Activated Gαq inhibits p110α phosphatidylinositol 3-kinase and Akt
Activated Gαq inhibits p110α phosphatidylinositol 3-kinase and Akt
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DOI：
10.1074/jbc.m212232200
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发表时间：
2003-06-27
影响因子：
4.8
通讯作者：
Lin, RZ
中科院分区：
文献类型：
--
作者：
Ballou, LM;Lin, HY;Lin, RZ
一些G（q）-偶联受体已显示拮抗磷脂酰肌醇3-激酶（PI 3 K）及其下游效应物Akt的生长因子活化。我们使用了一个组成型活性的Galpha（q）（Q209 L）突变体来探索Galpha（q）激活对通过PI 3 K/Akt途径的信号传导的影响。在大鼠-1成纤维细胞中瞬时表达Ga（q）（Q209 L）抑制血小板衍生生长因子或胰岛素处理诱导的Akt活化。在人胚肾293细胞中，Ga（q）（Q209 L）的表达也减弱了由组成型活性PI 3 K的共表达促进的Akt活化。Galalpha（q）（Q209 L）对Akt突变体的活性没有影响，其中两个调节磷酸化位点被改变为酸性氨基酸。在稳定转染的293细胞系中，Galpha（q）（Q209 L）的诱导表达导致p110 α（而不是p110 β）免疫沉淀物中PI 3 K活性的降低。Galpha（q）的受体活化也选择性抑制p110 α免疫沉淀物中的PI 3 K活性。在用磷脂酶C抑制剂U 73122预处理的细胞中，活性Galalpha（q）仍然抑制PI 3 K/Akt。最后，Ga（q）（Q209 L）与来自表达这些蛋白质的COS-7细胞裂解物的p110 α-p85 α PI 3 K异源二聚体共免疫沉淀，并且免疫沉淀的Ga（q）（Q209 L）与纯化的重组p110 α-p85 α体外孵育导致PI 3 K活性降低。这些结果表明，与G（q）偶联受体结合的激动剂通过释放抑制PI 3 K的活性Ga（q）亚基阻断Akt活化。其抑制机制似乎不依赖于磷脂酶C的激活，可能涉及Ga（q）和p110 α PI 3 K之间的抑制性相互作用。
Some G(q)-coupled receptors have been shown to antagonize growth factor activation of phosphatidylinositol 3-kinase (PI3K) and its downstream effector, Akt. We used a constitutively active Galpha(q)(Q209L) mutant to explore the effects of Galpha(q) activation on signaling through the PI3K/Akt pathway. Transient expression of Galpha(q)(Q209L) in Rat-1 fibroblasts inhibited Akt activation induced by platelet-derived growth factor or insulin treatment. Expression of Galpha(q)(Q209L) also attenuated Akt activation promoted by coexpression of constitutively active PI3K in human embryonic kidney 293 cells. Galpha(q)(Q209L) had no effect on the activity of an Akt mutant in which the two regulatory phosphorylation sites were changed to acidic amino acids. Inducible expression of Galpha(q)(Q209L) in a stably transfected 293 cell line caused a decrease in PI3K activity in p110alpha (but not p110beta) immunoprecipitates. Receptor activation of Galpha(q) also selectively inhibited PI3K activity in p110alpha immunoprecipitates. Active Galpha(q) still inhibited PI3K/Akt in cells pretreated with the phospholipase C inhibitor U73122. Finally, Galpha(q)(Q209L) co-immunoprecipitated with the p110alpha-p85alpha PI3K heterodimer from lysates of COS-7 cells expressing these proteins, and incubation of immunoprecipitated Galpha(q)(Q209L) with purified recombinant p110alpha-p85alpha in vitro led to a decrease in PI3K activity. These results suggest that agonist binding to G(q)-coupled receptors blocks Akt activation via the release of active Galpha(q) subunits that inhibit PI3K. The inhibitory mechanism seems to be independent of phospholipase C activation and might involve an inhibitory interaction between Galpha(q) and p110alpha PI3K.