Flux coupling in a neuronal glutamate transporter

Zerangue, Noa; Kavanaugh, Michael P.

doi:10.1038/383634a0

Cited by 804 publications

(766 citation statements)

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“…34 Glutamate transport is driven by transmembrane gradient for Na ϩ translocation of every glutamate molecule, which is accompanied by an influx of 3 Na ϩ ions and 1 H ϩ ion, coupled with the efflux of 1 K ϩ ion, making this transport electrogenic. 35 Activation of glutamate transporters is associated with substantial Na ϩ fluxes and increase in [Na ϩ ] i , 36 which serves as a signal for a glucose-lactate shuttle described in the previous section. The excess of intracellular Na ϩ is removed by sodium-calcium exchanger, which is conveniently co-localized with glutamate transporters in perisynaptic processes; increased [Na ϩ ] i turns the exchanger into the reverse mode, thus rapidly reducing cytosolic Na ϩ loads.…”

Section: Brain Homeostasismentioning

confidence: 96%

Astrocytes in Alzheimer's Disease

et al. 2010

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Summary:The circuitry of the human brain is formed by neuronal networks embedded into astroglial syncytia. The astrocytes perform numerous functions, providing for the overall brain homeostasis, assisting in neurogenesis, determining the micro-architecture of the grey matter, and defending the brain through evolutionary conserved astrogliosis programs.Astroglial cells are engaged in neurological diseases by determining the progression and outcome of neuropathological process. Astrocytes are specifically involved in various neurodegenerative diseases, including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and various forms of dementia. Recent evidence suggest that early stages of neurodegenerative processes are associated with atrophy of astroglia, which causes disruptions in synaptic connectivity, disbalance in neurotransmitter homeostasis, and neuronal death through increased excitotoxicity. At the later stages, astrocytes become activated and contribute to the neuroinflammatory component of neurodegeneration.

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Section: Brain Homeostasismentioning

confidence: 96%

Astrocytes in Alzheimer's Disease

et al. 2010

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“…Preexisting gradients of these cations allow accumulation of the amino acid substrate in cells. The type and number of co-or counter-transported cations vary among the members of the glutamate transporter family [3][4][5][6] .…”

Section: R T I C L E Smentioning

confidence: 99%

Conformational heterogeneity of the aspartate transporter GltPh

Hänelt

Wunnicke

Bordignon

et al. 2013

Nat Struct Mol Biol

104

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Glt Ph is a Pyrococcus horikoshii homotrimeric Na + -coupled aspartate transporter that belongs to the glutamate transporter family. Each protomer consists of a trimerization domain involved in subunit interaction and a transporting domain with the substrate-binding site. Here, we have studied the conformational changes underlying transport by Glt Ph using EPR spectroscopy. The trimerization domains form a rigid scaffold, whereas the transporting domains sample multiple conformations, consistent with large-scale movements during the transport cycle. Binding of substrates changed the occupancies of the different conformational states, but the domains remained heterogeneous. The membrane environment favored conformations different from those observed in detergent micelles, but the transporting domain remained structurally heterogeneous in both environments. We conclude that the transporting domains sample multiple conformational states with substantial occupancy regardless of the presence of substrate and coupling ions, consistent with equilibrium constants close to unity between the observed transporter conformations. npg © 2013 Nature America, Inc. All rights reserved.nature structural & molecular biology VOLUME 20 NUMBER 2 FEBRUARY 2013 2 1 1 a r t i c l e s of 160 K to qualitatively extract information on interspin distances <1.8 nm (ref. 14). We analyzed Glt Ph both solubilized in detergent micelles and reconstituted in proteoliposomes and compared the results from each experiment type. The trimerization domain is a stable scaffoldIntroduction of a spin label at a single position in Glt Ph allows for the measurement of the distance between the protomers of the homotrimeric protein. We constructed two trimerization-domain mutants by replacing Thr166 (located in the cytoplasmic end of transmembrane helix 4) and Val176 (located in the cytoplasmic end of helix 5) with an MTSL-modified cysteine (R1). Simulations on the available crystal structures indicated that these spin labels are >1.8 nm apart and therefore suitable for DEER measurements 15 . We did not observe spectral broadening in the CW EPR measurements, which further supports the notion that the spin labels were >1.8 nm apart (Supplementary Fig. 1). We recorded spectra of the apoprotein and of the protein in the presence of saturating concentrations of Na + alone or Na + and aspartate. In agreement with previous biochemical and structural data 12,13 , the trimerization domain did not show any large-scale conformational changes upon addition of coupling ions or substrate (Fig. 2). We observed two sharp peaks (centered around 2.8 nm and 3.8 nm for T166R1 and 2.6 nm and 3.4 nm for V176R1) in the interspin distance distributions for proteins in the presence and absence of substrates. The measured distances were in agreement with the interprotomer distances calculated on the basis of the crystal structures (Table 1 and Fig. 2).Because Glt Ph is a trimer, each mutation resulted in the presence of three cysteines per protein complex, which could result in a cons...

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“…These molecules transport glutamate together with three Na þ and one H þ , coupled to the countertransport of one K þ ion. 9 By transporting ions down their concentration gradients, glutamate can be moved out of the synapse to maintain low extracellular levels. GLAST (EAAT1) is also found in astrocytes, as well as in heart, skeletal muscle and placenta.…”

Section: Clarification Of Nomenclaturementioning

confidence: 99%

EAAT2 regulation and splicing: relevance to psychiatric and neurological disorders

Lauriat

McInnes

2007

Mol Psychiatry

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The excitatory amino acid transporter 2 (EAAT2) is responsible for the majority of glutamate uptake in the brain and its dysregulation has been associated with multiple psychiatric and neurological disorders. However, investigation of this molecule has been complicated by its complex pattern of alternative splicing, including three coding isoforms and multiple 5 0 -and 3 0 -UTRs that may have a regulatory function. It is likely that these sequences permit modulation of EAAT2 expression with spatial, temporal and or activity-dependent specificity; however, few studies have attempted to delineate the function of these sequences. Additionally, there are problems with the use of antibodies to study protein localization, possibly due to posttranslational modification of critical amino acid residues. This review describes what is currently known about the regulation of EAAT2 mRNA and protein isoforms and concludes with a summary of studies showing dysregulation of EAAT2 in psychiatric and neurological disorders. EAAT2 has been either primarily or secondarily implicated in a multitude of neuropsychiatric diseases in addition to the normal physiology of learning and memory. Thus, this molecule represents an intriguing therapeutic target once we improve our understanding of how it is regulated under normal conditions.

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Flux coupling in a neuronal glutamate transporter

Cited by 804 publications

References 28 publications

Astrocytes in Alzheimer's Disease

Astrocytes in Alzheimer's Disease

Conformational heterogeneity of the aspartate transporter GltPh

EAAT2 regulation and splicing: relevance to psychiatric and neurological disorders

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