MECHANISM OF RENAL NA/DICARBOXYLATE TRANSPORT

当前提议的重点是在分子水平上表征 表达肾脏近端小管Na+/二羧酸共转运体。 这些转运蛋白对肾脏的功能非常重要。 Krebs循环中间体的重吸收，并在酸碱中发挥作用 平衡和有机阴离子排泄。刷子边界的Na+/二羧酸盐 辅转运蛋白与肾结石的发生有关，其机制包括 它对尿液柠檬酸浓度的调节。校长 研究人员最近克隆了一只兔子的肾脏并对其进行了测序 Na+/二羧酸共转运体，NADC-1和人类同源物，hNaDC-1。 NADC-1似乎对应于低亲和力的Na+/二羧酸盐 刷子边缘膜的共转运体。的第一个具体目标 这项研究是为了表征运输特性和组织 NADC-1和hNaDC-1的分布。第二个具体目标将涉及 认为转运蛋白功能的急性调节发生在 蛋白质水平，可能是通过磷酸化。第三个具体目标是 发现的高亲和力Na+/二羧酸共转运蛋白的克隆和测序 在肾近端小管基侧膜上。第四个具体问题 AIM将检验NADC-1的二级结构具有 八个跨膜区。第五个具体目标将考验 假设组氨酸参与NADC-1与底物的结合， NADC-1和相关转运体之间的嵌合体可以提供 有关对底物识别和结合重要的结构域的信息。 这些研究应该提供有关功能的基本信息 这个钠依赖转运蛋白家族的性质，以及关于 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.