This Article Full Text (PDF) Other Versions of this Article: EC.00211-07v1 6/12/2343    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Onishi, M. Articles by Tachikawa, H. Search for Related Content PubMed PubMed Citation Articles by Onishi, M. Articles by Tachikawa, H.

 Previous Article  |  Next Article 

Eukaryotic Cell doi:10.1128/EC.00211-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Fission yeast Sst4p, a conserved Vps27/Hrs homolog, functions downstream of PtdIns 3-kinase Pik3p to mediate proper spore formation

Laboratory of Biological Chemistry, Graduate School of Agricultural and Life Science, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan; Department of Life Sciences, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan

^* To whom correspondence should be addressed. Email: ayfukui{at}mail.ecc.u-tokyo.ac.jp.

	Abstract

Sporulation of the fission yeast Schizosaccharomyces pombe is a developmental process that generates gametes and that includes the formation of spore envelope precursors called the forespore membranes. Assembly and development of forespore membranes require vesicular trafficking from other intracellular membrane compartments. We have shown that PtdIns 3-kinase is required for efficient and proper development of forespore membranes. The role of a FYVE domain protein, Sst4p, a homolog of Vps27p/Hrs, as a downstream factor for PtdIns 3-kinase in sporulation was investigated. sst4 asci formed spores with oval-shaped morphology and with reduced viability compared to the wild-type spores. The extension of forespore membranes was inefficient, and bubble-like structures emerged from the leading edges of the forespore membranes. Sst4p localization was examined using fluorescent protein fusions, and was found adjacent to the forespore membranes during sporulation. The localization and function of Sst4p were dependent on its FYVE domain and on PtdIns 3-kinase. Sst4p co-localized and interacted with Hse1p, a homolog of S. cerevisiae Hse1p and of mammalian STAM. Mutations in all three UIM domains of the Sst4p/Hse1p complex resulted in formation of spores with abnormal morphology. These results suggest that Sst4p is a downstream factor of PtdIns 3-kinase and functions in forespore membrane formation.