Cutler N S, Heitman J, Cardenas M E
Department of Genetics, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Biol Chem. 1997 Oct 31;272(44):27671-7. doi: 10.1074/jbc.272.44.27671.
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.
渥曼青霉素是一种抑制信号转导的天然产物。渥曼青霉素在哺乳动物细胞中的一个作用靶点是磷脂酰肌醇3激酶（PI 3激酶）的110 kDa催化亚基。我们发现渥曼青霉素对酿酒酵母有毒性，并提供了遗传学和生物化学证据，表明磷脂酰肌醇4激酶（PI 4激酶）STT4是渥曼青霉素在酵母中的一个作用靶点。在一个stt4突变体通过山梨醇渗透支持得以挽救的菌株背景中，山梨醇同样能阻止渥曼青霉素的毒性作用。相比之下，在另一种菌株背景中，STT4在所有条件下都是必需的，渥曼青霉素的毒性不会因山梨醇而减轻。STT4的过表达赋予了对渥曼青霉素的抗性，但相关的PI 4激酶PIK1的过表达则没有。在体外，渥曼青霉素能有效抑制STT4的PI 4激酶活性，但不能抑制PIK1的活性。磷脂酰肌醇4磷酸5激酶同源物MSS4的过表达赋予了对渥曼青霉素的抗性，磷脂酶C-1的缺失也有同样的效果。这些观察结果支持了一个涉及STT4、MSS4和磷脂酶C-1的磷脂酰肌醇代谢级联模型，并提供了证据表明该途径的一个必需产物是脂质磷脂酰肌醇4,5-二磷酸。
