TY - JOUR T1 - The <em>SLCO1A2</em> Gene, Encoding the Human Organic Anion Transporting Polypeptide 1A2 (OATP1A2), is Transactivated by the Vitamin D Receptor (VDR) JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.112.077909 SP - mol.112.077909 AU - Jyrki J Eloranta AU - Christian Hiller AU - Moritz Juttner AU - Gerd A. Kullak-Ublick Y1 - 2012/01/01 UR - http://molpharm.aspetjournals.org/content/early/2012/04/03/mol.112.077909.abstract N2 - Organic anion transporting polypeptide 1A2 (OATP1A2; gene symbol SLCO1A2) mediates cellular uptake of a wide range of endogenous substrates, as well as of drugs and xenobiotics. OATP1A2 is expressed in several tissues, including apical membranes of small intestinal epithelial cells. Given its role in intestinal drug absorption, a detailed analysis of the mechanisms that regulate SLCO1A2 gene expression is potentially of great pharmacological relevance. We show here that treatment of human intestine-derived Caco-2 cells with vitamin D3 markedly increased endogenous OATP1A2 mRNA and protein levels. Suppressing endogenous vitamin D receptor (VDR) expression by siRNAs significantly reduced this induction. Two alternative promoter regions exist in genomic databases for the SLCO1A2 gene. One putative VDR response elements (VDREs) predicted to efficiently interact with VDR:RXRα was identified in silico within the SLCO1A2 promoter variant 1. This VDRE served as a strong binding site for the recombinant VDR:RXRα heterodimers in vitro, and was potently activated by VDR in the presence of vitamin D3 in heterologous promoter assays. In reporter assays employing native promoter constructs, the SLCO1A2 promoter variant 1 was strongly induced by VDR, and site-directed mutagenesis of a single VDRE within this region abolished this activation. Native VDR:RXRα also interacted with this element both in vitro and within living cells. We have shown that the expression of the SLCO1A2 gene is induced by vitamin D3 at the transcriptional level via VDR. Our results suggest that pharmacological administration of vitamin D3 may allow modulation of intestinal absorption of OATP1A2 transport substrates. ER -