The CASP1 gene at 11q22.3 codes the 404 amino acid prescursor peptide to caspase-1. This is cleaved into:
- Caspase-1 subunit p20
- Caspase-1 subunit p10
Caspase-1 is a thiol protease that cleaves IL-1 beta, releasing the mature IL-1β cytokine which is involved in a variety of inflammatory processes and important for defence against pathogens. It also activates IL-18, and IL-33, so in the later case being important in type-2 helper T (Th2) cell response. There are five isoforms produced by alternative splicing (alpha, beta, delta, gamma and epsilon). It also cleaves and activates sterol regulatory element binding proteins (SREBPs) so has multiple roles. Functionally it is found as an heterotetramer that consists of two anti-parallel arranged heterodimers. Each of these is formed by the 20 kDa (p20) and a 10 kDa (p10) subunits formed by autocatalysis. The p20 subunit can also form a heterodimer with the epsilon isoform which then has an inhibitory effect. It is a component of the activated inflammasome.