Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/9624
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Type: Journal article
Title: Calcitonin stimulates expression of the rat 25-hydroxyvitamin D3-24-hydroxylase (CYP24) promoter in HEK-293 cells expressing calcitonin receptor: identification of signaling pathways
Author: Gao, X.
Dwivedi, P.
Omdahl, J.
Morris, H.
May, B.
Citation: Journal of Molecular Endocrinology, 2004; 32(1):87-98
Publisher: Soc Endocrinology
Issue Date: 2004
ISSN: 0952-5041
1479-6813
Abstract: Regulation of the gene for renal 25-hydroxyvitamin D-24-hydroxylase (CYP24) is important for controlling the level of circulating 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). We report here for the first time that the peptide hormone calcitonin significantly stimulates expression of a rat CYP24 promoter-luciferase construct in both transiently and stably transfected kidney HEK-293 cells. A GC box at −114/−101 and a CCAAT box at −62/−51 have been identified that underlie both basal expression of the CYP24 promoter and the calcitonin inductive response. Data from overexpression studies suggested that Sp1 and NF-Y are the proteins that function through the GC and CCAAT boxes respectively. ERK1/2 signaling pathways were not involved in the calcitonin-mediated response, since stimulation of the promoter was unaffected by the pharmacological ERK1/2 inhibitor PD98059 and by a dominant negative mutant of ERK1/2 (ERK1K71R). In contrast, calcitonin induction but not basal expression was dependent on protein kinase A and protein kinase C (PKC) activities with the inhibitors H89 and calphostin C lowering induction by 50–60%. The atypical PKC, PKC contributes to calcitonin induction, but not to basal expression of the CYP24 promoter, since overexpression of a dominant negative clone PKC K281 M lowered induction by 50%. Cotransfection of a dominant negative form of Ras resulted in calcitonin-mediated induction being reduced also by about 50%. A Ras–PKC signaling pathway for calcitonin action is proposed, which acts through the GC box. The findings have been extrapolated to the in vivo situation where we suggest that induction of renal CYP24 by calcitonin could be important under hypercalcemic conditions thus contributing to the lowering of circulating 1,25(OH)2D3 levels.
Keywords: Cells, Cultured
Animals
Humans
Sulfonamides
Flavonoids
Isoquinolines
Naphthalenes
Calcitonin
Cytochrome P-450 Enzyme System
Steroid Hydroxylases
Cyclic AMP-Dependent Protein Kinases
Extracellular Signal-Regulated MAP Kinases
Protein Kinase C
Immunoglobulins
CCAAT-Binding Factor
Receptors, Calcitonin
Enzyme Inhibitors
Cloning, Molecular
Mutation
Genes, Reporter
Promoter Regions, Genetic
Vitamin D3 24-Hydroxylase
DOI: 10.1677/jme.0.0320087
Published version: http://dx.doi.org/10.1677/jme.0.0320087
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