Abstract
Organic anion transporters (OATs) are anion exchangers that transport small hydrophilic anions and diuretics, antibiotics, nonsteroidal anti-inflammatory drugs, antiviral nucleoside analogs, and antitumor drugs across membrane barriers of epithelia of diverse organs. Three OATs are present in human liver: OAT2, OAT5, and OAT7. Given that hepatocyte nuclear factor-1α (HNF-1α) has previously been shown to regulate the expression of several hepatocellular transporter genes, we investigated whether the liver-specific human OAT genes are also regulated by HNF-1α. Short interfering RNAs targeting HNF-1α reduced endogenous expression of OAT5 and OAT7, but not OAT2, in human liver-derived Huh7 cells. Luciferase reporter gene constructs containing the OAT5 (SLC22A10) and OAT7 (SLC22A9) promoter regions were transactivated by HNF-1α in HepG2 cells. Two putative HNF-1α binding elements in the proximal OAT5 promoter, located at nucleotides −68/−56 and −173/−160, and one element in the OAT7 promoter, located at nucleotides −14/−2 relative to the transcription start site, were shown to bind HNF-1α in electromobility shift assays, and these promoter regions also interacted with HNF-1α in chromatin immunoprecipitation assays. A correlation between HNF-1α and OAT5 (r = 0.134, P < 0.05) or OAT7 (r = 0.461, P < 0.001) mRNA expression levels in surgical liver biopsies from 75 patients further supported an important role of HNF-1α in the regulation of OAT gene expression.
Footnotes
This study was supported by the Swiss National Science Foundation [Grant 320030_120463/1]; the Novartis Foundation for Biomedical Research, the Center of Clinical Research at the University Hospital Zurich; the Austrian Science Fund (Fonds zur Förderung der wissenschaftlichen Forschung) [Grant P19893-B05]; the Land Salzburg; and the Verein für Medizinische Forschung Salzburg.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.065201.
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ABBREVIATIONS:
- TMD
- transmembrane domain
- OAT
- organic anion transporter
- SLC
- solute carrier
- HNF
- hepatocyte nuclear factor
- EMSA
- electromobility shift assay
- ChIP
- chromatin immunoprecipitation
- siRNA
- small interfering RNA
- PCR
- polymerase chain reaction
- PBS-T
- phosphate-buffered saline–Tween 20
- bp
- base pair(s).
- Received March 31, 2010.
- Accepted September 9, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
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