title: CagA Phosphorylation in Helicobacter pylori-Infected B Cells Is Mediated by the Nonreceptor Tyrosine Kinases of the Src and Abl Families.
abstract: CagA is one of the most important virulence factors of the human pathogen Helicobacter pylori CagA expression can be associated with the induction of severe gastric disorders such as gastritis, ulceration, gastric cancer, or mucosa-associated lymphoid tissue (MALT) lymphoma. After translocation through a type IV secretion system into epithelial cells, CagA is tyrosine phosphorylated by kinases of the Src and Abl families, leading to drastic cell elongation and motility. While the functional role of CagA in epithelial cells is well investigated, knowledge about CagA phosphorylation and its associated signal transduction pathways in B cells is only marginal. Here, we established the B cell line MEC1 derived from a B cell chronic lymphocytic leukemia (B-CLL) patient as a new infection model to study the signal transduction in B cells controlled by H. pylori We observed that CagA was rapidly injected, strongly tyrosine phosphorylated, and cleaved into a 100-kDa N-terminal and a 40-kDa C-terminal fragment. To identify upstream signal transduction pathways of CagA phosphorylation in MEC1 cells, pharmacological inhibitors were employed to specifically target Src and Abl kinases. We observed that CagA phosphorylation was strongly inhibited upon treatment with an Src inhibitor and slightly diminished when the Abl kinase inhibitor imatinib mesylate (Gleevec) was applied. The addition of dasatinib to block c-Abl and Src kinases led to a complete loss of CagA phosphorylation. In conclusion, these results demonstrate an important role for Src and Abl tyrosine kinases in CagA phosphorylation in B cells, which represent druggable targets in H. pylori-mediated gastric MALT lymphoma.
authors.affiliation: Cancer Cluster Salzburg, Department of Molecular Biology, Division of Microbiology, Paris-Lodron University, Salzburg, Austria.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Krisch
authors.affiliation: Cancer Cluster Salzburg, Department of Molecular Biology, Division of Microbiology, Paris-Lodron University, Salzburg, Austria.
authors.forename: Gernot
authors.initials: G
authors.lastname: Posselt
authors.affiliation: Department of Molecular Biology, Division of Allergy and Immunology, Paris-Lodron University, Salzburg, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Hammerl
authors.affiliation: Cancer Cluster Salzburg, Department of Molecular Biology, Division of Microbiology, Paris-Lodron University, Salzburg, Austria silja.wessler@sbg.ac.at.
authors.forename: Silja
authors.initials: S
authors.lastname: Wessler
mesh_terms: D000942:Antigens, Bacterial / Q000378:metabolism*; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D005753:Gastric Mucosa / Q000382:microbiology; D016481:Helicobacter Infections / Q000378:metabolism / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate / Q000494:pharmacology; D018442:Lymphoma, B-Cell, Marginal Zone / Q000378:metabolism / Q000382:microbiology; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D020298:U937 Cells; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D047428:Protein Kinase Inhibitors; C080866:cagA protein, Helicobacter pylori; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016315:Proto-Oncogene Proteins c-abl; D019061:src-Family Kinases