Pivotal Role of Extended Linker 2 in the Activation of Gα by G Protein-coupled Receptor
Pivotal Role of Extended Linker 2 in the Activation of Gα by G Protein-coupled Receptor
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DOI：
10.1074/jbc.m114.608661
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发表时间：
2015-01-02
影响因子：
4.8
通讯作者：
Huang, Xin-Yun
中科院分区：
文献类型：
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作者：
Huang, Jianyun;Sun, Yutong;Huang, Xin-Yun
背景：G蛋白偶联受体主要通过异源三聚体G蛋白传递信号。结果：我们已经证明，扩展连接子2中的突变会损害-肾上腺素能受体对G（s）的激活。结论：我们提出了一个潜在的新管道，从肾上腺素能受体的螺旋结构域的G（s）亚基通过延长连接2。重要性：G蛋白偶联受体（GPCRs）主要将细胞外信号传递给异源三聚体G蛋白（G），是最成功的药物靶点。GPCR激活G蛋白的机制还不清楚。先前的研究已经揭示了从GPCR经由G的C-末端5-螺旋到鸟嘌呤核苷酸结合口袋的信号中继途径。最近的结构和生物物理学研究揭示了开放或旋转的螺旋结构域的G在激活G的GPCR的作用。在这里，我们表明，肾上腺素能受体激活8个G（S）突变蛋白（从66 G（S）突变体的屏幕），是无法结合G亚单位在细胞中。这八个突变体中的五个在F/连接体2/2铰链区（延伸的连接体2）中，该铰链区连接Ras样GT3结构域和G（s）的β-螺旋结构域。该延伸接头2是G（q）的天然产物抑制剂的靶位点。我们的数据表明，扩展的连接子2是G激活GPCR的关键。我们提出GPCR通过其胞内环2直接与G的（2）/（3）环相互作用以与Linker 2通信，导致在G蛋白活化期间-螺旋结构域的打开和关闭以及GDP的释放。
Background: G protein-coupled receptors mainly signal through heterotrimeric G-proteins. Results: We have demonstrated that mutations in the extended Linker 2 impaired the activation of G(s) by -adrenergic receptors. Conclusion: We have proposed a potential novel conduit from -adrenergic receptors to the helical domain of G(s) subunit via the extended Linker 2. Significance: Our systematic mutagenesis studies provide insights into the activation mechanism of G-proteins by receptors.G protein-coupled receptors (GPCRs) relay extracellular signals mainly to heterotrimeric G-proteins (G) and they are the most successful drug targets. The mechanisms of G-protein activation by GPCRs are not well understood. Previous studies have revealed a signal relay route from a GPCR via the C-terminal 5-helix of G to the guanine nucleotide-binding pocket. Recent structural and biophysical studies uncover a role for the opening or rotating of the -helical domain of G during the activation of G by a GPCR. Here we show that -adrenergic receptors activate eight G(s) mutant proteins (from a screen of 66 G(s) mutants) that are unable to bind G subunits in cells. Five of these eight mutants are in the F/Linker 2/2 hinge region (extended Linker 2) that connects the Ras-like GTPase domain and the -helical domain of G(s). This extended Linker 2 is the target site of a natural product inhibitor of G(q). Our data show that the extended Linker 2 is critical for G activation by GPCRs. We propose that a GPCR via its intracellular loop 2 directly interacts with the (2)/(3) loop of G to communicate to Linker 2, resulting in the opening and closing of the -helical domain and the release of GDP during G-protein activation.