Schematic structure of NLRP3 inflammasome complex. The NLRP3 inflammasome complex consists of the NLRP3 scaffold, the ASC adaptor, and pro-caspase-1 proteins. Deletion of the CARD domain and activation of caspase-1 domain of pro-caspase-1 leads to formation of active caspase-1, then resulting in cleavage from pro-IL-1β to IL-1β. ASC: apoptosis-associated speck-like protein, CARD: caspase activation and recruitment domain, IL: interleukin, LRR: leucine-rich repeat, NACHT: neuronal apoptosis inhibitory protein (NAIP), MHC class II transcription activator (CIITA), incompatibility locus protein from Podospora anserina (HET-E), and telomerase-associated protein (TP1), NLRP3: NACHT, LRR, and PYD domains-containing protein 3, PYD: pyrin domain.|@|~(^,^)~|@|Signal pathway for NLRP3 inflammasome activation. Activation of the NLRP3 inflammasome is essential for two steps such as priming (signal 1) and activation (signal 2). In priming step, activation of TLR or TNFR after exposure of danger signals facilitates NF-κB signaling pathway for initiating transcription and production of precursor of pro-inflammatory cytokine including pro-IL-1β and pro-IL-18. Next, sensing PAMPs or DAMPs triggers NLRP3 oligomerization and ASC and pro-caspase-1 recruitment (signal 2). Autocleavage and activation of caspase-1 results in maturation and release of pro-inflammatory cytokines IL-1β and IL-18. PAMPs: pathogen-associated molecular patterns, DAMPs: damage-associated molecular patterns, ASC: apoptosis-associated speck-like protein, CARD: caspase activation and recruitment domain, TLR: toll-like receptor, TNFR: tumor necrosis factor receptor, ROS: reactive oxygen species, IKK: IκB kinase, IL: interleukin, NF-κB: nuclear factor-κB, NACHT: neuronal apoptosis inhibitory protein (NAIP), MHC class II transcription activator (CIITA), incompatibility locus protein from Podospora anserina (HET-E), and telomerase-associated protein (TP1), NLRP3: NACHT, LRR, and PYD domains-containing protein 3.|@|~(^,^)~|@|Mechanism for IL-1β/IL-1R-related inflammatory signaling pathway. IL-1β/IL-1R complex is generated by the heterodimer signaling receptors and cytokine. The TIR domain, an intercellular signaling protein motif between receptors and adaptors, associates with adaptor MyD88, thus resulting in recruitment of IRAK and dimerized TRAF6. This subsequently activates multiple downstream signaling pathways including IκB-kinase complex and MAPK. Activation of transcription factors including NF-κB and AP-1 results in diverse pro-inflammatory cytokines and chemokines. IL-1β: interleukin-1β, IL-1RI: interleukin-1 receptor type I, TIR: toll/interleukin-1 receptor, MyD88: myeloid differentiation primary response 88, IRAK: interleukin-1 receptor associated kinase, TRAF6: TNF receptor-associated factor 6, TNF: tumor necrosis factor, NF-κB: nuclear factor-κB.
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