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Activating ERK Signaling enhances 1alpha,25(OH)2D3‐regulated 25‐hydroxyvitamin D‐24‐hydroxylase (CYP24) gene expression through the transcription factor Sp3 pathway in Caco‐2 cells.
Author(s) -
Jiang Yan,
Fleet James C
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.212.7
Subject(s) - transcription factor , signal transduction , mapk/erk pathway , phosphorylation , protein kinase c , p38 mitogen activated protein kinases , kinase , chemistry , microbiology and biotechnology , gene expression , sp1 transcription factor , promoter , biology , gene , biochemistry
CYP24 is an enzyme critical for degradation of 1, 25 dihydroxyvitamin (1,25D) and its gene is strongly regulated by 1,25D. Multiple signaling pathways have been shown to modulate 1,25D‐mediated CYP24 gene expression. Phorbol ester (PMA) treatment activates PKC, as well as ERK1/2 and p38 MAP kinase signaling pathways. In addition, PMA treatment enhances 1,25D‐induced CYP24 gene transcription (mRNA, 180%; reporter gene 150–250%) in Caco‐2 cells. Inhibition of PKC, ERK, and p38 kinase signaling pathways each reduced PMA enhanced and 1,25D induced CYP24 mRNA and reporter genes by 20–40%. Mithramycin A, an inhibitor of Sp protein binding to DNA, dose‐dependently reduced both 1,25D‐induced and PMA‐enhanced CYP24 promoter activity. Bioinformatics revealed 11 putative Sp1/Sp3 sites in the −298 to +74 bp region of the human CYP24 promoter. siRNA knockout of Sp1 reduced 1,25D action by only 30% but had no effect on PMA‐mediated enhancement of CYP24 induction. In contrast, Sp3 siRNA decreased both 1,25D‐mediated CYP24 induction and PMA enhancement of that effect by 20%. Immunoprecipitation showed that PMA can phosphorylate a serine residue on Sp3 and that this is blocked by inhibition of MEK1 with U0126. These data show that a portion of the impact that PMA has on 1,25D‐mediated CYP24 induction is due to activation of ERK1/2 and subsequent phosphorylation/activation of the Sp3 transcription factor. Supported by NIDDK Award DK054111 to JCF. Grant Funding Source: NIDDK Award DK054111 to JCF