title: Role of retinoic acid inducible gene-I in human metapneumovirus-induced cellular signalling.
abstract: Human metapneumovirus (HMPV) is a recently discovered pathogen that causes a significant proportion of respiratory infections in young infants, the elderly and immunocompromised patients. Very little is known regarding the cellular signalling elicited by this virus in airway epithelial cells, the target of HMPV infection. In this study, we investigated the role of the RNA helicases retinoic acid inducible gene-I (RIG-I) and melanoma differentiation-associated gene-5 (MDA-5) as the main pattern recognition receptors (PRRs) involved in viral detection and subsequent expression of proinflammatory and antiviral genes. HMPV infection readily induced RIG-I and MDA-5 gene and protein expression in A549 cells, a type II-like alveolar epithelial cell line. Expression of dominant-negative (DN) RIG-I or downregulation of RIG-I gene expression using small interfering RNA (siRNA) significantly decreased HMPV-induced beta interferon (IFN-beta), interleukin (IL)-8 and RANTES gene transcription, by inhibiting viral-induced activation of nuclear factor (NF)-kappaB and interferon regulatory factor (IRF), leading to enhanced viral replication. On the other hand, MDA-5 did not seem to play a significant role in HMPV-induced cellular responses. Mitochondrial antiviral signalling protein (MAVS), an adaptor protein linking both RIG-I and MDA-5 to downstream activation of IRF-3 and NF-kappaB, was also necessary for HMPV-induced cellular signalling. Expression of a DN MAVS significantly reduced IFN-beta and chemokine gene transcription, by inhibiting NF-kappaB- and IRF-dependent gene transcription, in response to HMPV infection. Our results show that HMPV activates the RIG-I-MAVS signalling pathway in airway epithelial cells, leading to the expression of important proinflammatory and antiviral molecules involved in the innate immune response to viruses.
authors.affiliation: Department of Pediatrics, Chang Gung Children's Hospital and Chang Gung University, Taoyuan, Taiwan, ROC.|Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: S
authors.initials: S
authors.lastname: Liao
authors.affiliation: Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: X
authors.initials: X
authors.lastname: Bao
authors.affiliation: Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: T
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Pediatrics, Chang Gung Children's Hospital and Chang Gung University, Taoyuan, Taiwan, ROC.|Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: S
authors.initials: S
authors.lastname: Lai
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: K
authors.initials: K
authors.lastname: Li
authors.affiliation: Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX, USA.|Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA.|Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Garofalo
authors.affiliation: Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX, USA.|Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA.|Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: A
authors.initials: A
authors.lastname: Casola
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000821:virology*; D005786:Gene Expression Regulation; D006801:Humans; D000072640:Interferon-Induced Helicase, IFIH1; D029121:Metapneumovirus / Q000472:pathogenicity*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism / Q000821:virology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014709:Vero Cells
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C505371:MAVS protein, human; C437968:PLAAT4 protein, human; D011506:Proteins; D034741:RNA, Small Interfering; D018168:Receptors, Retinoic Acid; C452815:IFIH1 protein, human; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1