CONTROL OF G PROTEIN SIGNALING: ROLE OF THE RGSS

我们已经发现了一个被称为RGSS的蛋白质家族，它通过使用七个跨膜受体和异源三聚体G蛋白的途径来损害信号转导。当这种受体在激素或趋化因子等配体结合后被激活时，会触发Gα亚基将GTP交换为GDP；这导致Gα和Gβ-伽马亚基的解离和下游信号。RGS蛋白与Gα亚基结合，作为GTPase激活蛋白(GAP)发挥作用，从而使Gα亚基失活，并促进其与Gβ-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作用。表达RGS1的B淋巴细胞不能对趋化因子SDF-1做出反应。相反，从RGS1基因被基因打靶干扰的小鼠获得的RGS1缺陷的B细胞对SDF-1的趋化反应增强。此外，RGS蛋白还可以抑制由G蛋白偶联受体(G蛋白偶联受体)如卡波西S肉瘤相关疱疹病毒(KSHV GPCR)触发的细胞内信号转导。KSHV-GPCR已被证明能激活异源三聚体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端加上RGS结构域，RGS结构域是其GAP活性所需的区域。N-末端的某些关键残基已被确定为重要的。我们还发现，某些RGS蛋白可以直接抑制腺酰环化酶的激活，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，RGS14在淋巴细胞中高度表达，其表达水平受B细胞和T细胞抗原受体信号的调节。RGS14也是独一无二的，因为它是G13信号的抑制因子。一个带有RGS14的酵母双杂交筛选已经完成，并且已经确定了几个新的编码与RGS14相互作用的蛋白的基因。为了研究RGS蛋白在淋巴细胞发育和功能中的作用，RGS1和RGS14已被转基因过表达。他们转基因表达的后果现在正在分析中。此外，RGS1基因打靶已经完成，RGS3和RGS14正在进行中。为了研究持续异源三聚体G蛋白信号在淋巴细胞发育和功能中的后果，正在建立表达GTPase缺陷的G12和G15的转基因小鼠。RGS3和RGS4已经被证明是磷酸化的，这种磷酸化可能在它们从细胞质到膜的转位中起重要作用。-RGS、G蛋白、趋化因子、趋化作用、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.