Platelet-derived growth factor isoforms decrease insulin-like growth factor I gene expression in rat vascular smooth muscle cells and selectively stimulate the biosynthesis of insulin-like growth factor binding protein 4
| Autor: | Ron G. Rosenfeld, Joel Kupfer, James S. Forrester, Behrooz G. Sharifi, Amin Kamyar, Daniel Giannella-Neto, James A. Fagin, Carlos José Pirola |
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| Rok vydání: | 1992 |
| Předmět: |
Male
medicine.medical_specialty Platelet-derived growth factor Vascular smooth muscle Physiology medicine.medical_treatment Gene Expression Mitosis Insulin-like growth factor-binding protein Muscle Smooth Vascular chemistry.chemical_compound Insulin-like growth factor Internal medicine Gene expression medicine Animals RNA Messenger Insulin-Like Growth Factor I Cells Cultured Platelet-Derived Growth Factor biology Growth factor Binding protein Rats Inbred Strains Cell biology Rats Insulin-Like Growth Factor Binding Proteins Endocrinology chemistry biology.protein Cardiology and Cardiovascular Medicine Carrier Proteins Platelet-derived growth factor receptor |
| Zdroj: | Circulation research. 71(3) |
| ISSN: | 0009-7330 |
| Popis: | Platelet-derived growth factor (PDGF) is believed to be a critical mediator of vascular smooth muscle cell (SMC) proliferation. Because insulin-like growth factor (IGF) I (IGF-I) functions as a progression factor for the mitogenic effects of PDGF, we hypothesized that IGF-I gene expression and the production of IGF binding proteins (IGFBPs) by cultured rat aortic SMCs might be regulated by one or more of the three isoforms of PDGF: PDGF-AA, -BB, and -AB. IGF-I gene expression was highly dependent on cell density: IGF-I mRNA transcripts decreased markedly as a function of cell confluence. IGF-I mRNA content was inhibited to a similar degree by PDGF-AA, -BB, and -AB through a mechanism requiring protein synthesis. The inhibition was readily apparent at 4 hours, reaching approximately 25% of control levels after 24 hours. Radioimmunoassayable IGF-I was only barely detectable in SMC-conditioned serum-free medium and not significantly modulated by PDGF. Western ligand blot revealed that vascular SMCs release 30-kd and 24-kd IGFBP into serum-free conditioned medium. PDGF isoforms did not significantly alter release of the 30-kd IGFBP but evoked a fivefold to sixfold increase in the 24-kd IGFBP. The 24-kd IGFBP was found to comigrate with IGFBP-4, a recently identified binding protein that inhibits IGF action. The 30-kd protein was not merely a glycosylated form of IGFBP-4, because it was not sensitive to N-glycanase digestion. PDGF-AA, -BB, and -AB markedly induced expression of IGFBP-4 mRNA in a time- and concentration-dependent fashion. Vascular SMCs also express IGFBP-2 mRNA, but its abundance was not induced by PDGF. In conclusion, PDGF evokes a complex pattern of regulation of genes in the IGF/IGFBP system. By inhibiting IGF-I production and specifically inducing biosynthesis of the inhibitory binding protein IGFBP-4, PDGF may set in motion mechanisms to limit the final magnitude of the mitogenic response. |
| Databáze: | OpenAIRE |
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