Is Na(+) required for the binding of dopamine, amphetamine, tyramine, and octopamine to the human dopamine transporter?

Naunyn-Schmiedeberg's Archives of Pharmacology
Li-Bin LiMaarten E A Reith

Abstract

The role of Na(+) in the recognition of blockers by the dopamine transporter is accomodated by a model with a cation site that overlaps with the blocker binding domain, and a distal Na(+) site that interacts with this cation site and perhaps with the blocker binding domain itself. The present study addresses the application of this model to the recognition of substrates by the dopamine transporter, focusing on conditions that should reveal a stimulatory effect, if present, of Na(+) on substrate binding. Recognition was studied via the inhibition of binding of [(3)H]WIN 35,428 (2beta-carbomethoxy-3beta-(4-fluorophenyl) [(3)H]tropane), a cocaine analog, to the human dopamine transporter in human embryonic kidney 293 cells. Little or no changes in binding were noted for dopamine, d-amphetamine, p-tyramine, or dl-octopamine by increasing [Na(+)] from 2 mM to 20 mM with co-varying Br(-), both at pH 7.4 and 7.0. In 74-mM Tris-HBr or -HCl, only dopamine and d-amphetamine showed binding increases upon raising Na(+), leveling off with NO(3)(-) or SO(4)(2-) but not Br(-) as anion at approximately 60 mM Na(+), consonant with a partly stimulatory action of Br(-). An Na(+) free, low 5-mM Tris-HEPES buffer was used for studying Na(+) curves ...Continue Reading

Citations

Nov 13, 2003·European Journal of Pharmacology·Jean-Jacques Bonnet
Nov 13, 2003·European Journal of Pharmacology·Nianhang Chen, Maarten E A Reith
Jun 16, 2005·Progress in Neurobiology·David SulzerAurelio Galli
Dec 9, 2003·Journal of Neuroscience Methods·Lijuan C WangMaarten E A Reith
Apr 17, 2004·Journal of Neurochemistry·Nianhang Chen, Maarten E A Reith
Sep 17, 2003·The Journal of Pharmacology and Experimental Therapeutics·Limen Chi, Maarten E A Reith
Jul 16, 2003·Journal of Neurochemistry·Nianhang ChenMaarten E A Reith
Mar 17, 2004·The Journal of Biological Chemistry·Li-Bin LiMaarten E A Reith
Jun 12, 2008·Journal of Chemical Information and Modeling·Henri XhaardMark S Johnson

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