Identification of Both Positive and Negative Domains within the Epidermal Growth Factor Receptor COOH-terminal Region for Signal Transducer and Activator of Transcription (STAT) Activation

• Published in: The Journal of biological chemistry 2002-08, Vol.277 (34), p.30716-30723
• Main Authors: Xia, Ling, Wang, Lijuan, Chung, Alicia S, Ivanov, Stanimir S, Ling, Mike Y, Dragoi, Ana M, Platt, Adam, Gilmer, Tona M, Fu, Xin-Yuan, Chin, Y Eugene
• Format: Article
• Language: English
• Subjects: Binding Sites; Carrier Proteins - physiology; DNA-Binding Proteins - metabolism; ErbB Receptors - chemistry; ErbB Receptors - physiology; Humans; Intracellular Signaling Peptides and Proteins; Proteins - physiology; Repressor Proteins; Signal Transduction; STAT1 Transcription Factor; STAT3 Transcription Factor; Suppressor of Cytokine Signaling 1 Protein; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins; Trans-Activators - metabolism; Transcription Factors
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M202823200

The cytoplasmic region of human epidermal growth factor receptor (EGFR) contains an intrinsic tyrosine kinase (697–955) followed by a 231-residue-long COOH-terminal tail (C-tail), which contains multiple tyrosine residues. To examine the role of the EGFR C-tail in signal transducer and activator of transcription (STAT) activation, a series of EGFR C-tail truncations were constructed. Transient transfection of 293 cells with EGFR lacking the C-tail, i.e. Y974ΔEGFR or Y992ΔEGFR, led to EGF-independent or constitutive STAT activation, whereas EGF-dependent STAT activation was restored with truncations made COOH-terminal to the next tyrosine residue, i.e. EGFR-Y1045Δ. Transfection with the-truncated form EGFR-Y954Δ resulted in the loss of STAT activation, suggesting that the sequence between Tyr 974 and Tyr 954 is essential for STAT activation. Phosphopeptide competition analysis revealed multiple tyrosine residues within the C-tail that can act as the docking sites for both Stat1 and Stat3. A region that negatively regulated STAT activation was also identified, extending from Tyr 1114 to Glu 1172 , consistent with the ability of this region to recruit a suppressor of cytokine signaling factors SOCS1 and SOCS3. When cotransfected with the full-length EGFR, but not Y992ΔEGFR, SOCS1 or SOCS3 inhibited STAT activation by EGF in 293 cells. This suggests that both SOCS1 and SOCS3 can negatively regulate EGFR activation, presumably by inducing ubiquitination-dependent EGFR degradation upon ligand binding. These findings may therefore offer clues to how the EGF receptor C-tail regulates STAT activity.