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Water transport by the human Na+-coupled glutamate cotransporter expressed in Xenopus oocytes.
MacAulay N, Gether U, Klaerke DA, Zeuthen T.
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The water transport properties of the human Na+-coupled glutamate cotransporter (EAAT1) were investigated. The protein was expressed in Xenopus laevis oocytes and electrogenic glutamate transport was recorded by two-electrode voltage clamp, while the concurrent water transport was monitored as oocyte volume changes. Water transport by EAAT1 was bimodal. Water was cotransported along with glutamate and Na+ by a mechanism within the protein. The transporter also sustained passive water transport in response to osmotic challenges. The two modes could be separated and could proceed in parallel. The cotransport modality was characterized in solutions of low Cl- concentration. Addition of glutamate promptly initiated an influx of 436 +/- 55 water molecules per unit charge, irrespective of the clamp potential. The cotransport of water occurred in the presence of adverse osmotic gradients. In accordance with the Gibbs equation, energy was transferred within the protein primarily from the downhill fluxes of Na+ to the uphill fluxes of water. Experiments using the cation-selective ionophore gramicidin showed no unstirred layer effects. Na+ currents in the ionophore did not lead to any significant initial water movements. In the absence of glutamate, EAAT1 contributed a passive water permeability (Lp) of (11.3 +/- 2.0) x 10(-6) cm s(-1) (osmol l(-1))(-1). In the presence of glutamate, Lp was about 50 % higher for both high and low Cl- concentrations. The physiological role of EAAT1 as a molecular water pump is discussed in relation to cellular volume homeostasis in the nervous system.
Arriza,
Functional comparisons of three glutamate transporter subtypes cloned from human motor cortex.
1994, Pubmed,
Xenbase
Arriza,
Functional comparisons of three glutamate transporter subtypes cloned from human motor cortex.
1994,
Pubmed
,
Xenbase Arriza,
Excitatory amino acid transporter 5, a retinal glutamate transporter coupled to a chloride conductance.
1997,
Pubmed
,
Xenbase Barbour,
Electrogenic glutamate uptake in glial cells is activated by intracellular potassium.
1988,
Pubmed Brew,
Electrogenic glutamate uptake is a major current carrier in the membrane of axolotl retinal glial cells.
,
Pubmed Colombo,
Protein solvation in allosteric regulation: a water effect on hemoglobin.
1992,
Pubmed Diamond,
Wet transport proteins.
,
Pubmed
,
Xenbase Erecińska,
The role of glial cells in regulation of neurotransmitter amino acids in the external environment. II. Mechanism of aspartate transport.
1986,
Pubmed Fairman,
An excitatory amino-acid transporter with properties of a ligand-gated chloride channel.
1995,
Pubmed
,
Xenbase Finkelstein,
The gramicidin A channel: a review of its permeability characteristics with special reference to the single-file aspect of transport.
1981,
Pubmed Frigeri,
Immunolocalization of the mercurial-insensitive water channel and glycerol intrinsic protein in epithelial cell plasma membranes.
1995,
Pubmed Golovanevsky,
The reactivity of the gamma-aminobutyric acid transporter GAT-1 toward sulfhydryl reagents is conformationally sensitive. Identification of a major target residue.
1999,
Pubmed Hediger,
Homology of the human intestinal Na+/glucose and Escherichia coli Na+/proline cotransporters.
1989,
Pubmed Jung,
Molecular characterization of an aquaporin cDNA from brain: candidate osmoreceptor and regulator of water balance.
1994,
Pubmed
,
Xenbase Kanner,
Binding order of substrates to the sodium and potassium ion coupled L-glutamic acid transporter from rat brain.
1982,
Pubmed King,
Pathophysiology of the aquaporin water channels.
1996,
Pubmed Kornblatt,
A nontraditional role for water in the cytochrome c oxidase reaction.
1990,
Pubmed Lehre,
Differential expression of two glial glutamate transporters in the rat brain: quantitative and immunocytochemical observations.
1995,
Pubmed Loike,
Sodium-glucose cotransporters display sodium- and phlorizin-dependent water permeability.
1996,
Pubmed
,
Xenbase Loo,
Cotransport of water by the Na+/glucose cotransporter.
1996,
Pubmed
,
Xenbase Loo,
Commentary on "Epithelial Fluid Transport--A Century of Investigation".
1999,
Pubmed Loo,
Passive water and ion transport by cotransporters.
1999,
Pubmed
,
Xenbase Mackenzie,
Relationships between Na+/glucose cotransporter (SGLT1) currents and fluxes.
1998,
Pubmed
,
Xenbase Meinild,
The human Na+-glucose cotransporter is a molecular water pump.
1998,
Pubmed
,
Xenbase Meinild,
Water transport by the renal Na(+)-dicarboxylate cotransporter.
2000,
Pubmed
,
Xenbase Mitrovic,
Identification of functional domains of the human glutamate transporters EAAT1 and EAAT2.
1998,
Pubmed
,
Xenbase Nelson,
Hydrogen ion cotransport by the renal brush border glutamate transporter.
1983,
Pubmed Nielsen,
Specialized membrane domains for water transport in glial cells: high-resolution immunogold cytochemistry of aquaporin-4 in rat brain.
1997,
Pubmed Parent,
Electrogenic properties of the cloned Na+/glucose cotransporter: I. Voltage-clamp studies.
1992,
Pubmed
,
Xenbase Qian,
Carbohydrate binding sites in a pancreatic alpha-amylase-substrate complex, derived from X-ray structure analysis at 2.1 A resolution.
1995,
Pubmed Rand,
Measured change in protein solvation with substrate binding and turnover.
1993,
Pubmed Rothstein,
Localization of neuronal and glial glutamate transporters.
1994,
Pubmed Rudnick,
Ion-coupled neurotransmitter transport: thermodynamic vs. kinetic determinations of stoichiometry.
1998,
Pubmed Slotboom,
A conserved serine-rich stretch in the glutamate transporter family forms a substrate-sensitive reentrant loop.
1999,
Pubmed Soreq,
Xenopus oocyte microinjection: from gene to protein.
1992,
Pubmed
,
Xenbase Stallcup,
Coupled transport of glutamate and sodium in a cerebellar nerve cell line.
1979,
Pubmed Wadiche,
Macroscopic and microscopic properties of a cloned glutamate transporter/chloride channel.
1998,
Pubmed
,
Xenbase Wadiche,
Ion fluxes associated with excitatory amino acid transport.
1995,
Pubmed
,
Xenbase Wadiche,
Kinetics of a human glutamate transporter.
1995,
Pubmed
,
Xenbase Zampighi,
A method for determining the unitary functional capacity of cloned channels and transporters expressed in Xenopus laevis oocytes.
1995,
Pubmed
,
Xenbase Zerangue,
Flux coupling in a neuronal glutamate transporter.
1996,
Pubmed
,
Xenbase Zeuthen,
Cotransport of K+, Cl- and H2O by membrane proteins from choroid plexus epithelium of Necturus maculosus.
1994,
Pubmed Zeuthen,
Isotonic transport by the Na+-glucose cotransporter SGLT1 from humans and rabbit.
2001,
Pubmed
,
Xenbase Zeuthen,
Cotransport of H+, lactate and H2O by membrane proteins in retinal pigment epithelium of bullfrog.
1996,
Pubmed Zeuthen,
Water transport by the Na+/glucose cotransporter under isotonic conditions.
1997,
Pubmed
,
Xenbase Zeuthen,
Secondary active transport of water across ventricular cell membrane of choroid plexus epithelium of Necturus maculosus.
1991,
Pubmed Zhang,
Water and urea permeability properties of Xenopus oocytes: expression of mRNA from toad urinary bladder.
1991,
Pubmed
,
Xenbase Zimmerberg,
Polymer inaccessible volume changes during opening and closing of a voltage-dependent ionic channel.
,
Pubmed
