Differential regulation of inhibin/activin alpha- and beta A-subunit and follistin mRNAs by cyclic AMP and phorbol ester in cultured human granulosa-luteal cells.
Granulosa cell-derived inhibin A (a dimer of alpha- and beta A-subunits), activin A (a homodimer of beta A-subunits) and the activin-binding protein follistatin are important regulators of human ovarian steroidogenesis. We here studied how 8-bromo-cAMP (8br-cAMP), a protein kinase A activator, and 12-O-tetradecanoylphorbol 13-acetate (TPA), a protein kinase C activator, affect the steady-state levels of alpha- and beta A-subunit and follistatin mRNAs in cultured human granulosa-luteal cells. 8br-cAMP induced alpha- and beta A-subunit and follistatin steady-state mRNA levels in a time- and concentration-dependent manner. The levels of alpha-subunit mRNAs were stimulated by 8br-cAMP in a sustained manner with a maximal induction seen at the time points 24 and 48 h. By contrast, beta A-subunit and follistatin mRNA levels were rapidly and transiently induced by 8br-cAMP with maximal effects observed at 3 h and 8 h, respectively. TPA did not affect basal alpha-subunit mRNA levels but it rapidly induced beta A-subunit mRNAs at 3 h and the stimulation was still evident at 48 h. TPA induced follistatin mRNA levels with kinetics similar to 8br-cAMP but to a lesser extent. Moreover, 8br-cAMP and TPA stimulated beta A-subunit and follistatin mRNA levels synergistically at 3 h. By contrast, TPA had a potent inhibitory effect on 8br-cAMP- and hCG-induced alpha-subunit levels. Neither 8br-cAMP nor TPA regulated inhibin/activin beta B-subunit mRNA levels. Taken together the activation of protein kinase-A and -C by 8br-cAMP and TPA, respectively, lead to clearly differential responses in the steady-state levels of inhibin activin alpha- and beta A-subunit and follistatin mRNAs. These results suggest that the inhibin A vs. activin A ratio as well as follistatin levels are regulated by multiple second-messenger pathways in the human ovary.
Tuuri
T
T
Haartman Institute, Department of Bacteriology and Immunology, University of Helsinki, Finland. Timo.Tuuri@Helsinki.Fi
Erämaa
M
M
Van Schaik
R H
RH
Ritvos
O
O
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D028341:Activins; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005260:Female; D038681:Follistatin; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007265:Inhibins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors
D006063:Chorionic Gonadotropin; D038681:Follistatin; D006023:Glycoproteins; D012333:RNA, Messenger; D028341:Activins; D015124:8-Bromo Cyclic Adenosine Monophosphate; D007265:Inhibins; D013755:Tetradecanoylphorbol Acetate