Insight

    Two proteins called Sec17 and Sec18 may have a larger role in membrane fusion than is commonly assumed in textbook models.