Stabilization of the vitamin D receptor in rat osteosarcoma cells through the action of 1,25-dihydroxyvitamin D3.
A regulatory mechanism for the vitamin D receptor (VDR) in rat osteosarcoma cells (ROS 17/2.8) is stabilization of the receptor through binding of its ligand, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. Increased transcription of the gene encoding VDR does not occur upon treatment of these osteoblast-like cells with 1,25-(OH)2D3. When 10 nM 1,25-(OH)2D3 was administered to confluent cultures of ROS 17/2.8 cells, no change in receptor mRNA was detected, as measured by a ribonuclease protection assay. VDR abundance was measured using an immunoradiometric assay at varying time points within a 24-h period after 1,25-(OH)2D3 treatment. Receptor protein levels increased rapidly and continued to rise over 24 h. By 2 h, the level of receptor increased 2.5-fold, achieving a maximum level of 8-fold above the baseline at 18 h. The half-life of the receptor protein is 2 h in the absence of hormone, as determined by blockage of translation in cycloheximide-treated cells. In the presence of hormone, however, receptor levels were unchanged for at least 6 h. The administration of 1,25-(OH)2D3 stabilizes the receptor, thereby resulting in its accumulation in ROS 17/2.8 cells.
Arbour
N C
NC
College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison 53706.
Prahl
J M
JM
DeLuca
H F
HF
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002117:Calcitriol / Q000378:metabolism / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology; D004355:Drug Stability; D015592:Immunoradiometric Assay; D007700:Kinetics; D012516:Osteosarcoma / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D003513:Cycloheximide; D002117:Calcitriol