Heterotrimeric G protein Galphas subunit attenuates PLEKHG2, a Rho family-specific guanine nucleotide exchange factor, by direct interaction
Heterotrimeric G protein Galphas subunit attenuates PLEKHG2, a Rho family-specific guanine nucleotide exchange factor, by direct interaction
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异三聚体 G 蛋白 Galphas 亚基通过直接相互作用减弱 PLEKHG2（一种 Rho 家族特异性鸟嘌呤核苷酸交换因子）
DOI：
10.1016/j.cellsig.2017.01.022
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发表时间：
2017
期刊：
影响因子：
4.8
通讯作者：
Ueda H
中科院分区：
文献类型：
--
作者：
Sugiyama K;Tago K;Matsushita S;Nishikawa M;Sato K;Muto Y;Nagase T;Ueda H
PLEKHG 2是小GTP酶Rac和Cdc 42的Gβγ依赖性鸟嘌呤核苷酸交换因子（GEF），并已被证明介导信号传导途径，如肌动蛋白细胞骨架重组和血清反应元件（SRE）依赖性基因转录。我们发现Gαs亚基的组成型活性突变体显著减弱了PLEKHG 2诱导的SRE介导的基因转录。引人注目的是，我们观察到CTx处理的内源性Gαs的组成性激活对PLEKHG 2诱导的SRE激活产生了类似的抑制作用。然而，蛋白激酶A催化亚基β的增强表达和二丁基环AMP处理均未能模拟Gαs对PLEKHG 2的抑制作用。此外，蛋白激酶A的显性失活突变体对PLEKHG 2介导的SRE激活没有影响。通过免疫沉淀和体外pulldown实验，我们发现PLEKHG 2与细胞中Gαs亚基的活性形式直接相互作用。PLEKHG 2和Gαs之间的相互作用需要PLEKHG 2的N端区域，该区域包括DH结构域，这表明Gαs直接掩蔽PLEKHG 2的DH结构域。在以前的研究中，我们报道了Gβγ加速PLEKHG 2介导的SRE依赖性基因转录。有趣的是，Gαs也抑制由Gβγ和PLEKHG 2共表达诱导的SRE的超活化;然而，Gαs和Gβγ结合于PLEKHG 2的不同区域。这是首次报道PLEKHG 2是一种新的Gαs效应子，并通过直接相互作用受到Gαs亚基的负调控。
PLEKHG2 is a Gβγ-dependent guanine nucleotide exchange factor (GEF) for the small GTPases Rac and Cdc42, and has been shown to mediate signalling pathways such as actin cytoskeleton reorganization and serum response element (SRE)-dependent gene transcription. Here we show that the constitutively active mutant of the Gαs subunit significantly attenuated PLEKHG2-induced SRE-mediated gene transcription. Strikingly, we observed that the constitutive activation of endogenous Gαs by treatment with CTx caused a similar inhibitory effect on PLEKHG2-induced activation of SRE. However, both the enforced expression of the catalytic subunit β of protein kinase A and the treatment with dibutyl-cyclic AMP failed to mimic the inhibitory effect of Gαs on PLEKHG2. Furthermore, the dominant negative mutant of protein kinase A had no effect on PLEKHG2-mediated SRE activation. Performing immunoprecipitation and anin vitropulldown assay, we found that PLEKHG2 directly interacted with the active form of the Gαs subunit in cells. The interaction between PLEKHG2 and Gαs required the N-terminal region of PLEKHG2, which includes the DH domain, a functional domain of GEF, suggesting that Gαs directly masks the DH domain of PLEKHG2. In a previous study, we reported that Gβγ accelerates PLEKHG2-mediated SRE-dependent gene transcription. Interestingly, Gαs also inhibited the hyperactivation of SRE induced by the co-expression of Gβγ and PLEKHG2; however, Gαs and Gβγ bind to different regions of PLEKHG2. This is the first report to show that PLEKHG2 is a novel effector of Gαs, and is negatively regulated by the Gαs subunit through direct interaction.