Diaz-Laviada I, Larrodera P, Diaz-Meco M T, Cornet M E, Guddal P H, Johansen T, Moscat J
Medicine y Cirugía Experimental, Hospital General Gregorio Marañón, Madrid, Spain.
EMBO J. 1990 Dec;9(12):3907-12. doi: 10.1002/j.1460-2075.1990.tb07611.x.
The products of ras and src oncogenes are thought to be important components in pathways regulating cell proliferation and differentiation. In fibroblasts transformed by these oncogenes, increased diacylglycerol levels have been found which most probably arise from activation of the turnover of phosphatidylcholine. Diacylglycerol is a key activator of protein kinase C whose role in cell growth and transformation has been proposed. We demonstrate here by using immunochemical techniques that transformation by ras or src oncogenes is associated with permanent translocation of protein kinase C to the cytoplasmic membrane. However, no down-regulation of the enzyme is observed despite its permanent activation in these transformants. Importantly, the lack of down-regulation observed in ras and src transformed cell lines is mimicked by chronic treatment of NIH 3T3 fibroblasts with exogenous Bacillus cereus phosphatidylcholine-hydrolysing phospholipase C, but not with phorbol myristate acetate or exogenous Bacillus thuringiensis phosphatidylinositol-hydrolysing phospholipase C. These results strongly suggest that diacylglycerol derived from phosphatidylcholine but not from phosphoinositide turnover is responsible for the atypical regulation of protein kinase C in cell lines transformed by ras and src oncogenes.
ras和src癌基因的产物被认为是调节细胞增殖和分化途径中的重要组成部分。在由这些癌基因转化的成纤维细胞中，已发现二酰基甘油水平升高，这很可能源于磷脂酰胆碱周转的激活。二酰基甘油是蛋白激酶C的关键激活剂，其在细胞生长和转化中的作用已被提出。我们在此通过免疫化学技术证明，ras或src癌基因介导的转化与蛋白激酶C向细胞质膜的永久性易位有关。然而，尽管该酶在这些转化细胞中被永久激活，但未观察到其下调。重要的是，用外源蜡样芽孢杆菌磷脂酰胆碱水解磷脂酶C长期处理NIH 3T3成纤维细胞可模拟在ras和src转化细胞系中观察到的下调缺失，而用佛波醇肉豆蔻酸酯乙酸盐或外源苏云金芽孢杆菌磷脂酰肌醇水解磷脂酶C处理则不能。这些结果强烈表明，来源于磷脂酰胆碱而非磷酸肌醇周转的二酰基甘油是ras和src癌基因转化细胞系中蛋白激酶C非典型调节的原因。
