Journal
CELL DEATH AND DIFFERENTIATION
Volume 21, Issue 3, Pages 451-461Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/cdd.2013.165
Keywords
c-FLIP; inflammasome; IL-1 beta; caspase-1; caspase-8; macrophages
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Funding
- National Health Research Institute [NHRI-EX101-10012SI]
- National Science Council [NSC101-2321-B001-002]
- Academia Sinica Investigator Award from Academia Sinica, and Taiwan, R.O.C
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Cellular FLICE-inhibitory protein (c-FLIP) is an inhibitor of caspase-8 and is required for macrophage survival. Recent studies have revealed a selective role of caspase-8 in noncanonical IL-1 beta production that is independent of caspase-1 or inflammasome. Here we demonstrated that c-FLIPL is an unexpected contributor to canonical inflammasome activation for the generation of caspase-1 and active IL-1 beta. Hemizygotic deletion of c-FLIP impaired ATP-and monosodium uric acid (MSU)-induced IL-1 beta production in macrophages primed through Toll-like receptors (TLRs). Decreased IL-1 beta expression was attributed to a reduced activation of caspase-1 in c-FLIP hemizygotic cells. In contrast, the production of TNF-alpha was not affected by downregulation in c-FLIP. c-FLIPL interacted with NLRP3 or procaspase-1. c-FLIP is required for the full NLRP3 inflammasome assembly and NLRP3 mitochondrial localization, and c-FLIP is associated with NLRP3 inflammasome. c-FLIP downregulation also reduced AIM2 inflammasome activation. In contrast, c-FLIP inhibited SMAC mimetic-, FasL-, or Dectin-1-induced IL-1 beta generation that is caspase-8-mediated. Our results demonstrate a prominent role of c-FLIPL in the optimal activation of the NLRP3 and AIM2 inflammasomes, and suggest that c-FLIP could be a valid target for treatment of inflammatory diseases caused by over-activation of inflammasomes.
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