Insulin-like growth factor receptor-1 stimulates phosphorylation of the beta2-adrenergic receptor in vivo on sites distinct from those phosphorylated in response to insulin.
G-protein-linked receptors have been shown to be substrates for growth factor receptors with intrinsic tyrosine kinase activity typified by the ability of insulin to both phosphorylate tyrosyl residues in the C terminus of and to counter-regulate the action of the beta2-adrenergic receptor (Karoor, V., Baltensperger, K., Paul, H., Czech, M. P., and Malbon, C. C. (1995) J. Biol. Chem. 270, 25305-25308). Insulin-like growth factor-1 (IGF-1), another member of the growth factor family operating via receptors with intrinsic tyrosine kinase, is shown in the present work to stimulate in vivo the phosphorylation of the beta2-adrenergic receptor. Analysis of tryptic digests prepared from phosphorylated beta2-adrenergic receptors of IGF-1-treated, metabolically labeled smooth muscle cells was performed using reversed-phase high performance liquid chromatography, two-dimensional peptide mapping, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results of these separate analyses reveal that IGF-1 stimulates phosphorylation predominantly on tyrosyl residues Y132/141 of the second intracellular loop of the beta2-adrenergic receptor rather than the C-terminal region targeted by the activated insulin receptor (Y350/354, Y364), although both growth factors block beta-adrenergic agonist action. These data demonstrate selective phosphorylation of a G-protein-linked receptor by receptor tyrosine kinases for insulin and IGF-1 mapping to spatially distinct regions of this heptihelical membrane receptor.
Karoor
V
V
Department of Molecular Pharmacology, Diabetes and Metabolic Diseases Research Center, School of Medicine, State University of New York, Stony Brook, New York 11794-8651, USA.
Malbon
C C
CC
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D007328:Insulin / Q000378:metabolism*; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D010449:Peptide Mapping; D010766:Phosphorylation; D018343:Receptors, Adrenergic, beta-2 / Q000737:chemistry / Q000378:metabolism*; D017451:Receptors, Somatomedin / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014357:Trypsin
D007328:Insulin; D018343:Receptors, Adrenergic, beta-2; D017451:Receptors, Somatomedin; D014357:Trypsin