The insulin-like growth factor 1 (IGF-1) receptor is responsible for mediating the effects of insulin, IGF-1, and IGF-2 in Xenopus laevis oocytes

• Published in: The Journal of biological chemistry Vol. 266; no. 15; pp. 9382 - 9391
• Main Authors: JANICOT, M, FLORES-RIVEROS, J. R, LANE, M. D
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 25.05.1991
• Subjects: Animals; Binding, Competitive; Biological and medical sciences; Cell receptors; Cell structures and functions; Chromatography, High Pressure Liquid; Deoxyglucose - metabolism; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Hexoses - metabolism; Hormone receptors. Growth factor receptors. Cytokine receptors. Prostaglandin receptors; insulin; insulin-growth factor II; insulin-like growth factor I; Insulin-Like Growth Factor I - metabolism; Insulin-Like Growth Factor II - metabolism; Kinetics; Molecular and cellular biology; oocytes; Oocytes - metabolism; Peptide Mapping; Phosphorylation; Protein-Tyrosine Kinases - metabolism; Receptors, Cell Surface - metabolism; Receptors, Somatomedin; Trypsin; Xenopus laevis; Autophosphorylation; Ligand binding; Somatomedin C; Xenopus laevis; Amphibia; HPLC chromatography; Homology; Salientia; Binding site; Insulin; Competitive fixation; Vertebrata; Protein kinase; Scatchard plot; Growth factor; Hormonal receptor
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)92830-9

Competitive hormone binding studies with membrane and partially purified receptors from Xenopus laevis oocytes revealed that the oocyte possesses high affinity (KD = 1-3 nM) binding sites for both insulin growth factors 1 and 2 (IGF-1 and IGF-2), but not for insulin. Consistent with these findings, IGF-1 activates hexose uptake by Xenopus oocytes with a KA (3 nM) identical with its KD, while IGF-2 and insulin activate hexose uptake with KA values of 50 nM and 200-250 nM, respectively, suggesting activation mediated through an IGF-1 receptor. Both IGF-1 and insulin activate receptor beta-subunit autophosphorylation and, thereby, protein substrate (reduced and carboxyamidomethylated lysozyme, i.e. RCAM-lysozyme) phosphorylation with KA values comparable to their respective KD values for ligand binding and KA values for activation of hexose uptake. The autophosphorylated beta-subunit(s) of the receptor were resolved into two discrete components, beta 1 and beta 2 (108 kDa and 94 kDa, respectively), which were phosphorylated exclusively on tyrosine and which exhibited similar extents of IGF-1-activated autophosphorylation. When added prior to autophosphorylation, RCAM-lysozyme blocks IGF-1-activated autophosphorylation and, thereby, IGF-1-activated protein substrate (RCAM-lysozyme) phosphorylation. Based on these findings, we conclude that IGF-1-stimulated autophosphorylation of its receptor is a prerequisite for catalysis of protein substrate phosphorylation by the receptor's tyrosine-specific protein kinase. The IGF-1 receptor kinase is implicated in signal transmission from the receptor, since anti-tyrosine kinase domain antibody blocks IGF-1-stimulated kinase activity in vitro and, when microinjected into intact oocytes, prevents IGF-1-stimulated hexose uptake.