Deletion of renal Nedd4-2 abolishes the effect of high sodium intake (HS) on Kir4.1, ENaC, and NCC and causes hypokalemia during high HS

• Published in: American journal of physiology. Renal physiology Vol. 320; no. 5; pp. F883 - F896
• Main Authors: Zhang, Dan-Dan, Duan, Xin-Peng, Xiao, Yu, Wu, Peng, Gao, Zhong-Xiuzi, Wang, Wen-Hui, Lin, Dao-Hong
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.05.2021
• Series: Mechanisms of Renal Electrolyte Transport and Ion Channel Regulation in Honor of Dr. Gerhard Giebisch
• Subjects: Aldosterone; Animals; Anti-Bacterial Agents - pharmacology; Biological Transport; Calcium conductance; Collecting duct; Diet; Doxycycline - pharmacology; Epithelial Sodium Channels - genetics; Epithelial Sodium Channels - metabolism; Excretion; Experiments; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Hydrochlorothiazide; Hypokalemia; Hypokalemia - chemically induced; Hypokalemia - etiology; Hypokalemia - genetics; Ion Transport - physiology; Kidneys; Mice; Mice, Knockout; Nedd4 Ubiquitin Protein Ligases - genetics; Nedd4 Ubiquitin Protein Ligases - metabolism; Nephrons - metabolism; Nutrient deficiency; Patch-Clamp Techniques; Potassium - metabolism; Potassium channels (inwardly-rectifying); Potassium Channels, Inwardly Rectifying - genetics; Potassium Channels, Inwardly Rectifying - metabolism; Potassium conductance; Renal function; Sodium; Sodium - metabolism; Sodium chloride; Sodium, Dietary - administration & dosage; Sodium, Dietary - adverse effects; Solute Carrier Family 12, Member 3 - genetics; Solute Carrier Family 12, Member 3 - metabolism; distal convoluted tubule; Kir4.1/Kir5.1; collecting duct; renal K+ excretion
• ISSN: 1931-857X; 1522-1466; 1522-1466
• DOI: 10.1152/ajprenal.00555.2020

The present study suggests that Nedd4-2 is involved in mediating the inhibitory effect of high salt (HS) diet on Kir4.1/kir5.1 in the distal convoluted tubule, NaCl cotransporter function, and epithelial Na + channel activity and that Nedd4-2 plays an essential role in maintaining K + homeostasis in response to a long-term HS diet. This suggests the possibility that HS intake could lead to hypokalemia in subjects lacking proper Nedd4-2 E3 ubiquitin ligase activity in aldosterone-sensitive distal nephron. Neural precursor cell expressed developmentally downregulated protein 4-2 (Nedd4-2) regulates the expression of Kir4.1, thiazide-sensitive NaCl cotransporter (NCC), and epithelial Na + channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN), and Nedd4-2 deletion causes salt-sensitive hypertension. We now examined whether Nedd4-2 deletion compromises the effect of high-salt (HS) diet on Kir4.1, NCC, ENaC, and renal K + excretion. Immunoblot analysis showed that HS diet decreased the expression of Kir4.1, Ca 2+ -activated large-conductance K + channel subunit-α (BKα), ENaCβ, ENaCγ, total NCC, and phospho-NCC (at Thr 53 ) in floxed neural precursor cell expressed developmentally downregulated gene 4-like ( Nedd4l fl/fl ) mice, whereas these effects were absent in kidney-specific Nedd4-2 knockout (Ks-Nedd4-2 KO) mice. Renal clearance experiments also demonstrated that Nedd4-2 deletion abolished the inhibitory effect of HS diet on hydrochlorothiazide-induced natriuresis. Patch-clamp experiments showed that neither HS diet nor low-salt diet had an effect on Kir4.1/Kir5.1 currents of the distal convoluted tubule in Nedd4-2-deficient mice, whereas we confirmed that HS diet inhibited and low-salt diet increased Kir4.1/Kir5.1 activity in Nedd4l flox/flox mice. Nedd4-2 deletion increased ENaC currents in the ASDN, and this increase was more robust in the cortical collecting duct than in the distal convoluted tubule. Also, HS-induced inhibition of ENaC currents in the ASDN was absent in Nedd4-2-deficient mice. Renal clearance experiments showed that HS intake for 2 wk increased the basal level of renal K + excretion and caused hypokalemia in Ks-Nedd4-2-KO mice but not in Nedd4l flox/flox mice. In contrast, plasma Na + concentrations were similar in Nedd4l flox/flox and Ks-Nedd4-2 KO mice on HS diet. We conclude that Nedd4-2 plays an important role in mediating the inhibitory effect of HS diet on Kir4.1, ENaC, and NCC and is essential for maintaining normal renal K + excretion and plasma K + ranges during long-term HS diet. NEW & NOTEWORTHY The present study suggests that Nedd4-2 is involved in mediating the inhibitory effect of high salt (HS) diet on Kir4.1/kir5.1 in the distal convoluted tubule, NaCl cotransporter function, and epithelial Na + channel activity and that Nedd4-2 plays an essential role in maintaining K + homeostasis in response to a long-term HS diet. This suggests the possibility that HS intake could lead to hypokalemia in subjects lacking proper Nedd4-2 E3 ubiquitin ligase activity in aldosterone-sensitive distal nephron.