Preliminary study and bioinformatics analysis on the potential role of CagQ in type IV secretion system of H.pylori

Helicobacter pylori (H.pylori), is a major causative agent of chronic gastritis, gastric carcinoma and duodenal ulcer. Remarkably, H.pylori carries cytotoxin-associated gene pathogenicity island (CagPAI) which encodes a type IV secretion system (T4SS). T4SS is capable of forming a syringe-like structure to deliver oncoprotein cytotoxin-associated Antigen (CagA) into gastric epithelial cells and resulting in a cascade of events in host cells, such as induction of pro-inflammatory cytokines, alteration of cellular gene expression and cytoskeletal rearrangements. Among of those proteins in T4SS, CagQ still remains unknown functions. In this study, we performed analysis of protein-protein interaction and revealed that CagQ correlated with the most virulence factor CagA in T4SS. Interestingly, our data demonstrated that CagQ-deficient mutant strain had significantly lower expression in both mRNA and protein levels of CagA compared with H.pylori wild-type strain 26695. Moreover, we demonstrated that CagQ deletion also played a vital role in suppressing CagA-induced apoptosis of host gastric epithelial cells. To further investigate the role of CagQ in T4SS, we used bioinformatics analysis to provide a preliminary insight into CagQ. These results showed that CagQ possessed a transmembrane region from amino acid 50-68 which is also consistent with the prediction of hydrophobic scale and structure modeling. Thus, we conclude that CagQ is a membrane protein in T4SS and is crucial for maintaining CagA expression and CagA-induced apoptotic effects. This provides a novel specific therapeutic target for H.pylori CagA-induced gastroduodenal diseases.