title: Inflammasome priming by lipopolysaccharide is dependent upon ERK signaling and proteasome function.
abstract: Caspase-1 activation is a central event in innate immune responses to many pathogenic infections and tissue damage. The NLRP3 inflammasome, a multiprotein scaffolding complex that assembles in response to two distinct steps, priming and activation, is required for caspase-1 activation. However, the detailed mechanisms of these steps remain poorly characterized. To investigate the process of LPS-mediated NLRP3 inflammasome priming, we used constitutively present pro-IL-18 as the caspase-1-specific substrate to allow study of the early events. We analyzed human monocyte caspase-1 activity in response to LPS priming, followed by activation with ATP. Within minutes of endotoxin priming, the NLRP3 inflammasome is licensed for ATP-induced release of processed IL-18, apoptosis-associated speck-forming complex containing CARD, and active caspase-1, independent of new mRNA or protein synthesis. Moreover, extracellular signal-regulated kinase 1 (ERK1) phosphorylation is central to the priming process. ERK inhibition and small interfering RNA-mediated ERK1 knockdown profoundly impair priming. In addition, proteasome inhibition prevents ERK phosphorylation and blocks priming. Scavenging reactive oxygen species with diphenylene iodonium also blocks both priming and ERK phosphorylation. These findings suggest that ERK1-mediated posttranslational modifications license the NLRP3 inflammasome to respond to the second signal ATP by inducing posttranslational events that are independent of new production of pro-IL-1β and NOD-like receptor components.
authors.affiliation: Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210;
authors.forename: Mohammed G
authors.initials: MG
authors.lastname: Ghonime
authors.forename: Obada R
authors.initials: OR
authors.lastname: Shamaa
authors.forename: Srabani
authors.initials: S
authors.lastname: Das
authors.forename: Ramadan A
authors.initials: RA
authors.lastname: Eldomany
authors.forename: Teresa
authors.initials: T
authors.lastname: Fernandes-Alnemri
authors.forename: Emad S
authors.initials: ES
authors.lastname: Alnemri
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Gavrilin
authors.forename: Mark D
authors.initials: MD
authors.lastname: Wewers
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D020170:Caspase 1 / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007113:Immunity, Innate; D058847:Inflammasomes; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020382:Interleukin-18 / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D016877:Oxidants / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D058847:Inflammasomes; D020382:Interleukin-18; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D016877:Oxidants; D047428:Protein Kinase Inhibitors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020170:Caspase 1; D046988:Proteasome Endopeptidase Complex