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  • AMPA glutamate receptor subunit 2 in normal and visually deprived macaque visual cortex. 12507323

    Glutamate and its various receptors are known to play an important role in excitatory synaptic transmission throughout the CNS, including the primary visual cortex. Among subunits of the AMPA receptors (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid), subunit 2 (GluR2) is of special significance because it controls their Ca2+ permeability. In the past, this subunit has been studied mostly in conjunction with other AMPA subunits. The present study sought to determine if GluR2 alone has a distinct laminar distribution in the normal macaque visual cortex, and if its pattern correlated with that of cytochrome oxidase (CO) under normal and monocularly deprived conditions. In the normal adult cortex, GluR2 immunoreactivity (ir) had a patchy distribution in layers II/III, in register with CO-rich puffs. GluR2-ir highlighted the upper border of layer II, the lower border of layer IV (previously termed IVC(beta dark)) and, most prominently, layer VI. Labeled neurons were primarily of the pyramidal type present in the upper border and lower half of layer VI, layers II/III, and scattered in layers V and upper IVB. Labeled nonpyramidal cells were large in layer IVB and small in IVC(beta dark). Notably, the bulk of CO-rich layers IVC and IVA had very low levels of GluR2-ir. At fetal day 13, however, GluR2 labeling showed a honeycomb-like pattern in layer IVA not found in the adult. A fragment of GluR2 cDNA was generated from a human cDNA library, and in situ hybridization revealed an expression pattern similar to that of GluR2 proteins. After 1-4 weeks of monocular impulse blockade with tetrodotoxin (TTX), alternating rows of strong and weak GluR2-ir in layers VI and II/III appeared in register with CO-labeled dark and light ocular dominance columns in layer IVC and puffs in II/III, respectively. Our results indicate that various cortical layers are differentially influenced by glutamate. The bulk of the major geniculate-recipient layers IVC and IVA have low levels of GluR2, presumably favoring synaptic transmission via Ca(2+)-permeable glutamate receptors. GluR2 plays a more important role in supragranular and infragranular layers, where the initial geniculate signals are further modified and are transmitted to other cortical and subcortical centers. The maintenance of GluR2 in these output layers is governed by visual input and neuronal activity, as monocular impulse blockade induced a down-regulation of this subunit in deprived ocular dominance columns.
    Document Type:
    Reference
    Product Catalog Number:
    AB1768-25UG

  • Altered glutamate receptor function in the cerebellum of the Ppt1-/- mouse, a murine model of infantile neuronal ceroid lipofuscinosis. 21971706

    The neuronal ceroid lipofuscinoses (NCLs) are a family of devastating pediatric neurodegenerative disorders and currently represent the most common form of pediatric-onset neurodegeneration. Infantile NCL (INCL), the most aggressive of these disorders, is caused by mutations in the CLN1 gene that encodes the enzyme palmitoyl protein thioesterase 1 (PPT1). Previous studies have suggested that glutamatergic neurotransmission may be disrupted in INCL, so the present study investigates glutamate receptor function in the Ppt1(-/-) mouse model of INCL by comparing the sensitivity of cultured wild-type (WT) and Ppt1(-/-) cerebellar granule cells to glutamate receptor-mediated toxicity. Ppt1(-/-) neurons were significantly less sensitive to AMPA receptor-mediated toxicity but markedly more vulnerable to NMDA receptor-mediated cell death. Because glutamate receptor function is regulated primarily by the surface expression level of the receptor, the surface level of AMPA and NMDA receptor subunits in the cerebella of WT and Ppt1(-/-) mice was also examined. Western blotting of surface cross-linked cerebellar samples showed a significantly lower surface level of the GluR4 AMPA receptor subunit in Ppt1(-/-) mice, providing a plausible explanation for the decreased vulnerability of Ppt1(-/-) cerebellar neurons to AMPA receptor-mediated cell death. The surface expression of the NR1, NR2A, and NR2B NMDA receptor subunits was similar in the cerebella of WT and Ppt1(-/-) mice, indicating that there is another mechanism behind the increased sensitivity of Ppt1(-/-) cerebellar granule cells to NMDA toxicity. Our results indicate an AMPA receptor hypofunction and NMDA receptor hyperfunction phenotype in Ppt1(-/-) neurons and provide new therapeutic targets for INCL.
    Document Type:
    Reference
    Product Catalog Number:
    AB1504
    Product Catalog Name:
    Anti-Glutamate receptor 1 Antibody

  • Distribution of glutamate receptor subunits at neurochemically characterized synapses in the entopeduncular nucleus and subthalamic nucleus of the rat. 9674565

    Glutamatergic neurotransmission in the subthalamic nucleus (STN) and in the output nuclei of the basal ganglia is critical in the expression of basal ganglia function, and increased glutamate transmission in these nuclei has been implicated in the pathology of Parkinson's disease. In order to determine the precise spatial relationship of subunits of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) glutamate receptors to nerve terminals enriched in glutamate or gamma-aminobutyric acid (GABA) in one of the output nuclei, the entopeduncular nucleus (EP), and the STN, postembedding immunolabelling for glutamate receptor subunits and for glutamate and GABA was carried out in the rat. Immunolabelling for the AMPA glutamate receptor subunits 1, 2/3, and 4 (GluR1, GluR2/3, and GluR4) and the NMDA receptor subunit 1 (NR1) was localized predominantly within asymmetrical synapses in both the EP and STN. Quantitative analysis revealed that, on average for the whole population, each of the receptor subunits was evenly distributed along the synaptic specialization. Multiple AMPA receptor subunits and the GluR2/3 and NMDA (NR1) subunits were co-localized within individual synapses. The combination of immunolabelling for glutamate and GABA with the receptor immunolabelling revealed that the majority of axon terminals presynaptic to the receptor-immunoreactive synapses were enriched in glutamate immunoreactivity and were GABA-immunonegative. However, at some NR1- and GluR2/3-positive synapses, the level of glutamate immunoreactivity was low in the presynaptic terminal and, in the STN, some of them were GABA-immunopositive. It is concluded that glutamatergic transmission at individual synapses of different origins in the EP and STN is mediated by a combination ofAMPA and NMDA glutamate receptors.
    Document Type:
    Reference
    Product Catalog Number:
    AB1506
    Product Catalog Name:
    Anti-Glutamate Receptor 2 & 3 Antibody

  • Glutamate receptor subunit 2-selective antibody shows a differential distribution of calcium-impermeable AMPA receptors among populations of neurons. 9300771

    Alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are the major excitatory neurotransmitter receptors of the central nervous system. AMPA receptor complexes that contain the AMPA-type glutamate receptor subunit 2 (GluR2) are responsible for the low calcium permeability typical of most AMPA receptors, and the absence of GluR2 may be a key factor in neurotoxicity. A polyclonal antibody was produced to a 16 amino acid peptide near the C-terminus of GluR2 and was affinity-purified in a three-step procedure. The antibody did not recognize other AMPA subunits in transfected cells with the use of either Western blots or immunocytochemistry. This highly specific GluR2 antibody was used to provide a specific morphological study of GluR2 protein distribution in neurons and synapses of the rat. GluR2 is prevalent in most principal neurons throughout the telencephalon. Neurons with few or no GluR2 subunits include two major types: 1) some populations of interneurons of the telencephalon and of some other areas and 2) many populations of principal neurons in the brainstem and spinal cord. Immunofluorescence showed that GluR2 immunolabeling was widespread, including in dendrites and puncta, in the hippocampus and neocortex. Where they were present, GluR2 subunits colocalized with other AMPA receptor subunits in individual neurons. Electron microscopy of the hippocampus showed GluR2-bearing, calcium-impermeable AMPA receptors postsynaptic to dendrite synapses of forebrain principal neurons. In addition, electron microscopy of the neocortex showed significant staining in postsynaptic profiles. Electron microscopy of the cerebellum revealed the presence of GluR2 subunits in the postsynaptic profiles of many parallel fiber/Purkinje cell spine synapses, whereas electron microscopy of the spinal cord showed substantial staining in the postsynaptic profiles of dorsal horn synapses, but not in ventral horn synapses. Both ultrastructural and immunofluorescence data showed that calcium-impermeable AMPA receptors are widespread in dendrite arborizations.
    Document Type:
    Reference
    Product Catalog Number:
    AB1768-25UG

  • Ionotropic glutamate receptor GluR2/3-immunoreactive neurons in the cat, rabbit, and hamster superficial superior colliculus. 15140557

    Ionotropic glutamate receptor (GluR) subtypes occur in various types of cells in the central nervous system. We studied the distribution of AMPA glutamate receptor subtype GluR2/3 in the superficial layers of cat, rabbit, and hamster superior colliculus (SC) with antibody immunocytochemistry and the effect of enucleation on this distribution. Furthermore, we compared this labeling to that of calbindin D28K and parvalbumin. Anti-GluR2/3-immunoreactive (IR) cells formed a dense band of labeled cells within the lower superficial gray layer (SGL) and upper optic layer (OL) in the cat SC. By contrast, GluR2/3-IR cells formed a dense band within the upper OL in the rabbit and within the OL in the hamster SC. Calbindin D28K-IR cells are located in three layers in the SC: one within the zonal layer (ZL) and the upper SGL in all three animals, a second within the lower OL and upper IGL in the cat, within the IGL in the rabbit and within the OL in the hamster, and a third within the deep gray layer (DGL) in all three animals. Many parvalbumin-IR neurons were found within the lower SGL and upper OL. Thus, the GluR2/3-IR band was sandwiched between the first and second layers of calbindin D28K-IR cells in the cat and rabbit SC while the distribution of GluR2/3-IR cells in the hamster matches the second layer of calbindin D28K-IR cells. The patterned distribution of GluR2/3-IR cells overlapped the tier of parvalbumin-IR neurons in cat, but only partially overlapped in hamster and rabbit. Two-color immunofluorescence revealed that more than half (55.1%) of the GluR2/3-IR cells in the hamster SC expressed calbindin D28K. By contrast, only 9.9% of GluR2/3-IR cells expressed calbindin D28K in the cat. Double-labeled cells were not found in the rabbit SC. Some (4.8%) GluR2/3-IR cells in the cat SC also expressed parvalbumin, while no GluR2/3-IR cells in rabbit and hamster SC expressed parvalbumin. In this dense band of GluR2/3, the majority of labeled cells were small to medium-sized round/oval or stellate cells. Immunoreactivity for the GluR2/3 was clearly reduced in the contralateral SC following unilateral enucleation in the hamster. By contrast, enucleation appeared to have had no effect on the GluR2/3 immunoreactivity in the cat and rabbit SC. The results indicate that neurons in the mammalian SC express GluR2/3 in specific layers, which does not correlate with the expression of calbindin D28K and parvalbumin among the animals.
    Document Type:
    Reference
    Product Catalog Number:
    AB1506
    Product Catalog Name:
    Anti-Glutamate Receptor 2 & 3 Antibody

  • Glutamate excitotoxicity is involved in the induction of paralysis in mice after infection by a human coronavirus with a single point mutation in its spike protein. 21957311

    Human coronaviruses (HCoV) are recognized respiratory pathogens, and some strains, including HCoV-OC43, can infect human neuronal and glial cells of the central nervous system (CNS) and activate neuroinflammatory mechanisms. Moreover, HCoV-OC43 is neuroinvasive, neurotropic, and neurovirulent in susceptible mice, where it induces chronic encephalitis. Herein, we show that a single point mutation in the viral spike (S) glycoprotein (Y241H), acquired during viral persistence in human neural cells, led to a hind-limb paralytic disease in infected mice. Inhibition of glutamate excitotoxicity using a 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propranoic acid (AMPA) receptor antagonist (GYKI-52466) improved clinical scores related to the paralysis and motor disabilities in S mutant virus-infected mice, as well as protected the CNS from neuronal dysfunctions, as illustrated by restoration of the phosphorylation state of neurofilaments. Expression of the glial glutamate transporter GLT-1, responsible for glutamate homeostasis, was downregulated following infection, and GYKI-52466 also significantly restored its steady-state expression level. Finally, GYKI-52466 treatment of S mutant virus-infected mice led to reduced microglial activation, which may lead to improvement in the regulation of CNS glutamate homeostasis. Taken together, our results strongly suggest an involvement of excitotoxicity in the paralysis-associated neuropathology induced by an HCoV-OC43 mutant which harbors a single point mutation in its spike protein that is acquired upon persistent virus infection.
    Document Type:
    Reference
    Product Catalog Number:
    AB1783
    Product Catalog Name:
    Anti-Glutamate Transporter Antibody, Glial

  • Glutamate receptor abnormalities in the YAC128 transgenic mouse model of Huntington's disease. 17544587

    A yeast artificial chromosome (YAC) mouse model of Huntington's disease (YAC128) develops motor abnormalities, age-dependent striatal atrophy and neuronal loss. Alteration of neurotransmitter receptors, particularly glutamate and dopamine receptors, is a pathological hallmark of Huntington's disease. We therefore analyzed neurotransmitter receptors in symptomatic YAC128 Huntington's disease mice. We found significant increases in N-methyl-d-aspartate, AMPA and metabotropic glutamate receptor binding, which were not due to increases in receptor subunit mRNA expression levels. Subcellular fractionation analysis revealed increased levels of glutamate receptor subunits in synaptic membrane fractions from YAC128 mice. We found no changes in dopamine, GABA or adenosine receptor binding, nor did we see alterations in dopamine D1, D2 or adenosine A2a receptor mRNA levels. The receptor abnormalities in YAC128 transgenic mice thus appear limited to glutamate receptors. We also found a significant decrease in preproenkephalin mRNA in the striatum of YAC128 mice, which contrasts with the lack of change in levels of mRNA encoding neurotransmitter receptors. Taken together, the abnormal and selective increases in glutamate receptor subunit expression and binding are not due to increases in receptor subunit expression and may exert detrimental effects. The decrease in preproenkephalin mRNA suggests a selective transcriptional deficit, as opposed to neuronal loss, and could additionally contribute to the abnormal motor symptoms in YAC128 mice.
    Document Type:
    Reference
    Product Catalog Number:
    MAB2166
    Product Catalog Name:
    Anti-Huntingtin Protein Antibody, a.a. 181-810, clone 1HU-4C8

  • Glutamate receptor subunit 3 (GluR3) immunoreactivity delineates a subpopulation of parvalbumin-containing interneurons in the rat hippocampus. 12761821

    Rasmussen's encephalitis is a childhood disease resulting in intractable seizures associated with hippocampal and neocortical inflammation. An autoantibody against the GluR3 subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors is implicated in the pathophysiology of Rasmussen's encephalitis. AMPA receptors mediate excitatory neurotransmission in the brain and contain combinations of four subunits (GluR1-4). Although the distributions of GluR1, GluR2, and GluR4 are known in some detail, the cellular distribution of GluR3 in the mammalian brain remains to be described. We developed and characterized a GluR3-specific monoclonal antibody and quantified the cellular distribution of GluR3 in CA1 of the rat hippocampus. GluR3 immunoreactivity was detected in all pyramidal neurons and astrocytes and in most interneurons. We quantified the intensity of GluR3 immunoreactivity in interneuron subtypes defined by their calcium-binding protein content. GluR3 immunofluorescence, but not GluR1 or GluR2 immunofluorescence, was significantly elevated in somata of parvalbumin-containing interneurons compared to pyramidal somata. Strikingly, increased GluR3 immunofluorescence was not observed in calbindin- and calretinin-containing interneurons. Furthermore, 24% of parvalbumin-containing interneurons could be distinguished from surrounding neurons based on their intense GluR3 immunoreactivity. This subpopulation had significantly elevated GluR3 immunoreactivity compared to the rest of parvalbumin-containing interneurons. Electron microscopy revealed enriched GluR3 immunoreactivity in parvalbumin-containing perikarya at cytoplasmic and postsynaptic sites. Parvalbumin-containing interneurons, potent inhibitors of cortical pyramidal neurons, are vulnerable in the brains of epileptic patients. Our findings suggest that the somata of these interneurons are enriched in GluR3, which may render them vulnerable to pathological states such as epilepsy and Rasmussen's encephalitis.
    Document Type:
    Reference
    Product Catalog Number:
    MAB5416
    Product Catalog Name:
    Anti-Glutamate Receptor 3 Antibody, clone 3B3

  • Glutamate receptors on human melanocytes regulate the expression of MiTF. 16420247

    Glutamate is the major excitatory neurotransmitter in the central nervous system but has also important functions in the epidermis. It is involved in keratinocyte barrier function and in re-epithelialization processes after wounding. Recently, glutamate signalling has been suggested to be implicated in the development of melanoma. The present study examined the expression and functionality of metabotropic and ionotropic glutamate receptors on normal human melanocytes. We found that cultured melanocytes expressed the ionotropic glutamate receptors GluR2 and 4 [alpha-amino-3-hydroxy-5-methyl-4-isoxsazolepropionic acid (AMPA) receptors] and N-methyl-d-aspartate (NMDA) receptors 2A and 2C and possibly the metabotropic glutamate receptor 1. Melanocytes were also found to express specific glutamate transporters and decarboxylases, but appeared neither to produce nor to release l-glutamate. Stimulation with 10 or 100 microM AMPA or NMDA elevated intracellular calcium concentrations in melanocytes, and thus demonstrated the functionality of the glutamate receptors. Millimolar concentrations of l-glutamate did not induce melanocyte toxicity and had no stimulating effect on melanin production. However, blockage of AMPA and NMDA receptors with CFM-2, memantine or MK801 caused a rapid and reversible change in melanocyte morphology, which was associated with disorganisation of actin and tubulin microfilaments. After 24 h of treatment with the AMPA receptor inhibitor CFM-2, there was a sharp reduction in the expression of the crucial melanocyte differentiation and proliferation factor MiTF. The results of this study demonstrate a role for glutamate in melanocyte regulation that may have implications in melanocyte associated disorders.
    Document Type:
    Reference
    Product Catalog Number:
    AB1555P
    Product Catalog Name:
    Anti-NMDAR2A Antibody

  • Glutamate receptor subunits GluR1 and GluR2/3 distribution shows reorganization in the human epileptogenic hippocampus. 9751141

    The AMPA-type glutamate receptor subunits GluR1 and GluR2/3 were localized by immunohistochemistry with subunit-specific antibodies in hippocampi removed surgically from patients with temporal lobe epilepsy for the control of seizures. The flip and flop splice variants of the subunits were localized by in situ hybridization histochemistry with specific oligoprobes. In patient hippocampi that were not the seizure focus, the GluR1 subunit proteins were diffusely expressed on the dendrites of neurons in all regions. In contrast, in these same hippocampi, the GluR2/3 subunit proteins were expressed strongly on the soma and proximal dendrites of principal neurons in all regions. The flip variant of these subunits was localized in the hilus and fields of Ammon's Horn (CA), while the flop variants were prominent on the dentate granule cells. In the epileptogenic hippocampus, while immunoreactivity was decreased in all fields that showed neuronal loss, there was an increased expression of GluR1 on the dendritic excrescences on the proximal dendrites of hilar neurons and CA3 pyramidal neurons, as well as expression of GluR2/3 in hilar neuron excrescences. Electron microscopic examination confirmed that the GluR1 immunoreactivity was only in dendritic processes, particularly dense at the postsynaptic membranes. Such expression of GluR1 may provide for an enhanced glutamatergic response by these neurons. GluR2/3 was also significantly increased on the dendrites of dentate granule cells in the epileptogenic hippocampus and may provide some protection against excitotoxic injury by reducing calcium flux into neurons.
    Document Type:
    Reference
    Product Catalog Number:
    AB1506
    Product Catalog Name:
    Anti-Glutamate Receptor 2 & 3 Antibody