title: ASC filament formation serves as a signal amplification mechanism for inflammasomes.
abstract: A hallmark of inflammasome activation is the ASC speck, a micrometre-sized structure formed by the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD), which consists of a pyrin domain (PYD) and a caspase recruitment domain (CARD). Here we show that assembly of the ASC speck involves oligomerization of ASC(PYD) into filaments and cross-linking of these filaments by ASC(CARD). ASC mutants with a non-functional CARD only assemble filaments but not specks, and moreover disrupt endogenous specks in primary macrophages. Systematic site-directed mutagenesis of ASC(PYD) is used to identify oligomerization-deficient ASC mutants and demonstrate that ASC speck formation is required for efficient processing of IL-1β, but dispensable for gasdermin-D cleavage and pyroptosis induction. Our results suggest that the oligomerization of ASC creates a multitude of potential caspase-1 activation sites, thus serving as a signal amplification mechanism for inflammasome-mediated cytokine production.
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
authors.forename: Mathias S
authors.initials: MS
authors.lastname: Dick
authors.affiliation: Focal Area Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Sborgi
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Rühl
authors.affiliation: Focal Area Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hiller
authors.affiliation: Focal Area Infection Biology, Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland.
authors.forename: Petr
authors.initials: P
authors.lastname: Broz
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry; D001854:Bone Marrow Cells / Q000166:cytology*; D053468:CARD Signaling Adaptor Proteins / Q000737:chemistry*; D064113:CRISPR-Cas Systems; D020170:Caspase 1 / Q000737:chemistry; D004789:Enzyme Activation; D057809:HEK293 Cells; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000737:chemistry; D028044:Phosphate-Binding Proteins; D000072417:Protein Domains; D000069292:Pyroptosis; D015398:Signal Transduction; D000094524:Gasdermins
chemical_list: D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D020170:Caspase 1; D058847:Inflammasomes; D053583:Interleukin-1beta; D047908:Intracellular Signaling Peptides and Proteins; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D028044:Phosphate-Binding Proteins; C498368:Gsdmd protein, mouse; D000094524:Gasdermins; C498534:Pycard protein, mouse