J Biol Chem, Vol. 274, Issue 3, 1519-1524, January 15, 1999
Heterologous Expression and Functional Characterization of a
Mouse Renal Organic Anion Transporter in Mammalian Cells
Kogo
Kuze,
Peter
Graves,
Amy
Leahy,
Patricia
Wilson,
Heidi
Stuhlmann, and
Guofeng
You
From the Department of Medicine, The Mount Sinai School of
Medicine, New York, New York 10029
Organic anion transporters play an
essential role in eliminating a wide range of organic anions including
endogenous compounds, xenobiotics, and their metabolites from kidney,
thereby preventing their potentially toxic effects within the body. The
goal of this study was to extend our previous study on the functional
characterization and post-translational modification of a mouse kidney
organic anion transporter (mOAT), in a mammalian cell system, COS-7
cells. The transporter-mediated p-aminohippurate (PAH)
uptake was saturable, probenecid-sensitive, and inhibited by a wide
range of organic anions including vitamins, anti-hypertensive drugs,
anti-tumor drugs, and anti-inflammatory drugs. Tunicamycin, an
inhibitor of asparagine-linked glycosylation, significantly inhibited
the transport activity. Immunofluorescence provided evidence that most
of the protein remained in the intracellular compartment in
tunicamycin-treated cells. Diethyl pyrocarbonate (DEPC), a histidine
residue-specific reagent, completely blocked PAH transport. The
inhibitory effect by DEPC was significantly protected (90%) by
pretreating the cells with excess unlabeled PAH, suggesting that the
histidine residues may be close to the PAH binding sites. Finally,
in situ mRNA localization was studied in postnatal
mouse kidney. The expression was observed in proximal tubules
throughout development. We conclude that COS-7 cells may be useful in
pharmacological and molecular biological studies of this carrier. The
carbohydrate moieties are necessary for the proper trafficking of mOAT
to the plasma membrane, and histidine residues appear to be important for the transport function.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.