Up-regulation of the vitamin D receptor in response to 1,25-dihydroxyvitamin D3 results from ligand-induced stabilization.
Several studies have shown that the 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) receptor protein levels increase in response to 1,25-(OH)2D3. We have studied the mechanism of this regulation in both mouse fibroblasts and rat intestinal epithelial cells. Cell extracts and total RNA were prepared at varying times after addition of 1,25-(OH)2D3. The 1,25-(OH)2D3 receptor protein levels, measured using an immunoradiometric assay, rose significantly 2-3 h posttreatment and had risen 3-fold at 8 h. Concurrently, the 1,25-(OH)2D3 receptor mRNA content, measured using a ribonuclease protection assay, was not altered by 1,25-(OH)2D3 during this time. In cycloheximide-blocked cells, the administration of 1,25-(OH)2D3 markedly reduced the degradation rate of previously formed receptor. The 1,25-(OH)2D3 receptor protein half-life was determined as 4 h in the absence of 1,25-(OH)2D3 and increased to at least 8 h in the presence of 1,25-(OH)2D3. We also measured the 1,25-(OH)2D3 receptor mRNA levels in the duodena and kidney of vitamin D-deficient rats after a single 150-pmol injection of 1,25-(OH)2D3. Again, we found that 1,25-(OH)2D3 receptor mRNA levels were not changed in these tissues after 1,25-(OH)2D3 treatment. Therefore, the elevation of the 1,25-(OH)2D3 receptor protein following 1,25-(OH)2D3 administration is apparently the result of increased receptor protein lifetime and not increased transcription.
Wiese
R J
RJ
College of Agricultural and Life Sciences, University of Wisconsin-Madison, Department of Biochemistry 53706.
Uhland-Smith
A
A
Ross
T K
TK
Prahl
J M
JM
DeLuca
H F
HF
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line; D004386:Duodenum / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008297:Male; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism; D014158:Transcription, Genetic; D015854:Up-Regulation; D014808:Vitamin D Deficiency / Q000378:metabolism
D008024:Ligands; D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D012260:Ribonucleases; D002117:Calcitriol