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 mediate inflammatory cell death after cleavage by caspases or other, unknown enzymes. The cleaved N-terminal fragments bind to acidic membrane lipids to form pores, but the mechanism of ...pore formation remains unresolved. Here we present the cryo-electron microscopy structures of the 27-fold and 28-fold single-ring pores formed by the N-terminal fragment of mouse GSDMA3 (GSDMA3-NT) at 3.8 and 4.2 Å resolutions, and of a double-ring pore at 4.6 Å resolution. In the 27-fold pore, a 108-stranded anti-parallel β-barrel is formed by two β-hairpins from each subunit capped by a globular domain. We identify a positively charged helix that interacts with the acidic lipid cardiolipin. GSDMA3-NT undergoes radical conformational changes upon membrane insertion to form long, membrane-spanning β-strands. We also observe an unexpected additional symmetric ring of GSDMA3-NT subunits that does not insert into the membrane in the double-ring pore, which may represent a pre-pore state of GSDMA3-NT. These structures provide a basis that explains the activities of several mutant gasdermins, including defective mutants that are associated with cancer.
Cytosolic sensing of pathogens and damage by myeloid and barrier epithelial cells assembles large complexes called inflammasomes, which activate inflammatory caspases to process cytokines (IL-1β) and ...gasdermin D (GSDMD). Cleaved GSDMD forms membrane pores, leading to cytokine release and inflammatory cell death (pyroptosis). Inhibiting GSDMD is an attractive strategy to curb inflammation. Here we identify disulfiram, a drug for treating alcohol addiction, as an inhibitor of pore formation by GSDMD but not other members of the GSDM family. Disulfiram blocks pyroptosis and cytokine release in cells and lipopolysaccharide-induced septic death in mice. At nanomolar concentration, disulfiram covalently modifies human/mouse Cys191/Cys192 in GSDMD to block pore formation. Disulfiram still allows IL-1β and GSDMD processing, but abrogates pore formation, thereby preventing IL-1β release and pyroptosis. The role of disulfiram in inhibiting GSDMD provides new therapeutic indications for repurposing this safe drug to counteract inflammation, which contributes to many human diseases.
Limited proteolysis of gasdermin D (GSDMD) generates an N-terminal pore-forming fragment that controls pyroptosis in macrophages. GSDMD is processed via inflammasome-activated caspase-1 or -11. It is ...currently unknown whether macrophage GSDMD can be processed by other mechanisms. Here, we describe an additional pathway controlling GSDMD processing. The inhibition of TAK1 or IκB kinase (IKK) by the
effector protein YopJ elicits RIPK1- and caspase-8-dependent cleavage of GSDMD, which subsequently results in cell death. GSDMD processing also contributes to the NLRP3 inflammasome-dependent release of interleukin-1β (IL-1β). Thus, caspase-8 acts as a regulator of GSDMD-driven cell death. Furthermore, this study establishes the importance of TAK1 and IKK activity in the control of GSDMD cleavage and cytotoxicity.
The interleukin-1 (IL-1) family cytokines are cytosolic proteins that exhibit inflammatory activity upon release into the extracellular space. These factors are released following various cell death ...processes, with pyroptosis being a common mechanism. Recently, it was recognized that phagocytes can achieve a state of hyperactivation, which is defined by their ability to secrete IL-1 while retaining viability, yet it is unclear how IL-1 can be secreted from living cells. Herein, we report that the pyroptosis regulator gasdermin D (GSDMD) was necessary for IL-1β secretion from living macrophages that have been exposed to inflammasome activators, such as bacteria and their products or host-derived oxidized lipids. Cell- and liposome-based assays demonstrated that GSDMD pores were required for IL-1β transport across an intact lipid bilayer. These findings identify a non-pyroptotic function for GSDMD, and raise the possibility that GSDMD pores represent conduits for the secretion of cytosolic cytokines under conditions of cell hyperactivation.
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•Multiple microbial and self-derived stimuli induce IL-1 release from living macrophages•Inflammasomes can be detected within cells that display multiple signs of viability•Living macrophages require gasdermin D to induce pore formation and IL-1 release•Gasdermin D pores facilitate the release of IL-1 from liposomes and intact cells
Inflammasomes elicit pyroptosis or cell hyperactivation, with the latter defined as living cells that release IL-1. Evavold et al report that the pore-forming protein gasdermin D regulates IL-1 release from hyperactive macrophages. Cell- and liposome-based assays revealed that gasdermin D pores permit IL-1 passage across intact lipid bilayers.
•Helical assembly of PYD and CARD is revealed as one universal mechanism for inflammasome signaling by cryo-EM.•Cryo-EM facilitates the understanding of disk-like, self-propagating assembly of the ...NLRC4 inflammasome.•The cryo-EM structure of a gasdermin (GSDM) pore uncovers the molecular details of membrane insertion, providing a novel mechanism for cytokine secretion and pyroptosis execution.
The innate immune system forms an evolutionarily ancient line of defense against invading pathogens and endogenous danger signals. Within certain cells of innate immunity, including epithelial cells and macrophages, intricate molecular machineries named inflammasomes sense a wide array of stimuli to mount inflammatory responses. Dysregulation in inflammasome signaling leads to a wide range of immune disorders such as gout, Crohn’s disease, and sepsis. Recent technological advances in cryo-electron microscopy (cryo-EM) have enabled the structural determination of several key signaling molecules in inflammasome pathways, from which macromolecular assembly emerges as a common mechanistic theme. Through the assembly of helical filaments, symmetric disks, and transmembrane pores, inflammasome pathways employ highly dynamic yet ordered processes to relay and amplify signals. These unprecedentedly detailed views of inflammasome signaling not only revolutionize our understanding of inflammation, but also pave the way for the development of therapeutics against inflammatory diseases.
Innate immunity enables host defense against pathogens and endogenous danger through inflammasomes, which are supramolecular complexes that recognize the threats and activate the immune response. ...Inflammasome activation often leads to pyroptosis, a highly inflammatory and lytic form of cell death, as a means of killing infected cells and releasing IL-1 family cytokines that communicate with other cells. Dysregulated inflammasome signaling results in a wide range of immune disorders including gout, sepsis, and hepatitis. Discovered as a direct killer molecule in pyroptosis, gasdermin D (GSDMD) is a pore-forming protein that represents a novel family with diverse cellular functions and pathological roles. This review summarizes current opinions in the biological mechanisms and therapeutic values of the GSDM family, particularly of GSDMD. Detailed mechanisms of auto-inhibition and pore formation by the GSDM family are presented, followed by a brief summary of the progress in the development of GSDM-targeting therapeutics.
Signaling pathways in innate and adaptive immunity play vital roles in pathogen recognition and the functions of immune cells. Higher-order assemblies have recently emerged as a central principle ...that governs immune signaling and, by extension, cellular communication in general. There are mainly two types of higherorder assemblies: 1) ordered, solid-like large supramolecular complexes formed by stable and rigid protein-protein interactions, and 2) liquid-like phaseseparated condensates formed by weaker and more dynamic intermolecular interactions. This review covers key examples of both types of higher-order assemblies in major immune pathways. By placing emphasis on the molecular structures of the examples provided, we discuss how their structural organization enables elegant mechanisms of signaling regulation.
Introduction
Group information-guided independent component analysis (GIG-ICA) and independent vector analysis (IVA) are two methods that improve estimation of subject-specific independent components ...in neuroimaging studies. These methods have shown better performance than traditional group independent component analysis (GICA) with respect to intersubject variability (ISV).
Methods
In this study, we compared the patterns of community structure, spatial variance, and prediction performance of GIG-ICA and IVA-GL, respectively. The dataset was obtained from the publicly available Autism Brain Imaging Data Exchange (ABIDE) database, comprising 75 healthy controls (HC) and 102 Autism Spectrum Disorder (ASD) participants. The greedy rule was used to match components from IVA-GL and GIG-ICA in order to compare the similarities between the two methods.
Results
Robust correspondence was observed between the two methods the following networks: cerebellum network (CRN; |
r
| = 0.7813), default mode network (DMN; |
r
| = 0.7263), self-reference network (SRN; |
r
| = 0.7818), ventral attention network (VAN; |
r
| = 0.7574), and visual network (VSN; |
r
| = 0.7503). Additionally, the Sensorimotor Network demonstrated the highest similarity between IVA-GL and GIG-ICA (SOM: |
r
| = 0.8125). Our findings revealed a significant difference in the number of modules identified by the two methods (HC:
p
< 0.001; ASD:
p
< 0.001). GIG-ICA identified significant differences in FNC between HC and ASD compared to IVA-GL. However, in correlation analysis, IVA-GL identified a statistically negative correlation between FNC of ASD and the social total subscore of the classic Autism Diagnostic Observation Schedule (ADOS: pi = −0.26,
p
= 0.0489). Moreover, both methods demonstrated similar prediction performances on age within specific networks, as indicated by GIG-ICA-CRN (
R
2
= 0.91, RMSE = 3.05) and IVA-VAN (
R
2
= 0.87, RMSE = 3.21).
Conclusion
In summary, IVA-GL demonstrated lower modularity, suggesting greater sensitivity in estimating networks with higher intersubject variability. The improved age prediction of cerebellar-attention networks underscores their importance in the developmental progression of ASD. Overall, IVA-GL may be appropriate for investigating disorders with greater variability, while GIG-ICA identifies functional networks with distinct modularity patterns.
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