(verbatim from application) This 5-year grant application. IRPG#1, is the first of three Component Grants comprising the overall IRPG (Interactive Research Project Grant) application. This application also contains the single CORE of resources .hat will be shared among the Component Grants. The major goals of IRPG#1 are 1) to define the functional-structural domains on the ROMK K+ channel that are involved in channel regulation (phosphorylation sites, nucleotide-binding domain and pore-forming domain), and 2) to determine using a ROMK knockout mouse model the functional roles of the ROMK channel in renal K+ handling. The hypothesis driving the first goal is that amino- and carboxy-terminal regions of the ROMK channel protein provide domains for regulation of channel activitv by both phosphorylation and nucleotide-binding interactions. We propose to examine nucleotide binding and phosphorylation at the protein level. This is now possible based on our recently established ability to produce and purify to homogeneity milligram amounts of ROMK protein. The first goal will provide crucial information necessary for our collaboration to obtain three-dimensional structural information on this K+ channel. The major hypothesis driving the second goal is that the ROMK channel is essential to K+ secretory processes in the thick ascending limb (TAL) and in principal cells of the cortical collecting duct (CCD). This hypothesis will be tested by using mice deficient for the ROMK gene, i.e., a ROMK """"""""knockout"""""""" mouse model. The key observation driving our choice of the ROMK """"""""knockout"""""""" is the demonstration that loss-of-function mutations of human ROMK produce neonatal Bartter's Syndrome, a renal NaCI wasting condition due to reduced NaC1 transport by the TAL. While the human ROMK """"""""knockout"""""""" demonstrates the importance of this K+ channel to TAL function, many unanswered questions remain concerning the pathophysiology of this disorder (e.g., mechanism for continued renal K+ loss and role of prostaglandin E2 in renal NaC1 and K+ wasting) and may best be addressed using an animal model.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Special Emphasis Panel (ZRG1-GRM (02))
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Ketchum, Christian J
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Yale University
Schools of Medicine
New Haven
United States
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Dong, Ke; Yan, Qingshang; Lu, Ming et al. (2016) Romk1 Knockout Mice Do Not Produce Bartter Phenotype but Exhibit Impaired K Excretion. J Biol Chem 291:5259-69
Vucic, Esad; Alfadda, Tariq; MacGregor, Gordon G et al. (2015) Kir1.1 (ROMK) and Kv7.1 (KCNQ1/KvLQT1) are essential for normal gastric acid secretion: importance of functional Kir1.1. Pflugers Arch 467:1457-1468
Wade, James B; Fang, Liang; Coleman, Richard A et al. (2011) Differential regulation of ROMK (Kir1.1) in distal nephron segments by dietary potassium. Am J Physiol Renal Physiol 300:F1385-93
Geibel, John P; Hebert, Steven C (2009) The functions and roles of the extracellular Ca2+-sensing receptor along the gastrointestinal tract. Annu Rev Physiol 71:205-17
Yan, Qingshang; Yang, Xinbo; Cantone, Alessandra et al. (2008) Female ROMK null mice manifest more severe Bartter II phenotype on renal function and higher PGE2 production. Am J Physiol Regul Integr Comp Physiol 295:R997-R1004
Cantone, Alessandra; Yang, Xinbo; Yan, Qingshang et al. (2008) Mouse model of type II Bartter's syndrome. I. Upregulation of thiazide-sensitive Na-Cl cotransport activity. Am J Physiol Renal Physiol 294:F1366-72
Wagner, Carsten A; Loffing-Cueni, Dominique; Yan, Qingshang et al. (2008) Mouse model of type II Bartter's syndrome. II. Altered expression of renal sodium- and water-transporting proteins. Am J Physiol Renal Physiol 294:F1373-80
Bailey, M A; Cantone, A; Yan, Q et al. (2006) Maxi-K channels contribute to urinary potassium excretion in the ROMK-deficient mouse model of Type II Bartter's syndrome and in adaptation to a high-K diet. Kidney Int 70:51-9
Leng, Qiang; Kahle, Kristopher T; Rinehart, Jesse et al. (2006) WNK3, a kinase related to genes mutated in hereditary hypertension with hyperkalaemia, regulates the K+ channel ROMK1 (Kir1.1). J Physiol 571:275-86
Lu, Ming; Leng, Qiang; Egan, Marie E et al. (2006) CFTR is required for PKA-regulated ATP sensitivity of Kir1.1 potassium channels in mouse kidney. J Clin Invest 116:797-807

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