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The Transcriptional Factor Prolactin Regulatory Element-Binding Protein Mediates the Gene Transcription of Adrenal Scavenger Receptor Class B Type I via 3',5'-Cyclic Adenosine 5'-Monophosphate

Division of Endocrinology and Metabolism, Departments of Internal Medicine (K.M., H.Im., X.Y., W.M.C., T.M., H.D., T.I.), of Cardiorenal and Cerebrovascular Medicine (N.H.), and of Diagnostic Pathology (R.H.), Faculty of Medicine, and Information Technology Center (H.Iw.), Kagawa University, 1750-1, Kagawa 761-0793, Japan

Address all correspondence and requests for reprints to: Koji Murao, Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe Miki-CHO, Kita-gun, Kagawa 761-0793, Japan. E-mail: mkoji{at}med.kagawa-u.ac.jp.

Prolactin regulatory element-binding (PREB) protein is a transcription factor that regulates prolactin promoter activity in the rat anterior pituitary. The PREB protein is not only expressed in the anterior pituitary but also in the adrenal gland. However, the role of PREB in the adrenal gland is not clearly understood. Scavenger receptor class B type I (SR-BI) is a receptor for high-density lipoprotein that mediates the cellular uptake of high-density lipoprotein-cholesteryl ester and is a major route for cholesterol delivery to the steroidogenic pathway in the adrenal gland. In the present study, we have examined the role of PREB in regulating SR-BI. SR-BI expression was found to be regulated by cAMP, which stimulated the expression of PREB in a dose-dependent manner. Conversely, overexpression of PREB using a PREB-expressing adenovirus increased the expression of the SR-BI protein in the adrenocortical cell line Y-1. In addition, PREB induced the expression of the luciferase reporter protein that was under the control of the SR-BI promoter. EMSA showed that PREB mediates its transcriptional effect by binding to the PREB-responsive cis-element of the SR-BI promoter. Finally, we used small interfering RNA to inhibit PREB expression in the Y-1 cells and demonstrated that the knockdown of PREB expression attenuated the effects of cAMP on SR-BI expression. In summary, our data showed that in the adrenal gland, PREB regulates the transcription of the SR-BI gene via cAMP.