Caspase 1

Caspase-1/Interleukin-1 converting enzyme (ICE) is an evolutionarily conserved enzyme that proteolytically cleaves other proteins, such as the precursors of the inflammatory cytokines interleukin 1β and interleukin 18 as well as the pyroptosis inducer Gasdermin D, into active mature peptides. It plays a central role in cell immunity as an inflammatory response initiator. Once activated through formation of an inflammasome complex, it initiates a proinflammatory response through the cleavage and thus activation of the two inflammatory cytokines, interleukin 1β (IL-1β) and interleukin 18 (IL-18) as well as pyroptosis, a programmed lytic cell death pathway, through cleavage of Gasdermin D. The two inflammatory cytokines activated by Caspase-1 are excreted from the cell to further induce the inflammatory response in neighboring cells.1BMQ, 1IBC, 1ICE, 1RWK, 1RWM, 1RWN, 1RWO, 1RWP, 1RWV, 1RWW, 1RWX, 1SC1, 1SC3, 1SC4, 2FQQ, 2H48, 2H4W, 2H4Y, 2H51, 2H54, 2HBQ, 2HBR, 2HBY, 2HBZ, 3D6F, 3D6H, 3D6M, 3E4C, 3NS7, 5FNA83412362ENSG00000137752ENSMUSG00000025888P29466P29452NM_033294NM_033295NM_009807NP_150636NP_150637NP_033937Caspase-1 is evolutionarily conserved in many eukaryotes of the Kingdom Animalia. Due to its role in the inflammatory immune response, it is highly expressed in the immune organs such as the liver, kidney, spleen, and blood (neutrophils). Following infection, the inflammatory response increases expression of Caspase-1, by a positive feedback mechanism that amplifies the response.Caspase-1 is produced as a zymogen that can then be cleaved into 20 kDa (p20) and 10 kDa (p10) subunits that become part of the active enzyme. Active Caspase 1 contains two heterodimers of p20 and p10. It contains a catalytic domain with an active site that spans both the p20 and p10 subunits, as well as a noncatalytic Caspase Activation and Recruitment Domain (CARD) . It interacts with other CARD containing proteins such as Apoptosis-Associated Speck-like Protein Containing a CARD (ASC) and Nod-Like Receptor (NLR) Family CARD Domain-Containing Protein 4 (NLRC4) through CARD-CARD interactions in the formation of inflammasomes.Caspase-1, normally in its physiologically inactive zymogen form, autoactivates when it is assembled into the filamentous inflammasome complex by autoproteolysis into the p10 and p20 subunits. The inflammasome complex is a ring complex composed of trimers of a signal specific sensor protein such as those of the NLR family and the AIM-1 (Absent in Melanoma) like receptors, an adaptor protein such as ASC, and a caspase, in this case Caspase-1. In some cases, where the signaling proteins contain their own CARDs, like in NLRP1 and NLRC4, the CARD –CARD interaction is direct, meaning there is no adaptor protein in the complex. There are a variety of sensor and adaptor proteins, the various combinations of which confer the inflammasomes' responses to specific signals. This allows the cell to have varying degrees of inflammatory responses based on the severity of the danger signal received.Activated Caspase 1 proteolytically cleaves pro IL-1β and pro IL-18 into their active forms, IL-1β and IL-18. The active cytokines lead to a downstream inflammatory response. It also cleaves Gasdermin D into its active form, which leads to pyroptosis.