1.C.123.1.1
Pore-forming Gasdermin D (Gasdermin-A3, GSDMD, DFNA5L, GSDMDC1, FKSG10) of 484 aas (Ding et al. 2016). GSDMD is activated by inflammasome-activated caspases-1/-4/-5/-11 as well as a caspase-8-mediated pathway during Yersinia infection. These caspases cleave GSDMD to release its functional N-terminal fragment (GSDMD-NT) from its auto-inhibitory C-terminal fragment (GSDMD-CT). GSDMD-NTs bind to acid lipids in mammalian cell membranes and bacterial membranes, oligomerize, and insert into the membranes to form large transmembrane pores. Consequently, cellular contents including inflammatory cytokines are released (e.g., IL-1β), and cells can undergo pyroptosis, a highly inflammatory form of cell death (Xia et al. 2019; Muendlein et al. 2020). As organelles of the innate immune system, inflammasomes activate caspase-1 and other inflammatory caspases that cleave gasdermin D. Caspase-1 also cleaves inactive precursors of the interleukin (IL)-1 family to generate mature cytokines such as IL-1beta and IL-18. Cleaved GSDMD forms transmembrane pores to enable the release of IL-1 and to drive cell lysis through pyroptosis. Cryo-EM structures of the pore and the prepore reveal the different conformations of the two states, as well as membrane-binding elements including a hydrophobic anchor and three positively charged patches. The pore conduit is predominantly negatively charged, but IL-1 precursors have an acidic domain that is proteolytically removed by caspase-1. When permeabilized, unlysed liposomes release positively charged and neutral cargoes faster than negatively charged cargoes of similar sizes, and the pores favor the passage of IL-1beta and IL-18 over that of their precursors (Xia et al. 2021). Gasdermin-A3 oligomers assemble on the membrane surface where they remain attached and mobile. Once inserted into the membrane it grows variable oligomeric stoichiometries and shapes, each able to open transmembrane pores. Molecular dynamics simulations resolved how the membrane-inserted amphiphilic beta-hairpins and the structurally adapting hydrophilic head domains stabilize variable oligomeric conformations and open the pore. Without a vertical collapse, gasdermin pore formation propagates along a set of multiple parallel but connected reaction pathways to ensure a robust cellular response (Mari et al. 2022). Gasdermin D (GSDMD) is the common effector for cytokine secretion and pyroptosis downstream of inflammasome activation by forming large transmembrane pores upon cleavage by inflammatory caspases. Du et al. 2023 reported that GSDMD cleavage is not sufficient for its pore formation; GSDMD must be lipidated by S-palmitoylation at Cys191 upon inflammasome activation, and only palmitoylated GSDMD N-terminal domain (GSDMD-NT) is capable of membrane translocation and pore formation. Thus, GSDMD palmitoylation is induced by ROS and required for pore formation (Du et al. 2023).  Brain endothelial GSDMD activation mediates inflammatory BBB breakdown (Wei et al. 2024).