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Regulation of epidermal growth factor receptor down-regulation by UBPY-mediated deubiquitination at endosomes

Emi Mizuno1, Takanobu Iura, Akiko Mukai

  • 1Department of Biological Sciences, Tokyo Institute of Technology, Yokohama 226-8501, Japan.

Molecular Biology of the Cell
|August 27, 2005
PubMed

Insights

The deubiquitinating enzyme UBPY/USP8 negatively regulates epidermal growth factor receptor (EGFR) down-regulation. UBPY/USP8 deubiquitinates EGFR on endosomes, delaying its degradation and signal termination.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Receptor tyrosine kinases, like the epidermal growth factor receptor (EGFR), are crucial for cell signaling.
  • Ligand-activated receptor tyrosine kinases are internalized via endocytosis and trafficked to lysosomes for degradation to terminate signaling.
  • Ubiquitination acts as a key signal for the lysosomal sorting of these receptors from endosomes.

Purpose of the Study:

  • To investigate the role of the deubiquitinating enzyme UBPY/USP8 in the down-regulation of the epidermal growth factor receptor (EGFR).
  • To elucidate the mechanism by which UBPY/USP8 influences EGFR ubiquitination, trafficking, and degradation.

Main Methods:

  • Overexpression of UBPY/USP8 and its mutants in EGF-stimulated cells.
  • In vitro deubiquitination assays using immunopurified UBPY/USP8.
  • RNA interference (RNAi) to deplete endogenous UBPY/USP8.
  • Immunoprecipitation and co-localization studies to assess protein interactions and localization on endosomes.

Main Results:

  • Overexpression of UBPY/USP8 reduced EGFR ubiquitination and delayed its degradation.
  • UBPY/USP8 directly deubiquitinated EGFR in vitro.
  • UBPY/USP8 localized to endosomes and interacted with EGFR upon EGF stimulation.
  • Depletion of UBPY/USP8 led to increased EGFR ubiquitination and accelerated degradation.

Conclusions:

  • UBPY/USP8 functions as a negative regulator of EGFR down-regulation.
  • The enzyme deubiquitinates EGFR on endosomes, thereby controlling its degradation rate and the termination of EGF signaling.

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