ROLE OF CYCLIC GMP IN PHOTORECEPTOR FUNCTION

这项研究的目的是阐明生物化学机制，通过 CGMP对脊椎动物视杆细胞视觉转导的影响 光感受器。CGMP途径(视紫红质到 GTP结合蛋白到磷酸二酯酶)和电生理效应 全细胞记录和离体膜贴片上cGMP的表达 CGMP在光依赖性通透性调控中的作用 质膜中的作用机制。CGMP的分子机制 然而，ACTS尚未确定。 拟议研究的目的如下： (1)评估弱光是否引起cGMP总量的下降 浓度反映了cGMP浓度在 细胞质。观察到的cGMP总浓度下降幅度太小。 通过一种简单的方法对渗透性机制产生显著影响 绑定模型。然而，cGMP的亚细胞分裂为游离和 可能会出现结合池，并将通过对细胞总数进行分级来检查 CGMP以确定cGMP总量的很大一部分是否被绑定，以及 因此对磷酸二酯酶的快速光诱导水解性不敏感。 (2)确定cGMP在视杆中的可能作用部位。CGMP已知 为了对质膜的离子通透性产生影响，钙离子释放 从盘膜、蛋白激酶活性和GTP结合蛋白。 CGMP结合位点的鉴定和鉴定将导致 可通过cGMP变化进行调节的蛋白质组分的纯化 浓度和/或结合，棒的离子渗透性。 这些实验应该允许对各种模型进行更明确的测试 CGMP在视觉转导中的作用，并导致对 为什么cGMP肉代谢缺陷会导致光感受器细胞退化和 死亡。

The objective of this research is to elucidate the biochemical mechanism by which cGMP influences visual transduction in vertebrate rod photoreceptors. Both biochemical studies of the cGMP pathway (rhodopsin to GTP-bining protein to phosphodiesterase) and electrophysiological effects of cGMP on whole cell recordings and isolated membrane patches demonstrate the importance of cGMP in modulating the light-dependent permeability mechanism in the plasma membrane. The molecular mechanism by which cGMP acts has not, however, been determined. The aims of the proposed research are as follows: (1) To evaluate whether small light-induced decreases in total cGMP concentration reflect larger changes in cGMP concentration in the cytoplasm. The observed decrease in total cGMP concentration is too small to exert a significant effect on the permeability mechanism by a simple binding model. However, subcellular partitioning of cGMP into free and bound pools may occur, and will be examined by fractionating total cellular cGMP to determine whether a significant portion of total cGMP is bound and hence not sensitive to rapid light-induced hydrolysis by phosphodiesterse. (2) To identify possible sites of action of cGMP in the rod. cGMP is known to have effects on ion permeability of the plasma membrane, Ca2+ release from disc membranes, protein kinase activity, and GTP-binding protein. Identification and characterization of cGMP binding sites will lead to purification of protein components that may regulate, via changes in cGMP concentration and/or binding, the ionic permeability of the rod. These experiments should permit more definitive tests of various models for cGMP action in visual transduction, and lead to increased understanding of why defects in cGMP meatabolism lead to photoreceptor cell degeneration and death.