title: Valosin-containing protein regulates the proteasome-mediated degradation of DNA-PKcs in glioma cells.
abstract: 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.
authors.affiliation: Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: N
authors.initials: N
authors.lastname: Jiang
authors.forename: Y
authors.initials: Y
authors.lastname: Shen
authors.forename: X
authors.initials: X
authors.lastname: Fei
authors.forename: K
authors.initials: K
authors.lastname: Sheng
authors.forename: P
authors.initials: P
authors.lastname: Sun
authors.forename: Y
authors.initials: Y
authors.lastname: Qiu
authors.forename: J
authors.initials: J
authors.lastname: Larner
authors.forename: L
authors.initials: L
authors.lastname: Cao
authors.forename: X
authors.initials: X
authors.lastname: Kong
authors.forename: J
authors.initials: J
authors.lastname: Mi
mesh_terms: D000251:Adenosine Triphosphatases / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000532:radiotherapy; D018797:Cell Cycle Proteins / Q000502:physiology*; D045744:Cell Line, Tumor; D004249:DNA Damage; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D005909:Glioblastoma / Q000378:metabolism* / Q000401:mortality / Q000532:radiotherapy; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D011836:Radiation Tolerance; D000074405:Valosin Containing Protein; D023041:Xenograft Model Antitumor Assays
chemical_list: D018797:Cell Cycle Proteins; D051747:DNA-Activated Protein Kinase; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein; C000614179:Vcp protein, mouse