Functions as a key mediator in apoptosis and inflammation (PubMed : 11103777, PubMed : 12646168, PubMed : 15030775, PubMed : 17349957, PubMed : 17599095, PubMed : 19158675, PubMed : 19158676, PubMed : 19234215, PubMed : 19494289, PubMed : 21487011, PubMed : 24630722, PubMed : 25847972, PubMed : 30674671, PubMed : 34678144, PubMed : 36050480). Promotes caspase-mediated apoptosis involving predominantly caspase-8 and also caspase-9 in a probable cell type-specific manner (PubMed : 11103777, PubMed : 12646168). Involved in activation of the mitochondrial apoptotic pathway, promotes caspase-8-dependent proteolytic maturation of BID independently of FADD in certain cell types and also mediates mitochondrial translocation of BAX and activates BAX-dependent apoptosis coupled to activation of caspase-9, -2 and -3 (PubMed : 14730312, PubMed : 16964285). Involved in innate immune response by acting as an integral adapter in the assembly of various inflammasomes (NLRP1, NLRP2, NLRP3, NLRP6, AIM2 and probably IFI16) which recruit and activate caspase-1 leading to processing and secretion of pro-inflammatory cytokines (PubMed : 15030775, PubMed : 16982856, PubMed : 17349957, PubMed : 17599095, PubMed : 19158675, PubMed : 19158676, PubMed : 19234215, PubMed : 21487011, PubMed : 23530044, PubMed : 24630722, PubMed : 25847972, PubMed : 29440442, PubMed : 30674671, PubMed : 33980849, PubMed : 34678144, PubMed : 34706239). Caspase-1-dependent inflammation leads to macrophage pyroptosis, a form of cell death (PubMed : 24630722). The function as activating adapter in different types of inflammasomes is mediated by the pyrin and CARD domains and their homotypic interactions (PubMed : 14499617, PubMed : 19234215, PubMed : 24630722). Clustered PYCARD nucleates the formation of caspase-1 filaments through the interaction of their respective CARD domains, acting as a platform for of caspase-1 polymerization (PubMed : 24630722). In the NLRP1 and NLRC4 inflammasomes seems not be required but facilitates the processing of procaspase-1 (PubMed : 17349957). In cooperation with NOD2 involved in an inflammasome activated by bacterial muramyl dipeptide leading to caspase-1 activation (PubMed : 16964285). May be involved in RIGI-triggered pro-inflammatory responses and inflammasome activation (PubMed : 19915568). In collaboration with AIM2 which detects cytosolic double-stranded DNA may also be involved in a caspase-1-independent cell death that involves caspase-8 (PubMed : 19158675, PubMed : 19158676). In adaptive immunity may be involved in maturation of dendritic cells to stimulate T-cell immunity and in cytoskeletal rearrangements coupled to chemotaxis and antigen uptake may be involved in post-transcriptional regulation of the guanine nucleotide exchange factor DOCK2; the latter function is proposed to involve the nuclear form (PubMed : 22732093). Also involved in transcriptional activation of cytokines and chemokines independent of the inflammasome; this function may involve AP-1, NF-kappa-B, MAPK and caspase-8 signaling pathways (PubMed : 12486103, PubMed : 16585594). For regulation of NF-kappa-B activating and inhibiting functions have been reported (PubMed : 12486103). Modulates NF-kappa-B induction at the level of the IKK complex by inhibiting kinase activity of CHUK and IKBK (PubMed : 12486103, PubMed : 16585594). Proposed to compete with RIPK2 for association with CASP1 thereby down-regulating CASP1-mediated RIPK2-dependent NF-kappa-B activation and activating interleukin-1 beta processing (PubMed : 16585594). Modulates host resistance to DNA virus infection, probably by inducing the cleavage of and inactivating CGAS in presence of cytoplasmic double-stranded DNA (PubMed : 28314590).. Isoform 2. May have a regulating effect on the function as inflammasome adapter.. Isoform 3. Seems to inhibit inflammasome-mediated maturation of interleukin-1 beta.