As the sensor component of the NLRP3 inflammasome, plays a crucial role in innate immunity and inflammation. In response to pathogens and other damage-associated signals, initiates the formation of the inflammasome polymeric complex, made of NLRP3, PYCARD and CASP1 (and possibly CASP4 and CASP5). Recruitment of proCASP1 to the inflammasome promotes its activation and CASP1-catalyzed IL1B and IL18 maturation and secretion in the extracellular milieu. Activation of NLRP3 inflammasome is also required for HMGB1 secretion. The active cytokines and HMGB1 stimulate inflammatory responses. Inflammasomes can also induce pyroptosis, an inflammatory form of programmed cell death. Under resting conditions, NLRP3 is autoinhibited. NLRP3 activation stimuli include extracellular ATP, reactive oxygen species, K(+) efflux, crystals of monosodium urate or cholesterol, amyloid-beta fibers, environmental or industrial particles and nanoparticles, cytosolic dsRNA, etc (By similarity). Activation upon, at least, K(+) efflux is mediated by the interaction wit NEK7 (By similarity). Activation in presence of cytosolic dsRNA is mediated by DHX33 (By similarity). Independently of inflammasome activation, regulates the differentiation of T helper 2 (Th2) cells and has a role in Th2 cell-dependent asthma and tumor growth (By similarity). During Th2 differentiation, required for optimal IRF4 binding to IL4 promoter and for IRF4-dependent IL4 transcription. Binds to the consensus DNA sequence 5'-GRRGGNRGAG-3'. May also participate in the transcription of IL5, IL13, GATA3, CCR3, CCR4 and MAF (By similarity). Under resting conditions, NLRP3 is autoinhibited. NLRP3 activation stimuli include extracellular ATP, reactive oxygen species, K(+) efflux, crystals of monosodium urate or cholesterol, amyloid-beta fibers, environmental or industrial particles and nanoparticles, cytosolic dsRNA, etc. However, it is unclear what constitutes the direct NLRP3 activator. Activation in presence of cytosolic dsRNA is mediated by DHX33. Sensor component of NLRP3 inflammasomes. Inflammasomes are supramolecular complexes that assemble in the cytosol in response to pathogens and other damage-associated signals and play critical roles in innate immunity and inflammation. The core of NLRP3 inflammasomes consists of a signal sensor component (NLRP3), an adapter (ASC/PYCARD), which recruits an effector pro-inflammatory caspase (CASP1 and, possibly, CASP4 and CASP5). Within the complex, NLRP3 and PYCARD interact via their respective DAPIN/pyrin domains. This interaction initiates speck formation (nucleation) which greatly enhances further addition of soluble PYCARD molecules to the speck in a prion-like polymerization process. NLRP3 localizes at the end of each PYCARD filament. Clustered PYCARD nucleates the formation of CASP1 filaments through the interaction of their respective CARD domains, acting as a platform for CASP1 polymerization. CASP1 filament formation increases local enzyme concentration, resulting in trans-autocleavage and activation. Active CASP1 then processes IL1B and IL18 precursors, leading to the release of mature cytokines in the extracellular milieu and inflammatory response. Reconstituted ternary inflammasomes show star-shaped structures, in which multiple filaments, containing CASP1, protrude radially from a single central hub, containing the sensor protein and PYCARD. In this complex, the sensor protein is sub-stoichiometric to PYCARD, and PYCARD is further substoichiometric to CASP1, suggesting amplifications of signal transduction from the sensor, via the adapter, to the effector. Interacts with MEFV; this interaction targets NLRP3 to degradation by autophagy, hence preventing excessive IL1B- and IL18-mediated inflammation. Interacts with GBP5 (via DAPIN domain); this interaction promotes inflammasome assembly in response to microbial and soluble, but not crystalline, agents. Interacts with EIF2AK2/PKR; this interaction requires EIF2AK2 activity, is accompanied by EIF2AK2 autophosphorylation and promotes inflammasome assembly in response to specific stimuli. Interacts with PML (isoform PML-1) (via the leucine-rich repeat (LRR) domain); PML-mediated increase in NLRP3 inflammasome activation does not depend upon this interaction (By similarity). Directly interacts with IRF4 (via the LRR domain); this interaction is required for optimal IRF4 binding to IL4 promoter and efficient IL4 transactivation during differentiation of Th2 helper T-cells (By similarity). Interacts (via NACHT domain) with DHX33 (via DEAH box). Interacts with PYDC5 (By similarity). Interacts (via NACHT domain) with DDX3X under both LPS-primed and inflammasome-activating conditions (By similarity) Interacts (via NACHT and LRR domains) with ARRB2; this interaction is direct and inducible by polyunsaturated fatty acids (PUFAs). Interacts with CARD8; leading to inhibit formation of the NLRP3 inflammasome (By similarity). Interacts (via LRR repeat domain) with NEK7 (via N-terminus); the interaction is required for the formation of the complex NLRP3:PYCARD, oligomerization of PYCARD and activation of CASP1 (By similarity). In macrophages, under resting conditions, mainly located in the cytosol, on the endoplasmic reticulum. After stimulation with inducers of the NLRP3 inflammasome, mitochondria redistribute in the vicinity of the endoplasmic reticulum in the perinuclear region, which results in colocalization of NLRP3 on the endoplasmic reticulum and PYCARD on mitochondria, allowing the activation of inflammasome assembly. After the induction of pyroptosis, inflammasome specks are released into the extracellular space where they can further promote IL1B processing and where they can be engulfed by macrophages. Phagocytosis induces lysosomal damage and inflammasome activation in the recipient cells (By similarity). In the Th2 subset of CD4(+) helper T-cells, mainly located in the nucleus. Nuclear localization depends upon KPNA2. In the Th1 subset of CD4(+) helper T-cells, mainly cytoplasmic (By similarity). Highly expressed in oocyte, testis, spleen, thymus and kidney. The pyrin domain (also called DAPIN domain or PYD) is involved in PYCARD-binding. The LRR domain mediates the interaction with IRF4 and PML. Intramolecular interactions between NACHT and leucine-rich repeat (LRR) domains may be important for autoinhibition in the absence of activating signal. The disulfide bond in the pyrin domain might play a role in reactive oxygen species-mediated activation. Ubiquitinated; undergoes both 'Lys-48'- and 'Lys-63'-linked polyubiquitination. Ubiquitination does not lead to degradation, but inhibits inflammasome activation (By similarity). Deubiquitination is catalyzed by BRCC3 and associated with NLRP3 activation and inflammasome assembly. This process can be induced by the activation of Toll-like receptors (by LPS), through a non-transcriptional pathway dependent on the mitochondrial production of reactive oxygen species, and by ATP (By similarity). Belongs to the NLRP family.