VISUAL TRANSDUCTION IN RETINAL PHOTORECEPTORS

拟议研究的长期目标是了解 详细的细胞机制的视觉转导视网膜 视杆和视锥光感受器。 第一个具体目标是了解更多关于光适应和 视杆细胞中潜在的Ca++反馈。 特别是，我们希望 检查：a）cGMP门控通道对Ca++的选择性的任何变化 在背景光下，B）鸟苷酸环化酶（鸟苷酸环化酶）与蛋白质之间的关系。 cGMP合成酶）和Ca++在接近生理条件下， c）任何独立于背景光的残余背景光适应， Ca++反馈和d）电压依赖性电导的任何贡献 视杆细胞的电压响应所示的光适应。 第二个具体目标是更多地了解 视锥细胞的光传导机制和光适应。 在 特别是，我们希望找出：a）是否暗代谢通量为 cGMP比在杆中更快，B）锥细胞的调节是否 钙离子对鸟苷酸环化酶的影响与视杆细胞类似 酶，以及c）在锥体上进行的各种测量是否可以 整合在一个简单的模型中，以预测锥体的反应行为， 光 第三个具体目标是表征视网膜cGMP激活的 分子水平上的通道。 我们希望：a）使结构-功能 通过定点突变对杆状通道的相关性研究 以及在杆通道之间的嵌合通道的构造， 嗅觉纤毛中的同源通道，和B）分子克隆 在视锥细胞和可能在视网膜的其他地方的cGMP门控通道。 电生理实验将在两栖动物身上进行 视杆细胞和视锥细胞以及哺乳动物的视锥细胞。 的分子生物学 将进行研究和并行的电气测量， 来自人视网膜cDNA的cGMP激活通道 图书馆 光转导过程的详细知识对于 了解影响光感受器的各种疾病，例如 视网膜色素变性

The long-term objective of the proposed research is to understand in detail the cellular mechanisms underlying visual transduction in retinal rod and cone photoreceptors. The first specific aim is to understand more about light adaptation and the underlying Ca++ feedback in rods. In particular, we hope to examine: a) any change in the cGMP-gated channel's selectivity for Ca++ in background light, b) the relation between guanylate cyclase (the cGMP-synthesizing enzyme) and Ca++ under near-physiological conditions, c) any residual background light adaptation that is independent of the Ca++ feedback and d) any contribution of voltage-dependent conductances to the light adaptation shown by the voltage response of rods. The second specific aim is to understand more about the phototransduction mechanism and light adaptation in cones. In particular, we hope to find out: a) whether the dark metabolic flux for cGMP is faster than in rods, b) whether the modulation of the cone guanylate cyclase by Ca++ is quantitatively similar to that for the rod enzyme, and c) whether the various measurements made on cones can be integrated in a simple model to predict the cone's response behavior to light. The third specific aim is to characterize the retinal cGMP-activated channels at a molecular level. We hope to: a) make structure-function correlation studies of the rod channel through site-directed mutagenesis as well as construction of chimeric channels between the rod channel and a homologous channel in olfactory cilia, and b) molecularly clone the cGMP-gated channels in cones and possibly elsewhere in the retina. The electrophysiological experiments will be carried out on amphibian rods and cones as well as mammalian cones. The molecular biological studies, together with parallel electrical measurements, will be carried out on cGMP-activated channels derived from a human retinal cDNA library. A detailed knowledge of the phototransduction process is important for understanding various diseases affecting photoreceptors, such as retinitis pigmentosa.