Huang M, Chida K, Kamata N, Nose K, Kato M, Homma Y, Takenawa T, Kuroki T
Department of Cancer Cell Research, University of Tokyo, Japan.
J Biol Chem. 1988 Dec 5;263(34):17975-80.
The inositol phospholipid metabolism is one of the main pathways of signal transduction in cells. We measured the activities of its key enzymes in v-Ha-ras-transformed 208F rat fibroblasts. In the ras-transformed clones, incorporation of [32P]Pi into intermediates of the inositol phospholipid metabolism was stimulated. The activities of phosphatidylinositol and phosphatidylinositol-4-phosphate kinases in the transformed clones were about 35-50% more than in untransformed cells, indicating increased inositol phospholipid metabolism. However, the activity of diacylglycerol kinase in their membrane fraction was 25-35% less than that of untransformed cells, although the total diacylglycerol kinase activity did not change. The imbalance of these kinases could constitute one of the main reasons leading to the increased level of inositol phosphates and the accumulation of diacylglycerol to 2-2.2 times that in control 208F cells. Phosphatidylinositol-4,5-bisphosphate-phospholipase C activity did not change on the transformation when assayed under various conditions. The increased level of diacylglycerol caused intracellular translocation, activation, and down-regulation of protein kinase C changes which may be one of the essential events in transformation by the v-Ha-ras gene.
肌醇磷脂代谢是细胞信号转导的主要途径之一。我们测定了v-Ha-ras转化的208F大鼠成纤维细胞中其关键酶的活性。在ras转化的克隆中，[32P]Pi掺入肌醇磷脂代谢中间体的过程受到刺激。转化克隆中磷脂酰肌醇和磷脂酰肌醇-4-磷酸激酶的活性比未转化细胞高约35-50%，表明肌醇磷脂代谢增加。然而，尽管二酰基甘油激酶的总活性没有变化，但其膜部分的活性比未转化细胞低25-35%。这些激酶的失衡可能是导致肌醇磷酸水平升高以及二酰基甘油积累至对照208F细胞的2-2.2倍的主要原因之一。在各种条件下测定时，磷脂酰肌醇-4,5-二磷酸-磷脂酶C的活性在转化时没有变化。二酰基甘油水平的升高导致蛋白激酶C发生细胞内转位、激活和下调变化，这可能是v-Ha-ras基因转化过程中的关键事件之一。
