Regulation of renal parathyroid hormone receptor expression by 1, 25-dihydroxyvitamin D3 and retinoic acid.
The renal distal convoluted tubule (DCT) is the major site of parathyroid hormone (PTH) and 1alpha,25-dihydroxyvitamin D3 [1, 25(OH)2D3]-regulated calcium absorption. 1,25(OH)2D3 augments PTH-stimulated calcium transport by DCT cells, while having no effect of its own. 1,25(OH)2D3 mediates its effects on gene expression by binding to a nuclear vitamin-D receptor (VDR), which then associates with the retinoid-X receptor (RXR) as a heterodimer. We studied the effects of 1,25(OH)2D3, 9-cis- and all-trans-retinoic acid on PTH/PTHrP receptor expression. mRNAs for the PTH/PTHrP, VDR, and RXR receptors were detected in immortalized DCT cells by reverse transcriptase-polymerase chain reaction. Changes in PTH/PTHrP receptor mRNA expression were quantified by slot blot hybridization. 1,25(OH)2D3 maximally increased PTH/PTHrP receptor mRNA levels by 70%. The stimulation was specific since 1,25(OH)2D3 treatment had no effect on the expression of adrenergic receptor or Na+/H+ exchanger mRNA levels. Likewise, the inactive form, 25(OH)2D3 had no effect on PTH/PTHrP receptor mRNA expression. In combination with the putative RXR ligand, 9-cis-retinoic acid, 1,25(OH)2D3 increased PTH/PTHrP receptor mRNA levels 4-fold. 9-cis-Retinoic acid had no effect of its own on steady-state PTH/PTHrP receptor mRNA expression. The putative ligand for the retinoic acid receptor, all-trans-retinoic acid, increased PTH/PTHrP receptor mRNA expression alone and in combination with 1,25(OH)2D3. 9-cis-Retinoic acid alone, and in combination with 1,25(OH)2D3, also increased specific PTH/PTHrP receptor binding to plasma membranes isolated from DCT cells. These results indicate that 1,25(OH)2D3 upregulated PTH/PTHrP receptor expression at both mRNA and protein levels in a manner consistent with VDR/RXR heterodimers transactivating the PTH/PTHrP receptor gene by binding a vitamin D response element in the PTH/PTHrP gene.
Sneddon
W B
WB
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, N.H., USA.
Barry
E L
EL
Coutermarsh
B A
BA
Gesek
F A
FA
Liu
F
F
Friedman
P A
PA
D000077556:Alitretinoin; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects*; D007686:Kidney Tubules, Distal / Q000187:drug effects*; D051379:Mice; D010281:Parathyroid Hormone; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D044168:Receptor, Parathyroid Hormone, Type 1; D018167:Receptors, Calcitriol / Q000235:genetics; D018016:Receptors, Parathyroid Hormone / Q000235:genetics*; D018168:Receptors, Retinoic Acid / Q000235:genetics; D047488:Retinoid X Receptors; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology
D010281:Parathyroid Hormone; D012333:RNA, Messenger; D044168:Receptor, Parathyroid Hormone, Type 1; D018167:Receptors, Calcitriol; D018016:Receptors, Parathyroid Hormone; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors; D014284:Triiodothyronine; D000077556:Alitretinoin; D014212:Tretinoin; D002117:Calcitriol