The helicase DDX41 senses intracellular DNA mediated by the adaptor STING in dendritic cells

Department of Immunology, Center for Cancer Immunology Research, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
Nature Immunology (Impact Factor: 20). 09/2011; 12(10):959-65. DOI: 10.1038/ni.2091
Source: PubMed


The recognition of pathogenic DNA is important to the initiation of antiviral responses. Here we report the identification of DDX41, a member of the DEXDc family of helicases, as an intracellular DNA sensor in myeloid dendritic cells (mDCs). Knockdown of DDX41 expression by short hairpin RNA blocked the ability of mDCs to mount type I interferon and cytokine responses to DNA and DNA viruses. Overexpression of both DDX41 and the membrane-associated adaptor STING together had a synergistic effect in promoting Ifnb promoter activity. DDX41 bound both DNA and STING and localized together with STING in the cytosol. Knockdown of DDX41 expression blocked activation of the mitogen-activated protein kinase TBK1 and the transcription factors NF-κB and IRF3 by B-form DNA. Our results suggest that DDX41 is an additional DNA sensor that depends on STING to sense pathogenic DNA.

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Available from: Bin Yuan, Dec 04, 2014
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    • "Cytoplasmic DNA is recognized as foreign or indicative of cellular distress because nuclear and mitochondrial membranes typically surround self DNAs. Many DNA sensors in the cytoplasm have been identified, including AIM2 (Fernandes-Alnemri et al., 2009; Hornung et al., 2009; Roberts et al., 2009), DAI (Takaoka et al., 2007), DDX41 (Zhang et al., 2011), DNA-PK (Ferguson et al., 2012), IFI16 (Unterholzner et al., 2010), and a form of RNA polymerase III that detects AT-rich DNA (Ablasser et al., 2009; Chiu et al., 2009). Chronic or deregulated activation of nucleic acid sensing has been shown to contribute to both microbial pathogenesis and autoimmune diseases (Liu et al., 2014; M€ unz et al., 2009). "
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    ABSTRACT: Upon DNA stimulation, cyclic GMP-AMP synthase (cGAS) synthesizes the second messenger cyclic GMP-AMP (cGAMP) that binds to the STING, triggering antiviral interferon-β (IFN-β) production. However, it has remained undetermined how hosts regulate cGAS enzymatic activity after the resolution of DNA immunogen. Here, we show that Akt kinase plays a negative role in cGAS-mediated anti-viral immune response. Akt phosphorylated the S291 or S305 residue of the enzymatic domain of mouse or human cGAS, respectively, and this phosphorylation robustly suppressed its enzymatic activity. Consequently, expression of activated Akt led to the reduction of cGAMP and IFN-β production and the increase of herpes simplex virus 1 replication, whereas treatment with Akt inhibitor augmented cGAS-mediated IFN-β production. Furthermore, expression of the phosphorylation-resistant cGAS S291A mutant enhanced IFN-β production upon DNA stimulation, HSV-1 infection, and vaccinia virus infection. Our study identifies an Akt kinase-mediated checkpoint to fine-tune hosts’ immune responses to DNA stimulation.
    Cell Reports 10/2015; 13(2). DOI:10.1016/j.celrep.2015.09.007 · 8.36 Impact Factor
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    • "Furthermore, while HEK293T/STING cells expressing cGAS displayed a strong antiviral effect to vesicular stomatitis virus (VSV-GFP) infection (14.7% infection), coexpression with ORF52 partially relieved this effect (53.5% infection), suggesting that ORF52 specifically inhibits cGAS-dependent antiviral responses (Figure 1C). The human monocyte cell line THP-1 expresses most cytosolic DNA sensors and has been used extensively for their study (Sun et al., 2013; Wu et al., 2013; Zhang et al., 2011). We made use of the reporter cell line THP1 Lucia ISG (Invivogen), which expresses luciferase from a gene under the control of an IRF3- inducible ISG54 promoter, as a surrogate assay to measure induction of the innate immune response by nucleic acid sensors . "
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    ABSTRACT: Invading viral DNA can be recognized by the host cytosolic DNA sensor, cyclic GMP-AMP (cGAMP) synthase (cGAS), resulting in production of the second messenger cGAMP, which directs the adaptor protein STING to stimulate production of type I interferons (IFNs). Although several DNA viruses are sensed by cGAS, viral strategies targeting cGAS are virtually unknown. We report here that Kaposi's sarcoma-associated herpesvirus (KSHV) ORF52, an abundant gammaherpesvirus-specific tegument protein, subverts cytosolic DNA sensing by directly inhibiting cGAS enzymatic activity through a mechanism involving both cGAS binding and DNA binding. Moreover, ORF52 homologs in other gammaherpesviruses also inhibit cGAS activity and similarly bind cGAS and DNA, suggesting conserved inhibitory mechanisms. Furthermore, KSHV infection evokes cGAS-dependent responses that can limit the infection, and an ORF52 null mutant exhibits increased cGAS signaling. Our findings reveal a mechanism through which gammaherpesviruses antagonize host cGAS DNA sensing. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell host & microbe 08/2015; 18(3). DOI:10.1016/j.chom.2015.07.015 · 12.33 Impact Factor
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    • "DDX41 acts as a cytosolic sensor in mDCs, and can bind with synthetic double-stranded DNA (dsDNA) through the DEAD domain in vitro [12]. Interestingly, in a cell type with limited basal IFI16 expression, DDX41 acts as an initial sensor of cytoplasmic DNA, activating IFN-I and subsequent IFI16 expression, thereby amplifying the innate response [25]. Similar to the function of STING, the DDX41 receptor directly interacts with cyclic dinucleotides (CDNs) and stimulates CDN-induced IFN-I [13]. "
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    ABSTRACT: DDX41, a receptor belonging to the DExD family, functions as a DNA sensor in the mammalian cytoplasm and mediates the antiviral response in host cells. Here, the olive flounder DDX41 was found to have 2267-bp long and encodes a putative protein of 614 amino acid residues. The olive flounder DDX41 mRNA was presented in all tested tissues, and was distinctly expressed in fish naturally infected with LCDV. High expression levels were observed in the heart, liver, kidney and stomach. Furthermore, the olive flounder DDX41 mRNA expression increased significantly in adherent (monocyte-like) cells following stimulation with a DNA virus. Reporter assays showed that the transcriptional activity of the IFN-I promoter was enhanced in DDX41-overexpressing HINAE cells treated with C-di-GMP (dinucleotides). Overexpression of DDX41 also induced the antiviral and inflammatory cytokine gene expression through cytoplasmic C-di-GMP treatment. These results suggest that DDX41 functions as a cytosolic DNA sensor that is capable of inducing antiviral activity and inflammatory responses in the olive flounder. Copyright © 2015. Published by Elsevier Ltd.
    Fish &amp Shellfish Immunology 03/2015; 44(2). DOI:10.1016/j.fsi.2015.03.008 · 2.67 Impact Factor
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