title: Characterization of insulin-like growth factor-I receptors in PC12 pheochromocytoma cells and bovine adrenal medulla.
abstract: Competitive binding studies indicated that PC12 cells have receptors for insulin-like growth factor-I (IGF-I). There are approximately 11,000 +/- 1,500 IGF-I receptors/cell; these receptors have an apparent KD for IGF-I of 7.2 +/- 0.6 nM. Covalent cross-linking of 125I-IGF-I to PC12 cells labeled a 125,000-130,000-Mr protein, presumably the alpha-subunit of the IGF-I receptor. Although PC12 cells also have insulin receptors, the 125I-IGF-I appeared to be cross-linked to IGF-I receptors, because 100 nM IGF-I competed for labeling but 100 nM insulin did not. Bovine chromaffin cells also have IGF-I receptors. The protein tyrosyl kinase activity of IGF-I receptors from bovine adrenal medulla and PC12 cells was examined after purification of the receptors by wheat germ agglutinin-Sepharose chromatography. IGF-I (10 nM) stimulated autophosphorylation of the beta-subunits of the IGF-I receptors from both preparations; the beta-subunits from both sources had Mr values of approximately 97,000. IGF-I also stimulated phosphorylation of the synthetic substrate poly(Glu:Tyr)4:1 by both receptor preparations. IGF-I (IC50 of approximately 0.2 nM) was much more potent than insulin at stimulating phosphorylation of poly(Glu:Tyr) by the bovine adrenal medulla preparation. A maximal concentration of IGF-I (10 nM) increased phosphorylation approximately threefold. IGF-I was slightly more effective than insulin at stimulating the phosphorylation of poly(Glu:Tyr) by the PC12 cell receptor preparation, but neither ligand produced a maximal effect at concentrations up to 100 nM. This result probably reflects the presence of comparable numbers of IGF-I and insulin receptors on PC12 cells.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, University of Chicago, Illinois 60637.
authors.forename: M K
authors.initials: MK
authors.lastname: Dahmer
authors.forename: L
authors.initials: L
authors.lastname: Ji
authors.forename: R L
authors.initials: RL
authors.lastname: Perlman
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000378:metabolism*; D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D010673:Pheochromocytoma / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I