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The SLCO1A2 Gene, Encoding the Human Organic Anion Transporting Polypeptide 1A2 (OATP1A2), is Transactivated by the Vitamin D Receptor (VDR)


Eloranta, Jyrki J; Hiller, Christian; Juttner, Moritz; Kullak-Ublick, Gerd A (2012). The SLCO1A2 Gene, Encoding the Human Organic Anion Transporting Polypeptide 1A2 (OATP1A2), is Transactivated by the Vitamin D Receptor (VDR). Molecular Pharmacology, 82(1):37-46.

Abstract

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 D(3) 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 D(3) 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 D(3) at the transcriptional level via VDR. Our results suggest that pharmacological administration of vitamin D(3) may allow modulation of intestinal absorption of OATP1A2 transport substrates.

Abstract

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 D(3) 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 D(3) 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 D(3) at the transcriptional level via VDR. Our results suggest that pharmacological administration of vitamin D(3) may allow modulation of intestinal absorption of OATP1A2 transport substrates.

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Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Center for Integrative Human Physiology
04 Faculty of Medicine > University Hospital Zurich > Clinic for Clinical Pharmacology and Toxicology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Date:2012
Deposited On:30 Apr 2012 12:31
Last Modified:05 Apr 2016 15:47
Publisher:American Society for Pharmacology and Experimental Therapeutics
ISSN:0026-895X
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1124/mol.112.077909
PubMed ID:22474172

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