Maintenance of Cdc42 GDP-bound state by Rho-GDI inhibits MAP kinase activation by the exchange factor Ras-GRF - Evidence for Ras-GRF function being inhibited by Cdc42-GDP but unaffected by Cdc42-GTP
Maintenance of Cdc42 GDP-bound state by Rho-GDI inhibits MAP kinase activation by the exchange factor Ras-GRF - Evidence for Ras-GRF function being inhibited by Cdc42-GDP but unaffected by Cdc42-GTP
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DOI：
10.1074/jbc.m011383200
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发表时间：
2001-06-15
影响因子：
4.8
通讯作者：
Crespo, P
中科院分区：
文献类型：
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作者：
Arozarena, I;Matallanas, D;Crespo, P
Pas 鸟嘌呤核苷酸交换因子 Ras-GRF/cdc25(Mn) 的功能受到严格的监管过程。我们最近表明 Ras-GRF 对 Ras/MAPK 通路的激活是由 Rho 家族 GTPase Cdc42 通过仍未知的机制控制的。在此，我们报告通过过表达 Rho-GDI 将 Cdc42 保留在 GDP 结合状态可抑制 Ras-GRF 介导的 MAPK 激活。相反，Ras-GRF 基础和 LPA 或离子霉素刺激的活性不受组成型活性 GTP 结合的 Cdc42 的影响。此外，Cdc42 下游效应器 MLK3、ACK1、PAK1 和 WASP 对 Ras-GRF 介导的 MAPK 激活没有可检测到的影响。相反，用Rho家族GEF Dbl或离子霉素促进Cdc42释放GDP可抑制Cdc42对Ras-GRF活性的抑制。我们得出结论，Cdc42-GDP 抑制 Ras-GRF 诱导的 MAPK 激活，但 Cdc42-GTP 和 Cdc42 下游效应器都不影响 Ras-GRF 性能。有趣的是，Cdc42 失去 GDP 结合状态消除了其对 Ras-GRF 功能的抑制作用。这些结果表明，Cdc42 的作用机制可能不仅仅局限于加载 GTP 时下游信号级联的激活，此外，GDP 结合形式可能充当抑制分子，下调平行信号传导途径，例如 Ras/MAPK 途径。
The function of the Pas guanine nucleotide exchange factor Ras-GRF/cdc25(Mn) is subject to tight regulatory processes. We have recently shown that the activation of the Ras/MAPK pathway by Ras-GRF is controlled by the Rho family GTPase Cdc42 through still unknown mechanisms. Here, we report that retaining Cdc42 in its GDP-bound state by overexpressing Rho-GDI inhibits Ras-GRF-mediated MAPK activation. Conversely, Ras-GRF basal and LPA- or ionomycin-stimulated activities were unaffected by a constitutively active GTP-bound Cdc42, Moreover, the Cdc42 downstream effecters MLK3, ACK1, PAK1, and WASP had no detectable influence on Ras-GRF-mediated MAPK activation. In contrast, promoting GDP release from Cdc42 with the Rho family GEF Dbl or with ionomycin suppressed the restraint exerted by Cdc42 on Ras-GRF activity. We conclude that Cdc42-GDP inhibits Ras-GRF-induced MAPK activation, but neither Cdc42-GTP nor the Cdc42 downstream effecters affect Ras-GRF performance, Interestingly, the loss of the GDP-bound state by Cdc42 abolishes its inhibitory effects on Ras-GRF function. These results suggest that the Cdc42 mechanism of action may not be solely restricted to activation of downstream signaling cascades when GTP-loaded, Furthermore, the GDP-bound form may be acting as an inhibitory molecule down-modulating parallel signaling routes such as the Ras/MAPK pathway.