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 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.
Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.|Universitat Pompeu Fabra, Barcelona, Spain.
Amy J
0000-0003-1086-2483
AJ
Curwin
Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.|Universitat Pompeu Fabra, Barcelona, Spain.
Nathalie
0000-0002-9808-9394
N
Brouwers
Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
Manuel
M
Alonso Y Adell
Division of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
David
0000-0002-8181-0253
D
Teis
Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy.
Gabriele
G
Turacchio
Institute of Protein Biochemistry, National Research Council of Italy, Naples, Italy.
Seetharaman
S
Parashuraman
Electron Microscopy Core Facility, European Molecular Biology Laboratory, Heidelberg, Germany.
Paolo
P
Ronchi
Centre for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.|Universitat Pompeu Fabra, Barcelona, Spain.|Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
Vivek
0000-0001-6198-7943
V
Malhotra
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
C492820:ACB1 protein, S cerevisiae; D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C083890:SNF7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C107528:VPS4 protein, S cerevisiae; D000251:Adenosine Triphosphatases
CUPS; ESCRTs; S. cerevisiae; cell biology; unconventional secretion