Functions as key mediator in apoptosis and inflammation (PubMed:12464617). Promotes caspase-mediated apoptosis (PubMed:12464617). Induces proteolytic processing of caspa and caspa-dependent apoptosis (PubMed:12464617). In innate immune response acts as an integral adapter in the assembly of NLRP1 inflammasomes which activate caspases caspa and caspb leading to processing and secretion of the pro-inflammatory cytokine il1b (PubMed:30150286). The function as activating adapter in different types of inflammasomes is mediated by the pyrin and CARD domains and their homotypic interactions (PubMed:30150286). Also involved in transcriptional activation of cytokines and chemokines independent of the inflammasome. Self-associates (via pyrin and CARD domains) (PubMed:12464617, PubMed:29791979). Interacts (via pyrin domain) with caspa (via pyrin domain) (PubMed:12464617, PubMed:30150286, PubMed:29791979). Interacts with caspb; the interaction only occurs in the presence of nlrp1 (PubMed:30150286). Component of NLRP1 inflammasomes (PubMed:30150286). 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 (PubMed:30150286). The NLRP1 inflammasome is composed of the signal sensor nlrp1, and the adapter pycard (asc), which recruit effector pro-inflammatory caspases caspa and/or caspb (PubMed:30150286). The interaction between nlrp1 and pycard is required for the sequential recruitment of caspa and then caspb (PubMed:30150286). Within the complex caspa is preferentially recruited first and this causes the cleavage of pro-il1b into the midformed il1b (PubMed:30150286). This is followed by the recruitment of caspb, which is activated and cleaves the midformed il1b resulting in il1b maturation (PubMed:30150286). Interacts (via pyrin domain) with NLP3X1 (via pyrin domain) (PubMed:29791979). Co-localizes with nlrp1, caspa and caspb in the cytoplasm (PubMed:30150286). Co-localizes with caspa and caspb independently at large cytoplasmic aggregates, known as specks (PubMed:12464617, PubMed:30150286, PubMed:29791979). Expressed in the kidney, intestine and gill (PubMed:29791979). Expressed at low levels in the heart (PubMed:29791979). First expressed during embryonic development at 1 somite at 10 hours post-fertilization (hpf) (PubMed:29791979). During embryonic development, expressed in the epidermis, mouth and pharyngeal arches at 48 and 72 hpf (PubMed:12464617). Up-regulated in response to infection with the bacteria E.tarda. The pyrin domain mediates homotypic interactions with pyrin domain of other proteins. Morpholino knockdown in one-cell embryos results in reduced caspa activity and impairs caspa activity in response to infection with the bacterium S.typhimurium (PubMed:29123523). In addition, there is increased susceptibility to the bacterium S.typhimurium (PubMed:29123523).