title: Unique role of SNT-2/FRS2beta/FRS3 docking/adaptor protein for negative regulation in EGF receptor tyrosine kinase signaling pathways.
abstract: The membrane-linked docking protein SNT-2/FRS2beta/FRS3 becomes tyrosine phosphorylated in response to fibroblast growth factors (FGFs) and neurotrophins and serves as a platform for recruitment of multiple signaling proteins, including Grb2 and Shp2, to FGF receptors or neurotrophin receptors. We previously reported that SNT-2 is not tyrosine phosphorylated significantly in response to epidermal growth factor (EGF) but that it inhibits ERK activation via EGF stimulation by forming a complex with ERK2. In the present report, we show that expression of SNT-2 suppressed EGF-induced cell transformation and proliferation, and expression level of SNT-2 is downregulated in cancer. The activities of the major signaling molecules in EGF receptor (EGFR) signal transduction pathways, including autophosphorylation of EGFR, were attenuated in cells expressing SNT-2 but not in cells expressing SNT-2 mutants lacking the ERK2-binding domain. Furthermore, SNT-2 constitutively bound to EGFR through the phosphotyrosine binding (PTB) domain both with and without EGF stimulation. Treatment of cells with MEK inhibitor U0126 partially restored the phosphorylation levels of MEK and EGFR in cells expressing SNT-2. On the basis of these findings, we propose a novel mechanism of negative control of EGFR tyrosine kinase activity with SNT-2 by recruiting ERK2, which is the site of negative-feedback loop from ERK, ultimately leading to inhibition of EGF-induced cell transformation and proliferation.
authors.affiliation: Department of Molecular Cellular Oncology and Microbiology, Graduate School, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
authors.forename: L
authors.initials: L
authors.lastname: Huang
authors.forename: M
authors.initials: M
authors.lastname: Watanabe
authors.forename: M
authors.initials: M
authors.lastname: Chikamori
authors.forename: Y
authors.initials: Y
authors.lastname: Kido
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Shibuya
authors.forename: N
authors.initials: N
authors.lastname: Gotoh
authors.forename: N
authors.initials: N
authors.lastname: Tsuchida
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D015536:Down-Regulation / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C113566:FRS3 protein, human; D050505:Mutant Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D016283:Proto-Oncogene Proteins p21(ras)