Caspase-1 is a crucial cysteine protease that plays a significant role in inflammation and cell death, particularly in the context of the immune system. Caspase-1 is synthesized as a 45 kDa precursor and is proteolytically cleaved during activation to generate two subunits of p20 (22 kDa) and p10 (10 kDa), which form heterodimers and then form a tetramer. It features a CARD domain and its caspase domain, and homotypic CARD interactions result in the recruitment of pro-caspase-1 to the inflammasome complex. Caspase-1 is originally named interleukin-1β converting enzyme (ICE) and is responsible for the processing of pro-interleukin-1β (IL-1β) to its biologically active form. This processing is central to its proinflammatory role, as IL-1β is a key mediator in coordinating diverse processes such as cellular recruitment and regulation of mood, sleep, appetite, and body temperature. Caspase-1 is known to initiate a programmed necrosis called pyroptosis, which is inherently inflammatory and triggered by various pathological stimuli. It also cleaves gasdermin D (GSDMD) in the cytoplasm, releasing its N-terminal domain to induce pyroptosis. In addition to its role in pyroptosis, caspase-1 has been implicated in initiating apoptosis in the absence of GSDMD, involving the Bid-caspase-9-caspase-3 axis.
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