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

项目摘要 高血压是影响美国四分之一以上成年人的主要健康问题，是一种 心肾功能衰竭的独立危险因素。大约95%的病例是特发性的和分类的 作为原发性高血压。Na+-Li+反向转运(SLC)增加是一种具有良好特征的遗传特征和 已知的高血压和糖尿病肾病的标志物。SLC代表另一种模式 Na+/H+交换与肾小管钠转运相关。最近，我们实验室鉴定出 NHA2，一种新的钠质子(Na+/H+)逆向转运蛋白，介导SLC，并在SLC的远端肾单位表达 肾脏。NHA2是一个在系统发育上截然不同且没有特征的分支的成员 后生动物阳离子质子转运体，包括著名的NHE转运体家族。在目标1中，我们将 基于与已知细菌和古生菌同源物的相似性生成和测试NHA2的模型结构 向外和向内的构象的结构。结构模型的预测能力， 结合酵母运输表型的功能筛选，将在数据库中进行测试 人类变种和患者电子病历在一种创新的Phewas方法中将基因型别与 疾病表型。我们的初步观察表明NHA2与肾囊肿的形成有关，并指出 肾源性尿崩症的潜在作用，这是服用锂治疗双相情感障碍患者的主要并发症 以及其他神经系统疾病。因此，在目标2中，我们将使用肾上皮细胞模型和三维 以确定NHA2在盐分和pH动态平衡中的作用。现代西方饮食中钠含量高，而且 已知与高血压有关。在初步实验中，我们观察到NHA2的升高 高盐饮食小鼠的转录本和蛋白质。目标3中的实验将研究盐诱导 通过对动物模型的外推，研究了肾脏中的NHA2以及NHA2在盐和pH动态平衡中的作用。我们 将直接测试NHA2是否对小鼠和人类红细胞中的SLC活性负责。这 该提案将首次对一种新型的人类钠离子转运体及其功能提供机制和功能方面的见解 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.