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 alpha, beta, and gamma subunits, the role of respiratory delta-ENaC has not been studied in vivo due to the lack of animal models. Methods: We characterized full-length human delta(802)-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 delta(802)-ENaC channel activity. Immunoblotting was utilized to analyse delta(802)-ENaC protein. Transcripts of individual ENaC subunits in human lung tissues were quantitated with qPCR. Results: The results indicate that delta(802)-ENaC functions as an amiloride-inhibitable Na+ channel. Inhibitory peptide alpha-13 distinguishes delta(802)- from alpha-type ENaC channels. Modified proteolysis of gamma-ENaC by plasmin and aprotinin did not alter the inhibition of amiloride and alpha-13 peptide. Expression of delta(802)-ENaC at the apical membrane of respiratory epithelium was detected with biophysical features similar to those of heterologously expressed channels in oocytes. delta(802)-ENaC regulated alveologenesis through facilitating the proliferation of alveolar type 2 epithelial cells. Conclusion: The humanized mouse line conditionally expressing human delta(802)-ENaC is a novel model for studying the expression and function of this protein in vivo.