ABSTRACT
Interferon (IFN)-Is are crucial mediators of antiviral immunity and homeostatic immune system regulation. However, the source of IFN-I signaling under homeostatic conditions is unclear. We discovered that commensal microbes regulate the IFN-I response through induction of IFN-ß by colonic DCs. Moreover, the mechanism by which a specific commensal microbe induces IFN-ß was identified. Outer membrane (OM)-associated glycolipids of gut commensal microbes belonging to the Bacteroidetes phylum induce expression of IFN-ß. Using Bacteroides fragilis and its OM-associated polysaccharide A, we determined that IFN-ß expression was induced via TLR4-TRIF signaling. Antiviral activity of this purified microbial molecule against infection with either vesicular stomatitis virus (VSV) or influenza was demonstrated to be dependent on the induction of IFN-ß. In a murine VSV infection model, commensal-induced IFN-ß regulated natural resistance to virus infection. Due to the physiological importance of IFN-Is, discovery of an IFN-ß-inducing microbial molecule represents a potential approach for the treatment of some human diseases.
Subject(s)
Immunity, Innate , Microbiota , Virus Diseases/microbiology , Animals , Bacteroides fragilis/physiology , Bone Marrow Cells/drug effects , Bone Marrow Cells/metabolism , Cell Membrane/drug effects , Cell Membrane/metabolism , Colon/pathology , Colon/virology , Dendritic Cells/drug effects , Dendritic Cells/metabolism , Female , Gene Expression Regulation/drug effects , Glycolipids/metabolism , Immunity, Innate/drug effects , Interferon-beta/blood , Interferon-beta/metabolism , Male , Mice, Inbred C57BL , Microbiota/drug effects , Polysaccharides, Bacterial/pharmacology , Toll-Like Receptor 4/metabolism , Vesiculovirus/physiology , Virus Diseases/geneticsABSTRACT
RLR-mediated type I IFN production plays a pivotal role in elevating host immunity for viral clearance and cancer immune surveillance. Here, we report that glycolysis, which is inactivated during RLR activation, serves as a barrier to impede type I IFN production upon RLR activation. RLR-triggered MAVS-RIG-I recognition hijacks hexokinase binding to MAVS, leading to the impairment of hexokinase mitochondria localization and activation. Lactate serves as a key metabolite responsible for glycolysis-mediated RLR signaling inhibition by directly binding to MAVS transmembrane (TM) domain and preventing MAVS aggregation. Notably, lactate restoration reverses increased IFN production caused by lactate deficiency. Using pharmacological and genetic approaches, we show that lactate reduction by lactate dehydrogenase A (LDHA) inactivation heightens type I IFN production to protect mice from viral infection. Our study establishes a critical role of glycolysis-derived lactate in limiting RLR signaling and identifies MAVS as a direct sensor of lactate, which functions to connect energy metabolism and innate immunity.
Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , DEAD Box Protein 58/antagonists & inhibitors , DEAD Box Protein 58/metabolism , Lactic Acid/pharmacology , Receptors, Cell Surface/antagonists & inhibitors , Receptors, Cell Surface/metabolism , Animals , Female , Glycolysis , HEK293 Cells , Humans , Interferon-beta/metabolism , L-Lactate Dehydrogenase/genetics , L-Lactate Dehydrogenase/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , RAW 264.7 Cells , Receptors, Immunologic , Signal Transduction/drug effects , TransfectionABSTRACT
Evasion of host immunity is a hallmark of cancer; however, mechanisms linking oncogenic mutations and immune escape are incompletely understood. Through loss-of-function screening of 1,001 tumor suppressor genes, we identified death-associated protein kinase 3 (DAPK3) as a previously unrecognized driver of anti-tumor immunity through the stimulator of interferon genes (STING) pathway of cytosolic DNA sensing. Loss of DAPK3 expression or kinase activity impaired STING activation and interferon (IFN)-ß-stimulated gene induction. DAPK3 deficiency in IFN-ß-producing tumors drove rapid growth and reduced infiltration of CD103+CD8α+ dendritic cells and cytotoxic lymphocytes, attenuating the response to cancer chemo-immunotherapy. Mechanistically, DAPK3 coordinated post-translational modification of STING. In unstimulated cells, DAPK3 inhibited STING K48-linked poly-ubiquitination and proteasome-mediated degradation. After cGAMP stimulation, DAPK3 was required for STING K63-linked poly-ubiquitination and STING-TANK-binding kinase 1 interaction. Comprehensive phospho-proteomics uncovered a DAPK3-specific phospho-site on the E3 ligase LMO7, critical for LMO7-STING interaction and STING K63-linked poly-ubiquitination. Thus, DAPK3 is an essential kinase for STING activation that drives tumor-intrinsic innate immunity and tumor immune surveillance.
Subject(s)
Death-Associated Protein Kinases/metabolism , Human Umbilical Vein Endothelial Cells/enzymology , Immunity, Innate , Interferon-beta/metabolism , Membrane Proteins/metabolism , Neoplasms/enzymology , Tumor Escape , Animals , Antineoplastic Combined Chemotherapy Protocols/pharmacology , Cell Line, Tumor , Death-Associated Protein Kinases/genetics , Female , Gene Expression Regulation, Neoplastic , Human Umbilical Vein Endothelial Cells/metabolism , Humans , Immune Checkpoint Inhibitors/pharmacology , Immunity, Innate/drug effects , Interferon-beta/genetics , LIM Domain Proteins/genetics , LIM Domain Proteins/metabolism , Membrane Proteins/genetics , Mice, Inbred C57BL , Mice, Knockout , Neoplasms/drug therapy , Neoplasms/genetics , Neoplasms/immunology , Phosphorylation , Signal Transduction , Transcription Factors/genetics , Transcription Factors/metabolism , Tumor Escape/drug effects , UbiquitinationABSTRACT
The innate RNA sensor RIG-I is critical in the initiation of antiviral type I interferons (IFNs) production upon recognition of "non-self" viral RNAs. Here, we identify a host-derived, IFN-inducible long noncoding RNA, lnc-Lsm3b, that can compete with viral RNAs in the binding of RIG-I monomers and feedback inactivate the RIG-I innate function at late stage of innate response. Mechanistically, binding of lnc-Lsm3b restricts RIG-I protein's conformational shift and prevents downstream signaling, thereby terminating type I IFNs production. Multivalent structural motifs and long-stem structure are critical features of lnc-Lsm3b for RIG-I binding and inhibition. These data reveal a non-canonical self-recognition mode in the regulation of immune response and demonstrate an important role of an inducible "self" lncRNA acting as a potent molecular decoy actively saturating RIG-I binding sites to restrict the duration of "non-self" RNA-induced innate immune response and maintaining immune homeostasis, with potential utility in inflammatory disease management.
Subject(s)
DEAD Box Protein 58/metabolism , Immunity, Innate , RNA, Long Noncoding/metabolism , Animals , HEK293 Cells , Humans , Interferon-alpha/metabolism , Interferon-beta/metabolism , Macrophages/cytology , Macrophages/immunology , Macrophages/virology , Mice , Mice, Inbred C57BL , Protein Binding , RAW 264.7 Cells , RNA Interference , RNA, Double-Stranded/metabolism , RNA, Long Noncoding/antagonists & inhibitors , RNA, Long Noncoding/genetics , RNA, Small Interfering/metabolism , Signal Transduction , Vesiculovirus/pathogenicityABSTRACT
Type I interferons (IFNs) are pleiotropic cytokines with potent antiviral properties that also promote protective T cell and humoral immunity. Paradoxically, type I IFNs, including the widely expressed IFNß, also have immunosuppressive properties, including promoting persistent viral infections and treating T-cell-driven, remitting-relapsing multiple sclerosis. Although associative evidence suggests that IFNß mediates these immunosuppressive effects by impacting regulatory T (Treg) cells, mechanistic links remain elusive. Here, we found that IFNß enhanced graft survival in a Treg-cell-dependent murine transplant model. Genetic conditional deletion models revealed that the extended allograft survival was Treg cell-mediated and required IFNß signaling on T cells. Using an in silico computational model and analysis of human immune cells, we found that IFNß directly promoted Treg cell induction via STAT1- and P300-dependent Foxp3 acetylation. These findings identify a mechanistic connection between the immunosuppressive effects of IFNß and Treg cells, with therapeutic implications for transplantation, autoimmunity, and malignancy.
Subject(s)
Interferon-beta , T-Lymphocytes, Regulatory , Acetylation , Allografts , Animals , Forkhead Transcription Factors/metabolism , Graft Survival , Humans , Interferon-beta/metabolism , MiceABSTRACT
Neurodegenerative diseases have been linked to inflammation, but whether altered immunomodulation plays a causative role in neurodegeneration is not clear. We show that lack of cytokine interferon-ß (IFN-ß) signaling causes spontaneous neurodegeneration in the absence of neurodegenerative disease-causing mutant proteins. Mice lacking Ifnb function exhibited motor and cognitive learning impairments with accompanying α-synuclein-containing Lewy bodies in the brain, as well as a reduction in dopaminergic neurons and defective dopamine signaling in the nigrostriatal region. Lack of IFN-ß signaling caused defects in neuronal autophagy prior to α-synucleinopathy, which was associated with accumulation of senescent mitochondria. Recombinant IFN-ß promoted neurite growth and branching, autophagy flux, and α-synuclein degradation in neurons. In addition, lentiviral IFN-ß overexpression prevented dopaminergic neuron loss in a familial Parkinson's disease model. These results indicate a protective role for IFN-ß in neuronal homeostasis and validate Ifnb mutant mice as a model for sporadic Lewy body and Parkinson's disease dementia.
Subject(s)
Interferon-beta/metabolism , Neurons/metabolism , Receptor, Interferon alpha-beta/metabolism , Animals , Autophagy , Disease Models, Animal , Genetic Therapy , Interferon-beta/genetics , Interferon-beta/therapeutic use , Lewy Body Disease/metabolism , Lewy Body Disease/pathology , Mice , Mice, Inbred C57BL , Parkinson Disease/genetics , Parkinson Disease/metabolism , Parkinson Disease/pathology , Parkinson Disease/therapy , Receptor, Interferon alpha-beta/genetics , Signal Transduction , Transcriptome , alpha-Synuclein/metabolismABSTRACT
Type I interferons (IFN-I, including IFNß) and IFNγ produce overlapping, yet clearly distinct immunological activities. Recent data show that the distinctness of global transcriptional responses to the two IFN types is not apparent when comparing their immediate effects. By analyzing nascent transcripts induced by IFN-I or IFNγ over a period of 48 h, we now show that the distinctiveness of the transcriptomes emerges over time and is based on differential employment of the ISGF3 complex as well as of the second-tier transcription factor IRF1. The distinct transcriptional properties of ISGF3 and IRF1 correspond with a largely diverse nuclear protein interactome. Mechanistically, we describe the specific input of ISGF3 and IRF1 into enhancer activation and the regulation of chromatin accessibility at interferon-stimulated genes (ISG). We further report differences between the IFN types in altering RNA polymerase II pausing at ISG 5' ends. Our data provide insight how transcriptional regulators create immunological identities of IFN-I and IFNγ.
Subject(s)
Gene Expression Regulation , Interferon Regulatory Factor-1 , Interferon-beta , Interferon-gamma , Signal Transduction , Interferon-gamma/metabolism , Interferon Regulatory Factor-1/metabolism , Interferon Regulatory Factor-1/genetics , Interferon-beta/metabolism , Interferon-beta/genetics , Humans , Interferon-Stimulated Gene Factor 3/metabolism , Interferon-Stimulated Gene Factor 3/genetics , Animals , Mice , RNA Polymerase II/metabolism , RNA Polymerase II/geneticsABSTRACT
TBK1 is essential for interferon-ß (IFN-ß) production and innate antiviral immunity. Here we identified the T cell anergy-related E3 ubiquitin ligase RNF128 as a positive regulator of TBK1 activation. RNF128 directly interacted with TBK1 through its protease-associated (PA) domain and catalyzed the K63-linked polyubiquitination of TBK1, which led to TBK1 activation, IRF3 activation and IFN-ß production. Deficiency of RNF128 expression attenuated IRF3 activation, IFN-ß production and innate antiviral immune responses to RNA and DNA viruses, in vitro and in vivo. Our study identified RNF128 as an E3 ligase for K63-linked ubiquitination and activation of TBK1 and delineated a previously unrecognized function for RNF128.
Subject(s)
Herpes Simplex/immunology , Herpesvirus 1, Human/immunology , Macrophages, Peritoneal/immunology , Protein Serine-Threonine Kinases/metabolism , Ubiquitin-Protein Ligases/metabolism , Vesicular Stomatitis/immunology , Vesiculovirus/immunology , Animals , Female , HEK293 Cells , Humans , Immunity, Innate , Interferon Regulatory Factor-3/metabolism , Interferon-beta/metabolism , Macrophages, Peritoneal/virology , Mice , Mice, Inbred C57BL , Mice, Knockout , RNA, Small Interfering/genetics , Signal Transduction/genetics , Ubiquitin-Protein Ligases/genetics , UbiquitinationABSTRACT
Innate sensing of pathogens initiates inflammatory cytokine responses that need to be tightly controlled. We found here that after engagement of Toll-like receptors (TLRs) in myeloid cells, deficient sumoylation caused increased secretion of transcription factor NF-κB-dependent inflammatory cytokines and a massive type I interferon signature. In mice, diminished sumoylation conferred susceptibility to endotoxin shock and resistance to viral infection. Overproduction of several NF-κB-dependent inflammatory cytokines required expression of the type I interferon receptor, which identified type I interferon as a central sumoylation-controlled hub for inflammation. Mechanistically, the small ubiquitin-like modifier SUMO operated from a distal enhancer of the gene encoding interferon-ß (Ifnb1) to silence both basal and stimulus-induced activity of the Ifnb1 promoter. Therefore, sumoylation restrained inflammation by silencing Ifnb1 expression and by strictly suppressing an unanticipated priming by type I interferons of the TLR-induced production of inflammatory cytokines.
Subject(s)
Disease Resistance , Gene Expression Regulation , Immunity, Innate , Immunomodulation , Inflammation/genetics , Inflammation/immunology , Inflammation/metabolism , Sumoylation , Animals , Chromatin/genetics , Chromatin/metabolism , Cytokines/metabolism , Dendritic Cells/immunology , Dendritic Cells/metabolism , Disease Models, Animal , Disease Susceptibility , Enhancer Elements, Genetic , Gene Expression Profiling , Genetic Loci , Inflammation/virology , Inflammation Mediators/metabolism , Interferon-beta/metabolism , Lipopolysaccharides/immunology , Mice , Mice, Knockout , Protein Binding , Receptor, Interferon alpha-beta/metabolism , Regulatory Elements, Transcriptional , SUMO-1 Protein/metabolism , Shock, Septic/genetics , Shock, Septic/immunology , Shock, Septic/metabolism , Signal Transduction , Sumoylation/genetics , Sumoylation/immunology , Toll-Like Receptors/metabolismABSTRACT
Sepsis is a bi-phasic inflammatory disease that threatens approximately 30 million lives and claims over 14 million annually, yet little is known regarding the molecular switches and pathways that regulate this disease. Here, we have described ABCF1, an ATP-Binding Cassette (ABC) family member protein, which possesses an E2 ubiquitin enzyme activity, through which it controls the Lipopolysaccharide (LPS)- Toll-like Receptor-4 (TLR4) mediated gram-negative insult by targeting key proteins for K63-polyubiquitination. Ubiquitination by ABCF1 shifts the inflammatory profile from an early phase MyD88-dependent to a late phase TRIF-dependent signaling pathway, thereby regulating TLR4 endocytosis and modulating macrophage polarization from M1 to M2 phase. Physiologically, ABCF1 regulates the shift from the inflammatory phase of sepsis to the endotoxin tolerance phase, and modulates cytokine storm and interferon-ß (IFN-ß)-dependent production by the immunotherapeutic mediator, SIRT1. Consequently, ABCF1 controls sepsis induced mortality by repressing hypotension-induced renal circulatory dysfunction.
Subject(s)
ATP-Binding Cassette Transporters/immunology , Macrophages/immunology , Sepsis/immunology , Shock, Septic/immunology , Ubiquitin-Conjugating Enzymes/immunology , ATP-Binding Cassette Transporters/genetics , ATP-Binding Cassette Transporters/metabolism , Adenosine Triphosphate/immunology , Adenosine Triphosphate/metabolism , Animals , Cytokines/immunology , Cytokines/metabolism , Female , Interferon-beta/immunology , Interferon-beta/metabolism , Lipopolysaccharides/administration & dosage , Lipopolysaccharides/immunology , Macrophage Activation/drug effects , Macrophage Activation/genetics , Macrophage Activation/immunology , Macrophages/classification , Macrophages/metabolism , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , RNA Interference , Sepsis/genetics , Sepsis/metabolism , Shock, Septic/genetics , Shock, Septic/metabolism , Signal Transduction/drug effects , Signal Transduction/genetics , Signal Transduction/immunology , Toll-Like Receptor 4/immunology , Toll-Like Receptor 4/metabolism , Ubiquitin-Conjugating Enzymes/genetics , Ubiquitin-Conjugating Enzymes/metabolism , Ubiquitination/immunologyABSTRACT
The execution of shock following high dose E. coli lipopolysaccharide (LPS) or bacterial sepsis in mice required pro-apoptotic caspase-8 in addition to pro-pyroptotic caspase-11 and gasdermin D. Hematopoietic cells produced MyD88- and TRIF-dependent inflammatory cytokines sufficient to initiate shock without any contribution from caspase-8 or caspase-11. Both proteases had to be present to support tumor necrosis factor- and interferon-ß-dependent tissue injury first observed in the small intestine and later in spleen and thymus. Caspase-11 enhanced the activation of caspase-8 and extrinsic cell death machinery within the lower small intestine. Neither caspase-8 nor caspase-11 was individually sufficient for shock. Both caspases collaborated to amplify inflammatory signals associated with tissue damage. Therefore, combined pyroptotic and apoptotic signaling mediated endotoxemia independently of RIPK1 kinase activity and RIPK3 function. These observations bring to light the relevance of tissue compartmentalization to disease processes in vivo where cytokines act in parallel to execute diverse cell death pathways.
Subject(s)
Caspase 8/metabolism , Caspases/metabolism , Escherichia coli Infections/enzymology , Escherichia coli Infections/physiopathology , Shock, Septic/enzymology , Shock, Septic/physiopathology , Animals , Apoptosis , Apoptosis Regulatory Proteins/metabolism , Caspase 8/genetics , Caspases/genetics , Caspases, Initiator , Cells, Cultured , Female , Inflammation/metabolism , Inflammation/pathology , Interferon Regulatory Factor-3/genetics , Interferon-beta/blood , Interferon-beta/metabolism , Intestine, Small/pathology , Intracellular Signaling Peptides and Proteins , Lipopolysaccharides/toxicity , Male , Mice, Inbred C57BL , Mice, Knockout , Phosphate-Binding Proteins , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Signal Transduction , Spleen/pathology , Tumor Necrosis Factor-alpha/antagonists & inhibitors , Tumor Necrosis Factor-alpha/blood , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Major 5'-terminally deleted (5'TD) RNA forms of group-B coxsackievirus (CVB-5'TD) has been associated with myocarditis in both mice and humans. Although it is known that interferon-ß (IFN-ß) signaling is critical for an efficient innate immune response against CVB-induced myocarditis, the link between CVB-5'TD RNA forms and type I IFN signaling in cardiomyocytes remains to be explored. In a mouse model of CVB3/28-induced myocarditis, major early-emerging forms of CVB-5'TD RNA have been characterized as replicative viral populations that impair IFN-ß production in the heart. Synthetic CVB3/28 RNA forms mimicking each of these major 5'TD virus populations were transfected in mice and have been shown to modulate innate immune responses in the heart and to induce myocarditis in mice. Remarkably, transfection of synthetic viral RNA with deletions in the secondary structures of the 5'-terminal CVB3 RNA domain I, modifying stem-loops "b", "c" or "d", were found to impair IFN-ß production in human cardiomyocytes. In addition, the activation of innate immune response by Poly(I:C), was found to restore IFN-ß production and to reduce the burden of CVB-5'TD RNA-forms in cardiac tissues, thereby reducing the mortality rate of infected mice. Overall, our results indicate that major early-emerging CVB3 populations deleted in the domain I of genomic RNA, in the 5' noncoding region, modulate the activation of the type I IFN pathway in cardiomyocytes and induce myocarditis in mice. These findings shed new light on the role of replicative CVB-5'TD RNA forms as key pathophysiological factors in CVB-induced human myocarditis.
Subject(s)
Coxsackievirus Infections , Enterovirus B, Human , Interferon Type I , Myocarditis , Myocytes, Cardiac , RNA, Viral , Myocarditis/virology , Myocarditis/immunology , Myocarditis/genetics , Animals , Myocytes, Cardiac/virology , Myocytes, Cardiac/metabolism , Mice , Enterovirus B, Human/immunology , Coxsackievirus Infections/immunology , Coxsackievirus Infections/virology , Coxsackievirus Infections/genetics , Interferon Type I/metabolism , RNA, Viral/genetics , RNA, Viral/metabolism , Humans , Immunity, Innate , Signal Transduction , Interferon-beta/metabolism , Interferon-beta/genetics , Interferon-beta/immunology , Male , 5' Untranslated RegionsABSTRACT
While macrophage is one of the major type I interferon (IFN-I) producers in multiple tissues during viral infections, it also serves as an important target cell for many RNA viruses. However, the regulatory mechanism for the IFN-I response of macrophages to respond to a viral challenge is not fully understood. Here we report ADAP, an immune adaptor protein, is indispensable for the induction of the IFN-I response of macrophages to RNA virus infections via an inhibition of the conjugation of ubiquitin-like ISG15 (ISGylation) to RIG-I. Loss of ADAP increases RNA virus replication in macrophages, accompanied with a decrease in LPS-induced IFN-ß and ISG15 mRNA expression and an impairment in the RNA virus-induced phosphorylation of IRF3 and TBK1. Moreover, using Adap-/- mice, we show ADAP deficiency strongly increases the susceptibility of macrophages to RNA-virus infection in vivo. Mechanically, ADAP selectively interacts and functionally cooperates with RIG-I but not MDA5 in the activation of IFN-ß transcription. Loss of ADAP results in an enhancement of ISGylation of RIG-I, whereas overexpression of ADAP exhibits the opposite effect in vitro, indicating ADAP is detrimental to the RNA virus-induced ISGylation of RIG-I. Together, our data demonstrate a novel antagonistic activity of ADAP in the cell-intrinsic control of RIG-I ISGylation, which is indispensable for initiating and sustaining the IFN-I response of macrophages to RNA virus infections and replication.
Subject(s)
Adaptor Proteins, Signal Transducing , DEAD Box Protein 58 , Interferon Type I , Macrophages , Mice, Knockout , RNA Virus Infections , Ubiquitins , Animals , Macrophages/virology , Macrophages/metabolism , Macrophages/immunology , Mice , RNA Virus Infections/immunology , RNA Virus Infections/metabolism , Ubiquitins/metabolism , Ubiquitins/genetics , DEAD Box Protein 58/metabolism , Interferon Type I/metabolism , Adaptor Proteins, Signal Transducing/metabolism , Adaptor Proteins, Signal Transducing/genetics , Cytokines/metabolism , Mice, Inbred C57BL , Humans , Receptors, Immunologic/metabolism , Interferon-beta/metabolism , RNA Viruses/immunology , Interferon Regulatory Factor-3/metabolismABSTRACT
Detailed understanding of the signaling intermediates that confer the sensing of intracellular viral nucleic acids for induction of type I interferons is critical for strategies to curtail viral mechanisms that impede innate immune defenses. Here we show that the activation of the microtubule-associated guanine nucleotide exchange factor GEF-H1, encoded by Arhgef2, is essential for sensing of foreign RNA by RIG-I-like receptors. Activation of GEF-H1 controls RIG-I-dependent and Mda5-dependent phosphorylation of IRF3 and induction of IFN-ß expression in macrophages. Generation of Arhgef2(-/-) mice revealed a pronounced signaling defect that prevented antiviral host responses to encephalomyocarditis virus and influenza A virus. Microtubule networks sequester GEF-H1 that upon activation is released to enable antiviral signaling by intracellular nucleic acid detection pathways.
Subject(s)
Immunity, Innate/immunology , Microtubules/immunology , RNA, Viral/immunology , Rho Guanine Nucleotide Exchange Factors/immunology , Signal Transduction/immunology , Animals , COS Cells , Chlorocebus aethiops , DEAD Box Protein 58 , DEAD-box RNA Helicases/immunology , DEAD-box RNA Helicases/metabolism , Gene Expression/immunology , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HEK293 Cells , Humans , Immunity, Innate/genetics , Immunoblotting , Influenza A virus/genetics , Interferon Regulatory Factor-3/immunology , Interferon Regulatory Factor-3/metabolism , Interferon-Induced Helicase, IFIH1 , Interferon-beta/genetics , Interferon-beta/immunology , Interferon-beta/metabolism , Macrophages/immunology , Macrophages/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Confocal , Microtubules/metabolism , Phosphorylation , Reverse Transcriptase Polymerase Chain Reaction , Rho Guanine Nucleotide Exchange Factors/genetics , Rho Guanine Nucleotide Exchange Factors/metabolism , Signal Transduction/geneticsABSTRACT
The cyclic GMP-AMP synthase (cGAS)-stimulator of IFN genes (STING) pathway is instrumental to antitumor immunity, yet the underlying molecular and cellular mechanisms are complex and still unfolding. A new paradigm suggests that cancer cells' cGAS-synthesized cGAMP can be transferred to tumor-infiltrating immune cells, eliciting STING-dependent IFN-ß response for antitumor immunity. Nevertheless, how the tumor microenvironment may shape this process remains unclear. In this study, we found that extracellular ATP, an immune regulatory molecule widely present in the tumor microenvironment, can potentiate cGAMP transfer, thereby boosting the STING signaling and IFN-ß response in murine macrophages and fibroblasts. Notably, genetic ablation or chemical inhibition of murine volume-regulation anion channel LRRC8/volume-regulated anion channel (VRAC), a recently identified cGAMP transporter, abolished ATP-potentiated cGAMP transfer and STING-dependent IFN-ß response, revealing a crucial role of LRRC8/VRAC in the cross-talk of extracellular ATP and cGAMP. Mechanistically, ATP activation of the P2X family receptors triggered Ca2+ influx and K+ efflux, promoting reactive oxygen species production. Moreover, ATP-evoked K+ efflux alleviated the phosphorylation of VRAC's obligate subunit LRRC8A/SWELL1 on S174. Mutagenesis studies indicated that the phosphorylation of S174 on LRRC8A could act as a checkpoint for VRAC in the steady state and a rheostat of ATP responsiveness. In an MC38-transplanted tumor model, systemically blocking CD39 and ENPP1, hydroxylases of extracellular ATP and cGAMP, respectively, elevated antitumor NK, NKT, and CD8+ T cell responses and restrained tumor growth in mice. Altogether, this study establishes a crucial role of ATP in facilitating LRRC8/VRAC transport cGAMP in the tumor microenvironment and provides new insight into harnessing cGAMP transfer for antitumor immunity.
Subject(s)
Adenosine Triphosphate , Membrane Proteins , Nucleotides, Cyclic , Tumor Microenvironment , Animals , Nucleotides, Cyclic/metabolism , Mice , Adenosine Triphosphate/metabolism , Membrane Proteins/metabolism , Membrane Proteins/immunology , Tumor Microenvironment/immunology , Interferon-beta/metabolism , Interferon-beta/immunology , Mice, Inbred C57BL , Humans , Signal Transduction/immunology , Mice, Knockout , Cell Line, Tumor , Cations/metabolism , Neoplasms/immunology , Neoplasms/metabolism , Nucleotidyltransferases/metabolism , Macrophages/immunology , Macrophages/metabolismABSTRACT
Double-stranded RNA (dsRNA) is a potent proinflammatory signature of viral infection. Long cytosolic dsRNA is recognized by MDA5. The cooperative assembly of MDA5 into helical filaments on dsRNA nucleates the assembly of a multiprotein type I interferon signaling platform. Here, we determined cryoelectron microscopy (cryo-EM) structures of MDA5-dsRNA filaments with different helical twists and bound nucleotide analogs at resolutions sufficient to build and refine atomic models. The structures identify the filament-forming interfaces, which encode the dsRNA binding cooperativity and length specificity of MDA5. The predominantly hydrophobic interface contacts confer flexibility, reflected in the variable helical twist within filaments. Mutation of filament-forming residues can result in loss or gain of signaling activity. Each MDA5 molecule spans 14 or 15 RNA base pairs, depending on the twist. Variations in twist also correlate with variations in the occupancy and type of nucleotide in the active site, providing insights on how ATP hydrolysis contributes to MDA5-dsRNA recognition.
Subject(s)
Adenosine Triphosphate/metabolism , Cryoelectron Microscopy , Interferon-Induced Helicase, IFIH1/ultrastructure , RNA, Double-Stranded/ultrastructure , HEK293 Cells , Humans , Hydrolysis , Hydrophobic and Hydrophilic Interactions , Interferon-Induced Helicase, IFIH1/genetics , Interferon-Induced Helicase, IFIH1/metabolism , Interferon-beta/genetics , Interferon-beta/metabolism , Molecular Docking Simulation , Mutation , Nucleic Acid Conformation , Protein Conformation , RNA, Double-Stranded/metabolism , Signal Transduction , Structure-Activity RelationshipABSTRACT
Virus infection induces stochastic activation of the interferon-ß gene. Three previously identified Alu-like DNA elements called NRCs (NF-κB reception centers) function by capturing and delivering NF-κB to the IFNB1 enhancer via stochastic interchromosomal interactions. We show that the transcription factor ThPOK binds cooperatively with NF-κB to NRCs and mediates their physical proximity with the IFNB1 gene via its ability to oligomerize when bound to DNA. ThPOK knockdown significantly decreased the frequency of interchromosomal interactions, NF-κB DNA binding to the IFNB1 enhancer, and virus-induced IFNB1 gene activation. We also demonstrate that cooperative DNA binding between ThPOK and NF-κB on the same face of the double DNA helix is required for interchromosomal interactions and distinguishes NRCs from various other Alu elements bearing κB sites. These studies show how DNA binding cooperativity of stereospecifically aligned transcription factors provides the necessary ultrasensitivity for the all-or-none stochastic cell responses to virus infection.
Subject(s)
DNA-Binding Proteins/metabolism , Interferon-beta/metabolism , Transcription Factors/metabolism , Alu Elements , Chromosomes/genetics , Chromosomes/metabolism , DNA-Binding Proteins/genetics , Enhancer Elements, Genetic , HEK293 Cells , HeLa Cells , Humans , Interferon-beta/genetics , NF-kappa B/metabolism , Promoter Regions, Genetic , Stochastic Processes , Transcription Factors/genetics , Transcription, Genetic , Virus Diseases/metabolismABSTRACT
Modification of mRNA by N6-adenosine methylation (m6A) on internal bases influences gene expression in eukaryotes. How the dynamic genome-wide landscape of m6A-modified mRNAs impacts virus infection and host immune responses remains poorly understood. Here, we show that type I interferon (IFN) production triggered by dsDNA or human cytomegalovirus (HCMV) is controlled by the cellular m6A methyltrasferase subunit METTL14 and ALKBH5 demethylase. While METTL14 depletion reduced virus reproduction and stimulated dsDNA- or HCMV-induced IFNB1 mRNA accumulation, ALKBH5 depletion had the opposite effect. Depleting METTL14 increased both nascent IFNB1 mRNA production and stability in response to dsDNA. In contrast, ALKBH5 depletion reduced nascent IFNB1 mRNA production without detectably influencing IFN1B mRNA decay. Genome-wide transcriptome profiling following ALKBH5 depletion identified differentially expressed genes regulating antiviral immune responses, while METTL14 depletion altered pathways impacting metabolic reprogramming, stress responses, and aging. Finally, we determined that IFNB1 mRNA was m6A-modified within both the coding sequence and the 3' untranslated region (UTR). This establishes that the host m6A modification machinery controls IFNß production triggered by HCMV or dsDNA. Moreover, it demonstrates that responses to nonmicrobial dsDNA in uninfected cells, which shape host immunity and contribute to autoimmune disease, are regulated by enzymes controlling m6A epitranscriptomic changes.
Subject(s)
DNA/immunology , Gene Expression Regulation/genetics , Immune System/enzymology , Immunity, Innate/genetics , Interferon-beta/genetics , Methyltransferases/metabolism , AlkB Homolog 5, RNA Demethylase/genetics , AlkB Homolog 5, RNA Demethylase/metabolism , Animals , Cell Line , Chlorocebus aethiops , Cytomegalovirus/immunology , Gene Expression Profiling , Humans , Interferon-beta/metabolism , RNA Stability/genetics , Vero Cells , Virus Replication/geneticsABSTRACT
Mitochondrial homeostasis is essential for providing cellular energy, particularly in resource-demanding neurons, defects in which cause neurodegeneration, but the function of interferons (IFNs) in regulating neuronal mitochondrial homeostasis is unknown. We found that neuronal IFN-ß is indispensable for mitochondrial homeostasis and metabolism, sustaining ATP levels and preventing excessive ROS by controlling mitochondrial fission. IFN-ß induces events that are required for mitochondrial fission, phosphorylating STAT5 and upregulating PGAM5, which phosphorylates serine 622 of Drp1. IFN-ß signaling then recruits Drp1 to mitochondria, oligomerizes it, and engages INF2 to stabilize mitochondria-endoplasmic reticulum (ER) platforms. This process tethers damaged mitochondria to the ER to separate them via fission. Lack of neuronal IFN-ß in the Ifnb-/- model of Parkinson disease (PD) disrupts STAT5-PGAM5-Drp1 signaling, impairing fission and causing large multibranched, damaged mitochondria with insufficient ATP production and excessive oxidative stress to accumulate. In other PD models, IFN-ß rescues dopaminergic neuronal cell death and pathology, associated with preserved mitochondrial homeostasis. Thus, IFN-ß activates mitochondrial fission in neurons through the pSTAT5/PGAM5/S622 Drp1 pathway to stabilize mitochondria/ER platforms, constituting an essential neuroprotective mechanism.
Subject(s)
Interferon-beta/metabolism , Mitochondrial Dynamics , Parkinson Disease/metabolism , Animals , Cell Line , Cell Line, Tumor , Dynamins/metabolism , Formins/metabolism , Interferon-beta/genetics , Mice , Mitochondria/metabolism , Neurons/metabolism , Phosphoprotein Phosphatases/metabolism , STAT5 Transcription Factor/metabolismABSTRACT
The controlled release of mitochondrial content into the cytosol has emerged as one of the key steps in mitochondrial signaling. In particular, the release of mitochondrial DNA (mtDNA) into the cytosol has been shown to activate interferon beta (IFN-ß) gene expression to execute the innate immune response. In this report, we show that human adenovirus type 5 (HAdV-C5) infection induces the release of mtDNA into the cytosol. The release of mtDNA is mediated by the viral minor capsid protein VI (pVI), which localizes to mitochondria. The presence of the mitochondrial membrane proteins Bak and Bax are needed for the mtDNA release, whereas the viral E1B-19K protein blocked pVI-mediated mtDNA release. Surprisingly, the pVI-mediated mtDNA release did not increase but inhibited the IFN-ß gene expression. Notably, the pVI expression caused mitochondrial leakage of the HSP60 protein. The latter prevented specific phosphorylation of the interferon regulatory factor 3 (IRF3) needed for IFN-ß gene expression. Overall, we assign a new mitochondria and IFN-ß signaling-modulating function to the HAdV-C5 minor capsid protein VI. IMPORTANCE: Human adenoviruses (HAdVs) are common pathogens causing various self-limiting diseases, including conjunctivitis and the common cold. HAdVs need to interfere with multiple cellular signaling pathways during the infection to gain control over the host cell. In this study, we identified human adenovirus type 5 (HAdV-C5) minor capsid protein VI as a factor modulating mitochondrial membrane integrity and mitochondrial signaling. We show that pVI-altered mitochondrial signaling impedes the cell's innate immune response, which may benefit HAdV growth. Overall, our study provides new detailed insights into the HAdV-mitochondria interactions and signaling. This knowledge is helpful when developing new anti-viral treatments against pathogenic HAdV infections and improving HAdV-based therapeutics.