title: CA-074Me protection against anthrax lethal toxin.
abstract: Anthrax lethal toxin (LT) activates the NLRP1b (NALP1b) inflammasome and caspase-1 in macrophages from certain inbred mouse strains, but the mechanism by which this occurs is poorly understood. We report here that similar to several NLRP3 (NALP3, cryopyrin)-activating stimuli, LT activation of the NLRP1b inflammasome involves lysosomal membrane permeabilization (LMP) and subsequent cytoplasmic cathepsin B activity. CA-074Me, a potent cathepsin B inhibitor, protects LT-sensitive macrophages from cell death and prevents the activation of caspase-1. RNA interference knockdown of cathepsin B expression, however, cannot prevent LT-mediated cell death, suggesting that CA-074Me may also act on other cellular proteases released during LMP. CA-074Me appears to function downstream of LT translocation to the cytosol (as assessed by mitogen-activated protein kinase kinase cleavage), K(+) effluxes, and proteasome activity. The initial increase in cytoplasmic activity of cathepsin B occurs at the same time or shortly before caspase-1 activation but precedes a larger-scale lysosomal destabilization correlated closely with cytolysis. We present results suggesting that LMP may be involved in the activation of the NLRP1b inflammasome.
authors.affiliation: Bacterial Toxins and Therapeutics Section, Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Zachary L
authors.initials: ZL
authors.lastname: Newman
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla
authors.forename: Mahtab
authors.initials: M
authors.lastname: Moayeri
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D000881:Anthrax / Q000517:prevention & control*; D000942:Antigens, Bacterial; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors*; D020170:Caspase 1 / Q000378:metabolism; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004151:Dipeptides / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D055785:Gene Knockdown Techniques; D007425:Intracellular Membranes / Q000187:drug effects; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D010539:Permeability / Q000187:drug effects
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000942:Antigens, Bacterial; D051017:Apoptosis Regulatory Proteins; D001427:Bacterial Toxins; C400541:CA 074 methyl ester; D004151:Dipeptides; D004791:Enzyme Inhibitors; C529636:NALP1 protein, mouse; C030325:anthrax toxin; D002401:Cathepsin B; D020170:Caspase 1