HELICOBACTER-PYLORI TOXIN VACA INDUCES VACUOLE FORMATION BY ACTING INTHE CELL CYTOSOL

Cells exposed to Helicobacter pylori toxin VacA develop large vacuoles that originate from massive swelling of membranous compartments of la te stages of the endocytic pathway. To determine if the toxin is activ e from the cell cytosol, cells were either micro-injected with toxin o r transfected with plasmids encoding VacA. Both procedures cause forma tion of intracellular vacuoles. Cytosolic localization of the toxin wa s assessed by indirect immunofluorescence with specific antibodies and by expression of an active green fluorescence protein (GFP)-VacA chim era. Vacuoles induced by internally produced VacA are morphologically and functionally identical to those induced by externally added toxin. It is concluded that VacA is a toxin acting intracellularly by alteri ng a cytosol-exposed target, possibly involved in the control of membr ane trafficking.