Transepithelial Na current in FRT epithelia coexpressing ENaC and KS-WNK1. FRT epithelia were transfected with ENaC (WT or αY644A, βY620A, γY627A, 0.07 μg of each subunit) and KS-WNK1 (0–0.8 μg, total cDNA held constant with GFP cDNA). (A) Representative short-circuit current tracings for ENaC coexpressed with GFP (“–KS-WNK1”) or KS-WNK1 (0.8 μg). Amiloride (100 μM) was added to apical bathing solution as indicated by bar. (B) Plots of amiloride-sensitive short-circuit current (relative to 0 μg KS-WNK1 for each group) vs. quantity of KS-WNK1 cDNA for WT ENaC and αY644A, βY620A, γY627A (“Y-A”) (mean ± SEM, n = 11–19; asterisks indicate P < 0.02 vs. 0 μg of KS-WNK1).