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Titolo:
Mechanisms of insulin-like growth factor I augmentation of follicle-stimulating hormone-induced porcine steroidogenic acute regulatory protein gene promoter activity in granulosa cells
Autore:
LaVoie, HA; Garmey, JC; Veldhuis, JD;
Indirizzi:
Univille,inia, Dept Internal Med, Ctr Hlth Sci, Div Endocrinol, Charlottesv Univ Virginia Charlottesville VA USA 22908 i, Div Endocrinol, Charlottesv Univ Maine, Dept Sci Biol, Orono, ME 04469 USA Univ Maine Orono ME USA 04469 v Maine, Dept Sci Biol, Orono, ME 04469 USA
Titolo Testata:
ENDOCRINOLOGY
fascicolo: 1, volume: 140, anno: 1999,
pagine: 146 - 153
SICI:
0013-7227(199901)140:1<146:MOIGFI>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
MESSENGER-RIBONUCLEIC-ACID; SOMATOMEDIN-C; AROMATASE-ACTIVITY; BINDING PROTEIN; STAR GENE; EXPRESSION; AMPLIFIER; DIFFERENTIATION; RESPONSIVENESS; GONADOTROPINS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Veldhuis, JD Univarlottesville,t Internal Med, Ctr Hlth Sci, Div Endocrinol, Box 202, Ch Univ Virginia Box 202 Charlottesville VA USA 22908 ox 202, Ch
Citazione:
H.A. LaVoie et al., "Mechanisms of insulin-like growth factor I augmentation of follicle-stimulating hormone-induced porcine steroidogenic acute regulatory protein gene promoter activity in granulosa cells", ENDOCRINOL, 140(1), 1999, pp. 146-153

Abstract

Insulin-like growth factor I(IGF-I) and the gonadotropin, FSH, can synergize to stimulate progesterone production in primary cultures of maturing human, rat, and pig granulosa cells. These trophic hormones act by increasing the activity and production of proteins and their gene transcripts essential to sterol uptake, delivery, and utilization in steroidogenesis. We previously observed that FSH and IGF-I interact synergistically to promote the accumulation of steroidogenic acute regulatory protein (StAR) messenger RNA and protein in granulosa cells. Here we investigate potential mechanisms of IGF-I synergy with FSH and the protein kinase A (PKA) pathway in activatingthe porcine StAR gene promoter. To this end, we first cloned 1423 bp of the porcine StAR promoter upstream of the transcriptional start site using PCR and created 5'-deletional constructs coupled to a cytoplasmically targeted firefly luciferase reporter gene. FSH, 8-bromo-cAMP, and transient transfection of the protein kinase A (PKA) catalytic subunit (driven by the Rous sarcoma virus promoter) were used to activate the PKA effector pathway. Allthree agonists alone stimulated StAR promoter-driven luciferase activity in primary cultures of granulosa cells after 4-h treatment. IGF-I significantly augmented PRE pathway agonist activation of the the StAR promoter, whereas IGF-I had no effect alone. Binding experiments with I-125-labeled ovineFSH-20 in IGF-I(100 ng/ml)-treated granulosa cells showed that FSH bindingaffinity and receptor number were unchanged by IGF-I treatment. However, IGF-I augmented FSH-stimulated, but not forskolin-stimulated, cAMP accumulation. Analysis of 5'-deletion constructs of the StAR promoter revealed threeregions of stimulatory activity within the - 139-bp fragment upstream of the transcriptional start site as well as another potentially inhibitory region upstream(-1115 to -905). Elimination of the putative SF-l site (-48 to -41)virtually abolished StAR promoter responsiveness. In summary, our data indicate that IGF-I can act via two post FSH-binding mechanisms to augment FSH/PKA pathway-mediated StAR gene promoter transactivation: at the level of cAMP accumulation and distal to cAMP production and PKA activation.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/09/20 alle ore 06:12:54