THE VACUOLAR ATPASE PROTON PUMP IS PRESENT ON INTRACELLULAR VACUOLES INDUCED BY HELICOBACTER-PYLORI

Cytotoxic strains of Helicobacter pylori cause an intense vacuolar deg eneration of cells, due to the enlargement of late endosomes in the pr esence of membrane permeant, weak bases. Bafilomycins, specific inhibi tors of the vacuolar-type (V-) ATPase proton pump, prevent vacuole for mation. The presence of the V-ATPase on vacuolar membranes was demonst rated by immunofluorescence with a monoclonal antibody (MAb) specific for the human 116-kDa regulatory subunit. The V-ATPase co-localised wi th the late endosomal marker rab7 on vacuolar membranes. In contrast, the early recycling endosomal compartment was not altered by the VacA cytotoxin, although it was endowed with the V-ATPase. Endocytosis of a MAb against the 116-kDa regulatory subunit of V-ATPase blocked endoso mal acidification in HeLa cells and prevented VacA action. These resul ts indicate that selective swelling of late endosomes, due to accumula tion of osmotically active weak bases driven by the V-ATPase, is essen tial for vacuole formation.