Activation of follistatin promoter by GnRH in LbetaT2 gonadotroph cells.
Follistatin (FS) is produced and secreted from gonadotroph cells in pituitary gland as well as granulosa cells in the ovary. In the present study, we found that the FS promoter is activated by GnRH in the gonadotroph cell line, LbetaT2. Therefore, we examined the signal transduction pathways involved in the mechanism. The activation of the FS promoter by GnRH was inhibited by calphostin C, a protein kinase C inhibitor, and U0126, a MAP kinase kinase (MEK) inhibitor. Phosphorylation by protein kinase C of myristoylated alanine-rich C kinase substrate (MARCKS) in LbetaT2 cells was observed after 3-min treatment with GnRH and declined after 30 min. The subsequent activation of MAP kinase was also transient, and down-regulation of protein kinase C completely inhibited the MAP kinase activation by GnRH, suggesting that the transient activation of protein kinase C led to the transient activation of MAP kinase. Although phorbol 12-myristate 13-acetate treatment increased phosphorylation of MARCKS and activated MAP kinase, it did not activate the FS promoter. Genistein, a tyrosine kinase inhibitor, completely inhibited the GnRH-induced activation of the FS promoter, while no inhibition of the MAP kinase pathway was observed. These results suggest that the activations of both the protein kinase C and tyrosine kinase pathways are necessary for the activation of the FS promoter in gonadotroph cells.
Kihara
Sachiko
S
Department of Reproductive Medicine and Surgery, Graduate School of Medical Sciences, Kumamoto University, Japan.
Yamamoto
Hideyuki
H
Ohba
Takashi
T
Shimasaki
Shunichi
S
Okamura
Hitoshi
H
D000818:Animals; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D038681:Follistatin / Q000235:genetics*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D048730:MAP Kinase Kinase Kinase 2 / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D010911:Pituitary Neoplasms / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D011966:Receptors, LHRH / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured
D038681:Follistatin; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D005640:Follicle Stimulating Hormone; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048730:MAP Kinase Kinase Kinase 2; D048369:MAP Kinase Kinase 1; D013755:Tetradecanoylphorbol Acetate