A run for a membrane vitamin D receptor

1,25-Dihydroxyvitamin D(3) is the hormonally active form of vitamin D(3). Its involvement in regulation of calcium and phosphate homeostasis as well as in differentiation and regulation of the immune system is well documented. Extensive data indicate that there are two mechanisms of the molecular mode-of-action of 1,25-dihydroxyvitamin D(3). One involves the activation of nuclear vitamin D receptor (nVDR) and transcriptional regulation of many vitamin D-responsive genes. The other involves activation of nongenomic signal transduction pathways in target cells. This second mechanism is likely to engage a membrane vitamin D receptor (mVDR). Recently discovered 64.5 kDa protein from chick epithelium, which specifically binds 1,25-dihydroxyvitamin D(3) and is responsible for some rapid cellular actions of 1,25-dihydroxyvitamin D(3) is a candidate for mVDR. This article provides a brief description of a search for a putative mVDR that lasted for over a decade.