title: STT4 is an essential phosphatidylinositol 4-kinase that is a target of wortmannin in Saccharomyces cerevisiae.
abstract: Wortmannin is a natural product that inhibits signal transduction. One target of wortmannin in mammalian cells is the 110-kDa catalytic subunit of phosphatidylinositol 3-kinase (PI 3-kinase). We show that wortmannin is toxic to the yeast Saccharomyces cerevisiae and present genetic and biochemical evidence that a phosphatidylinositol 4-kinase (PI 4-kinase), STT4, is a target of wortmannin in yeast. In a strain background in which stt4 mutants are rescued by osmotic support with sorbitol, the toxic effects of wortmannin are similarly prevented by sorbitol. In contrast, in a different strain background, STT4 is essential under all conditions and wortmannin toxicity is not mitigated by sorbitol. Overexpression of STT4 confers wortmannin resistance, but overexpression of PIK1, a related PI 4-kinase, does not. In vitro, the PI 4-kinase activity of STT4, but not of PIK1, was potently inhibited by wortmannin. Overexpression of the phosphatidylinositol 4-phosphate 5-kinase homolog MSS4 conferred wortmannin resistance, as did deletion of phospholipase C-1. These observations support a model for a phosphatidylinositol metabolic cascade involving STT4, MSS4, and phospholipase C-1 and provide evidence that an essential product of this pathway is the lipid phosphatidylinositol 4,5-bisphosphate.
authors.affiliation: Department of Genetics, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: N S
authors.initials: NS
authors.lastname: Cutler
authors.forename: J
authors.initials: J
authors.lastname: Heitman
authors.forename: M E
authors.initials: ME
authors.lastname: Cardenas
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics; D000730:Androstadienes / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins; D010738:Type C Phospholipases / Q000235:genetics; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D004791:Enzyme Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D019870:1-Phosphatidylinositol 4-Kinase; C441760:PIK1 protein, S cerevisiae; D010738:Type C Phospholipases; D000077191:Wortmannin