Formation of anion-selective channels in the cell plasma membrane by the toxin VacA of Helicobacter pylori is required for its biological activity

The vacuolating toxin VacA, a major determinant of Helicobacter pylori-asso ciated gastric diseases, forms anion-selective channels in artificial plana r lipid bilayers. Here we show that VacA increases the anion permeability o f the HeLa cell plasma membrane and determines membrane depolarization. Ele ctrophysiological and pharmacological approaches indicated that this effect is due to the formation of low-conductance VacA pores in the cell plasma m embrane and not to the opening of Ca2+- or volume-activated chloride channe ls. VacA-dependent increase of current conduction both in artificial planar lipid bilayers and in the cellular system was effectively inhibited by the chloride channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPP B), while2-[(2-cyclopentenyl-6,7-dichloro-2,3-dihydro-2-methyl- 1-oxo-1H-in den-5-yl)oxy] acetic acid (IAA-94) was less effective. NPPB inhibited and p artially reversed the vacuolation of HeLa cells and the increase of ion con ductivity of polarized Madine Darby canine kidney cell monolayers induced b y VacA, while IAA-94 had a weaker effect. We conclude that pore formation b y VacA accounts for plasma membrane permeabilization and is required for bo th cell vacuolation and increase of trans-epithelial conductivity.