INACTIVATION AND ADAPTATION OF THE ROD PHOTORESPONSE

视杆细胞感光反应的失活和适应

• 批准号: 3264615
• 负责人: NANCY J MANGINI
• 金额: $ 6.63万
• 依托单位: UNIVERSITY OF ILLINOIS AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-03-01 至 1991-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3264615
• 关键词: Anura; autoradiography; biological signal transduction; cyclic GMP; dark adaptation; fresh water environment; gel electrophoresis; immunochemistry; light adaptations; methylation; phosphodiesterase I; radioassay; retina degeneration; retinitis pigmentosa; rhodopsin; rod cell; vision; visual photoreceptor

Signal transduction in rod photoreceptors begins with light activation of rhodopsin and ends with a decrease in the intracellular level of cyclic GMP. The decrease in cGMP is what the rod uses to produce an electrical signal. The recovery of cGMP level, and termination of the light-induced signal depends on the deactivation of a rod cell component called phosphodiesterase (PDE). A defect in PDE -- or in one of the components that regulate PDE activity -- will result both in abnormal levels of cGMP, and in poor vision. For example, retinitis pigmentosa (RP) is a group of disorders that causes retinal degeneration. An early symptom of RP is night blindness. One hypothesis for the underlying basis for sensitivity deficits in RP patients, is that cGMP metabolism in rods is defective. Testing this hypothesis requires an understanding of the role each cellular component plays in the light activation and subsequent deactivation of PDE. The long term objectives of this application are (i) to examine processes involved in the inactivation and adaptation of the photoresponse in normal vision, and (ii) to examine whether defects in these processes underlie visual dysfunctions that occur in diseases such as RP. One specific objective of this research is to examine the effect of light on the cellular localization and metabolic regulation of a retinal protein designated "48K", "S- antigen" or "arrestin" that has been shown to quench light activation of PDE. A second specific objective is to examine whether reversible methylation of PDE is a mechanism for regulating PDE activity in the presence of steady background illumination. These studies will provide normative data about processes that are central to the regulation of PDE activity in rods. In view of (i) the role of PDE in the regulation of cGMP levels (ii) the central role of cGMP in phototransduction, and (iii) data indicating that abnormal cGMP metabolism can result in poor vision, proposed experiments will provide much needed information about processes that may underlie certain forms of retinal degenerative diseases such as RP. To achieve these goals, the following experiments are proposed: 1) To examine whether light induces a migration of 48K from the inner segment of rod photoreceptor to the outer segment. Experiments involve quantitation of 48K in dark- (DA) vs. light- adapted (LA) rod outer segments. 2) To measure the turnover rate of 48K in DA rod photoreceptors, and to examine whether light adaptation affects turnover rate of 48K. Experiments involve radioactive labeling of retinal proteins, and determination of specific activity of 48K in retinal subcellular fractions. 3) To examine whether reversible methylation of PDE is involved in adaptational processes in rods.

视杆细胞光感受器的信号转导始于光 视紫红质的激活，并以减少 细胞内cGMP水平。 cGMP的减少是什么 用来产生电信号 的恢复 cGMP水平，并且光诱导信号的终止取决于 一种视杆细胞成分的失活 磷酸二酯酶（PDE）。 PDE中的缺陷--或者 调节PDE活性的组分-将导致 cGMP水平异常，视力差。 比如说， 视网膜色素变性（RP）是一组引起视网膜色素变性的疾病， 视网膜变性 RP的早期症状是夜盲症。 一个假设的基础上的敏感性赤字， RP患者，是在杆cGMP代谢缺陷。 检验这一假设需要了解每一个 细胞成分在光激活和随后的 PDE失活。 本申请的长期目标是（i）检查 参与失活和适应的过程， 正常视力的光反应，以及（ii）检查是否 这些过程中的缺陷导致视觉功能障碍， 在疾病如RP。 这项研究的一个具体目标是 研究光对细胞定位的影响， 视网膜蛋白质的代谢调节，称为“48 K”、“S-K”、“S 已经显示出猝灭光的“抗原”或“抑制蛋白 激活PDE。 第二个具体目标是审查 PDE的可逆甲基化是否是 在稳定背景存在下调节PDE活性 照明。 这些研究将提供规范性数据， 这些过程是调节PDE活性的核心， 棒。 鉴于（i）PDE在cGMP调节中的作用 水平（ii）cGMP在光转导中的中心作用，和（iii） 数据表明cGMP代谢异常可导致 视力差，拟议的实验将提供急需的 关于可能构成某些形式的 视网膜变性疾病，如RP。 为了实现这些目标， 建议进行以下实验： 1)为了检查光是否会引起48 K从 视杆细胞内节到外节。 实验涉及在黑暗中定量48 K-（DA）与光照- 适配（LA）棒外节段。 2)测量DA棒中48 K的周转率 光感受器，并检查光适应是否影响 周转率48 K。 实验涉及放射性标记的 视网膜蛋白质和测定48 K的比活性， 视网膜亚细胞组分。 3)研究PDE的可逆甲基化是否涉及 in adaptation适应processes过程in rods杆.