Cloning of the human kidney PAH transporter: narrow substrate specificity and regulation by protein kinase C.
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Lu R, Chan BS, Schuster VL
Cloning of the human kidney PAH transporter: narrow substrate specificity and regulation by protein kinase C.
Am J Physiol. 1999 Feb;276(2 Pt 2):F295-303.
- PubMed ID
- 9950961 [ View in PubMed]
- Abstract
Conserved from fish to mammals, renal proximal tubule organic anion secretion plays an important role in drug and xenobiotic elimination. Studies with the model substrate p-aminohippurate (PAH) have suggested that a basolateral PAH/alpha-ketoglutarate exchanger imports diverse organic substrates into the proximal tubule prior to apical secretion. cDNAs encoding PAH transporters have been cloned recently from rat and flounder. Here we report the cloning of a highly similar human PAH transporter (hPAHT) from human kidney. By Northern blot analysis and EST database searching, hPAHT mRNA was detected in kidney and brain. PCR-based monochromosomal somatic cell hybrid mapping placed the hPAHT gene on chromosome 11. When expressed transiently in vitro, hPAHT catalyzed time-dependent and saturable [3H]PAH uptake (Km of approximately 5 microM). Preincubation with unlabeled alpha-ketoglutaric or with glutaric acid stimulated tracer PAH uptake, and preincubation with unlabeled PAH stimulated tracer alpha-ketoglutarate uptake, results that are consistent with PAH/alpha-ketoglutarate exchange. Several structurally diverse organic anions cis-inhibited PAH uptake. Like rat OAT1 organic anion transporter, hPAHT was inhibited by furosemide, indomethacin, probenecid, and alpha-ketoglutarate. Unlike OAT1, hPAHT was not inhibited by prostaglandins or methotrexate (MTX). Moreover, tracer PGE2 and MTX were not transported, indicating that the substrate specificity for transport by hPAHT is not broad. PAH uptake was inhibited by phorbol 12-myristate 13-acetate (PMA) in a dose- and time-dependent fashion, but not by the inactive 4alpha-phorbol-12,13 didecanoate. PMA-induced inhibition was blocked by staurosporine. Thus the protein kinase C-mediated inhibition of basolateral organic anion entry previously reported in intact tubules is likely due, at least in part, to direct modulation of the PAH/alpha-ketoglutarate exchanger.
DrugBank Data that Cites this Article
- Drug Transporters
Drug Transporter Kind Organism Pharmacological Action Actions Aminohippuric acid Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails Benzylpenicillin Solute carrier family 22 member 6 Protein Humans UnknownInhibitorDetails Dinoprostone Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails Fluorescein Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails Furosemide Solute carrier family 22 member 6 Protein Humans UnknownInhibitorInducerDetails Glutaric Acid Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails Indomethacin Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails Methotrexate Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails Probenecid Solute carrier family 22 member 6 Protein Humans UnknownSubstrateInhibitorDetails - Polypeptides
Name UniProt ID Solute carrier family 22 member 6 Q4U2R8 Details