Gαq binds to p110α/p85α phosphoinositide 3-kinase and displaces Ras
Gαq binds to p110α/p85α phosphoinositide 3-kinase and displaces Ras
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DOI：
10.1042/bj20051493
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发表时间：
2006-03-15
影响因子：
4.1
通讯作者：
Lin, RZ
中科院分区：
文献类型：
--
作者：
Ballou, LM;Chattopadhyay, M;Lin, RZ
多项研究报告称，G(q) 偶联受体的激活会抑制 PI3K（磷酸肌醇 3-激酶）信号传导。在本研究中，我们使用纯化的蛋白质来证明 G α(q) 以 GTP 依赖性方式直接抑制 p110 α/p85 α PI3K。经荧光光谱测量，活化的 Gaq 与 p110 α/p85 α PI3K 结合的表观亲和力比 G α(q) (.) GDP 的亲和力强七倍。相反，Gaq 不结合 p110 gamma PI3K。荧光光谱实验还表明，G α(q) 与 PI3K 激活剂 Ras 竞争与 p110 α/p85 α 的结合。有趣的是，使用缺失突变体的共沉淀研究表明，G α(q) 与 p110 α 的 p85 结合域结合，而不是 Ras 结合域。细胞中组成型活性 G α(q)Q209L 的表达抑制 PI3K/Akt 通路的 Ras 激活，但对 Ras/Raf/MEK [MAPK（丝裂原激活蛋白激酶）/ERK（细胞外信号调节激酶）激酶]信号传导没有影响。这些结果表明，G(q) 偶联受体的激活导致 G α(q) (.) GTP 与 PI3K 某些亚型的结合增加，这可能解释了为什么这些受体在某些细胞类型中抑制此信号传导途径。
Several studies have reported that activation of G(q)-coupled receptors inhibits PI3K (phosphoinositide 3-kinase) signalling. In the present study, we used purified proteins to demonstrate that G alpha(q) directly inhibits p110 alpha/p85 alpha PI3K in a GTP-dependent manner. Activated Gaq binds to the p110 alpha/p85 alpha PI3K with an apparent affinity that is seven times stronger than that for G alpha(q) (.) GDP as measured by fluorescence spectroscopy. In contrast, Gaq did not bind to the p110 gamma PI3K. Fluorescence spectroscopy experiments also showed that G alpha(q) competes with Ras, a PI3K activator, for binding to p110 alpha/p85 alpha. Interestingly, co-precipitation studies using deletion mutants showed that G alpha(q) binds to the p85-binding domain of p110 alpha and not to the Ras-binding domain. Expression of constitutively active G alpha(q)Q209L in cells inhibited Ras activation of the PI3K/Akt pathway but had no effect on Ras/Raf/MEK [MAPK (mitogen-activated protein kinase)/ERK (extra-cell ular-signal-regulated kinase) kinase] signalling. These results suggest that activation of G(q)-coupled receptors leads to increased binding of G alpha(q) (.) GTP to some isoforms of PI3K, which might explain why these receptors inhibit this signalling pathway in certain cell types.