CONTROL OF G PROTEIN SIGNALING: ROLE OF THE RGSS

我们已经发现了一个名为RGSs的蛋白质家族，它通过使用七种跨膜受体和异源三聚体G蛋白的途径损害信号转导。这些受体在与配体（如激素或趋化因子）结合后被激活，触发G α亚基将GTP交换为GDP；这导致G α和G β - γ亚基的分离和下游信号传导。RGS蛋白结合G α亚基并作为GTPase激活蛋白（gap）发挥作用，从而使G α亚基失活并促进其与G β - γ的重新结合。我们已经证明RGS蛋白通过趋化因子受体调节信号，并且它们可以抑制趋化性。表达RGS1的B淋巴细胞在趋化因子SDF-1的作用下无法迁移。相反，从RGS1基因被基因靶向破坏的小鼠中获得的RGS1缺陷B细胞对SDF-1的趋化反应增强。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）。KSHV-GPCR已被证明可以激活异三聚体G-蛋白的Gi、Gq、G12亚家族。某些RGS蛋白，特别是RGS2和RGS3，是非常有效的Gq信号抑制剂。它们的有效性取决于RGS蛋白的n端和RGS结构域，这是其GAP活性所需的区域。n端某些关键残基已被确定为重要残基。我们还发现某些RGS蛋白可以直接抑制腺苷酸环化酶的激活，从而提供了某些RGS蛋白可以抑制Gs诱导的cAMP产生的机制。我们已经证明RGS14在淋巴细胞中高表达，其表达水平通过b细胞和t细胞抗原受体的信号传导调节。RGS14的独特之处在于它是G13信号的抑制剂。酵母与RGS14的双杂交筛选已经完成，并且已经鉴定出几个编码与RGS14相互作用蛋白的新基因。为了研究RGS蛋白在淋巴细胞发育和功能中的作用，我们对RGS1和RGS14进行了转基因过表达。他们转基因表达的后果现在正在分析中。RGS1基因的靶向研究已经完成，RGS3和RGS14正在进行中。为了研究持续异三聚体G-蛋白信号在淋巴细胞发育和功能中的影响，我们创建了表达GTPase缺陷G12和G15的转基因小鼠。RGS3和RGS4被磷酸化，这种磷酸化可能在它们从细胞质转移到膜的过程中很重要。- RGS， g蛋白，趋化因子，趋化性，淋巴细胞，cAMP。

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.