αPix interacts with Helicobacter pylori CagA to induce IL-8 expression in gastric epithelial cells

Objective. Helicobacter pylori CagA, translocated into gastric epithelial cells, induces IL-8 expression through the signalling pathways, including extracellular signal-regulated kinase (ERK) and nuclear factor-kappa B (NF-kappa B). We previously demonstrated that CagA interacts with host alpha Pix. The present study was purposed to determine the role of the interaction of alpha Pix with CagA on the signalling pathways for IL-8 expression in H. pylori-infected gastric epithelial cells. Material and methods. H. pylori HP99 strain (CagA+, VacA+) was infected to gastric epithelial AGS cells transfected with nontargeting (NT) or alpha Pix-targeting siRNA. Activation of signalling molecules including p21-activated kinase (PAK), ERK and NF-kappa B, and expression of IL-8 in the cells were assessed. Results. H. pylori CagA was delivered into AGS cells and then interacted with aPix at 4 h following H. pylori infection. PAK1, ERK and NF-kappa B were activated in the cells containing NT and alpha Pix siRNA at 1-2 h following H. pylori infection. However, after 4 h, the time when CagA was delivered into the cells, the activations of PAK1, ERK and NF-kappa B were inhibited by down-regulation of aPix using siRNA but not by NT siRNA. The results indicate that alpha Pix is required for H. pylori-mediated signalling of PAK1, ERK and NF-kappa B. Additionally, alpha Pix siRNA suppressed IL-8 induction after translocation of CagA into the cells, indicating that interaction of CagA with alpha Pix is critical for CagA-mediating signalling for IL-8 expression. Conclusions. The interaction of alpha Pix with CagA activates PAK1, ERK and NF-kappa B, which induces IL-8 expression in H. pylori-infected gastric epithelial cells.