4A ); these findings are consistent with MAVS and cGAS activation induced by BCR signaling. Recently, evidence has shown that self-DNA release and cGAS-STING pathway over-activation can drive lung disease, making this pathway a promising therapeutic target for inflammatory lung disease. Mock (no DNA) was set as 1. cGAS KO cells serve as a negative control. Bars, 100 μm. Several DNA viruses carrying dsDNA activate cGAS-STING signaling in in vitro and in vivo studies. Activated STING translocates from the ER to the Golgi apparatus, where STING recruits and activates the kinase TBK1 that mediates the phosphorylation of IRF3 and NF-κB. To investigate whether VZV ORFs block cGAS/STING activation, we utilised a luciferase-based screening platform in HEK293T cells. In addition to the classic cGAS/STING-IFN axis (Fig. L) Immunoblot against cGAS and STING in NHDF-NT, NHDF-cGAS KO and NHDF-STING KO pools CAS PubMed PubMed Central Google Scholar . Activation of STING was independent of the cytosolic double stranded DNA sensor cGAS, and infection did not induce detectable release into the cytosol of either mitochondrial, nuclear or bacterial DNA-indicating DNA-independent activation of the STING pathway in S. pyogenes infected macrophages. Upon DNA binding, cGAS produces the second messenger cGAMP (cyclic guanosine monophosphate adenosine monophosphate), which activates the adaptor protein STING (STimulator of INterferon Genes, also known as transmembrane protein 173, TMEM173). We show that cGAMP administration at 1 to 10 µg increased STING dimers, TBK1 phosphorylation (pTBK1),. Additionally, tumor cells and MDSCs may impede STING signaling by upregulating Gal9 or via other . Conversely, . 2c ). The cGAS-STING pathway relies on two independent receptors. cGAS-STING pathway in DC In tumor microenvironment, cGAS-STING in DC plays an important role in the cross-presentation and priming of tumor-specific CD8+ Tcell(Fig.2). In- N.Y., J.G., and Z.C. Using gene targeting, RNA interference and inhibitors, we found that the innate immune response to Etoposide required STING but, unexpectedly, was independent of cGAS. In this study, we evaluated the role of Mn 2+ on the activation of cGAS-STING pathway combining with RT. On one hand, activation of the cGAS-STING pathway promotes antitumor immunity, although some cancers escape this immunity by deactivating the cGAS-STING pathway . Investigation of the effects of TBI on cGAS/STING activation, IFN-I signaling and neuroinflammation in young and aged C57Bl/6 male mice confirmed activation of key neuroinflammatory pathways in biochemical studies and indicated a mechanistic link between microglial-associated neuro inflammation and neurodegeneration in the aged TBI brain. To cite this article: Leonie Unterholzner & Gillian Dunphy (2019): cGAS-independent STING activation in response to DNA damage, Molecular & Cellular Oncology, DOI: 10.1080/23723556.2018.1558682 We thus used diABZI to reinforce the activation of cGAS‐STING pathway and then investigate its inhibitory effect of irradiation on NSCLC cells. cGas is a nucleotidyl transferase enzyme which catalyzes the conversion of ATP and GTP into a novel cyclic dinucleotide, cGMP-AMP (cGAMP) which in turn binds and activates Sting. The detection of DNA damage in the nucleus induces However, the molecular mechanisms involved in the above studies, especially those responsible for triggering spontaneous activation of the type 1 IFN response in . Immunoprecipitation . . cGAS‐STING pathway activator enhances the inhibitory effect of irradiation on NSCLC cells According to a previous study, 8 the small molecule diABZI was able to activate the cGAS‐STING pathway. Our recent study reported the involvement of Aim2 as the sensor of DNA vaccines in eliciting Ag-specific Ab responses. However, it is not clear how STING is activated in this setting. cGAS-STING pathway downregulates the expression of anti-apoptosis protein BCL2 and upregulates the abundance of pro-apoptosis protein BCL2-associated X (BAX) . Thus, the control of cGAS activity against nuclear self . Downstream from the BCR, Btk activation is a defining feature of the signaling induced by TI-2 antigens ( 1 ). Notably, HSV-1 infection. By contrast, in BAF-KD cells, mechanical compression elicited cGAS-STING pathway activation, as revealed by robust IRF3 activation (Fig. While CGAS was originally found to be required for STING1 activation during viral infection, recent studies have also reported a CGAS-independent STING1 pathway in response to different Jo urn al Pre- pr of 13 stimuli, including virial infection (Holm et al., 2016; Suschak et al., 2016; Unterholzner and Dunphy, 2019). helps cGAS in the activation of STING during cytosolic DNA recognition in human cells.8,9 However, even though IFI16 is also involved in conventional cytosolic DNA sensing, it promotes a different mode of STING activation after Etoposide-induced damage. Nat Commun 7: 10680 Crossref CAS PubMed Web of Science . Of course, the activation of the cGAS-STING signal pathway is also determined by the dose and frequency of radiotherapy. cGAS-independent STING activation in response to DNA damage Self-DNA has previously been thought to be protected from immune detection by compartmentalisation in the nucleus or mitochondria. Tumor-derived DNA The capacity of cGAS to initiate STING activation by eCDNs prompted us to investigate whether cGAS directly senses endocytosed eCDNs. KSHV primary infection can activate a STING-cGAS-dependent IFN-β response. a mRNA expression levels of cGAS (grey bars) and STING (black bars) in different cancer cell lines. K) ISRE reporter activation in THP1-Dual-CAS9 cells treated with 10uM cGAS inhibitor (G140) or DMSO and stimulated with 2.5ug/ml ISD (+ Lipofectamin LTX plus), 5ug/ml R848 or 50uM cGAMP. The recombinant DDX41 protein exhibited ATP-dependent DNA unwinding activity and ATP-independent strand annealing activity. 7 We also did not detect any production of the second messenger cGAMP in Etoposide-treated cells, or the classical signs of STING activation such as its translocation to peri . For example, several instances of STING-mediated induction of programed cell death have been reported40-49 Figure 1. More recently, it was reported that ATM inhibition could activate a type 1 IFN response in pancreatic tumor cells that could enhance ICB therapy in a cGAS/STING-independent manner . cGAMP acts as a second messenger, which can directly activate STING in the cGAS engaged cells (if present—in this schematic the cells with cytosolic DNA do not express STING). To further substantiate the telomere-related disease exacerbation, we also . cGAS activation by G3BP1 is independent of stress granule assembly. 5 A and B). In contrast, a recent study revealed that cGAS protects the liver from IR injury in a STING-independent manner (Lei et al., 2018). Several DNA viruses carrying dsDNA activate cGAS-STING signaling in in vitro and in vivo studies. Overview of cGAS activation and cGAS-STING signaling. The released DNA can then be detected by cytosolic cGAS to result in cGAMP production. During conventional DNA sensing, STING translocates from the ER to peri-nuclear foci and gets phosphorylated by TBK1 at Serine 366 ( Dobbs et al., 2015 , Liu et al., 2015 ). On the other hand, inactivation of cGAS signaling causes deficiency to. Often the effect of STING signaling is mediated by IFN-β, but can also be independent of type I IFNs, for example by upregulation of SOCS1 which hampers STAT3 phosphorylation. The activation of DNA-PK by free DNA ends leads to STING-independent IRF3 phosphorylation and type I IFN production . Thus, chronic cGAS-STING activation may promote tumor metastasis which needs to be overcome. STING signalling contributes to the pathology in Niemann-Pick disease type C independent of cGAS- and cGAMP Summary: Scientists at the University of Texas Southwestern Medical Center in Dallas, Texas, uncovered a cGAS- and cGAMP-independent mode of STING activation as the driver of Niemann-Pick disease type C (NPC1). This review focuses on the molecular mechanism of cGAS-dependent and cGAS-independent STING signaling under various disease conditions, particularly highlighting the diverse initiators upon this . An important unanswered question . The relative amount . Email. This results in activation of the cGAS-STING pathway (Dou et al., 2017), a cytosolic DNA sensing signalling response that plays essential roles in activating pro-inflammatory genes (Barber, 2015). Activation of STING was independent of the cytosolic double stranded DNA sensor cGAS, and infection did not induce detectable release into the cytosol of either mitochondrial, nuclear or bacterial DNA-indicating DNA-independent activation of the STING pathway in S. pyogenes infected macrophages. in cGAS-STING pathway. STING is an adaptor protein that is expressed in macrophages, dendritic cells (DCs), and lymphocytes, as well as endothelial and epithelial cells ().Macrophages, as major professional antigen-presenting cells (APCs), are best known for their ability to prime the host defense by engulfing foreign pathogens ().The DNA contained in pathogens would activate the cGAS-STING signal pathway of . A cGAS-Independent STING/IRF7 Pathway Mediates the Immunogenicity of DNA Vaccines It has been known since the discovery of DNA vaccines >20 y ago that DNA vaccines can function as adjuvants. The upstream dsDNA interacts with enzyme cGAS in a sequence-independent way [12, 13], promoting a conformational change of cGAS to catalyze the formation of 2′,3′-cyclic GMP-AMP (cGAMP), a cyclic dinucleotide . Independent of enhanced anti-cancer immunity, cGAS-STING pathway could directly activate senescence and apoptosis signaling pathways in cancer cells [51, 52]. Activation of STING signaling and viral evasion. Activation of the innate immune system is a critical step in limiting viral infection. Kubarenko AV, Andreeva L, Hopfner KP, Hornung V (2014) Cytosolic RNA: DNA hybrids activate the cGAS-STING axis. Using biochemical and genetic approaches (an anti-IL-6R antibody blockade, IL-6 knockout [KO], MyD88 KO or myeloid-specific p38 KO mice), we demonstrate that a blockade of the cGAS . Despite cGAS nuclear translocation, neither approach induced an ISG response in wild-type (WT) cells (Fig. in cGAS-STING pathway. Expand Among these, cyclic GMP-AMP synthase (cGas) is a powerful activator of the Sting/Tbk1 pathway, providing a strong candidate for the unknown DNA vaccine sensor. Moreover, cGAS- or cGAMP-independent STING activation is conceivable. Hence, we examined the possibility of cell death in bacterial-induced fused cells. However . These DNA viruses include adenovirus, 62 vaccinia virus, 34 African swine fever viruses 63 and herpesviruses such as cytomegalovirus, 64, . recent studies have revealed cGAS-STING activities that impact cells in unexpectedly diverse manners. Unexpectedly, cGAS and STING activation were affected in DDX41 KO cells, suggesting that DDX41 functions upstream of cGAS. Although the authors did not mea-sure cytosolic DNA or cGAMP levels to definitively exclude the involvement of cGAS, they found that STING was acti-vated selectively in neurons and . For example, the checkpoint kinase ATM can activate STING in response to etoposide-induced DNA damage independently of cGAS, stimulating NF-κB-dependent gene expression . CDNs produced by cGAS bind to STING in the ER inducing a conformational change in the molecule that leads to relocation of STING and TBK1 to the perinuclear region of the cell resulting in activation ( 16 ). In this work, we investigated whether Natterin activates mitochondrial damage, resulting in self-DNA leaks into the cytosol, and whether the DNA sensor cGAS and STING pathway participate in triggering the innate immune response. A cGAS-independent role of STING has been observed during RNA virus infection. This demonstrates that the function of STING during the response to nuclear DNA damage involves its non-canonical activation in a cGAS- and cGAMP-independent manner. Subsequently, nuclear translocation of IRF3 and NF-κB induces the expression of type I . The intrinsic function of the cGAS-STING pathway facilitates type-I interferon (IFN) inflammatory signaling responses and other cellular processes such as autophagy, cell survival . Taken together, these results establish the engagement of the cGAS-cGAMP-STING axis by flavine in human and mouse cells, through cytoplasmic leakage of DNA products. IFN-β mRNA in HUVECs (A) or EA.hy926 endothelial cells (B) was measured by real-time qPCR 4 h after transfection of various DNA fragments (ISD90, HSV60, and E. coli DNA at 5 μg/mL) and cGAMP (5 μg/mL) with Lipofectamine 2000 (Life Technologies).