title: The beta-adrenergic receptor is a substrate for the insulin receptor tyrosine kinase.
abstract: G-protein-linked receptors and intrinsic tyrosine-kinase growth receptors represent two prominent modalities in cell signaling. Cross-regulation among members of both receptor superfamilies has been reported, including the counter-regulatory effects of insulin on beta-adrenergic catecholamine action. Cells stimulated by insulin show loss of function and increased phosphotyrosine content of beta 2-adrenergic receptors. Phosphorylation of tyrosyl residues 350/354 of beta 2-adrenergic receptors is obligatory for counter-regulation by insulin (Karoor, V., Baltensperger, K., Paul, H., Czech, M., and Malbon, C. C. (1995) J. Biol. Chem. 270, 25305-25308), suggesting the hypothesis that G-protein-linked receptors themselves may act as substrates for the insulin receptor and other growth factor receptors. This hypothesis was evaluated directly using recombinant human insulin receptor, hamster beta 2-adrenergic receptor, and an vitro reconstitution and phosphorylation assay. Insulin is shown to stimulate insulin receptor-catalyzed phosphorylation of the beta 2-adrenergic receptor. Phosphoamino acid analysis establishes that insulin receptor-catalyzed phosphorylation of the beta 2-adrenergic receptor in vitro is confined to phosphotyrosine. High pressure liquid chromatography and two-dimensional mapping reveal insulin receptor-catalyzed phosphorylation of the beta 2-adrenergic receptor at residues Tyr132/Tyr141, Tyr350/Tyr354, and Tyr364, known sites of phosphorylation in response to insulin in vivo. Insulin-like growth factor-I receptor as well as the insulin receptor displays the capacity to phosphorylate the beta 2-adrenergic receptor in vitro, establishing a new paradigm, i.e. G-protein-linked receptors acting as substrates for intrinsic tyrosine kinase growth factor receptors.
authors.affiliation: Program in Molecular Medicine and the Department of Biochemistry and Molecular Biology, University of Massachusetts Medical Center, Worcester, 01605, USA.
authors.forename: K
authors.initials: K
authors.lastname: Baltensperger
authors.forename: V
authors.initials: V
authors.lastname: Karoor
authors.forename: H
authors.initials: H
authors.lastname: Paul
authors.forename: A
authors.initials: A
authors.lastname: Ruoho
authors.forename: M P
authors.initials: MP
authors.lastname: Czech
authors.forename: C C
authors.initials: CC
authors.lastname: Malbon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D018343:Receptors, Adrenergic, beta-2; D011994:Recombinant Proteins; D020794:Receptor Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; D019204:GTP-Binding Proteins