Zinc Potentiates an Uncoupled Anion Conductance Associated with the Dopamine Transporter
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Zinc Potentiates an Uncoupled Anion Conductance Associated with the Dopamine Transporter. / Meinild, Anne-Kristine; Sitte, Harald H; Gether, Ulrik.
In: Journal of Biological Chemistry, Vol. 279, No. 48, 2004, p. 49671-9.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Zinc Potentiates an Uncoupled Anion Conductance Associated with the Dopamine Transporter
AU - Meinild, Anne-Kristine
AU - Sitte, Harald H
AU - Gether, Ulrik
N1 - Keywords: Animals; Anions; Dopamine Plasma Membrane Transport Proteins; Kinetics; Membrane Glycoproteins; Membrane Potentials; Membrane Transport Proteins; Mutation; Nerve Tissue Proteins; Time Factors; Tritium; Xenopus; Zinc
PY - 2004
Y1 - 2004
N2 - Binding of Zn(2+) to an endogenous binding site in the dopamine transporter (DAT) leads to inhibition of dopamine (DA) uptake and enhancement of carrier-mediated substrate efflux. To elucidate the molecular mechanism for this dual effect, we expressed the DAT and selected mutants in Xenopus laevis oocytes and applied the two-electrode voltage clamp technique together with substrate flux studies employing radiolabeled tracers. Under voltage clamp conditions we found that Zn(2+) (10 mum) enhanced the current induced by both DA and amphetamine. This was not accompanied by a change in the uptake rate but by a marked increase in the charge/DA flux coupling ratio as assessed from concomitant measurements of [(3)H]DA uptake and currents in voltage-clamped oocytes. These data suggest that Zn(2+) facilitates an uncoupled ion conductance mediated by DAT. Whereas this required substrate in the wild type (WT), we observed that Zn(2+) by itself activated such a conductance in a previously described mutant (Y335A). This signifies that the conductance is not strictly dependent on an active transport process. Ion substitution experiments in Y335A, as well as in WT, indicated that the uncoupled conductance activated by Zn(2+) was mainly carried by Cl(-). Experiments in oocytes under non-voltage-clamped conditions revealed furthermore that Zn(2+) could enhance the depolarizing effect of substrates in oocytes expressing WT. The data suggest that by potentiating an uncoupled Cl(-) conductance, Zn(2+) is capable of modulating the membrane potential of cells expressing DAT and as a result cause simultaneous inhibition of uptake and enhancement of efflux.
AB - Binding of Zn(2+) to an endogenous binding site in the dopamine transporter (DAT) leads to inhibition of dopamine (DA) uptake and enhancement of carrier-mediated substrate efflux. To elucidate the molecular mechanism for this dual effect, we expressed the DAT and selected mutants in Xenopus laevis oocytes and applied the two-electrode voltage clamp technique together with substrate flux studies employing radiolabeled tracers. Under voltage clamp conditions we found that Zn(2+) (10 mum) enhanced the current induced by both DA and amphetamine. This was not accompanied by a change in the uptake rate but by a marked increase in the charge/DA flux coupling ratio as assessed from concomitant measurements of [(3)H]DA uptake and currents in voltage-clamped oocytes. These data suggest that Zn(2+) facilitates an uncoupled ion conductance mediated by DAT. Whereas this required substrate in the wild type (WT), we observed that Zn(2+) by itself activated such a conductance in a previously described mutant (Y335A). This signifies that the conductance is not strictly dependent on an active transport process. Ion substitution experiments in Y335A, as well as in WT, indicated that the uncoupled conductance activated by Zn(2+) was mainly carried by Cl(-). Experiments in oocytes under non-voltage-clamped conditions revealed furthermore that Zn(2+) could enhance the depolarizing effect of substrates in oocytes expressing WT. The data suggest that by potentiating an uncoupled Cl(-) conductance, Zn(2+) is capable of modulating the membrane potential of cells expressing DAT and as a result cause simultaneous inhibition of uptake and enhancement of efflux.
U2 - 10.1074/jbc.M407660200
DO - 10.1074/jbc.M407660200
M3 - Journal article
C2 - 15358780
VL - 279
SP - 49671
EP - 49679
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 48
ER -
ID: 3153799