Transmembrane serine protease 2 and proteolytic activation of the epithelial sodium channel in mouse kidney: Late effects of aldosterone

The appropriate regulation of the epithelial sodium channel (ENaC) in the aldosterone-sensitive distal nephron is required for sodium homeostasis and thereby for the long-term regulation of arterial blood pressure. A unique feature of ENaC is its activation by proteolytic cleavage. However, the relevant proteases involved in proteolytic ENaC activation in the kidney remain elusive. Here, we examined a potential role of transmembrane serine protease 2 (TMPRSS2). A mouse cortical collecting duct cell line (mCCDcl1) was used as a model system. We performed RNA-Seq transcriptome analysis of mCCDcl1 cells, which confirmed coexpression of Tmprss2 and all three ENaC subunits (Scnn1a, Scnn1b, Scnn1g) in this cell line. Importantly, high baseline expression of TMPRSS2 was detected in these cells without a stimulatory effect of aldosterone on its function or transcription. TMPRSS2 knockout in mCCDcl1 cells compromised γ-ENaC cleavage and reduced baseline and aldosterone-stimulated transepithelial short-circuit currents, which could be rescued by chymotrypsin. A compensatory transcriptional upregulation of other proteases was not observed. From these findings we conclude that TMPRSS2 is likely to contribute to proteolytic ENaC activation in the kidney.