title: 14-3-3 binding to the IGF-1 receptor is mediated by serine autophosphorylation.
abstract: The phosphoserine-binding 14-3-3 proteins have been implicated in playing a role in mitogenic and apoptotic signaling pathways. Binding of 14-3-3 proteins to phosphoserine residues in the C-terminus of the insulin-like growth factor-1 receptor (IGF-1R) has been described to occur in a variety of cell systems, but the kinase responsible for this serine phosphorylation has not been identified yet. Here we present evidence that the isolated dimeric insulin-like growth factor-1 receptor kinase domain (IGFKD) contains a dual specific (i.e. tyrosine/serine) kinase activity that mediates autophosphorylation of C-terminal serine residues in the enzyme. From the total phosphate incorporation of approximately 4 mol per mol kinase subunit, 1 mol accounts for serine phosphate. However, tyrosine autophosphorylation proceeds more rapidly than autophosphorylation of serine residues (t(1/2) approximately 1 min vs. t(1/2) approximately 5 min). Moreover, dot-blot and far-Western analyses reveal that serine autophosphorylation of IGFKD is sufficient to promote binding of 14-3-3 proteins in vitro. The proof that dual kinase activity of IGFKD is necessary and sufficient for 14-3-3 binding was obtained with an inactive kinase mutant that was phosphorylated on serine residues in a stoichiometric reaction with the catalytically active enzyme. Thus, the IGF-1R itself might be responsible for the serine autophosphorylation which leads to recognition of 14-3-3 proteins in vivo.
authors.affiliation: Institute of Biochemistry, University of Cologne, Otto-Fischer-Str. 12-14, 50674, Cologne, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Parvaresch
authors.forename: Tanju
authors.initials: T
authors.lastname: Yesilkaya
authors.forename: Kristin
authors.initials: K
authors.lastname: Baer
authors.forename: Hadi
authors.initials: H
authors.lastname: Al-Hasani
authors.forename: Helmut W
authors.initials: HW
authors.lastname: Klein
mesh_terms: D048948:14-3-3 Proteins; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002384:Catalysis; D002460:Cell Line; D019281:Dimerization; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007313:Insecta; D007700:Kinetics; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D000596:Amino Acids; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012694:Serine; D014446:Tyrosine 3-Monooxygenase; D005982:Glutathione Transferase; D017526:Receptor, IGF Type 1