title: The B30.2 domain of pyrin, the familial Mediterranean fever protein, interacts directly with caspase-1 to modulate IL-1beta production.
abstract: Familial Mediterranean fever (FMF) is a recessively inherited autoinflammatory disorder with high carrier frequencies in the Middle East. Pyrin, the protein mutated in FMF, regulates caspase-1 activation and consequently IL-1beta production through cognate interaction of its N-terminal PYRIN motif with the ASC adaptor protein. However, the preponderance of mutations reside in pyrin's C-terminal B30.2 domain. Here we demonstrate direct interaction of this domain with caspase-1. In lysates from cells not expressing ASC, reciprocal GST pull-downs demonstrated the interaction of pyrin with the p20 and p10 catalytic subunits of caspase-1. Coimmunoprecipitations of pyrin and caspase-1 from THP-1 human monocytic cells were consistent with the interaction of endogenous proteins. The C-terminal B30.2 domain of pyrin is necessary and sufficient for the interaction, and binding was reduced by FMF-associated B30.2 mutations. Full-length pyrin attenuated IL-1beta production in cells transfected with a caspase-1/IL-1beta construct, an effect diminished by FMF-associated B30.2 mutations and in B30.2 deletion mutants. Modeling of the crystal structure of caspase-1 with the deduced structure of the pyrin B30.2 domain corroborated both the interaction and the importance of M694V and M680I pyrin mutations. Consistent with a net inhibitory effect of pyrin on IL-1beta activation, small interfering RNA (siRNA)-mediated pyrin knockdown in THP-1 cells augmented IL-1beta production in response to bacterial LPS. Moreover, the IL-1 receptor antagonist anakinra suppressed acute-phase proteins in a patient with FMF and amyloidosis. Our data support a direct, ASC-independent effect of pyrin on IL-1beta activation and suggest heightened IL-1 responsiveness as one factor selecting for pyrin mutations.
authors.affiliation: Genetics and Genomics Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA. chaej@exchange.nih.gov
authors.forename: Jae Jin
authors.initials: JJ
authors.lastname: Chae
authors.forename: Geryl
authors.initials: G
authors.lastname: Wood
authors.forename: Seth L
authors.initials: SL
authors.lastname: Masters
authors.forename: Katharina
authors.initials: K
authors.lastname: Richard
authors.forename: Grace
authors.initials: G
authors.lastname: Park
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Smith
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Kastner
mesh_terms: D020170:Caspase 1 / Q000378:metabolism*; D061945:Caspase Inhibitors; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D010505:Familial Mediterranean Fever / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism; D009154:Mutation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary / Q000235:genetics; D000071198:Pyrin; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D012795:Sialoglycoproteins / Q000494:pharmacology
chemical_list: D061945:Caspase Inhibitors; D003598:Cytoskeletal Proteins; C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; C000604192:MEFV protein, human; D000071198:Pyrin; D034741:RNA, Small Interfering; D012795:Sialoglycoproteins; D020170:Caspase 1