title: Helicobacter pylori VacA induces apoptosis by accumulation of connexin 43 in autophagic vesicles via a Rac1/ERK-dependent pathway.
abstract: Helicobacter pylori (H. pylori) produces vacuolating cytotoxin (VacA), a potent protein toxin, which is associated with gastric inflammation and ulceration. Recent studies demonstrated that connexins (Cxs), which are responsible for intracellular communication at gap junctions (GJs) as well as cell homeostasis, participate in VacA-induced cell death. We now demonstrate in AZ-521 cells that VacA increased cytoplasmic Cx43, accompanied by LC3-II generation in a time- and dose-dependent manner without induction of Cx43 mRNA expression. Inhibition of VacA-induced Rac1 activity prevented ERK phosphorylation and the increase in Cx43. Suppression of ERK activity and addition of N-acetyl-cysteine inhibited VacA-dependent increase in Cx43 and LC3-II. DIDS, an anion-selective inhibitor, suppressed VacA-dependent increase in Cx43, suggesting that VacA channel activity was involved in this pathway. By confocal microscopy, Cx43 increased by VacA was predominately localized in cholesterol-rich, detergent-resistant membranes including GJs, and a fraction of Cx43 was incorporated in endocytotic vesicles and autophagolysosomes. Accumulation of Cx43 was also observed in gastric mucosa from H. pylori-infected patients compared with healthy controls, suggesting that the pathogen caused a similar effect in vivo. Our findings show that VacA-mediated effects on autophagy inhibits turnover of Cx43, resulting in increased levels in the cytoplasm, leading eventually to apoptotic cell death.
authors.affiliation: Department of Molecular Infectiology, Graduate School of Medicine, Chiba University , Chiba 260-8670, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yahiro
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, 1-7-1 Sakamoto , Nagasaki, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Akazawa
authors.affiliation: Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University , Nagasaki 852-8523, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine , 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 852-8523, Japan; Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima 734-8551, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Hisatune
authors.affiliation: Division of Medicine and Clinical Science, Department of Multidisciplinary Internal Medicine, Tottori University School of Medicine , Tottori 683-8503, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Isomoto
authors.affiliation: University Paris Diderot, Sorbonne Paris Cité, Epigenetics and Cell Fate, UMR 7216 CNRS , Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Sap
authors.affiliation: Department of Molecular Infectiology, Graduate School of Medicine, Chiba University , Chiba 260-8670, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Noda
authors.affiliation: Cardiovascular and Pulmonary Branch, NHLBI, National Institutes of Health , Bethesda, Maryland 20892, USA.
authors.forename: J
authors.initials: J
authors.lastname: Moss
authors.affiliation: Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University , Nagasaki 852-8523, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hirayama