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Characterization of Insulin‐Like Growth Factor‐I Receptors in PC 12 Pheochromocytoma Cells and Bovine Adrenal Medulla
Author(s) -
Dahmer Mary K.,
Ji Li,
Perlman Robert L.
Publication year - 1989
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1989.tb07392.x
Subject(s) - autophosphorylation , receptor , adrenal medulla , insulin receptor , insulin like growth factor , medicine , endocrinology , insulin receptor substrate , biology , phosphorylation , pelp 1 , wheat germ agglutinin , chromaffin cell , insulin , growth factor , biochemistry , chemistry , protein kinase a , lectin , catecholamine , gene , insulin resistance , nuclear receptor , transcription factor
Competitive binding studies indicated that PC 12 cells have receptors for insulin‐like growth factor‐I (IGF‐I). There are ∼ 11,100 ± 1,500 IGF‐I receptors/cell; these receptors have an apparent K D for IGF‐I of 7.2 ± 0.6 n M. Covalent cross‐linking of l25 I‐IGF‐I to PC 12 cells labeled a 125,000‐130,000‐M r protein, presumably the α‐subunit of the IGF‐I receptor. Although PC 12 cells also have insulin receptors, the 125 I‐IGF‐I appeared to be cross‐linked to IGF‐I receptors, because 100 n M IGF‐I competed for labeling but 100 n M 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 PC 12 cells was examined after purification of the receptors by wheat germ agglutinin‐Sepharose chromatography. IGF‐I (10 n M ) stimulated autophosphorylation of the β‐subunits of the IGF‐I receptors from both preparations; the β‐subunits from both sources had M r values of ∼97,000. IGF‐I also stimulated phosphorylation of the synthetic substrate poly(Glu:Tyr)4:1 by both receptor preparations. IGF‐I (IC 50 of ∼0.2 n M ) 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 n M ) increased phosphorylation approximately threefold. IGF‐I was slightly more effective than insulin at stimulating the phosphorylation of poly(Glu:Tyr) by the PC 12 cell receptor preparation, but neither ligand produced a maximal effect at concentrations up to 100 n M. This result probably reflects the presence of comparable numbers of IGF‐I and insulin receptors on PCI 2 cells. Our data indicate that the IGF‐I receptors on PC 12 cells are similar to IGF‐I receptors in the adrenal medulla and other tissues. Presumably these receptors are responsible for the stimulation of PC 12 cell replication by IGF‐I.