Structure and Function of ROMK Channel in Kidney

描述（由申请人提供）：ROMK（Kir1.1）在远端肾单位和集合管中形成顶端钾通道，为1）粗升支吸收NaCl所需的钾再循环和2）连接管和主细胞的钾分泌提供钾分泌途径。因此，确定ROMK通道的功能和调节对于理解肾脏钾处理和身体钾稳态是重要的。ROMK的功能丧失突变导致Bartter综合征，这是一种膨胀性肾性盐耗疾病，是由于粗的上升肢体丧失了盐重吸收能力。我们已经开发出了唯一一种具有足够高的存活率（>30%）以允许生理学研究的ROMK Bartter小鼠-并且是唯一一种具有如此高存活率的Bartter小鼠模型。我们建议继续研究小鼠ROMK Bartter的病理生理学，以提高我们对ROMK在肾K处理中的作用的理解，并提出治疗人类Bartter综合征的潜在方式。我们还将开发两种新的ROMK转基因小鼠，它们将为评估ROMK亚型的特定作用和ROMK亚型在天然肾细胞中的受调控运输提供模型。ROMK 1是其中一种亚型，仅在晚期远端小管和集合管中表达，并被认为在通过膳食钾摄入调节肾脏钾分泌中发挥重要作用。我们建议通过使用Cre-LoxP策略选择性删除ROMK 1特异性外显子来产生仅在ROMK 1中缺陷的小鼠。我们假设，这只小鼠不会有巴特的表型，而是有紊乱的K处理增加或减少饮食中的K摄入量。我们还将产生一个ROMK 1 BAC转基因小鼠标记的FLAG和EGFP，以确定ROMK运输在肾上皮细胞和确定相关的蛋白质在ROMK调控复合物。这些小鼠还将为对非肾细胞（胃肠道、脑等）中的ROMK功能感兴趣的其他人提供资源。

DESCRIPTION (provided by applicant): ROMK (Kir1.1) forms apical K channels in the distal nephron and collecting duct that provide the K secretory pathways for 1) K recycling necessary for NaCI absorption by the thick ascending limb and 2) K secretion by connecting duct and principal cells. Therefore, defining the function and regulation of the ROMK channels is important for understanding renal K handling and body K homeostasis. Loss-of-function mutations in ROMK cause Bartter's syndrome, a hypotensive renal salt wasting disease, that is due to loss of salt reabsorbing capacity by the thick ascending limb. We have developed the only ROMK Bartter's mouse with sufficiently high survival (>30%) to permit physiological study - and is the only mouse model of Bartter's with such high survival. We propose to continue to study the pathophysiology of mouse ROMK Bartter's to enhance our understanding of the role of ROMK in renal K handling and to suggest potential modalities for therapy of human Bartter's syndrome. We will also develop two new ROMK transgenic mice that will provide models for assessing both the specific roles of ROMK isoforms and the regulated trafficking of ROMK isoforms in native kidney cells. One of these isoforms, ROMK1, is only expressed in late distal tubule and collecting duct and has been suggested to play an important role in the regulation of renal K secretion by dietary K intake. We propose to generate a mouse deficient only in ROMK1 by selective deletion of the ROMK1-specific exon using a Cre-LoxP strategy. We hypothesize that this mouse will not have a Bartter's phenotype, but instead, have disordered K handling with increases or decreases in dietary K intake. We will also generate a ROMK1 BAC-transgenic mouse tagged with FLAG and EGFP to define ROMK trafficking in kidney epithelial cells and to determine associated proteins in the ROMK regulatory complex. These mice will also provide a resource for others interested in ROMK function in non- renal cells (Gl tract, brain, etc).