Hepatitis B Virus X Protein Stabilizes Cyclin D1 and Increases Cyclin D1 Nuclear Accumulation through ERK-Mediated Inactivation of GSK-3β
Hepatitis B Virus X Protein Stabilizes Cyclin D1 and Increases Cyclin D1 Nuclear Accumulation through ERK-Mediated Inactivation of GSK-3β
复制标题
乙型肝炎病毒 X 蛋白通过 ERK 介导的 GSK-3beta 失活来稳定 Cyclin D1 并增加 Cyclin D1 核积累。
DOI：
10.1158/1940-6207.capr-14-0384
复制
发表时间：
2015-05-01
影响因子：
3.3
通讯作者：
Lu, Fengmin
中科院分区：
文献类型：
--
作者：
Chen, Xiangmei;Zhang, Ling;Lu, Fengmin
B型肝炎病毒X蛋白（HBx）在肝细胞癌（HCC）的发病机制中起重要作用。已经表明HBx对细胞周期蛋白D1的转录激活与HCC的发展有关。然而，许多研究表明，细胞周期蛋白D1单独过表达是不足以驱动致癌转化。在此，我们研究HBx是否可以稳定细胞周期蛋白D1和诱导细胞周期蛋白D1蛋白核积累，从而加速肝癌的发生。HBx对细胞周期蛋白D1稳定性的影响通过基于细胞的转染、Western印迹、免疫沉淀、免疫细胞荧光染色和流式细胞术测定进行评估。结果表明，HBx在HCC细胞中的异位表达可使cyclin D1蛋白的半衰期从40-60分钟延长至80-110分钟。HBx主要在细胞周期的S期稳定细胞周期蛋白D1，其方式依赖于GSK-3 β的失活，而GSK-3 β的失活是由ERK激活介导的。HBx还可促进细胞周期蛋白D1在细胞核内的积累，而GSK-3 β组成型活性突变体沿着HBx共转染可逆转HBx诱导的细胞核内积累和随后的细胞增殖。此外，HBx和细胞核细胞周期蛋白D1水平之间的正相关关系，建立在HCC标本中检测的免疫组化分析。综上所述，我们的研究结果表明，HBx可以通过ERK介导的GSK-3 β失活来稳定和增加细胞周期蛋白D1的核积累。这种HBx诱导的cyclin D1上调可能在HCC的发生和发展中起重要作用。
The Hepatitis B virus X protein (HBx) contributes centrally to the pathogenesis of hepatocellular carcinoma (HCC). It has been suggested that the transcriptional activation of cyclin D1 by HBx is implicated in the development of HCC. However, numerous studies have shown that overexpression of cyclin D1 alone is not sufficient to drive oncogenic transformation. Herein, we investigated whether HBx can stabilize cyclin D1 and induce cyclin D1 protein nuclear accumulation, and thereby accelerate hepatocarcinogenesis. The effects of HBx on cyclin D1 stabilization were assessed in cell-based transfection, Western blot, immunoprecipitation, immunocytofluorescence staining, and flow-cytometric assays. The results demonstrated that ectopic expression of HBx in HCC cells could extend the half-life of cyclin D1 protein from 40-60 minutes to 80-110 minutes. HBx stabilized cyclin D1 primarily in the S phase of the cell cycle, in a manner dependent on the inactivation of GSK-3 beta, which was mediated by ERK activation. HBx also prompted the nuclear accumulation of cyclin D1, and cotransfection of the constitutively active mutant of GSK-3 beta along with HBx could reverse the nuclear accumulation and subsequent cell proliferation induced by HBx. Further, a positive correlation between HBx and nuclear cyclin D1 level was established in HCC specimens detected by an immunohistochemical assay. Taken together, our results indicated that HBx could stabilize and increase cyclin D1 nuclear accumulation through ERK-mediated inactivation of GSK-3 beta. This HBx-induced cyclin D1 upregulation might play an important role in HCC development and progression.