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Src phosphorylation converts Mdm2 from a ubiquitinating to a neddylating E3 ligase

Christopher N Batuello1, Paula M Hauck2, Jaimie M Gendron1

  • 1Department of Biochemistry and Molecular Biology and.

Proceedings of the National Academy of Sciences of the United States of America
|January 28, 2015
PubMed

Insights

Activated c-Src kinase phosphorylates Mdm2, increasing its stability and neddylating activity. This Mdm2-dependent Nedd8 conjugation inactivates tumor suppressor p53, offering a therapeutic target for wild-type p53 cancers.

Area of Science:

  • Molecular Biology
  • Oncology
  • Biochemistry

Background:

  • Murine double minute-2 protein (Mdm2) regulates proteins, including the tumor suppressor p53, through ubiquitin or Nedd8 conjugation.
  • The regulation of Mdm2's neddylating activity is not well understood, unlike its E3 ubiquitin ligase activity.

Purpose of the Study:

  • To investigate the regulation of Mdm2's neddylating activity.
  • To elucidate the mechanism by which Mdm2 neutralizes p53 in proliferating cells.

Main Methods:

  • Investigated the effect of c-Src kinase on Mdm2 phosphorylation at Y281 and Y302.
  • Assessed Mdm2 stability and its association with Ubc12, the E2 enzyme for neddylation.
  • Examined the impact of Mdm2-dependent Nedd8 conjugation on p53 transcriptional activity.
  • Utilized small molecule inhibitors targeting Src and Ubc12.

Main Results:

  • Activated c-Src kinase phosphorylates Mdm2 at Y281 and Y302, enhancing Mdm2 stability.
  • Phosphorylation increases Mdm2 association with Ubc12, facilitating Nedd8 conjugation to p53.
  • Mdm2-mediated Nedd8 conjugation of p53 leads to transcriptionally inactive p53.
  • Inhibitors of Src or Ubc12 reversed the inactivation of p53.

Conclusions:

  • c-Src kinase regulates Mdm2 neddylating activity through phosphorylation, impacting p53 stability and function.
  • This pathway provides a mechanism for p53 neutralization in proliferating cells.
  • Targeting the Nedd8 pathway presents a potential therapeutic strategy for wild-type p53 tumors.
Keywords:
Mdm2Nedd8Src

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