title: Potentiation of Helicobacter pylori CagA protein virulence through homodimerization.
abstract: Chronic infection with Helicobacter pylori cagA-positive strains is associated with atrophic gastritis, peptic ulceration, and gastric carcinoma. The cagA gene product, CagA, is delivered into gastric epithelial cells via type IV secretion, where it undergoes tyrosine phosphorylation at the EPIYA motifs. Tyrosine-phosphorylated CagA binds and aberrantly activates the oncogenic tyrosine phosphatase SHP2, which mediates induction of elongated cell morphology (hummingbird phenotype) that reflects CagA virulence. CagA also binds and inhibits the polarity-regulating kinase partitioning-defective 1 (PAR1)/microtubule affinity-regulating kinase (MARK) via the CagA multimerization (CM) sequence independently of tyrosine phosphorylation. Because PAR1 exists as a homodimer, two CagA proteins appear to be passively dimerized through complex formation with a PAR1 dimer in cells. Interestingly, a CagA mutant that lacks the CM sequence displays a reduced SHP2 binding activity and exhibits an attenuated ability to induce the hummingbird phenotype, indicating that the CagA-PAR1 interaction also influences the morphological transformation. Here we investigated the role of CagA dimerization in induction of the hummingbird phenotype with the use of a chemical dimerizer, coumermycin. We found that CagA dimerization markedly stabilizes the CagA-SHP2 complex and thereby potentiates SHP2 deregulation, causing an increase in the number of hummingbird cells. Protrusions of hummingbird cells induced by chemical dimerization of CagA are further elongated by simultaneous inhibition of PAR1. This study revealed a role of the CM sequence in amplifying the magnitude of SHP2 deregulation by CagA, which, in conjunction with the CM sequence-mediated inhibition of PAR1, evokes morphological transformation that reflects in vivo CagA virulence.
authors.affiliation: Division of Microbiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Lisa
authors.initials: L
authors.lastname: Nagase
authors.forename: Naoko
authors.initials: N
authors.lastname: Murata-Kamiya
authors.forename: Masanori
authors.initials: M
authors.lastname: Hatakeyama
mesh_terms: D049933:Aminocoumarins / Q000494:pharmacology; D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D027081:DNA Gyrase / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D016480:Helicobacter pylori / Q000187:drug effects / Q000472:pathogenicity*; D006801:Humans; D050505:Mutant Proteins / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D055503:Protein Multimerization / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013270:Stomach / Q000166:cytology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014774:Virulence / Q000187:drug effects
chemical_list: D049933:Aminocoumarins; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D050505:Mutant Proteins; D011993:Recombinant Fusion Proteins; C080866:cagA protein, Helicobacter pylori; D019000:Phosphotyrosine; C094670:MARK2 protein, human; D017346:Protein Serine-Threonine Kinases; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D027081:DNA Gyrase; C004628:coumermycin