Molecular Mechanism of ROMK Channel Function

肾脏中的ROMK(KIR 1.1，KCNJ1基因产物)通道有 微调调节肾钾排泄，维持钾 平衡。依赖于细胞骨架蛋白的内吞作用起着关键作用，限制了尿钾 缺钾所致的损失。在肾脏疾病中，异常的ROMK内吞可能 导致钾滞留和危及生命的高钾血症。现有证据 表明ROMK内吞作用是由WNKS刺激的，WNKS是一种突变在 家族性高钾血症和高血压(FHHt)。此应用程序构建在我们最新的 发现：1)低钾直接刺激远端ROMK内吞 2)WNK通过磷酸化网状蛋白适配器刺激ROMK的内吞作用， ARH，3)NEDD4家族相互作用蛋白，NDFIP1和2，与ROMK相互作用 控制通道的内吞后处理。以实现这些突破 对钾平衡如何实现全新理解的观察 为了实现这一点，我们概述了计划：1)定义钾直接 调节ROMK内吞作用；2)探索这一途径在小鼠中的参与 FHHt模型，3)阐明NDFIP1和NDFIP2的分子机制 控制ROMK的内吞后路由至溶酶体。这些研究应该提供 肾脏钾处理和钾稳态在健康中的分子基础的新见解 同时阐明了膜蛋白靶向的基本机制 在肾脏里。

ROMK (Kir 1.1, product of the KCNJ1 gene) channels in the kidney are exquisitely regulated to adjust renal potassium excretion and maintain potassium balance. Clathrin-dependent endocytosis plays a critical role, limiting urinary potassium loss in potassium deficiency. In renal disease, aberrant ROMK endocytosis may contribute to potassium retention and life-threatening hyperkalemia. Available evidence indicates ROMK endocytosis is stimulated by WNKs, kinases that are mutated in Familial Hyperkalemic and Hypertension (FHHt). This application builds on our recent discoveries that: 1) Low potassium directly stimulates ROMK endocytosis in the distal nephron, 2) WNK stimulates ROMK endocytosis by phosphorylating the clathrin-adaptor, ARH, 3) NEDD4 Family of Interacting Proteins, NDFIP1 and 2, interact with ROMK to control post-endocytic processing of the channel. To carry these breakthrough observations toward a completely new understanding of how potassium balance is achieved, we outline plans to: 1) Define the mechanism by which potassium directly regulates ROMK endocytosis; 2) Explore the involvement of this pathway in a mouse model of FHHt, 3) Elucidate the molecular mechanism by which NDFIP1 and NDFIP2 control post-endocytic routing of ROMK to the lysosome. The studies should provide novel insights into the molecular basis of renal K handling and K homeostasis in health and disease while illuminating fundamental mechanisms of membrane protein targeting in the kidney.