Integration of hormone signaling in the regulation of human 25(OH)D 3 24-hydroxylase transcription

Frank Barletta, Puneet Dhawan, Sylvia Christakos

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The current study sought to define the molecular mechanisms involved in the cross talk between 1,25-dihydroxyvitamin D3 [1,25(OH) 2D3] and activators of PKC in the regulation of 25(OH)D3 24-hydroxlyase [24(OH)ase]. Transfection of the h24(OH)ase promoter construct [-5,500/-22 luciferase; vitamin D response elements at -294/-274 and -174/-151; AP-1 site at -1,167/-1,160] in vitamin D receptor (VDR)-transfected COS-7 cells resulted in strong activation by 1,25(OH) 2D3. In these cells, cotreatment with the PKC activator TPA and 1,25(OH)2D3 yielded a 27-fold increase in luciferase activity, which was 2- to 3-fold greater than activation obtained with 1,25(OH)2D3 alone (P < 0.05). Similar results were observed using LLCPK-1 kidney cells, suggesting that the previously observed enhancement of 1,25 (OH)2D3-induced renal 24(OH)ase mRNA and activity by PKC activation occurs at the level of transcription. The functional cooperation between PKC activation and VDR was not found to be mediated by the AP-1 site in the h24(OH)ase promoter or by enhanced binding of GRIP or DRIP205 to VDR and was also not due to PKC-mediated phosphorylation of VDR on Ser51. Our study demonstrates that, in LLCPK-1 kidney cells, the PKC enhancement of 1,25(OH)2D 3-stimulated transcription may be due, in part, to an increase in VDR concentration. In addition, inhibitors of the MAPK pathway were found to decrease the TPA enhancement (P < 0.05). Because activation of MAPK has been reported to result in the phosphorylation of SRC-1 and in functional cooperation between SRC-1 and CREB binding protein, we propose that the potentiation of VDR-mediated transcription may also be mediated through changes in the phosphorylation of specific VDR coregulators.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume286
Issue number4 49-4
DOIs
StatePublished - Apr 1 2004

Fingerprint

Calcitriol Receptors
Transcription
Mixed Function Oxygenases
Hormones
Chemical activation
Phosphorylation
Transcription Factor AP-1
Luciferases
Mediator Complex Subunit 1
Vitamin D Response Element
CREB-Binding Protein
Kidney
Calcitriol
COS Cells
Transfection
Messenger RNA

All Science Journal Classification (ASJC) codes

  • Physiology (medical)
  • Physiology
  • Endocrinology, Diabetes and Metabolism

Keywords

  • 1,25-dihydroxyvitamin D
  • Phosphorylation
  • Protein kinase C
  • Vitamin D receptor
  • Vitamin D regulation

Cite this

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title = "Integration of hormone signaling in the regulation of human 25(OH)D 3 24-hydroxylase transcription",
abstract = "The current study sought to define the molecular mechanisms involved in the cross talk between 1,25-dihydroxyvitamin D3 [1,25(OH) 2D3] and activators of PKC in the regulation of 25(OH)D3 24-hydroxlyase [24(OH)ase]. Transfection of the h24(OH)ase promoter construct [-5,500/-22 luciferase; vitamin D response elements at -294/-274 and -174/-151; AP-1 site at -1,167/-1,160] in vitamin D receptor (VDR)-transfected COS-7 cells resulted in strong activation by 1,25(OH) 2D3. In these cells, cotreatment with the PKC activator TPA and 1,25(OH)2D3 yielded a 27-fold increase in luciferase activity, which was 2- to 3-fold greater than activation obtained with 1,25(OH)2D3 alone (P < 0.05). Similar results were observed using LLCPK-1 kidney cells, suggesting that the previously observed enhancement of 1,25 (OH)2D3-induced renal 24(OH)ase mRNA and activity by PKC activation occurs at the level of transcription. The functional cooperation between PKC activation and VDR was not found to be mediated by the AP-1 site in the h24(OH)ase promoter or by enhanced binding of GRIP or DRIP205 to VDR and was also not due to PKC-mediated phosphorylation of VDR on Ser51. Our study demonstrates that, in LLCPK-1 kidney cells, the PKC enhancement of 1,25(OH)2D 3-stimulated transcription may be due, in part, to an increase in VDR concentration. In addition, inhibitors of the MAPK pathway were found to decrease the TPA enhancement (P < 0.05). Because activation of MAPK has been reported to result in the phosphorylation of SRC-1 and in functional cooperation between SRC-1 and CREB binding protein, we propose that the potentiation of VDR-mediated transcription may also be mediated through changes in the phosphorylation of specific VDR coregulators.",
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Integration of hormone signaling in the regulation of human 25(OH)D 3 24-hydroxylase transcription. / Barletta, Frank; Dhawan, Puneet; Christakos, Sylvia.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 286, No. 4 49-4, 01.04.2004.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Integration of hormone signaling in the regulation of human 25(OH)D 3 24-hydroxylase transcription

AU - Barletta, Frank

AU - Dhawan, Puneet

AU - Christakos, Sylvia

PY - 2004/4/1

Y1 - 2004/4/1

N2 - The current study sought to define the molecular mechanisms involved in the cross talk between 1,25-dihydroxyvitamin D3 [1,25(OH) 2D3] and activators of PKC in the regulation of 25(OH)D3 24-hydroxlyase [24(OH)ase]. Transfection of the h24(OH)ase promoter construct [-5,500/-22 luciferase; vitamin D response elements at -294/-274 and -174/-151; AP-1 site at -1,167/-1,160] in vitamin D receptor (VDR)-transfected COS-7 cells resulted in strong activation by 1,25(OH) 2D3. In these cells, cotreatment with the PKC activator TPA and 1,25(OH)2D3 yielded a 27-fold increase in luciferase activity, which was 2- to 3-fold greater than activation obtained with 1,25(OH)2D3 alone (P < 0.05). Similar results were observed using LLCPK-1 kidney cells, suggesting that the previously observed enhancement of 1,25 (OH)2D3-induced renal 24(OH)ase mRNA and activity by PKC activation occurs at the level of transcription. The functional cooperation between PKC activation and VDR was not found to be mediated by the AP-1 site in the h24(OH)ase promoter or by enhanced binding of GRIP or DRIP205 to VDR and was also not due to PKC-mediated phosphorylation of VDR on Ser51. Our study demonstrates that, in LLCPK-1 kidney cells, the PKC enhancement of 1,25(OH)2D 3-stimulated transcription may be due, in part, to an increase in VDR concentration. In addition, inhibitors of the MAPK pathway were found to decrease the TPA enhancement (P < 0.05). Because activation of MAPK has been reported to result in the phosphorylation of SRC-1 and in functional cooperation between SRC-1 and CREB binding protein, we propose that the potentiation of VDR-mediated transcription may also be mediated through changes in the phosphorylation of specific VDR coregulators.

AB - The current study sought to define the molecular mechanisms involved in the cross talk between 1,25-dihydroxyvitamin D3 [1,25(OH) 2D3] and activators of PKC in the regulation of 25(OH)D3 24-hydroxlyase [24(OH)ase]. Transfection of the h24(OH)ase promoter construct [-5,500/-22 luciferase; vitamin D response elements at -294/-274 and -174/-151; AP-1 site at -1,167/-1,160] in vitamin D receptor (VDR)-transfected COS-7 cells resulted in strong activation by 1,25(OH) 2D3. In these cells, cotreatment with the PKC activator TPA and 1,25(OH)2D3 yielded a 27-fold increase in luciferase activity, which was 2- to 3-fold greater than activation obtained with 1,25(OH)2D3 alone (P < 0.05). Similar results were observed using LLCPK-1 kidney cells, suggesting that the previously observed enhancement of 1,25 (OH)2D3-induced renal 24(OH)ase mRNA and activity by PKC activation occurs at the level of transcription. The functional cooperation between PKC activation and VDR was not found to be mediated by the AP-1 site in the h24(OH)ase promoter or by enhanced binding of GRIP or DRIP205 to VDR and was also not due to PKC-mediated phosphorylation of VDR on Ser51. Our study demonstrates that, in LLCPK-1 kidney cells, the PKC enhancement of 1,25(OH)2D 3-stimulated transcription may be due, in part, to an increase in VDR concentration. In addition, inhibitors of the MAPK pathway were found to decrease the TPA enhancement (P < 0.05). Because activation of MAPK has been reported to result in the phosphorylation of SRC-1 and in functional cooperation between SRC-1 and CREB binding protein, we propose that the potentiation of VDR-mediated transcription may also be mediated through changes in the phosphorylation of specific VDR coregulators.

KW - 1,25-dihydroxyvitamin D

KW - Phosphorylation

KW - Protein kinase C

KW - Vitamin D receptor

KW - Vitamin D regulation

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JO - The American journal of physiology

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