Inhibition of uptake unmasks rapid extracellular turnover of glutamate of nonvesicular origin

Jabaudon, Denis; Shimamoto, Keiko; Yasuda-Kamatani, Yoshimi; Scanziani, Massimo; Gähwiler, Beat H.; Gerber, Urs

doi:10.1073/pnas.96.15.8733

Cited by 289 publications

(267 citation statements)

References 32 publications

(29 reference statements)

Supporting

Mentioning

234

Contrasting

Unclassified

Order By: Relevance

“…Regarding extended stimulus trails, the nontransportable inhibitor of glutamate uptake (TBOA; Jabaudon et al, 1999;Shimamoto et al, 1998) did not decrease the overshoot signal after extended stimulation (Figure 10). The concentration of TBOA used here (100 mmol/l) was the same as that used to block glial depolarizations evoked by synaptic stimulation in hippocampal slices (Kawamura et al, 2004).…”

Section: Glutamate Uptakementioning

confidence: 97%

NAD(P)H Fluorescence Transients after Synaptic Activity in Brain Slices: Predominant Role of Mitochondrial Function

Brennan

Connor

Shuttleworth

2006

J Cereb Blood Flow Metab

115

View full text Add to dashboard Cite

Excitatory stimulation in hippocampal slices results in biphasic NAD(P)H fluorescence transients. Previous studies using differing stimulus protocols agreed that the oxidation phase is a consequence of mitochondrial metabolism, but the reduction phase has been attributed to (1) mitochondrial nicotinamide adenine dinucleotide (NADH) generation or (2) astrocytic glycolysis triggered by glutamate uptake. In an attempt to reconcile these two views, the present study examined NAD(P)H signals evoked by a wide range of stimulus durations (40 ms to 20 secs). A combination of ionotropic glutamate receptor (iGluR) antagonists (6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 2-amino-5-phosphonopentanoic acid (APV)) virtually abolished responses to brief stimuli (40 to 200 ms, 50 Hz), but a significant fraction of the signal elicited by extended stimulation (20 secs, 32 Hz) was resistant to CNQX/APV. Glycolysis was inhibited by removal of glucose and addition of 2-deoxyglucose (2DG) (10 mmol/L) or iodoacetic acid (IAA, 1 mmol/L). Pyruvate was provided as an alternative substrate for oxidative phosphorylation and the A1 receptor antagonist 1,3-Dipropyl-8-cyclopentylxanthine (DPCPX) included to prevent decreases in synaptic efficacy. If sufficient pyruvate was supplied, responses to brief and extended stimuli were unaffected by glycolytic inhibition and not significantly reduced by an inhibitor of glucose uptake (3-O-methyl glucose, 3 mmol/L). When timed to arrive at the peak of overshoots generated by extended synaptic stimulation, brief pyruvate applications (10 mmol/L, 2 mins) had little effect on evoked NAD(P)H increases. Flavoprotein autofluorescence transients after extended stimuli matched (with inverted sign) NAD(P)H responses. Responses to extended stimuli were not reduced by a nonselective inhibitor of glutamate uptake DL-Threo-b-benzyloxyaspartic acid (TBOA). These results suggest that NAD(P)H transients report mitochondrial dynamics, rather than recruitment of glycolytic metabolism, over a wide range of stimulus intensities.

show abstract

Section: Glutamate Uptakementioning

confidence: 97%

NAD(P)H Fluorescence Transients after Synaptic Activity in Brain Slices: Predominant Role of Mitochondrial Function

Brennan

Connor

Shuttleworth

2006

J Cereb Blood Flow Metab

115

View full text Add to dashboard Cite

show abstract

“…The compartmentalization of glutamate is likely the result of sodium-dependent glutamate transporters. These transporters are active in clearing glutamate released from cystineglutamate exchange (Baker et al, 2002), and prevents glutamate maintained by nonvesicular release to access synaptic receptors (Jabaudon et al, 1999). To the extent that NR2B receptors are located outside the synapse, this hypothesis is supported by the recent observation that glutamate release from astrocytes appears to stimulate extrasynaptic, but not synaptic NMDA receptors (D'Ascenzo et al, 2007).…”

Section: N-acetylcysteine Reversal Of Psychotomimetic Effects Of Pcpmentioning

confidence: 97%

“…Continuous nonvesicular glutamate release has been detected following NMDA receptor activation, but only after sodium-dependent glutamate transporters were blocked (Jabaudon et al, 1999). This finding indicates that nonvesicular glutamate is released into the extrasynaptic compartment, but that sodium-dependent transporters block entry into the synapse.…”

Section: Introductionmentioning

confidence: 95%

Contribution of Cystine–Glutamate Antiporters to the Psychotomimetic Effects of Phencyclidine

Baker

Madayag

Kristiansen

et al. 2007

Neuropsychopharmacol

View full text Add to dashboard Cite

Altered glutamate signaling contributes to a myriad of neural disorders, including schizophrenia. While synaptic levels are intensely studied, nonvesicular release mechanisms, including cystine-glutamate exchange, maintain high steady-state glutamate levels in the extrasynaptic space. The existence of extrasynaptic receptors, including metabotropic group II glutamate receptors (mGluR), pose nonvesicular release mechanisms as unrecognized targets capable of contributing to pathological glutamate signaling. We tested the hypothesis that activation of cystine-glutamate antiporters using the cysteine prodrug N-acetylcysteine would blunt psychotomimetic effects in the rodent phencyclidine (PCP) model of schizophrenia. First, we demonstrate that PCP elevates extracellular glutamate in the prefrontal cortex, an effect that is blocked by N-acetylcysteine pretreatment. To determine the relevance of the above finding, we assessed social interaction and found that N-acetylcysteine reverses social withdrawal produced by repeated PCP. In a separate paradigm, acute PCP resulted in working memory deficits assessed using a discrete trial t-maze task, and this effect was also reversed by Nacetylcysteine pretreatment. The capacity of N-acetylcysteine to restore working memory was blocked by infusion of the cystineglutamate antiporter inhibitor (S)-4-carboxyphenylglycine into the prefrontal cortex or systemic administration of the group II mGluR antagonist LY341495 indicating that the effects of N-acetylcysteine requires cystine-glutamate exchange and group II mGluR activation. Finally, protein levels from postmortem tissue obtained from schizophrenic patients revealed significant changes in the level of xCT, the active subunit for cystine-glutamate exchange, in the dorsolateral prefrontal cortex. These data advance cystine-glutamate antiporters as novel targets capable of reversing the psychotomimetic effects of PCP.

show abstract

“…Westergren et al, 1994) and glutamate (Herman and Jahr, 2007) despite rapid neurotransmitter release (e.g. Jabaudon et al, 1999).…”

Section: The Expression Levels Required For Physiologically Significamentioning

confidence: 99%

Strategies for immunohistochemical protein localization using antibodies: What did we learn from neurotransmitter transporters in glial cells and neurons

Danbolt

Zhou

Furness

et al. 2016

Glia

View full text Add to dashboard Cite

Immunocytochemistry and Western blotting are still major methods for protein localization, but they rely on the specificity of the antibodies. Validation of antibody specificity remains challenging mostly because ideal negative controls are often unavailable. Further, immunochemical labeling patterns are also influenced by a number of other factors such as postmortem changes, fixation procedures and blocking agents as well as the general assay conditions (e.g., buffers, temperature, etc.). Western blotting similarly depends on tissue collection and sample preparation as well as the electrophoretic separation, transfer to blotting membranes and the immunochemical probing of immobilized molecules. Publication of inaccurate information on protein distribution has downstream consequences for other researchers because the interpretation of physiological and pharmacological observations depends on information on where ion channels, receptors, enzymes or transporters are located. Despite numerous reports, some of which are strongly worded, erroneous localization data are being published. Here we describe the extent of the problem and illustrate the nature of the pitfalls with examples from studies of neurotransmitter transporters. We explain the importance of supplementing immunochemical observations with other measurements (e.g., mRNA levels and distribution, protein activity, mass spectrometry, electrophysiological recordings, etc.) and why quantitative considerations are integral parts of the quality control. Further, we propose a practical strategy for researchers who plan to embark on a localization study. We also share our thoughts about guidelines for quality control. GLIA 2016;64:2045–2064

show abstract

Inhibition of uptake unmasks rapid extracellular turnover of glutamate of nonvesicular origin

Cited by 289 publications

References 32 publications

NAD(P)H Fluorescence Transients after Synaptic Activity in Brain Slices: Predominant Role of Mitochondrial Function

NAD(P)H Fluorescence Transients after Synaptic Activity in Brain Slices: Predominant Role of Mitochondrial Function

Contribution of Cystine–Glutamate Antiporters to the Psychotomimetic Effects of Phencyclidine

Strategies for immunohistochemical protein localization using antibodies: What did we learn from neurotransmitter transporters in glial cells and neurons

Contact Info

Product

Resources

About