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.
J Membr Biol
2005 Jan 01;2032:65-82. doi: 10.1007/s00232-004-0732-5.
Show Gene links
Show Anatomy links
Novel properties of a mouse gamma-aminobutyric acid transporter (GAT4).
Karakossian MH, Spencer SR, Gomez AQ, Padilla OR, Sacher A, Loo DD, Nelson N, Eskandari S.
???displayArticle.abstract???
We expressed the mouse gamma-aminobutyric acid (GABA) transporter GAT4 (homologous to rat/ human GAT-3) in Xenopus laevis oocytes and examined its functional and pharmacological properties by using electrophysiological and tracer uptake methods. In the coupled mode of transport (Na+/ Cl-/GABA cotransport), there was tight coupling between charge flux and GABA flux across the plasma membrane (2 charges/GABA). Transport was highly temperature-dependent with a temperature coefficient (Q10) of 4.3. The GAT4 turnover rate (1.5 s(-l); -50 mV, 21 degrees C) and temperature dependence suggest physiological turnover rates of 15-20 s(-1). No uncoupled current was observed in the presence of Na+. In the absence of external Na+, GAT4 exhibited two distinct uncoupled currents. (i) A Cl- leak current (ICl(leak)) was observed when Na+ was replaced with choline or tetraethylammonium. The reversal potential of (ICl(leak)) followed the Cl- Nernst potential. (ii) A Li+ leak current (ILi(leak)) was observed when Na+ was replaced with Li+. Both leak currents were inhibited by Na+, and both were temperature-independent (Q10 approximately 1). The two leak modes appeared not to coexist, as Li+ inhibited (ICl(leak)). The results suggest the existence of cation- and anion-selective channel-like pathways in GAT4. Flufenamic acid inhibited GAT4 Na+/Cl-/GABA cotransport, ILi(leak), and ICl(leak), (Ki approximately 30 microM), and the voltage-induced presteady-state charge movements (Ki approximately 440 microM). Flufenamic acid exhibited little or no selectivity for GAT1, GAT2, or GAT3. Sodium and GABA concentration jicroumps revealed that slow Na+ binding to the transporter is followed by rapid GABA-induced translocation of the ligands across the plasma membrane. Thus, Na+ binding and associated conformational changes constitute the rate-limiting steps in the transport cycle.
Binda,
Temperature effects on the presteady-state and transport-associated currents of GABA cotransporter rGAT1.
2002, Pubmed
Binda,
Temperature effects on the presteady-state and transport-associated currents of GABA cotransporter rGAT1.
2002,
Pubmed Bismuth,
Tyrosine 140 of the gamma-aminobutyric acid transporter GAT-1 plays a critical role in neurotransmitter recognition.
1997,
Pubmed Borden,
Cloning of the human homologue of the GABA transporter GAT-3 and identification of a novel inhibitor with selectivity for this site.
1994,
Pubmed Borden,
GABA transporter heterogeneity: pharmacology and cellular localization.
1996,
Pubmed Cammack,
A GABA transporter operates asymmetrically and with variable stoichiometry.
1994,
Pubmed Chen,
Synaptic uptake and beyond: the sodium- and chloride-dependent neurotransmitter transporter family SLC6.
2004,
Pubmed Chiu,
Number, density, and surface/cytoplasmic distribution of GABA transporters at presynaptic structures of knock-in mice carrying GABA transporter subtype 1-green fluorescent protein fusions.
2002,
Pubmed Clark,
Stable expression of a neuronal gamma-aminobutyric acid transporter, GAT-3, in mammalian cells demonstrates unique pharmacological properties and ion dependence.
1994,
Pubmed Clark,
Functional expression and CNS distribution of a beta-alanine-sensitive neuronal GABA transporter.
1992,
Pubmed Conti,
GABA transporters in the mammalian cerebral cortex: localization, development and pathological implications.
2004,
Pubmed Cooper,
Relationship between intracellular pH and chloride in Xenopus oocytes expressing the chloride channel ClC-0.
2003,
Pubmed
,
Xenbase Dalby,
Inhibition of gamma-aminobutyric acid uptake: anatomy, physiology and effects against epileptic seizures.
2003,
Pubmed DeFelice,
Transporter structure and mechanism.
2004,
Pubmed Deken,
Transport rates of GABA transporters: regulation by the N-terminal domain and syntaxin 1A.
2000,
Pubmed
,
Xenbase Eskandari,
Thyroid Na+/I- symporter. Mechanism, stoichiometry, and specificity.
1997,
Pubmed
,
Xenbase Eskandari,
Pentameric assembly of a neuronal glutamate transporter.
2000,
Pubmed
,
Xenbase Fairman,
An excitatory amino-acid transporter with properties of a ligand-gated chloride channel.
1995,
Pubmed
,
Xenbase Fesce,
The relation between charge movement and transport-associated currents in the rat GABA cotransporter rGAT1.
2002,
Pubmed
,
Xenbase Forlani,
Three kinds of currents in the canine betaine-GABA transporter BGT-1 expressed in Xenopus laevis oocytes.
2001,
Pubmed
,
Xenbase Forster,
Forging the link between structure and function of electrogenic cotransporters: the renal type IIa Na+/Pi cotransporter as a case study.
2002,
Pubmed Gadea,
Glial transporters for glutamate, glycine, and GABA: II. GABA transporters.
2001,
Pubmed Galli,
Norepinephrine transporters have channel modes of conduction.
1996,
Pubmed Galli,
Drosophila serotonin transporters have voltage-dependent uptake coupled to a serotonin-gated ion channel.
1997,
Pubmed
,
Xenbase Grewer,
Glutamate translocation of the neuronal glutamate transporter EAAC1 occurs within milliseconds.
2000,
Pubmed Grossman,
Effect of sodium lithium and proton concentrations on the electrophysiological properties of the four mouse GABA transporters expressed in Xenopus oocytes.
2003,
Pubmed
,
Xenbase Hazama,
Presteady-state currents of the rabbit Na+/glucose cotransporter (SGLT1).
1997,
Pubmed
,
Xenbase Hilgemann,
GAT1 (GABA:Na+:Cl-) cotransport function. Database reconstruction with an alternating access model.
1999,
Pubmed
,
Xenbase Itouji,
Neuronal and glial localization of two GABA transporters (GAT1 and GAT3) in the rat cerebellum.
1996,
Pubmed Kanner,
Transmembrane domain I of the gamma-aminobutyric acid transporter GAT-1 plays a crucial role in the transition between cation leak and transport modes.
2003,
Pubmed
,
Xenbase Keynan,
Expression of a cloned gamma-aminobutyric acid transporter in mammalian cells.
1992,
Pubmed
,
Xenbase Kinney,
Synaptically evoked GABA transporter currents in neocortical glia.
2002,
Pubmed Krogsgaard-Larsen,
GABA uptake inhibitors. Design, molecular pharmacology and therapeutic aspects.
2000,
Pubmed Lester,
Listening to neurotransmitter transporters.
1996,
Pubmed Li,
An intermediate state of the gamma-aminobutyric acid transporter GAT1 revealed by simultaneous voltage clamp and fluorescence.
2000,
Pubmed
,
Xenbase Lin,
Single-channel currents produced by the serotonin transporter and analysis of a mutation affecting ion permeation.
1996,
Pubmed
,
Xenbase Liu,
Molecular characterization of four pharmacologically distinct gamma-aminobutyric acid transporters in mouse brain [corrected].
1993,
Pubmed
,
Xenbase Loo,
Role of Cl- in electrogenic Na+-coupled cotransporters GAT1 and SGLT1.
2000,
Pubmed
,
Xenbase Loo,
Relaxation kinetics of the Na+/glucose cotransporter.
1993,
Pubmed
,
Xenbase Lu,
GAT1 (GABA:Na+:Cl-) cotransport function. Steady state studies in giant Xenopus oocyte membrane patches.
1999,
Pubmed
,
Xenbase Lu,
GAT1 (GABA:Na+:Cl-) cotransport function. Kinetic studies in giant Xenopus oocyte membrane patches.
1999,
Pubmed
,
Xenbase MacAulay,
Conformational basis for the Li(+)-induced leak current in the rat gamma-aminobutyric acid (GABA) transporter-1.
2002,
Pubmed
,
Xenbase Mager,
Steady states, charge movements, and rates for a cloned GABA transporter expressed in Xenopus oocytes.
1993,
Pubmed
,
Xenbase Mager,
Conducting states of a mammalian serotonin transporter.
1994,
Pubmed
,
Xenbase Mager,
Ion binding and permeation at the GABA transporter GAT1.
1996,
Pubmed
,
Xenbase Matskevitch,
Functional characterization of the Betaine/gamma-aminobutyric acid transporter BGT-1 expressed in Xenopus oocytes.
1999,
Pubmed
,
Xenbase Melamed,
Transmembrane domains I and II of the gamma-aminobutyric acid transporter GAT-4 contain molecular determinants of substrate specificity.
2004,
Pubmed
,
Xenbase Minelli,
GAT-3, a high-affinity GABA plasma membrane transporter, is localized to astrocytic processes, and it is not confined to the vicinity of GABAergic synapses in the cerebral cortex.
1996,
Pubmed Nelson,
The family of Na+/Cl- neurotransmitter transporters.
1998,
Pubmed Nelson,
Cloning of the human brain GABA transporter.
1990,
Pubmed Otis,
Isolation of current components and partial reaction cycles in the glial glutamate transporter EAAT2.
2000,
Pubmed Panayotova-Heiermann,
Neutralization of conservative charged transmembrane residues in the Na+/glucose cotransporter SGLT1.
1998,
Pubmed Pastuszko,
Energetics of gamma-aminobutyrate transport in rat brain synaptosomes.
1982,
Pubmed Quick,
Regulating the conducting states of a mammalian serotonin transporter.
2003,
Pubmed
,
Xenbase Quick,
Regulation of a gamma-aminobutyric acid transporter by reciprocal tyrosine and serine phosphorylation.
2004,
Pubmed Radian,
Stoichiometry of sodium- and chloride-coupled gamma-aminobutyric acid transport by synaptic plasma membrane vesicles isolated from rat brain.
1983,
Pubmed Richerson,
Dynamic equilibrium of neurotransmitter transporters: not just for reuptake anymore.
2003,
Pubmed Roux,
Neuronal and glial glycine transporters have different stoichiometries.
2000,
Pubmed
,
Xenbase Ruiz-Tachiquín,
Gamma-aminobutyric acid transporter (BGT-1) expressed in human astrocytoma U373 MG cells: pharmacological and molecular characterization and phorbol ester-induced inhibition.
2002,
Pubmed Sacher,
Presteady-state and steady-state kinetics and turnover rate of the mouse gamma-aminobutyric acid transporter (mGAT3).
2002,
Pubmed
,
Xenbase Sonders,
Channels in transporters.
1996,
Pubmed Sonders,
Multiple ionic conductances of the human dopamine transporter: the actions of dopamine and psychostimulants.
1997,
Pubmed
,
Xenbase Wadiche,
Kinetics of a human glutamate transporter.
1995,
Pubmed
,
Xenbase Watzke,
Early intermediates in the transport cycle of the neuronal excitatory amino acid carrier EAAC1.
2001,
Pubmed Whitlow,
The anticonvulsant valproate increases the turnover rate of gamma-aminobutyric acid transporters.
2003,
Pubmed
,
Xenbase Wright,
Sodium cotransporters.
1996,
Pubmed
