College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China.
Vet Res. 2014 Jun 18;45(1):66. doi: 10.1186/1297-9716-45-66.
Melanoma differentiation-associated gene 5 (MDA5) is an important intracellular receptor that recognizes long molecules of viral double-stranded RNA in innate immunity. To understand the mechanism of duck MDA5-mediated innate immunity, we cloned the MDA5 cDNA from the Muscovy duck (Cairina moschata). Quantitative real-time PCR analysis indicates that duck MDA5 mRNA was constitutively expressed in all sampled tissues. A significant increase of MDA5 mRNA was detected in the brain, spleen and lungs of ducks after infection with an H5N1 highly pathogenic avian influenza virus (HPAIV). We investigated the role of the predicted functional domains of MDA5. The results indicate the caspase activation and recruitment domain (CARD) of duck MDA5 had a signal transmission function through IRF-7-dependent signaling pathway. Overexpression of the CARD strongly activated the chicken IFN-β promoter and upregulated the mRNA expression of antiviral molecules (such as OAS, PKR and Mx), proinflammatory cytokines (such as IL-2, IL-6, IFN-α and IFN-γ, but not IL-1β and IL-8) and retinoic acid-inducible gene I (RIG-I)-like receptors (RLR) (RIG-I and LGP2) without exogenous stimulation. We also demonstrate the NS1 of the H5N1 HPAIV inhibited the duck MDA5-mediated signaling pathway in vitro. These results suggest that duck MDA5 is an important receptor for inducing antiviral activity in the host immune response of ducks.
黑色素瘤分化相关基因 5（MDA5）是先天免疫中识别病毒双链 RNA 的重要细胞内受体。为了了解鸭 MDA5 介导的先天免疫机制，我们从麝香鸭（Cairina moschata）中克隆了 MDA5 cDNA。定量实时 PCR 分析表明，鸭 MDA5 mRNA 在所有取样组织中均持续表达。感染 H5N1 高致病性禽流感病毒（HPAIV）后，鸭的大脑、脾脏和肺部中 MDA5 mRNA 显著增加。我们研究了 MDA5 预测功能域的作用。结果表明，鸭 MDA5 的半胱氨酸天冬氨酸蛋白酶激活和募集结构域（CARD）通过 IRF-7 依赖的信号通路具有信号转导功能。CARD 的过表达强烈激活鸡 IFN-β 启动子，并上调抗病毒分子（如 OAS、PKR 和 Mx）、促炎细胞因子（如 IL-2、IL-6、IFN-α 和 IFN-γ，但不包括 IL-1β 和 IL-8）和视黄酸诱导基因 I（RIG-I）样受体（RLR）（RIG-I 和 LGP2）的 mRNA 表达，而无需外源性刺激。我们还证明 H5N1 HPAIV 的 NS1 体外抑制了鸭 MDA5 介导的信号通路。这些结果表明，鸭 MDA5 是宿主免疫反应中诱导抗病毒活性的重要受体。
