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CacyBP/SIP protein reduces p53 stability by enhancing Mdm2 activity in p53 mutant glioma cells

Fengyuan Qian1, Tianjin Tang1,2, Shiquan Wang1

  • 1Institute of Nervous System Diseases, The Affiliated Hospital of Xuzhou Medical University, Xuzhou Medical University, Xuzhou, China.

Neoplasma
|September 4, 2020
PubMed

Insights

Calcyclin-binding protein (CacyBP/SIP) promotes glioma cell proliferation by degrading p53 protein. This occurs via interaction with Mdm2, enhancing p53 ubiquitination and degradation, offering a potential therapeutic target.

Area of Science:

  • Molecular Biology
  • Oncology
  • Biochemistry

Background:

  • Calcyclin-binding protein or Siah-1-interacting protein (CacyBP/SIP) has been shown to promote glioma cell proliferation.
  • The precise mechanism underlying CacyBP/SIP's role in glioma remains unclear.

Purpose of the Study:

  • To elucidate the mechanism by which CacyBP/SIP regulates glioma cell proliferation.
  • To investigate the interaction between CacyBP/SIP, p53, and Mdm2 in glioma cells.

Main Methods:

  • Western blotting to assess protein and mRNA levels of p53.
  • Co-immunoprecipitation to study protein interactions.
  • Ubiquitination assays and proteasome degradation studies.
  • Analysis of CacyBP/SIP and p53 protein levels in human glioma tissues.

Main Results:

  • CacyBP/SIP reduced p53 protein levels, but not mRNA, in p53 mutant U251 cells.
  • In p53 wild-type U87 cells, CacyBP/SIP did not affect proliferation or p53 levels.
  • CacyBP/SIP interacted with p53 and Mdm2, promoting p53 ubiquitination and degradation.
  • Mdm2 inhibition stabilized p53, while CacyBP/SIP enhanced p53 ubiquitination dose-dependently.
  • Inverse correlation observed between CacyBP/SIP and p53 protein levels in human glioma tissues.

Conclusions:

  • CacyBP/SIP promotes mutant p53 degradation by enhancing Mdm2 E3 ligase activity.
  • This reveals a novel regulatory pathway for mutant p53 in glioma.
  • Targeting the CacyBP/SIP pathway presents a potential therapeutic strategy for glioma.

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