Figure 10.

The arginine residue R153 at the proximal end of γ-11 may serve as another TMPRSS2-cleavage site mediating partial ENaC activation.A, representative whole-cell current traces recorded in individual oocytes from the same batch injected with 1 ng/subunit/oocyte of cRNA for wildtype (αβγ) or mutant ENaC (αβγ_RKRR138AAAA or αβγ_{RKRR138AAAA + R153A}) either alone (−) or in combination with 5 ng/oocyte cRNA for TMPRSS2 (+). Amiloride (ami, 2 μM) was present in the bath solution as indicated by black bars. Dashed lines indicate zero current level. Summary data obtained in similar experiments are shown to the right of the representative traces. Mean ± SD and data points for individual oocytes are shown; ∗∗∗p < 0.001; ns, two-tailed Mann–Whitney test (18 ≤ n ≤ 25, N = 3). B, ΔI_ami values of individual oocytes obtained in the same experiments as shown in (A) were normalized as described for Figure 8B. Dashed line indicates a normalized ΔI_ami value of one (no effect). Mean ± SD and data points for individual oocytes are shown; ∗∗∗p < 0.001; ∗p < 0.05; Kruskal–Wallis with Dunn’s post hoc test. C, summary of ΔI_ami values obtained in oocytes injected with 1 ng/subunit/oocyte of cRNA for wildtype (αβγ) or mutant ENaC (αβγ_{RKRK178AAAA;K168A;K170A;R172A;K189A + R153A}) either alone (−) or in combination with 5 ng/oocyte cRNA for TMPRSS2 (+). Mean ± SD and data points for individual oocytes are shown; ∗∗p < 0.01; ns, Kruskal–Wallis with Dunn’s post hoc test. cRNA, complementary RNA; ENaC, epithelial sodium channel; TMPRSS2, transmembrane serine protease 2.