GGL-RGS proteins: bifunctional G-protein regulators

描述(由申请人提供)： G蛋白偶联受体(GPCRs)调节神经传递、生长和分化等关键生理过程，也是许多治疗药物和娱乐药物的靶标。异源三聚体鸟嘌呤核苷酸结合蛋白(G蛋白)在GPCR途径中起着分子开关的作用，其中GA亚基的活性取决于GTP或GDP的结合。GTP和GDP占有率的相对水平反映了核苷酸交换和GTP水解之间的平衡。前者由偶联到杂三聚体的GPCRs的配体激活来催化，而后者由GTP酶激活蛋白或GAP催化。G蛋白信号转导调节因子(RGS)是一类不同的蛋白质，它们充当GA亚基的间隙。RGS蛋白的一个亚家族(RGS6、7、9、11)含有一个GG样结构域(GGL)，它介导与b亚基的结合。因此，除了通过RGS结构域与GTP-GA亚基相互作用外，含有RGS(GGL-RGS)结构域的GGL蛋白还可能与GDP-GA亚基结合，促进受体偶联。本项目旨在验证这样的假设，即GGL-RGS蛋白分别通过GGL和RGS结构域调节GDP-GA的受体偶联和GTP-GA的GTP水解，并且这两个结构域的α选择性决定了GGL-RGS蛋白对GPCR信号的整体影响。为了验证这一假设，将确定GUL和RGS结构域的GA选择性，定义这种选择性的分子决定因素，并比较野生型和突变型GGL-RGS结构对调节效应器通路GPCR激活的能力。

DESCRIPTION (provided by applicant): G-protein coupled receptors (GPCRs) regulate critical physiological processes such as neurotransmission, growth, and differentiation, and are also targeted by a large percentage of therapeutic agents and recreational drugs. Heterotrimeric guanine nucleotide binding proteins (G-proteins) act as molecular switches in GPCR pathways, in which the activity of the Ga subunit is determined by whether GTP or GDP is bound. Relative levels of GTP and GDP occupancy reflect the balance between nucleotide exchange and GTP hydrolysis. The former reaction is catalyzed by ligand activation of GPCRs coupled to heterotrimers, while the latter reaction is catalyzed by GTPase activating proteins, or GAPS. Regulators of G-protein Signaling (RGS) are diverse proteins that act as GAPs for Ga subunits. A subfamily of RGS proteins (RGS6, 7, 9, 11) contains a Gg-like (GGL) domain which mediates binding to b subunits. Therefore, in addition to interaction with GTP-Ga subunits through the RGS domain, GGL domain containing RGS (GGL-RGS) proteins may also associate with GDP-Ga subunits to promote receptor coupling. This project is designed to test the hypothesis that GGL-RGS proteins regulate both receptor coupling of GDP-Ga and GTP hydrolysis of GTP-Ga through the GGL and RGS domains, respectively, and that the alpha selectivity of the two domains determine the overall effect of GGL-RGS proteins on GPCR signaling. To test this hypothesis, the Ga selectivity of both the GUL and RGS domains will be determined, the molecular determinants of this selectivity will be defined, and wild type and mutant GGL-RGS constructs will be compared for their ability to regulate GPCR activation of effector pathways.