p21-Activated kinase 1 (Pak1)-dependent phosphorylation of Raf-1 regulates its mitochondrial localization, phosphorylation of BAD, and Bcl-2 association
p21-Activated kinase 1 (Pak1)-dependent phosphorylation of Raf-1 regulates its mitochondrial localization, phosphorylation of BAD, and Bcl-2 association
复制标题
DOI：
10.1074/jbc.m413374200
复制
发表时间：
2005-07-01
影响因子：
4.8
通讯作者：
Field, J
中科院分区：
文献类型：
--
作者：
Jin, SH;Zhuo, Y;Field, J
RAF-1通过移位到线粒体来保护细胞免受凋亡，而不是依赖于其对MEK和ERK的信号。在线粒体上，RAF-1与BAD结合并取代BAD。然而，Raf-1通常是如何被引诱到线粒体并被激活的这个问题的答案仍然难以捉摸。P21激活的蛋白激酶(PAK)是一种丝氨酸/苏氨酸蛋白激酶，可使Raf-1在Ser-338和Ser-339处磷酸化。在这里，我们阐明了Ak1通过Raf-1激活的途径向BAD发出信号的分子机制。当被Ak1磷酸化时，Raf-1转位到线粒体，并在Ser-112处磷酸化BAD。此外，Raf-1在Ser-338/Ser-339处的磷酸化也调节了Raf-1的线粒体易位以及Raf-1与Bcl2的相互作用。值得注意的是，我们发现Raf-1-Bcl-2复合体的形成与Bcl-2和BAD之间相互作用的丧失是一致的。这些信号是Ak1所特有的，因为Src激活的Raf-1只刺激MAP激酶级联。因此，我们的数据确定了参与细胞生存信号的Pak1-Raf-1-Bad通路的分子连接。
Raf-1 protects cells from apoptosis, independently of its signals to MEK and ERK, by translocating to the mitochondria where it binds Bcl-2 and displaces BAD. However, the answer to the question of how Raf-1 is normally lured to the mitochondria and becomes activated remains elusive. p21-activated protein kinases (Paks) are serine/threonine protein kinases that phosphorylate Raf-1 at Ser-338 and Ser-339. Here we elucidate the molecular mechanism through which Pak1 signals to BAD through a Raf-1-activated pathway. Upon phosphorylation by Pak1, Raf-1 translocates to mitochondria and phosphorylates BAD at Ser-112. Moreover, the mitochondrial translocation of Raf-1 and the interaction between Raf-1 and Bcl-2 are regulated by Raf-1 phosphorylation at Ser-338/Ser-339. Notably, we show that formation of a Raf-1-Bcl-2 complex coincides with loss of an interaction between Bcl- 2 and BAD. These signals are specific for Pak1, because Src-activated Raf-1 only stimulates the MAP kinase cascade. Thus, our data identify the molecular connections of a Pak1-Raf-1-BAD pathway that is involved in cell survival signaling.