Factors regulating insulin-like growth factor-binding protein-3 binding, processing, and potentiation of insulin-like growth factor action

Cheryl A Conover, Jay T. Clarkson, Laurie K. Bale

Research output: Contribution to journalArticle

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Abstract

In this study, we investigated the effects of various biochemical and pharmacological agents on insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) cell binding and action in cultured bovine fibroblasts. When cells were preincubated for 48 h with 50 nM recombinant human (rhIGFBP-3, IGF-I- stimulated [3H]aminoisobutyric acid ([125H]AIB) uptake was enhanced 2- to 3-fold. The addition of cytoskeletal disrupting agents during the preincubation with rhIGFBP-3 did not affect IGFBP-3 potentiation of IGF-I action, nor did a variety of serine, aspartate, and metalloproteinase inhibitors. On the other hand, ammonium chloride and chloroquine, weak bases that neutralize the pH of acidic cell compartments, blocked IGFBP-3 potentiation of IGF-I-stimulated [3H]AIB uptake. Chloroquine and ammonium chloride had no effect alone and did Bafilomycin A, a specific inhibitor of ATP-dependent hydrogen ion pumps, also inhibited IGFBP-3 potentiation of IGF- I-stimulated [3H]AIB uptake. Competitive [125I]IGF-I binding and affinity cross-linking experiments suggested structure/function changes in cell-bound IGFBP-3 that were altered in the presence of chloroquine and bafilomycin. Heparin markedly decreased initial IGFBP-3 cell adherence, but could not promote dissociation of IGFBP-3 from cells after the 48-h preincubation. Moreover, heparin did not inhibit IGFBP-3 potentiation of IGF-I action. In summary, these data indicate that IGFBP-3 under goes specific pH-dependent structural and/or environmental modifications that mediate the enhancing effect of IGFBP-3 on IGF-I action in bovine fibroblasts. They also suggest that IGFBP-3 binding to heparinlike molecules on the cell surface is not directly involved in this process.

Original languageEnglish (US)
Pages (from-to)2286-2292
Number of pages7
JournalEndocrinology
Volume137
Issue number6
DOIs
StatePublished - 1996

Fingerprint

Insulin-Like Growth Factor Binding Protein 3
Somatomedins
Protein Binding
Insulin-Like Growth Factor I
Chloroquine
Ammonium Chloride
Heparin
Fibroblasts
Ion Pumps
Aminoisobutyric Acids
Metalloproteases
Aspartic Acid
Serine
Protons
Adenosine Triphosphate
Pharmacology

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Factors regulating insulin-like growth factor-binding protein-3 binding, processing, and potentiation of insulin-like growth factor action. / Conover, Cheryl A; Clarkson, Jay T.; Bale, Laurie K.

In: Endocrinology, Vol. 137, No. 6, 1996, p. 2286-2292.

Research output: Contribution to journalArticle

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