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Participation of c-FLIP in NLRP3 and AIM2 inflammasome activation.

ABSTRACT: 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? production that is independent of caspase-1 or inflammasome. Here we demonstrated that c-FLIP(L) is an unexpected contributor to canonical inflammasome activation for the generation of caspase-1 and active IL-1?. Hemizygotic deletion of c-FLIP impaired ATP- and monosodium uric acid (MSU)-induced IL-1? production in macrophages primed through Toll-like receptors (TLRs). Decreased IL-1? expression was attributed to a reduced activation of caspase-1 in c-FLIP hemizygotic cells. In contrast, the production of TNF-? was not affected by downregulation in c-FLIP. c-FLIP(L) 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? generation that is caspase-8-mediated. Our results demonstrate a prominent role of c-FLIP(L) 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.

SUBMITTER: Wu YH

PROVIDER: S-EPMC3921593 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Participation of c-FLIP in NLRP3 and AIM2 inflammasome activation.

Wu Y-H YH Kuo W-C WC Wu Y-J YJ Yang K-T KT Chen S-T ST Jiang S-T ST Gordy C C He Y-W YW Lai M-Z MZ

Cell death and differentiation 20131122 3

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-1β production that is independent of caspase-1 or inflammasome. Here we demonstrated that c-FLIP(L) is an unexpected contributor to canonical inflammasome activation for the generation of caspase-1 and active IL-1β. Hemizygotic deletion of c-FLIP impaired ATP- and monosodium uric acid (MSU)-induced IL-1β pro ...[more]

PMID: 24270411

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Project description:BackgroundAIM2, a cytosolic DNA sensor, plays an important role during infection caused by pathogens with double-stranded DNA; however, its role in human cytomegalovirus (HCMV) infection remains unclear. Previously, we showed an increase in AIM2 protein levels during the early stage of HCMV infection and a decrease 24 h post infection. Because HCMV has developed a variety of strategies to evade host immunity, we speculated that this decline might be attributed to a viral immune escape mechanism. The tegument protein pUL83 is an important immune evasion protein and several studies have reported that pUL83 binds to specific cellular proteins, such as AIM2-like receptor IFI16, to affect their functions. To determine whether pUL83 contributes to the variation in AIM2 levels during HCMV infection, we investigated the pUL83/AIM2 interaction and its impact on the AIM2 inflammasome activation.MethodsWe constructed plasmids expressing recombinant pUL83 and AIM2 proteins for two-hybrid and chemiluminescence assays. Using co-immunoprecipitation and immunofluorescent co-localization, we confirmed the interaction of pUL83/AIM2 in THP-1-derived macrophages infected with HCMV AD169 strain. Furthermore, by investigating the expression and cleavage of inflammasome-associated proteins in recombinant HEK293T cells expressing AIM2, apoptosis-associated speck-like protein (ASC), pro-caspase-1 and pro-IL-1β, we evaluated the effect of pUL83 on the AIM2 inflammasome.ResultsAn interaction between pUL83 and AIM2 was detected in macrophages infected with HCMV as well as in transfected HEK293T cells. Moreover, transfection of the pUL83 expression vector into recombinant HEK293T cells stimulated by poly(dA:dT) resulted in reduced expression and activation of AIM2 inflammasome-associated proteins, compared with the absence of pUL83.ConclusionsOur data indicate that pUL83 interacts with AIM2 in the cytoplasm during the early stages of HCMV infection. The pUL83/AIM2 interaction deregulates the activation of AIM2 inflammasome. These findings reveal a new strategy of immune evasion developed by HCMV, which may facilitate latent infection.

Dataset Information

Participation of c-FLIP in NLRP3 and AIM2 inflammasome activation.

Publications

Participation of c-FLIP in NLRP3 and AIM2 inflammasome activation.

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