Inflammatory caspase‑1 (CASP1) is activated within the canonical inflammasome, a multiprotein complex assembled in response to sensing of pathogen‑derived particles or host‑derived danger signals (reviewed in Kelley N et al. 2019; Zheng D et al. 2020). Activated, CASP1 cleaves gasdermin D (GSDMD) within the central linker region generating a 31‑kDa N‑terminal fragment (GSDMD (1‑275)) which has an intrinsic pore‑forming activity to execute pyroptosis and a 22‑kDa C‑terminal fragment (GSDMD (276‑484)) which otherwise inhibits cell death through intramolecular domain association (Shi J et al. 2015; Ding J et al. 2016; Sborgi L et al. 2016; Liu Z et al. 2019; Yang J et al. 2018; Kuang S et al. 2017). The expression of GSDMD (1‑275) in human embryonic kidney 293 (HEK293) cells induced pyroptosis (Shi J et al. 2015). The catalytic domain of CASP1 was found to directly bind to GSDMD or its cleavage site peptide, FLTD (Yang J et al. 2018). A GSDMD‑derived inhibitor, N‑acetyl‑Phe‑Leu‑Thr‑Asp‑chloromethylketone (Ac‑FLTD‑CMK), inhibited GSDMD cleavage in vitro and suppressed pyroptosis downstream of both canonical and noncanonical inflammasomes. The structure of human CASP1 in complex with Ac‑FLTD‑CMK revealed extensive enzyme–inhibitor interactions involving both hydrogen bonds and hydrophobic contacts (Yang J et al. 2018). The most critical element determining the specific targeting of GSDMD by CASP1 as well as CASP4/5 and mouse Casp11 is a hydrophobic surface on the C‑terminal fragment (GSDMD (276‑484)) that is recognized by a short two-stranded β sheet at the dimer interface of the caspases, which leads to an unconventional tetrapeptide (cleavage-site sequence)-independent cleavage of GSDMD (Wang K et al. 2020; Liu Z et al. 2020). In addition, biochemical and structural studies of human GSDMD and mouse GSDMA3 showed the auto‑inhibitory conformation of gasdermin domains which is released upon interdomain cleavage by inflammatory caspases, including CASP1 (Shi J et al. 2015; Ding J et al. 2016; Liu Z et al. 2019; Yang J et al. 2018; Kuang S et al. 2017; reviewed in Orning P et al. 2019). Thus, the CASP1‑mediated cleavage is thought to release the cytotoxic GSDMD (1‑275) from intramolecular autoinhibition by the C‑terminal fragment of GSDMD. The N‑terminal domain GSDMD (1‑275) binds and inserts into lipid membranes where it assembles into pores 10‑16 nm in diameter (Ding J et al. 2016; Sborgi L et al. 2016). GSDMD pores facilitate the secretion of active forms of interleukin‑1β (IL‑1β) and IL‑18 from pyroptotic cells (Shi J et al. 2015; He W et al. 2015; Ding J et al. 2016; Evavold CL et al. 2018). "The increasing abundance of membrane pores ultimately leads to membrane rupture and pyroptosis, releasing the entire cellular contents" ‑ Feng S et al. 2018.
This Reactome event shows CASP1‑mediated cleavage of GSDMD at D275.