title: Activation of Abl by Helicobacter pylori: a novel kinase for CagA and crucial mediator of host cell scattering.
abstract: OBJECTIVE
  The pathogenesis of Helicobacter pylori (Hp)-associated diseases depends on a specialized type IV secretion system. This type IV secretion system injects the cytotoxin-associated gene A (CagA) effector protein into target cells where CagA becomes phosphorylated on tyrosine residues by Src. Src then is inactivated rapidly, suggesting the presence of another host tyrosine kinase to ensure constant CagA phosphorylation in sustained Hp infections. We aimed to identify this kinase.
  
  
  METHODS
  By using the AGS gastric epithelial cell model, we performed a detailed functional characterization of Abl tyrosine kinase in signaling during Hp infections.
  
  
  RESULTS
  We showed that Abl kinase is activated and a novel crucial mediator of Hp infections. First, Abl-specific inhibitors SKI-DV2-43 or STI571 (Gleevec, Novartis) and knockdown of c-Abl/Abl-related gene Arg by small hairpin and interfering RNAs efficiently inhibit CagA phosphorylation and cell scattering. Second, during infection, Abl is activated rapidly by autophosphorylation at Y-412. Third, both Abl and Src phosphorylated Y-899, Y-918, and Y-972 of CagA. Fourth, we found that the Abl substrate CrkII is phosphorylated at Y-221 in vivo. Fifth, overexpression of kinase-dead Abl (K290M) blocked Hp-induced actin cytoskeletal rearrangements. We further showed that sustained activity of Abl is required to maintain CagA in a phosphorylated state. Moreover, phosphorylated CagA forms a physical complex with Abl and activated CrkII in vivo.
  
  
  CONCLUSIONS
  We propose a model in which Hp has evolved a mechanism to use at least 2 tyrosine kinases, Abl and Src, for CagA phosphorylation and subsequent actin-cytoskeletal rearrangements leading to cell scattering and elongation.
authors.affiliation: Department of Medical Microbiology, Otto von Guericke University, Magdeburg, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Tammer
authors.forename: Sabine
authors.initials: S
authors.lastname: Brandt
authors.forename: Roland
authors.initials: R
authors.lastname: Hartig
authors.forename: Wolfgang
authors.initials: W
authors.lastname: König
authors.forename: Steffen
authors.initials: S
authors.lastname: Backert
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001549:Benzamides; D002460:Cell Line; D004848:Epithelium / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D005753:Gastric Mucosa / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D005786:Gene Expression Regulation; D016481:Helicobacter Infections / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016480:Helicobacter pylori / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D015151:Immunoblotting; D047468:Immunoprecipitation; D034982:Integration Host Factors / Q000235:genetics; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D012329:RNA, Bacterial / Q000235:genetics*; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D001549:Benzamides; D034982:Integration Host Factors; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D012329:RNA, Bacterial; C080866:cagA protein, Helicobacter pylori; D000068877:Imatinib Mesylate; C426236:ARG tyrosine kinase; D011505:Protein-Tyrosine Kinases; D019061:src-Family Kinases