Expression of Kinase-inactive c-Src Delays Oxidative Stress-induced Disassembly and Accelerates Calcium-mediated Reassembly of Tight Junctions in the Caco-2 Cell Monolayer

The activity of Src kinases appears to play a role in both assembly and disassembly of tight junction. However, the role of a specific isoform of Src kinase in regulation of tight junction is not known. In the present study the role of c-Src in regulation of epithelial tight junction was investigated in Caco-2 cell monolayers. Oxidative stress (xanthine oxidase + xanthine) induced an activation and membrane translocation of c-Src. The oxidative stress-induced decrease in transepithelial electrical resistance, increase in inulin permeability, and redistribution of occludin and ZO-1 from the intercellular junctions were prevented by PP2. The rates of oxidative stress-induced activation of c-Src, tyrosine phosphorylation of ZO-1 and β-catenin, decrease in resistance, increase in permeability to inulin, and redistribution of occludin and ZO-1 were significantly greater in cells transfected with wild type c- Src , whereas it was low in cells transfected with kinase-inactive c- Src K297R mutant, when compared with those in empty vector-transfected cells. The rates of recovery of resistance, increase in barrier to inulin, and reorganization of occludin and ZO-1 into the intercellular junctions during the calcium-induced reassembly of tight junction were much greater in Caco-2 cells transfected with c- Src K297R as compared with those in cells transfected with empty vector or wild type c- Src . These results show that the dominant-negative expression of kinase-inactive c- Src delays the oxidative stress-induced disruption of tight junction and accelerates calcium-induced assembly of tight junction in Caco-2 cells and demonstrate that oxidative stress-induced disruption of tight junction is mediated by the activation of c- Src .