Role of calcium-calmodulin-dependent protein kinase cascade in thyrotropin (TSH)-releasing hormone induction of TSH and prolactin gene expression.
TRH binds to a membrane receptor that activates several intracellular signaling pathways and increases transcription of the TSH and prolactin (PRL) genes. Although TRH induces TSH and PRL gene expression, the underlying mechanism is not clear. In this report we examined the role of the Ca(2+)/calmodulin-dependent protein (CaM) kinase cascade in mediating TRH-stimulated transcription of TSH and PRL. RT-PCR and Western blot analysis were used to show that CaM kinase kinase (CaM-KK) and CaM IV (CaM-KIV) were present in rat anterior pituitary and its cell line GH(3). Next, the effects of constitutively active CaM-KIV (CaM-KIVc) or its dominant negative mutant (CaM-KIVdn) on TSH and PRL promoter activity were tested in GH(3) cells. The results showed that either CaM-KIVc alone or an upstream kinase, CaM-KK, induced the activity of both TSH and PRL promoters. Exposure of GH(3) cells to 100 microm TRH induced CaM-KIV activity within 5 min and, as expected, also increased both TSH and PRL promoter activity. In contrast, cells carrying the CaM-KIVdn isoform had suppressed TRH induction of both TSH and PRL promoter activity. These results indicate that the CaM-KK-CaM-KIV cascade probably plays an important role in TRH induction of TSH and PRL transcriptional activity in pituitary cells.
Murao
Koji
K
First Department of Internal Medicine, Faculty of Medicine, Kagawa University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-0793, Japan. mkoji@kms.ac.jp
Imachi
Hitomi
H
Cao
Wen M
WM
Yu
Xiao
X
Tokumitsu
Hiroshi
H
Inuzuka
Hiroyuki
H
Wong
Norman C W
NC
Shupnik
Margaret A
MA
Kobayashi
Ryoji
R
Ishida
Toshihiko
T
D000818:Animals; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016373:DNA, Antisense; D004789:Enzyme Activation / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D008297:Male; D010902:Pituitary Gland / Q000166:cytology; D011388:Prolactin / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D013972:Thyrotropin / Q000235:genetics*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology
D016373:DNA, Antisense; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D013972:Thyrotropin; D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517686:Camk4 protein, rat