Phosphatidylinositol 3-kinase regulates Raf1 through Pak phosphorylation of serine 338
Phosphatidylinositol 3-kinase regulates Raf1 through Pak phosphorylation of serine 338
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DOI：
10.1016/s0960-9822(00)00475-9
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发表时间：
2000-05-04
期刊：
影响因子：
9.2
通讯作者：
Brugge, JS
中科院分区：
文献类型：
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作者：
Chaudhary, A;King, WG;Brugge, JS
我们以前已经证明，抑制磷脂酰肌醇（PI）3激酶严重减弱了整合素/纤连蛋白受体参与后细胞外信号调节激酶（Erk）的激活，Raf是PI 3激酶调节的关键靶点[I]，为了研究PI 3激酶如何调节Raf，我们检测了Raf 1上PI 3-激酶调控所需的位点，并探讨了参与这种调控的机制。丝氨酸338（Ser 338），这是至关重要的纤维连接蛋白刺激Raf 1，磷酸化的PI 3-激酶依赖性的方式后，接合的纤维连接蛋白受体。此外，含有磷酸化模拟突变（S338 D）的Raf 1突变体的纤连蛋白激活独立于PI 3-激酶。此外，整合素诱导的丝氨酸/苏氨酸激酶Pak-1的活化，其已被证明磷酸化Raf 1 Ser 338，也依赖于PI 3-激酶活性和激酶失活的Pak-1突变体的表达阻断Raf 1 Ser 338的磷酸化。这些结果表明PI 3-激酶通过丝氨酸/苏氨酸激酶Pak调节Raf 1 Ser 338的磷酸化。因此，Raf 1 Ser 338通过PI 3-激酶和Pak的磷酸化提供了共刺激信号，其与Pas一起导致Raf 1激酶活性被整联蛋白强烈激活。
We have previously shown that inhibition of phosphatidylinositol (PI) 3 kinase severely attenuates the activation of extracellular signal-regulated kinase (Erk) following engagement of integrin/fibronectin receptors and that Raf is the critical target of PI 3-kinase regulation [I], To investigate how PI 3-kinase regulates Raf, we examined sites on Raf1 required for regulation by PI 3-kinase and explored the mechanisms involved in this regulation. Serine 338 (Ser338), which was critical for fibronectin stimulation of Raf1, was phosphorylated in a PI 3-kinase-dependent manner following engagement of fibronectin receptors. In addition, fibronectin activation of a Raf1 mutant containing a phospho-mimic mutation (S338D) was independent of PI 3-kinase. Furthermore, integrin-induced activation of the serine/threonine kinase Pak-l,which has been shown to phosphorylate Raf1 Ser338, was also dependent on PI 3-kinase activity and expression of a kinase-inactive Pak-1 mutant blocked phosphorylation of Raf1 Ser338. These results indicate that PI 3-kinase regulates phosphorylation of Raf1 Ser338 through the serine/threonine kinase Pak. Thus, phosphorylation of Raf1 Ser338 through PI 3-kinase and Pak provides a co-stimulatory signal which together with Pas leads to strong activation of Raf1 kinase activity by integrins.