title: NLRP3 inflammasome activation downstream of cytoplasmic LPS recognition by both caspase-4 and caspase-5.
abstract: Humans encode two inflammatory caspases that detect cytoplasmic LPS, caspase-4 and caspase-5. When activated, these trigger pyroptotic cell death and caspase-1-dependent IL-1β production; however the mechanism underlying this process is not yet confirmed. We now show that a specific NLRP3 inhibitor, MCC950, prevents caspase-4/5-dependent IL-1β production elicited by transfected LPS. Given that both caspase-4 and caspase-5 can detect cytoplasmic LPS, it is possible that these proteins exhibit some degree of redundancy. Therefore, we generated human monocytic cell lines in which caspase-4 and caspase-5 were genetically deleted either individually or together. We found that the deletion of caspase-4 suppressed cell death and IL-1β production following transfection of LPS into the cytoplasm, or in response to infection with Salmonella typhimurium. Although deletion of caspase-5 did not confer protection against transfected LPS, cell death and IL-1β production were reduced after infection with Salmonella. Furthermore, double deletion of caspase-4 and caspase-5 had a synergistic effect in the context of Salmonella infection. Our results identify the NLRP3 inflammasome as the specific platform for IL-1β maturation, downstream of cytoplasmic LPS detection by caspase-4/5. We also show that both caspase-4 and caspase-5 are functionally important for appropriate responses to intracellular Gram-negative bacteria.
authors.affiliation: Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Australia.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Baker
authors.affiliation: Cell Biology and Molecular Medicine Division, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Dave
authors.initials: D
authors.lastname: Boucher
authors.affiliation: Cell Biology and Molecular Medicine Division, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Damien
authors.initials: D
authors.lastname: Bierschenk
authors.affiliation: The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.|Department of Microbiology and Immunology, The University of Melbourne, Parkville, Australia.
authors.forename: Christina
authors.initials: C
authors.lastname: Tebartz
authors.affiliation: The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.|Department of Microbiology and Immunology, The University of Melbourne, Parkville, Australia.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Whitney
authors.affiliation: Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Australia.
authors.forename: Damian B
authors.initials: DB
authors.lastname: D'Silva
authors.affiliation: Department of Medical Biology, The University of Melbourne, Parkville, Australia.|Cell Signaling and Cell Death Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Tanzer
authors.affiliation: Cell Biology and Molecular Medicine Division, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Monteleone
authors.affiliation: Cell Biology and Molecular Medicine Division, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Avril A B
authors.initials: AA
authors.lastname: Robertson
authors.affiliation: Cell Biology and Molecular Medicine Division, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Cooper
authors.affiliation: Department of Medical Biology, The University of Melbourne, Parkville, Australia.|Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
authors.forename: Silvia
authors.initials: S
authors.lastname: Alvarez-Diaz
authors.affiliation: Department of Medical Biology, The University of Melbourne, Parkville, Australia.|Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.
authors.forename: Marco J
authors.initials: MJ
authors.lastname: Herold
authors.affiliation: The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.|Department of Microbiology and Immunology, The University of Melbourne, Parkville, Australia.
authors.forename: Sammy
authors.initials: S
authors.lastname: Bedoui
authors.affiliation: Cell Biology and Molecular Medicine Division, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Kate
authors.initials: K
authors.lastname: Schroder
authors.affiliation: Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia.|Department of Medical Biology, The University of Melbourne, Parkville, Australia.
authors.forename: Seth L
authors.initials: SL
authors.lastname: Masters
mesh_terms: D002352:Carrier Proteins / Q000276:immunology*; D020169:Caspases / Q000276:immunology*; D053471:Caspases, Initiator / Q000276:immunology*; D045744:Cell Line, Tumor; D006801:Humans; D053583:Interleukin-1beta / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology*; D009000:Monocytes / Q000276:immunology*; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D012480:Salmonella Infections / Q000276:immunology*; D012486:Salmonella typhimurium / Q000276:immunology*
chemical_list: D002352:Carrier Proteins; C508585:IL1B protein, human; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; C093516:CASP4 protein, human; C099217:CASP5 protein, human; D020169:Caspases; D053471:Caspases, Initiator
keywords: Caspase-4; Caspase-5; LPS; NLRP3 inflammasome; Pyroptosis