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Regulation of the transport and protein levels of the inositol phosphorylceramide mannosyltransferases Csg1 and Csh1 by the Ca2+ binding protein Csg2

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Title: Regulation of the transport and protein levels of the inositol phosphorylceramide mannosyltransferases Csg1 and Csh1 by the Ca2+ binding protein Csg2
Authors: Uemura, Satoshi Browse this author
Kihara, Akio Browse this author →KAKEN DB
Iwaki, Soichiro Browse this author
Inokuchi, Jin-ichi Browse this author
Igarashi, Yasuyuki Browse this author →KAKEN DB
Issue Date: 23-Mar-2007
Publisher: American Society for Biochemistry and Molecular Biology
Journal Title: Journal of Biological Chemistry
Volume: 282
Issue: 12
Start Page: 8613
End Page: 8621
Publisher DOI: 10.1074/jbc.M606649200
PMID: 17220303
Abstract: Complex sphingolipids in yeast are known to function in cellular adaptation to environmental changes. One of the yeast complex sphingolipids, mannosylinositol phosphorylceramide (MIPC), is produced by the redundant inositol phosphorylceramide (IPC) mannosyltransferases Csg1 and Csh1. The Ca2+-binding protein Csg2 can form a complex with either Csg1 or Csh1 and is considered to act as a regulatory subunit. However, the role of Csg2 in MIPC synthesis has remained unclear. In this study, we found that Csg1 and Csh1 are N-glycosylated with core-type and mannan-type structures, respectively. Further identification of the glycosylated residues suggests that both Csg1 and Csh1 exhibit membrane topology with their C termini in the cytosol and their mannosyltransferase domains in the lumen. After complexing with Csg2, both Csg1 and Csh1 function in the Golgi, and then are delivered to the vacuole for degradation. However, uncomplexed Csh1 cannot exit from the endoplasmic reticulum. We also demonstrated that Ca2+ stimulates IPC-to-MIPC conversion, because of a Csg2-dependent increase in Csg1 levels. Thus, Csg2 has several regulatory functions for Csg1 and Csh1, including stability, transport, and gene expression.
Rights: Copyright © 2007 by the American Society for Biochemistry and Molecular Biology
Type: article (author version)
URI: http://hdl.handle.net/2115/22536
Appears in Collections:薬学研究院 (Faculty of Pharmaceutical Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 木原 章雄

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