Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
XB-ART-49277
J Biol Chem 2014 Sep 12;28937:25764-73. doi: 10.1074/jbc.M114.574269.
Show Gene links Show Anatomy links

The second sodium site in the dopamine transporter controls cation permeation and is regulated by chloride.

Borre L , Andreassen TF , Shi L , Weinstein H , Gether U .


???displayArticle.abstract???
The dopamine transporter (DAT) belongs to the family of neurotransmitter:sodium symporters and controls dopamine (DA) homeostasis by mediating Na(+)- and Cl(-)-dependent reuptake of DA. Here we used two-electrode voltage clamp measurements in Xenopus oocytes together with targeted mutagenesis to investigate the mechanistic relationship between DAT ion binding sites and transporter conductances. In Li(+), DAT displayed a cocaine-sensitive cation leak current ∼10-fold larger than the substrate-induced current in Na(+). Mutation of Na(+) coordinating residues in the first (Na1) and second (Na2) binding sites suggested that the Li(+) leak depends on Li(+) interaction with Na2 rather than Na1. DA caused a marked inhibition of the Li(+) leak, consistent with the ability of the substrate to interact with the Li(+)-occupied state of the transporter. The leak current in Li(+) was also potently inhibited by low millimolar concentrations of Na(+), which according to our mutational data conceivably depended on high affinity binding to Na1. The Li(+) leak was further regulated by Cl(-) that most likely increases Li(+) permeation by allosterically lowering Na2 affinity. Interestingly, mutational lowering of Na2 affinity by substituting Asp-420 with asparagine dramatically increased cation permeability in Na(+) to a level higher than seen in Li(+). In addition to reveal a functional link between the bound Cl(-) and the cation bound in the Na2 site, the data support a key role of Na2 in determining cation permeability of the transporter and thereby possibly in regulating the opening probability of the inner gate.

???displayArticle.pubmedLink??? 25063810
???displayArticle.pmcLink??? PMC4162178
???displayArticle.link??? J Biol Chem
???displayArticle.grants??? [+]

Species referenced: Xenopus laevis
Genes referenced: slc6a3

References [+] :
Beuming, The binding sites for cocaine and dopamine in the dopamine transporter overlap. 2008, Pubmed