Stimulatory effect of progesterone on the expression of steroidogenic acute regulatory protein in MA-10 Leydig cells

TY - JOUR

T1 - Stimulatory effect of progesterone on the expression of steroidogenic acute regulatory protein in MA-10 Leydig cells

AU - Schwarzenbach, Heidi

AU - Manna, Pulak R

AU - Stocco, Douglas M

AU - Chakrabarti, Gopa

AU - Mukhopadhyay, Amal K

PY - 2003/3/1

Y1 - 2003/3/1

N2 - The steroidogenic acute regulatory protein (StAR), by virtue of its ability to facilitate the intramitochondrial transport of cholesterol, plays an important role in regulating steroid hormone biosynthesis in steroidogenic cells. In agreement with published data, both StAR expression and progesterone production in MA-10 mouse Leydig tumor cells could be stimulated with hCG and 8Br-cAMP. Addition of aminoglutethimide, an inhibitor of cholesterol side chain cleavage (P450(scc)) enzyme, not only resulted in a drastic inhibition of progesterone production but also in an attenuation of StAR expression in response to either hCG or 8-Br-cAMP. Therefore, we addressed the question of whether progesterone, the end product of the steroidogenic cascade in these cells, could be in a position to regulate the StAR gene expression. In MA-10 cells, we report here that progesterone in microgram amounts can induce StAR gene expression in a time- and dose-dependent manner. StAR expression in response to a maximally effective concentration of progesterone of 10 microg/ml was highest at 6 h and started decreasing thereafter. The effect of progesterone on StAR protein and StAR mRNA induction was mimicked by its synthetic analog, progestin R5020, but not by other steroids, including dexamethasone, estradiol, testosterone, and dihydrotestosterone. Dexamethasone, in contrast, was able to inhibit StAR expression in MA-10 cells. Surprisingly, RU486, a potent antagonist of progesterone and glucocorticoid action, had a stimulatory effect on StAR mRNA levels. Reverse transcription-polymerase chain reaction analysis demonstrated the absence of the classical form of progesterone receptor in MA-10 cells. Thus, for the first time, a direct stimulatory effect of a steroid on StAR gene expression has been demonstrated. Furthermore, these results provide a new insight, indicating that progesterone mediates the activation of StAR expression exerted presumably through a novel, nonclassical progesterone receptor in mouse Leydig cells.

AB - The steroidogenic acute regulatory protein (StAR), by virtue of its ability to facilitate the intramitochondrial transport of cholesterol, plays an important role in regulating steroid hormone biosynthesis in steroidogenic cells. In agreement with published data, both StAR expression and progesterone production in MA-10 mouse Leydig tumor cells could be stimulated with hCG and 8Br-cAMP. Addition of aminoglutethimide, an inhibitor of cholesterol side chain cleavage (P450(scc)) enzyme, not only resulted in a drastic inhibition of progesterone production but also in an attenuation of StAR expression in response to either hCG or 8-Br-cAMP. Therefore, we addressed the question of whether progesterone, the end product of the steroidogenic cascade in these cells, could be in a position to regulate the StAR gene expression. In MA-10 cells, we report here that progesterone in microgram amounts can induce StAR gene expression in a time- and dose-dependent manner. StAR expression in response to a maximally effective concentration of progesterone of 10 microg/ml was highest at 6 h and started decreasing thereafter. The effect of progesterone on StAR protein and StAR mRNA induction was mimicked by its synthetic analog, progestin R5020, but not by other steroids, including dexamethasone, estradiol, testosterone, and dihydrotestosterone. Dexamethasone, in contrast, was able to inhibit StAR expression in MA-10 cells. Surprisingly, RU486, a potent antagonist of progesterone and glucocorticoid action, had a stimulatory effect on StAR mRNA levels. Reverse transcription-polymerase chain reaction analysis demonstrated the absence of the classical form of progesterone receptor in MA-10 cells. Thus, for the first time, a direct stimulatory effect of a steroid on StAR gene expression has been demonstrated. Furthermore, these results provide a new insight, indicating that progesterone mediates the activation of StAR expression exerted presumably through a novel, nonclassical progesterone receptor in mouse Leydig cells.

KW - 8-Bromo Cyclic Adenosine Monophosphate

KW - Aminoglutethimide

KW - Animals

KW - Blotting, Northern

KW - Dexamethasone

KW - Enzyme Inhibitors

KW - Female

KW - Gene Expression Regulation

KW - Glucocorticoids

KW - Leydig Cell Tumor

KW - Mice

KW - Mifepristone

KW - Phosphoproteins

KW - Progesterone

KW - Progesterone Congeners

KW - Promegestone

KW - RNA, Messenger

KW - Receptors, Glucocorticoid

KW - Receptors, Progesterone

KW - Reverse Transcriptase Polymerase Chain Reaction

KW - Tumor Cells, Cultured

M3 - SCORING: Journal article

C2 - 12604660

VL - 68

SP - 1054

EP - 1063

JO - BIOL REPROD

JF - BIOL REPROD

SN - 0006-3363

IS - 3

ER -