Dislodgment and accelerated degradation of Ras
Dislodgment and accelerated degradation of Ras
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DOI：
10.1021/bi972032d
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发表时间：
1998-02-03
期刊：
影响因子：
2.9
通讯作者：
Kloog, Y
中科院分区：
文献类型：
--
作者：
Haklai, R;Weisz, MG;Kloog, Y
转化活性所需的RAS癌蛋白的膜锚定依赖于其羧基末端的法尼基半胱氨酸。S反式，反式法尼基硫代水杨酸(FTS)是一种人工合成的法尼基半胱氨酸模拟物，它可以抑制ErbB_2和Ras转化细胞的生长，但不抑制v-Raf转化细胞的生长，这表明FTS特异性地干扰RAS功能。在这里，我们证明FTS从H-RAS转化的(EJ)细胞膜上移走RAS，促进其降解并减少细胞内总RAS。短暂存在于细胞质中的移位RAS被相对迅速地降解，导致细胞内RAS总量下降高达80%。经FTS处理的EJ细胞RAS半衰期为10+/-4h，对照组为27+/-4h。膜RAS的移位和细胞总RAS的减少呈剂量依赖性：50%的作用发生在10-15mU M，与EJ细胞50%生长抑制所需的浓度(7-10mM)相当。需要较高浓度的FTS(25-50µM)才能将RAS从表达正常RAS的大鼠-1细胞膜上清除，这表明FTS对致癌RAS具有一定的选择性。异源三聚体G蛋白的膜定位不受FTS的影响。与FTS相关的化合物N-乙酰基-S-法尼基-L-半胱氨酸不抑制EJ细胞的生长，对RAS无影响。FTS不抑制N-肉豆蔻酰化H-RAS转化的大鼠-1细胞的生长，也不减少这种RAS亚型的总量。结果表明，FTS以一种相当特异的方式影响RAS在细胞膜上的对接，使蛋白质易于蛋白质降解。
Membrane anchorage of Ras oncoproteins, required for transforming activity, depends on their carboxy-terminal farnesylcysteine. We previously showed that S-trans,trans-farnesylthiosalicylic acid (FTS), a synthetic farnesylcysteine mimetic, inhibits growth of ErbB2- and Ras-transformed cells, but not of v-Raf-transformed cells, suggesting that FTS interferes specifically with Ras functions. Here we demonstrate that FTS dislodges Ras from membranes of H-Ras-transformed (EJ) cells, facilitating its degradation and decreasing total cellular Ras. The dislodged Ras that was transiently present in the cytosol was degraded relatively rapidly, causing a decrease of up to 80% in total cellular Ras. The half-life of Ras was 10 +/- 4 h in FTS-treated EJ cells and 27 +/- 4 h in controls. The dislodgment of membrane Ras and decrease in total cellular Ras were dose-dependent: 50% of the effects occurred at 10-15 mu M, comparable to concentrations (7-10 mu M) required for 50% growth inhibition in EJ cells. Higher concentrations of FTS (25-50 mu M) were required to dislodge Ras from Rat-1 cell membranes expressing normal Ras, suggesting some selectivity of FTS toward oncogenic Ras. Membrane localization of the prenylated G beta gamma of heterotrimeric G proteins was not affected by FTS in EJ cells. An FTS-related compound, N-acetyl-S-farnesyl-L-cysteine, which does not inhibit EJ cell growth, did not affect Ras. FTS did not inhibit growth of Rat-1 cells transformed by N-myristylated H-Ras and did not reduce the total amount of this Ras isoform. The results suggest that FTS affects docking of Ras in the cell membrane in a rather specific manner, rendering the protein susceptible to proteolytic degradation.