Proliferative regulation of alveolar epithelial type 2 progenitor cells by human Scnn1d gene

Lung epithelial sodium channel (ENaC) encoded by Scnn1 genes is essential for maintaining transepithelial salt and fluid homeostasis in the airway and the lung. Compared to α, β, and γ subunits, the role of respiratory δ-ENaC has not been studied in vivo due to the lack of animal models.

Methods: We characterized full-length human δ₈₀₂-ENaC expressed in both Xenopus oocytes and humanized transgenic mice. AT2 proliferation and differentiation in 3D organoids were analysed with FACS and a confocal microscope. Both two-electrode voltage clamp and Ussing chamber systems were applied to digitize δ₈₀₂-ENaC channel activity. Immunoblotting was utilized to analyse δ₈₀₂-ENaC protein. Transcripts of individual ENaC subunits in human lung tissues were quantitated with qPCR.

Results: The results indicate that δ₈₀₂-ENaC functions as an amiloride-inhibitable Na⁺ channel. Inhibitory peptide α-13 distinguishes δ₈₀₂- from α-type ENaC channels. Modified proteolysis of γ-ENaC by plasmin and aprotinin did not alter the inhibition of amiloride and α-13 peptide. Expression of δ₈₀₂-ENaC at the apical membrane of respiratory epithelium was detected with biophysical features similar to those of heterologously expressed channels in oocytes. δ₈₀₂-ENaC regulated alveologenesis through facilitating the proliferation of alveolar type 2 epithelial cells.

Conclusion: The humanized mouse line conditionally expressing human δ₈₀₂-ENaC is a novel model for studying the expression and function of this protein in vivo .