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RFP-mediated ubiquitination of PTEN modulates its effect on AKT activation

James T Lee1, Jing Shan, Jiayun Zhong

  • 1Institute for Cancer Genetics, and Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, 1130 St Nicholas Avenue, New York, NY 10032, USA.

Cell Research
|February 20, 2013
PubMed

Insights

Ret finger protein (RFP) ubiquitinates PTEN, inhibiting its phosphatase activity and PI3K signaling. This RFP-mediated ubiquitination regulates AKT activation, TRAIL expression, and apoptosis, revealing a novel control mechanism for PTEN function.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Cancer Research

Background:

  • The PTEN tumor suppressor is crucial for regulating the phosphatidylinositol-3-kinase (PI3K) signaling pathway.
  • While PTEN ubiquitination affects stability and localization, its impact on phosphatase activity remains unclear.

Purpose of the Study:

  • To investigate the role of ubiquitination in regulating PTEN phosphatase activity.
  • To identify novel ubiquitin ligases that target PTEN.

Main Methods:

  • Identification of Ret finger protein (RFP) as a PTEN-interacting E3 ubiquitin ligase.
  • Analysis of RFP's effect on PTEN ubiquitination, phosphatase activity, and downstream signaling (AKT, TRAIL).
  • Utilizing overexpression and RNA interference (RNAi) techniques to study RFP function.

Main Results:

  • RFP mediates atypical polyubiquitination of PTEN, inhibiting its phosphatase activity without altering stability or localization.
  • RFP overexpression reduces PTEN's inhibitory effect on AKT activation, while RFP knockdown enhances PTEN's suppression of AKT.
  • RFP-mediated ubiquitination of PTEN inhibits TRAIL expression and apoptosis induction.

Conclusions:

  • RFP is a novel E3 ubiquitin ligase that directly inhibits PTEN phosphatase activity through atypical ubiquitination.
  • RFP-mediated ubiquitination plays a critical role in modulating PTEN's function in PI3K signaling, TRAIL expression, and apoptosis.

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