Helicobacter pylori CagA promotes Snail-mediated epithelial-mesenchymal transition by reducing GSK-3 activity.

Cytotoxin-associated gene A (CagA) is an oncoprotein and a major virulence factor of H. pylori. CagA is delivered into gastric epithelial cells via a type IV secretion system and causes cellular transformation. The loss of epithelial adhesion that accompanies the epithelial-mesenchymal transition (EMT) is a hallmark of gastric cancer. Although CagA is a causal factor in gastric cancer, the link between CagA and the associated EMT has not been elucidated. Here, we show that CagA induces the EMT by stabilizing Snail, a transcriptional repressor of E-cadherin expression. Mechanistically we show that CagA binds GSK-3 in a manner similar to Axin and causes it to shift to an insoluble fraction, resulting in reduced GSK-3 activity. We also find that the level of Snail protein is increased in H. pylori infected epithelium in clinical samples. These results suggest that H. pylori CagA acts as a pathogenic scaffold protein that induces a Snail-mediated EMT via the depletion of GSK-3.