Influenza A virus (IAV) infection regulates the expression of numerous host genes. However, the precise mechanism underlying implication of these genes in IAV pathogenesis remains largely unknown. Here, we employed isobaric tags for relative and absolute quantification (iTRAQ) to identify host proteins regulated by IAV infection. iTRAQ analysis of mouse lungs infected or uninfected with IAV showed a total of 167 differentially upregulated proteins in response to the viral infection. Interestingly, we observed that p27Kip1, a potent cyclin‐dependent kinase inhibitor, was markedly induced by IAV both at mRNA and protein levels through in vitro and in vivo studies. Furthermore, it was shown that innate immune signalling positively regulated p27Kip1 expression in response to IAV infection. Ectopic expression of p27Kip1 in A549 cells dramatically inhibited IAV replication, whereas, p27Kip1 knockdown significantly enhanced the virus replication. in vivo experiments demonstrated that p27Kip1 knockout (KO) mice were more susceptible to IAV than wild‐type (WT) mice: exhibiting higher viral load in lung tissue, faster body‐weight loss, reduced survival rate and more severe organ damage. Moreover, we found that p27Kip1 overexpression facilitated the degradation of viral NS1 protein, caused a dramatic STAT1 activation and promoted the expression of IFN‐β and several critical antiviral interferon‐stimulated genes (ISGs). Increased p27Kip1 expression also restricted infections of several other viruses. Conversely, IAV‐infected p27Kip1 KO mice exhibited a sharp increase in NS1 protein accumulation, reduced level of STAT1 activation and decreased expression of IFN‐β and the ISGs in the lung compared to WT animals. These findings reveal a key role of p27Kip1 in enhancing antiviral innate immunity.

中文翻译：

---

病毒感染诱导的 p27Kip1 的稳健表达对于抗病毒先天免疫至关重要。

甲型流感病毒 (IAV) 感染调节许多宿主基因的表达。然而，这些基因在 IAV 发病机制中的潜在影响的确切机制在很大程度上仍然未知。在这里，我们使用同量异位标记进行相对和绝对定量 (iTRAQ) 来识别受 IAV 感染调节的宿主蛋白。对感染或未感染 IAV 的小鼠肺部的 iTRAQ 分析显示，共有 167 种差异上调的蛋白质响应病毒感染。有趣的是，我们通过体外和体内研究观察到 p27Kip1，一种有效的细胞周期蛋白依赖性激酶抑制剂，在 mRNA 和蛋白质水平上均被 IAV 显着诱导。此外，研究表明先天免疫信号积极调节响应 IAV 感染的 p27Kip1 表达。p27Kip1 在 A549 细胞中的异位表达显着抑制了 IAV 复制，而 p27Kip1 敲低显着增强了病毒复制。体内实验表明，p27Kip1 敲除 (KO) 小鼠比野生型 (WT) 小鼠更容易感染 IAV：肺组织中的病毒载量更高，体重减轻更快，存活率降低，器官损伤更严重。此外，我们发现 p27Kip1 过表达促进了病毒 NS1 蛋白的降解，引起了显着的 STAT1 激活并促进了 IFN-β 和几个关键的抗病毒干扰素刺激基因 (ISG) 的表达。增加的 p27Kip1 表达也限制了其他几种病毒的感染。相反，IAV 感染的 p27Kip1 KO 小鼠表现出 NS1 蛋白积累的急剧增加，与 WT 动物相比，肺中 STAT1 激活水平降低和 IFN-β 和 ISG 表达降低。这些发现揭示了 p27Kip1 在增强抗病毒先天免疫中的关键作用。