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Zheng H, Wu P, Bonnet PA. Recent Advances on Small-Molecule Antagonists Targeting TLR7. Molecules 2023; 28:molecules28020634. [PMID: 36677692 PMCID: PMC9865772 DOI: 10.3390/molecules28020634] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 12/28/2022] [Accepted: 12/30/2022] [Indexed: 01/11/2023] Open
Abstract
Toll-like receptor 7 (TLR7) is a class of pattern recognition receptors (PRRs) recognizing the pathogen-associated elements and damage and as such is a major player in the innate immune system. TLR7 triggers the release of pro-inflammatory cytokines or type-I interferons (IFN), which is essential for immunoregulation. Increasing reports also highlight that the abnormal activation of endosomal TLR7 is implicated in various immune-related diseases, carcinogenesis as well as the proliferation of human immunodeficiency virus (HIV). Hence, the design and development of potent and selective TLR7 antagonists based on small molecules or oligonucleotides may offer new tools for the prevention and management of such diseases. In this review, we offer an updated overview of the main structural features and therapeutic potential of small-molecule antagonists of TLR7. Various heterocyclic scaffolds targeting TLR7 binding sites are presented: pyrazoloquinoxaline, quinazoline, purine, imidazopyridine, pyridone, benzanilide, pyrazolopyrimidine/pyridine, benzoxazole, indazole, indole, and quinoline. Additionally, their structure-activity relationships (SAR) studies associated with biological activities and protein binding modes are introduced.
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Affiliation(s)
- Haoyang Zheng
- Faculty of Pharmacy, Montpellier University, 34093 Montpellier, France
| | - Peiyang Wu
- School of Life Sciences, Shanghai Normal University, Shanghai 200234, China
| | - Pierre-Antoine Bonnet
- Institut des Biomolécules Max Mousseron IBMM, Ecole Nationale Supérieure de Chimie de Montpellier ENSCM, Montpellier University, Centre National de La Recherche Scientifique CNRS, 34093 Montpellier, France
- Correspondence:
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Radwan Y, Afonin KA, Johnson MB. Assessment of Intracellular Compartmentalization of RNA Nanostructures. Methods Mol Biol 2023; 2709:211-228. [PMID: 37572283 PMCID: PMC10482314 DOI: 10.1007/978-1-0716-3417-2_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/14/2023]
Abstract
Nucleic acid nanoparticles (NANPs) are extensively investigated as diagnostic and therapeutic tools. These innovative particles can be composed of RNA, DNA, and/or modified nucleic acids. Due to the regulatory role of nucleic acids in the cellular system, NANPs have the ability to identify target molecules and regulate expression of genes in disease pathways. However, translation of NANPs in clinical settings is hindered due to inefficient intracellular delivery, chemical instability, and off-target immunostimulatory effects following immune recognition. The composition of nucleic acids forming NANPs has been demonstrated to influence immunorecognition, subcellular compartmentalization, and physicochemical properties of NANPs. This chapter first outlines the methods used to generate a panel of NANPs with a uniform shape, size, charge, sequence, and connectivity. This includes the procedures for replacing the RNA strands with DNA or chemical analogs in the designated NANPs. Second, this chapter will also describe experiments to assess the effect of the chemical modification on enzymatic and thermodynamic stability, delivery efficiency, and subcellular compartmentalization of NANPs.
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Affiliation(s)
- Yasmine Radwan
- Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - Kirill A Afonin
- Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - M Brittany Johnson
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, USA.
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3
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Application of mutational profiling: New functional analyses reveal the tRNA recognition mechanism of tRNA m 1A22 methyltransferase. J Biol Chem 2022; 299:102759. [PMID: 36462666 PMCID: PMC9801127 DOI: 10.1016/j.jbc.2022.102759] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 11/22/2022] [Accepted: 11/23/2022] [Indexed: 12/05/2022] Open
Abstract
Transfer RNAs undergo diverse posttranscriptional modifications to regulate a myriad of cellular events including translation, stress response, and viral replication. These posttranscriptional modifications are synthesized by site-specific modification enzymes. Recent RNA-seq techniques have revealed multiple features of tRNA such as tRNA abundance, tRNA modification, and tRNA structure. Here, we adapt a tRNA-sequencing technique and design a new functional analysis where we perform mutational profiling of tRNA modifications to gain mechanistic insights into how tRNA modification enzymes recognize substrate tRNA. Profiling of Geobacillus stearothermophilus tRNAs and protein orthology analysis predict the existence of natural modifications in 44 tRNA molecular species of G. stearothermophilus. We selected the 1-methyladenosine modification at position 22 (m1A22) and tRNA (m1A22) methyltransferase (TrmK) for further analysis. Relative quantification of m1A22 levels in 59 tRNA transcripts by mutational profiling reveals that TrmK selectively methylates a subset of tRNAs. Using 240 variants of tRNALeu transcripts, we demonstrate the conserved nucleosides including U8, A14, G15, G18, G19, U55, Purine57, and A58 are important for the methyl transfer reaction of TrmK. Additional biochemical experiments reveal that TrmK strictly recognizes U8, A14, G18, and U55 in tRNA. Furthermore, these findings from tRNALeu variants were crossvalidated using variants of three different tRNA species. Finally, a model of the TrmK-tRNA complex structure was constructed based on our findings and previous biochemical and structural studies by others. Collectively, our study expands functional analyses of tRNA modification enzyme in a high-throughput manner where our assay rapidly identifies substrates from a large pool of tRNAs.
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Nicolai M, Steinberg J, Obermann HL, Solis FV, Bartok E, Bauer S, Jung S. Identification of an Optimal TLR8 Ligand by Alternating the Position of 2′-O-Ribose Methylation. Int J Mol Sci 2022; 23:ijms231911139. [PMID: 36232437 PMCID: PMC9570189 DOI: 10.3390/ijms231911139] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/16/2022] [Accepted: 09/17/2022] [Indexed: 12/03/2022] Open
Abstract
Recognition of RNA by receptors of the innate immune system is regulated by various posttranslational modifications. Different single 2′-O-ribose (2′-O-) methylations have been shown to convert TLR7/TLR8 ligands into specific TLR8 ligands, so we investigated whether the position of 2′-O-methylation is crucial for its function. To this end, we designed different 2′-O-methylated RNA oligoribonucleotides (ORN), investigating their immune activity in various cell systems and analyzing degradation under RNase T2 treatment. We found that the 18S rRNA-derived TLR7/8 ligand, RNA63, was differentially digested as a result of 2′-O-methylation, leading to variations in TLR8 and TLR7 inhibition. The suitability of certain 2′-O-methylated RNA63 derivatives as TLR8 agonists was further demonstrated by the fact that other RNA sequences were only weak TLR8 agonists. We were thus able to identify specific 2′-O-methylated RNA derivatives as optimal TLR8 ligands.
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Affiliation(s)
- Marina Nicolai
- Institute for Immunology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Julia Steinberg
- Institute of Cardiovascular Immunology, University Hospital Bonn, University of Bonn, 53127 Bonn, Germany
| | | | | | - Eva Bartok
- Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn, University of Bonn, 53127 Bonn, Germany
| | - Stefan Bauer
- Institute for Immunology, Philipps-University Marburg, 35043 Marburg, Germany
| | - Stephanie Jung
- Institute of Cardiovascular Immunology, University Hospital Bonn, University of Bonn, 53127 Bonn, Germany
- Correspondence:
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Chandler M, Johnson B, Khisamutdinov E, Dobrovolskaia MA, Sztuba-Solinska J, Salem AK, Breyne K, Chammas R, Walter NG, Contreras LM, Guo P, Afonin KA. The International Society of RNA Nanotechnology and Nanomedicine (ISRNN): The Present and Future of the Burgeoning Field. ACS NANO 2021; 15:16957-16973. [PMID: 34677049 PMCID: PMC9023608 DOI: 10.1021/acsnano.0c10240] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The International Society of RNA Nanotechnology and Nanomedicine (ISRNN) hosts an annual meeting series focused on presenting the latest research achievements involving RNA-based therapeutics and strategies, aiming to expand their current biomedical applications while overcoming the remaining challenges of the burgeoning field of RNA nanotechnology. The most recent online meeting hosted a series of engaging talks and discussions from an international cohort of leading nanotechnologists that focused on RNA modifications and modulation, dynamic RNA structures, overcoming delivery limitations using a variety of innovative platforms and approaches, and addressing the newly explored potential for immunomodulation with programmable nucleic acid nanoparticles. In this Nano Focus, we summarize the main discussion points, conclusions, and future directions identified during this two-day webinar as well as more recent advances to highlight and to accelerate this exciting field.
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Affiliation(s)
- Morgan Chandler
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
| | - Brittany Johnson
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
| | - Emil Khisamutdinov
- Department of Chemistry, Ball State University, Muncie, Indiana 47304, United States
| | - Marina A Dobrovolskaia
- Nanotechnology Characterization Lab, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research sponsored by the National Cancer Institute, Frederick, Maryland 21702, United States
| | - Joanna Sztuba-Solinska
- Department of Biological Sciences, Auburn University, 120 W. Samford Avenue, Rouse Life Sciences Building, Auburn, Alabama 36849, United States
| | - Aliasger K Salem
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa 52242, United States
| | - Koen Breyne
- Molecular Neurogenetics Unit, Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachussets 02114, United States
| | - Roger Chammas
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
- Centro de Investigação Translacional em Oncologia, Departamento de Radiologia e Oncologia, Instituto do Cancer do Estado de São Paulo - ICESP, Faculdade de Medicina da Universidade de São Paulo - FMUSP, Avenida Dr. Arnaldo 251, Cerqueira César, São Paulo 01246-000, São Paulo, Brazil
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry and Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Lydia M Contreras
- McKetta Department of Chemical Engineering and Department of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78714, United States
| | - Peixuan Guo
- Center for RNA Nanobiotechnology and Nanomedicine, College of Pharmacy, Division of Pharmaceutics and Pharmaceutical Chemistry, College of Medicine, Dorothy M. Davis Heart and Lung Research Institute, James Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, United States
| | - Kirill A Afonin
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, North Carolina 28223, United States
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Abstract
The innate immune receptors in higher organisms have evolved to detect molecular signatures associated with pathogenic infection and trigger appropriate immune response. One common class of molecules utilized by the innate immune system for self vs. nonself discrimination is RNA, which is ironically present in all forms of life. To avoid self-RNA recognition, the innate immune sensors have evolved sophisticated discriminatory mechanisms that involve cellular RNA metabolic machineries. Posttranscriptional RNA modification and editing represent one such mechanism that allows cells to chemically tag the host RNAs as "self" and thus tolerate the abundant self-RNA molecules. In this chapter, we discuss recent advances in our understanding of the role of RNA editing/modification in the modulation of immune signaling pathways, and application of RNA editing/modification in RNA-based therapeutics and cancer immunotherapies.
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Johnson MB, Halman JR, Miller DK, Cooper JS, Khisamutdinov E, Marriott I, Afonin KA. The immunorecognition, subcellular compartmentalization, and physicochemical properties of nucleic acid nanoparticles can be controlled by composition modification. Nucleic Acids Res 2020; 48:11785-11798. [PMID: 33091133 PMCID: PMC7672449 DOI: 10.1093/nar/gkaa908] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/24/2020] [Accepted: 10/01/2020] [Indexed: 12/18/2022] Open
Abstract
Nucleic acid nanoparticles (NANPs) have become powerful new platforms as therapeutic and diagnostic tools due to the innate biological ability of nucleic acids to identify target molecules or silence genes involved in disease pathways. However, the clinical application of NANPs has been limited by factors such as chemical instability, inefficient intracellular delivery, and the triggering of detrimental inflammatory responses following innate immune recognition of nucleic acids. Here, we have studied the effects of altering the chemical composition of a circumscribed panel of NANPs that share the same connectivity, shape, size, charge and sequences. We show that replacing RNA strands with either DNA or chemical analogs increases the enzymatic and thermodynamic stability of NANPs. Furthermore, we have found that such composition changes affect delivery efficiency and determine subcellular localization, effects that could permit the targeted delivery of NANP-based therapeutics and diagnostics. Importantly, we have determined that altering NANP composition can dictate the degree and mechanisms by which cell immune responses are initiated. While RNA NANPs trigger both TLR7 and RIG-I mediated cytokine and interferon production, DNA NANPs stimulate minimal immune activation. Importantly, incorporation of 2'F modifications abrogates RNA NANP activation of TLR7 but permits RIG-I dependent immune responses. Furthermore, 2'F modifications of DNA NANPs significantly enhances RIG-I mediated production of both proinflammatory cytokines and interferons. Collectively this indicates that off-target effects may be reduced and/or desirable immune responses evoked based upon NANPs modifications. Together, our studies show that NANP composition provides a simple way of controlling the immunostimulatory potential, and physicochemical and delivery characteristics, of such platforms.
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Affiliation(s)
- Morgan Brittany Johnson
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - Justin R Halman
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Daniel K Miller
- Department of Chemistry, Ball State University, Muncie, IN 47306, USA
| | - Joseph S Cooper
- Department of Chemistry, Ball State University, Muncie, IN 47306, USA
| | | | - Ian Marriott
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - Kirill A Afonin
- Nanoscale Science Program, Department of Chemistry, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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8
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Bartok E, Hartmann G. Immune Sensing Mechanisms that Discriminate Self from Altered Self and Foreign Nucleic Acids. Immunity 2020; 53:54-77. [PMID: 32668228 PMCID: PMC7359798 DOI: 10.1016/j.immuni.2020.06.014] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 12/19/2022]
Abstract
All lifeforms have developed highly sophisticated systems equipped to detect altered self and non-self nucleic acids (NA). In vertebrates, NA-sensing receptors safeguard the integrity of the organism by detecting pathogens, dyshomeostasis and damage, and inducing appropriate responses to eliminate pathogens and reconstitute homeostasis. Effector mechanisms include i) immune signaling, ii) restriction of NA functions such as inhibition of mRNA translation, and iii) cell death pathways. An appropriate effector response is necessary for host defense, but dysregulated NA-sensing can lead to devastating autoimmune and autoinflammatory disease. Their inherent biochemical similarity renders the reliable distinction between self NA under homeostatic conditions and altered or exogenous NA particularly challenging. In this review, we provide an overview of recent progress in our understanding of the closely coordinated and regulated network of innate immune receptors, restriction factors, and nucleases to effectively respond to pathogens and maintain host integrity.
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Affiliation(s)
- Eva Bartok
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Gunther Hartmann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Venusberg-Campus 1, 53127 Bonn, Germany.
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Patra MC, Achek A, Kim GY, Panneerselvam S, Shin HJ, Baek WY, Lee WH, Sung J, Jeong U, Cho EY, Kim W, Kim E, Suh CH, Choi S. A Novel Small-Molecule Inhibitor of Endosomal TLRs Reduces Inflammation and Alleviates Autoimmune Disease Symptoms in Murine Models. Cells 2020; 9:E1648. [PMID: 32660060 PMCID: PMC7407930 DOI: 10.3390/cells9071648] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 06/30/2020] [Accepted: 07/07/2020] [Indexed: 12/31/2022] Open
Abstract
Toll-like receptors (TLRs) play a fundamental role in the inflammatory response against invading pathogens. However, the dysregulation of TLR-signaling pathways is implicated in several autoimmune/inflammatory diseases. Here, we show that a novel small molecule TLR-inhibitor (TAC5) and its derivatives TAC5-a, TAC5-c, TAC5-d, and TAC5-e predominantly antagonized poly(I:C) (TLR3)-, imiquimod (TLR7)-, TL8-506 (TLR8)-, and CpG-oligodeoxynucleotide (TLR9)-induced signaling pathways. TAC5 and TAC5-a significantly hindered the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), reduced the phosphorylation of mitogen-activated protein kinases, and inhibited the secretion of tumor necrosis factor-α (TNF-α) and interleukin-6. Besides, TAC5-a prevented the progression of psoriasis and systemic lupus erythematosus (SLE) in mice. Interestingly, TAC5 and TAC5-a did not affect Pam3CSK4 (TLR1/2)-, FSL-1 (TLR2/6)-, or lipopolysaccharide (TLR4)-induced TNF-α secretion, indicating their specificity towards endosomal TLRs (TLR3/7/8/9). Collectively, our data suggest that the TAC5 series of compounds are potential candidates for treating autoimmune diseases such as psoriasis or SLE.
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Affiliation(s)
- Mahesh Chandra Patra
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Asma Achek
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Gi-Young Kim
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Suresh Panneerselvam
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Hyeon-Jun Shin
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Wook-Yong Baek
- Department of Rheumatology, Ajou University School of Medicine, Suwon 16499, Korea; (W.-Y.B.); (C.-H.S.)
| | - Wang Hee Lee
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - June Sung
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Uisuk Jeong
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Eun-Young Cho
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Wook Kim
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Eunha Kim
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
| | - Chang-Hee Suh
- Department of Rheumatology, Ajou University School of Medicine, Suwon 16499, Korea; (W.-Y.B.); (C.-H.S.)
| | - Sangdun Choi
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea; (M.C.P.); (A.A.); (G.-Y.K.); (S.P.); (H.-J.S.); (W.H.L.); (J.S.); (U.J.); (E.-Y.C.); (W.K.); (E.K.)
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Patinote C, Karroum NB, Moarbess G, Cirnat N, Kassab I, Bonnet PA, Deleuze-Masquéfa C. Agonist and antagonist ligands of toll-like receptors 7 and 8: Ingenious tools for therapeutic purposes. Eur J Med Chem 2020; 193:112238. [PMID: 32203790 PMCID: PMC7173040 DOI: 10.1016/j.ejmech.2020.112238] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/11/2020] [Accepted: 03/12/2020] [Indexed: 12/17/2022]
Abstract
The discovery of the TLRs family and more precisely its functions opened a variety of gates to modulate immunological host responses. TLRs 7/8 are located in the endosomal compartment and activate a specific signaling pathway in a MyD88-dependant manner. According to their involvement into various autoimmune, inflammatory and malignant diseases, researchers have designed diverse TLRs 7/8 ligands able to boost or block the inherent signal transduction. These modulators are often small synthetic compounds and most act as agonists and to a much lesser extent as antagonists. Some of them have reached preclinical and clinical trials, and only one has been approved by the FDA and EMA, imiquimod. The key to the success of these modulators probably lies in their combination with other therapies as recently demonstrated. We gather in this review more than 360 scientific publications, reviews and patents, relating the extensive work carried out by researchers on the design of TLRs 7/8 modulators, which are classified firstly by their biological activities (agonist or antagonist) and then by their chemical structures, which total syntheses are not discussed here. This review also reports about 90 clinical cases, thereby showing the biological interest of these modulators in multiple pathologies.
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Affiliation(s)
- Cindy Patinote
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France.
| | - Nour Bou Karroum
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France; Tumorigenèse et Pharmacologie Antitumorale, Lebanese University, EDST, BP 90656, Fanar Jdeideh, Lebanon
| | - Georges Moarbess
- Tumorigenèse et Pharmacologie Antitumorale, Lebanese University, EDST, BP 90656, Fanar Jdeideh, Lebanon
| | - Natalina Cirnat
- IBMM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Issam Kassab
- Tumorigenèse et Pharmacologie Antitumorale, Lebanese University, EDST, BP 90656, Fanar Jdeideh, Lebanon
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Zhu C, Sun B, Nie A, Zhou Z. The tRNA-associated dysregulation in immune responses and immune diseases. Acta Physiol (Oxf) 2020; 228:e13391. [PMID: 31529760 DOI: 10.1111/apha.13391] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 08/31/2019] [Accepted: 09/08/2019] [Indexed: 12/12/2022]
Abstract
Transfer RNA (tRNA), often considered as a housekeeping molecule, mainly participates in protein translation by transporting amino acids to the ribosome. Nevertheless, accumulating evidence has shown that tRNAs are closely related to various physiological and pathological processes. The proper functioning of the immune system is the key to human health. The aim of this review is to investigate the relationships between tRNAs and the immune system. We detail the biogenesis and structure of tRNAs and summarize the pathogen tRNA-mediated infection and host responses. In addition, we address recent advances in different aspects of tRNA-associated dysregulation in immune responses and immune diseases, such as tRNA molecules, tRNA modifications, tRNA derivatives and tRNA aminoacylation. Therefore, tRNAs play an important role in immune regulation. Although our knowledge of tRNAs in the context of immunity remains, for the most part, unknown, this field deserves in-depth research to provide new ideas for the treatment of immune diseases.
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Affiliation(s)
- Chunsheng Zhu
- Department of Chinese Medicine The First Affiliated Hospital of Zhengzhou University Zhengzhou China
| | - Bao Sun
- Department of Clinical Pharmacology Xiangya Hospital Central South University Changsha China
- Hunan Key Laboratory of Pharmacogenetics Institute of Clinical Pharmacology Central South University Changsha China
| | - Anzheng Nie
- Department of Chinese Medicine The First Affiliated Hospital of Zhengzhou University Zhengzhou China
| | - Zheng Zhou
- Department of Chinese Medicine The First Affiliated Hospital of Zhengzhou University Zhengzhou China
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12
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Salem ESB, Vonberg AD, Borra VJ, Gill RK, Nakamura T. RNAs and RNA-Binding Proteins in Immuno-Metabolic Homeostasis and Diseases. Front Cardiovasc Med 2019; 6:106. [PMID: 31482095 PMCID: PMC6710452 DOI: 10.3389/fcvm.2019.00106] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 07/17/2019] [Indexed: 12/16/2022] Open
Abstract
The increasing prevalence of worldwide obesity has emerged as a major risk factor for type 2 diabetes (T2D), hepatosteatosis, and cardiovascular disease. Accumulating evidence indicates that obesity has strong inflammatory underpinnings tightly linked to the development of metabolic diseases. However, the molecular mechanisms by which obesity induces aberrant inflammation associated with metabolic diseases are not yet clearly defined. Recently, RNAs have emerged as important regulators of stress responses and metabolism. RNAs are subject to changes in modification status, higher-order structure, and cellular localization; all of which could affect the affinity for RNA-binding proteins (RBPs) and thereby modify the RNA-RBP networks. Proper regulation and management of RNA characteristics are fundamental to cellular and organismal homeostasis, as well as paramount to health. Identification of multiple single nucleotide polymorphisms (SNPs) within loci of fat mass- and obesity-associated protein (FTO) gene, an RNA demethylase, through genome-wide association studies (GWAS) of T2D, and functional assessments of FTO in mice, support the concept that disruption in RNA modifications leads to the development of human diseases including obesity and metabolic disorder. In obesity, dynamic alterations in modification and localization of RNAs appear to modulate the RNA-RBP networks and activate proinflammatory RBPs, such as double-stranded RNA (dsRNA)-dependent protein kinase (PKR), Toll-like receptor (TLR) 3 and TLR7, and RNA silencing machinery. These changes induce aberrant inflammation and the development of metabolic diseases. This review will describe the current understanding of the underlying causes of these common and altered characteristics of RNA-RBP networks which will pave the way for developing novel approaches to tackle the pandemic issue of obesity.
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Affiliation(s)
- Esam S B Salem
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Andrew D Vonberg
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Vishnupriya J Borra
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Rupinder K Gill
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States
| | - Takahisa Nakamura
- Division of Endocrinology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States.,Department of Metabolic Bioregulation, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan
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13
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Freund I, Buhl DK, Boutin S, Kotter A, Pichot F, Marchand V, Vierbuchen T, Heine H, Motorin Y, Helm M, Dalpke AH, Eigenbrod T. 2'- O-methylation within prokaryotic and eukaryotic tRNA inhibits innate immune activation by endosomal Toll-like receptors but does not affect recognition of whole organisms. RNA (NEW YORK, N.Y.) 2019; 25:869-880. [PMID: 31019095 PMCID: PMC6573781 DOI: 10.1261/rna.070243.118] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 04/20/2019] [Indexed: 05/10/2023]
Abstract
Bacterial RNA has emerged as an important activator of innate immune responses by stimulating Toll-like receptors TLR7 and TLR8 in humans. Guanosine 2'-O-methylation at position 18 (Gm18) in bacterial tRNA was shown to antagonize tRNA-induced TLR7/8 activation, suggesting a potential role of Gm18 as an immune escape mechanism. This modification also occurs in eukaryotic tRNA, yet a physiological immune function remained to be tested. We therefore set out to investigate the immune modulatory role of Gm18 in both prokaryotic and eukaryotic microorganisms, Escherichia coli and Saccharomyces cerevisiae, and in human cells. Using RiboMethSeq analysis we show that mutation of trmH in E. coli, trm3 in S. cereviase, and CRISPR/Cas9-induced knockout of TARBP1 in H. sapiens results in loss of Gm18 within tRNA. Lack of Gm18 across the kingdoms resulted in increased immunostimulation of peripheral blood mononuclear cells when activated by tRNA preparations. In E. coli, lack of 2'-O-methyltransferase trmH also enhanced immune stimulatory properties by whole cellular RNA. In contrast, lack of Gm18 in yeasts and human cells did not affect immunostimulation by whole RNA preparations. When using live E. coli bacteria, lack of trmH did not affect overall immune stimulation although we detected a defined TLR8/RNA-dependent gene expression signature upon E. coli infection. Together, these results demonstrate that Gm18 is a global immune inhibitory tRNA modification across the kingdoms and contributes to tRNA recognition by innate immune cells, but as an individual modification has insufficient potency to modulate recognition of the investigated microorganisms.
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Affiliation(s)
- Isabel Freund
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Daniel K Buhl
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Sébastien Boutin
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Annika Kotter
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Florian Pichot
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- IMoPA UMR7365 CNRS-Lorraine University, BioPole Lorraine University, 54500 Vandoeuvre-les-Nancy, France
| | - Virginie Marchand
- UMS2008 IBSLor, CNRS-Lorraine University-INSERM, BioPole Lorraine University, 54500 Vandoeuvre-les-Nancy, France
| | - Tim Vierbuchen
- Division of Innate Immunity, Research Center Borstel, 23845 Borstel, Germany
| | - Holger Heine
- Division of Innate Immunity, Research Center Borstel, 23845 Borstel, Germany
| | - Yuri Motorin
- IMoPA UMR7365 CNRS-Lorraine University, BioPole Lorraine University, 54500 Vandoeuvre-les-Nancy, France
| | - Mark Helm
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Alexander H Dalpke
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
- Institute of Medical Microbiology and Hygiene, Technical University Dresden, 01307 Dresden, Germany
| | - Tatjana Eigenbrod
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
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14
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Keller P, Freund I, Marchand V, Bec G, Huang R, Motorin Y, Eigenbrod T, Dalpke A, Helm M. Double methylation of tRNA-U54 to 2'-O-methylthymidine (Tm) synergistically decreases immune response by Toll-like receptor 7. Nucleic Acids Res 2019; 46:9764-9775. [PMID: 30102387 PMCID: PMC6182150 DOI: 10.1093/nar/gky644] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 08/02/2018] [Indexed: 12/25/2022] Open
Abstract
Sensing of nucleic acids for molecular discrimination between self and non-self is a challenging task for the innate immune system. RNA acts as a potent stimulus for pattern recognition receptors including in particular human Toll-like receptor 7 (TLR7). Certain RNA modifications limit potentially harmful self-recognition of endogenous RNA. Previous studies had identified the 2′-O-methylation of guanosine 18 (Gm18) within tRNAs as an antagonist of TLR7 leading to an impaired immune response. However, human tRNALys3 was non-stimulatory despite lacking Gm18. To identify the underlying molecular principle, interferon responses of human peripheral blood mononuclear cells to differentially modified tRNALys3 were determined. The investigation of synthetic modivariants allowed attributing a significant part of the immunosilencing effect to the 2′-O-methylthymidine (m5Um) modification at position 54. The effect was contingent upon the synergistic presence of both methyl groups at positions C5 and 2’O, as shown by the fact that neither Um54 nor m5U54 produced any effect alone. Testing permutations of the nucleobase at ribose-methylated position 54 suggested that the extent of silencing and antagonism of the TLR7 response was governed by hydrogen patterns and lipophilic interactions of the nucleobase. The results identify a new immune-modulatory endogenous RNA modification that limits TLR7 activation by RNA.
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Affiliation(s)
- Patrick Keller
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg-University of Mainz, Staudingerweg 5, D-55128 Mainz, Germany
| | - Isabel Freund
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Virginie Marchand
- Next Generation Sequencing Platform, UMS2008 Ingénierie Biologie Santé en Lorraine (IBSLor), BioPôle de l'Université de Lorraine Campus Biologie-Santé, 9, avenue de la Forêt de Haye, CS 50184, 54505 Vandoeuvre-les-Nancy, France
| | - Guillaume Bec
- Biophysics and Structural Biology Team, Unité Architecture et réactivité de l'ARN (UPR9002), Institut de Biologie Moléculaire et Cellulaire du CNRS, Université de Strasbourg, 15, rue René Descartes, F67084, Strasbourg cedex, France
| | - Raven Huang
- Department of Biochemistry, Center for Biophysics & Computational Biology, University of Illinois at Urbana-Champaign, 411 Roger Adams Lab., 600 S. Mathews Ave. Urbana, IL 61801, USA
| | - Yuri Motorin
- Laboratoire Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA) UMR7365 CNRS-UL, BioPôle de l'Université de Lorraine Campus Biologie-Santé, 9, avenue de la Forêt de Haye, CS 50184, 54505 Vandoeuvre-les-Nancy, France
| | - Tatjana Eigenbrod
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Alexander Dalpke
- Department of Infectious Diseases, Medical Microbiology and Hygiene, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Mark Helm
- Institute of Pharmacy and Biochemistry, Johannes Gutenberg-University of Mainz, Staudingerweg 5, D-55128 Mainz, Germany
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15
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Vierbuchen T, Stein K, Heine H. RNA is taking its Toll: Impact of RNA-specific Toll-like receptors on health and disease. Allergy 2019; 74:223-235. [PMID: 30475385 DOI: 10.1111/all.13680] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 11/08/2018] [Accepted: 11/20/2018] [Indexed: 12/13/2022]
Abstract
RNA-sensing Toll-like receptors (TLRs) are often described as antiviral receptors of the innate immune system. However, the past decade has shown that the function and relevance of these receptors are far more complex. They were found to be essential for the detection of various bacterial, archaeal, and eukaryotic microorganisms and facilitate the discrimination between dead and living microbes. The cytokine and interferon response profile that is triggered has the potential to improve the efficacy of next-generation vaccines and may prevent the development of asthma and allergy. Nevertheless, the ability to recognize foreign RNA comes with a cost as also damaged host cells can release nucleic acids that might induce an inappropriate immune response. Thus, it is not surprising that RNA-sensing TLRs play a key role in various autoimmune diseases. However, promising new inhibitors and antagonists are on the horizon to improve their treatment.
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Affiliation(s)
- Tim Vierbuchen
- Division of Innate Immunity Research Center Borstel – Leibniz Lung Center Borstel Germany
| | - Karina Stein
- Division of Innate Immunity Research Center Borstel – Leibniz Lung Center Borstel Germany
- Airway Research Center North (ARCN) German Center for Lung Research (DZL) Borstel Germany
| | - Holger Heine
- Division of Innate Immunity Research Center Borstel – Leibniz Lung Center Borstel Germany
- Airway Research Center North (ARCN) German Center for Lung Research (DZL) Borstel Germany
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16
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RNA Modifications Modulate Activation of Innate Toll-Like Receptors. Genes (Basel) 2019; 10:genes10020092. [PMID: 30699960 PMCID: PMC6410116 DOI: 10.3390/genes10020092] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 01/23/2019] [Accepted: 01/25/2019] [Indexed: 12/13/2022] Open
Abstract
Self/foreign discrimination by the innate immune system depends on receptors that identify molecular patterns as associated to pathogens. Among others, this group includes endosomal Toll-like receptors, among which Toll-like receptors (TLR) 3, 7, 8, and 13 recognize and discriminate mammalian from microbial, potentially pathogen-associated, RNA. One of the discriminatory principles is the recognition of endogenous RNA modifications. Previous work has identified a couple of RNA modifications that impede activation of TLR signaling when incorporated in synthetic RNA molecules. Of note, work that is more recent has now shown that RNA modifications in their naturally occurring context can have immune-modulatory functions: Gm, a naturally occurring ribose-methylation within tRNA resulted in a lack of TLR7 stimulation and within a defined sequence context acted as antagonist. Additional RNA modifications with immune-modulatory functions have now been identified and recent work also indicates that RNA modifications within the context of whole prokaryotic or eukaryotic cells are indeed used for immune-modulation. This review will discuss new findings and developments in the field of immune-modulatory RNA modifications.
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17
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Hori H, Kawamura T, Awai T, Ochi A, Yamagami R, Tomikawa C, Hirata A. Transfer RNA Modification Enzymes from Thermophiles and Their Modified Nucleosides in tRNA. Microorganisms 2018; 6:E110. [PMID: 30347855 PMCID: PMC6313347 DOI: 10.3390/microorganisms6040110] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 10/17/2018] [Accepted: 10/17/2018] [Indexed: 12/11/2022] Open
Abstract
To date, numerous modified nucleosides in tRNA as well as tRNA modification enzymes have been identified not only in thermophiles but also in mesophiles. Because most modified nucleosides in tRNA from thermophiles are common to those in tRNA from mesophiles, they are considered to work essentially in steps of protein synthesis at high temperatures. At high temperatures, the structure of unmodified tRNA will be disrupted. Therefore, thermophiles must possess strategies to stabilize tRNA structures. To this end, several thermophile-specific modified nucleosides in tRNA have been identified. Other factors such as RNA-binding proteins and polyamines contribute to the stability of tRNA at high temperatures. Thermus thermophilus, which is an extreme-thermophilic eubacterium, can adapt its protein synthesis system in response to temperature changes via the network of modified nucleosides in tRNA and tRNA modification enzymes. Notably, tRNA modification enzymes from thermophiles are very stable. Therefore, they have been utilized for biochemical and structural studies. In the future, thermostable tRNA modification enzymes may be useful as biotechnology tools and may be utilized for medical science.
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Affiliation(s)
- Hiroyuki Hori
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
| | - Takuya Kawamura
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
| | - Takako Awai
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
| | - Anna Ochi
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
| | - Ryota Yamagami
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
| | - Chie Tomikawa
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
| | - Akira Hirata
- Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
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18
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Said EA, Tremblay N, Al-Balushi MS, Al-Jabri AA, Lamarre D. Viruses Seen by Our Cells: The Role of Viral RNA Sensors. J Immunol Res 2018; 2018:9480497. [PMID: 29854853 PMCID: PMC5952511 DOI: 10.1155/2018/9480497] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 02/20/2018] [Accepted: 03/13/2018] [Indexed: 12/12/2022] Open
Abstract
The role of the innate immune response in detecting RNA viruses is crucial for the establishment of proper inflammatory and antiviral responses. Different receptors, known as pattern recognition receptors (PRRs), are present in the cytoplasm, endosomes, and on the cellular surface. These receptors have the capacity to sense the presence of viral nucleic acids as pathogen-associated molecular patterns (PAMPs). This recognition leads to the induction of type 1 interferons (IFNs) as well as inflammatory cytokines and chemokines. In this review, we provide an overview of the significant involvement of cellular RNA helicases and Toll-like receptors (TLRs) 3, 7, and 8 in antiviral immune defenses.
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Affiliation(s)
- Elias A. Said
- Department of Microbiology and Immunology, College of Medicine and Health Sciences, Sultan Qaboos University, P.O. Box 35, 123 Muscat, Oman
| | - Nicolas Tremblay
- Centre de Recherche du CHUM (CRCHUM) et Faculté de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Mohammed S. Al-Balushi
- Department of Microbiology and Immunology, College of Medicine and Health Sciences, Sultan Qaboos University, P.O. Box 35, 123 Muscat, Oman
| | - Ali A. Al-Jabri
- Department of Microbiology and Immunology, College of Medicine and Health Sciences, Sultan Qaboos University, P.O. Box 35, 123 Muscat, Oman
| | - Daniel Lamarre
- Centre de Recherche du CHUM (CRCHUM) et Faculté de Médecine, Université de Montréal, Montréal, QC, Canada
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19
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Abstract
Pattern recognition receptors (PRRs) survey intra- and extracellular spaces for pathogen-associated molecular patterns (PAMPs) within microbial products of infection. Recognition and binding to cognate PAMP ligand by specific PRRs initiates signaling cascades that culminate in a coordinated intracellular innate immune response designed to control infection. In particular, our immune system has evolved specialized PRRs to discriminate viral nucleic acid from host. These are critical sensors of viral RNA to trigger innate immunity in the vertebrate host. Different families of PRRs of virus infection have been defined and reveal a diversity of PAMP specificity for wide viral pathogen coverage to recognize and extinguish virus infection. In this review, we discuss recent insights in pathogen recognition by the RIG-I-like receptors, related RNA helicases, Toll-like receptors, and other RNA sensor PRRs, to present emerging themes in innate immune signaling during virus infection.
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Affiliation(s)
- Kwan T Chow
- Center for Innate Immunity and Immune Disease and Department of Immunology, University of Washington, Seattle, Washington 98109, USA; , ,
| | - Michael Gale
- Center for Innate Immunity and Immune Disease and Department of Immunology, University of Washington, Seattle, Washington 98109, USA; , ,
| | - Yueh-Ming Loo
- Center for Innate Immunity and Immune Disease and Department of Immunology, University of Washington, Seattle, Washington 98109, USA; , ,
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20
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TLR8 activation and inhibition by guanosine analogs in RNA: Importance of functional groups and chain length. Bioorg Med Chem 2017; 26:77-83. [PMID: 29174509 DOI: 10.1016/j.bmc.2017.11.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 11/02/2017] [Accepted: 11/11/2017] [Indexed: 11/23/2022]
Abstract
Toll-like receptor 8 (TLR8) is an important component of the human innate immune system that recognizes single stranded RNA (ssRNA). Recent X-ray crystal structures of TLR8 bound to ssRNA revealed a previously unrecognized binding site for a 5'-UpG-3' dinucleotide. Here we use an atomic mutagenesis strategy coupled with a cellular TLR8 activation assay to probe the importance of specific functional groups present on the guanine base in RNA-mediated receptor agonism and antagonism. Results from RNA analogs containing 7-deazaguanosine, 2-aminopurine and inosine confirm the importance of guanine N7, O6 and N2, respectively, in TLR8 activation. Nevertheless, these RNAs each retained TLR8 antagonism activity. RNA containing 7-deaza-8-azainosine (7d8aI) was prepared from a novel phosphoramidite and found to be a weaker TLR8 activator than guanosine-containing RNA. However, 7d8aI-containing RNA also retained TLR8 antagonism activity indicating that removal of multiple TLR8 H-bonding sites on guanine is insufficient for blocking TLR8 antagonism by guanine-containing RNA. We also identified an oligoribonucleotide length dependence on both TLR8 activation and antagonism. These studies extend our understanding of the effects of nucleobase modification on immune stimulation and will inform the design of novel RNA-based therapeutics.
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