The B30.2 domain of pyrin, the familial Mediterranean fever protein, interacts directly with caspase-1 to modulate IL-1beta production.
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.
Chae
Jae Jin
JJ
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
Wood
Geryl
G
Masters
Seth L
SL
Richard
Katharina
K
Park
Grace
G
Smith
Brian J
BJ
Kastner
Daniel L
DL
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
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