Hescheler J, Klinz F J, Schultz G, Wittinghofer A
Pharmakologisches Institut der Freien Universität Berlin, Germany.
Cell Signal. 1991;3(2):127-33. doi: 10.1016/0898-6568(91)90019-q.
Ras (p21) proteins are involved in the control of cell growth and differentiation, but the mechanism by which they exert these effects is not yet known. Here we present evidence that c-Ha-ras (p21(Gly-12)) and its oncogenic mutant T24-ras (p21(Val-12)) selectively induce omega-conotoxin and dihydropyridine-sensitive Ca2+ currents within a few hours after introduction into the cytoplasm of neuroblastoma x glioma hybrid cells. Whereas control cells exhibited a mean Ca2+ current of 250 pA, it amounted to 730 pA in cells pretreated with ras protein. In cells loaded with p21(Gly-12), the effect occurred after 2 hours and was terminated after 8 hours. In contrast, introduction of p21(Val-12) resulted in a prolonged delay (6 hours) of the effect which lasted for more than 24 hours. When ras proteins were preactivated with the non-hydrolysable GTP analog GppNHp, the time courses of both p21(Gly-12) and p21(Val-12) effects were fast and sustained, suggesting that in intact cells (i) the GDP/GTP exchange is faster for p21(Gly-12) compared to p21(Val-12) and (ii) inactivation of p21(Gly-12) is mediated by GAP-induced GTPase activity. T-type Ca2+ currents and K+ currents were unaffected by ras proteins.
Ras（p21）蛋白参与细胞生长和分化的调控，但其发挥这些作用的机制尚不清楚。在此我们提供证据表明，c-Ha-ras（p21（Gly-12））及其致癌突变体T24-ras（p21（Val-12））在导入神经母细胞瘤x胶质瘤杂交细胞的细胞质后数小时内，可选择性地诱导ω-芋螺毒素和二氢吡啶敏感的Ca2+电流。对照细胞的平均Ca2+电流为250 pA，而用ras蛋白预处理的细胞中该电流为730 pA。在用p21（Gly-12）装载的细胞中，该效应在2小时后出现，并在8小时后终止。相反，导入p21（Val-12）导致效应延长延迟（6小时），持续超过24小时。当ras蛋白用不可水解的GTP类似物GppNHp预激活时，p21（Gly-12）和p21（Val-12）效应的时间进程都很快且持续，这表明在完整细胞中：（i）与p21（Val-12）相比，p21（Gly-12）的GDP/GTP交换更快；（ii）p21（Gly-12）的失活由GAP诱导的GTPase活性介导。T型Ca2+电流和K+电流不受ras蛋白影响。
