University of Colorado, Denver, Anschutz Medical Campus, Aurora, CO, USA.
J Virol. 2013 Mar;87(6):3447-60. doi: 10.1128/JVI.02324-12. Epub 2013 Jan 9.
Reovirus infection is a well-characterized experimental system for the study of viral pathogenesis and antiviral immunity within the central nervous system (CNS). We have previously shown that c-Jun N-terminal kinase (JNK) and the Fas death receptor each play a role in neuronal apoptosis occurring in reovirus-infected brains. Death-associated protein 6 (Daxx) is a cellular protein that mechanistically links Fas signaling to JNK signaling in several models of apoptosis. In the present study, we demonstrate that Daxx is upregulated in reovirus-infected brain tissue through a type I interferon-mediated mechanism. Daxx upregulation is limited to brain regions that undergo reovirus-induced apoptosis and occurs in the cytoplasm and nucleus of neurons. Cytoplasmic Daxx is present in Fas-expressing cells during reovirus encephalitis, suggesting a role for Daxx in Fas-mediated apoptosis following reovirus infection. Further, in vitro expression of a dominant negative form of Daxx (DN-Daxx), which binds to Fas but which does not transmit downstream signaling, inhibits apoptosis of reovirus-infected cells. In contrast, in vitro depletion of Daxx results in increased expression of caspase 3 and apoptosis, suggesting that Daxx plays an antiapoptotic role in the nucleus. Overall, these data imply a regulatory role for Daxx in reovirus-induced apoptosis, depending on its location in the nucleus or cytoplasm.
呼肠孤病毒感染是研究中枢神经系统(CNS)中病毒发病机制和抗病毒免疫的一个特征明确的实验系统。我们之前已经表明,c-Jun N 端激酶(JNK)和 Fas 死亡受体都在呼肠孤病毒感染的大脑中发生的神经元凋亡中发挥作用。死亡相关蛋白 6(Daxx)是一种细胞蛋白,在几种凋亡模型中,它在 Fas 信号传导和 JNK 信号传导之间起到机械连接作用。在本研究中,我们证明 Daxx 通过 I 型干扰素介导的机制在呼肠孤病毒感染的脑组织中上调。Daxx 的上调仅限于发生呼肠孤病毒诱导的凋亡的脑组织区域,并且发生在神经元的细胞质和核中。在呼肠孤病毒脑炎期间,细胞质中的 Daxx 存在于 Fas 表达细胞中,这表明 Daxx 在呼肠孤病毒感染后 Fas 介导的凋亡中起作用。此外,体外表达一种 Fas 结合但不传递下游信号的显性负形式的 Daxx(DN-Daxx)抑制呼肠孤病毒感染细胞的凋亡。相比之下,体外耗尽 Daxx 会导致 caspase 3 和凋亡的表达增加,表明 Daxx 在核中发挥抗凋亡作用。总体而言,这些数据表明 Daxx 在呼肠孤病毒诱导的凋亡中具有调节作用,具体取决于其在核或细胞质中的位置。