title: Association of a 85-kDa serine kinase with activated fibroblast growth factor receptor-4.
abstract: Fibroblast growth factors (FGFs) transduce a variety of biological signals via four distinct tyrosine kinase receptors. We have characterized the phosphorylation of FGF receptor 4 (FGFR-4) and its association with a putative substrate, p85, using transfected L6 myoblast and NIH3T3 fibroblast cell lines. FGFR-4 was phosphorylated in vivo and in vitro mainly on serine and threonine residues in several peptides and to a lower degree on tyrosine residues. When analyzed further by in-gel kinase assay, immunoprecipitates of ligand-activated FGFR-4 contained a serine autophosphorylated polypeptide doublet of 85 kDa. Analysis of the major autophosphorylation site Y754F mutant of FGFR-4 showed that binding of p85 and its serine phosphorylation were independent of receptor autophosphorylation at this site. Okadaic acid treatment increased the basal autophosphorylation activity of p85 but decreased FGFR-4 tyrosine phosphorylation. In contrast, orthovanadate treatment increased the tyrosine phosphorylation of FGFR-4. These data show that a serine kinase is associated with activated FGFR-4 and suggest a role for serine phosphorylation in FGFR-4 function.
authors.affiliation: Molecular/Cancer Biology Laboratory, Haartman Institute, University of Helsinki, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Vainikka
authors.forename: V
authors.initials: V
authors.lastname: Joukov
authors.forename: P
authors.initials: P
authors.lastname: Klint
authors.forename: K
authors.initials: K
authors.lastname: Alitalo
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D009132:Muscles; D016297:Mutagenesis, Site-Directed; D019319:Okadaic Acid; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry / Q000302:isolation & purification; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D051499:Receptor, Fibroblast Growth Factor, Type 4; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013379:Substrate Specificity; D014162:Transfection; D014357:Trypsin; D014638:Vanadates / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D004988:Ethers, Cyclic; D010748:Phosphopeptides; D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; D019319:Okadaic Acid; D014638:Vanadates; D005346:Fibroblast Growth Factors; C496372:Fgfr4 protein, mouse; C496373:Fgfr4 protein, rat; D051499:Receptor, Fibroblast Growth Factor, Type 4; D017346:Protein Serine-Threonine Kinases; D014357:Trypsin