Tmprss2 maintains epithelial barrier integrity and transepithelial sodium transport
Membrane-bound serine proteases are well known regulators of ENaC. More recently, they have also been identified as regulators of tight junction complexes. Here, we demonstrate that within the kidney, the serine protease Tmprss2 is co-expressed with the alpha subunit of ENaC, whereas Furin is primarily expressed in ENaC-negative cortex cells. In mCCDcl1 kidney cells, aldosterone-induced ENaC and Scnn1a-specific overexpression is accompanied by increased Tmprss2 gene expression, whereas Scnn1a silencing does not alter Tmprss2 transcription, suggesting that ENaC depends on Tmprss2 expression. This was confirmed by CRISPR-Cas9 Tmprss2 knockout which significantly downregulates Scnn1a gene and protein expression, and thus ENaC-mediated transepithelial sodium transport. Additionally, RNA sequencing analyses unveiled a drastic downregulation in EpCAM and claudin-3 and -7 gene expression, resulting in reduced protein expression also confirmed by immunocytochemistry. In summary, our data clearly demonstrates that the serine protease Tmprss2 is important in maintaining the epithelial tight junction barrier, in addition to regulating ENaC function via Scnn1a expression. Overall design: mRNA was harvested from three sequential passages, in triplicate, from two single control mCCDcl1 cell clones and two Tmprss2 knockout clones generated by CRISPR-Cas9.