Alphaviruses are enveloped, positive-sense RNA viruses that are important causes of viral encephalomyelitis. Sindbis virus (SINV) infects the neurons of rodents and is a model for studying factors that regulate infection of neuronal cells. The outcome of alphavirus infection of the central nervous system is dependent on neuronal maturation status. Differentiated mature neurons survive and control viral replication better than undifferentiated immature neurons. The cellular factors involved in age-dependent susceptibility include higher levels of antiapoptotic and innate immune factors in mature neurons. Because NF-κB pathway activation is required for the initiation of both apoptosis and the host antiviral response, we analyzed the role of NF-κB during SINV infection of differentiated and undifferentiated rat neuronal cells. SINV infection induced canonical NF-κB activation, as evidenced by the degradation of IκBα and the phosphorylation and nuclear translocation of p65. Inhibition or deletion of the upstream IκB kinase substantially reduced SINV replication in differentiated but not in undifferentiated neuronal cells or mouse embryo fibroblasts. NF-κB inhibition did not affect the establishment of infection, replication complex formation, the synthesis of nonstructural proteins, or viral RNA synthesis in differentiated neurons. However, the translation of structural proteins was impaired, phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α) was decreased, and host protein synthesis was maintained, suggesting that NF-κB activation was involved in the regulation of translation during infection of mature neurons. Inhibition or deletion of double-stranded RNA-activated protein kinase (PKR) also decreased eIF2α phosphorylation, the translation of viral structural proteins, and virus production. Therefore, canonical NF-κB activation synergizes with PKR to promote SINV replication in differentiated neurons by facilitating viral structural protein translation.IMPORTANCE Mosquito-borne alphaviruses are a significant and growing cause of viral encephalomyelitis worldwide. The outcome of alphaviral neuronal infections is host age dependent and greatly affected by neuronal maturation status, with differentiated, mature neurons being more resistant to infection than undifferentiated, immature neurons. The biological factors that change during neuronal maturation and that influence the outcome of viral infection are currently only partially defined. These studies investigated the role of NF-κB in determining the outcome of alphaviral infection in mature and immature neurons. Inhibition of canonical NF-κB activation decreased alphavirus replication in mature neurons by regulating protein synthesis and limiting the production of the viral structural proteins but had little effect on viral replication in immature neurons or fibroblasts. Therefore, NF-κB is a signaling pathway that influences the maturation-dependent outcome of alphaviral infection in neurons and that highlights the importance of cellular context in determining the effects of signal pathway activation.

中文翻译：

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NF-κB激活促进成熟神经元中的Alphavirus复制。

甲病毒是有包膜的正义RNA病毒，是病毒性脑脊髓炎的重要原因。Sindbis病毒（SINV）感染啮齿动物的神经元，是研究调节神经元细胞感染的因素的模型。α病毒感染中枢神经系统的结果取决于神经元成熟状态。分化的成熟神经元比未分化的未成熟神经元更好地存活并更好地控制病毒复制。年龄依赖性易感性所涉及的细胞因子包括成熟神经元中较高水平的抗凋亡和先天免疫因子。由于启动细胞凋亡和宿主抗病毒应答均需要激活NF-κB通路，因此我们分析了NF-κB在分化和未分化大鼠神经元细胞SINV感染过程中的作用。SINV感染诱导了典型的NF-κB活化，这由IκBα的降解以及p65的磷酸化和核易位证明。上游IκB激酶的抑制或缺失在分化的神经元细胞或小鼠胚胎成纤维细胞中可显着降低SINV复制，但在未分化的神经元细胞或小鼠胚胎成纤维细胞中则不会。抑制NF-κB不会影响感染的建立，复制复合物的形成，非结构蛋白的合成或分化神经元中病毒RNA的合成。但是，结构蛋白的翻译受到损害，真核翻译起始因子2（eIF2α）的α亚基的磷酸化降低，并且宿主蛋白的合成得以维持，这表明NF-κB激活参与了感染过程中翻译的调控。成熟的神经元。抑制或删除双链RNA激活的蛋白激酶（PKR）也减少了eIF2α磷酸化，病毒结构蛋白的翻译和病毒的产生。因此，经典的NF-κB激活与PKR协同作用，通过促进病毒结构蛋白的翻译来促进分化神经元中SINV的复制。重要信息蚊媒甲病毒是全世界病毒性脑脊髓炎的重要且日益增长的病因。甲型病毒性神经元感染的结果与宿主年龄有关，并且受神经元成熟状态的影响很大，分化成熟的神经元比未分化的未成熟神经元对感染的抵抗力更高。目前仅部分定义了在神经元成熟过程中发生变化并影响病毒感染结果的生物学因素。这些研究调查了NF-κB在确定成熟和不成熟神经元中α病毒感染的结果中的作用。规范性NF-κB激活的抑制通过调节蛋白质合成和限制病毒结构蛋白的产生而降低了成熟神经元中的alphavirus复制，但对未成熟神经元或成纤维细胞中的病毒复制影响很小。因此，NF-κB是一个信号通路，影响神经元中α病毒感染的依赖于成熟的结局，并突出了细胞环境在确定信号通路激活作用中的重要性。规范性NF-κB激活的抑制通过调节蛋白质合成和限制病毒结构蛋白的产生而降低了成熟神经元中的alphavirus复制，但对未成熟神经元或成纤维细胞中的病毒复制影响很小。因此，NF-κB是一个信号通路，影响神经元中α病毒感染的依赖于成熟的结局，并突出了细胞环境在确定信号通路激活作用中的重要性。规范性NF-κB激活的抑制通过调节蛋白质合成和限制病毒结构蛋白的产生而降低了成熟神经元中的alphavirus复制，但对未成熟神经元或成纤维细胞中的病毒复制影响很小。因此，NF-κB是一个信号通路，影响神经元中α病毒感染的依赖于成熟的结局，并突出了细胞环境在确定信号通路激活作用中的重要性。