title: Complement pathway amplifies caspase-11-dependent cell death and endotoxin-induced sepsis severity.
abstract: Cell death and release of proinflammatory mediators contribute to mortality during sepsis. Specifically, caspase-11-dependent cell death contributes to pathology and decreases in survival time in sepsis models. Priming of the host cell, through TLR4 and interferon receptors, induces caspase-11 expression, and cytosolic LPS directly stimulates caspase-11 activation, promoting the release of proinflammatory cytokines through pyroptosis and caspase-1 activation. Using a CRISPR-Cas9-mediated genome-wide screen, we identified novel mediators of caspase-11-dependent cell death. We found a complement-related peptidase, carboxypeptidase B1 (Cpb1), to be required for caspase-11 gene expression and subsequent caspase-11-dependent cell death. Cpb1 modifies a cleavage product of C3, which binds to and activates C3aR, and then modulates innate immune signaling. We find the Cpb1-C3-C3aR pathway induces caspase-11 expression through amplification of MAPK activity downstream of TLR4 and Ifnar activation, and mediates severity of LPS-induced sepsis (endotoxemia) and disease outcome in mice. We show C3aR is required for up-regulation of caspase-11 orthologues, caspase-4 and -5, in primary human macrophages during inflammation and that c3aR1 and caspase-5 transcripts are highly expressed in patients with severe sepsis; thus, suggesting that these pathways are important in human sepsis. Our results highlight a novel role for complement and the Cpb1-C3-C3aR pathway in proinflammatory signaling, caspase-11 cell death, and sepsis severity.
authors.affiliation: Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305.
authors.forename: Brooke A
authors.identifier: 0000-0002-6409-4750
authors.initials: BA
authors.lastname: Napier
authors.affiliation: Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305.
authors.forename: Sky W
authors.initials: SW
authors.lastname: Brubaker
authors.affiliation: Division of Biomedical Informatics Research, Stanford University School of Medicine, Stanford University, Stanford, CA 94305.|Institute for Immunity, Transplantation, and Infection, Stanford University, Stanford, CA 94305.
authors.forename: Timothy E
authors.identifier: 0000-0002-3596-1093
authors.initials: TE
authors.lastname: Sweeney
authors.affiliation: Department of Biology, Middlebury College, Middlebury, VT 05753.
authors.forename: Patrick
authors.identifier: 0000-0002-0847-7255
authors.initials: P
authors.lastname: Monette
authors.affiliation: Digital Team, Blue Bottle Coffee, Oakland, CA, 94607.
authors.forename: Greggory H
authors.identifier: 0000-0001-6058-4624
authors.initials: GH
authors.lastname: Rothmeier
authors.affiliation: Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305.
authors.forename: Nina A
authors.initials: NA
authors.lastname: Gertsvolf
authors.affiliation: Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305.
authors.forename: Andreas
authors.initials: A
authors.lastname: Puschnik
authors.affiliation: Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305.
authors.forename: Jan E
authors.initials: JE
authors.lastname: Carette
authors.affiliation: Division of Biomedical Informatics Research, Stanford University School of Medicine, Stanford University, Stanford, CA 94305.|Institute for Immunity, Transplantation, and Infection, Stanford University, Stanford, CA 94305.
authors.forename: Purvesh
authors.identifier: 0000-0002-4143-4708
authors.initials: P
authors.lastname: Khatri
authors.affiliation: Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305 dmonack@stanford.edu.
authors.forename: Denise M
authors.identifier: 0000-0003-3804-2209
authors.initials: DM
authors.lastname: Monack
mesh_terms: D000818:Animals; D064113:CRISPR-Cas Systems; D043424:Carboxypeptidase B / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D053471:Caspases, Initiator; D016923:Cell Death; D003176:Complement C3 / Q000378:metabolism; D003165:Complement System Proteins / Q000378:metabolism*; D019446:Endotoxemia / Q000097:blood / Q000473:pathology; D004731:Endotoxins; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000473:pathology; D018836:Inflammation Mediators / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008954:Models, Biological; D010766:Phosphorylation; D000067996:RAW 264.7 Cells; D011951:Receptors, Complement / Q000378:metabolism; D017471:Receptors, Interferon / Q000378:metabolism; D012475:Salmonella / Q000502:physiology; D018805:Sepsis / Q000201:enzymology* / Q000473:pathology*; D012760:Shigella / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D003176:Complement C3; D004731:Endotoxins; D018836:Inflammation Mediators; D011951:Receptors, Complement; D017471:Receptors, Interferon; D051197:Toll-Like Receptor 4; C085567:complement C3a receptor; D003165:Complement System Proteins; D048051:p38 Mitogen-Activated Protein Kinases; D043424:Carboxypeptidase B; C101136:Casp4 protein, mouse; D020169:Caspases; D053471:Caspases, Initiator