[Frontiers in Bioscience E2, 1218-1226 June 1, 2010]

Signal pathway of GnRH-III inhibiting FSH-induced steroidogenesis in granulosa cells

Cui-hong Fan1,2,3, Cui-Ling Lu1, Jun-Ling Yang1, Xiao-Qian Hu1, Yu Ren1,2, Huan Cai1, Min Chen1, Zhao-Yuan Hu1, Fei Gao1,Yi-Xun Liu1

1State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, No. 5 Datun Road, Chaoyang District, Beijing 100101, China, 2Graduate School of the Chinese Academy of Sciences, Beijing 100039, China, 3School of Life Science and Technology, Beijing Institute of Technology, Beijing 10001, China

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Materials and methods
3.1. Materials
3.2. Antibodies
3.3. Animals
3.4. Granulosa cell preparation and culture
3.5. RNA extraction and real-time PCR
3.6. Western blotting
3.7. Estradiol and progesterone RIA
3.8. Data analysis and statistics
4. Results
4.1. GnRH-III inhibits FSH-induced estrogen and progesterone production
4.2. GnRH-III inhibits FSH-induced key enzymes of steroidogenesis
4.3. GnRH-III action on FSH-induced phosphorylation of Akt and p38 MAPK
4.4. GnRH-III inhibits FSH-induced FSH receptor expression
4.5. GnRH-III inhibits FSH-induced NR5A2 expression
4.6. GnRH-III inhibits FSH-induced expression of upstream stimulatory factor1 and 2
5. Discussion
6. Acknowledgment
7. References

1. ABSTRACT

Gonadotrophin-releasing hormone type 1 and type 2 have been demonstrated to inhibit follicle-stimulating hormone (FSH)-induced granulosa cell (GC) steroidogenesis. A third type of GnRH (GnRH-III) was also purified from salmon, its action on the FSH-regulated GC function, however is not clear. In the present study we demonstrated that the FSH-induced estrogen and progesterone production in cultured DES-treated GCs was significantly inhibited by GnRH-III. Furthermore, the FSH-stimulated steroidogenic acute regulatory protein and the enzymes for steroidigenesis, such as HSD3B2,aromatase and cytochrome P450 side-chain cleavage were also significantly suppressed by this peptide. The inhibitory action of GnRH-III on the FSH-induced steroidogenenisis was demonstrated via Akt and p38 mitogen-activated protein kinase signaling pathways through suppressing its own receptor expression. Further studies indicated that FSH could stimulate NR5A2 and upstream stimulatory factor (USF) activation, and their induction was significantly suppressed by the GnRH-III. Therefore, it is suggested that GnRH-III inhibiting FSH-induced steroidogenenisis in GCs might be by suppressing FSH-induced its own receptor expression via NR5A2 and USF transcriptional factors.