Constitutive and ligand-induced EGFR signalling triggers distinct and mutually exclusive downstream signalling networks

• DOI: 10.1038/ncomms6811
• Publication Date: 2014-12-15T14:49:11Z
• Authors: Sharmistha Chakra...; Li Li; Vineshkumar Thidi...; Gao Guo; Kimmo J. Hatanpaa; Bruce Mickey; Rhonda F. Souza; Peggy Vo; Joachim Herz; Mei-Ru Chen; David A. Boothman; Tej K. Pandita; David H. Wang; Ganes C. Sen; Amyn A. Habib
• Keywords: 0301 basic medicine; Epidermal Growth Factor; Brain Neoplasms; Primary Cell Culture; Membrane Proteins; RNA-Binding Proteins; Antineoplastic Agents; Apoptosis; Protein Serine-Threonine Kinases; Article; 3. Good health; ErbB Receptors; Gene Expression Regulation, Neoplastic; 03 medical and health sciences; Shc Signaling Adaptor Proteins; Cell Line, Tumor; Humans; Interferon Regulatory Factor-3; Phosphorylation; Carrier Proteins; Extracellular Signal-Regulated MAP Kinases; Glioblastoma; Proto-Oncogene Proteins c-akt; Adaptor Proteins, Signal Transducing

Epidermal growth factor receptor (EGFR) overexpression plays an important oncogenic role in cancer. Regular EGFR protein levels are increased in cancer cells and the receptor then becomes constitutively active. However, downstream signals generated by constitutively activated EGFR are unknown. Here we report that the overexpressed EGFR oscillates between two distinct and mutually exclusive modes of signalling. Constitutive or non-canonical EGFR signalling activates the transcription factor IRF3 leading to expression of IFI27, IFIT1 and TRAIL. Ligand-mediated activation of EGFR switches off IRF3-dependent transcription, activates canonical extracellular signal-regulated kinase (ERK) and Akt signals, and confers sensitivity to chemotherapy and virus-induced cell death. Mechanistically, the distinct downstream signals result from a switch of EGFR-associated proteins. EGFR constitutively complexes with IRF3 and TBK1 leading to TBK1 and IRF3 phosphorylation. Addition of epidermal growth factor dissociates TBK1, IRF3 and EGFR leading to a loss of IRF3 activity, Shc-EGFR association and ERK activation. Finally, we provide evidence for non-canonical EGFR signalling in glioblastoma.