Ion Conductances in the Retinal Pigment Epithelium

摘要 光感受器的健康和完整性关键取决于其胞外的组成和体积。 微环境。调节视网膜下间隙的离子成分和体积是通过 离子和水通过视网膜色素上皮(RPE)的运输，RPE是一种多功能的单层 细胞并列在感光细胞外段和脉络膜血供之间。RPE传输是 这是一组不同的离子转运蛋白和驻留在ITS中的通道协调活动的结果 根尖膜和基底侧膜。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光感受器的变化 微环境。扰乱这些运输过程或其监管可能会造成不利的变化 视网膜下间隙，导致视网膜疾病。这些通道和转运体也负责 维持RPE细胞的细胞内组成，如果受到干扰，可能会对其他关键因素产生不利影响 RPE的功能，如吞噬、光感受器外段的降解和维生素A 运输和新陈代谢。我们的总体目标是了解钾(K+) 通道参与调节视网膜下液体的体积和离子组成 空间和RPE细胞质。最近的研究发现，在RPE中存在一种外向整流钾电流 这类似于神经元中的M型电流。这项建议的具体目的是：(1)确定 RPE中构成M型电导的KCNQ通道的亚基组成；(2)确定 M型电导是局限于根尖膜还是基底侧膜；(3)确定 M型电导受药理药剂和已知的信号通路调节 KCNQ通道的特定类型；以及(4)确定M型电导在调节 RPE细胞体积。这些目标将使用分子、生物化学、 免疫组织化学、成像和电生理技术研究M型通道结构， 功能和监管。这些研究的结果将使人们更好地理解这些 至关重要的运输蛋白在RPE中发挥作用，以帮助维持健康的光感受器 微环境。

ABSTRACT 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 the subretinal space is accomplished by the transport of ions and water across the retinal pigment epithelium (RPE), a multifunctional 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 channels and transporters are also responsible for maintaining the intracellular composition of the RPE cell, which, if disturbed, could adversely affect other key RPE functions such as phagocytosis, the degradation of photoreceptor outer segments, and 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. Recent studies have identified in the RPE an outwardly rectifying K+ current that resembles the M-type current in neurons. The specific aims of this proposal are to: (1) determine the subunit composition of KCNQ channels that underlie the M-type conductance in the RPE; (2) determine whether the M-type conductance is localized to the apical or basolateral membrane; (3) determine whether the M-type conductance is modulated by pharmacologic agents and signaling pathways known to modulate specific types of KCNQ channels; and (4) determine the role of the M-type conductance in the regulation of RPE cell volume. These aims will be pursued using a combination of molecular, biochemical, immunohistochemical, imaging, and electrophysiological techniques to investigate M-type channel structure, function, and regulation. The outcome of these studies will result in a better understanding of how these critically important transport proteins operate in the RPE to help maintain a healthy photoreceptor microenvironment.