Expression of the renal Na+/dicarboxylate cotransporter, NaDC-1, in COS-7 cells.
The cloned rabbit renal Na+/dicarboxylate cotransporter, NaDC-1, was transiently expressed in the mammalian monkey kidney cell line, COS-7. Cells transfected with the plasmid pSV-201, containing the cDNA for the Na+/dicarboxylate cotransporter, expressed sodium-dependent succinate and citrate transport after 48 h. Cells transfected with control plasmid, pSV-SPORT, did not express sodium-dependent transport of succinate or citrate. The transport of succinate in cells expressing NaDC-1 was inhibited by di-and tricarboxylic acids, but not by monocarboxylic acids. Sodium-dependent transport of succinate was insensitive to changes in pH, while sodium-dependent citrate transport was stimulated by acidic pH. Succinate transport by NaDC-1 was saturable with an apparent Michaelis constant, Km, around 0.5 mM. The kinetics of sodium activation of succinate transport by NaDC-1 were sigmoidal, with an apparent Hill coefficient of 2.9, indicating that three sodium ions are involved in the transport of each succinate. Succinate transport by NaDC-1 was inhibited by lithium. The functional characteristics of NaDC-1 expressed in COS-7 cells correspond to those of the Na+/dicarboxylate cotransporter of the apical membrane of the renal proximal tubule.
Pajor
A M
AM
Department of Physiology, University of Arizona, College of Medicine, Tuscon, AZ 85724, USA.
Valmonte
H G
HG
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics*; D002411:Cation Exchange Resins; D002460:Cell Line; D002794:Choline / Q000494:pharmacology; D006224:Cricetinae; D018076:DNA, Complementary / Q000302:isolation & purification; D029382:Dicarboxylic Acid Transporters; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007668:Kidney / Q000166:cytology*; D008055:Lipids; D008565:Membrane Proteins / Q000235:genetics*; D029363:Organic Anion Transporters, Sodium-Dependent; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D013379:Substrate Specificity; D013386:Succinates / Q000493:pharmacokinetics; D019802:Succinic Acid; D027981:Symporters; D013997:Time Factors; D014162:Transfection; D014981:Xenopus
D002352:Carrier Proteins; D002411:Cation Exchange Resins; D018076:DNA, Complementary; D029382:Dicarboxylic Acid Transporters; D007202:Indicators and Reagents; D008055:Lipids; C086724:Lipofectamine; D008565:Membrane Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; C092524:SLC13A2 protein, human; D013386:Succinates; D027981:Symporters; D012964:Sodium; D019802:Succinic Acid; D002794:Choline