title: Enzymatically Inactive Procaspase 1 stabilizes the ASC Pyroptosome and Supports Pyroptosome Spreading during Cell Division.
abstract: Caspase-1 is a key player during the initiation of pro-inflammatory innate immune responses, activating pro-IL-1β in so-called inflammasomes. A subset of patients with recurrent febrile episodes and systemic inflammation of unknown origin harbor mutations in CASP1 encoding caspase-1. CASP1 variants result in reduced enzymatic activity of caspase-1 and impaired IL-1β secretion. The apparent paradox of reduced IL-1β secretion but systemic inflammation led to the hypothesis that CASP1 mutations may result in variable protein interaction clusters, thus activating alternative signaling pathways. To test this hypothesis, we established and characterized an in vitro system of transduced immortalized murine macrophages expressing either WT or enzymatically inactive (p.C284A) procaspase-1 fusion reporter proteins. Macrophages with variant p.C284A caspase-1 did not secrete IL-1β and exhibited reduced inflammatory cell death, referred to as pyroptosis. Caspase-1 and apoptosis-associated speck-like protein containing a CARD (ASC) formed cytosolic macromolecular complexes (so-called pyroptosomes) that were significantly increased in number and size in cells carrying the p.C284A caspase-1 variant compared with WT caspase-1. Furthermore, enzymatically inactive caspase-1 interacted with ASC longer and with increased intensity compared with WT caspase-1. Applying live cell imaging, we documented for the first time that pyroptosomes containing enzymatically inactive variant p.C284A caspase-1 spread during cell division. In conclusion, variant p.C284A caspase-1 stabilizes pyroptosome formation, potentially enhancing inflammation by two IL-1β-independent mechanisms: pyroptosomes convey an enhanced inflammatory stimulus through the recruitment of additional proteins (such as RIP2, receptor interacting protein kinase 2), which is further amplified through pyroptosome and cell division.
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and.
authors.forename: Robert
authors.initials: R
authors.lastname: Stein
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and.
authors.forename: Franz
authors.initials: F
authors.lastname: Kapplusch
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and.
authors.forename: Michael Christian
authors.initials: MC
authors.lastname: Heymann
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and.
authors.forename: Susanne
authors.initials: S
authors.lastname: Russ
authors.affiliation: Biotechnology Center, Technische Universität Dresden, 01307 Dresden, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Staroske
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and.
authors.forename: Christian Michael
authors.initials: CM
authors.lastname: Hedrich
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and.
authors.forename: Angela
authors.initials: A
authors.lastname: Rösen-Wolff
authors.affiliation: From the Department of Pediatrics, Medizinische Fakultät Carl Gustav Carus, and sigrun.hofmann@uniklinikum-dresden.de.
authors.forename: Sigrun Ruth
authors.initials: SR
authors.lastname: Hofmann
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D020170:Caspase 1 / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D002461:Cell Line, Transformed; D006801:Humans; D058847:Inflammasomes / Q000235:genetics / Q000378:metabolism*; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000201:enzymology*; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C587672:IL1B protein, mouse; D058847:Inflammasomes; D053583:Interleukin-1beta; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C506255:Ripk2 protein, mouse; D020170:Caspase 1
keywords: ASC; IL-1; IL-1β; NLRP3; apoptosis-associated speck-like protein containing a CARD; caspase 1 (CASP1); imaging; inflammasome; interleukin 1-converting enzyme; pyroptosome