title: Helicobacter pylori VacA-induced inhibition of GSK3 through the PI3K/Akt signaling pathway.
abstract: Helicobacter pylori VacA toxin contributes to the pathogenesis and severity of gastric injury. We found that incubation of AZ-521 cells with VacA resulted in phosphorylation of protein kinase B (Akt) and glycogen synthase kinase-3beta (GSK3beta) through a PI3K-dependent pathway. Following phosphorylation and inhibition of GSK3beta,beta-catenin was released from a GSK3beta/beta-catenin complex, with subsequent nuclear translocation. Methyl-beta-cyclodextrin (MCD) and phosphatidylinositol-specific phospholipase C (PI-PLC), but not 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) and bafilomycin A1, inhibited VacA-induced phosphorylation of Akt, indicating that it does not require VacA internalization and is independent of vacuolation. VacA treatment of AZ-521 cells transfected with TOPtkLuciferase reporter plasmid or control FOPtkLucifease reporter plasmid resulted in activation of TOPtkLuciferase, but not FOPtkLucifease. In addition, VacA transactivated the beta-catenin-dependent cyclin D1 promoter in a luciferase reporter assay. Infection of AZ-521 cells by a vacA mutant strain of H. pylori failed to induce phosphorylation of Akt and GSK3beta, or release of beta-catenin from a GSK3beta/beta-catenin complex. Taken together, these results support the conclusion that VacA activates the PI3K/Akt signaling pathway, resulting in phosphorylation and inhibition of GSK3beta, and subsequent translocation ofbeta-catenin to the nucleus, consistent with effects of VacA on beta-catenin-regulated transcriptional activity. These data introduce the possibility that Wnt-dependent signaling might play a role in the pathogenesis of H. pylori infection, including the development of gastric cancer.
authors.affiliation: Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakayama
authors.forename: Junzo
authors.initials: J
authors.lastname: Hisatsune
authors.forename: Eiki
authors.initials: E
authors.lastname: Yamasaki
authors.forename: Hajime
authors.initials: H
authors.lastname: Isomoto
authors.forename: Hisao
authors.initials: H
authors.lastname: Kurazono
authors.forename: Masanori
authors.initials: M
authors.lastname: Hatakeyama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Azuma
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Yamaoka
authors.forename: Kinnosuke
authors.initials: K
authors.lastname: Yahiro
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.forename: Toshiya
authors.initials: T
authors.lastname: Hirayama
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D001426:Bacterial Proteins / Q000633:toxicity*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D016481:Helicobacter Infections / Q000201:enzymology* / Q000235:genetics; D016480:Helicobacter pylori; D006801:Humans; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D054799:Phospholipase C beta / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013274:Stomach Neoplasms / Q000201:enzymology / Q000235:genetics / Q000382:microbiology; D015533:Transcriptional Activation / Q000187:drug effects; D051153:Wnt Proteins; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D019938:Cyclin D1; D004791:Enzyme Inhibitors; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D019869:Phosphatidylinositol 3-Kinases; D054799:Phospholipase C beta; D051057:Proto-Oncogene Proteins c-akt; D051153:Wnt Proteins; D051176:beta Catenin; C530104:CCND1 protein, human; C074689:VacA protein, Helicobacter pylori; C000605506:GSK3B protein, human