Danthi Pranav, Coffey Caroline M, Parker John S L, Abel Ty W, Dermody Terence S
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA.
PLoS Pathog. 2008 Dec;4(12):e1000248. doi: 10.1371/journal.ppat.1000248. Epub 2008 Dec 26.
Apoptosis plays an important role in the pathogenesis of reovirus encephalitis. Reovirus outer-capsid protein mu1, which functions to penetrate host cell membranes during viral entry, is the primary regulator of apoptosis following reovirus infection. Ectopic expression of full-length and truncated forms of mu1 indicates that the mu1 phi domain is sufficient to elicit a cell death response. To evaluate the contribution of the mu1 phi domain to the induction of apoptosis following reovirus infection, phi mutant viruses were generated by reverse genetics and analyzed for the capacity to penetrate cell membranes and elicit apoptosis. We found that mutations in phi diminish reovirus membrane penetration efficiency by preventing conformational changes that lead to generation of key reovirus entry intermediates. Independent of effects on membrane penetration, amino acid substitutions in phi affect the apoptotic potential of reovirus, suggesting that phi initiates apoptosis subsequent to cytosolic delivery. In comparison to wild-type virus, apoptosis-defective phi mutant viruses display diminished neurovirulence following intracranial inoculation of newborn mice. These results indicate that the phi domain of mu1 plays an important regulatory role in reovirus-induced apoptosis and disease.
细胞凋亡在呼肠孤病毒脑炎的发病机制中起重要作用。呼肠孤病毒外 capsid 蛋白 mu1 在病毒进入期间负责穿透宿主细胞膜，是呼肠孤病毒感染后细胞凋亡的主要调节因子。mu1 的全长和截短形式的异位表达表明，mu1 的 phi 结构域足以引发细胞死亡反应。为了评估 mu1 的 phi 结构域对呼肠孤病毒感染后诱导细胞凋亡的作用，通过反向遗传学产生了 phi 突变病毒，并分析了其穿透细胞膜和引发细胞凋亡的能力。我们发现，phi 中的突变通过阻止导致关键呼肠孤病毒进入中间体产生的构象变化，降低了呼肠孤病毒的膜穿透效率。与对膜穿透的影响无关，phi 中的氨基酸取代影响呼肠孤病毒的凋亡潜力，表明 phi 在胞质递送后启动细胞凋亡。与野生型病毒相比，凋亡缺陷型 phi 突变病毒在新生小鼠颅内接种后显示出神经毒力降低。这些结果表明，mu1 的 phi 结构域在呼肠孤病毒诱导的细胞凋亡和疾病中起重要调节作用。
