Valosin-containing protein regulates the proteasome-mediated degradation of DNA-PKcs in glioma cells
Valosin-containing protein regulates the proteasome-mediated degradation of DNA-PKcs in glioma cells
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Valosin 含蛋白调节胶质瘤细胞中蛋白酶体介导的 DNA-PKcs 降解
DOI：
10.1038/cddis.2013.171
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发表时间：
2013-05-01
影响因子：
9
通讯作者：
Mi, J.
中科院分区：
文献类型：
--
作者：
Jiang, N.;Shen, Y.;Mi, J.
DNA依赖性蛋白激酶（DNA-PK）在胶质母细胞瘤细胞DNA损伤修复和辐射敏感性调节中具有重要作用。VCP（含缬氨酸蛋白）是一种调节泛素依赖性蛋白质降解的伴侣蛋白，被DNA-PK磷酸化并被募集到DNA双链断裂位点以调节DNA损伤修复。然而，目前尚不清楚VCP是否参与DNA-PKcs（DNA-PK催化亚基）降解或是否调节胶质母细胞瘤的放射敏感性。我们的数据表明，DNA-PKcs是泛素化的，并结合到VCP。VCP敲低导致胶质母细胞瘤细胞中DNA-PKcs蛋白的积累，蛋白酶体抑制剂MG 132协同这种增加。正如预期的那样，这种增加促进了几种胶质母细胞瘤细胞系中DNA修复的效率;反过来，这种增强的活性降低了胶质母细胞瘤细胞的辐射敏感性并延长了体外存活分数。此外，相对于对照异种移植的胶质母细胞瘤小鼠，胶质母细胞瘤细胞中的VCP敲低减少了放射治疗的异种移植小鼠的存活时间。此外，在WHO Ⅳ级星形细胞瘤患者的GBM中，VCP蛋白表达下调率为1.25%，且VCP蛋白表达水平与患者的生存期相关（R2 = 0.5222，P< 0.05）。这些结果表明，VCP调节DNA-PKcs降解，并增加GBM细胞对辐射的敏感性。
DNA-dependent protein kinase (DNA-PK) has an important role in the repair of DNA damage and regulates the radiation sensitivity of glioblastoma cells. The VCP (valosine-containing protein), a chaperone protein that regulates ubiquitin-dependent protein degradation, is phosphorylated by DNA-PK and recruited to DNA double-strand break sites to regulate DNA damage repair. However, it is not clear whether VCP is involved in DNA-PKcs (DNA-PK catalytic subunit) degradation or whether it regulates the radiosensitivity of glioblastoma. Our data demonstrated that DNA-PKcs was ubiquitinated and bound to VCP. VCP knockdown resulted in the accumulation of the DNA-PKcs protein in glioblastoma cells, and the proteasome inhibitor MG132 synergised this increase. As expected, this increase promoted the efficiency of DNA repair in several glioblastoma cell lines; in turn, this enhanced activity decreased the radiation sensitivity and prolonged the survival fraction of glioblastoma cells in vitro. Moreover, the VCP knockdown in glioblastoma cells reduced the survival time of the xenografted mice with radiation treatment relative to the control xenografted glioblastoma mice. In addition, the VCP protein was also downregulated in∼ 25% of GBM tissues from patients (WHO, grade IV astrocytoma), and the VCP protein level was correlated with patient survival (R 2= 0.5222, P< 0.05). These findings demonstrated that VCP regulates DNA-PKcs degradation and increases the sensitivity of GBM cells to radiation.