Structural and functional dynamics of Excitatory Amino Acid Transporters (EAAT)

Thomas Rauen; Rose Tanui; Christof Grewer; Thomas Rauen; Rose Tanui; Christof Grewer

doi:10.3934/molsci.2014.3.99

AIMS Molecular Science

2014, Volume 1, Issue 3: 99-125. doi: 10.3934/molsci.2014.3.99

Previous Article Next Article

Review Special Issues

Structural and functional dynamics of Excitatory Amino Acid Transporters (EAAT)

1.
University of Osnabrueck, FB 5-Biophysics/Electrophysiology, 49076 Osnabrueck, Germany;
2.
Department of Chemistry, Binghamton University, Binghamton, NY 13902, USA

Received: 22 July 2014 Accepted: 22 September 2014 Published: 22 July 2014

Glutamate transporters control the glutamate homeostasis in the central nervous system, and, thus, are not only crucial for physiological excitatory synaptic signaling, but also for the prevention of a large number of neurodegenerative diseases that are associated with excessive and prolonged presence of the neurotransmitter glutamate in the extracellular space. Until now, five subtypes of high-affinity glutamate transporters (excitatory amino acid transporters, EAATs 1–5) have been identified. These 5 high-affinity glutamate transporter subtypes belong to the solute carrier 1 (SLC1) family of transmembrane proteins: EAAT1/GLAST (SLC1A3), EAAT2/GLT1 (SLC1A2), EAAT3/EAAC1 (SLC1A1), EAAT4 (SLC1A6) and EAAT5 (SLC1A7). EAATs are secondary-active transporters, taking up glutamate into the cell against a substantial concentration gradient. The driving force for concentrative uptake is provided by the co-transport of Na⁺ ions and the counter-transport of one K⁺ in a step independent of the glutamate translocation step. Due to the electrogenicity of transport, the transmembrane potential can also act as driving force. Glutamate transporters are also able to run in reverse, resulting in glutamate release from cells. Due to these important physiological functions, glutamate transporter expression and, therefore, the transport rate, are tightly regulated. The EAAT protein family are structurally expected to be highly similar, however, these transporters show a functional diversity that ranges from high capacity glutamate uptake systems (EAATs 1–3) to receptor-like glutamate activated anion channels (EAATs 4–5). Here, we provide an update on most recent progress made on EAAT’s molecular transport mechanism, structure-function relationships, pharmacology, and will add recent insights into mechanism of rapid membrane trafficking of glutamate transporters.
- glutamate transporter,
- excitatory amino acid transporter,
- EAAT,
- SLC1A,
- neurotransmission,
- rapid kinetics,
- molecular dynamics simulation,
- glutamate transporter regulation,
- intracellular trafficking,
- glutamate transporter pharmacology
Citation: Thomas Rauen, Rose Tanui, Christof Grewer. Structural and functional dynamics of Excitatory Amino Acid Transporters (EAAT)[J]. AIMS Molecular Science, 2014, 1(3): 99-125. doi: 10.3934/molsci.2014.3.99

Related Papers:

Abstract

Glutamate transporters control the glutamate homeostasis in the central nervous system, and, thus, are not only crucial for physiological excitatory synaptic signaling, but also for the prevention of a large number of neurodegenerative diseases that are associated with excessive and prolonged presence of the neurotransmitter glutamate in the extracellular space. Until now, five subtypes of high-affinity glutamate transporters (excitatory amino acid transporters, EAATs 1–5) have been identified. These 5 high-affinity glutamate transporter subtypes belong to the solute carrier 1 (SLC1) family of transmembrane proteins: EAAT1/GLAST (SLC1A3), EAAT2/GLT1 (SLC1A2), EAAT3/EAAC1 (SLC1A1), EAAT4 (SLC1A6) and EAAT5 (SLC1A7). EAATs are secondary-active transporters, taking up glutamate into the cell against a substantial concentration gradient. The driving force for concentrative uptake is provided by the co-transport of Na⁺ ions and the counter-transport of one K⁺ in a step independent of the glutamate translocation step. Due to the electrogenicity of transport, the transmembrane potential can also act as driving force. Glutamate transporters are also able to run in reverse, resulting in glutamate release from cells. Due to these important physiological functions, glutamate transporter expression and, therefore, the transport rate, are tightly regulated. The EAAT protein family are structurally expected to be highly similar, however, these transporters show a functional diversity that ranges from high capacity glutamate uptake systems (EAATs 1–3) to receptor-like glutamate activated anion channels (EAATs 4–5). Here, we provide an update on most recent progress made on EAAT’s molecular transport mechanism, structure-function relationships, pharmacology, and will add recent insights into mechanism of rapid membrane trafficking of glutamate transporters.

References

[1]	Zerangue N, Kavanaugh MP (1996) Flux coupling in a neuronal glutamate transporter. Nature 383: 634-637. doi: 10.1038/383634a0
[2]	Danbolt NC (2001) Glutamate uptake. Prog Neurobiol 65: 1-105. doi: 10.1016/S0301-0082(00)00067-8
[3]	Hertz L (1979) Functional interactions between neurons and astrocytes. I. Turnover and metabolism of putative amino acid transmitters. ProgNeurobiol 13: 277-323.
[4]	Broer S, Brookes N (2001) Transfer of glutamine between astrocytes and neurons. J Neurochem 77: 705-719. doi: 10.1046/j.1471-4159.2001.00322.x
[5]	Drejer J, Larsson OM, Schousboe A (1982) Characterization of L-glutamate uptake into and release from astrocytes and neurons cultured from differnt brain regions. ExpBrain Res 47: 259-269.
[6]	Schousboe A, Hertz L (1981) Role of astroglial cells in glutamate homeostasis. Adv Biochem Psychopharmacol 27: 103-113.
[7]	Rauen T, Taylor WR, Kuhlbrodt K, et al. (1998) High-affinity glutamate transporters in the rat retina: a major role of the glial glutamate transporter GLAST-1 in transmitter clearance. Cell Tissue Res 291: 19-31.
[8]	Rauen T, Wiessner M (2000) Fine tuning of glutamate uptake and degradation in glial cells: common transcriptional regulation of GLAST1 and GS. Neurochem Int 37: 179-189. doi: 10.1016/S0197-0186(00)00021-8
[9]	Furness DN, Dehnes Y, Akhtar AQ, et al. (2008) A quantitative assessment of glutamate uptake into hippocampal synaptic terminals and astrocytes: new insights into a neuronal role for excitatory amino acid transporter 2 (EAAT2). Neuroscience 157: 80-94. doi: 10.1016/j.neuroscience.2008.08.043
[10]	Pines G, Danbolt NC, Bjoras M, et al. (1992) Cloning and expression of a rat brain L-glutamate transporter. Nature 360: 464-467. doi: 10.1038/360464a0
[11]	Storck T, Schulte S, Hofmann K, et al. (1992) Structure, expression, and functional analysis of a Na(+)-dependent glutamate/aspartate transporter from rat brain. Proc Natl Acad Sci U S A 89: 10955-10959. doi: 10.1073/pnas.89.22.10955
[12]	Arriza JL, Fairman WA, Wadiche JI, et al. (1994) Functional comparisons of three glutamate transporter subtypes cloned from human motor cortex. J Neurosci 14: 5559-5569.
[13]	Tanaka K, Watase K, Manabe T, et al. (1997) Epilepsy and exacerbation of brain injury in mice lacking the glutamate transporter GLT-1. Science 276: 1699-1702. doi: 10.1126/science.276.5319.1699
[14]	Bjornsen LP, Hadera MG, Zhou Y, et al. (2014) The GLT-1 (EAAT2; slc1a2) glutamate transporter is essential for glutamate homeostasis in the neocortex of the mouse. J Neurochem 128: 641-649. doi: 10.1111/jnc.12509
[15]	Rauen T, Wiessner M, Sullivan R, et al. (2004) A new GLT1 splice variant: cloning and immunolocalization of GLT1c in the mammalian retina and brain. Neurochem Int 45: 1095-1106. doi: 10.1016/j.neuint.2004.04.006
[16]	Sullivan R, Rauen T, Fischer F, et al. (2004) Cloning, transport properties, and differential localization of two splice variants of GLT-1 in the rat CNS: Implications for CNS glutamate homeostasis. Glia 45: 155-169. doi: 10.1002/glia.10317
[17]	Lee A, Anderson AR, Beasley SJ, et al. (2012) A new splice variant of the glutamate-aspartate transporter: cloning and immunolocalization of GLAST1c in rat, pig and human brains. J Chem Neuroanat 43: 52-63. doi: 10.1016/j.jchemneu.2011.10.005
[18]	Grewer C, Gameiro A, Rauen T (2014) SLC1 glutamate transporters. Pflugers Arch 466: 3-24. doi: 10.1007/s00424-013-1397-7
[19]	Rauen T (2000) Diversity of glutamate transporter expression and function in the mammalian retina. Amino Acids 19: 53-62. doi: 10.1007/s007260070033
[20]	Rauen T, Kanner BI (1994) Localization of the glutamate transporter GLT-1 in rat and macaque monkey retinae. Neurosci Lett 169: 137-140. doi: 10.1016/0304-3940(94)90375-1
[21]	Wiessner M, Fletcher EL, Fischer F, et al. (2002) Localization and possible function of the glutamate transporter, EAAC1, in the rat retina. Cell Tissue Res 310: 31-40. doi: 10.1007/s00441-002-0612-1
[22]	Holmseth S, Dehnes Y, Huang YH, et al. (2012) The density of EAAC1 (EAAT3) glutamate transporters expressed by neurons in the mammalian CNS. J Neurosci 32: 6000-6013. doi: 10.1523/JNEUROSCI.5347-11.2012
[23]	Dehnes Y, Chaudhry FA, Ullensvang K, et al. (1998) The glutamate transporter EAAT4 in rat cerebellar Purkinje cells: a glutamate-gated chloride channel concentrated near the synapse in parts of the dendritic membrane facing astroglia. J Neurosci 18: 3606-3619.
[24]	Mim C, Balani P, Rauen T, et al. (2005) The Glutamate Transporter Subtypes EAAT4 and EAATs 1-3 Transport Glutamate with Dramatically Different Kinetics and Voltage Dependence but Share a Common Uptake Mechanism. J Gen Physiol 126: 571-589. doi: 10.1085/jgp.200509365
[25]	Gincel D, Regan MR, Jin L, et al. (2007) Analysis of cerebellar Purkinje cells using EAAT4 glutamate transporter promoter reporter in mice generated via bacterial artificial chromosome-mediated transgenesis. Exp Neurol 203: 205-212. doi: 10.1016/j.expneurol.2006.08.016
[26]	Kovermann P, Machtens JP, Ewers D, et al. (2010) A conserved aspartate determines pore properties of anion channels associated with excitatory amino acid transporter 4 (EAAT4). J Biol Chem 285: 23676-23686. doi: 10.1074/jbc.M110.126557
[27]	Arriza JL, Eliasof S, Kavanaugh MP, et al. (1997) Excitatory amino acid transporter 5, a retinal glutamate transporter coupled to a chloride conductance. Proc Natl Acad Sci U S A 94: 4155-4160. doi: 10.1073/pnas.94.8.4155
[28]	Wersinger E, Schwab Y, Sahel JA, et al. (2006) The glutamate transporter EAAT5 works as a presynaptic receptor in mouse rod bipolar cells. J Physiol 577: 221-234. doi: 10.1113/jphysiol.2006.118281
[29]	Gameiro A, Braams S, Rauen T, et al. (2011) The Discovery of Slowness: Low-Capacity Transport and Slow Anion Channel Gating by the Glutamate Transporter EAAT5. Biophysical journal 100: 2623-2632. doi: 10.1016/j.bpj.2011.04.034
[30]	Hediger MA, Kanai Y, You G, et al. (1995) Mammalian ion-coupled solute transporters. JPhysiolLond 482: 7S-17S.
[31]	Bailey CG, Ryan RM, Thoeng AD, et al. (2011) Loss-of-function mutations in the glutamate transporter SLC1A1 cause human dicarboxylic aminoaciduria. J Clin Invest 121: 446-453. doi: 10.1172/JCI44474
[32]	Duerson K, Woltjer RL, Mookherjee P, et al. (2009) Detergent-insoluble EAAC1/EAAT3 aberrantly accumulates in hippocampal neurons of Alzheimer's disease patients. Brain Pathol 19: 267-278. doi: 10.1111/j.1750-3639.2008.00186.x
[33]	Revett TJ, Baker GB, Jhamandas J, et al. (2013) Glutamate system, amyloid ss peptides and tau protein: functional interrelationships and relevance to Alzheimer disease pathology. J Psychiatry Neurosci 38: 6-23. doi: 10.1503/jpn.110190
[34]	Rothstein JD (2009) Current hypotheses for the underlying biology of amyotrophic lateral sclerosis. Ann Neurol 65 Suppl 1: S3-9.
[35]	Lang UE, Borgwardt S (2013) Molecular Mechanisms of Depression: Perspectives on New Treatment Strategies. Cell Physiol Biochem 31: 761-777. doi: 10.1159/000350094
[36]	Crino PB, Jin H, Shumate MD, et al. (2002) Increased expression of the neuronal glutamate transporter (EAAT3/EAAC1) in hippocampal and neocortical epilepsy. Epilepsia 43: 211-218. doi: 10.1046/j.1528-1157.2002.35001.x
[37]	Estrada-Sanchez AM, Rebec GV (2012) Corticostriatal dysfunction and glutamate transporter 1 (GLT1) in Huntington's disease: interactions between neurons and astrocytes. Basal Ganglia 2: 57-66. doi: 10.1016/j.baga.2012.04.029
[38]	Rao VL, Dogan A, Todd KG, et al. (2001) Antisense knockdown of the glial glutamate transporter GLT-1, but not the neuronal glutamate transporter EAAC1, exacerbates transient focal cerebral ischemia-induced neuronal damage in rat brain. J Neurosci 21: 1876-1883.
[39]	Grewer C, Gameiro A, Zhang Z, et al. (2008) Glutamate forward and reverse transport: from molecular mechanism to transporter-mediated release after ischemia. IUBMB Life 60: 609-619. doi: 10.1002/iub.98
[40]	Ketheeswaranathan P, Turner NA, Spary EJ, et al. (2011) Changes in glutamate transporter expression in mouse forebrain areas following focal ischemia. Brain Res 1418: 93-103. doi: 10.1016/j.brainres.2011.08.029
[41]	Seki Y, Feustel PJ, Keller RW, et al. (1999) Inhibition of ischemia-induced glutamate release in rat striatum by dihydrokinate and an anion channel blocker. Stroke 30: 433-440. doi: 10.1161/01.STR.30.2.433
[42]	Azami Tameh A, Clarner T, Beyer C, et al. (2013) Regional regulation of glutamate signaling during cuprizone-induced demyelination in the brain. Ann Anat.
[43]	Karlsson RM, Tanaka K, Heilig M, et al. (2008) Loss of glial glutamate and aspartate transporter (excitatory amino acid transporter 1) causes locomotor hyperactivity and exaggerated responses to psychotomimetics: rescue by haloperidol and metabotropic glutamate 2/3 agonist. Biol Psychiatry 64: 810-814. doi: 10.1016/j.biopsych.2008.05.001
[44]	Karlsson RM, Tanaka K, Saksida LM, et al. (2009) Assessment of glutamate transporter GLAST (EAAT1)-deficient mice for phenotypes relevant to the negative and executive/cognitive symptoms of schizophrenia. Neuropsychopharmacology 34: 1578-1589. doi: 10.1038/npp.2008.215
[45]	Adamczyk A, Gause CD, Sattler R, et al. (2011) Genetic and functional studies of a missense variant in a glutamate transporter, SLC1A3, in Tourette syndrome. Psychiatr Genet 21: 90-97. doi: 10.1097/YPG.0b013e328341a307
[46]	Reyes N, Ginter C, Boudker O (2009) Transport mechanism of a bacterial homologue of glutamate transporters. Nature 462: 880-885. doi: 10.1038/nature08616
[47]	Verdon G, Boudker O (2012) Crystal structure of an asymmetric trimer of a bacterial glutamate transporter homolog. Nat Struct Mol Biol 19: 355-357. doi: 10.1038/nsmb.2233
[48]	Yernool D, Boudker O, Jin Y, et al. (2004) Structure of a glutamate transporter homologue from Pyrococcus horikoshii. Nature 431: 811-818. doi: 10.1038/nature03018
[49]	Jardetzky O (1966) Simple allosteric model for membrane pumps. Nature 211: 969-970. doi: 10.1038/211969a0
[50]	Owe SG, Marcaggi P, Attwell D (2006) The ionic stoichiometry of the GLAST glutamate transporter in salamander retinal glia. J Physiol 577: 591-599. doi: 10.1113/jphysiol.2006.116830
[51]	Kanai Y, Nussberger S, Romero MF, et al. (1995) Electrogenic properties of the epithelial and neuronal high affinity glutamate transporter. J Biol Chem 270: 16561-16568. doi: 10.1074/jbc.270.28.16561
[52]	Wadiche JI, Kavanaugh MP (1998) Macroscopic and microscopic properties of a cloned glutamate transporter/chloride channel. J Neurosci 18: 7650-7661.
[53]	Otis TS, Kavanaugh MP (2000) Isolation of current components and partial reaction cycles in the glial glutamate transporter EAAT2. J Neurosci 20: 2749-2757.
[54]	Otis TS, Jahr CE (1998) Anion currents and predicted glutamate flux through a neuronal glutamate transporter. J Neurosci 18: 7099-7110.
[55]	Bergles DE, Tzingounis AV, Jahr CE (2002) Comparison of coupled and uncoupled currents during glutamate uptake by GLT-1 transporters. J Neurosci 22: 10153-10162.
[56]	Grewer C, Watzke N, Wiessner M, et al. (2000) Glutamate translocation of the neuronal glutamate transporter EAAC1 occurs within milliseconds. Proc Natl Acad Sci U S A 97: 9706-9711. doi: 10.1073/pnas.160170397
[57]	Watzke N, Bamberg E, Grewer C (2001) Early intermediates in the transport cycle of the neuronal excitatory amino acid carrier EAAC1. J Gen Physiol 117: 547-562. doi: 10.1085/jgp.117.6.547
[58]	Mwaura J, Tao Z, James H, et al. (2012) Protonation state of a conserved acidic amino acid involved in Na(+) binding to the glutamate transporter EAAC1. ACS Chem Neurosci 12: 1073-1083.
[59]	Diamond JS, Jahr CE (1997) Transporters buffer synaptically released glutamate on a submillisecond time scale. J Neurosci 17: 4672-4687.
[60]	Mim C, Tao Z, Grewer C (2007) Two conformational changes are associated with glutamate translocation by the glutamate transporter EAAC1. Biochemistry 46: 9007-9018. doi: 10.1021/bi7005465
[61]	Wadiche JI, Arriza JL, Amara SG, et al. (1995) Kinetics of a human glutamate transporter. Neuron 14: 1019-1027. doi: 10.1016/0896-6273(95)90340-2
[62]	Loo DD, Hazama A, Supplisson S, et al. (1993) Relaxation kinetics of the Na+/glucose cotransporter. Proc Natl Acad Sci U S A 90: 5767-5771. doi: 10.1073/pnas.90.12.5767
[63]	Lu CC, Hilgemann DW (1999) GAT1 (GABA:Na+:Cl-) cotransport function. Kinetic studies in giant Xenopus oocyte membrane patches. J Gen Physiol 114: 445-457.
[64]	Grewer C, Zhang Z, Mwaura J, et al. (2012) Charge compensation mechanism of a Na+-coupled, secondary active glutamate transporter. J Biol Chem 287: 26921-26931. doi: 10.1074/jbc.M112.364059
[65]	Zhang Z, Tao Z, Gameiro A, et al. (2007) Transport direction determines the kinetics of substrate transport by the glutamate transporter EAAC1. Proc Natl Acad Sci U S A 104: 18025-18030. doi: 10.1073/pnas.0704570104
[66]	Wadiche JI, Amara SG, Kavanaugh MP (1995) Ion fluxes associated with excitatory amino acid transport. Neuron 15: 721-728. doi: 10.1016/0896-6273(95)90159-0
[67]	Eliasof S, Jahr CE (1996) Retinal glial cell glutamate transporter is coupled to an anionic conductance. Proc Natl Acad Sci U S A 93: 4153-4158. doi: 10.1073/pnas.93.9.4153
[68]	Billups B, Rossi D, Attwell D (1996) Anion conductance behavior of the glutamate uptake carrier in salamander retinal glial cells. J Neurosci 16: 6722-6731.
[69]	Fairman WA, Vandenberg RJ, Arriza JL, et al. (1995) An excitatory amino-acid transporter with properties of a ligand-gated chloride channel. Nature 375: 599-603. doi: 10.1038/375599a0
[70]	Larsson HP, Picaud SA, Werblin FS, et al. (1996) Noise analysis of the glutamate-activated current in photoreceptors. Biophysl J 70: 733-742. doi: 10.1016/S0006-3495(96)79613-3
[71]	Melzer N, Biela A, Fahlke C (2003) Glutamate modifies ion conduction and voltage-dependent gating of excitatory amino acid transporter-associated anion channels. J Biol Chem 278: 50112-50119. doi: 10.1074/jbc.M307990200
[72]	Picaud SA, Larsson HP, Grant GB, et al. (1995) Glutamate-gated chloride channel with glutamate-transporter-like properties in cone photoreceptors of the tiger salamander. J Neurophys 74: 1760-1771.
[73]	Watzke N, Grewer C (2001) The anion conductance of the glutamate transporter EAAC1 depends on the direction of glutamate transport. FEBS Lett 503: 121-125. doi: 10.1016/S0014-5793(01)02715-6
[74]	Tao Z, Grewer C (2007) Cooperation of the conserved aspartate 439 and bound amino acid substrate is important for high-affinity Na+ binding to the glutamate transporter EAAC1. J Gen Physiol 129: 331-344. doi: 10.1085/jgp.200609678
[75]	Boudker O, Ryan RM, Yernool D, et al. (2007) Coupling substrate and ion binding to extracellular gate of a sodium-dependent aspartate transporter. Nature 445: 387-393. doi: 10.1038/nature05455
[76]	Cater RJ, Vandenberg RJ, Ryan RM (2014) The domain interface of the human glutamate transporter EAAT1 mediates chloride permeation. Biophys J 107: 621-629. doi: 10.1016/j.bpj.2014.05.046
[77]	Huang Z, Tajkhorshid E (2008) Dynamics of the extracellular gate and ion-substrate coupling in the glutamate transporter. Biophys J 95: 2292-2300. doi: 10.1529/biophysj.108.133421
[78]	Shrivastava IH, Jiang J, Amara SG, et al. (2008) Time-resolved mechanism of extracellular gate opening and substrate binding in a glutamate transporter. J Biol Chem 283: 28680-28690. doi: 10.1074/jbc.M800889200
[79]	Huang Z, Tajkhorshid E (2010) Identification of the third Na+ site and the sequence of extracellular binding events in the glutamate transporter. Biophys J 99: 1416-1425. doi: 10.1016/j.bpj.2010.06.052
[80]	Bastug T, Heinzelmann G, Kuyucak S, et al. (2012) Position of the third Na+ site in the aspartate transporter GltPh and the human glutamate transporter, EAAT1. PLoS One 7: e33058. doi: 10.1371/journal.pone.0033058
[81]	Groeneveld M, Slotboom DJ (2010) Na(+):aspartate coupling stoichiometry in the glutamate transporter homologue Glt(Ph). Biochemistry 49: 3511-3513. doi: 10.1021/bi100430s
[82]	Larsson HP, Wang X, Lev B, et al. (2010) Evidence for a third sodium-binding site in glutamate transporters suggests an ion/substrate coupling model. Proc Natl Acad Sci U S A 107: 13912-13917. doi: 10.1073/pnas.1006289107
[83]	DeChancie J, Shrivastava IH, Bahar I (2011) The mechanism of substrate release by the aspartate transporter GltPh: insights from simulations. Mol Biosyst 7: 832-842. doi: 10.1039/C0MB00175A
[84]	Zomot E, Bahar I (2013) Intracellular gating in an inward-facing state of aspartate transporter Glt(Ph) is regulated by the movements of the helical hairpin HP2. J Biol Chem 288: 8231-8237. doi: 10.1074/jbc.M112.438432
[85]	Heinzelmann G, Kuyucak S (2014) Molecular dynamics simulations of the mammalian glutamate transporter EAAT3. PLoS One 9: e92089. doi: 10.1371/journal.pone.0092089
[86]	Jiang J, Shrivastava IH, Watts SD, et al. (2011) Large collective motions regulate the functional properties of glutamate transporter trimers. Proc Natl Acad Sci U S A 108: 15141-15146. doi: 10.1073/pnas.1112216108
[87]	Lezon TR, Bahar I (2012) Constraints imposed by the membrane selectively guide the alternating access dynamics of the glutamate transporter GltPh. Biophys J 102: 1331-1340. doi: 10.1016/j.bpj.2012.02.028
[88]	Das A, Gur M, Cheng MH, et al. (2014) Exploring the conformational transitions of biomolecular systems using a simple two-state anisotropic network model. PLoS Comput Biol 10: e1003521. doi: 10.1371/journal.pcbi.1003521
[89]	Stolzenberg S, Khelashvili G, Weinstein H (2012) Structural intermediates in a model of the substrate translocation path of the bacterial glutamate transporter homologue GltPh. J Phys Chem B 116: 5372-5383. doi: 10.1021/jp301726s
[90]	Grewer C, Watzke N, Rauen T, et al. (2003) Is the glutamate residue Glu-373 the proton acceptor of the excitatory amino acid carrier 1? J Biol Chem 278: 2585-2592. doi: 10.1074/jbc.M207956200
[91]	Heinzelmann G, Kuyucak S (2014) Molecular Dynamics Simulations Elucidate the Mechanism of Proton Transport in the Glutamate Transporter EAAT3. Biophys J 106: 2675-2683. doi: 10.1016/j.bpj.2014.05.010
[92]	Grewer C, Jager J, Carpenter BK, et al. (2000) A new photolabile precursor of glycine with improved properties: A tool for chemical kinetic investigations of the glycine receptor. Biochemistry 39: 2063-2070. doi: 10.1021/bi9919652
[93]	Grewer C, Rauen T (2005) Electrogenic glutamate transporters in the CNS: molecular mechanism, pre-steady-state kinetics, and their impact on synaptic signaling. J Membr Biol 203: 1-20. doi: 10.1007/s00232-004-0731-6
[94]	Gegelashvili G, Robinson MB, Trotti D, et al. (2001) Regulation of glutamate transporters in health and disease. Prog Brain Res 132: 267-286. doi: 10.1016/S0079-6123(01)32082-4
[95]	Santos SD, Carvalho AL, Caldeira MV, et al. (2009) Regulation of AMPA receptors and synaptic plasticity. Neuroscience 158: 105-125. doi: 10.1016/j.neuroscience.2008.02.037
[96]	Stephenson FA, Cousins SL, Kenny AV (2008) Assembly and forward trafficking of NMDA receptors (Review). Mol Membr Biol 25: 311-320. doi: 10.1080/09687680801971367
[97]	Robinson MB (2002) Regulated trafficking of neurotransmitter transporters: common notes but different melodies. J Neurochem 80: 1-11.
[98]	Gonzalez MI, Robinson MB (2004) Protein KINASE C-Dependent Remodeling of Glutamate Transporter Function. Mol Intervent 4: 48-58. doi: 10.1124/mi.4.1.48
[99]	Sheldon AL, Robinson MB (2007) The role of glutamate transporters in neurodegenerative diseases and potential opportunities for intervention. Neurochem Int 51: 333-355. doi: 10.1016/j.neuint.2007.03.012
[100]	Beart PM, O'Shea RD (2007) Transporters for L-glutamate: an update on their molecular pharmacology and pathological involvement. Br J Pharmacol 150: 5-17.
[101]	Poitry-Yamate CL, Vutskits L, Rauen T (2002) Neuronal-induced and glutamate-dependent activation of glial glutamate transporter function. J Neurochem 82: 987-997. doi: 10.1046/j.1471-4159.2002.01075.x
[102]	Benediktsson AM, Marrs GS, Tu JC, et al. (2012) Neuronal activity regulates glutamate transporter dynamics in developing astrocytes. Glia 60: 175-188. doi: 10.1002/glia.21249
[103]	Gonzalez-Gonzalez IM, Garcia-Tardon N, Gimenez C, et al. (2008) PKC-dependent endocytosis of the GLT1 glutamate transporter depends on ubiquitylation of lysines located in a C-terminal cluster. Glia 56: 963-974. doi: 10.1002/glia.20670
[104]	Sheldon AL, Gonzalez MI, Krizman-Genda EN, et al. (2008) Ubiquitination-mediated internalization and degradation of the astroglial glutamate transporter, GLT-1. Neurochem Int 53: 296-308. doi: 10.1016/j.neuint.2008.07.010
[105]	Martinez-Villarreal J, Garcia Tardon N, Ibanez I, et al. (2012) Cell surface turnover of the glutamate transporter GLT-1 is mediated by ubiquitination/deubiquitination. Glia 60: 1356-1365. doi: 10.1002/glia.22354
[106]	Sheldon AL, Gonzalez MI, Robinson MB (2006) A carboxyl-terminal determinant of the neuronal glutamate transporter, EAAC1, is required for platelet-derived growth factor-dependent trafficking. J Biol Chem 281: 4876-4886. doi: 10.1074/jbc.M504983200
[107]	Garcia-Tardon N, Gonzalez-Gonzalez IM, Martinez-Villarreal J, et al. (2012) Protein kinase C (PKC)-promoted endocytosis of glutamate transporter GLT-1 requires ubiquitin ligase Nedd4-2-dependent ubiquitination but not phosphorylation. J Biol Chem 287: 19177-19187. doi: 10.1074/jbc.M112.355909
[108]	A DA, Soragna A, Di Cairano E, et al. (2010) The Surface Density of the Glutamate Transporter EAAC1 is Controlled by Interactions with PDZK1 and AP2 Adaptor Complexes. Traffic 11: 1455-1470. doi: 10.1111/j.1600-0854.2010.01110.x
[109]	Traub LM (2009) Tickets to ride: selecting cargo for clathrin-regulated internalization. Nat Rev Mol Cell Biol 10: 583-596. doi: 10.1038/nrm2751
[110]	Sato K, Otsu W, Otsuka Y, et al. (2013) Modulatory roles of NHERF1 and NHERF2 in cell surface expression of the glutamate transporter GLAST. Biochem Biophys Res Commun 430: 839-845. doi: 10.1016/j.bbrc.2012.11.059
[111]	Shouffani A, Kanner BI (1990) Cholesterol is required for the reconstruction of the sodium- and chloride-coupled, gamma-aminobutyric acid transporter from rat brain. J Biol Chem 265: 6002-6008.
[112]	Butchbach ME, Guo H, Lin CL (2003) Methyl-beta-cyclodextrin but not retinoic acid reduces EAAT3-mediated glutamate uptake and increases GTRAP3-18 expression. J Neurochem 84: 891-894. doi: 10.1046/j.1471-4159.2003.01588.x
[113]	Simons K, Gerl MJ (2010) Revitalizing membrane rafts: new tools and insights. Nat Rev Mol Cell Biol 11: 688-699. doi: 10.1038/nrm2977
[114]	Butchbach ME, Tian G, Guo H, et al. (2004) Association of excitatory amino acid transporters, especially EAAT2, with cholesterol-rich lipid raft microdomains: importance for excitatory amino acid transporter localization and function. J Biol Chem 279: 34388-34396. doi: 10.1074/jbc.M403938200
[115]	Zschocke J, Bayatti N, Behl C (2005) Caveolin and GLT-1 gene expression is reciprocally regulated in primary astrocytes: association of GLT-1 with non-caveolar lipid rafts. Glia 49: 275-287. doi: 10.1002/glia.20116
[116]	Gonzalez MI, Krizman-Genda E, Robinson MB (2007) Caveolin-1 regulates the delivery and endocytosis of the glutamate transporter, excitatory amino acid carrier 1. J Biol Chem 282: 29855-29865. doi: 10.1074/jbc.M704738200
[117]	Ledesma MD, Dotti CG (2005) The conflicting role of brain cholesterol in Alzheimer's disease: lessons from the brain plasminogen system. Biochem Soc Symp: 129-138.
[118]	Tian G, Kong Q, Lai L, et al. (2010) Increased expression of cholesterol 24S-hydroxylase results in disruption of glial glutamate transporter EAAT2 association with lipid rafts: a potential role in Alzheimer's disease. J Neurochem 113: 978-989. doi: 10.1111/j.1471-4159.2010.06661.x
[119]	Arriza JL, Eliasof S, Kavanaugh MP, et al. (1997) Excitatory amino acid transporter 5, a retinal glutamate transporter coupled to a chloride conductance. Proc Natl Acad Sci U S A 94: 4155-4160. doi: 10.1073/pnas.94.8.4155
[120]	Arriza JL, Fairman WA, Wadiche JI, et al. (1994) Functional comparisons of three glutamate transporter subtypes cloned from human motor cortex. J Neurosci 14: 5559-5569.
[121]	Bridges RJ, Stanley MS, Anderson MW, et al. (1991) Conformationally defined neurotransmitter analogues. Selective inhibition of glutamate uptake by one pyrrolidine-2,4-dicarboxylate diastereomer. J Med Chem 34: 717-725.
[122]	Griffiths R, Dunlop J, Gorman A, et al. (1994) L-Trans-Pyrrolidine-2,4-Dicarboxylate and Cis-1-Aminocyclobutane-1,3-Dicarboxylate Behave as Transportable, Competitive Inhibitors of the High-Affinity Glutamate Transporters. Biochem Pharmacol 47: 267-274. doi: 10.1016/0006-2952(94)90016-7
[123]	Vandenberg RJ, Mitrovic AD, Chebib M, et al. (1997) Contrasting modes of action of methylglutamate derivatives on the excitatory amino acid transporters, EAAT1 and EAAT2. Mol Pharmacol 51: 809-815.
[124]	Huang S, Ryan RM, Vandenberg RJ (2009) The role of cation binding in determining substrate selectivity of glutamate transporters. J Biol Chem 284: 4510-4515. doi: 10.1074/jbc.M808495200
[125]	Eliasof S, McIlvain HB, Petroski RE, et al. (2001) Pharmacological characterization of threo-3-methylglutamic acid with excitatory amino acid transporters in native and recombinant systems. J Neurochem 77: 550-557. doi: 10.1046/j.1471-4159.2001.00253.x
[126]	Kanai Y, Hediger MA (1992) Primary structure and functional characterization of a high-affinity glutamate transporter. Nature 360: 467-471. doi: 10.1038/360467a0
[127]	Rauen T, Jeserich G, Danbolt NC, et al. (1992) Comparative analysis of sodium-dependent L-glutamate transport of synaptosomal and astroglial membrane vesicles from mouse cortex. FEBS Lett 312: 15-20. doi: 10.1016/0014-5793(92)81401-7
[128]	Zerangue N, Kavanaugh MP (1996) Interaction of L-cysteine with a human excitatory amino acid transporter. J Physiol 493 ( Pt 2): 419-423.
[129]	Roberts PJ, Watkins JC (1975) Structural requirements for the inhibition for L-glutamate uptake by glia and nerve endings. Brain Res 85: 120-125. doi: 10.1016/0006-8993(75)91016-1
[130]	Wilson DF, Pastuszko A (1986) Transport of Cysteate by Synaptosomes Isolated from Rat-Brain - Evidence That It Utilizes the Same Transporter as Aspartate, Glutamate, and Cysteine Sulfinate. J Neurochem 47: 1091-1097.
[131]	Vandenberg RJ, Mitrovic AD, Johnston GAR (1998) Serine-O-sulphate transport by the human glutamate transporter, EAAT2. Br J Pharmacol 123: 1593-1600. doi: 10.1038/sj.bjp.0701776
[132]	Bender AS, Woodbury DM, White HS (1989) Beta-Dl-Methylene-Aspartate, an Inhibitor of Aspartate-Aminotransferase, Potently Inhibits L-Glutamate Uptake into Astrocytes. Neurochem Res 14: 641-646. doi: 10.1007/BF00964873
[133]	Mitrovic AD, Amara SG, Johnston GA, et al. (1998) Identification of functional domains of the human glutamate transporters EAAT1 and EAAT2. J Biol Chem 273: 14698-14706. doi: 10.1074/jbc.273.24.14698
[134]	Vandenberg RJ, Mitrovic AD, Johnston GA (1998) Serine-O-sulphate transport by the human glutamate transporter, EAAT2. Br J Pharmacol 123: 1593-1600. doi: 10.1038/sj.bjp.0701776
[135]	Campiani G, De Angelis M, Armaroli S, et al. (2001) A rational approach to the design of selective substrates and potent nontransportable inhibitors of the excitatory amino acid transporter EAAC1 (EAAT3). New glutamate and aspartate analogues as potential neuroprotective agents. J Med Chem 44: 2507-2510.
[136]	Danbolt NC (2001) Glutamate uptake. Prog Neurobiol 65: 1-105. doi: 10.1016/S0301-0082(00)00067-8
[137]	Wang GJ, Chung HJ, Schnuer J, et al. (1998) Dihydrokainate-sensitive neuronal glutamate transport is required for protection of rat cortical neurons in culture against synaptically released glutamate. Eur J Neurosci 10: 2523-2531. doi: 10.1046/j.1460-9568.1998.00256.x
[138]	Shimamoto K, Lebrun B, Yasuda-Kamatani Y, et al. (1998) DL-threo-beta-benzyloxyaspartate, a potent blocker of excitatory amino acid transporters. Mol Pharmacol 53: 195-201.
[139]	Boudker O, Verdon G (2010) Structural perspectives on secondary active transporters. Trends Pharmacol Sci 31: 418-426. doi: 10.1016/j.tips.2010.06.004
[140]	Shigeri Y, Shimamoto K, Yasuda-Kamatani Y, et al. (2001) Effects of threo-beta-hydroxyaspartate derivatives on excitatory amino acid transporters (EAAT4 and EAAT5). J Neurochem 79: 297-302.
[141]	Shimamoto K, Shigeri Y, Yasuda-Kamatani Y, et al. (2000) Syntheses of optically pure beta-hydroxyaspartate derivatives as glutamate transporter blockers. Bioorg Med Chem Lett 10: 2407-2410. doi: 10.1016/S0960-894X(00)00487-X
[142]	Lebrun B, Sakaitani M, Shimamoto K, et al. (1997) New beta-hydroxyaspartate derivatives are competitive blockers for the bovine glutamate/aspartate transporter. J Biol Chem 272: 20336-20339. doi: 10.1074/jbc.272.33.20336
[143]	Shimamoto K, Sakai R, Takaoka K, et al. (2004) Characterization of novel L-threo-beta-benzyloxyaspartate derivatives, potent blockers of the glutamate transporters. Mol Pharmacol 65: 1008-1015. doi: 10.1124/mol.65.4.1008
[144]	Shimamoto K, Otsubo Y, Shigeri Y, et al. (2007) Characterization of the tritium-labeled analog of L-threo-beta-benzyloxyaspartate binding to glutamate transporters. Mol Pharmacol 71: 294-302.
[145]	Martinov V, Dehnes Y, Holmseth S, et al. (2014) A novel glutamate transporter blocker, LL-TBOA, attenuates ischaemic injury in the isolated, perfused rat heart despite low transporter levels. Eur J Cardiothorac Surg 45: 710-716. doi: 10.1093/ejcts/ezt487
[146]	Dunlop J, Eliasof S, Stack G, et al. (2003) WAY-855 (3-amino-tricyclo[2.2.1.02.6]heptane-1,3-dicarboxylic acid): a novel, EAAT2-preferring, nonsubstrate inhibitor of high-affinity glutamate uptake. Br J Pharmacol 140: 839-846.
[147]	Dunlop J, McIlvain HB, Carrick TA, et al. (2005) Characterization of novel aryl-ether, biaryl, and fluorene aspartic acid and diaminopropionic acid analogs as potent inhibitors of the high-affinity glutamate transporter EAAT2. Mol Pharmacol 68: 974-982. doi: 10.1124/mol.105.012005
[148]	Campiani G, Fattorusso C, De Angelis M, et al. (2003) Neuronal high-affinity sodium-dependent glutamate transporters (EAATs): targets for the development of novel therapeutics against neurodegenerative diseases. Curr Pharm Des 9: 599-625. doi: 10.2174/1381612033391261
[149]	Funicello M, Conti P, De Amici M, et al. (2004) Dissociation of [3H]L-glutamate uptake from L-glutamate-induced [3H]D-aspartate release by 3-hydroxy-4,5,6,6a-tetrahydro-3aH-pyrrolo[3,4-d]isoxazole-4-carboxylic acid and 3-hydroxy-4,5,6,6a-tetrahydro-3aH-pyrrolo[3,4-d]isoxazole-6-carboxylic acid, two conformationally constrained aspartate and glutamate analogs. Mol Pharmacol 66: 522-529.
[150]	Callender R, Gameiro A, Pinto A, et al. (2012) Mechanism of inhibition of the glutamate transporter EAAC1 by the conformationally constrained glutamate analogue (+)-HIP-B. Biochemistry 51: 5486-5495. doi: 10.1021/bi3006048
[151]	Erichsen MN, Huynh TH, Abrahamsen B, et al. (2010) Structure-activity relationship study of first selective inhibitor of excitatory amino acid transporter subtype 1: 2-Amino-4-(4-methoxyphenyl)-7-(naphthalen-1-yl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (UCPH-101). J Med Chem 53: 7180-7191. doi: 10.1021/jm1009154
[152]	Huynh THV, Shim I, Bohr H, et al. (2012) Structure-Activity Relationship Study of Selective Excitatory Amino Acid Transporter Subtype 1 (EAAT1) Inhibitor 2-Amino-4-(4-methoxyphenyl)-7-(naphthalen-1-yl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (UCPH-101) and Absolute Configurational Assignment Using Infrared and Vibrational Circular Dichroism Spectroscopy in Combination with ab Initio Hartree-Fock Calculations. J Med Chem 55: 5403-5412. doi: 10.1021/jm300345z
[153]	Abrahamsen B, Schneider N, Erichsen MN, et al. (2013) Allosteric Modulation of an Excitatory Amino Acid Transporter: The Subtype-Selective Inhibitor UCPH-101 Exerts Sustained Inhibition of EAAT1 through an Intramonomeric Site in the Trimerization Domain. J Neurosci 33: 1068-1087. doi: 10.1523/JNEUROSCI.3396-12.2013
[154]	Rothstein JD, Patel S, Regan MR, et al. (2005) Beta-lactam antibiotics offer neuroprotection by increasing glutamate transporter expression. Nature 433: 73-77. doi: 10.1038/nature03180
[155]	Fontana AC, de Oliveira Beleboni R, Wojewodzic MW, et al. (2007) Enhancing glutamate transport: mechanism of action of Parawixin1, a neuroprotective compound from Parawixia bistriata spider venom. Mol Pharmacol 72: 1228-1237. doi: 10.1124/mol.107.037127
[156]	Fontana ACK, Guizzo R, Beleboni RD, et al. (2003) Purification of a neuroprotective component of Parawixia bistriata spider venom that enhances glutamate uptake. Br J Pharmacol 139: 1297-1309. doi: 10.1038/sj.bjp.0705352
[157]	Xing XC, Chang LC, Kong QM, et al. (2011) Structure-activity relationship study of pyridazine derivatives as glutamate transporter EAAT2 activators. Bioorg Med Chem Lett 21: 5774-5777. doi: 10.1016/j.bmcl.2011.08.009

Reader Comments

Your name:*

Email:*
© 2014 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)