Project description:Pyroptosis—inflammatory cell death mediated by gasdermins (GSDM)—plays crucial roles in antimicrobial defense and inflammatory diseases. Pyroptosis results in the release of proinflammatory molecules, including damage-associated molecular patterns (DAMPs). However, our understanding of the consequences of pyroptosis—especially beyond IL-1 cytokines and DAMPs—that govern inflammation is limited. Here, we show intercellular propagation of pyroptosis from dying cells to bystander cells in vitro and in vivo. We identified extracellular vesicles (EVs) released by pyroptosing cells as the propagator of lytic death to naïve cells, triggering inflammatory responses and tissue damage. Remarkably, DNA-PAINT super-resolution and immunoelectron microscopical analyses revealed the presence of GSDMD nanostructures, such as pores, on EVs released by pyroptotic cells. Importantly, the transplantation of these GSDMD pores on adjacent cells’ plasma membrane by EVs causes cell-extrinsic lysis of bystanders. Overall, our findings demonstrate that cell-to-cell vesicular transplantation of GSDMD pores disseminates pyroptosis, revealing a domino-like effect shaping disease-associated bystander cell death.
Project description:The process of pyroptosis is mediated by inflammasomes and a downstream effector known as gasdermin D (GSDMD). Upon cleavage by inflammasome-associated caspases, the N-terminal domain of GSDMD forms membrane pores that promote cytolysis. Numerous proteins promote GSDMD cleavage, but none are known to be required for pore formation after GSDMD cleavage. Herein, we report a forward genetic screen that identified the Ragulator-Rag complex as being necessary for GSDMD pore formation and pyroptosis in macrophages. Mechanistic analysis revealed that Ragulator-Rag is not required for GSDMD cleavage upon inflammasome activation, but rather promotes GSDMD oligomerization in the plasma membrane. Defects in GSDMD oligomerization and pore formation can be rescued by mitochondrial poisons that stimulate reactive oxygen species (ROS) production, and ROS modulation impacts the ability of inflammasome pathways to promote pore formation downstream of GSDMD cleavage. These findings reveal an unexpected link between key regulators of immunity (inflammasome-GSDMD) and metabolism (Ragulator-Rag).
Project description:Cell death plays a critical role in inflammatory responses. During pyroptosis, inflammatory caspases cleave Gasdermin D (GSDMD) to release an N-terminal fragment that generates plasma membrane pores that mediate cell lysis and IL-1 release. However, certain stimuli and cell types release IL-1 cytokines through GSDMD pores in cells that remain viable, a process termed hyperactivation. How these distinct cell fate choices are regulated downstream of GSDMD pore formation is unknown. Here, we demonstrate that the Card19 locus promotes lysis downstream of caspase activation. Despite being largely protected from cell death, CARD19-deficient macrophages had no defect in caspase activation, IL-1 secretion, or GSDMD cleavage. CARD19, a mitochondrial protein, was not responsible for the observed phenotypes, nor was the recently identified pore forming protein NINJ1 which regulates terminal pore formation during multiple forms of cell death. Furthermore, previously identified cell death phenotypes attributed to Sterile alpha and heat Armadillo motif-containing protein (SARM) were revealed to be caused by a passenger mutation. Importantly, Card19-/ mice had increased susceptibility to Yersinia infection, including increased mortality, higher bacterial burdens and pronounced splenomegaly. These findings implicate the Card19 locus as a factor that couples caspase processing and GSDMD cleavage to cell death, providing insight into how the checkpoint between hyperactivation and cell death is regulated.
Project description:Gasdermin D (GSDMD) is the executioner of pyroptosis, which is important for host defense against pathogen infection. After activation, caspase-mediated cleavage of GSDMD liberates an N-terminal fragment (GSDMD-NT), which oligomerizes and forms pores in the plasma membrane, leading to cell death and subsequent release of proinflammatory cytokines. How this process is spatiotemporally controlled to promote pyroptosis in cells has been a fundamental, unaddressed question. Here, we identify GSDMD as a substrate for reversible S-palmitoylation on cysteine 192 (Cys192) in response to lipopolysaccharide (LPS) stimulation. We found that the palmitoyl acyltransferase DHHC7palmitoylates GSDMD to direct its cleavage by caspases in pyroptosis by promoting the interaction of GSDMD and caspases. We further show that after GSDMD cleavage, palmitoylation of GSDMD-NTpromotes its plasma membrane translocation and binding, and then acyl protein thioesterase 2 (APT2) depalmitoylates GSDMD-NT to unmask the Cys192 residue to promote oxidation-mediated oligomerization and pyroptosis. Perturbation of either palmitoylation or depalmitoylation suppresses pyroptosis, extends the survival of mice from LPS-induced lethal septic shock and sensitizes mice to bacterial infection. Thus. our findings reveal a model through which a palmitoylation-depalmitoylationrelay spatially and temporally controls GSDMD activation in pyroptosis.
Project description:Gasdermin D (GSDMD) is the executioner of pyroptosis, which is important for host defense against pathogen infection. After activation, caspase-mediated cleavage of GSDMD liberates an N-terminal fragment (GSDMD-NT), which oligomerizes and forms pores in the plasma membrane, leading to cell death and subsequent release of proinflammatory cytokines. How this process is spatiotemporally controlled to promote pyroptosis in cells has been a fundamental, unaddressed question. Here, we identify GSDMD as a substrate for reversible S-palmitoylation on cysteine 192 (Cys192) in response to lipopolysaccharide (LPS) stimulation. We found that the palmitoyl acyltransferase DHHC7palmitoylates GSDMD to direct its cleavage by caspases in pyroptosis by promoting the interaction of GSDMD and caspases. We further show that after GSDMD cleavage, palmitoylation of GSDMD-NTpromotes its plasma membrane translocation and binding, and then acyl protein thioesterase 2 (APT2) depalmitoylates GSDMD-NT to unmask the Cys192 residue to promote oxidation-mediated oligomerization and pyroptosis. Perturbation of either palmitoylation or depalmitoylation suppresses pyroptosis, extends the survival of mice from LPS-induced lethal septic shock and sensitizes mice to bacterial infection. Thus. our findings reveal a model through which a palmitoylation-depalmitoylationrelay spatially and temporally controls GSDMD activation in pyroptosis.
Project description:Alcoholic hepatitis (AH) continues to be a disease with high mortality and no efficacious medical treatment. Although severe AH is presented as acute on chronic liver failure, what underlies this transition from chronic alcoholic steatohepatitis (ASH) to AH, is largely unknown. To address this question, unbiased RNA-seq and proteomic analyses were performed on livers of the recently developed AH mouse model which exhibits the shift to AH from chronic ASH upon weekly alcohol binge, and these results are compared with gene expression profiling data from AH patients. This cross-analysis has identified Casp11 (CASP4 in man) as a commonly upregulated gene known to be involved in non-canonical inflammasome pathway. Immunoblotting confirms CASP11/4 activation in AH mice but not in chronic ASH. Gasdermin-D (GSDMD) which induces pyroptosis (lytic cell death caused by bacterial infection) downstream of CASP11/4 activation, is also activated in AH livers. CASP11 deficiency reduces GSDMD activation, bacterial load in the liver, and the severity of AH. Conversely, the deficiency of IL-18, the key anti-microbial cytokine, aggravates hepatic bacterial load, GSDMD activation, and AH. Further, hepatocyte-specific expression of constitutively active GSDMD worsens hepatocellular lytic death and PMN inflammation. These results implicate pyroptosis induced by CASP11/4-GSDMD pathway in the pathogenesis of AH.
Project description:Pyroptosis is a recently discovered form of lytic cell death that is characterized by cell swelling and formation of pores and large bubbles on the plasma membrane. We find radiation could induce pyroptosis in human colorectal cancer HCT116 cells, and irradiation induces pyroptosis in mouse normal intestine MODEK cells only after 36 hours and over 8.0 Gy. In view of the significant pyroptosis effect of MODE-K cells, we selected 4Gy and 12Gy, 24h and 48h for experiments. After ONT full-length transcriptome sequencing, the cell pyroptosis model can screen out the differential genes related to cell pyroptosis, which is helpful to further explore the mechanism of pyroptosis of MODE-K cells.
Project description:Inflammatory caspases (caspases 1, 4, 5 and 11) are activated in response to microbial infection and danger signals. When activated, they cleave mouse and human gasdermin D (GSDMD) after Asp276 and Asp275, respectively, to generate an N-terminal cleavage product (GSDMD-NT) that triggers inflammatory death (pyroptosis) and release of inflammatory cytokines such as interleukin-1β. Cleavage removes the C-terminal fragment (GSDMD-CT), which is thought to fold back on GSDMD-NT to inhibit its activation. However, how GSDMD-NT causes cell death is unknown. Here we show that GSDMD-NT oligomerizes in membranes to form pores that are visible by electron microscopy. GSDMD-NT binds to phosphatidylinositol phosphates and phosphatidylserine (restricted to the cell membrane inner leaflet) and cardiolipin (present in the inner and outer leaflets of bacterial membranes). Mutation of four evolutionarily conserved basic residues blocks GSDMD-NT oligomerization, membrane binding, pore formation and pyroptosis. Because of its lipid-binding preferences, GSDMD-NT kills from within the cell, but does not harm neighbouring mammalian cells when it is released during pyroptosis. GSDMD-NT also kills cell-free bacteria in vitro and may have a direct bactericidal effect within the cytosol of host cells, but the importance of direct bacterial killing in controlling in vivo infection remains to be determined.