MECHANISM OF RENAL NA/DICARBOXYLATE TRANSPORT

当前提案的重点是在分子水平上表征 使肾近曲小管的Na+/二羧酸协同转运蛋白水平升高。 这些转运蛋白对于肾脏的功能很重要， 重吸收克雷布斯循环中间产物，并在酸碱平衡中发挥作用 平衡和有机阴离子排泄。 刷状缘Na+/二羧酸盐 协同转运蛋白与肾结石的发生有关， 调节尿柠檬酸盐浓度。 校长 研究人员最近克隆并测序了一只兔子的肾 Na+/二羧酸协同转运蛋白NaDC-1和人类同源物hNaDC-1。 NaDC-1似乎对应于低亲和力的Na+/二羧酸 刷状缘膜的协同转运蛋白。 第一个具体目标 本研究是为了表征传输特性和组织 NaDC-1和hNaDC-1的分布。 第二个具体目标是解决 转运蛋白功能的急性调节发生在 蛋白质水平，可能通过磷酸化。 第三个具体目标是 克隆和测序发现的高亲和力Na+/二羧酸协同转运蛋白 在肾近曲小管基底外侧膜上 第四特定 目的是检验NaDC-1的二级结构具有 八个跨膜结构域。 第五个具体目标将测试 假设组氨酸参与NaDC-1的底物结合， NaDC-1和相关转运蛋白之间的嵌合体可以提供 对底物识别和结合重要的结构域信息。 这些研究应提供有关功能的基本信息 这一家族的钠依赖性转运蛋白的性质，并对 这些转运蛋白在肾脏中的生理作用。

The focus of the current proposal is to characterize at the molecular level the Na+/dicarboxylate cotransporters of the renal proximal tubule. These transporters are important to the function of the kidney in their reabsorption of Krebs cycle intermediates, and play a role in acid-base balance and organic anion excretion. The brush border Na+/dicarboxylate cotransporter has been implicated in the development of kidney stones by its regulation of urinary citrate concentrations. The principal investigator has recently cloned and sequenced a rabbit renal Na+/dicarboxylate cotransporter, NaDC-1 and the human homolog, hNaDC-1. NaDC-1 appears to correspond to the low affinity Na+/dicarboxylate cotransporter of the brush border membrane. The first specific aim of this study is to characterize the transport properties and tissue distribution of NaDC-1 and hNaDC-1. The second specific aim will address the hypothesis that acute regulation of transporter function occurs at the protein level, possibly by phosphorylation. The third specific aim is to clone and sequence the high affinity Na+/dicarboxylate cotransporter found on the renal proximal tubule basolateral membrane. The fourth specific aim will test the hypothesis that the secondary structure of NaDC-1 has eight transmembrane domains. The fifth specific aim will test the hypothesis that histidines are involved in substrate binding by NaDC-1, and that chimeras between NaDC-1 and related transporters can provide information on domains important to substrate recognition and binding. These studies should provide fundamental information on the functional properties of this family of sodium-dependent transporters, and on the physiological role of these transporters in the kidney.