title: Localization and functional characterization of the rat Oatp4c1 transporter in an in vitro cell system and rat tissues.
abstract: The organic anion transporting polypeptide 4c1 (Oatp4c1) was previously identified as a novel uptake transporter predominantly expressed at the basolateral membrane in the rat kidney proximal tubules. Its functional role was suggested to be a vectorial transport partner of an apically-expressed efflux transporter for the efficient translocation of physiological substrates into urine, some of which were suggested to be uremic toxins. However, our in vitro studies with MDCKII cells showed that upon transfection rat Oatp4c1 polarizes to the apical membrane. In this report, we validated the trafficking and function of Oatp4c1 in polarized cell systems as well as its subcellular localization in rat kidney. Using several complementary biochemical, molecular and proteomic methods as well as antibodies amenable to immunohistochemistry, immunofluorescence, and immunobloting we investigated the expression pattern of Oatp4c1 in polarized cell systems and in the rat kidney. Collectively, these data demonstrate that rat Oatp4c1 traffics to the apical cell surface of polarized epithelium and localizes primarily in the proximal straight tubules, the S3 fraction of the nephron. Drug uptake studies in Oatp4c1-overexpressing cells demonstrated that Oatp4c1-mediated estrone-3-sulfate (E3S) uptake was pH-dependent and ATP-independent. These data definitively demonstrate the subcellular localization and histological location of Oatp4c1 and provide additional functional evidence that reconciles expression-function reports found in the literature.
authors: Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky.
authors: Kuei-Ling
authors: KL
authors: Kuo
authors: Haining
authors: H
authors: Zhu
authors: Patrick J
authors: PJ
authors: McNamara
authors: Markos
authors: M
authors: Leggas
mesh_terms: D000818:Animals; D002460:Cell Line; D016764:Cell Polarity; D004285:Dogs; D004970:Estrone / Q000031:analogs & derivatives / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism; D009928:Organ Specificity; D027361:Organic Anion Transporters / Q000378:metabolism*; D016612:Paraffin Embedding; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013347:Subcellular Fractions / Q000378:metabolism; D016707:Tissue Fixation; D014511:Uremia / Q000378:metabolism
chemical_list: D027361:Organic Anion Transporters; C484531:organic anion transporting polypeptide 4C1, rat; D004970:Estrone; C017296:estrone sulfate