Non-structural protein 4A of Hepatitis C virus accumulates on mitochondria and renders the cells prone to undergoing mitochondria-mediated apoptosis
Non-structural protein 4A of Hepatitis C virus accumulates on mitochondria and renders the cells prone to undergoing mitochondria-mediated apoptosis
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DOI：
10.1099/vir.0.81701-0
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发表时间：
2006-07-01
影响因子：
3.8
通讯作者：
Hotta, Hak
中科院分区：
文献类型：
--
作者：
Nomura-Takigawa, Yuki;Nagano-Fujii, Motoko;Hotta, Hak
丙型肝炎病毒（HCV）的非结构蛋白4A（NS 4A）作为NS 3的辅因子，通过与NS 3形成复合物来增强其酶活性。NS 4A还与其他HCV蛋白（如NS 4 B/NS 5A）形成复合物，以促进在内质网（ER）膜上形成病毒RNA复制复合物。除了其在HCV复制中的重要作用外，NS 4A被认为通过影响细胞功能而参与病毒发病机制。在这项研究中，它被证明，NS 4A不仅定位在ER上，而且在线粒体上单独表达或与NS 3一起以NS 3/4A多聚蛋白的形式和在HCV RNA复制的背景下，在Huh 7细胞携带HCV RNA复制子。此外，NS 4A的表达改变了线粒体的细胞内分布显着，并造成线粒体损伤，证明了崩溃的线粒体跨膜电位和细胞色素c释放到细胞质中，最终导致诱导凋亡，通过激活caspase-3，但不是caspase-8。一致地，与对照Huh 7细胞相比，表达NS 3/4A的Huh 7细胞和携带HCV RNA复制子的Huh 7细胞显示出更倾向于经历放线菌素D诱导的、由HCV介导的凋亡。两者合计，这些结果表明，HCV在某些条件下对感染的细胞产生细胞病变效应（CPE）的可能性，NS 4A是负责的，至少部分，在HCV感染的细胞中的条件CPE。
Non-structural protein 4A (NS4A) of Hepatitis C virus (HCV) functions as a cofactor for NS3 by forming a complex with it to augment its enzymic activities. NS4A also forms a complex with other HCV proteins, such as NS4B/NS5A, to facilitate the formation of the viral RNA replication complex on the encloplasmic reticulum (ER) membrane. In addition to its essential role in HCV replication, NS4A is thought to be involved in viral pathogenesis by affecting cellular functions. In this study, it was demonstrated that NS4A was localized not only on the ER, but also on mitochondria when expressed either alone or together with NS3 in the form of the NS3/4A polyprotein and in the context of HCV RNA replication in Huh7 cells harbouring an HCV RNA replicon. Moreover, NS4A expression altered the intracellular distribution of mitochondria significantly and caused mitochondrial damage, as evidenced by the collapsed mitochondrial transmembrane potential and release of cytochrome c into the cytoplasm, which led ultimately to induction of apoptosis through activation of caspase-3, but not caspase-8. Consistently, Huh7 cells expressing NS3/4A and those harbouring an HCV RNA replicon were shown to be more prone to undergoing actinomycin D-induced, mitochondria-mediated apoptosis, compared with the control Huh7 cells. Taken together, these results suggest the possibility that HCV exerts cytopathic effect (CPE) on the infected cells under certain conditions and that NS4A is responsible, at least in part, for the conditional CPE in HCV-infected cells.