the VacA toxin of Helicobacter pylori identifies a new intermediate filament-interacting protein

The VacA toxin produced by Helicobacter pylori acts inside cells and induces the formation of vacuoles arising from late endosomal/lysosomal compartments. Using VacA as bait in a yeast two-hybrid screening of a HeLa cell library, we have identified a novel protein of 54 kDa (VIP54), which interacts specifically with VacA, as indicated by co-immunoprecipitation and binding experiments. VIP54 is expressed in cultured cells and many tissues, with higher expression in the brain, muscle, kidney and liver. Confocal immunofluorescence microscopy with anti-VIP54 affinity- purified antibodies shows a fibrous pattern typical of intermediate filaments. Double label immunofluorescence performed on various cell lines with antibodies specific to different intermediate filament proteins revealed that VIP54 largely co-distributes with vimentin. In contrast to known intermediate filament proteins, VIP54 is predicted to contain approximately 50% of helical segments, but no extended coiled-coil regions. The possible involvement of this novel protein in interactions between intermediate filaments and late endosomal compartments is discussed.