Epithelial cells challenged with a Rac-activating E. coli cytotoxin acquire features of professional phagocytes.

Activation of Rho, Rac and Cdc42 GTPases by an Escherichia coli cytotoxin (CNF1) has been reported to induce a phagocytic-like activity by epithelial cells in terms of a ruffle-driven capture and ingestion of large material. More recently, it has been reported that treatment with CNF1 induces superoxide anion release by these cells following a phagocytic stimulus. We herein show that in epithelial cells both transfection with the dominant form of Rac (RacV12) and treatment with the Rac-activating epidermal growth factor (EGF) may increase the secretion of superoxide anions on challenge with latex beads. Moreover, exposure to CNF1 induces a significant augmentation of acidic vesicles where the internalized particles were detectable. Our results indicate that (i) Rac is a pivotal GTPase for inducing in epithelial cells superoxide anion generation and (ii) the internalized material travels trough acidic compartments in CNF1-treated epithelial cells. Altogether this suggests a novel role for epithelial cells that, following Rac activation, might share with professional phagocytes the task of eliminating unwanted pathogens.