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CIN85 regulates ubiquitination and degradative endosomal sorting of the EGF receptor

Sissel Beate Rønning1, Nina Marie Pedersen, Inger Helene Madshus

  • 1Institute of Pathology, Faculty of Medicine, University of Oslo, Oslo, Norway.

Experimental Cell Research
|June 4, 2011
PubMed

Insights

CIN85 protein impacts epidermal growth factor receptor (EGFR) sorting in endosomes, not initial internalization. Depleting CIN85 delays EGFR degradation and increases EGF recycling, clarifying its role in endosomal trafficking.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • CIN85 protein interacts with proteins involved in endocytosis and intracellular sorting.
  • The precise function of CIN85 in endocytosis remains unclear, particularly concerning the epidermal growth factor receptor (EGFR).

Purpose of the Study:

  • To investigate the role of CIN85 in epidermal growth factor (EGF)-induced EGFR internalization versus endosomal sorting.
  • To elucidate the functional significance of CIN85 in the trafficking and degradation pathways of the EGFR.

Main Methods:

  • Over-expression of a dominant-negative CIN85 mutant (three SH3 domains).
  • RNA interference (RNAi) to knock down CIN85 expression.
  • Analysis of EGF-EGFR uptake, ubiquitination, degradation, and recycling.

Main Results:

  • Over-expression of dominant-negative CIN85 inhibited EGF internalization.
  • CIN85 knockdown did not affect EGF-EGFR uptake but decreased EGF-induced EGFR ubiquitination.
  • CIN85 depletion delayed EGF-EGFR degradation and increased EGF recycling.
  • CIN85 constitutively associates with Hrs, supporting its role in endosomal sorting.

Conclusions:

  • CIN85 plays a critical role in the endosomal sorting of ubiquitinated EGFR, rather than initial EGFR internalization.
  • CIN85 influences EGFR degradation and recycling pathways.
  • The constitutive association of CIN85 with Hrs strengthens its proposed function in endosomal EGFR sorting.

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