Abstract

In the ovary, transport of cholesterol to the mitochondrial cytochrome P450 side-chain cleavage enzyme (P450scc) is thought to be the rate- limiting step in steroid production. Since cholesterol is insoluble in the cell, it must be transported to the P450scc via a carrier molecule which facilitates cholesterol's movement across the mitochondrial membrane for steroid production. While the steroidogenic acute regulatory (StAR) protein is theorized to mediate cholesterol transport to the inner mitochondrial membrane, the mechanism for StAR-mediated cholesterol movement and the regulatory factors which control StAR mRNA levels in the ovary are uncertain. Gonadotropins have been shown to enhance StAR expression in MA-10 cells and a recent study by our laboratory has demonstrated that hCG stimulation increases StAR mRNA levels 8 to 9-fold in the ovary within 3 hours of treatment (Sandhoff & McLean, 1996a). These results indicate that gonadotropins increase StAR mRNA levels in parallel with an increase in progesterone production. In addition to the positive effects of gonadotropins on ovarian steroid production, altered cholesterol transport to the mitochondria has recently been identified as a key lytic event in the corpus luteum. Studies by Sandhoff & McLean (1996b) suggest that one antisteroidogenic action of PGF2alpha is to decrease StAR mRNA levels, which results in a decline in steroid production. Based on these investigations, we hypothesize that StAR transcription is positively regulated by gonadotropins via steroidogenic factor-1, while PGF2alpha working through PKC acts either indirectly, by reducing cAMP-mediated StAR gene expression, or directly, by reducing StAR expression via the negative regulatory transcription factor, DAX-1 or the Jun/Fos signal transduction pathway. To test this hypothesis, the Aims of this proposal are as follows:
Aim I. To determine whether StAR mRNA expression in the ovary is regulated by PKA and PKC signal transduction pathways.
Aim II. To determine whether Steroidogenic Factor 1 (SF-1) positively regulates transcription of the rat StAR gene by interaction with multiple putative SF-1 binding sites.
Aim III. To determine whether estradiol acting through an estrogen receptor half-site regulates the StAR gene.
Aim I V. To determine whether overexpression of DAX-1 or c-Fos negatively regulates StAR transcription.
Aim V. To determine whether PKA or PKC activation results in StAR phosphorylation. This study will provide new information concerning ovarian StAR expression and function during luteal development and regression.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
1R01HD035163-01A1
Application #
2624675
Study Section
Reproductive Biology Study Section (REB)
Program Officer
Laughlin, Maren R
Project Start
1998-04-01
Project End
2002-03-31
Budget Start
1998-04-01
Budget End
1999-03-31
Support Year
1
Fiscal Year
1998
Total Cost
Indirect Cost

  Institution

Name
University of South Florida
Department
Obstetrics & Gynecology
Type
Schools of Medicine
DUNS #
City
Tampa
State
FL
Country
United States
Zip Code
33612

  Publications

Zhang, Xiaohui; Merkler, Kathleen A; McLean, Mark P (2008) Characterization of regulatory intronic and exonic sequences involved in alternative splicing of scavenger receptor class B gene. Biochem Biophys Res Commun 372:173-8
Lopez, Dayami; Niesen, Melissa; Bedi, Mohini et al. (2007) Activation of the SCPx promoter in mouse adrenocortical Y1 cells. Biochem Biophys Res Commun 357:549-53
Zhang, Xiaohui; Moor, Andrea N; Merkler, Kathleen A et al. (2007) Regulation of alternative splicing of liver scavenger receptor class B gene by estrogen and the involved regulatory splicing factors. Endocrinology 148:5295-304
Liu, Qiyuan; Merkler, Kathleen A; Zhang, Xiaohui et al. (2007) Prostaglandin F2alpha suppresses rat steroidogenic acute regulatory protein expression via induction of Yin Yang 1 protein and recruitment of histone deacetylase 1 protein. Endocrinology 148:5209-19
Shea-Eaton, Wendy; Sandhoff, Todd W; Lopez, Dayami et al. (2002) Transcriptional repression of the rat steroidogenic acute regulatory (StAR) protein gene by the AP-1 family member c-Fos. Mol Cell Endocrinol 188:161-70
Nackley, Anna C; Shea-Eaton, Wendy; Lopez, Dayami et al. (2002) Repression of the steroidogenic acute regulatory gene by the multifunctional transcription factor Yin Yang 1. Endocrinology 143:1085-96
Lopez, Dayami; Sanchez, Mark D; Shea-Eaton, Wendy et al. (2002) Estrogen activates the high-density lipoprotein receptor gene via binding to estrogen response elements and interaction with sterol regulatory element binding protein-1A. Endocrinology 143:2155-68
Lopez, D; Nackley, A C; Shea-Eaton, W et al. (2001) Effects of mutating different steroidogenic factor-1 protein regions on gene regulation. Endocrine 14:353-62
Lopez, D; Shea-Eaton, W; Sanchez, M D et al. (2001) DAX-1 represses the high-density lipoprotein receptor through interaction with positive regulators sterol regulatory element-binding protein-1a and steroidogenic factor-1. Endocrinology 142:5097-106
Shea-Eaton, W; Lopez, D; McLean, M P (2001) Yin yang 1 protein negatively regulates high-density lipoprotein receptor gene transcription by disrupting binding of sterol regulatory element binding protein to the sterol regulatory element. Endocrinology 142:49-58

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