title: EGFR and FGFR signaling through FRS2 is subject to negative feedback control by ERK1/2.
abstract: Fibroblast growth factor (FGF) receptor substrate 2 (FRS2) is a membrane-anchored docking protein that has been shown to play an important role in linking FGF, nerve growth factor (NGF) and glial cell-derived neurotrophic factor (GDNF) receptors with the Ras/mitogen-activated protein (MAP) kinase signaling cascade. Here we provide evidence that FRS2 can also play a role in epidermal growth factor (EGF) signaling. Upon EGF stimulation, FRS2 mediates enhanced MAPK activity and undergoes phosphorylation on tyrosine as well as serine/threonine residues. This involves the direct interaction of the FRS2 PTB domain with the EGFR and results in a significantly altered mobility of FRS2 in SDS-PAGE which is also observed in FGF stimulated cells. This migration shift of FRS2 is completely abrogated by U0126, a specific MAPK kinase 1 (MEK1) inhibitor, suggesting that ERK1/2 acts as serine/threonine kinase upstream of FRS2. Indeed, we show that the central portion of FRS2 constitutively associates with ERK1/2, whereas the FRS2 carboxy-terminal region serves as substrate for ERK2 phosphorylation in response to EGF and FGF stimulation. Notably, tyrosine phosphorylation of FRS2 is enhanced when ERK1/2 activation is inhibited after both EGF and FGF stimulation. These results indicate a ligand-stimulated negative regulatory feedback loop in which activated ERK1/2 phosphorylates FRS2 on serine/threonine residues thereby down-regulating its tyrosine phosphorylation. Our findings support a broader role of FRS2 in EGFR-controlled signaling pathways in A-431 cells and provide insight into a molecular mechanism for ligand-stimulated feedback regulation with FRS2 as a central regulatory switch point.
authors.affiliation: Department of Molecular Biology, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Wu
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Chen
authors.forename: Axel
authors.initials: A
authors.lastname: Ullrich
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000378:metabolism*; D025461:Feedback, Physiological; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D013912:Threonine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C106534:FRS2 protein, human; D008565:Membrane Proteins; D010750:Phosphoproteins; D017468:Receptors, Fibroblast Growth Factor; D043562:Receptors, G-Protein-Coupled; D013912:Threonine; D014443:Tyrosine; D012694:Serine; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases