Phosphate regulates osteopontin gene transcription.
Extracellular inorganic phosphate (ePi) is a key regulator of cementoblast behavior, both in vivo and in vitro, and results in a marked increase in osteopontin expression in vitro. To examine the molecular mechanisms involved in ePi induction of osteopontin gene expression, we transfected a series of osteopontin promoter-luciferase constructs into OCCM-30 cementoblasts. Our results demonstrate that ePi can directly induce osteopontin gene transcription. The region responsive to ePi signaling was localized to a 53-bp region of the promoter between -1454 and -1401 that contains a glucocorticoid response element (GRE). Mutation of the GRE abolished the ePi response, suggesting that glucocorticoid receptor (GR) signaling is required for ePi-mediated transcription. In addition, treatment of cells with the GR antagonist RU-486 (Mifepristone) prevented promoter activation by ePi. The results presented support a model demonstrating that inorganic phosphate regulates OPN gene transcription in cementoblasts through a pathway that requires a functional GR.
Fatherazi
S
S
Department of Oral Biology, University of Washington, Seattle, WA 98195-7132, USA.
Matsa-Dunn
D
D
Foster
B L
BL
Rutherford
R B
RB
Somerman
M J
MJ
Presland
R B
RB
D000818:Animals; D020029:Base Pairing / Q000235:genetics; D002478:Cells, Cultured; D003739:Dental Cementum / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005938:Glucocorticoids / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology; D051379:Mice; D015735:Mifepristone / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D053495:Osteopontin / Q000235:genetics*; D010710:Phosphates / Q000494:pharmacology; D010758:Phosphorus / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011965:Receptors, Glucocorticoid / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics*; D014162:Transfection / Q000379:methods; D015854:Up-Regulation / Q000235:genetics
D005938:Glucocorticoids; D006727:Hormone Antagonists; D010710:Phosphates; D011965:Receptors, Glucocorticoid; D053495:Osteopontin; D010758:Phosphorus; D015735:Mifepristone; D003907:Dexamethasone