Dataset Information

Priming by IKKβ recruits NLRP3 to the trans-Golgi network to enable NEK7-independent inflammasome activation

ABSTRACT: The NLRP3 inflammasome plays a central role in antimicrobial defense as well as in the context of sterile inflammatory conditions. NLRP3 activity is governed by two independent signals: The first signal primes NLRP3, rendering it responsive to the second signal, which then triggers inflammasome formation. Our understanding of how NLRP3 priming contributes to inflammasome activation remains limited. Here we show that IKKβ, a kinase activated during priming, induces recruitment of NLRP3 to phosphatidylinositol-4-phosphate (PI4P), a lipid enriched on the trans-Golgi network. Intriguingly, NEK7, a mitotic spindle kinase that had previously been thought to be indispensable for NLRP3 activation, was redundant for inflammasome formation when IKKβ recruited NLRP3 to PI4P. Studying iPSC-derived human macrophages revealed that the IKKβ-mediated NEK7-independent pathway constitutes the predominant NLRP3 priming mechanism in human myeloid cells. Our results suggest that PI4P binding represents a new type of "primed" state into which NLRP3 is brought by IKKβ activity.

INSTRUMENT(S): Orbitrap Exploris 480

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Cell Culture

SUBMITTER: Sophia Mädler

LAB HEAD: Veit Hornung

PROVIDER: PXD035302 | Pride | 2022-11-17

REPOSITORIES: Pride

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			Action	DRS
	20220610_EXPL2_SoMa_SA_S557_inflammasome_fractionation_-12_02.raw	Raw
	20220610_EXPL2_SoMa_SA_S557_inflammasome_fractionation_-12_08.raw	Raw
	20220610_EXPL2_SoMa_SA_S557_inflammasome_fractionation_-12_14.raw	Raw
	20220610_EXPL2_SoMa_SA_S557_inflammasome_fractionation_-3_01.raw	Raw
	20220610_EXPL2_SoMa_SA_S557_inflammasome_fractionation_-3_07.raw	Raw

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Project description:Inflammasome, activated by pathogen-derived and host-derived danger signals, constitutes a multimolecular signaling complex that serves as a platform for caspase-1 (CASP1) activation and interleukin-1beta (IL1B) maturation. The activation of NLRP3 inflammasome requires two-step signals. The first “priming” signal (Signal 1) enhances gene expression of inflammasome components. The second “activation” signal (Signal 2) promotes the assembly of inflammasome components. Deregulated activation of NLRP3 inflammasome contributes to the pathological processes of Alzheimer’s disease (AD) and multiple sclerosis (MS). However, at present, the precise mechanism regulating NLRP3 inflammasome activation and deactivation remains largely unknown. By genome-wide gene expression profiling, we studied the molecular network of NLRP3 inflammasome activation-responsive genes in a human monocyte cell line THP-1 sequentially given two-step signals. We identified the set of 83 NLRP3 inflammasome activation-responsive genes. Among them, we found the NR4A nuclear receptor family NR4A1, NR4A2, and NR4A3, the EGR family EGR1, EGR2, and EGR3, the IkappaB family NFKBIZ, NFKBID, and NFKBIA as a key group of the genes that possibly constitute a negative feedback loop for shutting down inflammation following NLRP3 inflammasome activation. By molecular network analysis, we identified a complex network of NLRP3 inflammasome activation-responsive genes involved in cellular development and death, and immune and inflammatory responses, where transcription factors AP-1, NR4A, and EGR serve as a hub. Thus, NLRP3 inflammasome activation-responsive genes constitute the molecular network composed of a set of negative feedback regulators for prompt resolution of inflammation. To load the Signal 1 (S1), THP-1 cells were incubated for 3 hours in the culture medium with or without inclusion of 0.2 microgram/ml lipopolysaccharide (LPS). To load the Signal 2 (S2), they were incubated further for 2 hours in the culture medium with inclusion of 10 microM nigericin sodium salt dissolved in ethanol or the equal v/v% concentration of ethanol (vehicle), followed by processing for microarray analysis on Human Gene 1.0 ST Array (Affymetrix).

Project description:BACKGROUND: Cryopyrin-Associated Periodic Syndrome (CAPS) is an autoinflammatory condition consequence of monoallelic variants in the NLRP3 gene that exacerbate IL-1β production. These variants are gain-of-function, but the exact regulatory mechanism of the NLRP3 CAPS-inflammasome is not well yet understood. It is considered as a hypersensitive inflammasome triggered by cell priming, but patients with CAPS and animal disease models present inflammatory flares in the absence of external triggers.OBJECTIVES: To study the regulation and activation of the NLRP3 inflammasome in CAPS.METHODS: CAPS derived blood samples and genetically modified macrophages expressing different NLRP3 CAPS-associated variants were used to assess NLRP3 function dissociated from cell priming and cell metabolism.RESULTS: We found that CAPS-associated variants constitutively result in active NLRP3 inflammasomes, that induce a basal cleavage of gasdermin D, IL-18 release and pyroptosis. The constitutive active NLRP3 inflammasome was blocked by MCC950 and was dependent on NLRP3 expression level, being further regulated by deubiquitination. We also showed that activation of NF-κB with lipopolysaccharide or other endogenous host-derived molecules (palmitate, S100A9 or IL-6) further modulated the activation of the NLRP3 CAPS inflammasome and expanded the repertoire of molecules secreted from CAPS macrophages to IL-1β, IL-1α, HMGB1, cystatin B and the P2X7 receptor, identifying novel proteins involved in CAPS pathogenesis. NLRP3 inflammasomes with CAPS associated variants affected the immunometabolism of the myeloid compartment and impaired glycolysis.CONCLUSIONS: These findings demonstrate that NLRP3 CAPS-associated variants form a constitutive active inflammasome that induce basal pyroptosis and IL-18 release without cell priming, suggesting a priming-independent mechanism for the initiation of CAPS flares characterized with a profound affection in the immunometabolism.

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Priming by IKKβ recruits NLRP3 to the trans-Golgi network to enable NEK7-independent inflammasome activation

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