G-protein Signaling Modulator-3 Regulates Heterotrimeric G-protein Dynamics through Dual Association with Gβ and Gαi Protein Subunits
G-protein Signaling Modulator-3 Regulates Heterotrimeric G-protein Dynamics through Dual Association with Gβ and Gαi Protein Subunits
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DOI：
10.1074/jbc.m111.311712
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发表时间：
2012-02-10
影响因子：
4.8
通讯作者：
Siderovski, David P.
中科院分区：
文献类型：
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作者：
Giguere, Patrick M.;Laroche, Genevieve;Siderovski, David P.
G蛋白异源三聚体（G α中心点GDP/G β γ）的组装和功能的调节是一个涉及许多辅助蛋白参与的复杂过程。其中一种调节因子GPSM 3是一个蛋白质家族的成员，该蛋白质家族含有一个或多个被称为GoLoco（或GPR）基序的小调节基序的拷贝。虽然已知GPSM 3通过其GoLoco基序结合G α（i）中心点GDP亚基，但在这里我们报告GPSM 3也与G β亚基G β 1至G β 4相互作用，而不依赖于G γ或G α中心点GDP亚基相互作用。双分子荧光互补研究表明，G β-GPSM 3复合物形成，并通过高尔基体，也存在于细胞质中的可溶性复合物。GPSM 3和G β内源性共定位于THP-1细胞的质膜和胞核区室中。我们提供的证据表明，GPSM 3增加G β的稳定性，直到G β γ二聚体的形成，包括协会的G β-GPSM 3复合物与糖蛋白样蛋白PhLP和T-复合物蛋白1亚基eta（CCT 7），两个已知的伴侣蛋白的新合成的G β亚基。GPSM 3内的G β相互作用位点被定位到其第一个GoLoco基序的N-末端侧附近的富含亮氨酸的区域。G β和G α（i）中心点GDP结合事件都是GPSM 3抑制磷脂酶-C β活化的活性所需的。GPSM 3在THP-1细胞中也显示出对Akt活化（一种已知的G β γ依赖性途径）是重要的。G β/GPSM 3相互作用的发现，独立于G α中心点GDP和G γ参与，增加了GPSM 3在异源三聚体G蛋白调节中的作用的组合复杂性。
Regulation of the assembly and function of G-protein heterotrimers (G alpha center dot GDP/G beta gamma) is a complex process involving the participation of many accessory proteins. One of these regulators, GPSM3, is a member of a family of proteins containing one or more copies of a small regulatory motif known as the GoLoco (or GPR) motif. Although GPSM3 is known to bind G alpha(i)center dot GDP subunits via its GoLoco motifs, here we report that GPSM3 also interacts with the G beta subunits G beta 1 to G beta 4, independent of G gamma or G alpha center dot GDP subunit interactions. Bimolecular fluorescence complementation studies suggest that the G beta-GPSM3 complex is formed at, and transits through, the Golgi apparatus and also exists as a soluble complex in the cytoplasm. GPSM3 and G beta co-localize endogenously in THP-1 cells at the plasma membrane and in a juxtanuclear compartment. We provide evidence that GPSM3 increases G beta stability until formation of the G beta gamma dimer, including association of the G beta-GPSM3 complex with phosducin-like protein PhLP and T-complex protein 1 subunit eta (CCT7), two known chaperones of neosynthesized G beta subunits. The G beta interaction site within GPSM3 was mapped to a leucinerich region proximal to the N-terminal side of its first GoLoco motif. Both G beta and G alpha(i)center dot GDP binding events are required for GPSM3 activity in inhibiting phospholipase-C beta activation. GPSM3 is also shown in THP-1 cells to be important for Akt activation, a known G beta gamma-dependent pathway. Discovery of a G beta/GPSM3 interaction, independent of G alpha center dot GDP and G gamma involvement, adds to the combinatorial complexity of the role of GPSM3 in heterotrimeric G-protein regulation.