Impact of the interferon regulated proteins XAF1 and ZNF313 on innate immunity

描述(申请人提供)：为了控制病毒感染，宿主发展了一个包括先天免疫反应和获得性免疫反应的综合防御网络。对病毒感染的初始反应主要包括先天反应和对具有细胞毒性的受感染细胞的杀伤。一旦病毒入侵细胞，宿主介导的反应由单链和双链病毒RNA触发，诱导包括干扰素(IFN)在内的应激细胞因子的表达。干扰素对启动和协调成功的抗病毒反应至关重要，它通过诱导一些细胞内基因，即干扰素刺激基因(ISGs)，防止病毒复制/细胞溶解，并刺激免疫系统的适应性臂。防止病毒复制、传播或持续感染的细胞机制包括全球抑制蛋白质合成、阻断蛋白质运输和诱导细胞凋亡。许多细胞蛋白被认为是病毒诱导的细胞凋亡的媒介，包括我们最初提出的两个蛋白，TRAIL/Apo-2L和X-连锁的凋亡相关因子抑制因子-1(XAF1)。IFN还通过上调病毒检测系统的组件，包括Toll样受体、RIG-I和下游信号分子，有效地调节细胞对病毒和其他细胞病原体的反应。最近，我们发现XAF1增强了细胞对TRAIL等凋亡剂的敏感性，并能增强细胞的抗病毒反应。XAF1在这里显示了影响由肿瘤坏死因子家族配体启动的信号级联和dsRNA信号级联。这项授权旨在从功能上剖析XAF1活动的机制。重点将放在XAF1活性的下游调节因子上，包括一种新发现的蛋白质ZNF313，我们现在证明它是一种XAF1结合的环指蛋白，受IFN翻译后调控。这种假定的E3泛素连接酶在调节干扰素、病毒和其他先天免疫反应中的作用将在以下目标中进行研究。我们还将继续追踪最近将XAF1与调节泛素连接的其他信号分子(包括TRAF2和RIP2)联系起来的数据，并证明另一个XAF1结合伙伴TRIP6可能代表着肿瘤坏死因子/dsRNA途径中的一种新的泛素化调节因子。

DESCRIPTION (provided by applicant): To control viral infections the host has developed an integrated defense network that comprises both innate and adaptive immune responses. Initial responses to viral infection involve primarily the innate response and the killing of infected cells with cytotoxicity. Once the virus has invaded the cell, host-mediated responses are triggered by single stranded and doubled stranded viral RNAs that induce expression of stress cytokines including interferons (IFNs). IFNs are essential for initiating and coordinating a successful antiviral response by inducing a number of intracellular genes, the IFN-stimulated genes (ISGs), which prevent virus replication/cytolysis and stimulate the adaptive arm of the immune system. Cellular mechanisms that prevent viral replication, dissemination or persistent infections include global inhibition of protein synthesis, blockage of protein transport and induction of apoptosis. A number of cellular proteins have been implicated as mediators of virus-induced apoptosis, including two of the proteins that were the focus of our original proposal, TRAIL/Apo-2L and X-linked inhibitor of apoptosis-associated factor-1 (XAF1). IFNs also potently regulate cellular responsiveness to virus and other cellular pathogens by upregulating components of the virus detection system, including toll-like receptors, RIG-I and downstream signaling molecules. Recently, we have shown that XAF1 augments cellular sensitivity to apoptotic agents such as TRAIL, and can also enhance cellular antiviral responses. XAF1 is shown herein to impact signaling cascades initiated by TNF family ligands and dsRNA signaling cascades. This grant is designed to functionally dissect the mechanism of XAF1 activity. Emphasis will be on downstream regulators of XAF1 activity, including a newly identified protein, ZNF313, which we now show to be a XAF1-binding RING finger protein that is post-translationally regulated by IFNs. The role of this putative E3 ubiquitin ligase in regulating IFN, viral and other innate immune responses will be pursued as outlined in the following aims. We will also pursue recent data linking XAF1 to other signaling molecules that regulate ubiquitin ligation, including TRAF2 and RIP2, and demonstrate that TRIP6, another XAF1 binding partner, may represent a novel ubiquitination regulator in the TNF/dsRNA pathway.