HopQ impacts the integrin α5β1-independent NF-κB activation by Helicobacter pylori in CEACAM expressing cells

Helicobacter pylori infection persists in more than half of the world's population and represents a risk factor for peptic ulcer disease and gastric cancer. Virulent strains of H. pylori carry a cag pathogenicity island (cagPAI), which encodes a type IV secretion system (T4SS) with the capability to inject the effector protein cytotoxin-associated gene A (CagA) into eukaryotic cells. Colonisation of the gastric epithelium by H. pylori provokes direct activation of the proinflammatory and survival factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). We investigated the impact of host cell receptor integrin α5β1 and the bacterial adhesin HopQ on the NF-κB activation. We found that H. pylori induced early T4SS-dependent, but CagA-independent canonical NF-κB signalling in polarized, apical infected NCI-N87 cells. Integrin-dependent CagA translocation was hardly detectable, as integrin β1 was sparsely located at the apical surface of polarized NCI-N87 cells. Knockdown experiments indicated that integrin α5β1 and integrin linked kinase (ILK) were dispensable for NF-κB activation in H. pylori infection. Thus, there exists no common mechanism, which mediates integrin α5β1-dependent H. pylori-triggered CagA translocation and the activation of NF-κB. Further, we report that H. pylori adhesin HopQ, which binds to a specific subset of carcinoembryonic antigen-related cell adhesion molecules (CEACAMs), promotes canonical NF-κB activation in AGS and NCI-N87 cells, but not in HeLa cells, which are devoid of these CEACAMs. Noteworthy, these effects were not mediated by reduced adhesion, indicating additional functions of HopQ.