CASc

Caspase, interleukin-1 beta converting enzyme (ICE) homologues		 CASc
SMART accession number:SM00115
Description: Cysteine aspartases that mediate programmed cell death (apoptosis). Caspases are synthesised as zymogens and activated by proteolysis of the peptide backbone adjacent to an aspartate. The resulting two subunits associate to form an (alpha)2(beta)2-tetramer which is the active enzyme. Activation of caspases can be mediated by other caspase homologues.
Interpro abstract (IPR015917):

This entry represents the C-terminal conserved domain found in caspases mostly from animals. This domain includes the core of p45 (45 kDa) precursor of caspases, which can be processed to produce the active p20 (20 kDa) and p10 (10 kDa) subunits.

Caspases (Cysteine-dependent ASPartyl-specific proteASE) are cysteine peptidases that belong to the MEROPS peptidase family C14 (caspase family, clan CD) based on the architecture of their catalytic dyad or triad [(PUBMED:11517925)]. Caspases from animals can be classified as C14A subfamiy. Caspases are tightly regulated proteins that require zymogen activation to become active, and once active can be regulated by caspase inhibitors. Activated caspases act as cysteine proteases, using the sulphydryl group of a cysteine side chain for catalysing peptide bond cleavage at aspartyl residues in their substrates. The catalytic cysteine and histidine residues are on the p20 subunit after cleavage of the p45 precursor.

Caspases are mainly involved in mediating cell death (apoptosis) [(PUBMED:10578171), (PUBMED:10872455), (PUBMED:15077141)]. They have two main roles within the apoptosis cascade: as initiators that trigger the cell death process, and as effectors of the process itself. Caspase-mediated apoptosis follows two main pathways, one extrinsic and the other intrinsic or mitochondrial-mediated. The extrinsic pathway involves the stimulation of various TNF (tumour necrosis factor) cell surface receptors on cells targeted to die by various TNF cytokines that are produced by cells such as cytotoxic T cells. The activated receptor transmits the signal to the cytoplasm by recruiting FADD, which forms a death-inducing signalling complex (DISC) with caspase-8. The subsequent activation of caspase-8 initiates the apoptosis cascade involving caspases 3, 4, 6, 7, 9 and 10. The intrinsic pathway arises from signals that originate within the cell as a consequence of cellular stress or DNA damage. The stimulation or inhibition of different Bcl-2 family receptors results in the leakage of cytochrome c from the mitochondria, and the formation of an apoptosome composed of cytochrome c, Apaf1 and caspase-9. The subsequent activation of caspase-9 initiates the apoptosis cascade involving caspases 3 and 7, among others. At the end of the cascade, caspases act on a variety of signal transduction proteins, cytoskeletal and nuclear proteins, chromatin-modifying proteins, DNA repair proteins and endonucleases that destroy the cell by disintegrating its contents, including its DNA. The different caspases have different domain architectures depending upon where they fit into the apoptosis cascades, however they all carry the catalytic p10 and p20 subunits.

Caspases can have roles other than in apoptosis, such as caspase-1 (interleukin-1 beta convertase) (EC 3.4.22.36), which is involved in the inflammatory process. The activation of apoptosis can sometimes lead to caspase-1 activation, providing a link between apoptosis and inflammation, such as during the targeting of infected cells. Caspases may also be involved in cell differentiation [(PUBMED:15066636)].

GO function:cysteine-type peptidase activity (GO:0008234)
Family alignment:
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There are 6164 CASc domains in 6090 proteins in SMART's nrdb database.

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