LAUSR

Sodium-chloride cotransporter (NCC), uniquely located at the distal convoluted tubule (DCT), is the target of thiazide diuretics and critically involved in renal handling of both Na + and K + . However, the mechanism of how NCC activity is regulated is incompletely understood. Here we report a novel role of (pro)renin receptor (PRR) and its cleavage product soluble PRR (sPRR) via site-1 protease (S1P) as negative regulators of NCC during high-salt or high-K + loading. Mice with DCT-specific deletion of PRR (termed as DCT PRR KO) was generated by crossing PRR floxed mice with a transgenic mouse line expressing Cre under the control of the parvalbumin (PV) promoter. Radiotelemrty demonstrated that under basic condition, DCT PRR KO mice exhibited modest hypertension (~5 mmHg) associated with reduced urinary Na + (Floxed: 0.20±0.02, KO: 0.12±0.01 mmol/24h, p<0.001), K + (Floxed: 0.29±0.02, KO: 0.18±0.03 mmol/24h, p<0.05), and Cl - (Floxed: 0.30±0.03, KO: 0.21±0.02 mmol/24h, p<0.01) excretion and increased in vivo NCC activity as assessed by hydrochlorothiazide (HCTN)-induced natriuresis ( by 61%). Renal protein abundance of pNCC-T53 (by 51%) but not total NCC was elevated in the null mice. Following a high salt diet, DCT PRR KO mice were salt sensitive as evidenced by a ~30 mm Hg increase of mean arterial pressure (MAP) which was sensitive to HCTN (ΔMAP, Floxed+HS: -2.05±1.50, KO+HS: -12.77±2.6 mmHg, p<0.05), contrasting to salt resistance in the floxed control. The null mice also exhibited impaired kaliuresis (Floxed+HK: 3.24±0.13, KO+HK: 2.32±0.23 mmol/24h, p<0.001) and hyperkalemia (Floxed+HK: 3.75±0.05, KO+HK: 4.40±0.08 mM, p<0.001) after high K + intake. This phenotype was recapitulated by treatment of C57/BL6 mice with S1P inhibitor PF429242. In cultured Flp-In T-REx 293 NCC cells, S1P-derived sPRR directly dephosphorylated NCC (by 40%) via activation of angiotensin II receptor type 1 (AT1R) independently of aldosterone. 1 / 2 Taken together, the present study has demonstrated that S1P-derived sPRR via AT1R negatively regulates NCC activity in the DCT to render salt resistance and to promote K + excretion. 2 / 2