Pathogenic interactions between Helicobacter pylori adhesion protein HopQ and human cell surface adhesion molecules CEACAMs in gastric epithelial cells

The present paper aims to review the studies describing the interactions between HopQ and CEACAMs along with possible mechanisms responsible for pathogenicity of Helicobacter pylori. The literature was searched on “PubMed” using different key words including Helicobacter pylori, CEACAM and gastric. HopQ is one of the outer membrane proteins of H. pylori and belongs to the family of adhesin proteins. In contrast to other adhesins, HopQ interacts with host cell surface molecules in a glycan independent manner. Human CEACAMs are the cell surface adhesion molecules mainly present on the epithelial cells, endothelial cells and leukocytes. The overexpression of these molecules may contribute to cancer progression and relapse. Recent studies have shown that HopQ may interact with human CEACAMs, particularly CEACAM1, CEACAM3, CEACAM5 and CEACAM6, but not CEACAM8. HopQ interacts with GFCC’C” interaction surface of IgV domain of N- terminal region of CEACAM1. Moreover, binding of HopQ to CEACAM1 prevent its trans-dimerization and stabilizes it in monomeric form. H. pylori may use these HopQ-CEACAM interactions to transfer its CagA oncoprotein into host gastric epithelial cells, which is followed by its phosphorylation and release of interleukin-8. HopQ-CEACAM interactions may also utilize T4SS, instead of CagA, to activate NF-κB signaling and trigger inflammation. HopQ of H. pylori may interact with CEACAMs of the human gastric cells to induce the development of gastric ulcers and cancers by transferring CagA oncoprotein or inducing activation of T4SS to initiate and maintain inflammatory reactions.