Epidermal growth factor receptor activation under oxidative stress fails to promote c-Cbl mediated down-regulation

Activation of the epidermal growth factor (EGF) receptor by its ligand, EGF, rapidly enhances receptor internalization and degradation, which desensitizes receptor signaling. In contrast, we have shown previously that exposure to oxidative stress in the form of hydrogen peroxide (H₂O₂) activated the EGF receptor but that the levels of activated receptors did not decline, which resulted in prolonged receptor signaling. This study provides mechanistic insights into these different modes of EGF receptor activation. Here we demonstrate that the pattern of receptor tyrosine phosphorylation induced by H₂O₂ differs from that induced by its ligand, EGF. Importantly, H₂O₂ generates a receptor with negligible phosphorylation at tyrosine 1045, the major docking site for the ubiquitin ligase c-Cbl. As a result, H₂O₂-activated receptors fail to recruit c-Cbl and do not undergo ubiquitination and endocytosis. In summary, H₂O₂ stimulation results in an activated receptor uncoupled from normal down-regulation, a process that may contribute to oxidant-mediated tumorigenesis.