G PROTEIN PATHWAYS AND REGULATION IN RPE CELLS

视网膜色素上皮（RPE）功能的调节可能 涉及优先在RPE中表达的受体和G蛋白 细胞我们过去在RPE细胞中鉴定新型G蛋白的努力， 成功了我们还研究了G蛋白信号传导机制 通过分子克隆RPE特异性cDNA， 信号转导通路的组成部分。我们最近的发现表明 一个独特的受体介导的G蛋白偶联过程的存在， RPE细胞 我们已经在牛RPE细胞中鉴定了一种新的G蛋白偶联受体， 暂时称为RPE-视网膜G蛋白偶联受体或RGR。 这种新的七螺旋受体是值得注意的同源，亚家族 的视觉色素，它已被证明是通过原位杂交， 在RPE细胞、内核层细胞中选择性表达， 神经节细胞层的特定细胞。它不是在 光感受器，或在视网膜以外的组织中，除了可能的 个脑袋 这种受体在RPE中的定位，高水平的 其mRNA的表达及其与视色素的同源性表明， 这种受体的功能在视觉过程中很重要 涉及RPE。 RGR基因可能编码一种新的视蛋白同源物，结合视黄醇。 它的功能可能是催化视黄醇异构化或作为 11-顺式-视黄醛的捕获蛋白。RGR的替代功能可以是 通过结合活化的 配体并偶联至异源三聚体G蛋白。我们预测RGR 基因在脊椎动物中高度保守。RPE中RGR的丰度 细胞会强烈表明它参与了一个重大的， RPE的特殊作用。 我们将测试这些和其他假设的生化特性， RGR基因产物。这项建议的目的是进一步 表征RGR基因，确定推定的受体功能， RGR，并阐明RPE中专门的G蛋白通路和调节 细胞这种选择性表达的视蛋白或 视色素同系物为进一步研究提供了一个切入点 RPE的功能、分化和疾病。

Regulation of the functions of the retinal pigment epithelium (RPE) may involve receptors and G proteins that are expressed preferentially in RPE cells. Our past efforts to identify novel G proteins in RPE cells have been successful. We have also investigated G protein signaling mechanisms in RPE cells by molecular cloning of RPE-specific cDNAs that may encode the components of signal transduction pathways. Our recent findings point to the presence of a unique receptor-mediated G protein-coupled process in the RPE cell. We have identified in bovine RPE cells a novel G protein-coupled receptor, tentatively referred to as RPE-retinal G protein-coupled receptor or RGR. This novel heptahelical receptor is notably homologous, to the subfamily of visual pigments, and it has been shown by in situ hybridization to be selectively expressed in RPE cells, cells in the inner nuclear layer, and specific cells of the ganglion cell layer. It is not expressed in the photoreceptors, or in tissues other than the retina, except possibly the brain. The localization of this receptor in the RPE, the high level of expression of its mRNA, and its homology to the visual pigments suggest that the function of this receptor is important in the visual process involving the RPE. The RGR gene may encode a novel opsin homologue that binds retinaldehyde. Its function may be to catalyze retinaldehyde isomerization or act as a trapping protein for 11-cis-retinal. An alternative function of RGR may be to mediate a novel G protein response pathway by binding to an activating ligand and coupling to a heterotrimeric G protein. We predict that the RGR gene is highly conserved in vertebrates. The abundance of RGR in the RPE cell would strongly suggest that it participates in a major and specialized role of the RPE. We will test these and other hypotheses by biochemical characterization of the RGR gene product. The objectives of this proposal are to further characterize the RGR gene, determine the putative receptor function of RGR, and elucidate specialized G protein pathways and regulation in RPE cells. The molecular cloning of this selectively expressed opsin or retinochrome homologue provides an entry point for further investigation of RPE function, differentiation, and disease.