Hawkins P T, Stephens L R, Piggott J R
Smith Kline Beecham, Welwyn, Herts, United Kingdom.
J Biol Chem. 1993 Feb 15;268(5):3374-83.
When cultures of Saccharomyces cerevisiae are grown to stationary phase in medium containing [3H] inositol, significant amounts of radioactivity can be detected in phosphatidylinositol, phosphatidylinositol 3-phosphate, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate. Addition of glucose to such cultures results in the generation of [3H]glycerophosphoinositol, [3H]glycerophosphoinositol 4-phosphate, and [3H]glycerophosphoinositol 4,5-bisphosphate in the extracellular medium. We found no evidence, however, for the stimulated formation of other inositol polyphosphates. This result suggests that glucose does not stimulate the "phospholipase C" signalling pathway established in higher eukaryotic cells but, in contrast, stimulates specific phospholipases A or B. A variety of cell division cycle (cdc) mutants have been studied to investigate the relationship between cell cycle progression and inositol metabolism in S. cerevisiae. Mutants which are defective for completion of cell cycle "START" (i.e. commitment to mitosis) show reduced formation of glycerophosphoinositol 4-phosphate and glycerophosphoinositol 4,5-bisphosphate in response to glucose. In contrast, cdc mutants which are defective in post-"START" processes show a larger glucose response than wild type cells. These results suggest that deacylation of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate may be coordinated with cell cycle control in S. cerevisiae.
当酿酒酵母培养物在含有[³H]肌醇的培养基中生长至稳定期时，在磷脂酰肌醇、磷脂酰肌醇3 - 磷酸、磷脂酰肌醇4 - 磷酸和磷脂酰肌醇4,5 - 二磷酸中可检测到大量放射性。向此类培养物中添加葡萄糖会导致细胞外培养基中产生[³H]甘油磷酸肌醇、[³H]甘油磷酸肌醇4 - 磷酸和[³H]甘油磷酸肌醇4,5 - 二磷酸。然而，我们没有发现其他肌醇多磷酸形成受到刺激的证据。这一结果表明，葡萄糖不会刺激高等真核细胞中建立的“磷脂酶C”信号通路，相反，它会刺激特定的磷脂酶A或B。已对多种细胞分裂周期（cdc）突变体进行了研究，以探讨酿酒酵母细胞周期进程与肌醇代谢之间的关系。在细胞周期“起始点”（即进入有丝分裂的承诺）完成方面存在缺陷的突变体，对葡萄糖的反应中甘油磷酸肌醇4 - 磷酸和甘油磷酸肌醇4,5 - 二磷酸的形成减少。相比之下，在“起始点”后过程中存在缺陷的cdc突变体比野生型细胞表现出更大的葡萄糖反应。这些结果表明，磷脂酰肌醇4 - 磷酸和磷脂酰肌醇4,5 - 二磷酸的去酰化作用可能与酿酒酵母的细胞周期控制相协调。
