Gene 33 Is an Endogenous Inhibitor of Epidermal Growth Factor (EGF) Receptor Signaling and Mediates Dexamethasone-induced Suppression of EGF Function

• Published in: The Journal of biological chemistry 2005-01, Vol.280 (4), p.2924-2933
• Main Authors: Xu, Dazhong, Makkinje, Anthony, Kyriakis, John M.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - physiology; Adenoviridae - genetics; Amino Acid Sequence; Animals; Blotting, Northern; Blotting, Western; Carrier Proteins - genetics; Carrier Proteins - physiology; Cell Line; Dexamethasone - pharmacology; DNA, Complementary - metabolism; Electrophoresis, Polyacrylamide Gel; Epidermal Growth Factor - metabolism; ErbB Receptors - metabolism; Extracellular Signal-Regulated MAP Kinases - metabolism; Glucocorticoids - pharmacology; Glutathione Transferase - metabolism; Guanosine Triphosphate - chemistry; Humans; Immunoprecipitation; Intracellular Signaling Peptides and Proteins; Models, Genetic; Molecular Sequence Data; Oligonucleotides - chemistry; Phosphorylation; Platelet-Derived Growth Factor - metabolism; Protein Binding; Protein Structure, Tertiary; Rats; RNA Interference; RNA, Double-Stranded - chemistry; Sequence Homology, Amino Acid; Serine - chemistry; Signal Transduction; Time Factors; Transfection; Tumor Suppressor Proteins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M408907200

We report a mechanism by which the adapter protein Gene 33 (also called RALT and MIG6) regulates epidermal growth factor receptor (EGFR) signaling. We find that Gene 33 inhibits EGFR autophosphorylation and specifically blunts epidermal growth factor (EGF)-induced activation and/or phosphorylation of Ras, ERK, JNK, Akt/PKB, and retinoblastoma protein. The Ack homology domain of Gene 33, which contains the previously identified EGFR binding domain, is both necessary and sufficient for this inhibition of EGFR autophosphorylation. The endogenous Gene 33 polypeptide is induced by EGF, platelet-derived growth factor, serum, and dexamethasone (Dex) in Rat 2 rat fibroblasts. Dex induces Gene 33 expression and inhibits EGFR phosphorylation and EGF signaling. RNA interference-mediated silencing of Gene 33 significantly reverses this effect. Overexpression of Gene 33 completely blocks EGF-induced protein and DNA synthesis in Rat 2 cells, whereas gene 33 RNA interference substantially enhances EGF-induced protein and DNA synthesis in Rat 2 cells. Our results indicate that Gene 33 is a physiological feedback inhibitor of the EGFR, functioning to inhibit EGFR phosphorylation and all events induced by EGFR activation. Our results also indicate a role for Gene 33 in the suppression, by Dex, of EGF signaling pathways. We propose that Gene 33 may function in the cross-talk between EGF signaling and other mitogenic and/or stress signaling pathways.