Structure and regulation of the rat 1,25-dihydroxyvitamin D3 receptor.

Abstract

Complementary DNA clones encoding the entire rat 1,25-dihydroxyvitamin D3 receptor were isolated, and the total 423-amino acid sequence was deduced. The amino acid sequence of the rat receptor is similar but not identical to the reported human receptor sequence. The cysteine-rich DNA-binding domain is completely conserved and the steroidbinding domain is >93% conserved between rat and human. The cDNA was used as a probe in blot analysis of polyadenylylated RNA to show that the 1,25-dihydroxyvitamin D3 receptor mRNA is a single 4.4-kilobase mRNA that is expressed in intestine and kidney, slightly expressed in heart, and not detectable in liver and spleen. The receptor mRNA concentration is markedly increased during development of the rat intestine between day 14 and day 21, in accord with previous results obtained by measurement of receptor concentration by ligand binding or immunoblotting.The primary function of 1,25-dihydroxyvitamin D3, the active form of vitamin D, is to increase serum calcium and phosphorus (1, 2). The action of 1,25-dihydroxyvitamin D3 is mediated through an intracellular receptor protein that is present in target tissues at a very low concentration, -0.001% (3,4). This receptor binds 1,25-dihydroxyvitamin D3 and then interacts with specific sites in chromatin, resulting in specific gene transcription. These gene products then effect calcium transport in the intestine and cause calcium mobilization from bone and calcium reabsorption in kidney (1,2).The importance of a functional receptor is clearly demonstrated through the disease vitamin D-dependent rickets type II (5, 6). Patients with this disease suffer impaired calcium absorption despite high circulating levels of 1,25-dihydroxyvitamin D3. A defective receptor has been reported to be the cause in at least some kindrids (7).Monoclonal antibodies against the receptor have been isolated (8). The receptor has a molecular weight of 55,000 when identified by these antibodies on an immunoblot (9, 10). A partial cDNA for the rat receptor was isolated by screening a kidney Agtll expression library with these antibodies (11). When expressed in Escherichia coli, this cDNA produced a region of the receptor capable of specifically binding 1,25-dihydroxyvitamin D3, confirming the authenticity of the clone. In addition, a partial cDNA for the avian receptor (12) and the complete cDNA for the human receptor (13) have been sequenced.We report here the nucleotide sequence and the predicted amino acid sequence for the complete rat receptor. § Comparison of the rat sequence to the human sequence shows that the receptor has remained highly conserved between the two species. The cloned cDNA was used to study the regulation of receptor gene transcription. A single 4.4-kilobase (kb) receptor mRNA is expressed in the intestine, kidney, and heart of adult rats. This mRNA is not detectable in preparations isolated from intestine of 14-day-old rat, but by day 21, it has increased substantially.MATERIALS AND METHODS RNA Isolation. RNA was prepared by the pr...

The E75 ecdysone-inducible gene responsible for the 75B early puff in Drosophila encodes two new members of the steroid receptor superfamily.

“…(hGR) Human glucocorticoid receptor (Hollenberg et al 1985); {hER) human estrogen receptor Greene et al 1986); (cERBA) chicken c-erbA thyroid hormone receptor (Sap et al 1986); {rVDR) rat vitamin D receptor (Burmester et al 1988); (hRAR) human retinoic acid receptor (Giguere et al 1987); ( which we call El, E2, and E3. The E1 subregion is the most highly conserved and corresponds to a region shown by in vitro mutagenesis to be essential for steroid binding and steroid-dependent trans-activation (Giguere et al 1986;Danielson et al 1987}.…”

The Nuclear Vitamin D Receptor: Biological and Molecular Regulatory Properties Revealed

“…Shown are sequences from human (Hu), (147) mouse (Mus musculus, abbreviated Ms), (149) chicken (Gallus gallus, denoted Ch), (1,150,151) and Xenopus laevis (Xl). (18) Numbering is for the hVDR as published by Baker et al (147) Not shown are sequences from rat (148) and Japanese quail, (151) which are similar to the mouse and chicken, respectively. Alternative translation start sites for chicken (Ch) or human (Hu) mRNAs are indicated by arrows.…”

“…To date, VDR cDNAs have been cloned from six species, namely human, (147) rat, (148) mouse, (149) chicken, (1,150,151) Japanese quail, (151) and frog (Xenopus laevis). (18) As illustrated in Fig.…”

The molecular basis of hereditary 1,25-dihydroxyvitamin D3 resistant rickets in seven related families.

“…Like the other members of this receptor family, VDR is comprised of at least two functional domains, a steroid hormone-binding domain and a DNA-binding domain (17)(18)(19)(20)(21)(22)(23). The steroid-binding domain stretches from amino acid 182 to the COOH-terminus at amino acid 427 and provides the molecule with high affinity, steroid-specific recognition of the 1,25(OH)2D3 metabolite.…”

“…1,25(OH)2D3 binding to the steroid-binding domain of the receptor "activates" the VDR to a form with high affinity for DNA. The DNA-binding domain of the VDR then binds to a vitamin D response element in the regulatory region of target genes to modulate transcription of responsive genes and thereby mediates hormone action (17)(18)(19)(20)(21)(22)(23).Progress to elucidate the molecular basis of HVDRR began with the demonstration that rodent skin possessed VDR (24, 25) and that cultured human dermal fibroblasts derived from skin biopsies could be used as a model system for the study of the VDR from patients (26). It was soon demonstrated that defects in the VDR were the likely cause of the HVDRR syndrome (5) and that different families exhibited different defects (5-16).…”