RPE Lactate Transporters: A Role in Retinal Survival

RPE 乳酸转运蛋白：在视网膜存活中的作用

• 批准号: 6776776
• 负责人: NANCY Jean PHILP
• 金额: $ 35.33万
• 依托单位: THOMAS JEFFERSON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6776776
• 关键词: apical membrane; basolateral membrane; biological fluid transport; carboxylate; chemical structure function; electroretinography; enzyme activity; gene expression; gene targeting; genetically modified animals; immunocytochemistry; ion transport; laboratory mouse; lactates; light microscopy; macular degeneration; molecular cloning; northern blottings; nucleic acid sequence; polymerase chain reaction; retina degeneration; retinal pigment epithelium; visual photoreceptor; water channel

DESCRIPTION (provided by applicant): The retinal pigment epithelium (RPE) maintains retinal homeostasis by regulating the transport of ions, metabolites and fluid into and out of the neural retina. The long-term goal of this proposal is to characterize the role of RPE lactate transporters in maintaining normal retinal metabolism and to determine how changes in expression of these transporters could contribute to the pathophysiology of retinal disease. Transport of lactate into and out of cells is mediated by a family of proton-coupled monocarboxylate transporters (MCTs). During the past funding period, we established that the RPE expresses two MCTs; MCT1 in the apical membrane and MCT3 in the basolateral membrane. The polarized distribution of MCT1 and MCT3 in the RPE provides a mechanism for vectorial transport of lactate from the retina to the choroid, thereby regulating the pH and osmolarity in the space surrounding the photoreceptor cells. Alteration in the expression or polarization of these transporters would be expected to lead to photoreceptor cell degeneration. While MCT1 is widely expressed, MCT3 is preferentially expressed in the RPE. We cloned the mouse and human MCT3 genes and determined that the human gene maps to chromosome 22q12.3-13.2, a locus that has been associated with macular degeneration. Recently we have found that MCTs in the RPE are not isolated proteins but rather associate with a transmembrane glycoprotein- CD147. Like MCTs, CD147 is abundant in the apical and basolateral membranes of the RPE. In the CD147 null mice there is a loss of expression of MCTs in the RPE, suggesting that subunit assembly is required for targeting of MCT1 and MCT3 to the plasma membrane. In this competitive renewal application, we have proposed an integrated series of hypothesis driven experiments designed to further our understanding of the importance of MCT3 in maintaining normal visual function. The Specific Aims of this project are: (1) to determine the mechanisms that regulate the biosynthesis, trafficking, and functional activity of MCT1 and MCT3 in the RPE; (2) to characterize the MCT3 promoter and identify elements that regulate developmental and tissue specific expression of the MCT3 gene; (3) to determine the effects of targeted deletion of the MCT3 gene on the viability and functional activity of photoreceptor cells.

描述（由申请人提供）：视网膜色素上皮（RPE）通过调节离子、代谢物和液体进出神经视网膜的运输来维持视网膜稳态。该提案的长期目标是表征 RPE 乳酸转运蛋白在维持正常视网膜代谢中的作用，并确定这些转运蛋白表达的变化如何影响视网膜疾病的病理生理学。乳酸进出细胞的转运是由质子耦合单羧酸转运蛋白 (MCT) 家族介导的。在过去的资助期间，我们确定 RPE 表达两个 MCT； MCT1 位于顶膜，MCT3 位于基底外侧膜。 RPE 中 MCT1 和 MCT3 的极化分布提供了一种将乳酸从视网膜矢量运输到脉络膜的机制，从而调节感光细胞周围空间的 pH 值和渗透压。这些转运蛋白的表达或极化的改变预计会导致感光细胞变性。 MCT1 广泛表达，而 MCT3 优先在 RPE 中表达。我们克隆了小鼠和人类的 MCT3 基因，并确定人类基因映射到染色体 22q12.3-13.2，该基因座与黄斑变性相关。最近我们发现 RPE 中的 MCT 不是孤立的蛋白质，而是与跨膜糖蛋白 CD147 相关。与 MCT 一样，CD147 在 RPE 的顶膜和基底外侧膜中含量丰富。在 CD147 缺失小鼠中，RPE 中 MCT 表达缺失，表明 MCT1 和 MCT3 靶向质膜需要亚基组装。在这个竞争性更新应用中，我们提出了一系列综合的假设驱动实验，旨在进一步了解 MCT3 在维持正常视觉功能中的重要性。该项目的具体目标是：（1）确定RPE中MCT1和MCT3的生物合成、运输和功能活性的调节机制； (2) 表征MCT3启动子并鉴定调节MCT3基因的发育和组织特异性表达的元件； (3)确定MCT3基因定向缺失对感光细胞活力和功能活性的影响。