Translocation of the Helicobacter pylori CagA protein in gastric epithelial cells by a type IV secretion apparatus

Helicobacter pylori is one of the most common bacterial pathogens, infectin g about 50% of the world population. The presence of a pathogenicity island (PAI) in H. pylori has been associated with gastric disease. We present ev idence that the H. pylori protein encoded by the cytotoxin-associated gene A (cagA) is translocated and phosphorylated in infected epithelial cells. T wo-dimensional gel electrophoresis (2-DE) of proteins isolated from infecte d AGS cells revealed H. pylori strain-specific and time-dependent tyrosine phosphorylation and dephosphorylation of several 125-135 kDa and 75-80 kDa proteins. Immunoblotting studies, matrix-assisted laser desorption/ionizati on mass spectrometry (MALDI-MS), cell fractionation and confocal microscopy demonstrated that one of the 125-135 kDa proteins represents the H. pylori CagA protein, which is translocated into the host cell membrane and the cy toplasm. Translocation of CagA was dependent on functional cagA gene and vi rulence (vir) genes of a type IV secretion apparatus composed of virB4, vir B7, virB10, virB11 and virD4 encoded in the cag PAI of H. pylori. Our findi ngs support the view that H. pylori actively translocates virulence determi nants, including CagA, which could be involved in the development of a vari ety of gastric disease.