EGF Regulates Claudin-2 and -4 Expression Through Src and STAT3 in MDCK Cells

Epidermal Growth Factor (EGF) is a key regulator of epithelial paracellular permeability, a property that depends on tight junctions (TJ) and can be evaluated through the measurement of the transepithelial electrical resistance (TER). EGF increases the TER of MDCK monolayers by inducing ERK1/2‐dependent downregulation of claudin‐2 (CLDN‐2) and upregulation of claudin‐4 (CLDN‐4). Because either increments or decrements in TER often involve Src activation and epithelial cell differentiation occasionally depends on STAT3, here we investigated whether EGF might control CLDN‐2 downregulation and CLDN‐4 upregulation through those proteins. We found that EGF induces Src activation necessary for the reduction of CLDN‐2 at the TJ, the degradation of this CLDN, the reduction of the cellular levels of its mRNA and the resulting increase of TER. EGF‐induced changes on CLDN‐2 protein and mRNA also depend on STAT3 activity. This growth factor increases the levels of STAT3 phosphorylated at Y705 in the nucleus, a process that depends on Src activation. Interestingly, Src and STAT3 activation do not exclusively mediate the EGF‐induced downregulation of CLDN‐2, but they are also implicated in the EGF‐induced CLDN‐4 transcription, translation, and exocytic fusion into TJ. Our results indicate that EGF controls the levels of CLDN‐2 and ‐4 proteins and mRNAs through Src and STAT3 activity. J. Cell. Physiol. 230: 105–115, 2015. © 2014 Wiley Periodicals, Inc.