Ion Conductances in the Retinal Pigment Epithelium

描述（由申请人提供）：光感受器的健康和完整性主要取决于其细胞外微环境的组成和体积。通过离子和水穿过视网膜色素上皮（RPE）的运输来实现对该所谓的视网膜下空间的离子组成和体积的调节，视网膜色素上皮（RPE）是感光体外节和脉络膜血液供应之间并置的单层细胞。 RPE转运是位于其顶膜和基底外侧膜中的不同离子转运蛋白和通道组的协调活性的结果。随着视网膜活动的变化，视网膜细胞释放的化学信号扩散到RPE，并启动其运输的调整，以补偿感光细胞微环境的改变。这些运输过程或其调节的中断可能导致视网膜下腔的不利变化，从而导致视网膜疾病。这些转运途径也负责维持RPE细胞的细胞内组成，如果受到干扰，可能会对其他关键RPE功能（如维生素A转运和代谢）产生不利影响。我们的总体目标是了解钾（K+）通道参与调节视网膜下腔和RPE细胞质中液体的体积和离子组成的机制。具体目标是：（1）确定RPE中M型K+通道的分子基础，（2）确定除Kir7.1以外的内向整流K+（Kir）通道亚基是否参与RPE的K+电导，（3）了解Kir7.1通道是如何受细胞内pH的生理变化调节的，（4）了解K+通道的分子机制。（4）阐明M型K+通道的受体激活和抑制之间的信号转导途径。这些目标将采用分子和电生理技术相结合的方法来研究K+通道的结构、功能和调节。这些研究的结果将更好地了解这些至关重要的转运蛋白如何在RPE中运作，以维持健康的感光细胞微环境。

DESCRIPTION (provided by applicant): The health and integrity of photoreceptors critically depend on the composition and volume of their extracellular microenvironment. Regulation of the ionic composition and volume of this so-called subretinal space is accomplished by the transport of ions and water across the retinal pigment epithelium (RPE), a monolayer of cells juxtaposed between the photoreceptor outer segments and the choroidal blood supply. RPE transport is the result of the coordinated activity of a diverse group of ion transport proteins and channels residing in its apical and basolateral membranes. With changes in retinal activity, chemical signals released by retinal cells diffuse to the RPE and initiate adjustments in its transport to compensate for alterations in the photoreceptor microenvironment. Disruption of these transport processes or their regulation may cause adverse changes in the subretinal space, contributing to retinal disease. These transport pathways are also responsible for maintaining the intracellular composition of the RPE cell, which, if disturbed, could adversely affect other key RPE functions such as vitamin A transport and metabolism. Our overall goal is to understand the mechanisms by which potassium (K+) channels participate in the regulation of the volume and ionic composition of the fluid in both the subretinal space and the RPE cytoplasm. The specific aims are: (1) To determine the molecular basis for the M-type K+ channel in the RPE; (2) To ascertain whether inwardly rectifying K+ (Kir) channel subunits other than Kir7.1 contribute to the RPE K+ conductance; (3) To understand how the Kir7.1 channel is modulated by physiological changes in intracellular pH; and (4) To elucidate the signal transduction pathway linking receptor activation and inhibition of M-type K+ channels. These aims will be pursued using a combination of molecular and electrophysiological techniques to investigate K+ channel structure, function, and regulation. The outcome of these studies will be a better understanding of how these critically important transport proteins operate in the RPE to maintain a healthy photoreceptor microenvironment.