The Light-Dependent Cation Channel of Fly Photoreceptors

感光细胞对光的反应有一系列的步骤。在脊椎动物的眼睛中，环GMP是光感受器中的一种化合物，当细胞被照亮时，其内部浓度会增加。cGMP浓度的增加触发细胞膜通道的打开，允许离子穿过细胞膜。由于离子携带电荷，它们的运动产生称为受体电位的电事件。尽管无脊椎动物提供了理解这一重要特征发育和调节的遗传基础的希望，但人们对无脊椎动物光感受器中依赖光的阳离子通道知之甚少。果蝇以其在基因研究中的应用而闻名，并且有各种各样的突变菌株可供使用。本项目将研究果蝇的光依赖性阳离子通道，使用一种新开发的体外制剂，可以进入细胞膜进行膜片钳记录的电生理技术。建立通道开启和关闭的特性，并与脊椎动物光感受器的特性进行比较。生物化学化合物将确定控制通道的开放，以比较cGMP在脊椎动物光感受器中的作用。将筛选果蝇的视觉突变体，以确定可能决定控制这一重要膜成分的基因的结构或功能的基因。这项工作将直接导致基因操作的前景，允许对这些通道进行结构分析；这种对感觉传导中重要蛋白质的分析将对所有感觉科学产生重大影响。

A photoreceptor cell responds to light in a series of steps. In the vertebrate eye, cyclic GMP is a compound in the photoreceptors that increases in internal concentration when the cell is illuminated. The increased concentration of cGMP then triggers opening of channels in the cell membrane that allow ions to cross it. Since the ions carry electrical charge, their movement produces the electrical event called the receptor potential. Very little is known about the light-dependent cation channel in photoreceptors of invertebrates, although invertebrates offer the promise of understanding the genetic basis for the development and regulation of this important feature. The fruit fly, Drosophila, is well-known for its use in genetic studies, and a wide variety of mutant strains are available. This project will study light-dependent cation channel in flies, using a newly developed preparation in vitro that allows access to cell membranes for the electrophysiological technique of patch-clamp recording. The properties of channel opening and closing will be established and compared with those for vertebrate photoreceptors. Biochemical compounds will identified that control the opening of the channel to compare to the cGMP role in the vertebrate photoreceptors. Visual mutants of Drosophila will be screened to identify possible genes that determine the structure or function of the genes controlling this important membrane component. This work will lead directly to the promise of genetic manipulation allowing structural analysis of these channels; such analysis of proteins important in sensory transduction will have substantial impact on all sensory science.