Determinants and consequences of different levels of CagA phosphorylation for clinical isolates of Helicobacter pylori

Richard H. Argent*, Mark Kidd, Robert J. Owen, Rachael J. Thomas, Marie C. Limb, John C. Atherton

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    182 Citations (Scopus)


    Background & Aims: The Helicobacter pylori cag pathogenicity island encodes a secretory system that translocates CagA into epithelial cells, where it becomes tyrosine phosphorylated and induces cytoskeletal rearrangements. Strains with more CagA tyrosine phosphorylation motifs are most closely associated with gastric cancer. Here we assess whether clinical strains can deliver CagA, whether strains with different numbers of CagA phosphorylation motifs have CagA phosphorylated to different degrees, and whether this induces different amounts of epithelial cytoskeletal change. Methods: Forty-four H. pylori strains from South African patients, all cagA gene positive, were cocultured with the gastric adenocarcinoma cell line AGS. CagA expression and phosphorylation were determined by Western blot and interleukin-8 secretion by enzyme-linked immunosorbent assay. The cagA 3′ variable regions of 22 strains were sequenced and shown to possess 3-6 phosphorylation motifs. These strains were used to quantify CagA phosphorylation and cytoskeletal rearrangements. Results: cagA genotype and typing of cag pathogenicity island genes were poorly predictive of phenotype. Thirty-four of 44 strains expressed CagA protein that could be delivered to and phosphorylated within AGS cells. Only these 34 strains induced interleukin-8 secretion from AGS cells. Among those strains, the number of CagA tyrosine phosphorylation motifs determined the degree of CagA phosphorylation and the level of biologic activity in terms of degree and extent of AGS cell elongation. Conclusions: H. pylori strains that deliver CagA with more phosphorylation motifs induce higher levels of CagA phosphorylation in epithelial cells, induce more cytoskeletal changes, and are more likely to be associated with gastric cancer.

    Original languageEnglish
    Pages (from-to)514-523
    Number of pages10
    Issue number2
    Publication statusPublished - Aug 2004

    Bibliographical note

    Funding Information:
    Supported by a grant from Cancer Research UK. J.C.A. is funded by a senior clinical fellowship from the Medical Research Council (United Kingdom).


    • ELISA
    • IL
    • PCR
    • PaI
    • TFSS
    • TPM
    • enzyme-linked immunosorbent assay
    • interleukin
    • pathogenicity island
    • polymerase chain reaction
    • type IV secretory system
    • tyrosine phosphorylation motif


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