PMID:16436379

Citation	Yamasaki, E, Wada, A, Kumatori, A, Nakagawa, I, Funao, J, Nakayama, M, Hisatsune, J, Kimura, M, Moss, J and Hirayama, T (2006) Helicobacter pylori vacuolating cytotoxin induces activation of the proapoptotic proteins Bax and Bak, leading to cytochrome c release and cell death, independent of vacuolation. J. Biol. Chem. 281:11250-9
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 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.
Links	PubMed Online version:10.1074/jbc.M509404200
Keywords	Apoptosis; Bacterial Proteins/chemistry; Bacterial Proteins/physiology; Cell Death; Cell Line; Cell Line, Tumor; Cytochromes c/metabolism; Flow Cytometry; HeLa Cells; Helicobacter pylori/metabolism; Humans; Immunohistochemistry; Macrolides/pharmacology; Microscopy, Confocal; Microscopy, Fluorescence; Mitochondria/metabolism; Protons; RNA, Small Interfering/metabolism; Time Factors; Transfection; Vacuoles/metabolism; bcl-2 Homologous Antagonist-Killer Protein/metabolism; bcl-2-Associated X Protein/metabolism
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HELPX:C7F7V2		GO:0005773: vacuole	ECO:0000314:		C		Using immunocytochemistry and confocal analysis, figure 2 shows that VacA is localized to vacuoles, but not to mitochondria.	complete CACAO 3791
HELPX:C7F7V2		GO:0009405: pathogenesis	ECO:0000314:		P		toxin molecule that attaches to the surface and gets inserted into the cell where it accumulates and effects the normal trafficking of the cells resulting in the death of that cell	complete CACAO 9665

References

See Help:References for how to manage references in GONUTS.