Possible involvement of mitogen-activated protein kinase phosphatase-1 (MKP-1) in thyrotropin-releasing hormone (TRH)-induced prolactin gene expression.
The role of extracellular signal-regulated kinase (ERK) in mediating the ability of thyrotropin-releasing hormone (TRH) to stimulate the prolactin gene has been well elucidated. ERK is inactivated by a dual specificity phosphatase, mitogen-activated protein kinase phosphatase (MKP). In this study, we examined the induction of MKP-1 protein by thyrotropin-releasing hormone (TRH) in pituitary GH3 cells, and investigated the possible role for MKP-1 in TRH-induced prolactin gene expression. MKP-1 protein was induced significantly from 60 min after TRH stimulation, and remained elevated at 4h. The effect of TRH on MKP-1 expression was completely prevented in the presence of the MEK inhibitor, U0126. In the experiments using triptolide, a potent blocker for MKP-1, MKP-1 induction by TRH was completely inhibited in a dose-dependent manner. TRH-induced ERK activation was significantly enhanced in this condition. Prolactin promoter activity, activated by TRH, was reduced to the control level in the presence of triptolide in a dose-dependent manner. In GH3 cells, which were transfected with MKP-1 specific siRNA, both the basal and TRH-stimulated activities of the prolactin promoter were significantly reduced compared to the cells transfected with negative control siRNA. Our present results support a critical role of MKP-1 in TRH-induced, ERK-dependent, prolactin gene expression.
Oride
Aki
A
Department of Obstetrics and Gynecology, Shimane University School of Medicine, Shimane Prefecture, Izumo City, Japan.
Kanasaki
Haruhiko
H
Purwana
Indri N
IN
Miyazaki
Kohji
K
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D004224:Diterpenes / Q000494:pharmacology; D054638:Dual Specificity Phosphatase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004852:Epoxy Compounds / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D005786:Gene Expression Regulation; D009570:Nitriles / Q000494:pharmacology; D010616:Phenanthrenes / Q000494:pharmacology; D011388:Prolactin / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism* / Q000494:pharmacology
D002070:Butadienes; D004224:Diterpenes; D004791:Enzyme Inhibitors; D004852:Epoxy Compounds; D009570:Nitriles; D010616:Phenanthrenes; D034741:RNA, Small Interfering; C113580:U 0126; C001899:triptolide; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D048049:Extracellular Signal-Regulated MAP Kinases; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat