Novel functions of RGS3

描述（由申请人提供）：G蛋白信号调节因子RGS3是一种GTPase激活蛋白（GAP），可结合异三聚体G蛋白的G- α亚基并加速其GTPase活性。我们和其他人已经证明，通过这种机制，RGS3调节Gq-和gi偶联受体对血管紧张素II、内皮素-1、碳醇、促性腺激素释放激素和鞘氨醇-1磷酸的信号传导。我们的新数据表明，a) RGS3与TGF-2信号转导器、Smad转录因子相互作用，这些转导器以前被认为与G蛋白/ RGS轴无关；b) RGS3抑制smad介导的基因转录；c) RGS3在T淋巴细胞中丰富，TGF-2进一步诱导其在T细胞中的表达。在T细胞中，G蛋白信号传导与向各种趋化因子的迁移有关，而TGF-2信号传导在多个水平上控制T细胞的增殖和分化。内源性RGS3在T细胞中的功能尚未被研究。根据我们的初步数据，我们假设(i) RGS3是一种多功能蛋白，除了调节G蛋白信号传导外，还调节TGF-2信号传导；（ii）内源性RGS3通过调节G蛋白和TGF-2信号传导来控制T细胞的迁移、增殖和分化。为了验证这些假设，我们提出了三个具体目标：(i)通过RGS3及其突变体的过表达来研究RGS3 / Smad相互作用的分子性质和功能后果；（ii）研究内源性RGS3在EL4 T胸腺瘤细胞系中对G蛋白和TGF-2信号的调节；（iii）研究RGS3如何控制T细胞迁移、增殖和分化，以响应TGF-2和趋化因子，使用来自RGS3敲除小鼠的T细胞。这项研究的根本意义在于可能发现RGS3作为TGF-2信号调节因子的一种新的非规范功能。这项研究的实际意义在于了解与T细胞异常免疫反应相关的疾病。

DESCRIPTION (provided by applicant): Regulator of G protein signaling RGS3 is a GTPase-activating protein (GAP) that binds G-alpha subunits of heterotrimeric G proteins and accelerates their GTPase activity. We and others have shown that through this mechanism, RGS3 regulates the signaling of Gq- and Gi-coupled receptors to angiotensin II, endothelin-1, carbachol, gonadotropin-releasing hormone and sphingosine-1 phosphate. Our new data suggest that a) RGS3 interacts with the transducers of TGF-2 signaling, Smad transcription factors that were previously thought to be unrelated to G protein / RGS axis; b) RGS3 inhibits Smad-mediated gene transcription; and c) RGS3 is abundant in T-lymphocytes and its expression in T cells is further induced by TGF-2 treatment. In T cells, G protein signaling is associated with migration towards various chemokines, whereas TGF-2 signaling controls proliferation and differentiation of T cells at multiple levels. The function of endogenous RGS3 has not been investigated in T cells. Based on our preliminary data, we hypothesize that (i) RGS3 is a multifunctional protein that, in addition to regulating G protein signaling, also modulates the signaling of TGF-2, and (ii) endogenous RGS3 controls T cell migration, proliferation and differentiation through the regulation of both G protein- and TGF-2 signaling. To test these hypotheses, we propose three specific aims: (i) investigate the molecular nature and functional consequences of RGS3 / Smad interaction by overexpression of RGS3 and its mutants, (ii) investigate the regulation of G protein- and TGF-2 signaling by endogenous RGS3 in EL4 T thymoma cell line; and (iii) examine how RGS3 controls T cell migration, proliferation and differentiation in response to TGF-2 and chemokines, using T cells from RGS3-knockout mouse. The fundamental significance of this study relates to a potential discovery of a novel, non-canonical function of RGS3 as a regulator of TGF-2 signaling. The practical importance of this study relates to understanding the diseases associated with abnormal immune responses of T cell. PUBLIC HEALTH RELEVANCE: Appropriate function of T lymphocytes is critical for the adaptive immunity, whereas abnormal function of T cells leads to autoimmune and inflammatory diseases such as asthma, multiple sclerosis, rheumatoid arthritis, type I diabetes and others. Therefore, defining the molecular mechanisms of T cell activation and differentiation may lead to a better understanding the pathogenesis of these diseases.