Figure 4.

PHA-1 mutation results in a consistent ENaC phenotype across species and channel subunits. (A) Families of macroscopic Na⁺ currents from representative CHO cells expressing mENaC harboring PHA-1-causing mutations in the α (top; G95S), β (middle; G37S), and γ (bottom; G40S) subunits. Current was evoked by progressive 20 mV voltage steps from a holding potential of 0 mV up to 100 mV and down to −200 mV. For these experiments, the bath and pipette [Na⁺] were symmetrical at 150 mM. (B) Macroscopic I/V relations for CHO cells expressing wild-type (black lines) and mutant mENaC (gray lines) containing αG95S (top), βG37S (middle), or γG40S (bottom). The I/V relations were generated from experiments similar to that in panel A. For presentation, current was normalized to current at −100 mV. (C) Summary graph of (amiloride-sensitive) current density at steady state at −80 mV for CHO cells, similar to that in panel A, expressing wild-type mENaC and mENaC harboring PHA-1-causing mutations in the α-, β-, or γ-subunit. The number of experiments for each group is indicated. ^∗ Significant (P < 0.05) decrease versus wild-type mENaC. (D) Steady-state G-V relations were fitted with the Boltzmann equation for CHO cells expressing wild-type (open boxes) and mENaC containing αG95S (black squares) and γG40S (open circles). Data were obtained from experiments identical to that in panel A. For presentation, conductance was normalized to the maximum of the fit. For B and D, n ≥ 6 for each group.