Synthesis of a 1α-C-methyl analogue of 25-hydroxyvitamin D3: interaction with a mutant vitamin D receptor Arg274Leu

The Centennial Collection of VDR Ligands: Metabolites, Analogs, Hybrids and Non-Secosteroidal Ligands

Since the discovery of vitamin D a century ago, a great number of metabolites, analogs, hybrids and nonsteroidal VDR ligands have been developed. An enormous effort has been made to synthesize compounds which present beneficial properties while attaining lower calcium serum levels than calcitriol. This structural review covers VDR ligands published to date.

Synthetic Chemical Probes That Dissect Vitamin D Activities

Vitamin D₃ metabolites are capable of controlling gene expression in mammalian cells through two independent pathways: vitamin D receptor (VDR) and sterol regulatory element-binding protein (SREBP) pathways. In the present study, we dissect the complex biological activity of vitamin D by designing synthetic vitamin D₃ analogs specific for VDR or SREBP pathway, i.e., a VDR activator that lacks SREBP inhibitory activity, or an SREBP inhibitor devoid of VDR activity. These synthetic vitamin D probes permitted identification of one of the vitamin D-responsive genes, Soat1, as an SREBP-suppressed gene. The chemical probes developed in the present study may prove useful in dissecting the intricate interplay of vitamin D actions, thereby providing insights into how vitamin D target genes are regulated.

Vitamin D and Its Synthetic Analogs

For many individuals, in particular during winter, supplementation with the secosteroid vitamin D₃ is essential for the prevention of bone disorders, muscle weakness, autoimmune diseases, and possibly also different types of cancer. Vitamin D₃ acts via its metabolite 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] as potent agonist of the transcription factor vitamin D receptor (VDR). Thus, vitamin D directly affects chromatin structure and gene regulation at thousands of genomic loci, i.e., the epigenome and transcriptome of its target tissues. Modifications of 1,25(OH)₂D₃ at its side-chain, A-ring, triene system, or C-ring, alone and in combination, as well as nonsteroidal mimics provided numerous potent VDR agonists and some antagonists. The nearly 150 crystal structures of VDR’s ligand-binding domain with various vitamin D compounds allow a detailed molecular understanding of their action. This review discusses the most important vitamin D analogs presented during the past 10 years and molecular insight derived from new structural information on the VDR protein.

Novel screening system for high-affinity ligand of heredity vitamin D-resistant rickets-associated vitamin D receptor mutant R274L using bioluminescent sensor

Hereditary vitamin D-resistant rickets (HVDRR) is caused by mutations in the vitamin D receptor (VDR) gene. Arg274 located in the ligand binding domain (LBD) of VDR is responsible for anchoring 1α,25-dihydroxyvitamin D3 (1α,25(OH)₂D₃) by forming a hydrogen bond with the 1α-hydroxyl group of 1α,25(OH)₂D_3. The Arg274Leu (R274L) mutation identified in patients with HVDRR causes a 1000-fold decrease in the affinity for 1α,25(OH)₂D₃, and dramatically reduces vitamin D- related gene expression. Recently, we successfully constructed fusion proteins consisting of split-luciferase and LBD of the VDR. The chimeric protein LucC-LBD-LucN, which displays the C-terminal domain of luciferase (LucC) at its N-terminus, can detect and discriminate between VDR agonists and antagonists. The LucC-LBD (R274L)-LucN was constructed to screen high-affinity ligands for the mutant VDR (R274L). Of the 33 vitamin D analogs, 5 showed much higher affinities for the mutant VDR (R274L) than 1α,25(OH)₂D₃, and 2α-[2-(tetrazol-2-yl)ethyl]-1α,25-(OH)₂D₃ showed the highest affinity. These compounds might be potential therapeutics for HVDRR caused by the mutant VDR (R274L).