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1 Department of Life Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan
2 Research Center, Asahi Glass Co. Ltd, Kanagawa, Yokohama 221-8755, Japan
3 Laboratory of Biological Chemistry, Graduate School of Agricultural and Life Science, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
4 Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, Kowakae 3-4-1, Higashi-Osaka 577-8502, Japan
Correspondence
Kaoru Takegawa
takegawa{at}ag.kagawa-u.ac.jp
The multivesicular body (MVB) sorting pathway is required for a number of biological processes, including downregulation of cell-surface proteins and protein sorting into the vacuolar lumen. The function of this pathway requires endosomal sorting complexes required for transport (ESCRT) composed of class E vacuolar protein sorting (Vps) proteins in Saccharomyces cerevisiae, many of which are conserved in Schizosaccharomyces pombe. Of these, sst4/vps27 (homologous to VPS27) and sst6 (similar to VPS23) have been identified as suppressors of sterility in ste12
(sst), although their functions have not been uncovered to date. In this report, these two sst genes are shown to be required for vacuolar sorting of carboxypeptidase Y (CPY) and an MVB marker, the ubiquitin–GFP–carboxypeptidase S (Ub–GFP–CPS) fusion protein, despite the lack of the ubiquitin E2 variant domain in Sst6p. Disruption mutants of a variety of other class E vps homologues also had defects in sorting of CPY and Ub–GFP–CPS. Sch. pombe has a mammalian AMSH homologue, sst2. Phenotypic analyses suggested that Sst2p is a class E Vps protein. Taken together, these results suggest that sorting into multivesicular bodies is dependent on class E Vps proteins, including Sst2p, in Sch. pombe.
Supplementary methods, electron micrographs and fusion protein figures are available with the online version of this paper.
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M. Onishi, M. Iida, T. Koga, S. Yamada, A. Hirata, T. Iwaki, K. Takegawa, Y. Fukui, and H. Tachikawa Schizosaccharomyces pombe Sst4p, a Conserved Vps27/Hrs Homolog, Functions Downstream of Phosphatidylinositol 3-Kinase Pik3p To Mediate Proper Spore Formation Eukaryot. Cell, December 1, 2007; 6(12): 2343 - 2353. [Abstract] [Full Text] [PDF] |
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