RESUMO
Double-stranded RNA-induced antiviral gene expression in mammalian cells requires activation of IFN regulatory factor 3 (IRF3). In this study, we show that the IL-17R adaptor protein Act1/CIKS is involved in this process. Small interfering RNA-mediated knockdown of Act1 in primary human skin fibroblasts specifically attenuates expression of IFN-ß and IFN-stimulated antiviral genes induced by a synthetic viral mimic, polyinosinic-polycytidylic acid. Ectopic expression of Act1 potentiates the IRF3-driven expression of a synthetic reporter construct as well as the induction of antiviral genes. We demonstrate that this effect is dependent on the ability of Act1 to functionally and physically interact with IκB kinase ε (IKKε), a known IRF3 kinase, and IRF3: 1) Act1 binds IKKε and IRF3; 2) Act1-induced IRF3 activation can be blocked specifically by coexpression of a catalytically inactive mutant of IKKε; and 3) mutants of IRF3, either lacking the C terminus or mutated at the key phosphorylation sites, important for its activation by IKKε, do not support Act1-dependent IRF3 activation. We also show that a zebrafish Act1 protein is able to trigger antiviral gene expression in human cells, which suggests an evolutionarily conserved function of vertebrate Act1 in the host defense against viruses. On the whole, our study demonstrates that Act1 is a component of antiviral signaling.
Assuntos
Fibroblastos/imunologia , Infecções por Vírus de RNA/imunologia , Vírus de RNA/imunologia , Transdução de Sinais/imunologia , Peptídeos e Proteínas Associados a Receptores de Fatores de Necrose Tumoral/imunologia , Proteínas Adaptadoras de Transdução de Sinal , Animais , Linhagem Celular Tumoral , Evolução Molecular , Fibroblastos/metabolismo , Fibroblastos/virologia , Humanos , Quinase I-kappa B/genética , Quinase I-kappa B/imunologia , Quinase I-kappa B/metabolismo , Fator Regulador 3 de Interferon/genética , Fator Regulador 3 de Interferon/imunologia , Fator Regulador 3 de Interferon/metabolismo , Interferon beta/genética , Interferon beta/imunologia , Interferon beta/metabolismo , Mutação , Infecções por Vírus de RNA/genética , Infecções por Vírus de RNA/metabolismo , Vírus de RNA/genética , Vírus de RNA/metabolismo , RNA Interferente Pequeno , Transdução de Sinais/genética , Peptídeos e Proteínas Associados a Receptores de Fatores de Necrose Tumoral/genética , Peptídeos e Proteínas Associados a Receptores de Fatores de Necrose Tumoral/metabolismo , Peixe-Zebra/genética , Peixe-Zebra/imunologia , Peixe-Zebra/virologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/imunologia , Proteínas de Peixe-Zebra/metabolismoRESUMO
Excessive inflammation during bacterial and viral infections is destructive to the host and involves elevated production of proinflammatory cytokines. It is especially deleterious in organs with space constraints such as lung and the CNS. Indeed, a number of viruses that infect lungs, such as avian influenza virus, SARS-associated coronavirus, and respiratory syncytial virus, elicit a very high level of proinflammatory cytokines; however, it is unclear what triggers their production. In this study, we show that IL-17 commonly produced during viral infection specifically augments a proinflammatory response by directly synergizing with antiviral signaling. Costimulation of primary human fibroblasts with IL-17 greatly enhanced respiratory syncytial virus-induced or synthetic dsRNA-based viral mimic polyinosinic:polycytidylic acid-induced expression of proinflammatory genes without affecting expression of IFN-ß-stimulated or IFN-stimulated genes. Knockdown of expression of known mediators of the antiviral signaling pathway revealed that the IL-17-poly(I:C) synergy depends on the presence of the transcriptional factors RelA and IFN regulatory factor 3 and IκB kinases. Moreover, this synergy was blocked by an IκB kinase inhibitor, BAY 11-7082. These findings shed light on the molecular mechanisms behind IL-17-dependent immunopathology observed in viral infections.
