Clostridium difficile toxin CDT hijacks microtubule organization and reroutes vesicle traffic to increase pathogen adherence

Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis by the actions of Rho-glucosylating toxins A and B. Recently identified hypervirulent strains, which are associated with increased morbidity and mortality, additionally produce the actin-ADP-ribosylating toxin C. difficile transferase (CDT). CDT depolymerizes actin, causes formation of microtubule-based protrusions, and increases pathogen adherence. Here we show that CDT-induced protrusions allow vesicle traffic and contain endoplasmic reticulum tubules, connected to microtubules via the calcium sensor Stim1. The toxin reroutes Rab11-positive vesicles containing fibronectin, which is involved in bacterial adherence, from basolateral to the apical membrane sides in a microtubule-and Stim1-dependent manner. The data yield a model of C. difficile adherence regulated by actin depolymerization, microtubule restructuring, subsequent Stim1-dependent Ca2+ signaling, vesicle rerouting, and secretion of ECM proteins to increase bacterial adherence.