The Biology of NBCe1 in Health and Disease

项目摘要 肾脏中的SLC 4蛋白在介导偶联转运（共转运体， 近端小管和集合管中Na+、HCO 3+、CO 32+和Cl+的交换器）。婴儿和儿童 随着产电Na+-CO 32 β同向转运体NBCe 1和Cl β/HCO 3 β交换体AE 1的突变， 严重的近端和远端肾小管酸中毒。致病突变如何损害他们的 分子水平上的运输机制是未知的。为了实现这一目标，我们最近解决了 冷冻电子显微镜（cryoEM）：NBCe 1的外向结构，NBCe 1的内向和外向结构。 AE 1的结构，并获得了Na+-CO_32 ~+/Cl ~-交换剂NDCBE的二维类平均值 代表了该领域的重大进展。这些重大进展加上我们初步的功能性 诱变和分子动力学计算分析使其有可能在第一次 运输领域，以实现了解详细的结构功能的长期目标 SLC 4转运蛋白的性质及其因致病突变而受到的损害。为了实现这一 目标1：AE 1的结构决定因素， NBCe 1和NDCBE离子配位位点、传输模式和离子特异性： cryoEM、功能诱变和分子动力学计算分析， 这些转运蛋白中的离子配位位点编码它们各自的转运模式和独特的离子配位位点。 将审查运输的具体情况。目的2：表征AE 1、NBCe 1和 NDCBE渗透孔、离子选择性和能量学：为此，使用cryoEM、功能诱变 和分子动力学计算分析，假设在结构和 离子在这些转运体之间的渗透能在决定选择性方面起着重要作用 将检查离子到达它们的配位位点的外向和内向构象。 目标3：AE 1、NBCe 1和NDCBE的传输模型以及传输异常的表征 肾小管酸中毒诱发突变：AE 1、NBCe 1和 将根据初步数据和目标1和目标2中获得的结果生成NDCBE。如何疾病 将确定导致突变损害这些机械转运蛋白分子模型的因素。这项建议 鉴于SLC 4转运蛋白的重要性，代表了对肾脏病学和医学的重大贡献 在调节肾离子平衡、全身酸碱化学、血压和维持细胞 功能和成长。

PROJECT SUMMARY SLC4 proteins in the kidney play an essential role in mediating the coupled transport (symporters, exchangers) of Na+, HCO3⎯, CO32⎯, and Cl⎯ in the proximal tubule and collecting duct. Infants and children with mutations in the electrogenic Na+-CO32⎯ symporter NBCe1 and the Cl⎯/HCO3⎯ exchanger AE1 develop severe proximal and distal renal tubular acidosis respectively. How disease causing mutations impair their transport mechanisms at the molecular level is unknown. Towards this goal, we have recently solved by cryoelectron microscopy (cryoEM) the outward facing structure of NBCe1, the inward and outward facing structures of AE1, and have obtained 2D class averages of the Na+-CO32⎯/Cl⎯ exchanger NDCBE representing major advances in the field. These significant advances coupled with our preliminary functional mutagenesis and Molecular Dynamics computational analyses make it possible for the first time in the transport field to achieve the long-term objective of understanding the detailed structure-functional properties of SLC4 transporters and their impairment by disease causing mutations. To accomplish this objective, the project addresses the following specific aims: Aim 1: Structural Determinants of the AE1, NBCe1, and NDCBE Ion Coordination Sites, Transport Modes and Ion Specificities: In this aim, using cryoEM, functional mutagenesis and Molecular Dynamics computational analyses, the hypothesis that the ion coordination sites in these transporters encode both their respective transport modes and unique ion transport specificities will be examined. Aim 2: Characterize the Structural Components of AE1, NBCe1 and NDCBE Permeation Pores, Ion Selectivity and Energetics: In this aim, using cryoEM, functional mutagenesis and Molecular Dynamics computational analyses, the hypothesis that differences in the structure and energetics of ion permeation among these transporters plays an important role in determining the selectivity of ions reaching their coordination sites in both outward and inward facing conformations will be examined. Aim 3: Transport Models for AE1, NBCe1 and NDCBE, and Characterization of the Transport Abnormalities Induced by Renal Tubular Acidosis Causing Mutations: The dynamic transport models of AE1, NBCe1 and NDCBE will be generated based on preliminary data, and the results obtained in Aims 1 and 2. How disease causing mutations impair these mechanistic transporter molecular models will be determined. This proposal represents a significant contribution to Nephrology and Medicine given the importance of SLC4 transporters in regulating kidney ion balance, systemic acid-base chemistry, blood pressure, and the maintenance of cell function and growth.