Cloning and characterization of two human polyspecific organic cation transporters.
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Gorboulev V, Ulzheimer JC, Akhoundova A, Ulzheimer-Teuber I, Karbach U, Quester S, Baumann C, Lang F, Busch AE, Koepsell H
Cloning and characterization of two human polyspecific organic cation transporters.
DNA Cell Biol. 1997 Jul;16(7):871-81.
- PubMed ID
- 9260930 [ View in PubMed]
- Abstract
Previously we cloned a polyspecific transporter from rat (rOCT1) that is expressed in renal proximal tubules and hepatocytes and mediates electrogenic uptake of organic cations with different molecular structures. Recently a homologous transporter from rat kidney (rOCT2) was cloned but not characterized in detail. We report cloning and characterization of two homologous transporters from man (hOCT1 and hOCT2) displaying approximately 80% amino acid identity to rOCT1 and rOCT2, respectively. Northern blots showed that hOCT1 is mainly transcribed in liver, while hOCT2 is found in kidney. Using in situ hybridization and immunohistochemistry, expression of hOCT2 was mainly detected in the distal tubule where the transporter is localized at the luminal membrane. After expression in Xenopus laevis oocytes, hOCT1 and hOCT2 mediate tracer influx of N-1-methylnicotinamide (NMN), tetraethylammonium (TEA), and 1-methyl-4-phenylpyridinium (MPP). For cation transport by hOCT2 apparent K(m) and K(i) values were determined in tracer flux measurements. In addition, electrical measurements were performed with voltage-clamped oocytes. Similar to rOCT1, cation transport by hOCT2 was pH independent, electrogenic, and polyspecific; however, the cation specificity was different. In voltage-clamped hOCT2-expressing oocytes, inward currents were induced by superfusion with MPP, TEA, choline, quinine, d-tubocurarine, pancuronium, and cyanine863. Cation transport in distal tubules is indicated for the first time. Here hOCT2 mediates the first step in cation reabsorption. hOCT1 may participate in hepatic excretion of organic cations.
DrugBank Data that Cites this Article
- Drug Transporters
Drug Transporter Kind Organism Pharmacological Action Actions Choline Solute carrier family 22 member 2 Protein Humans UnknownSubstrateInhibitorDetails Choline salicylate Solute carrier family 22 member 2 Protein Humans UnknownSubstrateInhibitorDetails Desipramine Solute carrier family 22 member 2 Protein Humans UnknownInhibitorDetails N-methylnicotinamide Solute carrier family 22 member 2 Protein Humans UnknownNot Available Details Pancuronium Solute carrier family 22 member 2 Protein Humans UnknownNot Available Details Procainamide Solute carrier family 22 member 2 Protein Humans UnknownInhibitorDetails Quinine Solute carrier family 22 member 2 Protein Humans UnknownInhibitorDetails Tubocurarine Solute carrier family 22 member 2 Protein Humans UnknownNot Available Details - Polypeptides
Name UniProt ID Solute carrier family 22 member 2 O15244 Details Solute carrier family 22 member 1 O15245 Details