Regulated expression of sterol carrier protein 2 in the ovary: a key role for cyclic AMP.

TitleRegulated expression of sterol carrier protein 2 in the ovary: a key role for cyclic AMP.
Publication TypeJournal Article
Year of Publication1991
AuthorsRennert H, Amsterdam A, Billheimer JT, Strauss JF
Date Published1991 Nov 26
Keywords8-Bromo Cyclic Adenosine Monophosphate, Animals, Blotting, Northern, Carrier Proteins, Cell Transformation, Neoplastic, Cells, Cultured, Cyclic AMP, Cycloheximide, Dactinomycin, Female, Gene Expression Regulation, Genes, ras, Gonadotropins, Equine, Granulosa Cells, Kinetics, Ovary, Plant Proteins, Rats, Rats, Inbred Strains, RNA, Messenger, Simian virus 40, Sterols

Sterol carrier protein 2 (SCP2) is believed to play an important role in the intracellular movement of cholesterol in steroidogenic cells. We examined the distribution of SCP2 gene expression in the rat ovary and the role of gonadotropins and cyclic AMP in the regulation of SCP2 mRNA levels. In situ hybridization revealed that the most steroidogenically active ovarian compartments (e.g., corpora lutea and theca cells) contain significant amounts of SCP2 mRNA whereas granulosa cells have modest levels. Gonadotropins, which promote follicular growth and luteinization, increased the ovarian content of SCP2 mRNA as assessed by Northern blotting along with increases in cytochrome P450scc mRNA. Using steroidogenic transformed rat granulosa cells (Grs-21), a cyclic AMP analogue (8-Br-cAMP) was found to increase SCP2 mRNA and protein levels within 24 h of treatment. P450scc mRNA was also induced whereas actin mRNA levels were not affected. The 8-Br-cAMP stimulation of SCP2 mRNA accumulation was completely inhibited by actinomycin D and cycloheximide. The cyclic AMP analogue also increased SCP2 mRNA levels in a non-steroid hormone producing transformed rat granulosa cell line Gs-8. We conclude that SCP2 gene expression in the ovary is correlated with the state of differentiation of granulosa cells. Gonadotropic hormones which stimulate luteinization of the cells increase SCP2 gene expression. These actions of gonadotropins appear to be mediated at least in part by cyclic AMP through a mechanism requiring ongoing RNA and protein synthesis. However, SCP2 gene expression is not obligatorily coupled to steroidogenic activity, as cyclic AMP analogues can increase SCP2 mRNA in a line of transformed ovarian granulosa cells incapable of synthesizing hormones.

Alternate JournalBiochemistry
PubMed ID1659897
Grant ListHD-06274 / HD / NICHD NIH HHS / United States
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Hanna Rennert, Ph.D.

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