Variations in the multimerization region of the Helicobacter pylori cytotoxin CagA affect virulence.

Helicobacter pylori colonizes the human stomach by infecting gastric epithelial cells. It is the primary cause of peptic ulcer disease and gastric cancer (GC). Cytotoxin-associated gene A (CagA) is a virulence factor produced by H. pylori. Strains positive for the CagA protein are associated with more severe gastric diseases. The 3' region of the cagA gene exhibits heterogeneity with respect to tyrosine phosphorylation motifs (EPIYA) and CagA multimerization motifs (CM). CagA proteins are categorized as either Western or Eastern based on EPIYA sequences. CM motifs are also identified as Western and Eastern based on CM sequences identified in Western and East Asian countries. It has been suggested that CagA proteins possessing an Eastern CM type are associated with less severe gastric disorders. In the present study, the effects of two CagA peptides with different CM motifs on cell function were compared: CagA with a Western and Eastern CM motif (CagA-WE), and CagA with two Western CM motifs (CagA-WW). CagA sequences were fused with green fluorescent protein (GFP) to form GFP-CagA fusion proteins. GFP-CagA and GFP control constructs were transfected into human gastric adenocarcinoma cells (AGS). GFP-CagA expression was verified by immunoblotting and immunofluorescence. The results demonstrated that, following 18 h, the CagA-WE-transfected cells were less adherent compared with the CagA-WW transfected cells. CagA has also been reported to cause cell elongation in AGS cells. In the current study, cell elongation was more frequent in the CagA-WW-transfected cells compared with the CagA-WE transfected cells (8.34 vs. 3.97% cells, respectively). The CagA peptides did not affect proliferation or apoptosis rates. These results suggest that different CM motif types may affect CagA virulence.