HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 281, Issue 16, 11250-11259, April 21, 2006

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 281/16/11250    most recent M509404200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Yamasaki, E. Articles by Hirayama, T. Search for Related Content PubMed PubMed Citation Articles by Yamasaki, E. Articles by Hirayama, T. Social Bookmarking                      What's this?

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 Wada¹, Atsushi Kumatori^¶, Ichiro Nakagawa^||, Junko Funao^||, Masaaki Nakayama, Junzo Hisatsune, Miyuki Kimura^**, Joel Moss², and Toshiya Hirayama

From the PRESTO, Japan Science and Technology Corporation, Saitama 332-0012, Japan, the Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 852-8523, Japan, the ^¶Division of Medical Science, Department of Disaster Prevention System, Faculty of Risk and Crisis Management, Chiba Institute of Science, Choshi, Chiba 288-0025, Japan, the ^||Department of Oral and Molecular Microbiology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita-Osaka 565-0871, Japan, the ^**Department of Medical Technology, Faculty of Health Sciences, Okayama University Medical School, Okayama 700-8558, Japan, and the Pulmonary-Critical Care Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1590

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 cyto-metric 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 cyto-chrome 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.

Received for publication, August 25, 2005 , and in revised form, December 29, 2005.

^* This work was supported by grants-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan and from Institute of Tropical Medicine, Nagasaki University. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental material.

² Supported by the Intramural Research Program, NHLBI, National Institutes of Health.

¹ To whom correspondence should be addressed: Dept. of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan. Tel.: 81-95-849-7833; Fax: 81-95-849-7805; E-mail: a-wada{at}net.nagasaki-u.ac.jp.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				M. Nakayama, J. Hisatsune, E. Yamasaki, H. Isomoto, H. Kurazono, M. Hatakeyama, T. Azuma, Y. Yamaoka, K. Yahiro, J. Moss, et al. Helicobacter pylori VacA-induced Inhibition of GSK3 through the PI3K/Akt Signaling Pathway J. Biol. Chem., January 16, 2009; 284(3): 1612 - 1619. [Abstract] [Full Text] [PDF]

				J. Hisatsune, M. Nakayama, H. Isomoto, H. Kurazono, N. Mukaida, A. K. Mukhopadhyay, T. Azuma, Y. Yamaoka, J. Sap, E. Yamasaki, et al. Molecular Characterization of Helicobacter pylori VacA Induction of IL-8 in U937 Cells Reveals a Prominent Role for p38MAPK in Activating Transcription Factor-2, cAMP Response Element Binding Protein, and NF-{kappa}B Activation J. Immunol., April 1, 2008; 180(7): 5017 - 5027. [Abstract] [Full Text] [PDF]

				M.-R. Ki, H.-R. Lee, M.-J. Goo, I.-H. Hong, S.-H. Do, D.-H. Jeong, H.-J. Yang, D.-W. Yuan, J.-K. Park, and K.-S. Jeong Differential regulation of ERK1/2 and p38 MAP kinases in VacA-induced apoptosis of gastric epithelial cells Am J Physiol Gastrointest Liver Physiol, March 1, 2008; 294(3): G635 - G647. [Abstract] [Full Text] [PDF]

				J. Hisatsune, E. Yamasaki, M. Nakayama, D. Shirasaka, H. Kurazono, Y. Katagata, H. Inoue, J. Han, J. Sap, K. Yahiro, et al. Helicobacter pylori VacA Enhances Prostaglandin E2 Production through Induction of Cyclooxygenase 2 Expression via a p38 Mitogen-Activated Protein Kinase/Activating Transcription Factor 2 Cascade in AZ-521 Cells Infect. Immun., September 1, 2007; 75(9): 4472 - 4481. [Abstract] [Full Text] [PDF]

				J. M. Kim, J. S. Kim, J. Y. Lee, Y.-J. Kim, H.-J. Youn, I. Y. Kim, Y. J. Chee, Y.-K. Oh, N. Kim, H. C. Jung, et al. Vacuolating Cytotoxin in Helicobacter pylori Water-Soluble Proteins Upregulates Chemokine Expression in Human Eosinophils via Ca2+ Influx, Mitochondrial Reactive Oxygen Intermediates, and NF-{kappa}B Activation Infect. Immun., July 1, 2007; 75(7): 3373 - 3381. [Abstract] [Full Text] [PDF]

				G. Kroemer, L. Galluzzi, and C. Brenner Mitochondrial Membrane Permeabilization in Cell Death Physiol Rev, January 1, 2007; 87(1): 99 - 163. [Abstract] [Full Text] [PDF]

				M. Nakayama, J. Hisatsune, E. Yamasaki, Y. Nishi, A. Wada, H. Kurazono, J. Sap, K. Yahiro, J. Moss, and T. Hirayama Clustering of Helicobacter pylori VacA in Lipid Rafts, Mediated by Its Receptor, Receptor-Like Protein Tyrosine Phosphatase {beta}, Is Required for Intoxication in AZ-521 Cells Infect. Immun., December 1, 2006; 74(12): 6571 - 6580. [Abstract] [Full Text] [PDF]