Follistatin gene expression by gonadotropin-releasing hormone: a role for cyclic AMP and mitogen-activated protein kinase signaling pathways in clonal gonadotroph LbetaT2 cells.
The purpose of the present study was to examine the signal transduction pathways involved in follistatin gene expression induced by GnRH in the LbetaT2 cell line. The LHbeta-subunit was predominantly increased by high frequency GnRH pulses (30 min interval); whereas low frequency pulses (120 min) increased FSHbeta. In a static culture, follistatin expression was significantly increased at 12 h (2.35 +/- 0.80-fold) after the addition of GnRH. Following pulsatile stimulation, follistatin mRNA was increased by high frequency GnRH pulses, but not by low frequency pulses. In a static culture, GnRH maximally activated extracellular signal-regulated kinase (ERK) 10 min (3.2 +/- 0.55-fold) after treatment. In addition, intracellular cAMP accumulated up to 2.1 +/- 0.76-fold. Follistatin promoter activity was significantly increased following transfection with either a constitutively active cAMP dependent protein kinase (PKA) or a constitutively active MEK kinase (MEKK). The induction of follistatin gene expression by GnRH was completely inhibited by H89, a protein kinase A inhibitor, and U0126, a MEK inhibitor. Follistatin gene expression was also activated by both PACAP and CPT-cAMP under static culture conditions. Maximal ERK activation levels were nearly identical regardless of GnRH pulse frequency; however, high frequency GnRH pulses elevated both the intracellular cAMP level as well as cAMP-response element (Cre) promoter activity. These results suggest that both the PKA and ERK pathways are necessary for the induction of the follistatin promoter. Furthermore, the intracellular cAMP level, but not ERK activity, determined whether follistatin was induced following high frequency GnRH pulses.
Mutiara
Sandra
S
Department of Obstetrics and Gynecology, Shimane University, School of Medicine, Izumo City, Shimane Prefecture, Japan.
Kanasaki
Haruhiko
H
Oride
Aki
A
Purwana
Indri N
IN
Shimasaki
Shunichi
S
Yamamoto
Hideyuki
H
Miyazaki
Kohji
K
D002460:Cell Line; D002999:Clone Cells; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism; D038681:Follistatin / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D052681:Gonadotrophs / Q000166:cytology* / Q000187:drug effects*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors
D037201:Follicle Stimulating Hormone, beta Subunit; D038681:Follistatin; D037101:Luteinizing Hormone, beta Subunit; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D047428:Protein Kinase Inhibitors; D013873:Thionucleotides; D007987:Gonadotropin-Releasing Hormone; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases