Department of Biology, Colgate University, Hamilton, New York, USA.
J Virol. 2012 Feb;86(3):1650-60. doi: 10.1128/JVI.05924-11. Epub 2011 Nov 16.
A variety of signal transduction pathways are activated in response to viral infection, which dampen viral replication and transmission. These mechanisms involve both the induction of type I interferons (IFNs), which evoke an antiviral state, and the triggering of apoptosis. Mammalian orthoreoviruses are double-stranded RNA viruses that elicit apoptosis in vitro and in vivo. The transcription factors interferon regulatory factor 3 (IRF-3) and nuclear factor kappa light-chain enhancer of activated B cells (NF-κB) are required for the expression of IFN-β and the efficient induction of apoptosis in reovirus-infected cells. However, it is not known whether IFN-β induction is required for apoptosis, nor have the genes induced by IRF-3 and NF-κB that are responsible for apoptosis been identified. To determine whether IFN-β is required for reovirus-induced apoptosis, we used type I IFN receptor-deficient cells, IFN-specific antibodies, and recombinant IFN-β. We found that IFN synthesis and signaling are dispensable for the apoptosis of reovirus-infected cells. These results indicate that the apoptotic response following reovirus infection is mediated directly by genes responsive to IRF-3 and NF-κB. Noxa is a proapoptotic BH3-domain-only protein of the Bcl-2 family that requires IRF-3 and NF-κB for efficient expression. We found that Noxa is strongly induced at late times (36 to 48 h) following reovirus infection in a manner dependent on IRF-3 and NF-κB. The level of apoptosis induced by reovirus is significantly diminished in cells lacking Noxa, indicating a key prodeath function for this molecule during reovirus infection. These results suggest that prolonged innate immune response signaling induces apoptosis by eliciting Noxa expression in reovirus-infected cells.
多种信号转导途径被激活以响应病毒感染，从而抑制病毒复制和传播。这些机制既包括诱导 I 型干扰素（IFN），从而引发抗病毒状态，也包括触发细胞凋亡。哺乳动物正呼肠孤病毒是双链 RNA 病毒，可在体外和体内引发细胞凋亡。转录因子干扰素调节因子 3（IRF-3）和核因子κ轻链增强子的激活 B 细胞（NF-κB）对于 IFN-β的表达和在呼肠孤病毒感染细胞中有效诱导细胞凋亡是必需的。然而，尚不清楚 IFN-β诱导是否是细胞凋亡所必需的，也不知道负责细胞凋亡的由 IRF-3 和 NF-κB 诱导的基因。为了确定 IFN-β是否是呼肠孤病毒诱导细胞凋亡所必需的，我们使用了 I 型 IFN 受体缺陷细胞、IFN 特异性抗体和重组 IFN-β。我们发现呼肠孤病毒感染细胞的凋亡不需要 IFN 合成和信号转导。这些结果表明，呼肠孤病毒感染后细胞凋亡的反应是由直接响应 IRF-3 和 NF-κB 的基因介导的。Noxa 是 Bcl-2 家族中的一种促凋亡 BH3 结构域仅蛋白，需要 IRF-3 和 NF-κB 才能有效地表达。我们发现 Noxa 在呼肠孤病毒感染后晚期（36 至 48 小时）强烈诱导，其方式依赖于 IRF-3 和 NF-κB。在缺乏 Noxa 的细胞中，呼肠孤病毒诱导的细胞凋亡水平显著降低，表明该分子在呼肠孤病毒感染期间具有关键的促死亡功能。这些结果表明，延长的先天免疫反应信号通过在呼肠孤病毒感染的细胞中诱导 Noxa 表达来诱导细胞凋亡。
