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Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5
BACKGROUND: The cytoplasmic RIG-like receptors are responsible for the early detection of viruses and other intracellular microbes by activating the innate immune response mediated by type I interferons (IFNs). RIG-I and MDA5 detect virus-specific RNA motifs with short 5′-tri/diphosphorylated, blunt...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2015
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517655/ https://www.ncbi.nlm.nih.gov/pubmed/26215161 http://dx.doi.org/10.1186/s12915-015-0166-9 |
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author | Louber, Jade Brunel, Joanna Uchikawa, Emiko Cusack, Stephen Gerlier, Denis |
author_facet | Louber, Jade Brunel, Joanna Uchikawa, Emiko Cusack, Stephen Gerlier, Denis |
author_sort | Louber, Jade |
collection | PubMed |
description | BACKGROUND: The cytoplasmic RIG-like receptors are responsible for the early detection of viruses and other intracellular microbes by activating the innate immune response mediated by type I interferons (IFNs). RIG-I and MDA5 detect virus-specific RNA motifs with short 5′-tri/diphosphorylated, blunt-end double-stranded RNA (dsRNA) and >0.5–2 kb long dsRNA as canonical agonists, respectively. However, in vitro, they can bind to many RNA species, while in cells there is an activation threshold. As SF2 helicase/ATPase family members, ATP hydrolysis is dependent on co-operative RNA and ATP binding. Whereas simultaneous ATP and cognate RNA binding is sufficient to activate RIG-I by releasing autoinhibition of the signaling domains, the physiological role of the ATPase activity of RIG-I and MDA5 remains controversial. RESULTS: A cross-analysis of a rationally designed panel of RNA binding and ATPase mutants and truncated receptors, using type I IFN promoter activation as readout, allows us to refine our understanding of the structure-function relationships of RIG-I and MDA5. RNA activation of RIG-I depends on multiple critical RNA binding sites in its helicase domain as confirmed by functional evidence using novel mutations. We found that RIG-I or MDA5 mutants with low ATP hydrolysis activity exhibit constitutive activity but this was fully reverted when associated with mutations preventing RNA binding to the helicase domain. We propose that the turnover kinetics of the ATPase domain enables the discrimination of self/non-self RNA by both RIG-I and MDA5. Non-cognate, possibly self, RNA binding would lead to fast ATP turnover and RNA disassociation and thus insufficient time for the caspase activation and recruitment domains (CARDs) to promote downstream signaling, whereas tighter cognate RNA binding provides a longer time window for downstream events to be engaged. CONCLUSIONS: The exquisite fine-tuning of RIG-I and MDA5 RNA-dependent ATPase activity coupled to CARD release allows a robust IFN response from a minor subset of non-self RNAs within a sea of cellular self RNAs. This avoids the eventuality of deleterious autoimmunity effects as have been recently described to arise from natural gain-of-function alleles of RIG-I and MDA5. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12915-015-0166-9) contains supplementary material, which is available to authorized users. |
format | Online Article Text |
id | pubmed-4517655 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-45176552015-07-29 Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 Louber, Jade Brunel, Joanna Uchikawa, Emiko Cusack, Stephen Gerlier, Denis BMC Biol Research Article BACKGROUND: The cytoplasmic RIG-like receptors are responsible for the early detection of viruses and other intracellular microbes by activating the innate immune response mediated by type I interferons (IFNs). RIG-I and MDA5 detect virus-specific RNA motifs with short 5′-tri/diphosphorylated, blunt-end double-stranded RNA (dsRNA) and >0.5–2 kb long dsRNA as canonical agonists, respectively. However, in vitro, they can bind to many RNA species, while in cells there is an activation threshold. As SF2 helicase/ATPase family members, ATP hydrolysis is dependent on co-operative RNA and ATP binding. Whereas simultaneous ATP and cognate RNA binding is sufficient to activate RIG-I by releasing autoinhibition of the signaling domains, the physiological role of the ATPase activity of RIG-I and MDA5 remains controversial. RESULTS: A cross-analysis of a rationally designed panel of RNA binding and ATPase mutants and truncated receptors, using type I IFN promoter activation as readout, allows us to refine our understanding of the structure-function relationships of RIG-I and MDA5. RNA activation of RIG-I depends on multiple critical RNA binding sites in its helicase domain as confirmed by functional evidence using novel mutations. We found that RIG-I or MDA5 mutants with low ATP hydrolysis activity exhibit constitutive activity but this was fully reverted when associated with mutations preventing RNA binding to the helicase domain. We propose that the turnover kinetics of the ATPase domain enables the discrimination of self/non-self RNA by both RIG-I and MDA5. Non-cognate, possibly self, RNA binding would lead to fast ATP turnover and RNA disassociation and thus insufficient time for the caspase activation and recruitment domains (CARDs) to promote downstream signaling, whereas tighter cognate RNA binding provides a longer time window for downstream events to be engaged. CONCLUSIONS: The exquisite fine-tuning of RIG-I and MDA5 RNA-dependent ATPase activity coupled to CARD release allows a robust IFN response from a minor subset of non-self RNAs within a sea of cellular self RNAs. This avoids the eventuality of deleterious autoimmunity effects as have been recently described to arise from natural gain-of-function alleles of RIG-I and MDA5. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12915-015-0166-9) contains supplementary material, which is available to authorized users. BioMed Central 2015-07-28 /pmc/articles/PMC4517655/ /pubmed/26215161 http://dx.doi.org/10.1186/s12915-015-0166-9 Text en © Louber et al. 2015 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
spellingShingle | Research Article Louber, Jade Brunel, Joanna Uchikawa, Emiko Cusack, Stephen Gerlier, Denis Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 |
title | Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 |
title_full | Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 |
title_fullStr | Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 |
title_full_unstemmed | Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 |
title_short | Kinetic discrimination of self/non-self RNA by the ATPase activity of RIG-I and MDA5 |
title_sort | kinetic discrimination of self/non-self rna by the atpase activity of rig-i and mda5 |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517655/ https://www.ncbi.nlm.nih.gov/pubmed/26215161 http://dx.doi.org/10.1186/s12915-015-0166-9 |
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