Helicobacter pylori CagA protein - the first identified bacterial oncoprotein

Helicobacter pylori is a gramnegative spiral-shaped epsilon-Proteobacterium, which colonizes the gastric mucosa of humans. Infections caused by H. pylori are associated with different symptoms ranging from mild gastritis to ulcers. CagA is a highly immunogenic, polymorphic protein and the main H. pylori virulence factor. Infection with cagA-positive H. pylori is associated with the risk of development of gastric adenocarcinoma. CagA injected into eukaryotic cells by the type IV transport system apparatus interacts with various host proteins influencing many signal-transduction pathways in a phosphorylation-dependent and phosphorylation-independent manner. These interactions result in the perturbations of cell morphology, proliferation, differention and spreading. All these interactions influence the process of carcinogenesis. Recently conducted experiments on transgenic mice producing CagA documented that CagA is a bacterial oncoprotein. The presented review summarizes the recent achievements concerning the details of CagA interaction with host proteins.