Zhang Rui, Xu Aotian, Qin Chao, Zhang Qiong, Chen Shifan, Lang Yue, Wang Mengdong, Li Chuang, Feng Wenhai, Zhang Rui, Jiang Zhengfan, Tang Jun
State Key Laboratory of Agrobiotechnology and College of Veterinary Medicine, China Agricultural University, Beijing, China.
Department of Microbiology and Immunology, College of Biological Sciences, China Agricultural University, Beijing, China.
J Virol. 2017 Oct 13;91(21). doi: 10.1128/JVI.01148-17. Print 2017 Nov 1.
Alphaherpesviruses that establish persistent infections rely partly on their ability to evade host antiviral responses, notably the type I interferon (IFN) response. However, the mechanisms employed by alphaherpesviruses to avoid this response are not well understood. Pseudorabies virus (PRV) is an economically important pathogen and a useful model system for studying alphaherpesvirus biology. To identify PRV proteins that antagonize type I IFN signaling, we performed a screen by using an IFN-stimulated response element reporter in the swine cell line CRL. Unexpectedly, we identified the dUTPase UL50 as a strong inhibitor. We confirmed that UL50 has the ability to inhibit type I IFN signaling by performing ectopic expression of UL50 in cells and deletion of UL50 in PRV. Mechanistically, UL50 impeded type I IFN-induced STAT1 phosphorylation, likely by accelerating lysosomal degradation of IFN receptor 1 (IFNAR1). In addition, this UL50 activity was independent of its dUTPase activity and required amino acids 225 to 253 in the C-terminal region. The UL50 encoded by herpes simplex virus 1 (HSV-1) also possessed similar activity. Moreover, UL50-deleted PRV was more susceptible to IFN than UL50-proficient PRV. Our results suggest that in addition to its dUTPase activity, the UL50 protein of alphaherpesviruses possesses the ability to suppress type I IFN signaling by promoting lysosomal degradation of IFNAR1, thereby contributing to immune evasion. This finding reveals UL50 as a potential antiviral target. Alphaherpesviruses can establish lifelong infections and cause many diseases in humans and animals. Pseudorabies virus (PRV) is a swine alphaherpesvirus that threatens pig production. Using PRV as a model, we found that this alphaherpesvirus could utilize its encoded dUTPase UL50 to induce IFNAR1 degradation and inhibit type I IFN signaling in an enzymatic activity-independent manner. Our finding reveals a mechanism employed by an alphaherpesvirus to evade the immune response and indicates that UL50 is an important viral protein in pathogenesis and is a potential target for antiviral drug development.
建立持续性感染的甲型疱疹病毒部分依赖于其逃避宿主抗病毒反应的能力，尤其是I型干扰素（IFN）反应。然而，甲型疱疹病毒用于规避这种反应的机制尚不清楚。伪狂犬病病毒（PRV）是一种具有经济重要性的病原体，也是研究甲型疱疹病毒生物学的有用模型系统。为了鉴定拮抗I型IFN信号传导的PRV蛋白，我们在猪细胞系CRL中使用IFN刺激反应元件报告基因进行了筛选。出乎意料的是，我们鉴定出dUTPase UL50是一种强效抑制剂。我们通过在细胞中进行UL50的异位表达以及在PRV中缺失UL50，证实了UL50具有抑制I型IFN信号传导的能力。从机制上讲，UL50可能通过加速I型IFN诱导的STAT1磷酸化，可能是通过加速干扰素受体1（IFNAR1）的溶酶体降解。此外，这种UL50活性与其dUTPase活性无关，并且需要C末端区域的225至253位氨基酸。单纯疱疹病毒1（HSV-1）编码的UL50也具有类似的活性。此外，缺失UL50的PRV比具有UL50的PRV对IFN更敏感。我们的结果表明，除了其dUTPase活性外，甲型疱疹病毒的UL50蛋白还具有通过促进IFNAR1的溶酶体降解来抑制I型IFN信号传导的能力，从而有助于免疫逃避。这一发现揭示了UL50作为潜在的抗病毒靶点。甲型疱疹病毒可建立终身感染并在人类和动物中引起多种疾病。伪狂犬病病毒（PRV）是一种威胁生猪生产的猪甲型疱疹病毒。以PRV为模型，我们发现这种甲型疱疹病毒可以利用其编码的dUTPase UL50以酶活性非依赖的方式诱导IFNAR1降解并抑制I型IFN信号传导。我们的发现揭示了甲型疱疹病毒逃避免疫反应的一种机制，并表明UL50是发病机制中的一种重要病毒蛋白，是抗病毒药物开发的潜在靶点。
