Transport Mechanism and Renal Function of a Newly Recognized Na+/H+ Exchanger

项目摘要 高血压是一个主要的健康问题，在美国，超过四分之一的成年人受到影响， 心脏和肾衰竭的独立危险因素。大约95%的病例是特发性的， 原发性高血压增加的Na+-Li+反向转运（SLC）是一种充分表征的遗传性状， 已知原发性高血压和糖尿病肾病标志物。SLC代表了一种替代模式， Na+/H+交换，并与肾小管中的钠转运相关。最近，我们的实验室发现， NHA 2是一种新型的钠质子（Na+/H+）逆向转运蛋白，介导SLC，并表达于NSCLC的远端肾单位。 肾脏NHA 2是NHA超家族的遗传学上不同且未表征的分支的成员。 后生动物阳离子质子转运蛋白，包括众所周知的NHE转运蛋白家族。在目标1中，我们 基于与已知NHA 2的细菌和古细菌直向同源物的相似性生成并测试NHA 2的模型结构， 结构中的外向和内向构象。结构模型的预测能力， 结合酵母中转运表型的功能筛选，将针对以下数据库进行测试： 以创新的PheWAS方法将基因型与人类变异和患者电子病历联系起来 疾病表型我们的初步观察表明NHA 2参与了肾囊肿的形成， 在肾源性尿崩症中的潜在作用，这是双极患者处方锂的主要并发症 和其他神经系统疾病。因此，在目标2中，我们将使用肾上皮细胞模型和三维成像。 孢囊，以确定NHA 2在盐和pH稳态中的作用。现代西方饮食中钠含量很高， 已知与高血压有关。在初步实验中，我们观察到NHA 2 喂食高盐饮食的小鼠中的转录本和蛋白质。目标3中的实验将研究 肾脏中的NHA 2以及NHA 2在盐和pH稳态中的作用，通过外推到动物模型。我们 将直接测试NHA 2是否负责小鼠和人类红细胞中的SLC活性。这 该提案将提供关于新型人类Na+转运蛋白及其功能的第一个机制和功能见解。 与高血压和人类疾病的相关性。

Project Summary Hypertension is a major health problem affecting more than 1 in 4 adults in the United States and is an independent risk factor for heart and kidney failure. Approximately 95% of cases are idiopathic and classified as essential hypertension. Increased Na+-Li+ countertransport (SLC) is a well-characterized inheritable trait and known marker for essential hypertension and diabetic nephropathy. SLC represents an alternative mode of Na+/H+ exchange and correlates with sodium transport in the renal tubule. Recently, our laboratory identified NHA2, a novel sodium proton (Na+/H+) antiporter that mediates SLC, and is expressed in the distal nephron of the kidney. NHA2 is a member of a phylogenetically distinct and uncharacterized branch of the superfamily of metazoan cation proton transporters that includes the well-known NHE family of transporters. In Aim 1, we will generate and test model structures of NHA2 based on similarity with bacterial and archaeal orthologs of known structures in outward and inward facing conformations. The predictive power of the structural models, combined with functional screening of transport phenotypes in yeast, will be tested against a database of human variants and patient electronic medical records in an innovative PheWAS approach to link genotypes to disease phenotypes. Our preliminary observations implicate NHA2 in renal cyst formation and point to a potential role in nephrogenic diabetes insipidus, a major complication in patients prescribed lithium for bipolar and other neurological disorders. Therefore, in Aim 2 we will use renal epithelial cell models and 3-dimensional cysts to determine the role of NHA2 in salt and pH homeostasis. Modern Western diet is high in sodium and is known to be associated with hypertension. In preliminary experiments, we have observed elevation of NHA2 transcript and protein in mice fed a high salt diet. Experiments in Aim 3 will investigate the salt induction of NHA2 in the kidney and the role of NHA2 in salt and pH homeostasis by extrapolation to animal models. We will directly test whether NHA2 is responsible for SLC activity in red cells from mouse and human. This proposal will provide the first mechanistic and functional insights on a novel human Na+ transporter and its relevance to hypertension and human disease.