Cell vacuolation induced by the VacA cytotoxin of Helicobacter pylori is regulated by the Rac1 GTPase

Chronic gastric infection with the Gram-negative bacterium Helicobacter pyl ori is a major contributing factor in the development of duodenal ulcers an d is believed to be a significant risk factor in the development of gastric tumors. The VacA cytotoxin of H. pylori is a 90-kDa secreted protein that forms trans-membrane ion channels. In epithelial cells, VacA activity is as sociated with the rapid formation of acidic vacuoles enriched for late endo somal and lysosomal markers. Rad is a member of the Rho family of small GTP -binding proteins that regulate reorganization of the actin cytoskeleton an d intracellular signal transduction and are being shown increasingly to pla y a role in membrane trafficking events. In this study we report that: (i) green fluorescent-tagged Rad localizes around the perimeter of the vacuoles induced by VacA; (ii) expression of dominant negative Rad in epithelial ce lls inhibits vacuole formation; (iii) expression of constitutively active R ad potentiates the activity of VacA. Taken together, these data demonstrate a role for Rad in the regulation of VacA activity.