Figure 6.

Loss of a critical Gly residue in the cytosolic portion of mENaC results in the PHA-1 phenotype. (A) Families of macroscopic Na⁺ currents from representative voltage-clamped CHO cells expressing mENaC containing αG95 substituted with Ala (top) or Cys (bottom). Currents were 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 (gray lines) mENaC containing αG95A (top) or αG95C (bottom). The I/V relations were generated from experiments similar to that shown in Fig. 5A. For presentation, the current was normalized to current at −100 mV. (C) Summary graph of (amiloride-sensitive) current density at steady state at −80 mV for voltage-clamped CHO cells (as in Fig. 5A) expressing wild-type mENaC and mENaC containing αG95S, αG95A, αG95C, or αG95W. 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 mENaC containing αG95S (open squares), αG95A (gray circles), or αG95C (black squares). Data are from experiments identical to that in panel A. For B and D, n ≥ 6 for each group.