Enteropathogenic bacteria evade ROCK-driven epithelial cell extrusion

Diverse pathogen-encoded virulence factors disable apoptosis, pyroptosis or necroptosis, the host cell death programs that remove infected cells1. In the intestine, the extrusion of infected cells into the lumen for elimination provides an additional layer of host defence, but no virulence mechanisms that target the cytoskeletal changes required are known2. Here we show that the Escherichia coli ubiquitin ligase NleL is an inhibitor of intestinal epithelial cell (IEC) extrusion, targeting caspase-4, ROCK1 and ROCK2 for proteasomal degradation. Genetic deletion of Rock1 and Rock2 from cultured IECs diminished inflammasome-induced IEC extrusion. Moreover, mice with Rock1- and Rock2-deficient IECs were less effective than wild-type mice at constraining the numbers of Citrobacter rodentium in the colon. Notably, NleL-deficient C. rodentium triggered more IEC extrusion than did wild-type C. rodentium, resulting in diminished colonization of the colon in infected mice. Our work highlights a host–pathogen arms race focused on dynamic regulation of the host epithelial barrier. The bacterial ubiquitin ligase NleL evades host defence mechanisms both by inhibiting pyroptosis and by preventing infected intestinal epithelial cells from being extruded into the lumen and expelled in the faeces.