Abstract
In the two major target tissues of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) action, intestine and kidney, one of the most pronounced effects of 1,25(OH)2D3 known is the induction of the calcium-binding protein, calbindin, the first identified target of 1,25(OH)2D3 action. This chapter reviews the chemistry, localization, proposed functional significance, and regulation of these calcium-binding proteins. In addition, it provides insight into the information obtained by studying these proteins concerning the multiple actions of the vitamin D endocrine system and the basic molecular mechanism of 1,25(OH)2D3 action. Findings indicating that calbindins can be regulated by a number of different hormones and factors are also reviewed. The study of the molecular interactions of several members of the steroid hormone–retinoic acid family as well as the role of signal transduction pathways in the regulation of calbindin-D may be applicable to the regulation of other targets of 1,25 (OH)2D3 action. Elucidation of multiple factors and interactions regulating 1,25(OH)2D3 target genes should result in novel insights related to tissue-specific molecular mechanisms involved in calcium homeostasis.