Structural and biochemical studies of RIG-I antiviral signaling
Structural and biochemical studies of RIG-I antiviral signaling
复制标题
RIG-I 抗病毒信号的结构和生化研究
DOI：
10.1007/s13238-012-2088-4
复制
发表时间：
2013-02-01
期刊：
影响因子：
21.1
通讯作者：
Zhou, Zhaocai
中科院分区：
文献类型：
--
作者：
Feng, Miao;Ding, Zhanyu;Zhou, Zhaocai
视黄酸诱导基因I（RIG-I）是一种重要的模式识别受体，其检测病毒RNA并通过下游接头MAVS（也称为IPS-1、CARDIF或VISA）触发I型干扰素的产生。一系列的结构研究已经阐明了dsRNA识别和激活RIG-I的一些机制。最近的研究提出，K63连接的泛素化或未锚定的K63连接的多聚泛素结合RIG-I正调控MAVS介导的抗病毒信号传导。相反，RIG-I的磷酸化似乎在控制RIG-I抗病毒信号转导中起抑制作用。在这里，我们进行了结构和生物化学相结合的研究，以进一步确定RIG-I信号转导的调控功能。ATP和双链RNA的结合引发了RIG-I的二聚化，并导致串联CARD结构域的构象重排。全长RIG-I似乎与dsRNA以2：2的摩尔比形成复合物。与先前报道的RIG-I在非活性状态下的晶体结构相比，我们的全长RIG-I与钝端dsRNA复合的电子显微镜结构首次揭示了CARD结构域的暴露的活性构象。此外，我们发现纯化的重组RIG-I蛋白可以独立于dsRNA结合MAVS的CARD结构域，而RIG-I的S8 E和T170 E磷酸化模拟突变体在结合E3连接酶TRIM 25、未锚定的K63连接的多聚泛素和MAVS方面有缺陷，而不管dsRNA如何。这些发现表明，RIG的磷酸化通过损害RIG-I与多聚泛素的结合及其与MAVS的相互作用来抑制下游信号传导。
Retinoic acid-inducible gene I (RIG-I) is an important pattern recognition receptor that detects viral RNA and triggers the production of type-I interferons through the downstream adaptor MAVS (also called IPS-1, CARDIF, or VISA). A series of structural studies have elaborated some of the mechanisms of dsRNA recognition and activation of RIG-I. Recent studies have proposed that K63-linked ubiquitination of, or unanchored K63-linked polyubiquitin binding to RIG-I positively regulates MAVS-mediated antiviral signaling. Conversely phosphorylation of RIG-I appears to play an inhibitory role in controlling RIG-I antiviral signal transduction. Here we performed a combined structural and biochemical study to further define the regulatory features of RIG-I signaling. ATP and dsRNA binding triggered dimerization of RIG-I with conformational rearrangements of the tandem CARD domains. Full length RIG-I appeared to form a complex with dsRNA in a 2:2 molar ratio. Compared with the previously reported crystal structures of RIG-I in inactive state, our electron microscopic structure of full length RIG-I in complex with blunt-ended dsRNA, for the first time, revealed an exposed active conformation of the CARD domains. Moreover, we found that purified recombinant RIG-I proteins could bind to the CARD domain of MAVS independently of dsRNA, while S8E and T170E phosphorylation-mimicking mutants of RIG-I were defective in binding E3 ligase TRIM25, unanchored K63-linked polyubiquitin, and MAVS regardless of dsRNA. These findings suggested that phosphorylation of RIG inhibited downstream signaling by impairing RIG-I binding with polyubiquitin and its interaction with MAVS.