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

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 collective...

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Bibliographic Details
Published in:eLife 2016-04, Vol.5
Main Authors: Curwin, Amy J, Brouwers, Nathalie, Alonso Y Adell, Manuel, Teis, David, Turacchio, Gabriele, Parashuraman, Seetharaman, Ronchi, Paolo, Malhotra, Vivek
Format: Article
Language:English
Subjects:
Adenosine triphosphatase
Adenosine Triphosphatases - genetics
Adenosine Triphosphatases - metabolism
Amino acids
Biosynthesis
Carrier Proteins - metabolism
Cell Biology
CUPS
Endoplasmic reticulum
Endosomal Sorting Complexes Required for Transport - genetics
Endosomal Sorting Complexes Required for Transport - metabolism
ESCRTs
Gene Deletion
Membranes
Microscopy
Observations
Protein-protein interactions
Proteins
Saccharomyces cerevisiae - genetics
Saccharomyces cerevisiae - metabolism
Saccharomyces cerevisiae Proteins - genetics
Saccharomyces cerevisiae Proteins - metabolism
Saccule
Secretion
Tubules
unconventional secretion
Vesicles
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Summary: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.
ISSN:2050-084X
2050-084X
DOI:10.7554/eLife.16299