GIV/Girdin activates Gαi and inhibits Gαs via the same motif
GIV/Girdin activates Gαi and inhibits Gαs via the same motif
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DOI：
10.1073/pnas.1609502113
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发表时间：
2016-09-27
影响因子：
11.1
通讯作者：
Ghosh, Pradipta
中科院分区：
文献类型：
--
作者：
Gupta, Vijay;Bhandari, Deepali;Ghosh, Pradipta
我们以前表明，鸟嘌呤核苷酸结合（G）蛋白，一个亚基（G α）相互作用的囊泡相关蛋白（GIV），鸟嘌呤核苷酸交换因子（GEF），反式激活G α活性抑制多肽1（G α i）蛋白响应生长因子，如EGF，使用短的C-末端基序。随后的测序工作表明，GIV也结合G α s，并且无活性的G α s促进内体的成熟并关闭来自内体的促有丝分裂MAPK-ERK 1/2信号。然而，GIV与两种G蛋白G α i和G α s双重偶联的机制和后果仍然未知。在这里，我们报告说，GIV是一个双功能的G蛋白的调节剂，它作为一个鸟嘌呤核苷酸解离抑制剂（GDI）的G α s使用相同的基序，使其能够作为一个GEF的G α i。在EGF刺激后，GIV依次调节G α i和G α s：首先，关键的磷酸化修饰有利于GIV-G α i复合物的组装并激活GIV的GEF功能;然后第二次磷酸化修饰终止GIV的GEF功能，触发GIV-G α s复合物的组装，并激活GIV的GDI功能。通过比较WT和GIV突变体，我们证明GIV抑制细胞对EGF反应的G α s活性。因此，cAMP -> PKA -> cAMP反应元件结合蛋白信号传导轴被抑制，EGF受体通过早期内体的转运时间被加速，促有丝分裂MAPK-ERK 1/2信号被迅速终止，增殖被抑制。这些见解定义了G蛋白信号传导的范例，其中多效性作用调节剂使用相同的基序来激活和抑制G蛋白。我们的研究结果还阐明了两种相反的G α蛋白的这种调节如何整合下游信号和细胞反应。
We previously showed that guanine nucleotide-binding (G) protein a subunit (G alpha)-interacting vesicle-associated protein (GIV), a guanine-nucleotide exchange factor (GEF), transactivates G alpha activity-inhibiting polypeptide 1 (G alpha i) proteins in response to growth factors, such as EGF, using a short C-terminal motif. Subsequentwork demonstrated that GIV also binds G alpha s and that inactive G alpha s promotes maturation of endosomes and shuts down mitogenic MAPK-ERK1/2 signals from endosomes. However, the mechanism and consequences of dual coupling of GIV to two G proteins, G alpha i and G alpha s, remained unknown. Here we report that GIV is a bifunctional modulator of G proteins; it serves as a guanine nucleotide dissociation inhibitor (GDI) for G alpha s using the same motif that allows it to serve as a GEF for G alpha i. Upon EGF stimulation, GIV modulates G alpha i and G alpha s sequentially: first, a key phosphomodification favors the assembly of GIV-G alpha i complexes and activates GIV's GEF function; then a second phosphomodification terminates GIV's GEF function, triggers the assembly of GIV-G alpha s complexes, and activates GIV's GDI function. By comparing WT and GIV mutants, we demonstrate that GIV inhibits G alpha s activity in cells responding to EGF. Consequently, the cAMP -> PKA -> cAMP response element-binding protein signaling axis is inhibited, the transit time of EGF receptor through early endosomes are accelerated, mitogenic MAPK-ERK1/2 signals are rapidly terminated, and proliferation is suppressed. These insights define a paradigm in G-protein signaling in which a pleiotropically actingmodulator uses the same motif both to activate and to inhibit G proteins. Our findings also illuminate how such modulation of two opposing G alpha proteins integrates downstream signals and cellular responses.