Chen Wen Qin, Hu Yi Wei, Zou Peng Fei, Ren Shi Si, Nie Pin, Chang Ming Xian
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; Hubei Vocational College of Bio-Technology, Wuhan, Hubei Province 430070, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; Graduate University of Chinese Academy of Sciences, Beijing 100039, China.
Dev Comp Immunol. 2015 Mar;49(1):19-30. doi: 10.1016/j.dci.2014.10.017. Epub 2014 Nov 11.
The mitochondrial antiviral signaling protein (MAVS) plays a key role in the signal transduction of RIG-I-like receptors (RLRs)-mediated antiviral response. In the present study, zebrafish MAVS transcript variants, namely MAVS_tv1 and MAVS_tv2, were cloned from zebrafish embryos. The putative MAVS_tv1 protein (full length form) contains an N-terminal CARD domain, a central proline region, and a C-terminal transmembrane domain (TM). MAVS_tv2 is generated by a 190 bp intron fragment insertion. The putative MAVS_tv2 protein lacked TM domain due to a frame shift, with the N-terminal 303 aa residues identical to MAVS_tv1, and no sequence homology for the C-terminal 41 aa residues. Real-time PCR showed that the expression of MAVS_tv1 in ZF4 cells was higher than that of MAVS_tv2, and MAVS variants were induced by Edwardsiella tarda and SVCV infection during the early time points of infection, whereas MAVS_tv1 unchanged or MAVS_tv2 decreased at a later time point after the infection, respectively. Overexpression of MAVS_tv1 and MAVS_tv2 in fish cells conferred antiviral resistance, and activated zebrafish IFN1 and IFN3 promoters. MAVS_tv1 overexpression induced a slow (48 hpf) increased expression of IFN1, mxa, mxb, mxe and RSAD2. In contrast, MAVS_tv2 overexpression increased rapidly and transiently the expression of IFN1, IFN2, IFN3, mxc and rsad2 at 6 or 24 hpf. The simultaneous overexpression of MAVS variants and RIG-I in zebrafish embryos led to an accumulative induction of IFNs and IFN-stimulated genes including IFN1, IFN4, mxc, mxe and rsad. Furthermore, MAVS_tv1 cooperated with RIG-I in the accumulation of RIG-I transcript in a positive feedback loop; MAVS_tv2 synergized with MDA5 in the accumulation of MAVS_tv2 transcript. Collectively, these data suggest the molecular mechanisms of fish MAVS variants in antiviral immunity.
线粒体抗病毒信号蛋白（MAVS）在维甲酸诱导基因I样受体（RLRs）介导的抗病毒反应信号转导中起关键作用。在本研究中，从斑马鱼胚胎中克隆了斑马鱼MAVS转录变体，即MAVS_tv1和MAVS_tv2。推测的MAVS_tv1蛋白（全长形式）包含一个N端CARD结构域、一个中央脯氨酸区域和一个C端跨膜结构域（TM）。MAVS_tv2是由一个190bp内含子片段插入产生的。由于移码，推测的MAVS_tv2蛋白缺乏TM结构域，其N端303个氨基酸残基与MAVS_tv1相同，C端41个氨基酸残基无序列同源性。实时PCR显示，MAVS_tv1在ZF4细胞中的表达高于MAVS_tv2，并且在感染早期，迟缓爱德华氏菌和鲤春病毒血症病毒感染可诱导MAVS变体表达，而在感染后的后期时间点，MAVS_tv1不变或MAVS_tv2分别下降。MAVS_tv1和MAVS_tv2在鱼细胞中的过表达赋予了抗病毒抗性，并激活了斑马鱼IFN1和IFN3启动子。MAVS_tv1过表达诱导IFN1、mxa、mxb、mxe和RSAD2的表达在缓慢（48 hpf）时增加。相比之下，MAVS_tv2过表达在6或24 hpf时迅速且短暂地增加IFN1、IFN2、IFN3、mxc和rsad2的表达。MAVS变体和RIG-I在斑马鱼胚胎中的同时过表达导致IFN和IFN刺激基因（包括IFN1、IFN4、mxc、mxe和rsad）的累积诱导。此外，MAVS_tv1与RIG-I在RIG-I转录本的积累中以正反馈环的方式协同作用；MAVS_tv2与MDA5在MAVS_tv2转录本的积累中协同作用。总体而言，这些数据揭示了鱼类MAVS变体在抗病毒免疫中的分子机制。
