Sustained Activation of Interferon Regulatory Factor 3 during Infection by Paramyxoviruses Requires MDA5

• Published in: Journal of innate immunity Vol. 6; no. 5; pp. 650 - 662
• Main Authors: Grandvaux, Nathalie, Guan, Xiaochun, Yoboua, Fabrice, Zucchini, Nicolas, Fink, Karin, Doyon, Priscilla, Martin, Lydie, Servant, Marc J., Chartier, Stéfany
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland S. Karger AG 01.01.2014
• Subjects: Cell Line; DEAD Box Protein 58; DEAD-box RNA Helicases - genetics; DEAD-box RNA Helicases - metabolism; Epithelial Cells - immunology; Epithelial Cells - virology; Gene Expression Regulation - genetics; Humans; Immunity, Innate - genetics; Interferon Regulatory Factor-3 - genetics; Interferon Regulatory Factor-3 - metabolism; Interferon-Induced Helicase, IFIH1; Phosphorylation - genetics; Proteolysis; Receptors, Immunologic; Research Article; Respiratory syncytial virus; Respiratory Syncytial Virus Infections - immunology; Respiratory Syncytial Virus, Human - immunology; RNA, Small Interfering - genetics; Sendai virus; Signal Transduction - genetics; Ubiquitination - genetics; Host defense; Respiratory syncytial virus; Interferon regulatory factor 3; Innate immunity; Pathogen recognition receptors; Melanoma differentiation-associated gene 5; Retinoic acid-inducible gene I
• ISSN: 1662-811X; 1662-8128; 1662-8128
• DOI: 10.1159/000360764

Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are the main cytosolic sensors of single-stranded RNA viruses, including paramyxoviruses, and are required to initiate a quick and robust innate antiviral response. Despite different ligand-binding properties, the consensus view is that RIG-I and MDA5 trigger common signal(s) to activate interferon regulatory factor 3 (IRF-3) and NF-κB, and downstream antiviral and proinflammatory cytokine expression. Here, we performed a thorough analysis of the temporal involvement of RIG-I and MDA5 in the regulation of IRF-3 during respiratory syncytial virus (RSV) infection. Based on specific RNA interference-mediated knockdown of RIG-I and MDA5 in A549 cells, we confirmed that RIG-I is critical for the initiation of IRF-3 phosphorylation, dimerization and downstream gene expression. On the other hand, our experiments yielded the first evidence that knockdown of MDA5 leads to early ubiquitination and proteasomal degradation of active IRF-3. Conversely, ectopic expression of MDA5 prolonged RIG-I-induced IRF-3 activation. Altogether, we provide novel mechanistic insight into the temporal involvement of RIG-I and MDA5 in the innate antiviral response. While RIG-I is essential for initial IRF-3 activation, engagement of induced MDA5 is essential to prevent early degradation of IRF-3, thereby sustaining IRF-3-dependent antiviral gene expression. MDA5 plays a similar role during Sendai virus infection suggesting that this model is not restricted to RSV amongst paramyxoviruses.