title: Mammalian Sprouty4 suppresses Ras-independent ERK activation by binding to Raf1.
abstract: The signalling cascade including Raf, mitogen-activated protein kinase (MAPK) kinase and extracellular-signal-regulated kinase (ERK) is important in many facets of cellular regulation. Raf is activated through both Ras-dependent and Ras-independent mechanisms, but the regulatory mechanisms of Raf activation remain unclear. Two families of membrane-bound molecules, Sprouty and Sprouty-related EVH1-domain-containing protein (Spred) have been identified and characterized as negative regulators of growth-factor-induced ERK activation. But the molecular functions of mammalian Sproutys have not been clarified. Here we show that mammalian Sprouty4 suppresses vascular epithelial growth factor (VEGF)-induced, Ras-independent activation of Raf1 but does not affect epidermal growth factor (EGF)-induced, Ras-dependent activation of Raf1. Sprouty4 binds to Raf1 through its carboxy-terminal cysteine-rich domain, and this binding is necessary for the inhibitory activity of Sprouty4. In addition, Sprouty4 mutants of the amino-terminal region containing the conserved tyrosine residue, which is necessary for suppressing fibroblast growth factor signalling, still inhibit the VEGF-induced ERK pathway. Our results show that receptor tyrosine kinases use distinct pathways for Raf and ERK activation and that Sprouty4 differentially regulates these pathways.
authors.affiliation: Division of Molecular and Cellular Immunology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Atsuo
authors.initials: A
authors.lastname: Sasaki
authors.forename: Takaharu
authors.initials: T
authors.lastname: Taketomi
authors.forename: Reiko
authors.initials: R
authors.lastname: Kato
authors.forename: Kazuko
authors.initials: K
authors.lastname: Saeki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nonami
authors.forename: Mika
authors.initials: M
authors.lastname: Sasaki
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Kuriyama
authors.forename: Naoaki
authors.initials: N
authors.lastname: Saito
authors.forename: Masabumi
authors.initials: M
authors.lastname: Shibuya
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshimura
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000378:metabolism / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology; D005057:Eukaryotic Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000378:metabolism / Q000494:pharmacology; D006133:Growth Substances / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008222:Lymphokines / Q000378:metabolism / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D016228:Endothelial Growth Factors; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008222:Lymphokines; D009419:Nerve Tissue Proteins; C499038:SPRY4 protein, human; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D020794:Receptor Protein-Tyrosine Kinases; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins