RGS14 Regulation of Hormone-sensitive NPT2A-mediated Phosphate Transport

项目摘要：PTH和FGF23在汇聚的肾近端小管细胞中启动信号通路 在[NPT2A：NHERF1]复合体上抑制磷吸收。缺乏PDZ蛋白NHERF1和 携带NHERF1突变的人类是低磷血症。在理解以下方面存在重大差距 由于不明因素，这些行动中涉及的要素。对慢性阻塞性肺疾病患者进行的大量GWAS研究 肾脏疾病与RGS14有关，RGS14含有PDZ识别基序。我们认为RGS14是一部小说 激素敏感型磷酸盐转运的调节机制，并提供支持这一观点的初步数据。RGS14 是整合G蛋白、MAPK和钙/钙调素信号通路的支架。它的行动是最容易理解的 在啮齿动物大脑中，RGS14抑制突触可塑性和基于海马体的学习。什么都不知道 关于RGS14对激素作用或肾脏的影响。我们的初步发现表明，RGS14抑制了 PTH和FGF23均调节磷酸盐转运。RGS14持续减弱甲状旁腺素调节的磷酸盐 原代人近端小管细胞的转运。被siRNA击倒的RGS14逆转了这一行为，揭示了 甲状旁腺素的全部活性。RGS14加回缺乏该蛋白质的细胞可阻断甲状旁腺素的作用。人类RGS14含有一个C- 直接与NHERF1结合的末端PDZ配体(-DSAL)。PDZ配体突变破坏RGS14结合 并干扰RGS14对激素作用的调节。这些发现将RGS14确定为一种 一种全新的元素，调节荷尔蒙对重要的动态平衡活动的作用，并提出了以下假设 RGS14是一种新的激素敏感的[NPT2A：NHERF1]介导的肾脏近端磷酸盐转运调节因子 肾小管细胞。三个目标将检验这一前提。目标1将定义RGS14如何调节 [NPT2A：NHERF1]，其内化和激素敏感的磷酸盐吸收。目标2将定义 RGS14对PTH和FGF23信号的影响及激素诱导的NHERF1磷酸化对其的影响 RGS14对[NPT2A：NHERF1]复合体的调节。目标3：将定义PTH和FGF23定向的信号如何 影响RGS14与NHERF1和[NHERF1：NPT2A]复合体的相互作用。这些研究将确定小说 RGS14调节NPT2A功能和激素敏感磷酸酶的作用及分子机制 肾脏转运与肾脏疾病有关。

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.