CITRATE TRANSPORT IN THE PROXIMAL TUBULE

近端小管中的柠檬酸盐转运

• 批准号: 7725310
• 负责人: Kathleen S Hering-Smith
• 金额: $ 18.67万
• 依托单位: TULANE UNIVERSITY OF LOUISIANA
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7725310
• 关键词: Acids; Acute; Address; Apical; Calcium; Cell Line; Cells; Chronic; Citrate; Citrates; Computer Retrieval of Information on Scientific Projects Database; Condition; Diagnosis; Excretory function; Funding; Grant; Human; Hypokalemia; In Vitro; Individual; Institution; Kidney Calculi; Lead; Metabolic acidosis; Modeling; Nephrolithiasis; Nephrons; Physiological; Production; Proteins; Regulation; Research; Research Personnel; Resources; Source; Structure of retinal pigment epithelium; System; Transport Process; United States National Institutes of Health; Vesicle; apical membrane; base; citrate carrier; dicarboxylate; dicarboxylate-binding protein; extracellular; improved; in vitro Model; inhibitor/antagonist; mRNA Stability; novel; trafficking; uptake; urinary

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Various studies estimate that 1963% of individuals with calcium containing kidney stones have hypocitraturia as a contributing cause. Understanding the mechanisms of the regulation of citrate transport will hopefully lead to improved diagnosis of causes of hypocitraturia. Urinary citrate is an important inhibitor of calcium nephrolithiasis and is primarily determined by fractional reabsorption in the proximal tubule. The dicarboxylate transporter (NaDC1) is presumably the main mechanism of apical uptake of filtered citrate along the nephron. The most important physiologic regulator of urinary citrate excretion is acid-base status. Also urinary citrate increases as urinary calcium increases. The proposed studies will address the acute regulation of citrate transport by calcium, and chronic regulation of citrate transport by acid-base perturbations and hypokalemia. Using a newly characterized in vitro model of citrate transport, OK cells studied under particular conditions, citrate and dicarboxylate uptake are sensitive to extracellular calcium. These studies indicate that the OK cell citrate transport system is likely a novel citrate transporter. Recently another cell line of dicarboxylate transport was developed. Human retinal pigmented epithelial cells stably transfected with human NaDC1 (CUBS cells) are responsive to acid-base conditions in vitro and will therefore represent a powerful new model. Two hypotheses will be examined: 1. Calcium acutely inhibits a novel citrate transport process in mammalian proximal tubule cells. 2. Chronic regulation of proximal tubule transport of citrate is accomplished by redundant mechanisms including changes in NaDC1 protein production and insertion of pre-existing NaDC1 protein into the apical membrane from sub-apical vesicles. The specific aims are: 1. To delineate the calcium sensitive citrate transport process by: demonstrating that the calcium sensitive citrate transport process is a novel transporter, not NaDC1, and determining the cellular mechanisms whereby extracellular calcium alters this citrate transport process. 2. To delineate the mechanisms of chronic regulation of citrate transport by acid-base perturbations and hypokalemia. To achieve this aim three modes of regulation will be examined: transcriptional (or mRNA stability) regulation, regulation at the protein level, and regulation by trafficking of NaDC1 into and out of the apical membrane from sub-apical vesicles under conditions of metabolic acidosis and hypokalemia.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 各种研究估计，有1963％的含钙结石的个体具有低核性原因。 了解柠檬酸盐转运调节的机制将有望改善诊断性低下的原因。泌尿柠檬酸盐是钙肾上腺素症的重要抑制剂，主要由近端小管中的分数重吸收确定。二羧酸酯转运蛋白（NADC1）大概是沿着肾单位过滤柠檬酸盐的顶端吸收的主要机制。柠檬酸尿液排泄的最重要的生理调节剂是酸碱状态。随着泌尿钙的增加，柠檬酸盐也会增加。拟议的研究将针对钙对柠檬酸盐转运的急性调节，以及通过酸碱扰动和低钾血症对柠檬酸盐转运的慢性调节。使用新特征的柠檬酸盐转运体外模型，在特定条件下研究的OK细胞，柠檬酸盐和二羧酸酯的摄取对细胞外钙敏感。这些研究表明，OK细胞柠檬酸盐转运系统可能是一种新型的柠檬酸盐转运蛋白。 最近，开发了另一条二羧酸酯转运的细胞系。 通过人NADC1（CUBS细胞）稳定转染的人视网膜色素上皮细胞在体外对酸碱条件有反应，因此将代表一个强大的新模型。将检查两个假设：1。钙急性抑制哺乳动物近端小管细胞中的新型柠檬酸盐转运过程。 2。通过冗余机制，包括NADC1蛋白产生的变化以及将现有的NADC1蛋白从亚皮囊泡插入顶端膜中的冗余机制来实现柠檬酸近端转运的慢性调节。 具体目的是：1。通过：证明钙敏感的柠檬酸钙转运过程是一种新型的转运蛋白，而不是NADC1，并确定细胞外钙改变了这种柠檬酸盐运输过程。 2。描述通过酸碱扰动和低钾血症对柠檬酸盐转运的慢性调节机制。 为了实现这一目标，将检查三种调节模式：转录（或mRNA稳定性）调节，蛋白质水平的调节以及通过在代谢性酸中毒和低成效性的条件下从亚光子囊泡中运输NADC1进入和流出根尖膜的调节。