Insulin-Like Growth Factor-I (IGF-I) Attenuation of Growth Hormone Is Enhanced by Overexpression of Pituitary IGF-I Receptors
| Autor: | Shlomo Melmed, Diane Prager, Saba Gebremedhin, Hironori Yamasaki |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
medicine.medical_treatment
Gene Expression Receptors Cell Surface Biology Transfection Cell Line Insulin-like growth factor Endocrinology medicine Animals Cloning Molecular Insulin-Like Growth Factor I Receptor Molecular Biology Growth factor Receptors Somatomedin DNA General Medicine Molecular biology Growth hormone secretion Rats Blotting Southern Kinetics Somatropin Cell culture Growth Hormone Pituitary Gland Signal transduction Plasmids Signal Transduction |
| Zdroj: | Molecular Endocrinology. 5:890-896 |
| ISSN: | 1944-9917 0888-8809 |
| Popis: | Insulin-like growth factor-I (IGF-I) attenuates GH gene expression by a receptor-mediated mechanism in pituitary cells. We, therefore, isolated neomycin-resistant stable GC cell transfectants over-expressing human IGF-I receptor cDNA (IGFIR-cDNA) cloned in an Rous sarcoma virus-directed expression vector. A transfection control contained the IGFIR-cDNA cloned in the reverse orientation. Southern analysis confirmed incorporation of human IGFIR-cDNA sequences into rat genomic DNA. Immunoprecipitation of metabolically labeled [35S]methionine stably transfected cells revealed a 200-kDa human IGF-I receptor precursor protein. Growth rate and basal GH secretion were not altered in transfected cells. Although transfected and control cells had a similar Kd for IGF-I binding (0.43 and 0.40 nM, respectively), IGF-I-binding sites were induced 17-fold (384,000 vs. 22,000 sites/cell). Treatment of cells with IGF-I (6.5 nM) maximally attenuated GH secretion by 80% compared to 40% attenuation in control cells (P less than 0.0001). Maximal suppression of GH in transfectants occurred within 15 h of treatment, and GH secretion by control cells was only maximally suppressed after 42 h. The ED50 of IGF-I suppression of GH secretion in transfectants after 15 h was 0.5 nM. These results demonstrate that transfectants overexpressing human IGF-I receptor are hyperresponsive to exogenous IGF-I. These data indicate that IGF-I receptor number plays an important role in mediating the signal transduction of IGF-I to the GH gene. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|