Mechanism of suppression of the Raf/MEK/extracellular signal-regulated kinase pathway by the Raf kinase inhibitor protein
Mechanism of suppression of the Raf/MEK/extracellular signal-regulated kinase pathway by the Raf kinase inhibitor protein
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DOI：
10.1128/mcb.20.9.3079-3085.2000
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发表时间：
2000-05-01
影响因子：
5.3
通讯作者：
Kolch, W
中科院分区：
文献类型：
--
作者：
Yeung, K;Janosch, P;Kolch, W
我们最近发现Raf激酶抑制蛋白(RKIP)是Raf-1/MEK/细胞外信号调节蛋白(ERK)通路的内源性生理性抑制因子。RKIP干扰Raf-1对MEK的磷酸化和激活，从而抑制Raf-1诱导的转化和AP-1依赖的转录。在此，我们报道了RKIP抑制作用的分子机制。RKIP能与Raf-1、MEK和ERK形成三元复合体。然而，虽然MEK和ERK可以同时与RKIP结合，但Raf-1与RKIP的结合和MEK的结合是相互排斥的。RKIP能解离Raf-1-MEK复合体，是MEK磷酸化的竞争性抑制剂。结合结构域图谱显示，MEK和Raf-1与RKIP中的重叠部位结合，而MEK和RKIP与Raf-1中的不同结构域结合，Raf-1和RKIP与MEK中的不同部位结合。RKIP中的Raf-1和MEK结合位点都需要被破坏，以解除RKIP对Raf-1/MEK/ERK通路的抑制，这表明Raf-1或MEK的结合足以抑制。RKIP的性质揭示了相互作用成分的特定隔离，作为细胞调控信号通路的一个新基序。
We have recently identified the Raf kinase inhibitor protein (RKIP) as a physiological endogenous inhibitor of the Raf-1/MEK/extracellular signal-regulated kinase (ERK) pathway. RKIP interfered with MEK phosphorylation and activation by Raf-1, resulting in the suppression of both Raf-1-induced transformation and AP-1-dependent transcription. Here we report the molecular mechanism of RKIP's inhibitory function. RKIP can form ternary complexes with Raf-1, MEK, and ERK. However, whereas MEK and ERK can simultaneously associate with RKIP, Raf-1 binding to RKIP and that of MEK are mutually exclusive. RKIP is able to dissociate a Raf-1-MEK complex and behaves as a competitive inhibitor of MEK phosphorylation. Mapping of the binding domains showed that MEK and Raf-1 bind to overlapping sites in RKIP, whereas MEK and RKIP associate with different domains in Raf-1, and Raf-1 and RKIP bind to different sites in MEK. Both the Raf-1 and the MEK binding sites in RKIP need to be destroyed in order to relieve RKIP-mediated suppression of the Raf-1/MEK/ERK pathway, indicating that binding of either Raf-1 or MEK is sufficient for inhibition. The properties of RKIP reveal the specific sequestration of interacting components as a novel motif in the cell's repertoire for the regulation of signaling pathways.