title: Disturbance of sphingolipid biosynthesis abrogates the signaling of Mss4, phosphatidylinositol-4-phosphate 5-kinase, in yeast.
abstract: The functional relationships between phosphoinositides and sphingolipids have not been well characterized to date. ISP-1/myriocin is a potent inhibitor of sphingolipid biosynthesis and induces severe growth defects in eukaryotic cells because of the sphingolipid deprivation. We characterized a novel multicopy suppressor gene of ISP-1-mediated cell death in yeast, MSS4. MSS4 encodes a phosphatidylinositol-4-phosphate 5-kinase that synthesizes phosphatidylinositol (4,5)-bisphosphate (PI4,5P(2)). We demonstrate here that ISP-1 treatment of yeast causes defects both in the activity and subcellular localization of Mss4. The effect of the Mss4 defect on the downstream signaling was examined, because interaction between the Mss4 product, PI4,5P(2), and the pleckstrin-homology domain of Rom2 mediates recruitment of Rom2 to the membrane, which is the crucial step for subsequent Rho1/2 activation. Indeed, failure of Rom2 recruitment was observed in ISP-1-treated cells as well as in csg2-deleted cells, which have reduced mannosylated inositolphosphorylceramide. These data suggested that proper sphingolipids are required for the signaling pathway involving Mss4.
authors.affiliation: Laboratory of Membrane Biochemistry and Biophysics, Graduate School of Biostudies, Kyoto University, Yoshida Shimoadachi, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Hiromu
authors.initials: H
authors.lastname: Takematsu
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yamaji
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Hiramoto
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Kozutsumi
mesh_terms: D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013107:Sphingolipids / Q000037:antagonists & inhibitors / Q000096:biosynthesis*
chemical_list: D005229:Fatty Acids, Monounsaturated; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; C489795:MSS4 protein, S cerevisiae; C001996:thermozymocidin