scholarly journals RNase L amplifies Interferon signaling by inducing PKR-mediated antiviral stress granules

2020 ◽  
Author(s):  
Praveen Manivannan ◽  
Mohammad Adnan Siddiqui ◽  
Krishnamurthy Malathi
Keyword(s):  
Pattern Recognition ◽  
Virus Infection ◽  
Viral Infections ◽  
Stress Granules ◽  
Antiviral Response ◽  
Pattern Recognition Receptors ◽  
Stress Granule ◽  
Rna Cleavage ◽  
Rnase L ◽  
Rna Ligands

ABSTRACTVirus infection leads to activation of the interferon-induced endoribonuclease, RNase L, which results in degradation of viral and cellular RNAs. Both cellular and viral RNA cleavage products of RNase L bind pattern recognition receptors (PRR) like Retinoic acid-inducible I (Rig-I) and or melanoma differentiation-associated protein 5 (MDA5) to further amplify interferon (IFN) production and antiviral response. Although much is known about the mechanics of ligand binding and PRR activation, how the cells coordinate RNA sensing to signaling response and interferon production remains unclear. We show that RNA cleavage products of RNase L activity induce formation of antiviral stress granule (avSG) by regulating activation of double-stranded RNA (dsRNA)-dependent protein kinase R (PKR), and recruit antiviral proteins Rig-I, PKR, OAS and RNase L to avSG. Biochemical analysis of purified avSG showed interaction of key stress granule protein, G3BP1, with only PKR and Rig-I and not with OAS or RNase L. AvSG assembly during RNase L activation is required for IRF3-mediated IFN production and not IFN signaling or proinflammatory cytokine induction. Consequently, cells lacking avSG formation or RNase L signaling produced less IFN and showed higher susceptibility during Sendai virus infection demonstrating the importance of avSG in RNase L-mediated host defense. During viral infection, we propose a role for RNase L-cleaved RNAs in inducing avSG containing antiviral proteins to provide a platform for efficient interaction of RNA ligands with pattern recognition receptors to enhance IFN production to effectively mount antiviral response.IMPORTANCEDouble-stranded RNAs produced during viral infections serve as pathogen associated molecular patterns (PAMPs) and bind pattern recognition receptors to stimulate IFN production. RNase L is an IFN-regulated endoribonuclease that is activated in virus-infected cells and cleaves single-stranded viral and cellular RNAs. The RNase L-cleaved dsRNAs signal to Rig-like helicases to amplify IFN production. This study identifies a novel role of antiviral stress granules induced by RNase L as an antiviral signaling hub to coordinate the RNA ligands with cognate receptors to mount effective host response during viral infections.

scholarly journals RNase L Amplifies Interferon Signaling by Inducing Protein Kinase R-Mediated Antiviral Stress Granules

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
Praveen Manivannan ◽  
Mohammad Adnan Siddiqui ◽  
Krishnamurthy Malathi
Keyword(s):  
Pattern Recognition ◽  
Protein Kinase ◽  
Virus Infection ◽  
Viral Infections ◽  
Stress Granules ◽  
Pattern Recognition Receptors ◽  
Rna Cleavage ◽  
Rnase L ◽  
Protein Kinase R ◽  
Rna Ligands

ABSTRACT Virus infection leads to activation of the interferon (IFN)-induced endoribonuclease RNase L, which results in degradation of viral and cellular RNAs. Both cellular and viral RNA cleavage products of RNase L bind pattern recognition receptors (PRRs), like retinoic acid-inducible I (Rig-I) and melanoma differentiation-associated protein 5 (MDA5), to further amplify IFN production and antiviral response. Although much is known about the mechanics of ligand binding and PRR activation, how cells coordinate RNA sensing with signaling response and interferon production remains unclear. We show that RNA cleavage products of RNase L activity induce the formation of antiviral stress granules (avSGs) by regulating activation of double-stranded RNA (dsRNA)-dependent protein kinase R (PKR) and recruit the antiviral proteins Rig-I, PKR, OAS, and RNase L to avSGs. Biochemical analysis of purified avSGs showed interaction of a key stress granule protein, G3BP1, with only PKR and Rig-I and not with OAS or RNase L. AvSG assembly during RNase L activation is required for IRF3-mediated IFN production, but not IFN signaling or proinflammatory cytokine induction. Consequently, cells lacking avSG formation or RNase L signaling produced less IFN and showed higher susceptibility during Sendai virus infection, demonstrating the importance of avSGs in RNase L-mediated host defense. We propose a role during viral infection for RNase L-cleaved RNAs in inducing avSGs containing antiviral proteins to provide a platform for efficient interaction of RNA ligands with pattern recognition receptors to enhance IFN production to mount an effective antiviral response. IMPORTANCE Double-stranded RNAs produced during viral infections serve as pathogen-associated molecular patterns (PAMPs) and bind pattern recognition receptors to stimulate IFN production. RNase L is an IFN-regulated endoribonuclease that is activated in virus-infected cells and cleaves single-stranded viral and cellular RNAs. The RNase L-cleaved dsRNAs signal to Rig-like helicases to amplify IFN production. This study identifies a novel role of antiviral stress granules induced by RNase L as an antiviral signaling hub to coordinate the RNA ligands with cognate receptors to mount an effective host response during viral infections.

scholarly journals Stable Formation of Compositionally Unique Stress Granules in Virus-Infected Cells

2009 ◽  
Vol 84 (7) ◽  
pp. 3654-3665 ◽  
Author(s):  
Joanna Piotrowska ◽  
Spencer J. Hansen ◽  
Nogi Park ◽  
Katarzyna Jamka ◽  
Peter Sarnow ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Heat Shock ◽  
Viral Infections ◽  
De Novo ◽  
Stress Granules ◽  
Stress Granule ◽  
Initiation Factor ◽  
Granule Formation ◽  
Infected Cells ◽  
Positive Strand Rna

ABSTRACT Stress granules are sites of mRNA storage formed in response to a variety of stresses, including viral infections. Here, the mechanisms and consequences of stress granule formation during poliovirus infection were examined. The results indicate that stress granules containing T-cell-restricted intracellular antigen 1 (TIA-1) and mRNA are stably constituted in infected cells despite lacking intact RasGAP SH3-domain binding protein 1 (G3BP) and eukaryotic initiation factor 4G. Fluorescent in situ hybridization revealed that stress granules in infected cells do not contain significant amounts of viral positive-strand RNA. Infection does not prevent stress granule formation in response to heat shock, indicating that poliovirus does not block de novo stress granule formation. A mutant TIA-1 protein that prevents stress granule formation during oxidative stress also prevents formation in infected cells. However, stress granule formation during infection is more dependent upon ongoing transcription than is formation during oxidative stress or heat shock. Furthermore, Sam68 is recruited to stress granules in infected cells but not to stress granules formed in response to oxidative stress or heat shock. These results demonstrate that stress granule formation in poliovirus-infected cells utilizes a transcription-dependent pathway that results in the appearance of stable, compositionally unique stress granules.

scholarly journals Mitochondria, pattern recognition receptors and autophagy under physiological and pathological conditions, including viral infections

2021 ◽  
Author(s):  
Paulina Niedźwiedzka-Rystwej ◽  
Dominika Bębnowska ◽  
Roman Kołacz ◽  
Wiesław Deptuła
Keyword(s):  
Pattern Recognition ◽  
Viral Infections ◽  
Apoptotic Cell ◽  
Pattern Recognition Receptors ◽  
The Body ◽  
The Other ◽  
Cellular Processes ◽  
Pathological Conditions ◽  
Other Hand

Research on the health of mammals invariably shows how dynamic immunology is and how the role of many elements and immune processes of the macroorganism, developed in the process of evolution in protecting against threats, including infections, is changing. Among these elements conditioning the homeostasis of the macroorganism are mitochondria, PRR receptors (pattern recognition receptors) and the phenomenon of autophagy. In the context of physiological and pathological states in the body, mitochondria perform various functions. The primary function of these organelles is to produce energy in the cell, but on the other hand, they are heavily involved in various cellular processes, including ROS production and calcium homeostasis. They are largely involved in the activation of immune mechanisms during infectious and non-infectious conditions through mtDNA and the mitochondrial MAVS protein. Mitochondrial involvement has been also determined in PRR-related mechanisms as mtDNA has the ability to directly stimulate TLRs. On the other hand, mitochondria are also associated with apoptotic cell death and autophagy.

scholarly journals RNase L promotes the formation of unique ribonucleoprotein granules distinct from stress granules

2020 ◽  
Vol 295 (6) ◽  
pp. 1426-1438 ◽  
Author(s):  
James M. Burke ◽  
Evan T. Lester ◽  
Devin Tauber ◽  
Roy Parker
Keyword(s):  
Stress Granules ◽  
Antiviral Response ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Rnase L ◽  
Protein Kinase R ◽  
Eukaryotic Translation ◽  
P Bodies ◽  
Initiation Factor 2 ◽  
Rnp Complex

Stress granules (SGs) are ribonucleoprotein (RNP) assemblies that form in eukaryotic cells as a result of limited translation in response to stress. SGs form during viral infection and are thought to promote the antiviral response because many viruses encode inhibitors of SG assembly. However, the antiviral endoribonuclease RNase L also alters SG formation, whereby only small punctate SG-like bodies that we term RNase L–dependent bodies (RLBs) form during RNase L activation. How RLBs relate to SGs and their mode of biogenesis is unknown. Herein, using immunofluorescence, live-cell imaging, and MS-based analyses, we demonstrate that RLBs represent a unique RNP granule with a protein and RNA composition distinct from that of SGs in response to dsRNA lipofection in human cells. We found that RLBs are also generated independently of SGs and the canonical dsRNA-induced SG biogenesis pathway, because RLBs did not require protein kinase R, phosphorylation of eukaryotic translation initiation factor 2 subunit 1 (eIF2α), the SG assembly G3BP paralogs, or release of mRNAs from ribosomes via translation elongation. Unlike the transient interactions between SGs and P-bodies, RLBs and P-bodies extensively and stably interacted. However, despite both RLBs and P-bodies exhibiting liquid-like properties, they remained distinct condensates. Taken together, these observations reveal that RNase L promotes the formation of a unique RNP complex that may have roles during the RNase L–mediated antiviral response.

scholarly journals RIG-I Activation by a Designer Short RNA Ligand Protects Human Immune Cells against Dengue Virus Infection without Causing Cytotoxicity

2019 ◽  
Vol 93 (14) ◽  
Author(s):  
Victor Ho ◽  
Hui Yee Yong ◽  
Marion Chevrier ◽  
Vipin Narang ◽  
Josephine Lum ◽  
...  
Keyword(s):  
Virus Infection ◽  
Dengue Virus ◽  
Human Skin ◽  
Immune Cells ◽  
Viral Infections ◽  
Short Hairpin Rna ◽  
Dengue Virus Infection ◽  
Hairpin Rna ◽  
Short Hairpin ◽  
Rna Ligands

ABSTRACT Virus-derived double-stranded RNA (dsRNA) molecules containing a triphosphate group at the 5′ end are natural ligands of retinoic acid-inducible gene I (RIG-I). The cellular pathways and proteins induced by RIG-I are an essential part of the innate immune response against viral infections. Starting from a previously published RNA scaffold (3p10L), we characterized an optimized small dsRNA hairpin (called 3p10LG9, 25 nucleotides [nt] in length) as a highly efficient RIG-I activator. Dengue virus (DENV) infection in cell lines and primary human skin cells could be prevented and restricted through 3p10LG9-mediated activation of RIG‐I. This antiviral effect was RIG-I and interferon signal dependent. The effect was temporary and was reversed above a saturating concentration of RIG-I ligand. This finding revealed an effective feedback loop that controls potentially damaging inflammatory effects of the RIG-I response, at least in immune cells. Our results show that the small RIG-I activator 3p10LG9 can confer short-term protection against DENV and can be further explored as an antiviral treatment in humans. IMPORTANCE Short hairpin RNA ligands that activate RIG-I induce antiviral responses in infected cells and prevent or control viral infections. Here, we characterized a new short hairpin RNA molecule with high efficacy in antiviral gene activation and showed that this molecule is able to control dengue virus infection. We demonstrate how structural modifications of minimal RNA ligands can lead to increased potency and a wider window of RIG-I-activating concentrations before regulatory mechanisms kick in at high concentrations. We also show that minimal RNA ligands induce an effective antiviral response in human skin dendritic cells and macrophages, which are the target cells of initial infection after the mosquito releases virus into the skin. Using short hairpin RNA as RIG-I ligands could therefore be explored as antiviral therapy.

scholarly journals Why Females Do Better: The X Chromosomal TLR7 Gene-Dose Effect in COVID-19

2021 ◽  
Vol 12 ◽  
Author(s):  
Anna E. Spiering ◽  
Teun J. de Vries
Keyword(s):  
Pattern Recognition ◽  
Viral Infections ◽  
Pattern Recognition Receptors ◽  
Dose Effect ◽  
Toll Like Receptor ◽  
Novel Studies ◽  
Gene Dose ◽  
Male Sex ◽  
Tlr7 Stimulation

A male sex bias has emerged in the COVID-19 pandemic, fitting to the sex-biased pattern in other viral infections. Males are 2.84 times more often admitted to the ICU and mortality is 1.39 times higher as a result of COVID-19. Various factors play a role in this, and novel studies suggest that the gene-dose of Toll-Like Receptor (TLR) 7 could contribute to the sex-skewed severity. TLR7 is one of the crucial pattern recognition receptors for SARS-CoV-2 ssRNA and the gene-dose effect is caused by X chromosome inactivation (XCI) escape. Female immune cells with TLR7 XCI escape have biallelic TLR7 expression and produce more type 1 interferon (IFN) upon TLR7 stimulation. In COVID-19, TLR7 in plasmacytoid dendritic cells is one of the pattern recognition receptors responsible for IFN production and a delayed IFN response has been associated with immunopathogenesis and mortality. Here, we provide a hypothesis that females may be protected to some extend against severe COVID-19, due to the biallelic TLR7 expression, allowing them to mount a stronger and more protective IFN response early after infection. Studies exploring COVID-19 treatment via the TLR7-mediated IFN pathway should consider this sex difference. Various factors such as age, sex hormones and escape modulation remain to be investigated concerning the TLR7 gene-dose effect.

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