title: Caspase-1 autoproteolysis is differentially required for NLRP1b and NLRP3 inflammasome function.
abstract: Inflammasomes are caspase-1-activating multiprotein complexes. The mouse nucleotide-binding domain and leucine rich repeat pyrin containing 1b (NLRP1b) inflammasome was identified as the sensor of Bacillus anthracis lethal toxin (LT) in mouse macrophages from sensitive strains such as BALB/c. Upon exposure to LT, the NLRP1b inflammasome activates caspase-1 to produce mature IL-1β and induce pyroptosis. Both processes are believed to depend on autoproteolysed caspase-1. In contrast to human NLRP1, mouse NLRP1b lacks an N-terminal pyrin domain (PYD), indicating that the assembly of the NLRP1b inflammasome does not require the adaptor apoptosis-associated speck-like protein containing a CARD (ASC). LT-induced NLRP1b inflammasome activation was shown to be impaired upon inhibition of potassium efflux, which is known to play a major role in NLRP3 inflammasome formation and ASC dimerization. We investigated whether NLRP3 and/or ASC were required for caspase-1 activation upon LT stimulation in the BALB/c background. The NLRP1b inflammasome activation was assessed in both macrophages and dendritic cells lacking either ASC or NLRP3. Upon LT treatment, the absence of NLRP3 did not alter the NLRP1b inflammasome activity. Surprisingly, the absence of ASC resulted in IL-1β cleavage and pyroptosis, despite the absence of caspase-1 autoprocessing activity. By reconstituting caspase-1/caspase-11(-/-) cells with a noncleavable or catalytically inactive mutant version of caspase-1, we directly demonstrated that noncleavable caspase-1 is fully active in response to the NLRP1b activator LT, whereas it is nonfunctional in response to the NLRP3 activator nigericin. Taken together, these results establish variable requirements for caspase-1 cleavage depending on the pathogen and the responding NLR.
authors.affiliation: INSERM U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, F-69000 Lyon, France; Université de Lyon, Université Lyon 1, F-69000 Lyon, France; Centre Léon Bérard, F-69008 Lyon, France; and.
authors.forename: Baptiste
authors.initials: B
authors.lastname: Guey
authors.affiliation: INSERM U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, F-69000 Lyon, France; Université de Lyon, Université Lyon 1, F-69000 Lyon, France; Centre Léon Bérard, F-69008 Lyon, France; and.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Bodnar
authors.affiliation: INSERM U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, F-69000 Lyon, France; Université de Lyon, Université Lyon 1, F-69000 Lyon, France; Centre Léon Bérard, F-69008 Lyon, France; and.
authors.forename: Serge N
authors.initials: SN
authors.lastname: Manié
authors.affiliation: Department of Biochemistry, University of Lausanne, CH-1066 Epalinges, Switzerland.
authors.forename: Aubry
authors.initials: A
authors.lastname: Tardivel
authors.affiliation: INSERM U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, F-69000 Lyon, France; Université de Lyon, Université Lyon 1, F-69000 Lyon, France; Centre Léon Bérard, F-69008 Lyon, France; and virginie.petrilli@lyon.unicancer.fr.
authors.forename: Virginie
authors.initials: V
authors.lastname: Petrilli
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D053468:CARD Signaling Adaptor Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D020170:Caspase 1 / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000187:drug effects / Q000378:metabolism; D058847:Inflammasomes / Q000235:genetics / Q000378:metabolism*; D020382:Interleukin-18 / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D009550:Nigericin / Q000494:pharmacology; D059748:Proteolysis
chemical_list: D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D002352:Carrier Proteins; D058847:Inflammasomes; D020382:Interleukin-18; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C509168:Nalp1b protein, mouse; C492716:Nlrp3 protein, mouse; C498534:Pycard protein, mouse; D020170:Caspase 1; D009550:Nigericin
keywords: dendritic cell; interleukin-1beta; lethal toxin; macrophage; pyroptosis