title: Structural basis and functional consequence of Helicobacter pylori CagA multimerization in cells.
abstract: Helicobacter pylori cagA-positive strains are associated with gastric adenocarcinoma. The cagA gene product CagA is delivered into gastric epithelial cells where it localizes to the plasma membrane and undergoes tyrosine phosphorylation at the EPIYA-repeat region, which contains the EPIYA-A segment, EPIYA-B segment, and Western CagA-specific EPIYA-C or East Asian CagA-specific EPIYA-D segment. In host cells, CagA specifically binds to and deregulates SHP-2 phosphatase via the tyrosine-phosphorylated EPIYA-C or EPIYA-D segment, thereby inducing an elongated cell shape known as the hummingbird phenotype. In this study, we found that CagA multimerizes in cells in a manner independent of its tyrosine phosphorylation. Using a series of CagA mutants, we identified a conserved amino acid sequence motif (FPLXRXXXVXDLSKVG), which mediates CagA multimerization, within the EPIYA-C segment as well as in a sequence that located immediately downstream of the EPIYA-C or EPIYA-D segment. We also found that a phosphorylation-resistant CagA, which multimerizes but cannot bind SHP-2, inhibits the wild-type CagA-SHP-2 complex formation and abolishes induction of the hummingbird phenotype. Thus, SHP-2 binds to a preformed and tyrosinephosphorylated CagA multimer via its two Src homology 2 domains. These results, in turn, indicate that CagA multimerization is a prerequisite for CagA-SHP-2 interaction and subsequent deregulation of SHP-2. The present work raises the possibility that inhibition of CagA multimerization abolishes pathophysiological activities of CagA that promote gastric carcinogenesis.
authors.affiliation: Division of Molecular Oncology, Institute for Genetic Medicine, Hokkaido University, Kita-15 Nishi-7, Kita-ku, Sapporo 060-0815, Japan.
authors.forename: Shumei
authors.initials: S
authors.lastname: Ren
authors.forename: Hideaki
authors.initials: H
authors.lastname: Higashi
authors.forename: Huaisheng
authors.initials: H
authors.lastname: Lu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Azuma
authors.forename: Masanori
authors.initials: M
authors.lastname: Hatakeyama
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D005798:Genes, Bacterial; D005822:Genetic Vectors; D016480:Helicobacter pylori / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D014162:Transfection; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D011505:Protein-Tyrosine Kinases; D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases