The molecular mechanisms by which receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major signaling hubs in eukaryotes, independently relay signals across the plasma membrane have been extensively characterized. How these hubs crosstalk has been a long-standing question, but answers remain elusive. Using linear-ion-trap mass spectrometry in combination with biochemical, cellular, and computational approaches, we unravel a mechanism of activation of heterotrimeric G proteins by RTKs and chart the key steps that mediate such activation. Upon growth factor stimulation, the guanine-nucleotide exchange modulator, GIV, dissociates G-alpha(i)/beta/gamma trimers, scaffolds monomeric G-alpha(i) with RTKs, and facilitates the phosphorylation on two tyrosines located within the inter-domain cleft of G-alpha(i). Phosphorylation triggers the activation of G-alpha(i) and inhibits second messengers (cAMP). Tumor-associated mutants reveal how constitutive activation of this pathway impacts cellular decision to go vs. grow. These insights define a tyrosine-based G protein signaling paradigm and reveal its importance in eukaryotes.

中文翻译：

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受体酪氨酸激酶通过Gαi域间裂隙内的磷酸化激活异源三聚体G蛋白

受体酪氨酸激酶（RTK）和异三聚体G蛋白（真核生物中的两个主要信号传导枢纽）独立地在整个质膜上传递信号的分子机制已得到广泛表征。这些集线器如何串扰一直是一个长期存在的问题，但是答案仍然难以捉摸。使用线性离子阱质谱结合生化，细胞和计算方法，我们揭示了RTK激活异三聚体G蛋白的机制，并绘制了介导这种激活的关键步骤。受到生长因子刺激后，鸟嘌呤核苷酸交换调节剂GIV使G-alpha（i）/ beta / gamma三聚体解离，将单体G-alpha（i）与RTKs结合在一起，并促进位于两个氨基酸之间的两个酪氨酸的磷酸化。 G-alpha（i）的畴裂。磷酸化触发G-alpha（i）的激活并抑制第二信使（cAMP）。肿瘤相关突变体揭示了此途径的组成性激活如何影响细胞生长决定。这些见解定义了基于酪氨酸的G蛋白信号范式，并揭示了其在真核生物中的重要性。