USP25 Regulates EGFR Fate by Modulating EGF-Induced Ubiquitylation Dynamics.

Carlos A Niño,Giovanni Giangreco,Nadine Wollscheid,Simona Polo,Elena Maspero

doi:10.3390/biom10111548

Abstract

Deregulated epidermal growth factor receptor (EGFR) signaling is a key feature in different stages of oncogenesis. One important mechanism whereby cancer cells achieve increased and uncontrolled EGFR signaling is escaping down-modulation of the receptor. Ubiquitylation of the EGFR plays a decisive role in this process, as it regulates receptor internalization, trafficking and degradation. Deubiquitinating enzymes (DUBs) may oppose the ubiquitylation process, antagonizing or even promoting receptor degradation. Here, we use qualitative and quantitative assays to measure EGFR internalization and degradation after Ubiquitin Specific Peptidase 25 (USP25) depletion. We show that, by acting at the early steps of EGFR internalization, USP25 restrains the degradation of the EGFR by assisting in the association of the E3 ubiquitin ligase c-Cbl with EGFR, thereby modulating the amplitude of ubiquitylation on the receptor. This study establishes USP25 as a negative regulator of the EGFR down-modulation process and suggests that it is a promising target for pharmacological intervention to hamper oncogenic growth signals in tumors that depend on the EGFR.

Highlights

The epidermal growth factor receptor (EGFR) belongs to the ErbB family of Receptor Tyrosine Kinases (RTKs) and exerts a fundamental role in development, tissue wound healing and organ physiology [1,2]
Cells were stimulated with high-dose EGF (100 ng/mL) for different timepoints and the kinetics of EGFR degradation was assessed by immunoblot (Figure 1A) or dissociation-enhanced lanthanide fluorescence immunoassay (DELFIA) assay (Figure 1B)
Enhanced EGFR degradation kinetics was observed upon Ubiquitin Specific Peptidase 25 (USP25) KD

Summary

Introduction

The epidermal growth factor receptor (EGFR) belongs to the ErbB family of Receptor Tyrosine Kinases (RTKs) and exerts a fundamental role in development, tissue wound healing and organ physiology [1,2]. Activation of EGFR signaling occurs when a cognate ligand(s) (i.e., EGF) binds to the extracellular EGFR domain, inducing receptor dimerization and activation of its intracellular tyrosine kinase domain which, in turn, triggers a downstream signaling cascade [1]. The aberrant signaling can be a consequence of EGFR and/or ligand(s) overexpression, EGFR mutations that cause spontaneous dimerization or activation, alterations in the EGFR signaling cascade, or sustained signaling caused by inefficient EGFR degradation [4,5,6]. EGF stimulation induces EGFR internalization through two major pathways, namely clathrin-mediated endocytosis (CME) and non-clathrin endocytic pathway (NCE), resulting in different EGFR fates and signal extension [6]. Ubiquitylation of the EGFR by the E3 ligase c-Cbl is dispensable for CME [8,9], while it is required for the activation of the NCE pathway [10,11,12]. NCE represents the main mechanism for signal attenuation to protect cells from overstimulation

Methods

Results

Discussion

Conclusion