title: Steroid receptor co-activator-1 mediates 1,25-dihydroxyvitamin D(3)-stimulated alkaline phosphatase in human osteosarcoma cells.
abstract: For steroid hormone function to occur, nuclear receptors interact with a series of coactivators including steroid receptor coactivator-1 (SRC-1). The SRC-1 binds the vitamin D receptor (VDR) in the presence of ligand in an activation function 2 (AF-2)-dependent manner. In order to understand the role of this interaction in 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]-mediated gene expression, the level of SRC-1 expression was altered in MG-63 cells. Previous studies had demonstrated that MG-63 cells express the VDR and that 1,25(OH)(2)D(3) regulates expression of alkaline phosphatase (ALP). Analysis of MG-63 cells demonstrated that SRC-1 is expressed. A full-length cDNA coding for SRC-1 was inserted in antisense orientation into an expression vector (anti-SRC-1). The MG-63 cells were transfected with anti-SRC-1 or mock vector and stable transformants were selected. Western blot analysis showed a 95% reduction in SRC-1 protein as compared with mock cells. We determined the effect of normal and reduced SRC-1 expression in MG-63 cells on 1,25(OH)(2)D(3)-mediated stimulation of ALP. Whereas 10(-8) M 1,25(OH)(2)D(3) produced a 3.6-fold stimulation in ALP in mock cells expressing normal levels of SRC-1, it did not alter ALP in cells expressing reduced levels of SRC-1. Thus, SRC-1 is required for 1,25(OH)(2)D(3)-mediated gene expression of ALP by human MG-63 cells.
authors.affiliation: Department of Medicine, Division of Bone and Mineral Metabolism, Medical University of South Carolina, 114 Doughty Street, PO Box 250775, Charleston, South Carolina 29425, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Gill
authors.forename: N H
authors.initials: NH
authors.lastname: Bell
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D005786:Gene Expression Regulation; D051548:Histone Acetyltransferases; D006801:Humans; D056920:Nuclear Receptor Coactivator 1; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000378:metabolism; D011987:Receptors, Steroid / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D015534:Trans-Activators; D014157:Transcription Factors; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1; D000469:Alkaline Phosphatase; D002117:Calcitriol