Functional expression of the epithelial sodium channel delta subunit in human respiratory epithelial cells

Abstract

The expression and function of the epithelial sodium channel δ subunit (δ‐ENaC) as well as its contribution to ion and fluid transport in human respiratory epithelial cells.Expression of δ‐ENaC was investigated in human alveolar (A549) and bronchial (Calu‐3, 16HBE14o‐) epithelial cell lines on genomic and protein levels. Reverse transcriptase and real‐time PCR were carried out as well as analysis by Western blot and immuno‐confocal laser scanning microscopy (CLSM). Ussing chamber studies were performed with Calu‐3 monolayers using Evans blue at 10 – 50 μM.Delta‐ENaC expression was confirmed in all cell lines on mRNA level with higher abundance in A549 and 16HBE14o‐ than in Calu‐3 cell monolayers. Generally, mRNA levels of δ‐ENaC were weaker than that of α, β and γ ENaC subunits. By Western blot and CLSM δ‐ENaC protein was detected in all cell lines, with the highest expression found in Calu‐3 and 16HBE14o‐ cells. CLSM also revealed the δ‐ENaC subunit located in the apical aspect of cellular membranes. Evans blue exhibited a concentration‐dependant increase of ISC up to 650% at 50 μM.These results indicate that ä‐ENaC is functionally expressed in human respiratory epithelial cell monolayers. Further experiments will investigate its role in ion and fluid transport processes across the respiratory epithelial barrier.ES is funded by an IRSCET postgraduate scholarship.