The Role of Intercalated Cell Nedd4-2 in BP Regulation, Ion Transport, and Transporter Expression.

Background Nedd4-2 is an E3 ubiquitin-protein ligase that associates with transport proteins, causing their ubiquitylation, and then internalization and degradation. Previous research has suggested a correlation between Nedd4-2 and BP. In this study, we explored the effect of intercalated cell (IC) Nedd4-2 gene ablation on IC transporter abundance and function and on BP. Methods We generated IC Nedd4-2 knockout mice using Cre-lox technology and produced global pendrin/ Nedd4-2 null mice by breeding global Nedd4-2 null ( Nedd4-2 ^-/- ) mice with global pendrin null ( Slc26a4 ^-/- ) mice. Mice ate a diet with 1%-4% NaCl; BP was measured by tail cuff and radiotelemetry. We measured transepithelial transport of Cl ^- and total CO ₂ and transepithelial voltage in cortical collecting ducts perfused in vitro Transporter abundance was detected with immunoblots, immunohistochemistry, and immunogold cytochemistry. Results IC Nedd4-2 gene ablation markedly increased electroneutral Cl ^- /HCO ₃ ^- exchange in the cortical collecting duct, although benzamil-, thiazide-, and bafilomycin-sensitive ion flux changed very little. IC Nedd4-2 gene ablation did not increase the abundance of type B IC transporters, such as AE4 ( Slc4a9 ), H ⁺ -ATPase, barttin, or the Na ⁺ -dependent Cl ^- /HCO ₃ ^- exchanger ( Slc4a8 ). However, IC Nedd4-2 gene ablation increased CIC-5 total protein abundance, apical plasma membrane pendrin abundance, and the ratio of pendrin expression on the apical membrane to the cytoplasm. IC Nedd4-2 gene ablation increased BP by approximately 10 mm Hg. Moreover, pendrin gene ablation eliminated the increase in BP observed in global Nedd4-2 knockout mice. Conclusions IC Nedd4-2 regulates Cl ^- /HCO ₃ ^- exchange in ICs., Nedd4-2 gene ablation increases BP in part through its action in these cells.
(Copyright © 2018 by the American Society of Nephrology.)