Structural and biological characterization of bovine insulin-like growth factor binding protein-3

Cheryl A Conover, M. Ronk, F. Lombana, D. R. Powell

Research output: Contribution to journalArticle

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Abstract

Insulin-like growth factor binding protein-3 (IGFBP-3) purified from bovine serum shares 19 of 25 amino-terminal amino acid residues with IGFBP-3 purified from human, rat, and procine sources. A newly characterized bovine fibroblast model was used to investigate the biological effects of purified bovine IGFBP-3 (bIGFBP-3). Coincubation of insulin-like growth factor I (IGF-I) with increasing concentrations of bIGFBP-3 produced a dose-dependent inhibition of IGF-I-stimulated [3H]aminoisobutyric acid (AIB) uptake in cultured bovine fibroblasts. Inhibition was complete at equimolar concentrations of IGF-I and bIGFBP-3. Inhibition of IGF-I-stimulated [3H]AIB uptake paralleled the ability of bIGFBP-3 to prevent [125I]IGF-I cell surface binding. In contrast, preincubation with bIGFBP-3 resulted in a dose-dependent enhancement of IGF-I-stimulated [3H]AIB uptake; a 32-86% increase in IGF-I bioactivity was seen after a 24 h preexposure to 10 nM bIGFBP-3, and a 2- to 6-fold potentiation was seen after a 72 h preincubation. Preincubation with bIGFBP-3 increased both the sensitivity and maximal responsiveness of the cells to IGF-I. The potentiating effects of bIGFBP-3 were associated with increased [125I]IGF-I binding to cultured bovine fibroblasts. Affinity cross-linking experiments indicated that the increase in IGF-I binding was due to increased membrane-associated bIGFBP-3 rather than to a bIGFBP-3-induced increase in type I IGF receptors. bIGFBP-3 had no effect on insulin stimulation of [3H]AIB uptake under either experimental condition. These data suggest that soluble bIGFBP-3 inhibits IGF-I action by sequestering and preventing IGF-I receptor binding, whereas surface-associated bIGFBP-3 enhances the growth-promoting effects of IGF-I in bovine fibroblasts. We propose that IGFBP-3 serves a dual function in modulating IGF action in vivo.

Original languageEnglish (US)
Pages (from-to)2795-2803
Number of pages9
JournalEndocrinology
Volume127
Issue number6
StatePublished - 1990

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Insulin-Like Growth Factor Binding Protein 3
Insulin-Like Growth Factor I
Aminoisobutyric Acids
Fibroblasts
IGF Type 1 Receptor

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Structural and biological characterization of bovine insulin-like growth factor binding protein-3. / Conover, Cheryl A; Ronk, M.; Lombana, F.; Powell, D. R.

In: Endocrinology, Vol. 127, No. 6, 1990, p. 2795-2803.

Research output: Contribution to journalArticle

Conover, Cheryl A ; Ronk, M. ; Lombana, F. ; Powell, D. R. / Structural and biological characterization of bovine insulin-like growth factor binding protein-3. In: Endocrinology. 1990 ; Vol. 127, No. 6. pp. 2795-2803.
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