CONTROL OF G PROTEIN SIGNALING: ROLE OF THE RGSS

G 蛋白信号传导的控制：RGSS 的作用

• 批准号: 6288950
• 负责人: JOHN H KEHRL
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6288950
• 关键词: G protein; biological signal transduction; gene targeting; genetically modified animals; human tissue; laboratory mouse; protein sequence; protein structure function; receptor coupling; recombinant proteins; yeasts

We have discovered a protein family termed RGSs that impair signal transduction through pathways that use seven transmembrane receptors and heterotrimeric G proteins. Such receptors, when activated following the binding of a ligand such as a hormone or chemokine, trigger the G alpha subunit to exchange GTP for GDP; this causes the dissociation of G alpha and G beta-gamma subunits and downstream signaling. RGS proteins bind G alpha subunits and function as GTPase activating proteins (GAPs), thereby deactivating the G alpha subunit and facilitating their re-association with G beta-gamma. We have shown that RGS proteins modulate signaling through chemokine receptors and that they can inhibit chemotaxis. RGS1 expressing B lymphocytes fail to migrate in response to the chemokine SDF-1. Conversely, RGS1 deficient B cells obtained from mice in which the RGS1 gene has been disrupted by gene targeting have an enhanced chemotaxic response to SDF-1. Also, RGS proteins can inhibit the intracellular signaling triggered by a constitutively active G-protein coupled receptor (GPCR) such as the Kaposi?s sarcoma-associated herpes virus (KSHV-GPCR). The KSHV-GPCR has been shown to activate the Gi, Gq, G12 subfamilies of heterotrimeric G- proteins. Certain RGS proteins, in particular RGS2 and RGS3, are very efficient inhibitors of Gq signaling. Their effectiveness depends on the N-terminus of the RGS protein plus the RGS domain, the region required for its GAP activity. Certain key residues in the N-terminus have been identified as important. We have also shown that certain RGS proteins can directly inhibit the activation of adenylyl cyclase, thereby providing a mechanism by which certain RGS proteins can inhibit Gs induced cAMP production. We have demonstrated that RGS14 is highly expressed in lymphocytes and its expression levels are modulated by signaling through the B-cell and T-cell antigen receptors. RGS14 is also unique in that it is an inhibitor of G13 signaling. A yeast two- hybrid screen with RGS14 has been completed and several novel genes have been identified that encode proteins that interact with RGS14. To study the role of RGS proteins in lymphocyte development and function, RGS1 and RGS14 have been transgenically overexpressed. The consequences of their transgenic expression are now being analyzed. Furthermore RGS1 gene targeting has been accomplished and RGS3 and RGS14 are in progress. To study the consequences of persistent heterotrimeric G- protein signaling in lymphocyte development and function, transgenic mice expressing GTPase deficient G12 and G15 are being created. RGS3 and RGS4 have been shown to be phosphorylated and this phosphorylation is likely important in their translocation from the cytosol to membrane. - RGS, G-protein, chemokine, chemotaxis, lymphocytes, cAMP.

我们已经发现了一个蛋白质家族，称为RGSs，通过使用七个跨膜受体和异源三聚体G蛋白的途径损害信号转导。当这些受体在与配体如激素或趋化因子结合后被激活时，触发G α亚基将GTP交换为GDP;这导致G α和G β-γ亚基的解离和下游信号传导。RGS蛋白结合G α亚基并作为GTP酶激活蛋白（GAP）起作用，从而使G α亚基失活并促进它们与G β-γ的再结合。我们已经证明RGS蛋白通过趋化因子受体调节信号传导，并且它们可以抑制趋化性。表达RGS 1的B淋巴细胞不能响应趋化因子SDF-1而迁移。相反，从其中RGS 1基因已通过基因靶向被破坏的小鼠获得的RGS 1缺陷型B细胞对SDF-1具有增强的趋化性应答。此外，RGS蛋白可以抑制由组成型活性G蛋白偶联受体（GPCR），如卡波西？肉瘤相关疱疹病毒（KSHV-GPCR）。已显示KSHV-GPCR激活异源三聚体G蛋白的Gi、Gq、G12亚家族。某些RGS蛋白，特别是RGS 2和RGS 3，是非常有效的Gq信号传导抑制剂。它们的有效性取决于RGS蛋白的N-末端加上RGS结构域，其GAP活性所需的区域。N-末端的某些关键残基已被鉴定为重要的。我们还表明，某些RGS蛋白可以直接抑制腺苷酸环化酶的激活，从而提供了一种机制，通过这种机制，某些RGS蛋白可以抑制Gs诱导的cAMP产生。我们已经证明RGS 14在淋巴细胞中高度表达，并且其表达水平通过B细胞和T细胞抗原受体的信号传导来调节。RGS 14的独特之处还在于它是G13信号传导的抑制剂。用RGS 14进行的酵母双杂交筛选已经完成，并且已经鉴定了几个编码与RGS 14相互作用的蛋白质的新基因。为了研究RGS蛋白在淋巴细胞发育和功能中的作用，已转基因过表达RGS 1和RGS 14。目前正在分析其转基因表达的后果。此外，RGS 1基因靶向已经完成，RGS 3和RGS 14正在进行中。为了研究持续的异源三聚体G蛋白信号传导在淋巴细胞发育和功能中的后果，正在建立表达GT3缺陷型G12和G15的转基因小鼠。RGS 3和RGS 4已被证明是磷酸化的，并且这种磷酸化可能在它们从胞质溶胶到膜的易位中是重要的。- RGS，G蛋白，趋化因子，趋化性，淋巴细胞，cAMP。