ISOPRENOID METABOLISM IN THE RETINA

来自甲羟戊酸的类异戊二烯途径产生几种 视网膜感光细胞功能的重要产品。 的 主要产物胆固醇约占组织的2%， 重量和约6-8%的总杆外段（ROS） 膜脂 第二种产物，长叶醇磷酸酯（Dol-P）， N-连接糖蛋白中寡糖转移所需的 合成，这是将视蛋白整合到细胞中所必需的过程。 ROS膜。 关于代谢，我们知之甚少。 视网膜中的这两种脂质。 本建议旨在 缓解这一不足。 胆固醇的化学水平， 角鲨烯、Dol-P和多萜醇将由高 高效液相色谱法 de novo的作用 在类异戊二烯结合到视网膜中的合成中， ROS将通过测量 在离体视网膜中使用3 H2O和（3 H）乙酸盐进行合成。 的 （a）ROS组装的类异戊二烯合成要求 膜，（B）将视蛋白掺入ROS，和（c） 将使用抑制剂检查视蛋白的糖基化 在类异戊二烯从头途径的特定酶促步骤 生物合成 最后，为了解决是否 类异戊二烯和视蛋白通过不同的途径， 依赖功能高尔基体衍生的囊泡交通对 将测定类异戊二烯向ROS的转运。 上述研究应提供大量资料 关于从头类异戊二烯的作用和要求 用于ROS膜的组装和功能的合成。

The isoprenoid pathway from mevalonate generates several products important for retinal photoreceptor cell function. The primary product, cholesterol, represents about 2% of the tissue weight and about 6-8% of the total rod outer segment (ROS) membrane lipid. A second product, dolichyl phosphate (Dol-P), is required for oligosaccharide transfer in N-linked glycoprotein synthesis, a process essential for the integration of opsin into the ROS membrane. Very little is known regarding the metabolism of these two lipids in the retina. The present proposal is aimed at alleviating this deficiency. The chemical levels of cholesterol, squalene, Dol-P and dolichol will be determined by high performance liquid chromatography. The role of de novo synthesis in the incorporation of isoprenoids into the retina and ROS will be determined by measuring the absolute rates of synthesis in isolated retina using 3H20 and (3H)acetate. The requirement for isoprenoid synthesis for the (a) assembly of ROS membranes, (b) incorporation of opsin into ROS, and (c) glycosylation of opsin will be examined using inhibitors which act at specific enzymatic steps of the de novo pathway of isoprenoid biosynthesis. Finally, to address the question of whether isoprenoids and opsin are routed by different pathways, the dependence of functioning Golgi-derived vesicular traffic on the transport of isoprenoids to the ROS will be determined. The above studies should yield considerable information concerning the role and requirement of de novo isoprenoid synthesis for the assembly and function of ROS membranes.