Pseudomonas aeruginosa ExoT inhibits in vitro lung epithelial wound repair

The nosocomial pathogen Pseudomonas aeruginosa causes clinical infection in the setting of pre-existing epithelial tissue damage, an association that is mirrored by the increased ability of P. aeruginosa to bind, invade and d amage injured epithelial cells in vitro. In this study, we report that P. a eroginosa inhibits the process of epithelial wound repair in vitro through the type III-secreted bacterial protein ExoT, a GTPase-activating protein ( GAP) for Rho family GTPases. This inhibition primarily targets cells at the edge of the wound, and causes actin cytoskeleton collapse, cell rounding a nd cell detachment. ExoT-dependent inhibition of wound repair is mediated t hrough the GAP activity of this bacterial protein, as mutations in ExoT tha t alter the conserved arginine (R149) within the GAP domain abolish the abi lity of P. aeruginosa to inhibit wound closure. Because ExoT can also inhib it P. aeruginosa internalization by phagocytes and epithelial cells, this p rotein may contribute to the in vivo virulence of P. aeruginosa by allowing organisms both to overcome local host defences, such as an intact epitheli al barrier, and to evade phagocytosis by immune effector cells.