Sequence of Helicobacter pylori clinical isolate CagA and its effect on the morphology and function of gastric epithelial cells

Abstract:

[Background] Cytotoxin associated gene A protein (CagA) is one of the most important effectors of Helicobacter pylori, and its polymorphism is suggested to be involved in the development and progression of gastric carcinoma. [Objective] To compare the structural differences of CagA as an H. pylori clinical isolate, and explore its effects on the morphology and function of gastric epithelial cells. [Methods] A total of 27 sequences of CagA were analyzed to reveal the differences in composition and amino acids variation. Five H. pylori strains containing different CagA sequences were used to infect low malignant gastric epithelial AGS cells for 6 hours at a multiplicity of infection (MOI) of 30. Then the cell morphology was observed by the microscope and the expression of polarity-regulating kinase 1b (PAR1b) was determined by the Western Blot. Finally, the concentration of interleukin-8 (IL-8) in the medium was detected using enzyme-linked immunosorbent assay (ELISA). [Results] It was found that there were differences in the structure and composition of amino acid of CagA. In particular, the EPIYA motifs of Western strains was detected with more variation, and the cell morphology of the strain with the intact CagA gene changed significantly after infection. Compared with the control group, the expression of PAR1b in the AGS cells infected with Western strains of NCTC 11639 and 26695 increased significantly, while expression of PAR1b in the cells infected with East Asian strain GZ7 decreased significantly, and both of the differences were statistically significant (P<0.05). However, there was no significant difference in the expression of PAR1b in the AGS cells infected with H. pylori GZ15 and H. pylori GZ7/ΔcagA. The concentration of IL-8 in the experimental group was higher than that in the control group for East Asia and Western strains (P<0.05). Furthermore, the potential of East Asia strains to promote IL-8 secretion was greater than that of Western strains. [Conclusion] H. pylori containing different CagA performs different biological functions. The East Asian strains can inhibit the expression of PAR1b and have a more vital ability to promote the secretion of IL-8. In addition, the changes in cell morphology caused by H. pylori depend on the integrity of the cagA.

Key words:Helicobacter pylori, CagA, EPIYA motif, PAR1b, IL-8