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Major Excitatory Neurotransmitter (major + excitatory_neurotransmitter)
Selected AbstractsPhysiological requirement for the glutamate transporter dEAAT1 at the adult Drosophila neuromuscular junctionDEVELOPMENTAL NEUROBIOLOGY, Issue 10 2006Thomas Rival Abstract L -Glutamate is the major excitatory neurotransmitter in the mammalian brain. Specific proteins, the Na+/K+ -dependent high affinity excitatory amino acid transporters (EAATs), are involved in the extracellular clearance and recycling of this amino acid. Type I synapses of the Drosophila neuromuscular junction (NMJ) similarly use L -glutamate as an excitatory transmitter. However, the localization and function of the only high-affinity glutamate reuptake transporter in Drosophila, dEAAT1, at the NMJ was unknown. Using a specific antibody and transgenic strains, we observed that dEAAT1 is present at the adult, but surprisingly not at embryonic and larval NMJ, suggesting a physiological maturation of the junction during metamorphosis. We found that dEAAT1 is not localized in motor neurons but in glial extensions that closely follow motor axons to the adult NMJ. Inactivation of the dEAAT1 gene by RNA interference generated viable adult flies that were able to walk but were flight-defective. Electrophysiological recordings of the thoracic dorso-lateral NMJ were performed in adult dEAAT1-deficient flies. The lack of dEAAT1 prolonged the duration of the individual responses to motor nerve stimulation and this effect was progressively increased during physiological trains of stimulations. Therefore, glutamate reuptake by glial cells is required to ensure normal activity of the Drosophila NMJ, but only in adult flies. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Role of the GLT-1 subtype of glutamate transporter in glutamate homeostasis: the GLT-1-preferring inhibitor WAY-855 produces marginal neurotoxicity in the rat hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005Julie V. Selkirk Abstract Glutamate is the major excitatory neurotransmitter in the central nervous system and is tightly regulated by cell surface transporters to avoid increases in concentration and associated neurotoxicity. Selective blockers of glutamate transporter subtypes are sparse and so knock-out animals and antisense techniques have been used to study their specific roles. Here we used WAY-855, a GLT-1-preferring blocker, to assess the role of GLT-1 in rat hippocampus. GLT-1 was the most abundant transporter in the hippocampus at the mRNA level. According to [3H]- l -glutamate uptake data, GLT-1 was responsible for approximately 80% of the GLAST-, GLT-1-, and EAAC1-mediated uptake that occurs within dissociated hippocampal tissue, yet when this transporter was preferentially blocked for 120 h with WAY-855 (100 µm), no significant neurotoxicity was observed in hippocampal slices. This is in stark contrast to results obtained with TBOA, a broad-spectrum transport blocker, which, at concentrations that caused a similar inhibition of glutamate uptake (10 and 30 µm), caused substantial neuronal death when exposed to the slices for 24 h or longer. Likewise, WAY-855, did not significantly exacerbate neurotoxicity associated with simulated ischemia, whereas TBOA did. Finally, intrahippocampal microinjection of WAY-855 (200 and 300 nmol) in vivo resulted in marginal damage compared with TBOA (20 and 200 nmol), which killed the majority of both CA1,4 pyramidal cells and dentate gyrus granule cells. These results indicate that selective inhibition of GLT-1 is insufficient to provoke glutamate build-up, leading to NMDA receptor-mediated neurotoxic effects, and suggest a prominent role of GLAST and/or EAAC1 in extracellular glutamate maintenance. [source] Necrostatin-1 protects against glutamate-induced glutathione depletion and caspase-independent cell death in HT-22 cellsJOURNAL OF NEUROCHEMISTRY, Issue 5 2007Xingshun Xu Abstract Glutamate, a major excitatory neurotransmitter in the CNS, plays a critical role in neurological disorders such as stroke and Parkinson's disease. Recent studies have suggested that glutamate excess can result in a form of cell death called glutamate-induced oxytosis. In this study, we explore the protective effects of necrostatin-1 (Nec-1), an inhibitor of necroptosis, on glutamate-induced oxytosis. We show that Nec-1 inhibits glutamate-induced oxytosis in HT-22 cells through a mechanism that involves an increase in cellular glutathione (GSH) levels as well as a reduction in reactive oxygen species production. However, Nec-1 had no protective effect on free radical-induced cell death caused by hydrogen peroxide or menadione, which suggests that Nec-1 has no antioxidant effects. Interestingly, the protective effect of Nec-1 was still observed when cellular GSH was depleted by buthionine sulfoximine, a specific and irreversible inhibitor of glutamylcysteine synthetase. Our study further demonstrates that Nec-1 significantly blocks the nuclear translocation of apoptosis-inducing factor (a marker of caspase-independent programmed cell death) and inhibits the integration of Bcl-2/adenovirus E1B 19 kDa-interacting protein 3 (a pro-death member of the Bcl-2 family) into the mitochondrial membrane. Taken together, these results demonstrate for the first time that Nec-1 prevents glutamate-induced oxytosis in HT-22 cells through GSH related as well as apoptosis-inducing factor and Bcl-2/adenovirus E1B 19 kDa-interacting protein 3-related pathways. [source] Glutamate activation of Oct-2 in cultured chick Bergmann glia cells: Involvement of NF,BJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2005J. Alfredo Méndez Abstract Glutamate, the major excitatory neurotransmitter in the central nervous system, is critically involved in gene expression regulation at the transcriptional and translational levels. Its activity through ionotropic as well as metabotropic receptors modifies the protein repertoire in neurons and glial cells. In avian cerebellar Bergmann glia cells, glutamate receptors trigger a diverse array of signaling cascades that include activity-dependent transcription factors such as the activator protein-1, the cAMP response-element binding protein, and Oct-2. We analyze the upstream regulatory elements involved in Oct-2 activation. Our results demonstrate that Ca2+ influx, protein kinase C, phosphatidylinositol-3 kinase, Src, and nuclear factor (NF),B are involved in this signaling pathway. Our findings link ,-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor activation to a negative phase of chkbp gene regulation, controlled by NF,B. © 2005 Wiley-Liss, Inc. [source] Subtype selective kainic acid receptor agonists: Discovery and approaches to rational designMEDICINAL RESEARCH REVIEWS, Issue 1 2009Lennart Bunch Abstract (S)-Glutamic acid (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system, activating the plethora of glutamate receptors (GluRs). In broad lines, the GluRs are divided into two major classes: the ionotropic Glu receptors (iGluRs) and the metabotropic Glu receptors (mGluRs). Within the iGluRs, five subtypes (KA1, KA2, iGluR5-7) show high affinity and express full agonist activity upon binding of the naturally occurring amino acid kainic acid (KA). Thus these receptors have been named the KA receptors. This review describes all,to our knowledge,published KA receptor agonists. In total, over 100 compounds are described by means of chemical structure and available pharmacological data. With this perspective review, it is our intention to ignite and stimulate inspiration for future design and synthesis of novel subtype selective KA receptor agonists. © 2008 Wiley Periodicals, Inc. Med Res Rev, 29, No. 1, 3,28, 2009 [source] Competitive AMPA receptor antagonistsMEDICINAL RESEARCH REVIEWS, Issue 2 2007Daniela Catarzi Abstract Glutamic acid (Glu) is the major excitatory neurotransmitter in the mammalian central nervous system (CNS) where it is involved in the physiological regulation of different processes. It has been well established that excessive endogenous Glu is associated with many acute and chronic neurodegenerative disorders such as cerebral ischaemia, epilepsy, amiotrophic lateral sclerosis, Parkinson's, and Alzheimer's disease. These data have consequently added great impetus to the research in this field. In fact, many Glu receptor antagonists acting at the N -methyl- D -aspartic acid (NMDA), 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA), and/or kainic acid (KA) receptors have been developed as research tools and potential therapeutic agents. Ligands showing competitive antagonistic action at the AMPA type of Glu receptors were first reported in 1988, and the systemically active 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo[f]quinoxaline (NBQX) was first shown to have useful therapeutic effects in animal models of neurological disease in 1990. Since then, the quinoxaline template has represented the backbone of various competitive AMPA receptor antagonists belonging to different classes which had been developed in order to increase potency, selectivity and water solubility, but also to prolong the "in vivo" action. Compounds that present better pharmacokinetic properties and less serious adverse effects with respect to the others previously developed are undergoing clinical evaluation. In the near future, the most important clinical application for the AMPA receptor antagonists will probably be as neuroprotectant in neurodegenerative diseases, such as epilepsy, for the treatment of patients not responding to current therapies. The present review reports the history of competitive AMPA receptor antagonists from 1988 up to today, providing a systematic coverage of both the open and patent literature. © 2006 Wiley Periodicals, Inc. [source] Docking and homology modeling explain inhibition of the human vesicular glutamate transportersPROTEIN SCIENCE, Issue 9 2007Jonas Almqvist Abstract As membrane transporter proteins, VGLUT1,3 mediate the uptake of glutamate into synaptic vesicles at presynaptic nerve terminals of excitatory neural cells. This function is crucial for exocytosis and the role of glutamate as the major excitatory neurotransmitter in the central nervous system. The three transporters, sharing 76% amino acid sequence identity in humans, are highly homologous but differ in regional expression in the brain. Although little is known regarding their three-dimensional structures, hydropathy analysis on these proteins predicts 12 transmembrane segments connected by loops, a topology similar to other members in the major facilitator superfamily, where VGLUT1,3 have been phylogenetically classified. In this work, we present a three-dimensional model for the human VGLUT1 protein based on its distant bacterial homolog in the same superfamily, the glycerol-3-phosphate transporter from Escherichia coli. This structural model, stable during molecular dynamics simulations in phospholipid bilayers solvated by water, reveals amino acid residues that face its pore and are likely to affect substrate translocation. Docking of VGLUT1 substrates to this pore localizes two different binding sites, to which inhibitors also bind with an overall trend in binding affinity that is in agreement with previously published experimental data. [source] Expression, purification, crystallization and preliminary X-ray analysis of the ligand-binding domain of metabotropic glutamate receptor 7ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2007Takanori Muto Glutamate is the major excitatory neurotransmitter and its metabotropic glutamate receptor (mGluR) plays an important role in the central nervous system. The ligand-binding domain (LBD) of mGluR subtype 7 (mGluR7) was produced using the baculovirus expression system and purified from the culture medium. The purified protein was characterized by gel-filtration chromatography, SDS,PAGE and a ligand-binding assay. Crystals of mGluR7 LBD were grown at 293,K by the hanging-drop vapour-diffusion method. The crystals diffracted X-rays to 3.30,Å resolution using synchrotron radiation and belong to the trigonal space group P3121, with unit-cell parameters a = b = 92.4, c = 114.3,Å. Assuming the presence of one protomer per crystallographic asymmetric unit, the Matthews coefficient VM was calculated to be 2.5,Å3,Da,1 and the solvent content was 51%. [source] | |||||||||||||