title: A RIPK3-caspase 8 complex mediates atypical pro-IL-1β processing.
abstract: Caspase 8, the initiator caspase for death receptor-induced apoptosis, functions as a negative regulator of receptor interacting protein kinase 3 (RIPK3), an essential factor for TNF-, TLR3-, and TLR4-induced necroptosis. In certain situations, caspase 8 can also participate in pro-IL-1β processing. However, the biochemical complex that mediates caspase 8-mediated processing is not defined. In this study, we show that RIPK3 is crucial for caspase 1- and caspase 8-mediated pro-IL-1β and pro-IL-18 processing in bone marrow-derived dendritic cells (BMDCs) in response to LPS stimulation. Caspase 8-mediated pro-IL-1β processing requires intact RIPK1, RIPK3, TRIF, and FADD. In response to LPS, a complex that contains RIPK1, RIPK3, FADD, and caspase 8 is formed. Surprisingly, RIPK3-specific kinase inhibitors strongly enhanced caspase 8 activation and pro-IL-1β processing in LPS-stimulated BMDCs. However, studies in BMDCs expressing the kinase-inactive RIPK3-K51A mutant or RIPK1-K45A mutant showed that the kinase activity of neither RIPK1 nor RIPK3 is required for LPS-induced caspase 8 activation and IL-1β secretion. Hence, RIPK3 is an unexpected positive regulator of caspase 8 activity that promotes IL-1β maturation in BMDCs.
authors.affiliation: Department of Pathology, Program in Immunology & Microbiology, University of Massachusetts Medical School, Worcester, MA 01655; and.
authors.forename: Kenta
authors.initials: K
authors.lastname: Moriwaki
authors.affiliation: Pattern Recognition Receptor Discovery Performance Unit, Immuno-Inflammation Therapeutic Area, GlaxoSmithKline, Collegeville, PA 19422.
authors.forename: John
authors.initials: J
authors.lastname: Bertin
authors.affiliation: Pattern Recognition Receptor Discovery Performance Unit, Immuno-Inflammation Therapeutic Area, GlaxoSmithKline, Collegeville, PA 19422.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Gough
authors.affiliation: Department of Pathology, Program in Immunology & Microbiology, University of Massachusetts Medical School, Worcester, MA 01655; and francis.chan@umassmed.edu.
authors.forename: Francis Ka-Ming
authors.initials: FK
authors.lastname: Chan
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000276:immunology; D053181:Caspase 8 / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology*; D004789:Enzyme Activation / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D055879:Gene Knock-In Techniques; D047468:Immunoprecipitation; D007249:Inflammation / Q000276:immunology; D053583:Interleukin-1beta / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000276:immunology*; D014162:Transfection
chemical_list: D053583:Interleukin-1beta; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C485615:Ripk3 protein, mouse; D053181:Caspase 8