title: Helicobacter pylori-induced loss of survivin and gastric cell viability is attributable to secreted bacterial gamma-glutamyl transpeptidase activity.
abstract: Helicobacter pylori is the etiologic agent of a series of gastric pathologies that may culminate in the development of gastric adenocarcinoma. An initial step in this process is the loss of glandular structures in the gastric mucosa, presumably as the consequence of increased apoptosis and reduced cellular regeneration, which may be attributed to the combination of several bacterial and host factors and to an unfavorable proinflammatory environment. In a previous study, we showed that survivin, a member of the inhibitor of apoptosis protein family, is expressed in the normal human gastric mucosa and that its levels decrease in the mucosa of infected patients and in gastric cells exposed in culture to the bacteria, coincident with increased cell death in the latter case. We investigated the bacterial factors responsible for loss of survivin in gastric cells exposed to H. pylori. The results of this study indicated that the loss of survivin due to H. pylori infection involves proteasome-mediated degradation of the protein. Studies with isogenic mutants deficient in either CagA, VacA, lipopolysaccharide, or gamma-glutamyl transpeptidase (GGT) implicated the latter in H. pylori-induced loss of survivin and cell viability. Moreover, experiments with the GGT inhibitor 6-diazo-5-oxo-l-norleucine and purified recombinant GGT protein indicated that secreted bacterial GGT activity was required and sufficient to induce these effects.
authors.affiliation: Laboratory of Cellular Communication, Center for Molecular Studies of the Cell, Universidad de Chile, Santiago, Chile.
authors.forename: Manuel
authors.initials: M
authors.lastname: Valenzuela
authors.forename: Denisse
authors.initials: D
authors.lastname: Bravo
authors.forename: Jimena
authors.initials: J
authors.lastname: Canales
authors.forename: Carlos
authors.initials: C
authors.lastname: Sanhueza
authors.forename: Natalia
authors.initials: N
authors.lastname: Díaz
authors.forename: Oscar
authors.initials: O
authors.lastname: Almarza
authors.forename: Héctor
authors.initials: H
authors.lastname: Toledo
authors.forename: Andrew F G
authors.initials: AF
authors.lastname: Quest
mesh_terms: D002460:Cell Line; D017353:Gene Deletion; D016481:Helicobacter Infections / Q000382:microbiology* / Q000473:pathology*; D016480:Helicobacter pylori / Q000201:enzymology* / Q000472:pathogenicity*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D050296:Microbial Viability; D000077022:Survivin; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000235:genetics / Q000378:metabolism*
chemical_list: C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D000077022:Survivin; D037521:Virulence Factors; D005723:gamma-Glutamyltransferase
keywords: CagA; Helicobacter pylori; LPS; VacA; apoptosis; gamma glutamyl transpeptidase; gastric cancer; infection; survivin