Helicobacter pylori vacuolating cytotoxin induces activation of the proapoptotic proteins Bax and Bak, leading to cytochrome c release and cell death, independent of vacuolation

Eiki Yamasaki, Akihiro Wada, Atsushi Kumatori, Ichiro Nakagawa, Junko Funao, Masaaki Nakayama, Junzo Hisatsune, Miyuki Kimura, Joel Moss, Toshiya Hirayama

Research output: Contribution to journalArticle

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Abstract

Helicobacter pylori vacuolating cytotoxin, VacA, which causes vacuolation of gastric epithelial cells and other types of cultured cells, is known to stimulate apoptosis via a mitochondria-dependent pathway. In the present study, we examined the mechanisms of VacA-induced mitochondrial damage. Intracellular VacA localization was monitored by immunostaining and confocal microscopy; in AZ-521 cells in which cytochrome c release was stimulated, most of VacA was localized to vacuoles rather than mitochondria. VacA reduced the membrane potential of isolated mitochondria without inducing cytochrome c release, suggesting that it did not act directly to induce cytochrome c release from mitochondria and that in intact cells, VacA-induced cytochrome c release involved apoptosis-related factor(s), such as a proapoptotic Bcl-2 family protein. In agreement, flow cytometric analyses using antibodies specific for activated Bax revealed that intracellular Bax was activated by VacA in a concentration- and time-dependent manner. Using active form-specific antibodies, we also observed that the Bcl-2 family protein, Bak, was activated. By confocal microscopy, Bax and Bak were activated in AZ-521 cells in which cytochrome c release was induced by VacA. In addition, small interfering RNA-induced silencing of the bax gene resulted in reduction of VacA-stimulated cytochrome c release, consistent with a contribution of VacA-induced Bax activation to cytochrome c release. NH4Cl enhanced both VacA-induced vacuolation and Bax activation, whereas Bax activation was not inhibited by bafilomycin A1, which inhibited vacuolation caused by VacA. These results suggest that VacA acts through different signaling pathways to induce apoptosis via Bax activation, independent of vacuolation.

Original languageEnglish
Pages (from-to)11250-11259
Number of pages10
JournalJournal of Biological Chemistry
Volume281
Issue number16
DOIs
Publication statusPublished - Apr 21 2006

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bcl-2 Homologous Antagonist-Killer Protein
bcl-2-Associated X Protein
Cytotoxins
Cell death
Cytochromes c
Helicobacter pylori
Cell Death
Chemical activation
Mitochondria
Confocal microscopy
Apoptosis
Confocal Microscopy
Antibodies
RNA Interference
Vacuoles
Membrane Potentials
Small Interfering RNA
Cultured Cells
Stomach
Genes

ASJC Scopus subject areas

  • Biochemistry

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Helicobacter pylori vacuolating cytotoxin induces activation of the proapoptotic proteins Bax and Bak, leading to cytochrome c release and cell death, independent of vacuolation. / Yamasaki, Eiki; Wada, Akihiro; Kumatori, Atsushi; Nakagawa, Ichiro; Funao, Junko; Nakayama, Masaaki; Hisatsune, Junzo; Kimura, Miyuki; Moss, Joel; Hirayama, Toshiya.

In: Journal of Biological Chemistry, Vol. 281, No. 16, 21.04.2006, p. 11250-11259.

Research output: Contribution to journalArticle

Yamasaki, Eiki ; Wada, Akihiro ; Kumatori, Atsushi ; Nakagawa, Ichiro ; Funao, Junko ; Nakayama, Masaaki ; Hisatsune, Junzo ; Kimura, Miyuki ; Moss, Joel ; Hirayama, Toshiya. / Helicobacter pylori vacuolating cytotoxin induces activation of the proapoptotic proteins Bax and Bak, leading to cytochrome c release and cell death, independent of vacuolation. In: Journal of Biological Chemistry. 2006 ; Vol. 281, No. 16. pp. 11250-11259.
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AU - Yamasaki, Eiki

AU - Wada, Akihiro

AU - Kumatori, Atsushi

AU - Nakagawa, Ichiro

AU - Funao, Junko

AU - Nakayama, Masaaki

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AU - Moss, Joel

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