This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wang, Y. Articles by Ge, W. Search for Related Content PubMed PubMed Citation Articles by Wang, Y. Articles by Ge, W.

Involvement of Cyclic Adenosine 3',5'-Monophosphate in the Differential Regulation of Activin ßA and ßB Expression by Gonadotropin in the Zebrafish Ovarian Follicle Cells

Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China

Address all correspondence and requests for reprints to: Wei Ge, Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. E-mail: weige{at}cuhk.edu.hk.

Activin is a dimeric protein consisting of two similar but distinct ß-subunits, ßA and ßB. In our previous studies, both activin A (ßAßA) and activin B (ßBßB) have been demonstrated to stimulate oocyte maturation and promote oocyte maturational competence in the zebrafish. Follistatin, a specific activin-binding protein, can block both activin- and gonadotropin-induced final oocyte maturation in vitro, suggesting that activin is likely a downstream mediator of gonadotropin actions in the zebrafish ovary. In the present study, a full-length cDNA encoding zebrafish ovarian activin ßA was cloned and sequenced. The precursor of zebrafish activin ßA consists of 395 amino acids and its mature region exhibits about 78% homology with that of mammals. Using an in vitro primary culture of the ovarian follicle cells and semiquantitative RT-PCR assays, we examined the regulation of activin ßA and ßB expression by human chorionic gonadotropin (hCG) and its intracellular signal transduction mechanisms. hCG (15 IU/ml) increased the mRNA level of activin ßA-subunit; however, it significantly down-regulated the steady-state expression level of activin ßB in a time- and dose-dependent manner. The differential regulation of the two ß-subunits by hCG could be mimicked by 3-isobutyl-1-methylxanthine, forskolin, and dibutyryl-cAMP, suggesting involvement of the intracellular cAMP pathway. Interestingly, H89 (a specific inhibitor of protein kinase A, PKA) could effectively block hCG- and forskolin-stimulated activin ßA expression at 10 µM, but it was unable to reverse the inhibitory effects of hCG and forskolin on ßB expression. This suggests that the hCG-stimulated activin ßA expression is dependent on the activation of the cAMP-PKA pathway, whereas the inhibitory effect of hCG on activin ßB expression is likely mediated by PKA-independent pathway(s).

This article has been cited by other articles:

				M. Kouzu-Fujita, Y. Mezaki, S. Sawatsubashi, T. Matsumoto, I. Yamaoka, T. Yano, Y. Taketani, H. Kitagawa, and S. Kato Coactivation of Estrogen Receptor {beta} by Gonadotropin-Induced Cofactor GIOT-4 Mol. Cell. Biol., January 1, 2009; 29(1): 83 - 92. [Abstract] [Full Text] [PDF]

				Y. Wang, J. Li, C. Ying Wang, A. H. Yan Kwok, and F. C. Leung Epidermal Growth Factor (EGF) Receptor Ligands in the Chicken Ovary: I. Evidence for Heparin-Binding EGF-Like Growth Factor (HB-EGF) as a Potential Oocyte-Derived Signal to Control Granulosa Cell Proliferation and HB-EGF and Kit Ligand Expression Endocrinology, July 1, 2007; 148(7): 3426 - 3440. [Abstract] [Full Text] [PDF]

				Y. Wang, J. Li, C. Y. Wang, A. H. Y. Kwok, and F. C. Leung Identification of the Endogenous Ligands for Chicken Growth Hormone-Releasing Hormone (GHRH) Receptor: Evidence for a Separate Gene Encoding GHRH in Submammalian Vertebrates Endocrinology, May 1, 2007; 148(5): 2405 - 2416. [Abstract] [Full Text] [PDF]

				A. H. Y. Kwok, Y. Wang, C. Y. Wang, and F. C. Leung Cloning of Chicken Glucocorticoid Receptor (GR) and Characterization of its Expression in Pituitary and Extrapituitary Tissues Poult. Sci., February 1, 2007; 86(2): 423 - 430. [Abstract] [Full Text] [PDF]

				W.-K. So, H.-F. Kwok, and W. Ge Zebrafish Gonadotropins and Their Receptors: II. Cloning and Characterization of Zebrafish Follicle-Stimulating Hormone and Luteinizing Hormone Subunits--Their Spatial-Temporal Expression Patterns and Receptor Specificity Biol Reprod, June 1, 2005; 72(6): 1382 - 1396. [Abstract] [Full Text] [PDF]

				H.-F. Kwok, W.-K. So, Y. Wang, and W. Ge Zebrafish Gonadotropins and Their Receptors: I. Cloning and Characterization of Zebrafish Follicle-Stimulating Hormone and Luteinizing Hormone Receptors-- Evidence for Their Distinct Functions in Follicle Development Biol Reprod, June 1, 2005; 72(6): 1370 - 1381. [Abstract] [Full Text] [PDF]

				M Zhang, Y Tao, B Zhou, H Xie, F Wang, L Lei, L Huo, Q Sun, and G Xia Atrial natriuretic peptide inhibits the actions of FSH and forskolin in meiotic maturation of pig oocytes via different signalling pathways J. Mol. Endocrinol., April 1, 2005; 34(2): 459 - 472. [Abstract] [Full Text] [PDF]

				Y. Wang and W. Ge Developmental Profiles of Activin {beta}A, {beta}B, and Follistatin Expression in the Zebrafish Ovary: Evidence for Their Differential Roles During Sexual Maturation and Ovulatory Cycle Biol Reprod, December 1, 2004; 71(6): 2056 - 2064. [Abstract] [Full Text] [PDF]

				Y. Wang and W. Ge Cloning of Epidermal Growth Factor (EGF) and EGF Receptor from the Zebrafish Ovary: Evidence for EGF as a Potential Paracrine Factor from the Oocyte to Regulate Activin/Follistatin System in the Follicle Cells Biol Reprod, September 1, 2004; 71(3): 749 - 760. [Abstract] [Full Text] [PDF]

				Y. Wang and W. Ge Spatial Expression Patterns of Activin and Its Signaling System in the Zebrafish Ovarian Follicle: Evidence for Paracrine Action of Activin on the Oocytes Biol Reprod, December 1, 2003; 69(6): 1998 - 2006. [Abstract] [Full Text] [PDF]

				Y. Wang, A. O. L. Wong, and W. Ge Cloning, Regulation of Messenger Ribonucleic Acid Expression, and Function of a New Isoform of Pituitary Adenylate Cyclase-Activating Polypeptide in the Zebrafish Ovary Endocrinology, November 1, 2003; 144(11): 4799 - 4810. [Abstract] [Full Text] [PDF]