The function of vitamin D receptor in vitamin D action

Vitamin D has roles in a variety of biological actions such as calcium homeostasis, cell proliferation and cell differentiation to many target tissues. Most of these biological actions of vitamin D are now considered to be exerted through the nuclear vitamin D receptor (VDR)-mediated control of target genes. VDR belongs to the nuclear hormone receptor superfamily and acts as a ligand-inducible transcription factor. For the ligand-induced transactivation of VDR, coactivator complexes have recently been shown to be essential. The function of VDR as a ligand-induced transcription factor is overviewed, and the phenotype of VDR gene knock-out mice and the VDR-mediated transcriptional and negative regulation of the key enzyme in vitamin D biosynthesis are also described, based mainly on our recent findings, to gain a better understanding of the function of VDR in the transcriptional control of vitamin D target genes.