Long non-coding RNAs are important regulators of biological processes including immune responses. The immunoregulatory functions of lncRNAs have been revealed primarily in murine models with limited ...understanding of lncRNAs in human immune responses. Here, we identify lncRNA LUCAT1 which is upregulated in human myeloid cells stimulated with lipopolysaccharide and other innate immune stimuli. Targeted deletion of LUCAT1 in myeloid cells increases expression of type I interferon stimulated genes in response to LPS. By contrast, increased LUCAT1 expression results in a reduction of the inducible ISG response. In activated cells, LUCAT1 is enriched in the nucleus where it associates with chromatin. Further, LUCAT1 limits transcription of interferon stimulated genes by interacting with STAT1 in the nucleus. Together, our study highlights the role of the lncRNA LUCAT1 as a post-induction feedback regulator which functions to restrain the immune response in human cells.
Activated macrophages undergo a metabolic switch to aerobic glycolysis, accumulating Krebs' cycle intermediates that alter transcription of immune response genes. We extended these observations by ...defining fumarate as an inhibitor of pyroptotic cell death. We found that dimethyl fumarate (DMF) delivered to cells or endogenous fumarate reacts with gasdermin D (GSDMD) at critical cysteine residues to form S-(2-succinyl)-cysteine. GSDMD succination prevents its interaction with caspases, limiting its processing, oligomerization, and capacity to induce cell death. In mice, the administration of DMF protects against lipopolysaccharide shock and alleviates familial Mediterranean fever and experimental autoimmune encephalitis by targeting GSDMD. Collectively, these findings identify GSDMD as a target of fumarate and reveal a mechanism of action for fumarate-based therapeutics that include DMF, for the treatment of multiple sclerosis.
Functional peptides encoded by short open reading frames are emerging as important mediators of fundamental biological processes. In this study, we identified a micropeptide produced from a putative ...long noncoding RNA (lncRNAs) that is important in controlling innate immunity. By studying lncRNAs in mice macrophages, we identified lncRNA 1810058I24Rik, which was downregulated in both human and murine myeloid cells exposed to LPS as well as other TLR ligands and inflammatory cytokines. Analysis of lncRNA 1810058I24Rik subcellular localization revealed that this transcript was localized in the cytosol, prompting us to evaluate its coding potential. In vitro translation with
S-labeled methionine resulted in translation of a 47 aa micropeptide. Microscopy and subcellular fractionation studies in macrophages demonstrated endogenous expression of this peptide on the mitochondrion. We thus named this gene mitochondrial micropeptide-47 (Mm47). Crispr-Cas9-mediated deletion of
, as well as small interfering RNA studies in mice primary macrophages, showed that the transcriptional response downstream of TLR4 was intact in cells lacking Mm47. In contrast,
-deficient or knockdown cells were compromised for Nlrp3 inflammasome responses. Activation of Nlrc4 or Aim2 inflammasomes were intact in cells lacking Mm47. This study therefore identifies, to our knowledge, a novel mitochondrial micropeptide Mm47 that is required for the activation of the Nlrp3 inflammasome. This work further highlights the functional activity of short open reading frame-encoded peptides and underscores their importance in innate immunity.
Alterations in the cGAS-STING DNA-sensing pathway affect intestinal homeostasis. We sought to delineate the functional role of STING in intestinal inflammation. Increased STING expression was a ...feature of intestinal inflammation in mice with colitis and in humans afflicted with inflammatory bowel disease. Mice bearing an allele rendering STING constitutively active exhibited spontaneous colitis and dysbiosis, as well as progressive chronic intestinal inflammation and fibrosis. Bone marrow chimera experiments revealed STING accumulation in intestinal macrophages and monocytes as the initial driver of inflammation. Depletion of Gram-negative bacteria prevented STING accumulation in these cells and alleviated intestinal inflammation. STING accumulation occurred at the protein rather than transcript level, suggesting post-translational stabilization. We found that STING was ubiquitinated in myeloid cells, and this K63-linked ubiquitination could be elicited by bacterial products, including cyclic di-GMP. Our findings suggest a positive feedback loop wherein dysbiosis foments the accumulation of STING in intestinal myeloid cells, driving intestinal inflammation.
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•Constitutive activation of STING initiates commensal dysbiosis•STING accumulates predominantly in intestinal myeloid cells during colitis•STING activation in myeloid cells results in progressive and chronic colitis•Colitis-promoting bacterial products trigger ubiquitination and stabilization of STING
To understand the function of the DNA sensing protein STING in intestinal inflammation, Shmeul-Galia et al. utilize a constitutively active STING mouse model that exhibits dysbiosis, severe colitis, and fibrosis. Bacterial nucleotides like cyclic di-GMP initiate a feed-forward loop through the ubiquitination and stabilization of STING in intestinal myeloid cells to promote T cell-dependent colitis.
Recognition of DNA by the innate immune system is central to antiviral and antibacterial defenses, as well as an important contributor to autoimmune diseases involving self DNA. AIM2 (absent in ...melanoma 2) and IFI16 (interferon-inducible protein 16) have been identified as DNA receptors that induce inflammasome formation and interferon production, respectively. Here we present the crystal structures of their HIN domains in complex with double-stranded (ds) DNA. Non-sequence-specific DNA recognition is accomplished through electrostatic attraction between the positively charged HIN domain residues and the dsDNA sugar-phosphate backbone. An intramolecular complex of the AIM2 Pyrin and HIN domains in an autoinhibited state is liberated by DNA binding, which may facilitate the assembly of inflammasomes along the DNA staircase. These findings provide mechanistic insights into dsDNA as the activation trigger and oligomerization platform for the assembly of large innate signaling complexes such as the inflammasomes.
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► Electrostatic attraction underlies innate dsDNA recognition by the HIN domains ► Both OB folds and the linker between them engage the dsDNA backbone ► An autoinhibited state of AIM2 is activated by DNA that liberates the PYD domain ► DNA serves as an oligomerization platform for the inflammasome assembly
Inflammasomes regulate the activity of caspase-1 and the maturation of interleukin 1beta (IL-1beta) and IL-18. AIM2 has been shown to bind DNA and engage the caspase-1-activating adaptor protein ASC ...to form a caspase-1-activating inflammasome. Using Aim2-deficient mice, we identify a central role for AIM2 in regulating caspase-1-dependent maturation of IL-1beta and IL-18, as well as pyroptosis, in response to synthetic double-stranded DNA. AIM2 was essential for inflammasome activation in response to Francisella tularensis, vaccinia virus and mouse cytomegalovirus and had a partial role in the sensing of Listeria monocytogenes. Moreover, production of IL-18 and natural killer cell-dependent production of interferon-gamma, events critical in the early control of virus replication, were dependent on AIM2 during mouse cytomegalovirus infection in vivo. Collectively, our observations demonstrate the importance of AIM2 in the sensing of both bacterial and viral pathogens and in triggering innate immunity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Modular domains of long non-coding RNAs can serve as scaffolds to bring distant regions of the linear genome into spatial proximity. Here, we present HiChIRP, a method leveraging bio-orthogonal ...chemistry and optimized chromosome conformation capture conditions, which enables interrogation of chromatin architecture focused around a specific RNA of interest down to approximately ten copies per cell. HiChIRP of three nuclear RNAs reveals insights into promoter interactions (7SK), telomere biology (telomerase RNA component) and inflammatory gene regulation (lincRNA-EPS).
Deficiency in mevalonate kinase (MVK) causes systemic inflammation. However, the molecular mechanisms linking the mevalonate pathway to inflammation remain obscure. Geranylgeranyl pyrophosphate, a ...non-sterol intermediate of the mevalonate pathway, is the substrate for protein geranylgeranylation, a protein post-translational modification that is catalyzed by protein geranylgeranyl transferase I (GGTase I). Pyrin is an innate immune sensor that forms an active inflammasome in response to bacterial toxins. Mutations in MEFV (encoding human PYRIN) result in autoinflammatory familial Mediterranean fever syndrome. We found that protein geranylgeranylation enabled Toll-like receptor (TLR)-induced activation of phosphatidylinositol-3-OH kinase (PI(3)K) by promoting the interaction between the small GTPase Kras and the PI(3)K catalytic subunit p110δ. Macrophages that were deficient in GGTase I or p110δ exhibited constitutive release of interleukin 1β that was dependent on MEFV but independent of the NLRP3, AIM2 and NLRC4 inflammasomes. In the absence of protein geranylgeranylation, compromised PI(3)K activity allows an unchecked TLR-induced inflammatory responses and constitutive activation of the Pyrin inflammasome.
Detection of DNA is an important determinant of host-defense but also a driver of autoinflammatory and autoimmune diseases. Failure to degrade self-DNA in DNAseII or III(TREX1)-deficient mice results ...in activation of the cGAS-STING pathway. Deficiency of cGAS or STING in these models ameliorates disease manifestations. However, the contribution of the cGAS-STING pathway, relative to endosomal TLRs, in systemic lupus erythematosus (SLE) is controversial. In fact, STING deficiency failed to rescue, and actually exacerbated, disease manifestations in Fas-deficient SLE-prone mice. We have now extended these observations to a chronic model of SLE induced by the i.p. injection of TMPD (pristane). We found that both cGAS- and STING-deficiency not only failed to rescue mice from TMPD-induced SLE, but resulted in increased autoantibody production and higher proteinuria levels compared to cGAS STING sufficient mice. Further, we generated cGAS
Fas
mice on a pure MRL/Fas
background using Crispr/Cas9 and found slightly exacerbated, and not attenuated, disease. We hypothesized that the cGAS-STING pathway constrains TLR activation, and thereby limits autoimmune manifestations in these two models. Consistent with this premise, mice lacking cGAS and Unc93B1 or STING and Unc93B1 developed minimal systemic autoimmunity as compared to cGAS or STING single knock out animals. Nevertheless, TMPD-driven lupus in B6 mice was abrogated upon AAV-delivery of DNAse I, implicating a DNA trigger. Overall, this study demonstrated that the cGAS-STING pathway does not promote systemic autoimmunity in murine models of SLE. These data have important implications for cGAS-STING-directed therapies being developed for the treatment of systemic autoimmunity.
Although Toll-like receptor 9 (TLR9) has been implicated in cytokine and type I interferon (IFN) production during malaria in humans and mice, the high AT content of the Plasmodium falciparum genome ...prompted us to examine the possibility that malarial DNA triggered TLR9-independent pathways. Over 6000 ATTTTTAC (“AT-rich”) motifs are present in the genome of P. falciparum, which we show here potently induce type I IFNs. Parasite DNA, parasitized erythrocytes and oligonucleotides containing the AT-rich motif induce type I IFNs via a pathway that did not involve the previously described sensors TLR9, DAI, RNA polymerase-III or IFI16/p204. Rather, AT-rich DNA sensing involved an unknown receptor that coupled to the STING, TBK1 and IRF3-IRF7 signaling pathway. Mice lacking IRF3, IRF7, the kinase TBK1 or the type I IFN receptor were resistant to otherwise lethal cerebral malaria. Collectively, these observations implicate AT-rich DNA sensing via STING, TBK1 and IRF3-IRF7 in P. falciparum malaria.
► Plasmodium falciparum induces type I IFN inducible genes during infections ► Pf genomic DNA is AT rich and induces type I IFNs in a TLR9-independent manner ► Pf AT-rich DNA triggers a STING-dependent DNA sensing pathway ► Malarial pathology involves TBK1 and IRF3-IRF7-dependent production of type I IFNs
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