51
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Lu C, MacDougall M. RIG-I-Like Receptor Signaling in Singleton-Merten Syndrome. Front Genet 2017; 8:118. [PMID: 28955379 PMCID: PMC5600918 DOI: 10.3389/fgene.2017.00118] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 08/29/2017] [Indexed: 12/12/2022] Open
Abstract
Singleton-Merten syndrome (SMS) is an autosomal dominant, multi-system innate immune disorder characterized by early and severe aortic and valvular calcification, dental and skeletal abnormalities, psoriasis, glaucoma, and other varying clinical findings. Recently we identified a specific gain-of-function mutation in IFIH1, interferon induced with helicase C domain 1, segregated with this disease. SMS disease without hallmark dental anomalies, termed atypical SMS, has recently been reported caused by variants in DDX58, DEXD/H-box helicase 58. IFIH1 and DDX58 encode retinoic acid-inducible gene I (RIG-I)-like receptors family members melanoma differentiation-associated gene 5 and RIG-I, respectively. These cytosolic pattern recognition receptors function in viral RNA detection initiating an innate immune response through independent pathways that promote type I and type III interferon expression and proinflammatory cytokines. In this review, we focus on SMS as an innate immune disorder summarizing clinical features, molecular aspects of the pathogenetic pathway and discussing underlying mechanisms of the disease.
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Affiliation(s)
- Changming Lu
- Institute of Oral Health Research, School of Dentistry, University of Alabama at Birmingham, BirminghamAL, United States
| | - Mary MacDougall
- Faculty of Dentistry, University of British Columbia, VancouverBC, Canada
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52
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Uchikawa E, Lethier M, Malet H, Brunel J, Gerlier D, Cusack S. Structural Analysis of dsRNA Binding to Anti-viral Pattern Recognition Receptors LGP2 and MDA5. Mol Cell 2017; 62:586-602. [PMID: 27203181 PMCID: PMC4885022 DOI: 10.1016/j.molcel.2016.04.021] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 03/21/2016] [Accepted: 04/19/2016] [Indexed: 12/14/2022]
Abstract
RIG-I and MDA5 sense virus-derived short 5′ppp blunt-ended or long dsRNA, respectively, causing interferon production. Non-signaling LGP2 appears to positively and negatively regulate MDA5 and RIG-I signaling, respectively. Co-crystal structures of chicken (ch) LGP2 with dsRNA display a fully or semi-closed conformation depending on the presence or absence of nucleotide. LGP2 caps blunt, 3′ or 5′ overhang dsRNA ends with 1 bp longer overall footprint than RIG-I. Structures of 1:1 and 2:1 complexes of chMDA5 with short dsRNA reveal head-to-head packing rather than the polar head-to-tail orientation described for long filaments. chLGP2 and chMDA5 make filaments with a similar axial repeat, although less co-operatively for chLGP2. Overall, LGP2 resembles a chimera combining a MDA5-like helicase domain and RIG-I like CTD supporting both stem and end binding. Functionally, RNA binding is required for LGP2-mediated enhancement of MDA5 activation. We propose that LGP2 end-binding may promote nucleation of MDA5 oligomerization on dsRNA. chLPG2-dsRNA structures reveal RIG-I like end binding, but overhangs are possible chMDA5-dsRNA complex structures show head-to-head packing on short dsRNAs LGP2 also has MDA5-like behavior, coating dsRNA but with less cooperativity Both human and chicken LGP2 enhance MDA5 signaling in an RNA-dependent manner
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MESH Headings
- Adenosine Diphosphate/metabolism
- Adenosine Triphosphatases/chemistry
- Adenosine Triphosphatases/genetics
- Adenosine Triphosphatases/metabolism
- Adenosine Triphosphate/metabolism
- Animals
- Avian Proteins/chemistry
- Avian Proteins/genetics
- Avian Proteins/metabolism
- Binding Sites
- Cell Line
- Chickens
- DEAD Box Protein 58/chemistry
- DEAD Box Protein 58/genetics
- DEAD Box Protein 58/metabolism
- Humans
- Hydrolysis
- Interferon-Induced Helicase, IFIH1/chemistry
- Interferon-Induced Helicase, IFIH1/genetics
- Interferon-Induced Helicase, IFIH1/metabolism
- Models, Molecular
- Nucleic Acid Conformation
- Protein Binding
- Protein Interaction Domains and Motifs
- RNA, Double-Stranded/chemistry
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- Receptors, Pattern Recognition/chemistry
- Receptors, Pattern Recognition/genetics
- Receptors, Pattern Recognition/metabolism
- Structure-Activity Relationship
- Transfection
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Affiliation(s)
- Emiko Uchikawa
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France; University Grenoble Alpes, Centre National de la Recherche Scientifique, EMBL Unit of Virus Host-Cell Interactions, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France
| | - Mathilde Lethier
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France; University Grenoble Alpes, Centre National de la Recherche Scientifique, EMBL Unit of Virus Host-Cell Interactions, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France
| | - Hélène Malet
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France; University Grenoble Alpes, Centre National de la Recherche Scientifique, EMBL Unit of Virus Host-Cell Interactions, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France
| | - Joanna Brunel
- CIRI, International Center for Infectiology Research, Université de Lyon, 69007 Lyon, France; Inserm, U1111, 69007 Lyon, France; CNRS, UMR5308, 69007 Lyon, France; Ecole Normale Supérieure de Lyon, 69007 Lyon, France; Université Lyon 1, Centre International de Recherche en Infectiologie, 69007 Lyon, France
| | - Denis Gerlier
- CIRI, International Center for Infectiology Research, Université de Lyon, 69007 Lyon, France; Inserm, U1111, 69007 Lyon, France; CNRS, UMR5308, 69007 Lyon, France; Ecole Normale Supérieure de Lyon, 69007 Lyon, France; Université Lyon 1, Centre International de Recherche en Infectiologie, 69007 Lyon, France
| | - Stephen Cusack
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France; University Grenoble Alpes, Centre National de la Recherche Scientifique, EMBL Unit of Virus Host-Cell Interactions, 71 Avenue des Martyrs, CS 90181, 38042 Grenoble Cedex 9, France.
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53
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Abstract
PURPOSE OF REVIEW We give an update on the etiology and potential treatment options of rare inherited monogenic disorders associated with arterial calcification and calcific cardiac valve disease. RECENT FINDINGS Genetic studies of rare inherited syndromes have identified key regulators of ectopic calcification. Based on the pathogenic principles causing the diseases, these can be classified into three groups: (1) disorders of an increased extracellular inorganic phosphate/inorganic pyrophosphate ratio (generalized arterial calcification of infancy, pseudoxanthoma elasticum, arterial calcification and distal joint calcification, progeria, idiopathic basal ganglia calcification, and hyperphosphatemic familial tumoral calcinosis; (2) interferonopathies (Singleton-Merten syndrome); and (3) others, including Keutel syndrome and Gaucher disease type IIIC. Although some of the identified causative mechanisms are not easy to target for treatment, it has become clear that a disturbed serum phosphate/pyrophosphate ratio is a major force triggering arterial and cardiac valve calcification. Further studies will focus on targeting the phosphate/pyrophosphate ratio to effectively prevent and treat these calcific disease phenotypes.
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MESH Headings
- Abnormalities, Multiple/drug therapy
- Abnormalities, Multiple/genetics
- Abnormalities, Multiple/metabolism
- Aortic Diseases/drug therapy
- Aortic Diseases/genetics
- Aortic Diseases/metabolism
- Basal Ganglia Diseases/drug therapy
- Basal Ganglia Diseases/genetics
- Basal Ganglia Diseases/metabolism
- Calcinosis/drug therapy
- Calcinosis/genetics
- Calcinosis/metabolism
- Cartilage Diseases/drug therapy
- Cartilage Diseases/genetics
- Cartilage Diseases/metabolism
- Dental Enamel Hypoplasia/drug therapy
- Dental Enamel Hypoplasia/genetics
- Dental Enamel Hypoplasia/metabolism
- Diphosphates/metabolism
- Enzyme Replacement Therapy
- Gaucher Disease/drug therapy
- Gaucher Disease/genetics
- Gaucher Disease/metabolism
- Hand Deformities, Congenital/drug therapy
- Hand Deformities, Congenital/genetics
- Hand Deformities, Congenital/metabolism
- Humans
- Hyperostosis, Cortical, Congenital/drug therapy
- Hyperostosis, Cortical, Congenital/genetics
- Hyperostosis, Cortical, Congenital/metabolism
- Hyperphosphatemia/drug therapy
- Hyperphosphatemia/genetics
- Hyperphosphatemia/metabolism
- Interferons/metabolism
- Metacarpus/abnormalities
- Metacarpus/metabolism
- Muscular Diseases/drug therapy
- Muscular Diseases/genetics
- Muscular Diseases/metabolism
- Odontodysplasia/drug therapy
- Odontodysplasia/genetics
- Odontodysplasia/metabolism
- Osteoporosis/drug therapy
- Osteoporosis/genetics
- Osteoporosis/metabolism
- Phosphates/metabolism
- Progeria/drug therapy
- Progeria/genetics
- Progeria/metabolism
- Pseudoxanthoma Elasticum/drug therapy
- Pseudoxanthoma Elasticum/genetics
- Pseudoxanthoma Elasticum/metabolism
- Pulmonary Valve Stenosis/drug therapy
- Pulmonary Valve Stenosis/genetics
- Pulmonary Valve Stenosis/metabolism
- Vascular Calcification/drug therapy
- Vascular Calcification/genetics
- Vascular Calcification/metabolism
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Affiliation(s)
- Yvonne Nitschke
- Department of General Pediatrics, Münster University Children's Hospital, Albert-Schweitzer-Campus 1, D-48149, Münster, Germany
| | - Frank Rutsch
- Department of General Pediatrics, Münster University Children's Hospital, Albert-Schweitzer-Campus 1, D-48149, Münster, Germany.
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54
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Dilley KA, Voorhies AA, Luthra P, Puri V, Stockwell TB, Lorenzi H, Basler CF, Shabman RS. The Ebola virus VP35 protein binds viral immunostimulatory and host RNAs identified through deep sequencing. PLoS One 2017. [PMID: 28636653 PMCID: PMC5479518 DOI: 10.1371/journal.pone.0178717] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Ebola virus and Marburg virus are members of the Filovirdae family and causative agents of hemorrhagic fever with high fatality rates in humans. Filovirus virulence is partially attributed to the VP35 protein, a well-characterized inhibitor of the RIG-I-like receptor pathway that triggers the antiviral interferon (IFN) response. Prior work demonstrates the ability of VP35 to block potent RIG-I activators, such as Sendai virus (SeV), and this IFN-antagonist activity is directly correlated with its ability to bind RNA. Several structural studies demonstrate that VP35 binds short synthetic dsRNAs; yet, there are no data that identify viral immunostimulatory RNAs (isRNA) or host RNAs bound to VP35 in cells. Utilizing a SeV infection model, we demonstrate that both viral isRNA and host RNAs are bound to Ebola and Marburg VP35s in cells. By deep sequencing the purified VP35-bound RNA, we identified the SeV copy-back defective interfering (DI) RNA, previously identified as a robust RIG-I activator, as the isRNA bound by multiple filovirus VP35 proteins, including the VP35 protein from the West African outbreak strain (Makona EBOV). Moreover, RNAs isolated from a VP35 RNA-binding mutant were not immunostimulatory and did not include the SeV DI RNA. Strikingly, an analysis of host RNAs bound by wild-type, but not mutant, VP35 revealed that select host RNAs are preferentially bound by VP35 in cell culture. Taken together, these data support a model in which VP35 sequesters isRNA in virus-infected cells to avert RIG-I like receptor (RLR) activation.
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Affiliation(s)
- Kari A. Dilley
- Virology Group, J. Craig Venter Institute, Rockville, Maryland, United States of America
- * E-mail: (RSS); (KAD)
| | - Alexander A. Voorhies
- Infectious Disease Group, J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Priya Luthra
- Center for Microbial Pathogenesis, Georgia State University, Atlanta, Georgia, United States of America
| | - Vinita Puri
- Virology Group, J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Timothy B. Stockwell
- Virology Group, J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Hernan Lorenzi
- Infectious Disease Group, J. Craig Venter Institute, Rockville, Maryland, United States of America
| | - Christopher F. Basler
- Center for Microbial Pathogenesis, Georgia State University, Atlanta, Georgia, United States of America
| | - Reed S. Shabman
- Virology Group, J. Craig Venter Institute, Rockville, Maryland, United States of America
- * E-mail: (RSS); (KAD)
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55
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Xu XX, Wan H, Nie L, Shao T, Xiang LX, Shao JZ. RIG-I: a multifunctional protein beyond a pattern recognition receptor. Protein Cell 2017; 9:246-253. [PMID: 28593618 PMCID: PMC5829270 DOI: 10.1007/s13238-017-0431-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 05/16/2017] [Indexed: 12/21/2022] Open
Abstract
It was widely known that retinoic acid inducible gene I (RIG-I) functions as a cytosolic pattern recognition receptor that initiates innate antiviral immunity by detecting exogenous viral RNAs. However, recent studies showed that RIG-I participates in other various cellular activities by sensing endogenous RNAs under different circumstances. For example, RIG-I facilitates the therapy resistance and expansion of breast cancer cells and promotes T cell-independent B cell activation through interferon signaling activation by recognizing non-coding RNAs and endogenous retroviruses in certain situations. While in hepatocellular carcinoma and acute myeloid leukemia, RIG-I acts as a tumor suppressor through either augmenting STAT1 activation by competitively binding STAT1 against its negative regulator SHP1 or inhibiting AKT-mTOR signaling pathway by directly interacting with Src respectively. These new findings suggest that RIG-I plays more diverse roles in various cellular life activities, such as cell proliferation and differentiation, than previously known. Taken together, the function of RIG-I exceeds far beyond that of a pattern recognition receptor.
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Affiliation(s)
- Xiao-Xiao Xu
- Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Han Wan
- Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Li Nie
- Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Tong Shao
- Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Li-Xin Xiang
- Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China.
| | - Jian-Zhong Shao
- Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University, Hangzhou, 310058, China. .,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266235, China.
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56
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Abstract
RIG-I-like receptors (RLRs) are cytosolic innate immune sensors that detect pathogenic RNA and induce a systemic antiviral response. During the last decade, many studies focused on their molecular characterization and the identification of RNA agonists. Therefore, it became more and more clear that RLR activation needs to be carefully regulated, because constitutive signaling or detection of endogenous RNA through loss of specificity is detrimental. Here, we review the current understanding of RLR activation and selectivity. We specifically focus upon recent findings on the function of the helicase domain in discriminating between different RNAs, and whose malfunctioning causes serious autoimmune diseases.
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Affiliation(s)
- Charlotte Lässig
- From the Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität, 81377 Munich and
| | - Karl-Peter Hopfner
- From the Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität, 81377 Munich and
- the Center for Integrated Protein Sciences, 81377 Munich, Germany
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57
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Fitzgerald ME, Rawling DC, Potapova O, Ren X, Kohlway A, Pyle AM. Selective RNA targeting and regulated signaling by RIG-I is controlled by coordination of RNA and ATP binding. Nucleic Acids Res 2017; 45:1442-1454. [PMID: 28180316 PMCID: PMC5388420 DOI: 10.1093/nar/gkw816] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 08/31/2016] [Accepted: 09/03/2016] [Indexed: 12/25/2022] Open
Abstract
RIG-I is an innate immune receptor that detects and responds to infection by deadly RNA viruses such as influenza, and Hepatitis C. In the cytoplasm, RIG-I is faced with a difficult challenge: it must sensitively detect viral RNA while ignoring the abundance of host RNA. It has been suggested that RIG-I has a ‘proof-reading’ mechanism for rejecting host RNA targets, and that disruptions of this selectivity filter give rise to autoimmune diseases. Here, we directly monitor RNA proof-reading by RIG-I and we show that it is controlled by a set of conserved amino acids that couple RNA and ATP binding to the protein (Motif III). Mutations of this motif directly modulate proof-reading by eliminating or enhancing selectivity for viral RNA, with major implications for autoimmune disease and cancer. More broadly, the results provide a physical explanation for the ATP-gated behavior of SF2 RNA helicases and receptor proteins.
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MESH Headings
- Adenosine Triphosphatases/chemistry
- Adenosine Triphosphatases/genetics
- Adenosine Triphosphatases/metabolism
- Adenosine Triphosphate/metabolism
- Amino Acid Substitution
- Autoimmunity
- Binding Sites/genetics
- DEAD Box Protein 58/genetics
- DEAD Box Protein 58/immunology
- DEAD Box Protein 58/metabolism
- HEK293 Cells
- Humans
- Immunity, Innate
- Models, Molecular
- Mutagenesis, Site-Directed
- Neoplasms/genetics
- Neoplasms/metabolism
- Protein Interaction Domains and Motifs
- RNA/chemistry
- RNA/genetics
- RNA/metabolism
- RNA Viruses/genetics
- RNA Viruses/immunology
- RNA Viruses/pathogenicity
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Receptors, Immunologic
- Receptors, Pattern Recognition/chemistry
- Receptors, Pattern Recognition/genetics
- Receptors, Pattern Recognition/metabolism
- Signal Transduction
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Affiliation(s)
- Megan E. Fitzgerald
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - David C. Rawling
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Olga Potapova
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
| | - Xiaoming Ren
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Andrew Kohlway
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Anna Marie Pyle
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
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58
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Abstract
Organisms throughout biology need to maintain the integrity of their genome. From bacteria to vertebrates, life has established sophisticated mechanisms to detect and eliminate foreign genetic material or to restrict its function and replication. Tremendous progress has been made in the understanding of these mechanisms which keep foreign or unwanted nucleic acids from viruses or phages in check. Mechanisms reach from restriction-modification systems and CRISPR/Cas in bacteria and archaea to RNA interference and immune sensing of nucleic acids, altogether integral parts of a system which is now appreciated as nucleic acid immunity. With inherited receptors and acquired sequence information, nucleic acid immunity comprises innate and adaptive components. Effector functions include diverse nuclease systems, intrinsic activities to directly restrict the function of foreign nucleic acids (e.g., PKR, ADAR1, IFIT1), and extrinsic pathways to alert the immune system and to elicit cytotoxic immune responses. These effects act in concert to restrict viral replication and to eliminate virus-infected cells. The principles of nucleic acid immunity are highly relevant for human disease. Besides its essential contribution to antiviral defense and restriction of endogenous retroelements, dysregulation of nucleic acid immunity can also lead to erroneous detection and response to self nucleic acids then causing sterile inflammation and autoimmunity. Even mechanisms of nucleic acid immunity which are not established in vertebrates are relevant for human disease when they are present in pathogens such as bacteria, parasites, or helminths or in pathogen-transmitting organisms such as insects. This review aims to provide an overview of the diverse mechanisms of nucleic acid immunity which mostly have been looked at separately in the past and to integrate them under the framework nucleic acid immunity as a basic principle of life, the understanding of which has great potential to advance medicine.
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Affiliation(s)
- G Hartmann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Bonn, Germany.
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59
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Abstract
Viruses have evolved a remarkable array of strategies to escape the host's innate immune responses. In this issue of Cell Host & Microbe, Zhao et al. (2016b) reveal a viral strategy to inactivate RIG-I signaling that relies on deamidation of RIG-I.
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Affiliation(s)
- Dominique Garcin
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva 4, Switzerland.
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60
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Zhao J, Zeng Y, Xu S, Chen J, Shen G, Yu C, Knipe D, Yuan W, Peng J, Xu W, Zhang C, Xia Z, Feng P. A Viral Deamidase Targets the Helicase Domain of RIG-I to Block RNA-Induced Activation. Cell Host Microbe 2016; 20:770-784. [PMID: 27866900 DOI: 10.1016/j.chom.2016.10.011] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/08/2016] [Accepted: 10/07/2016] [Indexed: 12/31/2022]
Abstract
RIG-I detects double-stranded RNA (dsRNA) to trigger antiviral cytokine production. Protein deamidation is emerging as a post-translational modification that chiefly regulates protein function. We report here that UL37 of herpes simplex virus 1 (HSV-1) is a protein deamidase that targets RIG-I to block RNA-induced activation. Mass spectrometry analysis identified two asparagine residues in the helicase 2i domain of RIG-I that were deamidated upon UL37 expression or HSV-1 infection. Deamidation rendered RIG-I unable to sense viral dsRNA, thus blocking its ability to trigger antiviral immune responses and restrict viral replication. Purified full-length UL37 and its carboxyl-terminal fragment were sufficient to deamidate RIG-I in vitro. Uncoupling RIG-I deamidation from HSV-1 infection, by engineering deamidation-resistant RIG-I or introducing deamidase-deficient UL37 into the HSV-1 genome, restored RIG-I activation and antiviral immune signaling. Our work identifies a viral deamidase and extends the paradigm of deamidation-mediated suppression of innate immunity by microbial pathogens.
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Affiliation(s)
- Jun Zhao
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Yi Zeng
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Simin Xu
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Jie Chen
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA; Division of General Surgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Guobo Shen
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Caiqun Yu
- Department of Chemistry, Dornsife College of Arts, Letters, and Sciences, University of Southern California, LJS 369, 840 Downey Way, Los Angeles, CA 90089, USA
| | - David Knipe
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Weiming Yuan
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Jian Peng
- Division of General Surgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Wenqing Xu
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Chao Zhang
- Department of Chemistry, Dornsife College of Arts, Letters, and Sciences, University of Southern California, LJS 369, 840 Downey Way, Los Angeles, CA 90089, USA
| | - Zanxian Xia
- State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Pinghui Feng
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA.
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61
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Cao X, Li Y, Jin X, Li Y, Guo F, Jin T. Molecular mechanism of divalent-metal-induced activation of NS3 helicase and insights into Zika virus inhibitor design. Nucleic Acids Res 2016; 44:10505-10514. [PMID: 27915293 PMCID: PMC5137455 DOI: 10.1093/nar/gkw941] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/03/2016] [Accepted: 10/18/2016] [Indexed: 12/31/2022] Open
Abstract
Zika virus has attracted increasing attention because of its potential for causing human neural disorders, including microcephaly in infants and Guillain–Barré syndrome. Its NS3 helicase domain plays critical roles in NTP-dependent RNA unwinding and translocation during viral replication. Our structural analysis revealed a pre-activation state of NS3 helicase in complex with GTPγS, in which the triphosphate adopts a compact conformation in the absence of any divalent metal ions. In contrast, in the presence of a divalent cation, GTPγS adopts an extended conformation, and the Walker A motif undergoes substantial conformational changes. Both features contribute to more extensive interactions between the GTPγS and the enzyme. Thus, this study provides structural evidence on the allosteric modulation of MgNTP2− on the NS3 helicase activity. Furthermore, the compact conformation of inhibitory NTP identified in this study provides precise information for the rational drug design of small molecule inhibitors for the treatment of ZIKV infection.
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Affiliation(s)
- Xiaocong Cao
- Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, CAS Center for Excellence in Molecular Cell Science, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Yajuan Li
- Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, CAS Center for Excellence in Molecular Cell Science, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Xiangyu Jin
- Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, CAS Center for Excellence in Molecular Cell Science, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Yuelong Li
- Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, CAS Center for Excellence in Molecular Cell Science, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Feng Guo
- School of Medicine, Stanford University, Stanford, CA 94305, USA
| | - Tengchuan Jin
- Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, CAS Center for Excellence in Molecular Cell Science, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China
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62
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Omura H, Oikawa D, Nakane T, Kato M, Ishii R, Ishitani R, Tokunaga F, Nureki O. Structural and Functional Analysis of DDX41: a bispecific immune receptor for DNA and cyclic dinucleotide. Sci Rep 2016; 6:34756. [PMID: 27721487 PMCID: PMC5056382 DOI: 10.1038/srep34756] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 09/15/2016] [Indexed: 11/22/2022] Open
Abstract
In the innate immune system, pattern recognition receptors (PRRs) specifically recognize ligands derived from bacteria or viruses, to trigger the responsible downstream pathways. DEAD box protein 41 (DDX41) is an intracellular PRR that triggers the downstream pathway involving the adapter STING, the kinase TBK1, and the transcription factor IRF3, to activate the type I interferon response. DDX41 is unique in that it recognizes two different ligands; i.e., double-stranded DNA (dsDNA) and cyclic dinucleotides (CDN), via its DEAD domain. However, the structural basis for the ligand recognition by the DDX41 DEAD domain has remained elusive. Here, we report two crystal structures of the DDX41 DEAD domain in apo forms, at 1.5 and 2.2 Å resolutions. A comparison of the two crystal structures revealed the flexibility in the ATP binding site, suggesting its formation upon ATP binding. Structure-guided functional analyses in vitro and in vivo demonstrated the overlapped binding surface for dsDNA and CDN, which is distinct from the ATP-binding site. We propose that the structural rearrangement of the ATP binding site is crucial for the release of ADP, enabling the fast turnover of DDX41 for the dsDNA/CDN-induced STING activation pathway.
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Affiliation(s)
- Hiroki Omura
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Daisuke Oikawa
- Laboratory of Molecular Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371-8512, Japan.,Department of Pathobiochemistry, Osaka City University, Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan
| | - Takanori Nakane
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Megumi Kato
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Ryohei Ishii
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Ryuichiro Ishitani
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Fuminori Tokunaga
- Laboratory of Molecular Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371-8512, Japan.,Department of Pathobiochemistry, Osaka City University, Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan
| | - Osamu Nureki
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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63
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Roers A, Hiller B, Hornung V. Recognition of Endogenous Nucleic Acids by the Innate Immune System. Immunity 2016; 44:739-54. [PMID: 27096317 DOI: 10.1016/j.immuni.2016.04.002] [Citation(s) in RCA: 366] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 02/14/2016] [Accepted: 04/01/2016] [Indexed: 12/25/2022]
Abstract
Recognition of DNA and RNA by endosomal and cytosolic sensors constitutes a central element in the detection of microbial invaders by the innate immune system. However, the capacity of these sensors to discriminate between microbial and endogenous nucleic acids is limited. Over the past few years, evidence has accumulated to suggest that endogenous DNA or RNA species can engage nucleic-acid-sensing pattern-recognition receptors that can trigger or sustain detrimental pathology. Here, we review principles of how the activation of innate sensors by host nucleic acids is prevented in the steady state and discuss four important determinants of whether a nucleic-acid-driven innate response is mounted. These include structural features of the ligand being sensed, the subcellular location and quantity of pathogen-derived or endogenous nucleic acids, and the regulation of sensor-activation thresholds. Furthermore, we emphasize disease mechanisms initiated by failure to discriminate self from non-self in nucleic acid detection.
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Affiliation(s)
- Axel Roers
- Institute for Immunology, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, 01069 Dresden, Germany
| | - Björn Hiller
- Institute of Molecular Medicine, University Hospital Bonn, 53127 Bonn, Germany
| | - Veit Hornung
- Institute of Molecular Medicine, University Hospital Bonn, 53127 Bonn, Germany; Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, 81377 Munich, Germany; Center for Integrated Protein Science Munich, 81377 Munich, Germany.
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64
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RNAs Containing Modified Nucleotides Fail To Trigger RIG-I Conformational Changes for Innate Immune Signaling. mBio 2016; 7:mBio.00833-16. [PMID: 27651356 PMCID: PMC5030355 DOI: 10.1128/mbio.00833-16] [Citation(s) in RCA: 158] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Invading pathogen nucleic acids are recognized and bound by cytoplasmic (retinoic acid-inducible gene I [RIG-I]-like) and membrane-bound (Toll-like) pattern recognition receptors to activate innate immune signaling. Modified nucleotides, when present in RNA molecules, diminish the magnitude of these signaling responses. However, mechanisms explaining the blunted signaling have not been elucidated. In this study, we used several independent biological assays, including inhibition of virus replication, RIG-I:RNA binding assays, and limited trypsin digestion of RIG-I:RNA complexes, to begin to understand how RNAs containing modified nucleotides avoid or suppress innate immune signaling. The experiments were based on a model innate immune activating RNA molecule, the polyU/UC RNA domain of hepatitis C virus, which was transcribed in vitro with canonical nucleotides or with one of eight modified nucleotides. The approach revealed signature assay responses associated with individual modified nucleotides or classes of modified nucleotides. For example, while both N-6-methyladenosine (m6A) and pseudouridine nucleotides correlate with diminished signaling, RNA containing m6A modifications bound RIG-I poorly, while RNA containing pseudouridine bound RIG-I with high affinity but failed to trigger the canonical RIG-I conformational changes associated with robust signaling. These data advance understanding of RNA-mediated innate immune signaling, with additional relevance for applying nucleotide modifications to RNA therapeutics. The innate immune system provides the first response to virus infections and must distinguish between host and pathogen nucleic acids to mount a protective immune response without activating autoimmune responses. While the presence of nucleotide modifications in RNA is known to correlate with diminished innate immune signaling, the underlying mechanisms have not been explored. The data reported here are important for defining mechanistic details to explain signaling suppression by RNAs containing modified nucleotides. The results suggest that RNAs containing modified nucleotides interrupt signaling at early steps of the RIG-I-like innate immune activation pathway and also that nucleotide modifications with similar chemical structures can be organized into classes that suppress or evade innate immune signaling steps. These data contribute to defining the molecular basis for innate immune signaling suppression by RNAs containing modified nucleotides. The results have important implications for designing therapeutic RNAs that evade innate immune detection.
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65
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Baek YM, Yoon S, Hwang YE, Kim DE. Dependence of RIG-I Nucleic Acid-Binding and ATP Hydrolysis on Activation of Type I Interferon Response. Immune Netw 2016; 16:249-55. [PMID: 27574504 PMCID: PMC5002451 DOI: 10.4110/in.2016.16.4.249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/23/2016] [Accepted: 07/02/2016] [Indexed: 01/21/2023] Open
Abstract
Exogenous nucleic acids induce an innate immune response in mammalian host cells through activation of the retinoic acid-inducible gene I (RIG-I). We evaluated RIG-I protein for RNA binding and ATPase stimulation with RNA ligands to investigate the correlation with the extent of immune response through RIG-I activation in cells. RIG-I protein favored blunt-ended, double-stranded RNA (dsRNA) ligands over sticky-ended dsRNA. Moreover, the presence of the 5'-triphosphate (5'-ppp) moiety in dsRNA further enhanced binding affinity to RIG-I. Two structural motifs in RNA, blunt ends in dsRNA and 5'-ppp, stimulated the ATP hydrolysis activity of RIG-I. These structural motifs also strongly induced IFN expression as an innate immune response in cells. Therefore, we suggest that IFN induction through RIG-I activation is mainly determined by structural motifs in dsRNA that increase its affinity for RIG-I protein and stimulate ATPase activity in RIG-I.
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Affiliation(s)
- Yu Mi Baek
- Department of Bioscience and Biotechnology, Konkuk University, Seoul 05902, Korea
| | - Soojin Yoon
- Department of Bioscience and Biotechnology, Konkuk University, Seoul 05902, Korea
| | - Yeo Eun Hwang
- Department of Bioscience and Biotechnology, Konkuk University, Seoul 05902, Korea
| | - Dong-Eun Kim
- Department of Bioscience and Biotechnology, Konkuk University, Seoul 05902, Korea
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66
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Abstract
The ability to distinguish between self and nonself is the fundamental basis of the immune system in all organisms. The conceptual distinction between self and nonself, however, breaks down when it comes to endogenous retroviruses and other retroelements. While some retroelements retain the virus-like features including the capacity to replicate and reinvade the host genome, most have become inactive through mutations or host epigenetic silencing. And yet, accumulating evidence suggests that endogenous retroelements, both active and inactive, play important roles not only in pathogenesis of immune disorders, but also in proper functioning of the immune system. This review discusses the recent development in our understanding of the interaction between retroelements and the host innate immune system. In particular, it focuses on the impact of retroelement transcripts on the viral RNA sensors such as Toll-like receptors, RIG-I-like receptors, protein kinase R, and the inflammasomes.
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Affiliation(s)
- X Mu
- Harvard Medical School, Boston, MA, United States; Boston Children's Hospital, Boston, MA, United States
| | - S Ahmad
- Harvard Medical School, Boston, MA, United States; Boston Children's Hospital, Boston, MA, United States
| | - S Hur
- Harvard Medical School, Boston, MA, United States; Boston Children's Hospital, Boston, MA, United States.
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67
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Abstract
Immune sensing of foreign nucleic acids among abundant self nucleic acids is a hallmark of virus detection and antiviral defence. Efficient antiviral defence requires a balanced process of sensing foreign nucleic acids and ignoring self nucleic acids. This balance is accomplished by a multilevel, fail-safe system which combines immune sensing of pathogen-specific nucleic acid structures with specific labelling of self nucleic acids and nuclease-mediated degradation. Cellular localization of nucleic acids, nucleic acid secondary structure, nucleic acid sequence and chemical modification all contribute to selective recognition of foreign nucleic acids. Nucleic acid sensing occurs in immune cells and non-immune cells and results in antiviral responses that include the induction of antiviral effector proteins, the secretion of cytokines alarming neighbouring cells, the secretion of chemokines, which attract immune cells, and the induction of cell death. Vertebrate cells cannot completely avoid the occurrence of endogenous self nucleic acid structures with immunostimulatory properties. Therefore, additional mechanisms involving self-nucleic acid modification and nuclease-mediated degradation are necessary to diminish uncontrolled immune activation. Viruses have established sophisticated mechanisms to exploit and adopt endogenous tolerance mechanisms or to avoid the presentation of characteristic molecular features recognized by nucleic acid sensing receptors.
The detection of viruses by the immune system is mediated predominantly by the sensing of nucleic acids. Here, the authors review our current understanding of how this complex immune sensory system discriminates self from non-self nucleic acids to reliably detect pathogenic viruses, and discuss the future perspectives and implications for human disease. Innate immunity against pathogens relies on an array of immune receptors to detect molecular patterns that are characteristic of the pathogens, including receptors that are specialized in the detection of foreign nucleic acids. In vertebrates, nucleic acid sensing is the dominant antiviral defence pathway. Stimulation of nucleic acid receptors results in antiviral immune responses with the production of type I interferon (IFN), as well as the expression of IFN-stimulated genes, which encode molecules such as cell-autonomous antiviral effector proteins. This Review summarizes the tremendous progress that has been made in understanding how this sophisticated immune sensory system discriminates self from non-self nucleic acids in order to reliably detect pathogenic viruses.
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Affiliation(s)
- Martin Schlee
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany
| | - Gunther Hartmann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital, University of Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany
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68
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Tremblay N, Baril M, Chatel-Chaix L, Es-Saad S, Park AY, Koenekoop RK, Lamarre D. Spliceosome SNRNP200 Promotes Viral RNA Sensing and IRF3 Activation of Antiviral Response. PLoS Pathog 2016; 12:e1005772. [PMID: 27454487 PMCID: PMC4959778 DOI: 10.1371/journal.ppat.1005772] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 06/27/2016] [Indexed: 12/18/2022] Open
Abstract
Spliceosomal SNRNP200 is a Ski2-like RNA helicase that is associated with retinitis pigmentosa 33 (RP33). Here we found that SNRNP200 promotes viral RNA sensing and IRF3 activation through the ability of its amino-terminal Sec63 domain (Sec63-1) to bind RNA and to interact with TBK1. We show that SNRNP200 relocalizes into TBK1-containing cytoplasmic structures upon infection, in contrast to the RP33-associated S1087L mutant, which is also unable to rescue antiviral response of SNRNP200 knockdown cells. This functional rescue correlates with the Sec63-1-mediated binding of viral RNA. The hindered IFN-β production of knockdown cells was further confirmed in peripheral blood cells of RP33 patients bearing missense mutation in SNRNP200 upon infection with Sendai virus (SeV). This work identifies a novel immunoregulatory role of the spliceosomal SNRNP200 helicase as an RNA sensor and TBK1 adaptor for the activation of IRF3-mediated antiviral innate response. The innate immune system is the first line of defense against pathogens and relies on the recognition of molecular structures specific to pathogens by sensor receptors. These receptors activate a signaling cascade and induce a protective cellular innate immune response. In this study, we provide evidence for a role of the spliceosomal SNRNP200 RNA helicase in promoting antiviral response that is clearly distinguishable of the one in pre-mRNA splicing. The depletion of SNRNP200 in human cells resulted in a reduced interferon-β (IFNB1) production and increased susceptibility to viral infection. We showed that SNRNP200 positively regulates activation of the key transcription factor IRF3 via interaction with TANK kinase 1 (TBK1). Upon infection, SNRNP200 binds viral RNA and relocalizes into TBK1-containing cytoplasmic structures to promote IRF3 activation and IFNB1 production. Of clinical relevance, we observed a significantly hindered antiviral response of PBMCs from patients carrying a dominant SNRNP200 mutation associated with retina pigmentosa type 33 (RP33), an inherited degenerative eye disease. We showed that the RP33-associated S1087L SNRNP200 mutant has lost the ability to bind RNA and that its expression fails to rescue antiviral response in SNRNP200 silenced cells. Our study provides new insights into a role within the antiviral response for spliceosome SNRNP200 helicase as an RNA sensor and TBK1 adaptor in IRF3 signaling.
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Affiliation(s)
- Nicolas Tremblay
- Centre de Recherche du CHUM (CRCHUM), Montréal, Québec, Canada
- Faculté de Médecine, Université de Montréal, Montréal, Canada
| | - Martin Baril
- Centre de Recherche du CHUM (CRCHUM), Montréal, Québec, Canada
| | | | - Salwa Es-Saad
- Centre de Recherche du CHUM (CRCHUM), Montréal, Québec, Canada
| | - Alex Young Park
- Centre de Recherche du CHUM (CRCHUM), Montréal, Québec, Canada
- Faculté de Médecine, Université de Montréal, Montréal, Canada
| | - Robert K. Koenekoop
- Departments of Pediatric Surgery, Human Genetics and Ophthalmology, McGill University, Montréal, Canada
| | - Daniel Lamarre
- Centre de Recherche du CHUM (CRCHUM), Montréal, Québec, Canada
- Faculté de Médecine, Université de Montréal, Montréal, Canada
- * E-mail:
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69
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Buers I, Nitschke Y, Rutsch F. Novel interferonopathies associated with mutations in RIG-I like receptors. Cytokine Growth Factor Rev 2016; 29:101-7. [PMID: 26993858 DOI: 10.1016/j.cytogfr.2016.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Type I interferonopathies are a relatively new class of inherited autoimmune disorders associated with an inborn elevated interferon response. Activation of cytosolic receptors which recognize viral double stranded RNA including the RIG-I (retinoic acid-inducible gene I) like receptors RIG-I and MDA5 (melanoma differentiation-associated gene 5) has been shown to induce the transcription of type I interferon genes. Within recent years, with the help of next generation sequencing techniques in syndromic families, mutations in the genes encoding for RIG-I and MDA5 have been identified to cause rare diseases including Aicardi-Goutières syndrome, Systemic Lupus Erythematosus in certain individuals as well as classic and atypical Singleton-Merten syndrome. Patients carrying mono-allelic mutations in MDA5 and RIG-I show constitutive activation of the RIG-I receptors and downstream signalling associated with increased type I interferon production. Although differing in the degree of phenotypic expression and severity, the phenotype of these "novel" diseases shows a considerable overlap reflecting their common pathogenetic pathway.
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Affiliation(s)
- Insa Buers
- Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Building A1, 48149 Muenster, Germany.
| | - Yvonne Nitschke
- Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Building A1, 48149 Muenster, Germany.
| | - Frank Rutsch
- Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Building A1, 48149 Muenster, Germany.
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70
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Blango MG, Bass BL. Identification of the long, edited dsRNAome of LPS-stimulated immune cells. Genome Res 2016; 26:852-62. [PMID: 27197207 PMCID: PMC4889969 DOI: 10.1101/gr.203992.116] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 04/18/2016] [Indexed: 12/31/2022]
Abstract
Endogenous double-stranded RNA (dsRNA) must be intricately regulated in mammals to prevent aberrant activation of host inflammatory pathways by cytosolic dsRNA binding proteins. Here, we define the long, endogenous dsRNA repertoire in mammalian macrophages and monocytes during the inflammatory response to bacterial lipopolysaccharide. Hyperediting by adenosine deaminases that act on RNA (ADAR) enzymes was quantified over time using RNA-seq data from activated mouse macrophages to identify 342 Editing Enriched Regions (EERs), indicative of highly structured dsRNA. Analysis of publicly available data sets for samples of human peripheral blood monocytes resulted in discovery of 3438 EERs in the human transcriptome. Human EERs had predicted secondary structures that were significantly more stable than those of mouse EERs and were located primarily in introns, whereas nearly all mouse EERs were in 3' UTRs. Seventy-four mouse EER-associated genes contained an EER in the orthologous human gene, although nucleotide sequence and position were only rarely conserved. Among these conserved EER-associated genes were several TNF alpha-signaling genes, including Sppl2a and Tnfrsf1b, important for processing and recognition of TNF alpha, respectively. Using publicly available data and experimental validation, we found that a significant proportion of EERs accumulated in the nucleus, a strategy that may prevent aberrant activation of proinflammatory cascades in the cytoplasm. The observation of many ADAR-edited dsRNAs in mammalian immune cells, a subset of which are in orthologous genes of mouse and human, suggests a conserved role for these structured regions.
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Affiliation(s)
- Matthew G Blango
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
| | - Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
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71
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Leung DW, Amarasinghe GK. When your cap matters: structural insights into self vs non-self recognition of 5' RNA by immunomodulatory host proteins. Curr Opin Struct Biol 2016; 36:133-41. [PMID: 26916433 PMCID: PMC5218996 DOI: 10.1016/j.sbi.2016.02.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 02/04/2016] [Indexed: 12/13/2022]
Abstract
Cytosolic recognition of viral RNA is important for host innate immune responses. Differential recognition of self vs non-self RNA is a considerable challenge as the inability to differentiate may trigger aberrant immune responses. Recent work identified the composition of the RNA 5', including the 5' cap and its methylation state, as an important determinant of recognition by the host. Recent studies have advanced our understanding of the modified 5' RNA recognition and viral antagonism of RNA receptors. Here, we will discuss RIG-I and IFIT proteins as examples of host proteins that detect dsRNA and ssRNA, respectively.
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Affiliation(s)
- Daisy W Leung
- Department of Pathology and Immunology, Washington University School of Medicine, Campus Box 8118, 660 South Euclid Avenue, St Louis, MO 63110, United States.
| | - Gaya K Amarasinghe
- Department of Pathology and Immunology, Washington University School of Medicine, Campus Box 8118, 660 South Euclid Avenue, St Louis, MO 63110, United States.
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