WNK Kinase Regulation of Thiazide-sensitive NaCl Transport

Oregon Health & Science University, Portland OR

Investigators

Linked publications, trials & patents

Abstract

Project Summary Salt transport by the kidney is dysregulated in many diseases, including heart failure and hypertension. This project is designed understand how sodium chloride reabsorption along the distal nephron in the kidney is regulated by diet and disease. The work will focus on the distal convoluted tubule and the thiazide-sensitive NaCl cotransporter, which play key roles in regulating arterial pressure, systemic potassium balance, and the development of resistance to diuretic drugs. The thiazide-sensitive NaCl cotransporter is activated by low NaCl intake or low potassium intake through WNK kinases, which eventually affect its phosphorylation status. Low potassium intake reduces intracellular chloride concentration, activating these kinases, but the kinases can also be activated when intracellular chloride concentration is high. When stimulated, WNK kinases form condensates, with other regulatory proteins. In the first aim, we will study two novel components of these WNK signaling condensates, which activate the kinases under diverse conditions. We will determine whether the condensates comprise localized regions of low chloride concentration, and also study how the novel proteins interact with a kidney-specific form of WNK1 that is known to be essential for their formation. In a second aim, we will test the hypothesis that signaling by G-protein-coupled receptors in this same nephron segment activates WNK kinases and contributes to human disease. We showed recently that raising luminal calcium activates the thiazide- sensitive NaCl transporter, through stimulation of the calcium-sensing receptor. We will therefore test whether increases in luminal calcium caused by loop diuretic actions upstream contribute to distal convoluted tubule cell growth and to diuretic resistance. We have shown that glucose or fructose can also activate the thiazide-sensitive NaCl cotransporter via the calcium-sensing receptor in the distal convoluted tubule luminal membrane; we believe that this effect may underlie some of the high blood pressure that results from diabetes or when individuals consume fructose-containing beverages. Here, we will confirm the involvement of the calcium sensing receptor, by deleting it genetically. We will also use novel approaches to mimic G protein-coupled receptor stimulations exclusively in the distal convoluted tubule. Preliminary data shows that activation of the receptors in the basolateral membrane rapidly reduces salt transport; here, we will test whether this effect is mediated through inhibition of potassium channels in the basolateral membrane. Finally, we will determine whether angiotensin II and low salt diet, long known to stimulate sodium chloride transporter activity, do so through another G-protein-coupled receptor, the angiotensin receptor. Together, these experiments will provide substantial insight into how the kidney handles salt in both health and disease.