West Nile virus infection activates the unfolded protein response, leading to CHOP induction and apoptosis
West Nile virus infection activates the unfolded protein response, leading to CHOP induction and apoptosis
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DOI：
10.1128/jvi.01151-07
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发表时间：
2007-10-01
影响因子：
5.4
通讯作者：
Nelson, Jay A.
中科院分区：
文献类型：
--
作者：
Medigeshi, Guruprasad R.;Lancaster, Alissa M.;Nelson, Jay A.
西尼罗河病毒(West Nile Virus，WNV)介导的神经元死亡是WNV脑膜炎和脑炎的标志。然而，西尼罗河病毒诱导神经元损伤的机制尚不清楚。我们用人神经母细胞瘤细胞和原代培养的大鼠海马神经元研究了西尼罗河病毒的神经发病机制。我们观察到，西尼罗河病毒激活了多个未折叠蛋白反应(UPR)途径，导致UPR靶基因的转录和翻译诱导。我们评估了三个主要的UPR途径，即依赖于肌醇需要酶1的X盒结合蛋白1(XBP1)的剪接，激活转录因子6(ATF6)，以及蛋白激酶R样内质网(ER)依赖的真核细胞起始因子2α(eIF2α)的磷酸化在西尼罗河病毒感染细胞中的作用。我们发现，在西尼罗河病毒复制中，XBP1不是必需的，或者可以被其他UPR途径所取代。ATF6被蛋白酶体迅速降解，这与西尼罗河病毒诱导的内质网应激一致。我们进一步观察到eIF2α的瞬时磷酸化和诱导促凋亡的环状AMP反应元件结合转录因子同源蛋白(CHOP)。西尼罗河病毒感染的细胞表现出许多凋亡表型，如(1)诱导生长停滞和DNA损伤诱导基因34，(2)激活caspase-3，(3)裂解聚(ADP-核糖)聚合酶。仅WNV非结构蛋白的表达就足以诱导CHOP的表达。重要的是，西尼罗河病毒在CHOP(-/-)小鼠胚胎成纤维细胞(MEF)中的病毒滴度显著高于野生型MEF，这表明CHOP依赖的细胞过早死亡代表了一种限制病毒复制的宿主防御机制，这可能也是在WNV感染的神经元组织中观察到的广泛神经元丢失的原因。
West Nile virus (WNV)-mediated neuronal death is a hallmark of WNV meningitis and encephalitis. However, the mechanisms of WNV-induced neuronal damage are not well understood. We investigated WNV neuropathogenesis by using human neuroblastoma cells and primary rat hippocampal neurons. We observed that WNV activates multiple unfolded protein response (UPR) pathways, leading to transcriptional and translational induction of UPR target genes. We evaluated the role of the three major UPR pathways, namely, inositol-requiring enzyme 1-dependent splicing of X box binding protein 1 (XBP1) mRNA, activation of activating transcription factor 6 (ATF6), and protein kinase R-like endoplasmic reticulum (ER) kinase-dependent eukaryotic initiation factor 2 alpha (eIF2 alpha) phosphorylation, in WNV-infected cells. We show that XBP1 is nonessential or can be replaced by other UPR pathways in WNV replication. ATF6 was rapidly degraded by proteasomes, consistent with induction of ER stress by WNV. We further observed a transient phosphorylation of eIF2 alpha and induction of the proapoptotic cyclic AMP response element-binding transcription factor homologous protein (CHOP). WNV-infected cells exhibited a number of apoptotic phenotypes, such as (i) induction of growth arrest and DNA damage-inducible gene 34, (ii) activation of caspase-3, and (iii) cleavage of poly(ADP-ribose) polymerase. The expression of WNV nonstructural proteins alone was sufficient to induce CHOP expression. Importantly, WNV grew to significantly higher viral titers in chop(-/-) mouse embryonic fibroblasts (MEFs) than in wild-type MEFs, suggesting that CHOP-dependent premature cell death represents a host defense mechanism to limit viral replication that might also be responsible for the widespread neuronal loss observed in WNV-infected neuronal tissue.