Expression of a type I insulin-like growth factor receptor with low affinity for insulin-like growth factor II

E. L. Germain-Lee, M. Janicot, R. Lammers, A. Ullrich, S. J. Casella

Research output: Contribution to journalArticle

Abstract

We investigated the binding properties of the type I insulin-like growth factor (IGF) receptor expressed in NIH-3T3 fibroblasts transfected with a human type I receptor cDNA. Cell surface receptors bound IGF-I with K(D) = 1 nM as predicted. Although recent studies have suggested that IGF-I and IGF-II bind to type I receptors with near-equal affinity, the receptors in this system bound IGF-II with much lower affinity (K(D)) = 15-20 nM). When type I receptors from the transfected cells were solubilized and immunopurified, however, both 125I-1GF-I and 125I-1GF-II bound to the purified receptors with extremely high and relatively similar affinities (K(D) = 8 and 17 pM respectively). Thus the immunopurified receptors had higher affinity but lower specificity for the two ligands. The monoclonal antibody αIR-3 effectively inhibited IGF-I binding to cell surface receptors (75±10 %), but did not inhibit IGF-II binding. In the purified receptor assay, αIR-3 also inhibited IGF-I binding more effectively than IGF-II binding (38±7 % versus 10±4 %). We conclude that the products of this cDNA can account for the binding patterns that we previously observed in receptors immunopurified from human placenta. The differential effect of αIR-3 on IGF-I versus IGF-II raises the possibility that these homologous growth factors bind to immunologically distinct epitopes on the type I receptor.

Original languageEnglish (US)
Pages (from-to)413-417
Number of pages5
JournalBiochemical Journal
Volume281
Issue number2
StatePublished - 1992

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IGF Type 1 Receptor
Insulin-Like Growth Factor II
Insulin-Like Growth Factor I
Cell Surface Receptors
Complementary DNA
Fibroblasts
Placenta
Epitopes
Assays
Intercellular Signaling Peptides and Proteins
Monoclonal Antibodies
Ligands

ASJC Scopus subject areas

  • Biochemistry

Cite this

Germain-Lee, E. L., Janicot, M., Lammers, R., Ullrich, A., & Casella, S. J. (1992). Expression of a type I insulin-like growth factor receptor with low affinity for insulin-like growth factor II. Biochemical Journal, 281(2), 413-417.

Expression of a type I insulin-like growth factor receptor with low affinity for insulin-like growth factor II. / Germain-Lee, E. L.; Janicot, M.; Lammers, R.; Ullrich, A.; Casella, S. J.

In: Biochemical Journal, Vol. 281, No. 2, 1992, p. 413-417.

Research output: Contribution to journalArticle

Germain-Lee, EL, Janicot, M, Lammers, R, Ullrich, A & Casella, SJ 1992, 'Expression of a type I insulin-like growth factor receptor with low affinity for insulin-like growth factor II', Biochemical Journal, vol. 281, no. 2, pp. 413-417.
Germain-Lee, E. L. ; Janicot, M. ; Lammers, R. ; Ullrich, A. ; Casella, S. J. / Expression of a type I insulin-like growth factor receptor with low affinity for insulin-like growth factor II. In: Biochemical Journal. 1992 ; Vol. 281, No. 2. pp. 413-417.
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