Cysteine protease that plays essential roles in programmed cell death, axonal degeneration, development and innate immunity (PubMed:18981099, PubMed:22555455, PubMed:23695670, PubMed:32298652). Acts as a non-canonical executioner caspase during apoptosis: localizes in the nucleus and cleaves the nuclear structural protein NUMA1 and lamin A/LMNA thereby inducing nuclear shrinkage and fragmentation (By similarity). Lamin-A/LMNA cleavage is required for chromatin condensation and nuclear disassembly during apoptotic execution (By similarity). Acts as a regulator of liver damage by promoting hepatocyte apoptosis: in absence of phosphorylation by AMP-activated protein kinase (AMPK), catalyzes cleavage of BID, leading to cytochrome c release, thereby participating in nonalcoholic steatohepatitis (PubMed:32029622). Cleaves PARK7/DJ-1 in cells undergoing apoptosis (PubMed:22555455). Involved in intrinsic apoptosis by mediating cleavage of RIPK1 (By similarity). Furthermore, cleaves many transcription factors such as NF-kappa-B and cAMP response element-binding protein/CREBBP (By similarity). Cleaves phospholipid scramblase proteins XKR4 and XKR9 (PubMed:25231987). In addition to apoptosis, involved in different forms of programmed cell death (PubMed:32298652). Plays an essential role in defense against viruses by acting as a central mediator of the ZBP1-mediated pyroptosis, apoptosis, and necroptosis (PANoptosis), independently of its cysteine protease activity (PubMed:32298652). PANoptosis is a unique inflammatory programmed cell death, which provides a molecular scaffold that allows the interactions and activation of machinery required for inflammasome/pyroptosis, apoptosis and necroptosis (PubMed:32298652). Mechanistically, interacts with RIPK3 and enhances the interaction between RIPK3 and ZBP1, leading to ZBP1-mediated inflammasome activation and cell death (PubMed:32298652). Plays an essential role in axon degeneration during axon pruning which is the remodeling of axons during neurogenesis but not apoptosis (PubMed:23695670). Regulates B-cell programs both during early development and after antigen stimulation (PubMed:18981099, PubMed:29863787). Strict requirement for Asp at position P1 and has a preferred cleavage sequence of Val-Glu-His-Asp-|-. During activation, the N-terminal disordered prodomain is removed by cleavage. Concomitantly, double cleavage gives rise to a large 18-kDa and a small 11-kDa subunit. The two large and two small subunits then assemble to form the active CASP6 complex. Can be cleaved and activated by different caspases, depending on the context. Cleaved and activated by caspase-8 (CASP8) and subsequently by caspase-3 (CASP3). Can also undergo autoactivation by mediating autocleavage at Asp-162 and Asp-175, while it is not able to cleave its N-terminal disordered prodomain. Intramolecular cleavage at Asp-175 is a prerequisite for CASP6 self-activation. Cleaved and activated by CASP1 in neurons, possibly in the context of inflammation. Phosphorylation at Ser-239 inhibits autocleavage, preventing caspase activation. Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a 18 kDa (p18) and a 11 kDa (p11) subunit. Interacts with BIRC6/bruce. Interacts with RIPK3. Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a 18 kDa (Caspase-6 subunit p18) and a 11 kDa (Caspase-6 subunit p11) subunit. Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a 18 kDa (Caspase-6 subunit p18) and a 11 kDa (Caspase-6 subunit p11) subunit. Highly expressed in lung, liver, kidney, testis, and heart. Lower levels in spleen, skeletal muscle and brain. Expressed in neurons. The N-terminal disordered prodomain is required to prevent self-activation. The Tri-arginine exosite is required to recruit substrates for hydrolysis. Undergoes helix-strand structural transitions upon substrate-binding: the 130's region interconverts between an inactive helical state and the canonically active strand state. Other caspases rest constitutively in the strand conformation before and after substrate-binding. Phosphorylated by NUAK1; phosphorylation inhibits self-activation. Phosphorylation at Ser-239 by AMP-activated protein kinase (PRKAA1 or PRKAA2) inhibits autocleavage, preventing caspase activation, thereby preventing hepatocyte apoptosis. Palmitoylation by ZDHHC17 blocks dimerization and subsequent activation, leading to inhibit the cysteine protease activity. Can be cleaved and activated by different caspases, depending on the context. Cleaved and activated by caspase-8 (CASP8) and subsequently by caspase-3 (CASP3). Can also undergo autoactivation by mediating autocleavage at Asp-162 and Asp-175, while it is not able to cleave its N-terminal disordered prodomain. Cleaved and activated by CASP1, possibly in the context of inflammation. Casp6-knockout mice are grossly normal, breed with Mendelian ratio, and are only slightly protected from anti-Fas/CD95-induced cell death (PubMed:11062535). Casp6-deficient neurons undergo apoptosis and exhibit soma and axon degeneration just as wild type neurons (PubMed:23695670). While Casp6-deficiency is able to block axon degeneration with local deprivation, it is incapable of doing so with global deprivation (PubMed:23695670). In addition, B-cell differentiation into plasma cells is accelerated in deletion mutants compared to wild-type (PubMed:18981099, PubMed:29863787). Casp6-knockout mice are more susceptible to influenza virus infection (PubMed:32298652). Belongs to the peptidase C14A family.