This Article Full Text Full Text (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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Lin, X.-z. Articles by Okamoto, M. Search for Related Content PubMed PubMed Citation Articles by Lin, X.-z. Articles by Okamoto, M. Pubmed/NCBI databases Compound via MeSH Substance via MeSH

Salt-Inducible Kinase Is Involved in the ACTH/cAMP-Dependent Protein Kinase Signaling in Y1 Mouse Adrenocortical Tumor Cells

Department of Molecular Physiological Chemistry (X.L., H.T., Y.K., J.D., N.H., A.M., M.O.), Osaka University Medical School H-1, Osaka, 565-0871, Japan; and College of Nutrition (Y.N.), Koshien University, Hyogo, 665-0006, Japan

Address all correspondence and request for reprints to: Mitsuhiro Okamoto, Department of Molecular Physiological Chemistry, Osaka University Medical School H-1, 2–2 Yamadaoka, Suita, Osaka, 565-0871, Japan. E-mail: mokamoto{at}mr-mbio.med.osaka-u.ac.jp

The involvement of salt-inducible kinase, a recently cloned protein serine/threonine kinase, in adrenal steroidogenesis was investigated. When Y1 mouse adrenocortical tumor cells were stimulated by ACTH, the cellular content of salt-inducible kinase mRNA, protein, and enzyme activity changed rapidly. Its level reached the highest point in 1–2 h and returned to the initial level after 8 h. The mRNA levels of cholesterol side-chain cleavage cytochrome P450 and steroidogenic acute regulatory protein, on the other hand, began to rise after a few hours, reaching the highest levels after 8 h. The salt-inducible kinase mRNA level in ACTH-, forskolin-, or 8-bromo-cAMP-treated Kin-7 cells, mutant Y1 with less cAMP-dependent PKA activity, remained low. However, Kin-7 cells, when transfected with a PKA expression vector, expressed salt-inducible kinase mRNA. Y1 cells that overexpressed salt-inducible kinase were isolated, and the mRNA levels of steroidogenic genes in these cells were compared with those in the parent Y1. The level of cholesterol side-chain cleavage cytochrome P450 mRNA in the salt-inducible kinase-overexpressing cells was markedly low compared with that in the parent, while the levels of Ad4BP/steroidogenic factor-1-, ACTH receptor-, and steroidogenic acute regulatory protein-mRNAs in the former were similar to those in the latter. The ACTH-dependent expression of cholesterol side-chain cleavage cytochrome P450- and steroidogenic acute regulatory protein-mRNAs in the salt-inducible kinase-overexpressing cells was significantly repressed. The promoter activity of the cholesterol side-chain cleavage cytochrome P450 gene was assayed by using Y1 cells transfected with a human cholesterol side-chain cleavage cytochrome P450 promoter-linked reporter gene. Addition of forskolin to the culture medium enhanced the cholesterol side-chain cleavage cytochrome P450 promoter activity, but the forskolin-dependently activated promoter activity was inhibited when the cells were transfected with a salt-inducible kinase expression vector. This inhibition did not occur when the cells were transfected with a salt-inducible kinase (K56M) vector that encoded an inactive kinase. The salt-inducible kinase’s inhibitory effect was also observed when nonsteroidogenic, nonAd4BP/steroidogenic factor-1 -expressing, NIH3T3 cells were used for the promoter assays. These results suggested that salt-inducible kinase might play an important role(s) in the cAMP-dependent, but Ad4BP/steroidogenic factor-1-independent, gene expression of cholesterol side-chain cleavage cytochrome P450 in adrenocortical cells.

This article has been cited by other articles:

				M. Sjostrom, K. Stenstrom, K. Eneling, J. Zwiller, A. I. Katz, H. Takemori, and A. M. Bertorello SIK1 is part of a cell sodium-sensing network that regulates active sodium transport through a calcium-dependent process PNAS, October 23, 2007; 104(43): 16922 - 16927. [Abstract] [Full Text] [PDF]

				N. Horike, H. Takemori, Y. Katoh, J. Doi, L. Min, T. Asano, X. J. Sun, H. Yamamoto, S. Kasayama, M. Muraoka, et al. Adipose-specific Expression, Phosphorylation of Ser794 in Insulin Receptor Substrate-1, and Activation in Diabetic Animals of Salt-inducible Kinase-2 J. Biol. Chem., May 9, 2003; 278(20): 18440 - 18447. [Abstract] [Full Text] [PDF]

				H. Takemori, Y. Katoh, N. Horike, J. Doi, and M. Okamoto ACTH-induced Nucleocytoplasmic Translocation of Salt-inducible Kinase. IMPLICATION IN THE PROTEIN KINASE A-ACTIVATED GENE TRANSCRIPTION IN MOUSE ADRENOCORTICAL TUMOR CELLS J. Biol. Chem., October 25, 2002; 277(44): 42334 - 42343. [Abstract] [Full Text] [PDF]

				J. Doi, H. Takemori, X.-z. Lin, N. Horike, Y. Katoh, and M. Okamoto Salt-inducible Kinase Represses cAMP-dependent Protein Kinase-mediated Activation of Human Cholesterol Side Chain Cleavage Cytochrome P450 Promoter through the CREB Basic Leucine Zipper Domain J. Biol. Chem., May 3, 2002; 277(18): 15629 - 15637. [Abstract] [Full Text] [PDF]