The 16-kDa proteolytic fragment of insulin-like growth factor (IGF) binding protein-3 inhibits the mitogenic action of fibroblast growth factor on mouse fibroblasts with a targeted disruption of the type 1 IGF receptor gene.
We previously reported that a 16-kDa proteolytic fragment of IGF Binding Protein-3 (IGFBP-3), which is devoid of affinity for IGFs, inhibits the mitogenic effects of IGF-I on chick embryo fibroblasts. Here, we set out to determine if the fragment had biological effects on fibroblasts from mouse embryos homozygous for a targeted disruption of the Type 1 IGF receptor gene. In the cell clone used, bFGF (but not IGF, EGF or PDGF) was mitogenic in serum-free medium, increasing 14C-thymidine uptake by a factor of 10-15 within 24 hours and doubling cell proliferation. The 16-kDa fragment, isolated by HPLC following limited proteolysis of recombinant human (rh) IGFBP-3 by plasmin, in both assays dose-dependently (20 to 100 ng/ml) inhibited (up to 100%) maximal stimulation induced by 25 ng/ml bFGF, whereas intact IGFBP-3 had virtually no effect. Similar results were obtained with control wild-type cells. In the latter, the mitogenic activity of 1% fetal calf serum (equal to that of 25 ng/ml bFGF) was inhibited by only 25-30% by 100 ng/ml 16-kDa fragment or 200 ng/ml rhIGFBP-3. This agrees with an antagonistic action, affecting the mitogenic activity of serum that is attributable to IGFs. The 16-kDa IGFBP-3 fragment therefore appears to be a potent inhibitor of mitogenic signals resulting from activation of both the type 1 IGF and FGF receptors.
Zadeh
S M
SM
Unité de Recherches sur la Régulation de la Croissance, U.142, Institut National de la Santé et de la Recherche Médicale, Hôpital Saint Antoine, Paris, France.
Binoux
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D000818:Animals; D002478:Cells, Cultured; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000037:antagonists & inhibitors*; D005347:Fibroblasts / Q000187:drug effects; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000494:pharmacology*; D051379:Mice; D008970:Molecular Weight; D010446:Peptide Fragments / Q000494:pharmacology*; D017526:Receptor, IGF Type 1 / Q000235:genetics*; D013936:Thymidine / Q000378:metabolism
D018972:Insulin-Like Growth Factor Binding Protein 3; D010446:Peptide Fragments; D016222:Fibroblast Growth Factor 2; D005346:Fibroblast Growth Factors; D017526:Receptor, IGF Type 1; D013936:Thymidine