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Glutamate Receptor Subunit (glutamate + receptor_subunit)
Selected AbstractsGlutamate Receptor Subunit ,2 Is Highly Expressed in a Novel Population of Glial-Like Cells in Rat Pineal Glands in CultureJOURNAL OF NEUROCHEMISTRY, Issue 3 2000Shouki Yatsushiro Abstract: The mammalian pineal gland uses L-glutamate as an intercellular chemical transmitter to regulate negatively melatonin synthesis. To receive glutamate signals, pinealocytes express at least three kinds of glutamate receptors: metabotropic receptor types 3 and 5 and an ionotropic receptor, GluR1. In this study, we examined whether or not the fourth class of ionotropic receptor, ,, which is known for its nondefinitive molecular function and its unique expression pattern in brain, is expressed in pineal gland. RT-PCR analyses with specific probes indicated the expression of mRNA of ,2 but not that of ,1 in pineal gland and cultured pineal cells. Western blotting analysis with polyclonal antibodies specific to the carboxyl-terminal region of the ,2 receptor recognized a single 110-kDa polypeptide of cerebellar membranes and specifically immunostained Purkinje cells. The ,2 antibodies recognized a 110-kDa polypeptide of pineal membranes and specifically immunostained huge glial-like cells with the occasional presence of several long, branching processes in a pineal cell culture. ,2 is not uniformly distributed throughout the cells and is relatively abundant at the periphery of the cell bodies and long processes, where the terminals of synaptophysin-positive processes of pinealocytes, a site for glutamate secretion, are frequently present. The ,2-positive cells constitute a very minor population among total pineal cells (,0.03%). Double immunolabeling with ,2 antibodies and antibodies against marker proteins for pineal interstitial cells clearly distinguishes ,2-positive pineal cells and other known interstitial cells, including glial fibrillary acidic protein- or vimentin-positive glial-like cells. These results indicated that the ,2 glutamate receptor is expressed in a novel subpopulation of pineal glial-like cells in culture and suggest the presence of a glutamate-mediated intercellular signal transduction mechanism between pinealocytes and ,2-expressing cells. The pineal cells may provide a good experimental system for studies on the function of glutamate receptor ,2. [source] Critical and sensitive periods for reversing the effects of mechanosensory deprivation on behavior, nervous system, and development in Caenorhabditis elegansDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2007Susan Rai Abstract In these studies the nematode Caenorhabditis elegans was used as a model to investigate ways to reverse the effects of mechanosensory deprivation on behavior and development. Rose et al. (J Neurosci 2005; 25:7159,7168) showed that worms reared in isolation responded significantly less to a mechanical tap stimulus, were significantly smaller, and expressed significantly lower levels of a postsynaptic glutamate receptor subunit on the command interneurons of the tap response circuit and a presynaptic vesicle marker in the tap sensory neurons compared with worms raised in groups. Here, brief mechanical stimulation at any time throughout development reversed the effects of isolation on the response to tap and on postsynaptic glutamate receptor expression on the command interneurons, suggesting there is no critical period for these measures. In contrast to the high level of plasticity in glutamate receptor subunit expression on the interneurons, low levels of stimulation only rescued vesicle expression in the tap sensory neurons early in development and progressively higher levels of stimulation were required as the worm developed, suggesting a sensitive period immediately after hatching, followed by a period of decreasing plasticity. Stimulation during the first three stages of larval development, but not later, rescued the effects of isolation on worm length, suggesting there is a critical period for this measure that ends in the third larval stage. These results indicate that different effects of early isolation required different amounts and/or timing of stimulation to be reversed. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Synaptic plasticity and functionality at the cone terminal of the developing zebrafish retinaDEVELOPMENTAL NEUROBIOLOGY, Issue 3 2003Oliver Biehlmaier Abstract Previous studies have analyzed photoreceptor development, some inner retina cell types, and specific neurotransmitters in the zebrafish retina. However, only minor attention has been paid to the morphology of the synaptic connection between photoreceptors and second order neurons even though it represents the transition from the light sensitive receptor to the neuronal network of the visual system. Here, we describe the appearance and differentiation of pre- and postsynaptic elements at cone synapses in the developing zebrafish retina together with the maturation of the directly connecting second order neurons and a dopaminergic third order feedback-neuron from the inner retina. Zebrafish larvae were examined at developmental stages from 2 to 7dpf (days postfertilization) and in the adult. Synaptic maturation at the photoreceptor terminals was examined with antibodies against synapse associated proteins. The appearance of synaptic plasticity at the so-called spinule-type synapses between cones and horizontal cells was assessed by electron microscopy, and the maturation of photoreceptor downstream connection was identified by immunocytochemistry for GluR4 (AMPA-type glutamate receptor subunit), protein kinase ,1 (mixed rod-cone bipolar cells), and tyrosine hydroxylase (dopaminergic interplexiform cells). We found that developing zebrafish retinas possess first synaptic structures at the cone terminal as early as 3.5dpf. Morphological maturation of these synapses at 3.5,4dpf, together with the presence of synapse associated proteins at 2.5dpf and the maturation of second order neurons by 5dpf, indicate functional synaptic connectivity and plasticity between the cones and their second order neurons already at 5dpf. However, the mere number of spinules and ribbons at 7dpf still remains below the adult values, indicating that synaptic functionality of the zebrafish retina is not entirely completed at this stage of development. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 222,236, 2003 [source] Requirement of the tumour suppressor APC for the clustering of PSD-95 and AMPA receptors in hippocampal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2007Atsushi Shimomura Abstract Mutations in the adenomatous polyposis coli (APC) gene are associated with familial adenomatous polyposis and sporadic colorectal tumours. The APC gene is expressed ubiquitously in various tissues, especially throughout the large intestine and central nervous system (CNS). In the CNS, the expression of the APC protein is highest during embryonic and early postnatal development. APC associates through its C-terminal region with postsynaptic density (PSD)-95, a neuronal protein that participates in synapse development. Here, we examined the involvement of APC in synaptogenesis. In cultured hippocampal neurons, both overexpression of a dominant-negative construct that disrupts the APC,PSD-95 interaction and knockdown of APC expression using small interfering RNA (siRNA) inhibited the clustering of PSD-95 and a glutamate receptor subunit, and reduced alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA)-induced activity of AMPA receptors; however, the clustering of an N -methyl- d -aspartate (NMDA) receptor subunit was unaffected. These results are suggestive of APC involvement in the development of glutamatergic synapses. [source] Impairment of eyeblink conditioning in GluR,2-mutant mice depends on the temporal overlap between conditioned and unconditioned stimuliEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2001Yasushi Kishimoto Abstract Mice lacking the glutamate receptor subunit ,2 (GluR,2) are deficient in cerebellar long-term depression (LTD) at the parallel fibre,Purkinje cell synapses. We conducted delay and trace eyeblink conditioning with these mice, using various temporal intervals between the conditioned stimulus (CS) and unconditioned stimulus (US). During trace conditioning in which a stimulus-free trace interval (TI) of 250, 100 or 50 ms intervened between the 352-ms tone CS and 100-ms US, GluR,2-mutant mice learned as successfully as wild-type mice. Even in the paradigm with TI = 0 ms, in which the end of CS and onset of US are simultaneous, there was no difference between the GluR,2-mutant and wild-type mice in their acquisition of a conditioned response. However, in the delay paradigm in which the 452-ms CS overlapped temporally with the coterminating 100-ms US, GluR,2-mutant mice exhibited severe learning impairment. The present study together with our previous work [Kishimoto, Y., Kawahara, S., Suzuki, M., Mori, H., Mishina, M. & Kirino, Y. (2001) Eur. J. Neurosci.,13, 1249,1254], indicates that cerebellar LTD-independent learning is possible in paradigms without temporal overlap between the CS and US. On the other hand, GluR,2 and cerebellar LTD are essential for learning when there is CS,US temporal overlap, suggesting that the cerebellar neural substrates underlying eyeblink conditioning may change, depending on the temporal overlap of the CS and US. [source] NSF binds calcium to regulate its interaction with AMPA receptor subunit GluR2JOURNAL OF NEUROCHEMISTRY, Issue 6 2007Jonathan G. Hanley Abstract N -ethylmaleimide-sensitive fusion protein (NSF) is essential for numerous Ca2+ -triggered vesicle trafficking events. It functions as a molecular chaperone to regulate trafficking protein complexes such as the soluble NSF attachment protein (SNAP) receptor complex and the ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-protein interacting with C-kinase (PICK1) complex. AMPAR trafficking is fundamental to processes of synaptic plasticity, which may underlie learning and memory. Changes in synaptic strength brought about by AMPAR trafficking are triggered by a post-synaptic influx of Ca2+, which may have numerous molecular targets including PICK1. NSF binds AMPAR subunit glutamate receptor subunit 2 (GluR2) and functions to maintain receptors at the synapse. In this study, it was showed that NSF is a Ca2+ -binding protein and that GluR2,NSF interactions are inhibited by the presence of 15 ,mol/L Ca2+. NSF Ca2+ -binding is reciprocally inhibited by the presence of GluR2 C-terminus. Mutant of NSF that binds Ca2+ with reduced affinity and binds GluR2 with reduced sensitivity to Ca2+ was identied. In addition, the interaction of ,SNAP with PICK1 is sensitive to Ca2+. This study demonstrates that the GluR2-NSF-,SNAP-PICK1 complex is regulated directly by Ca2+, allowing for the transduction of Ca2+ signals into concerted alterations in protein,protein interactions to bring about changes in AMPAR trafficking during synaptic plasticity. [source] Developmental maturation of ionotropic glutamate receptor subunits in rat vestibular nuclear neurons responsive to vertical linear accelerationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008Suk-King Lai Abstract We investigated the maturation profile of subunits of ionotropic glutamate receptors in vestibular nuclear neurons that were activated by sinusoidal linear acceleration along the vertical plane. The otolithic origin of Fos expression in these neurons was confirmed as a marker of functional activation when labyrinthectomized and/or stationary control rats contrasted by showing sporadically scattered Fos-labeled neurons in the vestibular nuclei. By double immunohistochemistry for Fos and one of the receptor subunits, otolith-related neurons that expressed either ,-amino-3-hydroxy-5-methyl-4-isoxazole-propionate or N -methyl- d -aspartate subunits were first identified in the medial vestibular nucleus, spinal vestibular nucleus and Group x by postnatal day (P)7, and in the lateral vestibular nucleus and Group y by P9. No double-labeled neurons were found in the superior vestibular nucleus. Within each vestibular subnucleus, these double-labeled neurons constituted ,90% of the total Fos-labeled neurons. The percentage of Fos-labeled neurons expressing the GluR1 or NR2A subunit showed developmental invariance in all subnuclei. For Fos-labeled neurons expressing the NR1 subunit, similar invariance was observed except that, in Group y, these neurons decreased from P14 onwards. For Fos-labeled neurons expressing the GluR2, GluR2/3, GluR4 or NR2B subunit, a significant decrease was found by the adult stage. In particular, those expressing the GluR4 subunit showed a two- to threefold decrease in the medial vestibular nucleus, spinal vestibular nucleus and Group y. Also, those expressing the NR2B subunit showed a twofold decrease in Group y. Taken together, the postsynaptic expression of ionotropic glutamate receptor subunits in different vestibular subnuclei suggests that glutamatergic transmission within subregions plays differential developmental roles in the coding of gravity-related vertical spatial information. [source] Heterogeneous distribution of AMPA glutamate receptor subunits at the photoreceptor synapses of rodent retinaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2001Iris Hack Abstract In the retina the segregation of different aspects of visual information starts at the first synapse in signal transfer from the photoreceptors to the second-order neurons, via the neurotransmitter glutamate. We examined the distribution of the four AMPA glutamate receptor subunits GluR1,GluR4 at the photoreceptor synapses in mouse and rat retinae by light and immunoelectron microscopy and serial section reconstructions. On the dendrites of OFF-cone bipolar cells, which make flat, noninvaginating contacts postsynaptic at cone synaptic terminals, the subunits GluR1 and GluR2 were predominantly found. Horizontal cell processes postsynaptic at both rod and cone synaptic terminals preferentially expressed the subunits GluR2, GluR2/3 and GluR4. An intriguing finding was the presence of GluR2/3 and GluR4 subunits on dendrites of putative rod bipolar cells, which are thought to signal through the sign-inverting metabotropic glutamate receptor 6, mGluR6. Furthermore, at the rod terminals, horizontal cell processes and rod bipolar cell dendrites showed labelling for the AMPA receptor subunits at the ribbon synaptic site or perisynaptically at their site of invagination into the rod terminal. The wide distribution of AMPA receptor subunits at the photoreceptor synapses suggests that AMPA receptors play an important role in visual signal transfer from the photoreceptors to their postsynaptic partners. [source] Assembly and cell surface expression of KA-2 subunit-containing kainate receptorsJOURNAL OF NEUROCHEMISTRY, Issue 6 2003Ferenc Gallyas Jr Abstract Kainate receptors (KARs) modulate synaptic transmission at both pre-synaptic and post-synaptic sites. The overlap in the distribution of KA-2 and GluR6/7 subunits in several brain regions suggests the co-assembly of these subunits in native KARs. The molecular mechanisms that control the assembly and surface expression of KARs are unknown. Unlike GluR5,7, the KA-2 subunit is unable to form functional homomeric KAR channels. We expressed the KA-2 subunit alone or in combination with other KAR subunits in HEK-293 cells. The cell surface expression of the KAR subunit homo- and heteromers were analysed using biotinylation and agonist-stimulated cobalt uptake. While GluR6 or GluR7 homomers were expressed on the cell surface, KA-2 alone was retained within the endoplasmic reticulum. We found that the cell surface expression of KA-2 was dramatically increased by co-expression with either of the low-affinity KAR subunits GluR5,7. However, co-expression with other related ionotropic glutamate receptor subunits (GluR1 and NR1) does not facilitate the cell surface expression of KA-2. The analysis of subcellular fractions of neocortex revealed that synaptic KARs have a relatively high KA-2 content compared to microsomal ones. Thus, KA-2 is likely to contain an endoplasmic reticulum retention signal that is shielded on assembly with other KAR subunits. [source] Expression of SV2 in the Seveloping Chick Cerebellum: Comparison with Calbindin and AMPA Glutamate Receptors 2/3THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2008Detlev Grabs Abstract The well-organized cerebellum is an ideal model to investigate the developmental appearance and localization of pre- and postsynaptic structures. One of the synaptic proteins abundant in the central nervous system and localized in presynaptic vesicle membranes is the synaptic vesicle protein 2 (SV2). SV2 was shown to be involved in priming and modulating synaptic vesicles and having an effect in epileptic diseases. So far there are no data available describing the developmental localization of this protein in the cerebellum. We followed the expression pattern of SV2 and compared it with the expression of the neuronal calcium-binding protein Calbindin and the AMPA glutamate receptor subunits 2/3 (GluR 2/3), both shown to be early expressed in the developing chick cerebellum predominantly in Purkinje cells. We detected the expression of SV2 in presynaptic terminals (mainly from climbing and mossy fibers) as soon as they are formed at embryonic day 16 in the inner molecular layer. Purkinje cells express Calbindin and GluR 2/3 in the soma and postsynaptically in the primary dendrites at this stage. With ongoing development, the pattern of SV2 expression follows the development of Purkinje cell dendrites in the molecular layer, suggesting a synaptic refinement of labeled climbing and later parallel fibers. Anat Rec, 291:538,546, 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||