Hepatitis B Virus Encoded X Protein Suppresses Apoptosis by Inhibition of the Caspase-Independent Pathway
Hepatitis B Virus Encoded X Protein Suppresses Apoptosis by Inhibition of the Caspase-Independent Pathway
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DOI：
10.1021/pr2012297
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发表时间：
2012-10-01
影响因子：
4.4
通讯作者：
He, Fuchu
中科院分区：
文献类型：
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作者：
Liu, Haiying;Yuan, Yanzhi;He, Fuchu
B型肝炎病毒（HBV）编码的X蛋白（HBx）与肝细胞癌的细胞凋亡及相关致病事件有关。然而，HBx作用的潜在分子机制在很大程度上尚不清楚。我们在温和条件下使用串联亲和纯化来深入了解HBV产生的HepG2.2.15细胞中的HBx相互作用组，并通过质谱法鉴定了49种可能与HBx相关的蛋白质。新鉴定了两种caspase非依赖性凋亡途径的关键蛋白，凋亡诱导因子（AIF）和同源AMID（AIF同源凋亡相关诱导因子）。我们证实了HBx与AIF和AMID的相互作用，分别通过相互免疫共沉淀实验。我们观察到HBx减少的AIF介导的凋亡的表达和HBx与AIF和AMID共定位，主要在细胞质中。此外，HBx的胞浆水平升高可抑制AIF的胞核转位。在这里，我们提出了第一个详细的分子证据表明，HBx可以通过抑制半胱天冬酶非依赖性细胞凋亡途径抑制细胞凋亡。这种对细胞凋亡的抑制涉及AIF的细胞核易位的抑制，尽管AMID的测试并不确定。这些发现为HBV抑制细胞凋亡的新机制提供了重要的见解。
Hepatitis B virus (HBV) encoded X protein (HBx) has been implicated in apoptotic and related pathogenic events during hepatocellular carcinoma. However, the underlying molecular mechanism through which HBx acts is largely unclear. We used tandem affinity purification under mild conditions to gain insight into the HBx interactome in HBV-producing HepG2.2.15 cells and identified 49 proteins by mass spectrometry that are potentially associated with HBx. Two of the key proteins of the caspase-independent apoptosis pathway were newly identified, apoptosis-inducing factor (AIF) and the homologous AMID (AIF-homologue mitochondrion-associated inducer of death). We confirmed the interactions of HBx with AIF and with AMID by reciprocal coimmunoprecipitation experiments, respectively. We observed the expression of HBx-reduced AIF-mediated apoptosis and HBx colocalization with AIF and AMID, principally in the cytoplasm. Furthermore, the elevated cytoplasmic levels of HBx could inhibit mitochondrion-to-nucleus translocation of AIF. Here, we present the first detailed molecular evidence that HBx can repress apoptosis via inhibition of the caspase-independent apoptosis pathway. This inhibition of apoptosis involves the repression of the mitochondrion-to-nucleus translocation of AIF, although tests with AMID were not conclusive. These findings provide important insights into the new mechanism of the apoptosis inhibition by HBV.