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ESCRT-III drives the final stages of CUPS maturation for unconventional protein secretion

  1. Amy J Curwin
  2. Nathalie Brouwers
  3. Manuel Alonso Adell
  4. David Teis
  5. Gabriele Turacchio
  6. Seetharaman Parashuraman
  7. Paolo Ronchi
  8. Vivek Malhotra  Is a corresponding author
  1. The Barcelona Institute of Science and Technology, Spain
  2. Medical University of Innsbruck, Austria
  3. National Research Council of Italy, Italy
  4. European Molecular Biology Laboratory, Germany
Research Article
  • Cited 24
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Cite this article as: eLife 2016;5:e16299 doi: 10.7554/eLife.16299

Abstract

The unconventional secretory pathway exports proteins that bypass the endoplasmic reticulum. In Saccharomyces cerevisiae, conditions that trigger Acb1 secretion via this pathway generate a Grh1 containing compartment composed of vesicles and tubules surrounded by a cup-shaped membrane and collectively called CUPS. Here we report a quantitative assay for Acb1 secretion that reveals requirements for ESCRT-I, -II, and -III but, surprisingly, without the involvement of the Vps4 AAA-ATPase. The major ESCRT-III subunit Snf7 localizes transiently to CUPS and this was accelerated in vps4Δ cells, correlating with increased Acb1 secretion. Microscopic analysis suggests that, instead of forming intraluminal vesicles with the help of Vps4, ESCRT-III/Snf7 promotes direct engulfment of preexisting Grh1 containing vesicles and tubules into a saccule to generate a mature Acb1 containing compartment. This novel multivesicular / multilamellar compartment, we suggest represents the stable secretory form of CUPS that is competent for the release of Acb1 to cells exterior.

Article and author information

Author details

  1. Amy J Curwin

    Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
    Competing interests
    No competing interests declared.
  2. Nathalie Brouwers

    Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
    Competing interests
    No competing interests declared.
  3. Manuel Alonso Adell

    Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
    Competing interests
    No competing interests declared.
  4. David Teis

    Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
    Competing interests
    No competing interests declared.
  5. Gabriele Turacchio

    Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy
    Competing interests
    No competing interests declared.
  6. Seetharaman Parashuraman

    Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy
    Competing interests
    No competing interests declared.
  7. Paolo Ronchi

    Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany
    Competing interests
    No competing interests declared.
  8. Vivek Malhotra

    Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain
    For correspondence
    vivek.malhotra@crg.eu
    Competing interests
    Vivek Malhotra, Senior editor, eLife.

Reviewing Editor

  1. Randy Schekman, Howard Hughes Medical Institute, University of California, Berkeley, United States

Publication history

  1. Received: March 23, 2016
  2. Accepted: April 25, 2016
  3. Accepted Manuscript published: April 26, 2016 (version 1)
  4. Accepted Manuscript updated: April 27, 2016 (version 2)
  5. Version of Record published: May 16, 2016 (version 3)

Copyright

© 2016, Curwin 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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