A noncanonical function of cGAMP in inflammasome priming and activation

Recognition of pathogen-associated molecular patterns and danger-associated molecular patterns by host cells is an important step in innate immune activation. The DNA sensor cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS) binds to DNA and produces cGAMP, which in turn binds to stimulator of interferon genes (STING) to activate IFN-I. Here we show that cGAMP has a noncanonical function in inflammasome activation in human and mouse cells. Inflammasome activation requires two signals, both of which are activated by cGAMP. cGAMP alone enhances expression of inflammasome components through IFN-I, providing the priming signal. Additionally, when combined with a priming signal, cGAMP activates the inflammasome through an AIM2, NLRP3, ASC, and caspase-1 dependent process. These two cGAMP-mediated functions, priming and activation, have differential requirements for STING. Temporally, cGAMP induction of IFN-I precedes inflammasome activation, which then occurs when IFN-I is waning. In mice, cGAS/cGAMP amplify both inflammasome and IFN-I to control murine cytomegalovirus. Thus, cGAMP activates the inflammasome in addition to IFN-I, and activation of both is needed to control infection by a DNA virus.

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Cyclic Guanosine Monophosphate–Adenosine Monophosphate Synthase (cGAS), a Multifaceted Platform of Intracellular DNA Sensing

Frontiers in Immunology ◽

10.3389/fimmu.2021.637399 ◽

2021 ◽

Vol 12 ◽

Author(s):

Eloi R. Verrier ◽

Christelle Langevin

Keyword(s):

Nucleic Acid ◽

Current Knowledge ◽

Adenosine Monophosphate ◽

Cyclic Guanosine Monophosphate ◽

Innate Immune ◽

Guanosine Monophosphate ◽

Type I ◽

Nucleic Acid Binding ◽

Sting Pathway ◽

Molecular Patterns

Innate immune pathways are the first line of cellular defense against pathogen infections ranging from bacteria to Metazoa. These pathways are activated following the recognition of pathogen associated molecular patterns (PAMPs) by membrane and cytosolic pattern recognition receptors. In addition, some of these cellular sensors can also recognize endogenous danger-associated molecular patterns (DAMPs) arising from damaged or dying cells and triggering innate immune responses. Among the cytosolic nucleic acid sensors, the cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS) plays an essential role in the activation of the type I interferon (IFNs) response and the production of pro-inflammatory cytokines. Indeed, upon nucleic acid binding, cGAS synthesizes cGAMP, a second messenger mediating the activation of the STING signaling pathway. The functional conservation of the cGAS-STING pathway during evolution highlights its importance in host cellular surveillance against pathogen infections. Apart from their functions in immunity, cGAS and STING also play major roles in nuclear functions and tumor development. Therefore, cGAS-STING is now considered as an attractive target to identify novel biomarkers and design therapeutics for auto-inflammatory and autoimmune disorders as well as infectious diseases and cancer. Here, we review the current knowledge about the structure of cGAS and the evolution from bacteria to Metazoa and present its main functions in defense against pathogens and cancer, in connection with STING. The advantages and limitations of in vivo models relevant for studying the cGAS-STING pathway will be discussed for the notion of species specificity and in the context of their integration into therapeutic screening assays targeting cGAG and/or STING.

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Cyclic GMP-AMP Synthase Is an Innate Immune Sensor of HIV and Other Retroviruses

Science ◽

10.1126/science.1240933 ◽

2013 ◽

Vol 341 (6148) ◽

pp. 903-906 ◽

Cited By ~ 553

Author(s):

Daxing Gao ◽

Jiaxi Wu ◽

You-Tong Wu ◽

Fenghe Du ◽

Chukwuemika Aroh ◽

...

Keyword(s):

Leukemia Virus ◽

Adaptor Protein ◽

Adenosine Monophosphate ◽

Cyclic Guanosine Monophosphate ◽

Innate Immune ◽

Guanosine Monophosphate ◽

Type I Interferons ◽

Type I ◽

Innate Immune Responses ◽

Hiv Reverse Transcriptase

Retroviruses, including HIV, can activate innate immune responses, but the host sensors for retroviruses are largely unknown. Here we show that HIV infection activates cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS) to produce cGAMP, which binds to and activates the adaptor protein STING to induce type I interferons and other cytokines. Inhibitors of HIV reverse transcriptase, but not integrase, abrogated interferon-β induction by the virus, suggesting that the reverse-transcribed HIV DNA triggers the innate immune response. Knockout or knockdown of cGAS in mouse or human cell lines blocked cytokine induction by HIV, murine leukemia virus, and simian immunodeficiency virus. These results indicate that cGAS is an innate immune sensor of HIV and other retroviruses.

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Cyclic guanosine monophosphate/adenosine monophosphate synthase (cGAS), innate immune responses, and viral hepatitis

Hepatology ◽

10.1002/hep.27187 ◽

2014 ◽

Vol 60 (3) ◽

pp. 1098-1100 ◽

Cited By ~ 2

Author(s):

Eloi R. Verrier ◽

Michaela U. Gack ◽

Thomas F. Baumert

Keyword(s):

Immune Responses ◽

Viral Hepatitis ◽

Adenosine Monophosphate ◽

Cyclic Guanosine Monophosphate ◽

Innate Immune ◽

Guanosine Monophosphate ◽

Innate Immune Responses

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BAF restricts cGAS on nuclear DNA to prevent innate immune activation

Science ◽

10.1126/science.aaw6421 ◽

2020 ◽

Vol 369 (6505) ◽

pp. 823-828 ◽

Cited By ~ 4

Author(s):

Baptiste Guey ◽

Marilena Wischnewski ◽

Alexiane Decout ◽

Kristina Makasheva ◽

Murat Kaynak ◽

...

Keyword(s):

Immune Responses ◽

Nuclear Dna ◽

Membrane Integrity ◽

Adenosine Monophosphate ◽

Cyclic Guanosine Monophosphate ◽

Innate Immune ◽

Guanosine Monophosphate ◽

Danger Signal ◽

Physical Separation ◽

Safeguard Mechanism

The appearance of DNA in the cytosol is perceived as a danger signal that stimulates potent immune responses through cyclic guanosine monophosphate–adenosine monophosphate synthase (cGAS). How cells regulate the activity of cGAS toward self-DNA and guard against potentially damaging autoinflammatory responses is a fundamental biological question. Here, we identify barrier-to-autointegration factor 1 (BAF) as a natural opponent of cGAS activity on genomic self-DNA. We show that BAF dynamically outcompetes cGAS for DNA binding, hence prohibiting the formation of DNA-cGAS complexes that are essential for enzymatic activity. Upon acute loss of nuclear membrane integrity, BAF is necessary to restrict cGAS activity on exposed DNA. Our observations reveal a safeguard mechanism, distinct from physical separation, by which cells protect themselves against aberrant immune responses toward genomic DNA.

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Polydatin Attenuates Carbachol-induced Contraction of Guinea Pig Gallbladder

Current Topics in Nutraceutical Research ◽

10.37290/ctnr2641-452x.18:34-38 ◽

2019 ◽

Vol 18 (1) ◽

pp. 34-38

Author(s):

Chen Lei ◽

Pan Xiang ◽

Shen Yonggang ◽

Song Kai ◽

Zhong Xingguo ◽

...

Keyword(s):

Protein Kinase ◽

Guinea Pig ◽

Smooth Muscles ◽

Cyclic Adenosine Monophosphate ◽

Adenosine Monophosphate ◽

Cyclic Guanosine Monophosphate ◽

Guanosine Monophosphate ◽

Dependent Manner ◽

Underlying Mechanisms ◽

Dose Dependent

The aim of this study was to determine whether polydatin, a glucoside of resveratrol isolated from the root of Polygonum cuspidatum, warranted development as a potential therapeutic for ameliorating the pain originating from gallbladder spasm disorders and the underlying mechanisms. Guinea pig gallbladder smooth muscles were treated with polydatin and specific inhibitors to explore the mechanisms underpinning polydatin-induced relaxation of carbachol-precontracted guinea pig gallbladder. Our results shown that polydatin relaxed carbachol-induced contraction in a dose-dependent manner through the nitric oxide/cyclic guanosine monophosphate/protein kinase G and the cyclic adenosine monophosphate/protein kinase A signaling pathways as well as the myosin light chain kinase and potassium channels. Our findings suggested that there was value in further exploring the potential therapeutic use of polydatin in gallbladder spasm disorders.

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ANP and BNP Exert Anti-Inflammatory Action via NPR-1/cGMP Axis by Interfering with Canonical, Non-Canonical, and Alternative Routes of Inflammasome Activation in Human THP1 Cells

International Journal of Molecular Sciences ◽

10.3390/ijms22010024 ◽

2020 ◽

Vol 22 (1) ◽

pp. 24

Author(s):

Letizia Mezzasoma ◽

Vincenzo Nicola Talesa ◽

Rita Romani ◽

Ilaria Bellezza

Keyword(s):

Natriuretic Peptide ◽

Specific Inhibitor ◽

Cyclic Guanosine Monophosphate ◽

Guanosine Monophosphate ◽

Caspase 8 ◽

Inflammasome Activation ◽

Intracellular Cgmp ◽

Dependent Protein ◽

Anti Inflammatory ◽

Alternative Routes

Dysregulated inflammasome activation and interleukin (IL)-1β production are associated with several inflammatory disorders. Three different routes can lead to inflammasome activation: a canonical two-step, a non-canonical Caspase-4/5- and Gasdermin D-dependent, and an alternative Caspase-8-mediated pathway. Natriuretic Peptides (NPs), Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP), binding to Natriuretic Peptide Receptor-1 (NPR-1), signal by increasing cGMP (cyclic guanosine monophosphate) levels that, in turn, stimulate cGMP-dependent protein kinase-I (PKG-I). We previously demonstrated that, by counteracting inflammasome activation, NPs inhibit IL-1β secretion. Here we aimed to decipher the molecular mechanism underlying NPs effects on THP-1 cells stimulated with lipopolysaccharide (LPS) + ATP. Involvement of cGMP and PKG-I were assessed pre-treating THP-1 cells with the membrane-permeable analogue, 8-Br-cGMP, and the specific inhibitor KT-5823, respectively. We found that NPs, by activating NPR-1/cGMP/PKG-I axis, lead to phosphorylation of NLRP3 at Ser295 and to inflammasome platform disassembly. Moreover, by increasing intracellular cGMP levels and activating phosphodiesterases, NPs interfere with both Gasdermin D and Caspase-8 cleavage, indicating that they disturb non-canonical and alternative routes of inflammasome activation. These results showed that ANP and BNP anti-inflammatory and immunomodulatory actions may involve the inhibition of all the known routes of inflammasome activation. Thus, NPs might be proposed for the treatment of the plethora of diseases caused by a dysregulated inflammasome activation.

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Inflammasome Activation Contributes to Interleukin-23 Production in Response to Clostridium difficile

mBio ◽

10.1128/mbio.02386-14 ◽

2015 ◽

Vol 6 (1) ◽

Cited By ~ 31

Author(s):

Carrie A. Cowardin ◽

Sarah A. Kuehne ◽

Erica L. Buonomo ◽

Chelsea S. Marie ◽

Nigel P. Minton ◽

...

Keyword(s):

Clostridium Difficile ◽

Disease Severity ◽

Tissue Damage ◽

The United States ◽

Host Cells ◽

Inflammasome Activation ◽

Content Type ◽

Danger Signals ◽

Interleukin 23 ◽

Molecular Patterns

ABSTRACT Clostridium difficileis the most common hospital-acquired pathogen, causing antibiotic-associated diarrhea in over 250,000 patients annually in the United States. Disease is primarily mediated by toxins A and B, which induce potent proinflammatory signaling in host cells and can activate an ASC-containing inflammasome. Recent findings suggest that the intensity of the host response to infection correlates with disease severity. Our lab has identified the proinflammatory cytokine interleukin-23 (IL-23) as a pathogenic mediator during C. difficile infection (CDI). The mechanisms by which C. difficile induces IL-23, however, are not well understood, and the role of toxins A and B in this process is unclear. Here, we show that toxins A and B alone are not sufficient for IL-23 production but synergistically increase the amount of IL-23 produced in response to MyD88-dependent danger signals, including pathogen-associated molecular patterns (PAMPs) and host-derived damage associated molecular patterns (DAMPs). Danger signals also enhanced the secretion of IL-1β in response to toxins A and B, and subsequent IL-1 receptor signaling accounted for the majority of the increase in IL-23 that occurred in the presence of the toxins. Inhibition of inflammasome activation in the presence of extracellular K+likewise decreased IL-23 production. Finally, we found that IL-1β was increased in the serum of patients with CDI, suggesting that this systemic response could influence downstream production of pathogenic IL-23. Identification of the synergy of danger signals with toxins A and B via inflammasome signaling represents a novel finding in the mechanistic understanding of C. difficile-induced inflammation.IMPORTANCEClostridium difficileis among the leading causes of death due to health care-associated infection, and factors determining disease severity are not well understood. C. difficile secretes toxins A and B, which cause inflammation and tissue damage, and recent findings suggest that some of this tissue damage may be due to an inappropriate host immune response. We have found that toxins A and B, in combination with both bacterium- and host-derived danger signals, can induce expression of the proinflammatory cytokines IL-1β and IL-23. Our results demonstrate that IL-1β signaling enhances IL-23 production and could lead to increased pathogenic inflammation during CDI.

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Effects of Haima Duobian Pill in a Rat Model of Kidney Yang Deficiency Syndrome

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2021/6696234 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Yijia Zeng ◽

Tingna Li ◽

Xiaorui Zhang ◽

Yuanyuan Ren ◽

Qinwan Huang ◽

...

Keyword(s):

Rat Model ◽

Cyclic Adenosine Monophosphate ◽

Adenosine Monophosphate ◽

Cyclic Guanosine Monophosphate ◽

Deficiency Syndrome ◽

Guanosine Monophosphate ◽

Network Pharmacology ◽

Enzyme Linked Immunosorbent Assay ◽

Therapeutic Effects ◽

Kidney Yang Deficiency

Objective. Modern research shows that Haima Duobian pill (HDP) can relieve the kidney yang deficiency syndrome (KYDS), but the mechanism is still unclear. The aim of this work was to study the effects of HDP in a rat model of KYDS. Materials and Methods. The network pharmacology methods were used to predict the therapeutic effects of Haima Duobian pill. Adenine was used to establish the rat model of kidney yang deficiency syndrome. The general physical signs of rats were observed after different doses of Haima Duobian pill (HDP) were given. Serum cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T), estradiol (E2), and gonadotropin-releasing hormone (GnRH) levels were determined using enzyme-linked immunosorbent assay (ELISA) kits. Then, the histopathologic changes and sperm activity were detected. Results. HDP could improve the general signs of kidney yang deficiency syndrome rats. After the rats were treated with HDP, the expression of cGMP and E2 was significantly inhibited and the expression of cAMP and T was significantly increased. The pathological damage of testis, epididymis, and seminal vesicle was alleviated, and the sperm activity was improved. Conclusion. For adenine-induced kidney yang deficiency syndrome in rats, HDP had a significant therapeutic effect.

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A host type I interferon response is induced by cytosolic sensing of the bacterial second messenger cyclic-di-GMP

Journal of Experimental Medicine ◽

10.1084/jem.20082874 ◽

2009 ◽

Vol 206 (9) ◽

pp. 1899-1911 ◽

Cited By ~ 202

Author(s):

Sarah M. McWhirter ◽

Roman Barbalat ◽

Kathryn M. Monroe ◽

Mary F. Fontana ◽

Mamoru Hyodo ◽

...

Keyword(s):

Mammalian Cells ◽

Map Kinases ◽

Second Messenger ◽

Innate Immune ◽

Guanosine Monophosphate ◽

Host Cells ◽

Type I Interferons ◽

Interferon Response ◽

Type I

The innate immune system responds to unique molecular signatures that are widely conserved among microbes but that are not normally present in host cells. Compounds that stimulate innate immune pathways may be valuable in the design of novel adjuvants, vaccines, and other immunotherapeutics. The cyclic dinucleotide cyclic-di–guanosine monophosphate (c-di-GMP) is a recently appreciated second messenger that plays critical regulatory roles in many species of bacteria but is not produced by eukaryotic cells. In vivo and in vitro studies have previously suggested that c-di-GMP is a potent immunostimulatory compound recognized by mouse and human cells. We provide evidence that c-di-GMP is sensed in the cytosol of mammalian cells via a novel immunosurveillance pathway. The potency of cytosolic signaling induced by c-di-GMP is comparable to that induced by cytosolic delivery of DNA, and both nucleic acids induce a similar transcriptional profile, including triggering of type I interferons and coregulated genes via induction of TBK1, IRF3, nuclear factor κB, and MAP kinases. However, the cytosolic pathway that senses c-di-GMP appears to be distinct from all known nucleic acid–sensing pathways. Our results suggest a novel mechanism by which host cells can induce an inflammatory response to a widely produced bacterial ligand.

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