Evidence for a Nonendosomal Function of the Saccharomyces cerevisiae ESCRT-III-Like Protein Chm7.
Endosomal sorting complex required for transport (ESCRT) proteins are involved in a number of cellular processes, such as endosomal protein sorting, HIV budding, cytokinesis, plasma membrane repair, and resealing of the nuclear envelope during mitosis. Here we explored the function of a noncanonical member of the ESCRT-III protein family, the Saccharomyces cerevisiae ortholog of human CHMP7. Very little is known about this protein. In silico analysis predicted that Chm7 (yeast ORF YJL049w) is a fusion of an ESCRT-II and ESCRT-III-like domain, which would suggest a role in endosomal protein sorting. However, our data argue against a role of Chm7 in endosomal protein sorting. The turnover of the endocytic cargo protein Ste6 and the vacuolar protein sorting of carboxypeptidase S (CPS) were not affected by CHM7 deletion, and Chm7 also responded very differently to a loss in Vps4 function compared to a canonical ESCRT-III protein. Our data indicate that the Chm7 function could be connected to the endoplasmic reticulum (ER). In line with a function at the ER, we observed a strong negative genetic interaction between the deletion of a gene function (APQ12) implicated in nuclear pore complex assembly and messenger RNA (mRNA) export and the CHM7 deletion. The patterns of genetic interactions between the APQ12 deletion and deletions of ESCRT-III genes, two-hybrid interactions, and the specific localization of mCherry fusion proteins are consistent with the notion that Chm7 performs a novel function at the ER as part of an alternative ESCRT-III complex.
Institut für Lebensmittelwissenschaft und Biotechnologie, Fg. Hefegenetik und Gärungstechnologie, Universität Hohenheim, 70599 Stuttgart, Germany.
Iva
I
Bauer
Institut für Lebensmittelwissenschaft und Biotechnologie, Fg. Hefegenetik und Gärungstechnologie, Universität Hohenheim, 70599 Stuttgart, Germany.
Thomas
T
Brune
Department of Molecular and Cellular Biology, University of Guelph, Ontario, Canada N1G 2W1.
Richard
R
Preiss
Institut für Lebensmittelwissenschaft und Biotechnologie, Fg. Hefegenetik und Gärungstechnologie, Universität Hohenheim, 70599 Stuttgart, Germany ralf.koelling@uni-hohenheim.de.
Ralf
R
Kölling
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D004705:Endocytosis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D048868:Adaptor Proteins, Signal Transducing; C000610602:Chm7 protein, S cerevisiae; D056827:Endosomal Sorting Complexes Required for Transport; C489277:STE6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins
ESCRT-III; endoplasmic reticulum; endosome; multivesicular body; protein degradation