ION CONDUCTANCES IN THE RETINAL PIGMENT EPITHELIUM

光感受器的健康和完整性关键取决于其细胞外微环境的组成和体积。这个所谓的视网膜下空间的离子组成和体积的调节是通过跨视网膜色素上皮(RPE)的离子、水和代谢物的运输完成的，RPE是并列在光感受器外段和脉络膜血供之间的单层细胞。RPE转运是一组不同的离子泵、共转运体、交换器和驻留在根尖和基侧膜上的通道协同活动的结果。随着视网膜活动的变化，视网膜细胞释放的化学信号也扩散到RPE，在那里运输被调整以补偿光感受器微环境的变化。这些运输过程的中断或它们的调节可能会导致视网膜下腔的不利变化，从而导致视网膜疾病。这些转运途径还负责维持RPE细胞的细胞内成分，如果受到干扰，可能会对其他关键的RPE功能产生不利影响，如维生素A的运输和代谢。我们的总体目标是了解钾(K+)通道参与调节视网膜下间隙和RPE细胞质中液体的体积和离子组成的机制。其具体目的是：(1)确定RPE内向整流钾(KIR)电导的分子基础；(2)确定细胞内ATP调节KIR通道的机制；(3)了解KIR通道是如何受细胞内pH的生理变化调节的；以及(4)检验另一种K+通道，即M型K+通道，是由花生四烯酸代谢产物介导的容量诱导激活的假说。这些目标将利用分子和电生理技术的组合来研究K+通道的结构、功能和调节。这些研究的结果将是更好地了解这些至关重要的运输蛋白如何在RPE中运作，以维持健康的光感受器微环境。

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, water, and metabolites 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 pumps, co-transporters , exchangers, and channels residing in the apical and basolateral membranes. With changes in retinal activity, chemical signals released by retinal cell diffuse too the RPE where transport is adjusted to compensate for alteration 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 in 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 inwardly rectifying K+ (Kir) conductance of the RPE; (2) To determine the mechanism underlying the regulation of the Kir channel by intracellular ATP; (3) To understand how the Kir channel is modulated by physiological changes in intracellular pH; and (4) To test the hypothesis that volume-induced activation of another K+ channel, an M-type K+ channel, is mediated by arachidonic acid metabolites. 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.