title: Calyculin A sensitive protein phosphatase is required for Bacillus anthracis lethal toxin induced cytotoxicity.
abstract: Previous studies have shown that the Bacillus anthracis lethal toxin can induce both necrosis and apoptosis in mouse macrophage-like J774A.1 cells depending on both the toxin concentration and the phosphatase activity. In this study several protein kinase or phosphatase inhibitors were employed to evaluate the hypothesis that the lethal toxin induces cell death via protein phosphorylation processes. Pretreatment with a serine/threonine phosphatase inhibitor Calyculin A (300 nM) could inhibit about 78% of cell death induced by the lethal toxin, whereas inhibitors of kinases, such as H7, HA, Sphingosine, and Genestein, but other inhibitors of phosphatases, such as Okadaic acid, Tautomycin, and Cyclosporin A, did not. In addition, recent reports have demonstrated that the MEK1 protein may serve as a proteolytic target within its N-terminus for lethal factor cleavage. In this study, Calyculin A is shown to enhance the phosphorylation of the MEK1 protein. This prevents the cleavage of the MEK1 by lethal factor. These results suggest that a putative Calyculin A-sensitive protein phosphatase is involved in anthrax toxin induced cytotoxicity and that the blocking effect of Calyculin A on lethal factor cytotoxicity may be mediated through the MEK signaling pathway.
authors.affiliation: Institute of Preventive Medicine, National Defense Medical Center, P.O. Box 90048-700, Taipei, Taiwan, ROC.
authors.forename: Jyh-Hwa
authors.initials: JH
authors.lastname: Kau
authors.forename: Ching-Gong
authors.initials: CG
authors.lastname: Lin
authors.forename: Hsin-Hsien
authors.initials: HH
authors.lastname: Huang
authors.forename: Hui-Ling
authors.initials: HL
authors.lastname: Hsu
authors.forename: Kuo-Ching
authors.initials: KC
authors.lastname: Chen
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Wu
authors.forename: Hung-Chi
authors.initials: HC
authors.lastname: Lin
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D000942:Antigens, Bacterial; D001408:Bacillus anthracis / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity; D001427:Bacterial Toxins / Q000378:metabolism* / Q000633:toxicity; D015153:Blotting, Western; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology; D048728:MAP Kinase Kinase Kinase 1; D008387:Marine Toxins; D051379:Mice; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011714:Pyrans; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000494:pharmacology; D013141:Spiro Compounds
chemical_list: D000935:Antifungal Agents; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D011714:Pyrans; D013141:Spiro Compounds; C030325:anthrax toxin; C053079:tautomycin; D019319:Okadaic Acid; C059041:calyculin A; D016572:Cyclosporine; D019833:Genistein; D017346:Protein Serine-Threonine Kinases; D048728:MAP Kinase Kinase Kinase 1; C482578:Map3k1 protein, mouse; D010749:Phosphoprotein Phosphatases; D013110:Sphingosine