title: Role of MAP kinases in the 1,25-dihydroxyvitamin D3-induced transactivation of the rat cytochrome P450C24 (CYP24) promoter. Specific functions for ERK1/ERK2 and ERK5.
abstract: The current study investigated the action of 1,25-dihydroxyvitamin D(3) (1,25D) at the genomic and signal transduction levels to induce rat cytochrome P450C24 (CYP24) gene expression. A rat CYP24 promoter containing two vitamin D response elements and an Ets-1 binding site was used to characterize the mechanism of actions for the 1,25D secosteroid hormone. The Ets-1 binding site was determined to function cooperatively with the most proximal vitamin D response element in a hormone-dependent fashion. Evidence was obtained for distinct roles of ERK1/ERK2 and ERK5 in the 1,25D-inductive actions. Specifically, 1,25D stimulated the activities of ERK1/ERK2 and ERK5 in a Ras-dependent manner. Promoter induction was inhibited by mitogen-activated protein (MAP) kinase inhibitors (PD98059 and U0126) and a dominant-negative Ras mutant (Ras17N). Induction of CYP24 by 1,25D was also inhibited by overexpression of dominant-negative mutants of ERK1 and MEK5 (ERK1K71R and MEK5(A)). The p38 and JNK MAP kinases were not required for the action of 1,25D. 9-cis retinoid X receptor alpha (RXR alpha) interacted with ERK2 but not ERK5 in intact cells, whereas Ets-1 interacted preferentially with ERK5. Increased phosphorylation of RXR alpha and Ets-1 was detected in response to 1,25D. Activated ERK2 and ERK5 specifically phosphorylated RXR alpha and Ets-1, respectively. Mutagenesis of Ets-1 (T38A) reduced CYP24 promoter activity to levels observed with the dominant-negative MEK5(A) and inhibited ERK5-directed phosphorylation. Mutated RXR alpha (S260A) inhibited 1,25D-induced CYP24 promoter activity and abolished phosphorylation by activated ERK2. The 1,25D-inductive action through ERK5 involved Ets-1 phosphorylation at threonine 38, whereas hormone stimulation of ERK1/ERK2 required RXR alpha phosphorylation on serine 260. The ERK1/ERK2 and ERK5 modules provide a novel mechanism for linking the rapid signal transduction and slower transcription actions of 1,25D to induce CYP24 gene expression.
authors.affiliation: Department of Molecular Biosciences (Biochemistry), University of Adelaide, Adelaide, Australia 5005.
authors.forename: Prem P
authors.initials: PP
authors.lastname: Dwivedi
authors.forename: Charles S T
authors.initials: CS
authors.lastname: Hii
authors.forename: Antonio
authors.initials: A
authors.lastname: Ferrante
authors.forename: Joseph
authors.initials: J
authors.lastname: Tan
authors.forename: Channing J
authors.initials: CJ
authors.lastname: Der
authors.forename: John L
authors.initials: JL
authors.lastname: Omdahl
authors.forename: Howard A
authors.initials: HA
authors.lastname: Morris
authors.forename: Brian K
authors.initials: BK
authors.lastname: May
mesh_terms: D000818:Animals; D019556:COS Cells; D002117:Calcitriol / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats; D013250:Steroid Hydroxylases / Q000235:genetics*; D015533:Transcriptional Activation / Q000187:drug effects*; D020798:Two-Hybrid System Techniques; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D020928:Mitogen-Activated Protein Kinases; D002117:Calcitriol