Helicobacter pylori VacA activates the p38/activating transcription factor 2-mediated signal pathway in AZ-521 cells.
Persistent Helicobacter pylori colonization in the stomach induces gastritis and peptic ulcer and interferes with ulcer healing. Most strains of H. pylori produce a cytotoxin, VacA, that induces cytoplasmic vacuolation in epithelial cells with structural and functional changes, leading to gastric injury. VacA is known to cause cell death by mitochondrial damage. We hypothesized that VacA might disrupt other signaling pathways; to that end, we examined the effects of VacA on MAPKs to elucidate their role in the abnormalities seen in VacA-treated cells. VacA stimulated phosphorylation of p38 and Erk1/2, but not JNK, in AZ-521 cells. Both phosphorylation and kinase activation of p38 were maximal 10-30 min after addition of VacA and declined thereafter. Treatment with anti-VacA antibody or the p38 inhibitor SB203580 blocked p38 phosphorylation caused by VacA and inhibited VacA-induced phosphorylation of activating transcription factor 2 (ATF-2), which is implicated in transcriptional control of stress-responsive genes. These data indicate that VacA stimulates a p38/ATF-2-mediated signal pathway. However, 10 microM SB203580, which is sufficient to decrease p38 phosphorylation, did not inhibit VacA-induced cellular vacuolation, decrease in mitochondrial membrane potential, or cytochrome c release from mitochondria. These results suggest that VacA-induced activation of p38/ATF-2-mediated signal pathway is independent of cellular vacuolation, decrease in mitochondrial membrane potential, or cytochrome c release from mitochondria caused by VacA. The cytotoxin may thus act independently on several cellular targets, leading to disruption of signaling, regulatory, and metabolic pathways.
Nakayama
Masaaki
M
Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 8528523, Japan.
Kimura
Miyuki
M
Wada
Akihiro
A
Yahiro
Kinnosuke
K
Ogushi
Ken-ichi
K
Niidome
Takuro
T
Fujikawa
Akihiro
A
Shirasaka
Daisuke
D
Aoyama
Nobuo
N
Kurazono
Hisao
H
Noda
Masaharu
M
Moss
Joel
J
Hirayama
Toshiya
T
D051698:Activating Transcription Factor 2; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016480:Helicobacter pylori / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D008564:Membrane Potentials; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D048051:p38 Mitogen-Activated Protein Kinases
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D001426:Bacterial Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D014157:Transcription Factors; C074689:VacA protein, Helicobacter pylori; D045304:Cytochromes c; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580