Browse
Submit Data
Databases
API
Help

Dataset Information

14 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Regulation of glutamate transport in developing rat oligodendrocytes.

ABSTRACT: Glutamate released from synaptic vesicles mediates excitatory neurotransmission by stimulating glutamate receptors. Glutamate transporters maintain low synaptic glutamate levels critical for this process, a role primarily attributed to astrocytes. Recently, vesicular release of glutamate from unmyelinated axons in the rat corpus callosum has been shown to elicit AMPA receptor-mediated currents in glial progenitor cells. Glutamate transporters are the only mechanism of glutamate clearance, yet very little is known about the role of glutamate transporters in normal development of oligodendrocytes (OLs) or in excitotoxic injury to OLs. We found that OLs in culture are capable of sodium-dependent glutamate uptake with a K(m) of 10 +/- 2 microm and a V(max) of 2.6, 5.0, and 3.8 nmol x min(-1) x mg(-1) for preoligodendrocytes, immature, and mature OLs, respectively. Surprisingly, EAAC1, thought to be exclusively a neuronal transporter, contributes more to [(3)H]l-glutamate uptake in OLs than GLT1 or GLAST. These data suggest that glutamate transporters on oligodendrocytes may serve a critical role in maintaining glutamate homeostasis at a time when unmyelinated callosal axons are engaging in glutamatergic signaling with glial progenitors. Furthermore, GLT1 was significantly increased in cultured mature OLs contrary to in vivo data in which we have shown that, although GLT1 is present on developing OLs when unmyelinated axons are prevalent in the developing rat corpus callosum, after myelination, GLT1 is not expressed on mature OLs. The absence of GLT1 in mature OLs in the rat corpus callosum and its presence in mature rat cultured OLs may indicate that a signaling process in vivo is not activated in vitro.

SUBMITTER: DeSilva TM

PROVIDER: S-EPMC2926807 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Ion transport and regulation in a synaptic vesicle glutamate transporter.

Project description:Synaptic vesicles accumulate neurotransmitters, enabling the quantal release by exocytosis that underlies synaptic transmission. Specific neurotransmitter transporters are responsible for this activity and therefore are essential for brain function. The vesicular glutamate transporters (VGLUTs) concentrate the principal excitatory neurotransmitter glutamate into synaptic vesicles, driven by membrane potential. However, the mechanism by which they do so remains poorly understood owing to a lack of structural information. We report the cryo-electron microscopy structure of rat VGLUT2 at 3.8-angstrom resolution and propose structure-based mechanisms for substrate recognition and allosteric activation by low pH and chloride. A potential permeation pathway for chloride intersects with the glutamate binding site. These results demonstrate how the activity of VGLUTs can be coordinated with large shifts in proton and chloride concentrations during the synaptic vesicle cycle to ensure normal synaptic transmission.

| S-EPMC7388591 | biostudies-literature

Glutamate receptor-mediated toxicity in optic nerve oligodendrocytes.

Project description:In cultured oligodendrocytes isolated from perinatal rat optic nerves, we have analyzed the expression of ionotropic glutamate receptor subunits as well as the effect of the activation of these receptors on oligodendrocyte viability. Reverse transcription-PCR, in combination with immunocytochemistry, demonstrated that most oligodendrocytes differentiated in vitro express the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluR3 and GluR4 and the kainate receptor subunits GluR6, GluR7, KA1 and KA2. Acute and chronic exposure to kainate caused extensive oligodendrocyte death in culture. This effect was partially prevented by the AMPA receptor antagonist GYKI 52466 and was completely abolished by the non-N-methyl-D-aspartate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), suggesting that both AMPA and kainate receptors mediate the observed kainate toxicity. Furthermore, chronic application of kainate to optic nerves in vivo resulted in massive oligodendrocyte death which, as in vitro, could be prevented by coinfusion of the toxin with CNQX. These findings suggest that excessive activation of the ionotropic glutamate receptors expressed by oligodendrocytes may act as a negative regulator of the size of this cell population.

| S-EPMC23152 | biostudies-literature

Transcriptional regulation of MHC class I gene expression in rat oligodendrocytes.

Project description:MHC class I molecules are normally expressed at very low levels in the brain and their up-regulation in response to cytokines and viral infections has been associated with a number of neurological disorders. Here we demonstrate that the down-regulation of surface class I molecules in differentiated primary rat oligodendrocytes was accompanied by reduced steady-state levels of class I heavy-chain mRNA. Transient expression assays were performed in oligodendrocytes and fibroblasts, using a mouse H-2Kb class I promoter chloramphenicol acetyltransferase plasmid termed pH2KCAT (which contained 5'-flanking sequences from -2033 to +5 bp of the H-2Kb gene relative to the transcriptional start site at +1 bp). These assays showed that H-2Kb promoter activity was reduced in oligodendrocytes but not in class I-expressing fibroblasts. H-2Kb promoter activity was up-regulated in oligodendrocytes co-transfected with a plasmid expression vector encoding the transcriptional activator tax of human T-cell leukaemia virus type I, showing that down-regulation of promoter activity was reversible. Deletion mutant analysis of the H-2Kb promoter revealed the presence of negative regulatory elements that were functional in oligodendrocytes at -1.61 to -1.07 kb and -242 to -190 bp. Deletion of sequences in pH2KCAT encompassing the downstream element totally abolished promoter activity in both oligodendrocytes and fibroblasts, whereas a deletion within the upstream negative regulatory element increased promoter activity specifically in oligodendrocytes. The upstream negative regulatory element also down-regulated a linked heterologous herpes simplex virus thymidine kinase promoter in oligodendrocytes, but not in fibroblasts. Gel retardation assays using overlapping DNA probes that spanned the entire -1.61 to -1.07 kb region revealed the presence of a number of DNA-binding activities that were present in oligodendrocyte, but not in fibroblast nuclear extracts.

| S-EPMC1219121 | biostudies-other

Presynaptic regulation of quantal size: K+/H+ exchange stimulates vesicular glutamate transport.

Project description:The amount of neurotransmitter stored in a single synaptic vesicle can determine the size of the postsynaptic response, but the factors that regulate vesicle filling are poorly understood. A proton electrochemical gradient (??(H+)) generated by the vacuolar H(+)-ATPase drives the accumulation of classical transmitters into synaptic vesicles. The chemical component of ??(H+) (?pH) has received particular attention for its role in the vesicular transport of cationic transmitters as well as in protein sorting and degradation. Thus, considerable work has addressed the factors that promote ?pH. However, synaptic vesicle uptake of the principal excitatory transmitter glutamate depends on the electrical component of ??(H+) (??). We found that rat brain synaptic vesicles express monovalent cation/H(+) exchange activity that converts ?pH into ??, and that this promotes synaptic vesicle filling with glutamate. Manipulating presynaptic K(+) at a glutamatergic synapse influenced quantal size, indicating that synaptic vesicle K(+)/H(+) exchange regulates glutamate release and synaptic transmission.

| S-EPMC3183113 | biostudies-literature

Glutamate metabolism and transport in rat brain mitochondria.

Project description:1. The metabolism and transport of glutamate and glutamine in rat brain mitochondria of non-synaptic origin has been studied in various states. 2. These mitochondria exhibited glutamate uptake and swelling in iso-osmotic ammonium glutamate, both of which were inhibited by N-ethylmaleimide. 3. The oxidation of glutamate was inhibited by 20% by avenaciolide, but glutamine oxidation was not affected. 4. These mitochondria, when metabolizing glutamine, allowed glutamate, but very little aspartate, to efflux at considerable rates. 5. These results suggests that brain mitochondria of non-synaptic origin possess in addition to a relatively rapid glutamate-aspartate translocase, a relatively slow aspartate-independent glutamate-OH-translocase (cf. liver mitochondria).

| S-EPMC1163752 | biostudies-other

Glutamate and aspartate transport in rat brain mitochondria.

Project description:1. Rat brain mitochondria did not swell in iso-osmotic solutions of ammonium or potassium (plus valinomycin) glutamate or aspartate, with or without addition of uncouplers. 2. Glutamate was able to reduce intramitochondrial NAD(P)(+); aspartate was able to cause partial re-oxidation. 3. These effects were inhibited by threo-hydroxy-aspartate in whole but not in lysed mitochondria. 4. The existence of a ;malate-aspartate shuttle' for the oxidation of extramitochondrial NADH was demonstrated. This shuttle requires the net exchange of glutamate for aspartate across the mitochondrial membrane. 5. Extramitochondrial glutamate did not inhibit intramitochondrial glutaminase under conditions in which the inhibition in lysed mitochondria was virtually complete. 6. The glutaminase activity of these mitochondria was not energy-dependent. 7. We conclude that these mitochondria do not possess a glutamate-hydroxyl antiporter similar to that of liver mitochondria nor a glutamate-glutamine antiporter similar to that of pig kidney mitochondria, but that they do possess a glutamate-aspartate antiporter.

| S-EPMC1167992 | biostudies-other

Oligodendrocytes support axonal transport and maintenance via exosome secretion.

Project description:Neurons extend long axons that require maintenance and are susceptible to degeneration. Long-term integrity of axons depends on intrinsic mechanisms including axonal transport and extrinsic support from adjacent glial cells. The mechanisms of support provided by myelinating oligodendrocytes to underlying axons are only partly understood. Oligodendrocytes release extracellular vesicles (EVs) with properties of exosomes, which upon delivery to neurons improve neuronal viability in vitro. Here, we show that oligodendroglial exosome secretion is impaired in 2 mouse mutants exhibiting secondary axonal degeneration due to oligodendrocyte-specific gene defects. Wild-type oligodendroglial exosomes support neurons by improving the metabolic state and promoting axonal transport in nutrient-deprived neurons. Mutant oligodendrocytes release fewer exosomes, which share a common signature of underrepresented proteins. Notably, mutant exosomes lack the ability to support nutrient-deprived neurons and to promote axonal transport. Together, these findings indicate that glia-to-neuron exosome transfer promotes neuronal long-term maintenance by facilitating axonal transport, providing a novel mechanistic link between myelin diseases and secondary loss of axonal integrity.

| S-EPMC7787684 | biostudies-literature

The mechanism and regulation of vesicular glutamate transport: Coordination with the synaptic vesicle cycle.

Project description:The transport of classical neurotransmitters into synaptic vesicles generally relies on a H+ electrochemical gradient (∆μH+). Synaptic vesicle uptake of glutamate depends primarily on the electrical component ∆ψ as the driving force, rather than the chemical component ∆pH. However, the vesicular glutamate transporters (VGLUTs) belong to the solute carrier 17 (SLC17) family, which includes closely related members that function as H+ cotransporters. Recent work has also shown that the VGLUTs undergo allosteric regulation by H+ and Cl-, and exhibit an associated Cl- conductance. These properties appear to coordinate VGLUT activity with the large ionic shifts that accompany the rapid recycling of synaptic vesicles driven by neural activity. Recent structural information also suggests common mechanisms that underlie the apparently divergent function of SLC17 family members, and that confer allosteric regulation.

| S-EPMC7483692 | biostudies-literature

Quantitative characteristics of glutamate transport in rat liver mitochondria.

Project description:1. The kinetics of glutamate transport into mitochondria were determined by using Bromocresol Purple to terminate the transport process. 2. Glutamate transport was found to have a V(max.) of 9.1nmol/min per mg of protein at pH6.9 and 20 degrees C; the K(m) for glutamate was 4mm. 3. The rate of glutamate deamination in intact mitochondria was tenfold slower than in disrupted mitochondria. 4. These results suggest that glutamate deamination may be controlled by the rate of glutamate transport. Possible consequences of these findings are discussed.

| S-EPMC1177911 | biostudies-other

The Neuroactive Steroid Pregnanolone Glutamate: Anticonvulsant Effect, Metabolites and Its Effect on Neurosteroid Levels in Developing Rat Brains.

Project description:Pregnanolone glutamate (PA-G) is a neuroactive steroid that has been previously demonstrated to be a potent neuroprotective compound in several biological models in vivo. Our in vitro experiments identified PA-G as an inhibitor of N-methyl-D-aspartate receptors and a potentiator of γ-aminobutyric acid receptors (GABAARs). In this study, we addressed the hypothesis that combined GABAAR potentiation and NMDAR antagonism could afford a potent anticonvulsant effect. Our results demonstrated the strong age-related anticonvulsive effect of PA-G in a model of pentylenetetrazol-induced seizures. PA-G significantly decreased seizure severity in 12-day-old animals, but only after the highest dose in 25-day-old animals. Interestingly, the anticonvulsant effect of PA-G differed both qualitatively and quantitatively from that of zuranolone, an investigational neurosteroid acting as a potent positive allosteric modulator of GABAARs. Next, we identified 17-hydroxy-pregnanolone (17-OH-PA) as a major metabolite of PA-G in 12-day-old animals. Finally, the administration of PA-G demonstrated direct modulation of unexpected neurosteroid levels, namely pregnenolone and dehydroepiandrosterone sulfate. These results suggest that compound PA-G might be a pro-drug of 17-OH-PA, a neurosteroid with a promising neuroprotective effect with an unknown mechanism of action that may represent an attractive target for studying perinatal neural diseases.

| S-EPMC8780580 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data