A distinct tethering step is vital for vacuole membrane fusion

  1. Michael Zick
  2. William T Wickner  Is a corresponding author
  1. Geisel School of Medicine at Dartmouth, United States

Abstract

Past experiments with reconstituted proteoliposomes, employing assays that infer membrane fusion from fluorescent lipid dequenching, have suggested that vacuolar SNAREs alone suffice to catalyze membrane fusion in vitro. While we could replicate these results, we detected very little fusion with the more rigorous assay of lumenal compartment mixing. Exploring the discrepancies between lipid-dequenching and content-mixing assays, we surprisingly found that the disposition of the fluorescent lipids with respect to SNAREs had a striking effect. Without other proteins, the association of SNAREs in trans causes lipid dequenching that cannot be ascribed to fusion or hemifusion. Tethering of the SNARE-bearing proteoliposomes was required for efficient lumenal compartment mixing. While the physiological HOPS tethering complex caused a few-fold increase of trans-SNARE association, the rate of content mixing increased more than 100-fold. Thus tethering has a role in promoting membrane fusion that extends beyond simply increasing the amount of total trans-SNARE complex.

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Author details

  1. Michael Zick

    Geisel School of Medicine at Dartmouth, Hanover, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. William T Wickner

    Geisel School of Medicine at Dartmouth, Hanover, United States
    For correspondence
    William.T.Wickner@dartmouth.edu
    Competing interests
    The authors declare that no competing interests exist.

Copyright

© 2014, Zick & Wickner

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. Michael Zick
  2. William T Wickner
(2014)
A distinct tethering step is vital for vacuole membrane fusion
eLife 3:e03251.
https://doi.org/10.7554/eLife.03251

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https://doi.org/10.7554/eLife.03251