Receptor- and nucleotide exchange-independent mechanisms for promoting G protein subunit dissociation
Receptor- and nucleotide exchange-independent mechanisms for promoting G protein subunit dissociation
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DOI：
10.1074/jbc.c300271200
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发表时间：
2003-09-12
影响因子：
4.8
通讯作者：
Smrcka, AV
中科院分区：
文献类型：
--
作者：
Ghosh, M;Peterson, YK;Smrcka, AV
不依赖于G蛋白偶联受体激活的异源三聚体G蛋白激活机制正变得越来越明显。我们最近确定了β-γ亚基结合肽，我们提出绑定到β-γ亚基上的“热点”，刺激G蛋白解离，而不刺激核苷酸交换和激活完整细胞中的G蛋白信号传导。AGS 3是G蛋白信号传导激活因子家族中的一员，也以不依赖于核苷酸交换的方式激活G蛋白信号传导，并且AGS 3同源物参与发育过程中的不对称细胞分裂。在这里，我们证明了一个共识G蛋白调节（GPR）肽AGS 3和相关蛋白是足以诱导G蛋白亚基解离和GPR和热点结合肽促进解离的程度与已知的G蛋白激活剂，AMF。来自腺苷酸环化酶2和GRK 2的肽阻止异源三聚体复合物的形成，但不改变α亚基与β γ亚基解离的速率。这些数据表明，这些核苷酸交换独立的G蛋白激活肽不简单地竞争与β γ亚基的α相互作用，但积极促进亚基解离。因此，我们提出了两种新的机制，核苷酸交换独立激活G蛋白信号，一个涉及α亚基的构象变化，一个涉及β γ亚基的构象变化。
Mechanisms for heterotrimeric G protein activation that do not rely on G protein coupled receptor activation are becoming increasingly apparent. We recently identified betagamma subunit-binding peptides that we proposed bound to a "hot spot" on betagamma subunits, stimulating G protein dissociation without stimulating nucleotide exchange and activating G protein signaling in intact cells. AGS3, a member of the activators of G protein signaling family of proteins, also activates G protein signaling in a nucleotide exchange-independent manner, and AGS3 homologues are involved in asymmetric cell division during development. Here we demonstrate that a consensus G protein regulatory (GPR) peptide from AGS3 and related proteins is sufficient to induce G protein subunit dissociation and that both the GPR and hot spot-binding peptides promote dissociation to extents comparable with a known G protein activator, AMF. Peptides derived from adenylyl cyclase 2 and GRK2 prevented formation of the heterotrimeric complex but did not alter the rate of alpha subunit dissociation from betagamma subunits. These data indicate that these nucleotide exchange-independent G protein activator peptides do not simply compete for alpha interactions with betagamma subunits, but actively promote subunit dissociation. Thus, we propose two novel mechanisms for nucleotide exchange independent activation of G protein signaling, one that involves conformational changes in the alpha subunit and one that involves conformational changes in the betagamma subunits.