Molecular Mechanism of ROMK Channel Function

肾脏中的ROMK（Kir 1.1，KCNJ 1基因的产物）通道是 精细调节肾脏排钾，维持钾 平衡网格蛋白依赖的内吞作用起着关键作用，限制尿钾 钾缺乏的损失。在肾脏疾病中，异常的ROMK内吞作用可能 导致钾潴留和危及生命的高钾血症。现有证据 表明ROMK内吞作用受到WNK的刺激，WNK是一种突变的激酶， 家族性高钾血症和高血压（FHHt）。这个应用程序建立在我们最近的 发现：1）低钾直接刺激远端ROMK内吞作用 肾单位，2）WNK通过磷酸化网格蛋白-衔接子刺激ROMK内吞作用， ARH，3）NEDD 4相互作用蛋白家族，NDFIP 1和2，与ROMK相互作用， 控制通道的内吞后加工。为了实现这些突破 对钾平衡的全新理解的观察 实现，我们概述计划：1）定义钾直接 调节ROMK内吞作用; 2）探索小鼠中该途径的参与 3）阐明NDFIP 1和NDFIP 2与FHHt相互作用的分子机制 控制ROMK到溶酶体的内吞后路由。研究应提供 对健康肾脏钾处理和钾稳态的分子基础的新见解 同时阐明膜蛋白靶向的基本机制 在肾脏。

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.