Figure 4.

Removal of ENaC furin cleavage sites increases DCA activation of the channel. A, oocytes were injected with cRNA encoding WT ENaC subunits or ENaC subunits lacking the furin cleavage sites in the α and γ subunits (ENaCΔF: αR205A,R231AβγR143A). Whole-cell currents were measured by TEVC at −100 mV. Representative current traces of oocytes perfused with 1 mm DCA for 40 s, followed by 10 μm amiloride (amil) are shown. B, amiloride-sensitive currents are shown before and after exposure to DCA for each oocyte. Baseline amiloride-sensitive currents were −4.6 ± 1.21 μA for WT ENaC (n = 11) and −0.6 ± 0.3 μA for ENaCΔF (n = 19). ***, p < 0.001; ****, p < 0.0001 by Wilcoxon matched-pairs signed rank test. C, DCA activation of ENaC current was determined as a percentage of the amiloride-sensitive baseline current. Individual experiments are shown with bars indicating the mean. ****, p < 0.0001 by Mann–Whitney U test.