Novel functions of RGS3

描述（由申请人提供）：G蛋白信号转导调节剂RGS 3是一种GTP酶激活蛋白（GAP），其结合异源三聚体G蛋白的G-α亚基并加速其GTP酶活性。我们和其他人已经表明，通过这种机制，RGS 3调节Gq-和Gi-偶联受体的信号传导到血管紧张素II，内皮素-1，卡巴胆碱，促性腺激素释放激素和鞘氨醇-1磷酸。我们的新数据表明：a）RGS 3与TGF-2信号转导因子、以前被认为与G蛋白/ RGS轴无关的Smad转录因子相互作用; B）RGS 3抑制Smad介导的基因转录; c）RGS 3在T淋巴细胞中丰富，并且其在T细胞中的表达被TGF-2处理进一步诱导。在T细胞中，G蛋白信号传导与向各种趋化因子的迁移相关，而TGF-2信号传导在多个水平上控制T细胞的增殖和分化。尚未在T细胞中研究内源性RGS 3的功能。基于我们的初步数据，我们假设（i）RGS 3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的信号传导，和（ii）内源性RGS 3通过调节G蛋白和TGF-2信号传导来控制T细胞迁移、增殖和分化。为了验证这些假设，我们提出了三个具体的目标：（i）通过RGS 3及其突变体的过表达来研究RGS 3/ Smad相互作用的分子性质和功能后果;（ii）研究内源性RGS 3在EL 4 T胸腺瘤细胞系中对G蛋白和TGF-2信号转导的调节;和（iii）使用来自RGS 3敲除小鼠的T细胞，检测RGS 3如何控制T细胞响应TGF-2和趋化因子的迁移、增殖和分化。这项研究的基本意义涉及到一个新的，非典型的RGS 3作为TGF-2信号转导调节功能的潜在发现。本研究的实际意义在于了解与T细胞异常免疫应答相关的疾病。 公共卫生相关性：T淋巴细胞的适当功能对于适应性免疫至关重要，而T细胞的异常功能导致自身免疫性和炎性疾病，如哮喘、多发性硬化、类风湿性关节炎、I型糖尿病等。因此，确定T细胞活化和分化的分子机制可能会导致更好地理解这些疾病的发病机制。

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.