This Article Full Text Full Text (PDF) All Versions of this Article: 145/11/4846    most recent Author Manuscript (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Murao, K. Articles by Ishida, T. Search for Related Content PubMed PubMed Citation Articles by Murao, K. Articles by Ishida, T.

Role of Calcium-Calmodulin-Dependent Protein Kinase Cascade in Thyrotropin (TSH)-Releasing Hormone Induction of TSH and Prolactin Gene Expression

First Department of Internal Medicine (K.M., H.I., W.M.C., X.Y., T.I.) and Department of Signal Transduction Sciences (H.T., H.I., R.K.), Faculty of Medicine, Kagawa University, Kagawa 761-0793, Japan; Departments of Medicine and Biochemistry and Molecular Biology, Faculty of Medicine, University of Calgary (N.C.W.W.), Calgary, Canada T2N 4N1; and Department of Internal Medicine, Division of Endocrinology and Metabolism, University of Virginia (M.A.S.), Charlottesville, Virginia 22903

Address all correspondence and requests for reprints to: Dr. Koji Murao, First Department of Internal Medicine, Faculty of Medicine, Kagawa University, 1750-1 Miki-cho, Kita-gun, Kagawa 761-0793, Japan. E-mail: mkoji{at}kms.ac.jp.

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 Ca²⁺/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 GH₃. 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 GH₃ 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 GH₃ cells to 100 µM 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.