RGS14 Regulation of Hormone-sensitive NPT2A-mediated Phosphate Transport

项目总结：PTH和FGF 23启动肾脏近端小管细胞中的信号通路， [NPT 2A：NHERF 1]复合物抑制磷酸盐摄取。缺乏PDZ蛋白NHERF 1的小鼠和 携带NHERF 1突变的人是低磷酸盐血症。在理解 由于不明原因，这些行动涉及的因素。许多GWAS研究的慢性 肾脏疾病涉及RGS 14，其具有PDZ识别基序。我们认为RGS 14是一个新的 调节剂的敏感磷酸盐运输，并提供初步的数据来支持这一想法。RGS14 是整合G蛋白、MAPK和Ca++/CaM信号通路的支架。它的行为最好理解 在啮齿动物的大脑中，RGS 14抑制突触可塑性和基于突触的学习。一无所知 关于RGS 14对激素作用或肾脏的影响。我们的初步发现表明RGS 14抑制了 PTH和FGF 23调节磷酸盐转运。RGS 14持续减弱PTH调节的磷酸盐 在原代人近曲小管细胞中的转运。通过siRNA敲低RGS 14逆转了这一作用， 全段PTH活性RGS 14添加回缺乏蛋白质的细胞阻断PTH作用。人RGS 14含有一个C- 末端PDZ配体（-DSAL），其直接结合NHERF 1。PDZ-配体中的突变破坏RGS 14结合 NHERF 1和干扰RGS 14调节激素的作用。这些发现将RGS 14确定为 一个全新的元素调节激素作用于一个重要的稳态活动，并提出假设， RGS 14是肾近端细胞中对NPT 2A：NHERF 1敏感的磷酸盐转运的新型调节剂 肾小管细胞三个目标将检验这一前提。AIM 1将定义RGS 14如何调节 [NPT 2A：NHERF 1]，其内化和对磷酸盐敏感的摄取。AIM 2将定义 RGS 14对PTH和FGF 23信号传导的影响以及蛋白酶介导的NHERF 1磷酸化对PTH和FGF 23信号传导的影响。 [NPT 2A：NHERF 1]复合物的RGS 14调节。目的3：将定义PTH和FGF 23介导的信号传导 影响RGS 14与NHERF 1和[NHERF 1：NPT 2A]复合物的相互作用。这些研究将确定新的 RGS 14调节NPT 2A功能和对蛋白质敏感的磷酸盐的作用和分子机制 与肾脏疾病有关的肾脏转运。

PROJECT SUMMARY: PTH and FGF23 initiate signaling pathways in renal proximal tubule cells that converge on the [NPT2A:NHERF1] complex to inhibit phosphate uptake. Mice lacking the PDZ protein NHERF1 and humans harboring NHERF1 mutations are hypophosphatemic. Important gaps exist in understanding the elements involved in these actions due to unidentified factors. Numerous GWAS studies of patients with chronic kidney disease implicate RGS14, which harbors a PDZ-recognition motif. We propose that RGS14 is a novel regulator of hormone-sensitive phosphate transport, and provide preliminary data to support this idea. RGS14 is scaffold that integrates G protein, MAPK, and Ca++/CaM signaling pathways. Its actions are best understood in rodent brain, where RGS14 suppresses synaptic plasticity and hippocampal-based learning. Nothing is known about RGS14 effects on hormone action or in kidney. Our preliminary findings show that RGS14 suppresses both PTH- and FGF23-regulated phosphate transport. RGS14 persistently attenuates PTH-regulated phosphate transport in primary human proximal tubule cells. RGS14 knock-down by siRNA reverses this action to reveal full PTH activity. RGS14 add-back to cells lacking the protein blocks PTH actions. Human RGS14 contains a C- terminal PDZ ligand (-DSAL) that directly binds NHERF1. Mutations in the PDZ-ligand disrupt RGS14 binding to NHERF1 and interfere with RGS14 regulation of hormone actions. These findings identify RGS14 as an entirely new element regulating hormone action on a vital homeostatic activity, and raise the hypothesis that RGS14 is a novel regulator of hormone-sensitive [NPT2A:NHERF1]-mediated phosphate transport in renal proximal tubule cells. Three Aims will test this premise. AIM 1 will define how RGS14 regulates assembly, disassembly of [NPT2A:NHERF1], its internalization and hormone-sensitive phosphate uptake. AIM 2 will define the locus of RGS14 effects on PTH and FGF23 signaling and the impact of hormone-directed NHERF1 phosphorylation on RGS14 regulation of the [NPT2A:NHERF1] complex. AIM 3: will define how PTH- and FGF23-directed signaling affect RGS14 interactions with NHERF1 and the [NHERF1:NPT2A] complex. These studies will identify novel roles and molecular mechanisms by which RGS14 regulates NPT2A function and hormone-sensitive phosphate transport in kidney as related to kidney disease.