Helicobacter pylori CagA Induces Cortactin Y-470 Phosphorylation-Dependent Gastric Epithelial Cell Scattering via Abl, Vav2 and Rac1 Activation

Simple Summary

Various microbial pathogens target the actin-binding protein cortactin to promote their own uptake, proliferation and spread, and exhibit proposed roles in human cancerogenesis. We aimed to study the molecular mechanisms of how the gastric pathogen Helicobacter pylori hijacks cortactin phosphorylation via tyrosine kinase Abl to trigger cancer-related signal transduction events. We discovered that cortactin phosphorylated at Y-470 recruits the signaling factor Vav2 to activate the small Rho GTPase Rac1, and finally, a cancer cell motility phenotype. We also demonstrate that phosphorylation of cortactin at Y-470 can be completely inhibited by the well-known Abl inhibitor imatinib. Imatinib is an established oral chemotherapy medication, employed for efficient systemic treatment of various cancers. These results reveal a comprehensive novel pathway for how precisely H. pylori manipulates host signaling in gastric disease development, and may pave the way for new opportunities of treatment of the outcome of infections with this pathogen, i.e., through using imatinib.

Abstract

The pathogen Helicobacter pylori is the first reported bacterial type-1 carcinogen playing a role in the development of human malignancies, including gastric adenocarcinoma. Cancer cell motility is an important process in this scenario, however, the molecular mechanisms are still not fully understood. Here, we demonstrate that H. pylori subverts the actin-binding protein cortactin through its type-IV secretion system and injected oncoprotein CagA, e.g., by inducing tyrosine phosphorylation of cortactin at Y-470, which triggers gastric epithelial cell scattering and motility. During infection of AGS cells, cortactin was discovered to undergo tyrosine dephosphorylation at residues Y-421 and Y-486, which is mediated through inactivation of Src kinase. However, H. pylori also profoundly activates tyrosine kinase Abl, which simultaneously phosphorylates cortactin at Y-470. Phosphorylated cortactin interacts with the SH2-domain of Vav2, a guanine nucleotide exchange factor for the Rho-family of GTPases. The cortactin/Vav2 complex then stimulates a previously unrecognized activation cascade including the small GTPase Rac1, to effect actin rearrangements and cell scattering. We hypothesize that injected CagA targets cortactin to locally open the gastric epithelium in order to get access to certain nutrients. This may disturb the cellular barrier functions, likely contributing to the induction of cell motility, which is important in gastric cancer development.