Membrane recruitment of Raf-1 is not the only function of Ras in Raf-1 activation
Membrane recruitment of Raf-1 is not the only function of Ras in Raf-1 activation
复制标题
Raf-1 的膜募集并不是 Ras 在 Raf-1 激活中的唯一功能
DOI：
10.1038/sj.onc.1201582
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发表时间：
1997
期刊：
影响因子：
8
通讯作者：
T. Kataoka
中科院分区：
文献类型：
--
作者：
M. Tamada;Chang;K. Kariya;T. Okada;T. Kataoka
RAS与Raf-1相互作用，刺激Raf-1的激酶活性，导致丝裂原活化蛋白(MAP)激活级联反应。已经提出RAS在Raf-1激活中的主要作用是将Raf-1募集到质膜上，在质膜上发生单独的激活事件，如磷酸化。在这里，我们检测了不同的人Ha-RAS突变体在体内诱导Raf-1膜转位和激活Raf-1的活性。活化区突变体Ha-RAS V45E在COS7细胞中的过表达诱导Raf-1的膜转位与野生型Ha-RAS一样有效。然而，与野生型Ha-RAS相比，该突变体激活Raf-1和细胞外信号调节激酶-2(ERK2)的活性降低了约70%。通过测定从膜组分中纯化的与Ha-Ras V45E相关的Raf-1的活性，进一步证明了比活性的降低。这些结果表明，RAS与Raf-1的结合具有另一个重要的结果，可能依赖于其激活区与Raf-1之间的相互作用，而不是简单地将Raf-1募集到质膜上。
Ras interacts with Raf-1 and stimulates its kinase activity, which results in activation of the mitogen-activated protein (MAP) kinase cascade. It has been proposed that the main function of Ras in Raf-1 activation is to recruit Raf-1 to the plasma membrane, where a separate activation event such as phosphorylation takes place. Here, we examined the activities of various mutants of human Ha-Ras to induce membrane translocation of Raf-1 and to activate Raf-1 in vivo. Overexpression of an activator region mutant Ha-Ras V45E in COS7 cells induced membrane translocation of Raf-1 as effectively as wild-type Ha-Ras. However, the activity of this mutant to activate Raf-1 and extracellular signal-regulated kinase-2 (ERK2) was attenuated by approximately 70% compared to that of wild-type Ha-Ras. The decrease in the specific activity was further demonstrated by measuring the activity of the Ha-Ras V45E-associated Raf-1 purified from the membrane fraction. These results imply that the association of Ras with Raf-1 has another important consequence, presumably dependent on the interaction between its activator region and Raf-1, than the simple recruitment of Raf-1 to the plasma membrane.