The energy dependence of γ-aminobutyric acid (GABA) uptake was characterized in rat brain synaptic vesicles and in proteoliposomes reconstituted with a new procedure from vesicular detergent extracts. The proteoliposomes displayed high ATP-dependent GABA uptake activity with properties virtually identical to those of intact vesicles. GABA uptake was similar at chloride concentrations of 0 and 150 mM, i.e. conditions under which either the membrane potential (ΔΨ) or the pH difference (ΔpH) predominates. ΔΨ was gradually dissipated by increasing the concentration of SCN-. GABA uptake was reduced by 10 mM SCN-, showing less sensitivity to ΔΨ reduction than glutamate uptake but more than dopamine uptake. Dissipation of ΔPh with NH4+ abolished GABA uptake at pH 7.3, whereas no significant inhibition occurred at pH 6.5. In contrast, dopamine uptake was inhibited more strongly, even at pH 6.5, and glutamate uptake was not reduced in either condition. We conclude that GABA uptake is driven by both components of the proton electrochemical gradient, ΔpH and ΔΨ, and that this is different from the uptake of both dopamine and glutamate, which is more strongly dependent on ΔpH and ΔΨ, respectively. Thus, our data suggest that GABA uptake is electrogenic and occurs in exchange for protons.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Biological Chemistry|
|State||Published - Feb 5 1990|
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