REVIEWS Channelling inflammation: gasdermins in physiology and disease Xing Liu 1,5 ✉ , Shiyu Xia 2,3,5, Zhibin Zhang2,4,5, Hao Wu 2,3 ✉ and Judy Lieberman 2,4 ✉ Abstract | Gasdermins were recently identified as the mediators of pyroptosis — inflammatory cell death triggered by cytosolic sensing of invasive infection and danger signals. Upon activation, gasdermins form cell membrane pores, which release pro-inflammatory cytokines and alarmins and damage the integrity of the cell membrane. Roles for gasdermins in autoimmune and inflammatory diseases, infectious diseases, deafness and cancer are emerging, revealing potential novel therapeutic avenues. Here, we review current knowledge of the family of gasdermins, focusing on their mechanisms of action and roles in normal physiology and disease. Efforts to develop drugs to modulate gasdermin activity to reduce inflammation or activate more potent immune responses are highlighted. Gasdermins 8–11 Gasdermins (GSDMs) are a recently characterized pro- and forms pores . In the full-length protein, the CT A family of homologous tein family encoded by six paralogous genes: GSDMA, domain folds back on the NT domain to auto-inhibit pore-forming proteins GSDMB, GSDMC, GSDMD, GSDME (also known pore formation9,12. GSDM cleavage in the linker region whose N-terminal fragments as DFNA5) and DFNB59 (also known as pejvakin)1. liberates the active, pore-forming NT domain. GSDMD permeabilize cell membranes when the protein is cleaved Proteolytic cleavage of the GSDMs liberates an N-terminal is the most studied GSDM as it is the key executioner in the linker region connecting (NT) fragment, which can assemble in membranes to of inflammasome-induced pyroptosis and is probably the the active N-terminal and form pores (verified for most, but not all, of the family). most important GSDM mediating disease-associated inhibitory C-terminal domains. GSDM pores can disrupt cell membrane integrity to trig- inflammation. GSDMD cleavage and pyroptosis are ger an inflammatory cell death in which cellular contents, activated when cytosolic danger and infection sen- including inflammatory cytokines, are released into the sors in macrophages and dendritic cells assemble into 1The Center for Microbes, 2–4 (BOX 1; FIGS 1,2) Development and Health, extracellular space . GSDM-mediated large supramolecular complexes called inflammasomes 13–15 Key Laboratory of Molecular cell death is termed pyroptosis (fiery death). that recruit and activate inflammatory caspases . The Virology and Immunology, The name ‘gasdermin’ comes from GSDM expression inflammatory caspases activate GSDMD by cleaving after Institut Pasteur of Shanghai, in the gastroinstestinal tract and skin. Individual GSDMs Asp275 (mouse Asp276) in the linker13,14. By contrast, Chinese Academy of Sciences, apoptosis (BOx 2) Shanghai, China. are selectively expressed with varying abundance wher- GSDME is activated during classical , by ever the body encounters, detects and responds to caspase 3 cleavage after Asp270, which converts nonin- 2Program in Cellular and 3,5 Molecular Medicine, Boston infection , being predominantly expressed in specific flammatory apoptotic death into inflammatory pyroptotic 16,17 Children’s Hospital, Boston, mucosal sites (TABle 1). GSDMA is found in skin and death in cells that express GSDME . Granzymes (Gzms) MA, USA. the gastrointestinal tract, GSDMB is located in the lung, A and B, death-inducing proteases in natural killer (NK) 3Department of Biological oesophagus, gastrointestinal tract and immune cells, cells and cytotoxic T lymphocytes (CTLs), also cleave Chemistry and Molecular GSDMC is found in keratinocytes and the gastrointes- GSDMB and GSDME, respectively, to activate pyropto- Pharmacology, Harvard tinal tract, and GSDMD is found in the gastrointestinal sis during killer cell attack, which was previously thought Medical School, Boston, 18,19 MA, USA. epithelia and in the sentinel cells of the immune sys- of as noninflammatory . A recent study showed that 3 4Department of Pediatrics, tem, macrophages and dendritic cells . GSDME has a GSDMC can be cleaved by caspase 8 after TNF-mediated 20 Harvard Medical School, different pattern of expression in mesenchymal cells — death receptor signalling to trigger pyroptosis . How Boston, MA, USA. muscle (both skeletal and cardiac), central nervous GSDMA is activated is currently unknown. 5These authors contributed system (CNS) and placenta6. The physiological role of GSDM pores in the plasma membrane act as chan- equally: Xing Liu, Shiyu Xia, GSDME in these tissues, where inflammation might be nels through which low-molecular-weight cellular con- Zhibin Zhang. harmful, is not entirely clear, although it may be involved tents are released into the extracellular space to initiate ✉e-mail: [email protected]; in development7. inflammation (FIG. 2). Importantly, the pores mediate the [email protected]; pro-inflammatory judy.lieberman@ GSDMs A–E share highly conserved NT and ‘unconventional protein secretion’ of the childrens.harvard.edu C-terminal (CT) domains separated by a variable linker cytokines (IL-1β and IL-18) that lack a signal peptide https://doi.org/10.1038/ (FIG. 3a). The NT domain of GSDMs binds to acidic for secretion via the endoplasmic reticulum to Golgi s41573-021-00154-z phospholipids in the inner leaflet of cell membranes secretory pathway21. Cellular alarmins, including ATP 384 | MAY 2021 | VOLUME 20 www.nature.com/nrd 0123456789();: REVIEWS Pyroptosis and HMGB1, cleaved GSDMs and other cytokines and This Review encapsulates our current understanding A programmed inflammatory chemokines, are released at the same time to amplify of the expression, activation and regulation of GSDMs cell death, which occurs after inflammation in the tissue and recruit immune cells to and highlights their important physiological and patho- the cleavage and activation of respond to the infection or damage. Many small mole- logical roles as perpetrators of cell death, cytokine a gasdermin, leading to loss of cell membrane integrity and cules and other proteins, which may differ between cell secretion and inflammation. Emerging opportunities release of pro-inflammatory types, are probably released from pyroptotic cells. Pore to develop GSDM-targeted drugs, particularly GSDMD cytokines and cellular proteins formation triggers rapid pyroptotic cell death in which inhibitors, and the associated challenges, are discussed. that can act as danger signals. the damaged membrane forms large ballooning bubbles and dying cells appear to flatten as their cytoplasmic con- The gasdermin family Inflammasome 22 Intracellular complex of tents are released . Both the rapidity of cell death and Humans have six GSDM genes: GSDMA, GSDMB, cytosolic sensors of invasive the morphological changes are hallmarks that distinguish GSDMC, GSDMD, GSDME and DFNB59 (TABLe 1; FIG. 1). infection that recognize pyroptotic from apoptotic cell death3. In some circum- GSDME on human chromosome 7p15.3 is the most pathogen-associated molecular stances, GSDM-mediated cell membrane damage can ancient gene with orthologues found in early metazoa patterns (PAMPs) or of danger 17,50,51 that recognize damage- be repaired by the ubiquitous damaged cell membrane and invertebrates . The other GSDM genes likely associated molecular patterns repair response — the cell survives but inflammatory arose as gene duplications — GSDMA and GSDMB on (DAMPs) and then assemble mediators are released through GSDM pores before the human chromosome 17q21 and GSDMC and GSDMD into supramolecular complexes pores are removed from the membrane23. Macrophages on human chromosome 8q2. Although in metazoa that activate inflammatory that survive despite GSDMD cleavage have been termed DFNB59 is not truncated and is closely homologous to caspases; the canonical inflammasome activates ‘hyperactivated’, because they both stimulate inflam- GSDME, mammalian DFNB59 is a more distant and trun- caspase 1 and the noncanonical mation and preserve their other antigen-presenting cated gene, whose N terminus is homologous to the NT, inflammasome activates functions24. pore-forming region of the other family members, but caspase 4 or caspase 5 in The diverse physiological and pathological roles of whether it possesses pore-forming activity is unknown. humans or caspase 11 in mice. GSDMs as executioners of pyroptosis are still being Mice lack a GSDMB orthologue, but have one Gsdmd Inflammatory caspases uncovered. However, associations of GSDMs with sev- on chromosome 15, one Gsdme on chromosome 6 and Cysteine proteases that are eral diseases have emerged. GSDMD has been implicated three Gsdmas (Gsdma1–3) and four Gsdmcs (Gsdmc1–4) activated by proximity-induced in the pathogenesis of many inflammasome-associated clustered on chromosomes 11D and 15D1, respectively1. autocatalytic cleavage when diseases and tissue damage14,25,26. In addition, sponta- Although published studies and web-based gene they dimerize after recruitment to canonical (caspase 1) or neous mutations of GSDMs lead to disorders such as expression atlases are available for GSDM expression, 27–31 32 noncanonical (caspase 4, 5 alopecia (GSDMA) , asthma (GSDMB) and hear- these resources are inadequate for accurately predicting or 11) inflammasomes and ing impairment (GSDME/DFNB59)6,33–39 in mice and/or GSDM expression, which can be induced by cytokines are responsible for processing humans. Moreover, accumulating evidence suggests that and immune signalling in cells that are not ordinarily inflammatory cytokines