As the sensor component of the NLRP9 inflammasome, plays a crucial role in innate immunity and inflammation. In response to pathogens, including rotavirus, initiates the formation of the inflammasome polymeric complex, made of NLRP9, PYCARD and CASP1. Recruitment of proCASP1 to the inflammasome promotes its activation and CASP1-catalyzed IL1B and IL18 maturation and release in the extracellular milieu. The active cytokines stimulate inflammatory responses. Inflammasomes can also induce pyroptosis, an inflammatory form of programmed cell death. NLRP9 inflammasome activation may be initiated by DHX9 interaction with viral double-stranded RNA (dsRNA), preferentially to short dsRNA segments. Sensor component of NLRP9 inflammasomes. Inflammasomes are supramolecular complexes that assemble in the cytosol in response to pathogens, such as rotavirus, and play critical roles in innate immunity and inflammation. The core of NLRP9 inflammasomes consists of a signal sensor component (NLRP9), an adapter (ASC/PYCARD), which recruits an effector pro-inflammatory caspase (CASP1). Within the complex, NLRP9 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. 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 (PubMed:28636595). Interacts with DHX9 upon rotavirus infection; this interaction may trigger inflammasome activation and inflammatory response (PubMed:28636595). Expressed in ileum intestinal epithelial cells. Not detected in peripheral blood mononuclear cells (PubMed:28636595). Expressed in cerebral endothelial cells and, at much lower levels, in brain pericytes (PubMed:28432035). In brain pericytes, up-regulated at the mRNA level in response to oxidative stress. Belongs to the NLRP family.