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Sample records for psd-95 controls ampa

  1. A critical role for PSD-95/AKAP interactions in endocytosis of synaptic AMPA receptors.

    PubMed

    Bhattacharyya, Samarjit; Biou, Virginie; Xu, Weifeng; Schlüter, Oliver; Malenka, Robert C

    2009-02-01

    The endocytosis of AMPA receptors (AMPARs) underlies several forms of synaptic plasticity, including NMDA receptor (NMDAR)-dependent long-term depression (LTD), but the molecular mechanisms responsible for this trafficking remain unknown. We found that PSD-95, a major postsynaptic density protein, is important for NMDAR-triggered endocytosis of synaptic AMPARs in rat neuron cultures because of its binding to A kinase-anchoring protein 150 (AKAP150), a scaffold for specific protein kinases and phosphatases. Knockdown of PSD-95 with shRNA blocked NMDAR-triggered, but not constitutive or mGluR-triggered, endocytosis of AMPARs. Deletion of PSD-95's Src homology 3 and guanylate kinase-like domains, as well as a point mutation (L460P), both of which inhibit binding of PSD-95 to AKAP150, also blocked NMDAR-triggered AMPAR endocytosis. Furthermore, expression of a mutant AKAP150 that does not bind calcineurin inhibited this NMDAR-triggered trafficking event. Our results suggest that PSD-95's interaction with AKAP150 is critical for NMDAR-triggered AMPAR endocytosis and LTD, possibly because these scaffolds position calcineurin in the appropriate subsynaptic domain.

  2. Palmitoylation regulates glutamate receptor distributions in postsynaptic densities through control of PSD95 conformation and orientation

    PubMed Central

    Jeyifous, Okunola; Lin, Eric I.; Chen, Xiaobing; Antinone, Sarah E.; Mastro, Ryan; Drisdel, Renaldo; Reese, Thomas S.; Green, William N.

    2016-01-01

    Postsynaptic density protein 95 (PSD95) and synapse-associated protein 97 (SAP97) are homologous scaffold proteins with different N-terminal domains, possessing either a palmitoylation site (PSD95) or an L27 domain (SAP97). Here, we measured PSD95 and SAP97 conformation in vitro and in postsynaptic densities (PSDs) using FRET and EM, and examined how conformation regulated interactions with AMPA-type and NMDA-type glutamate receptors (AMPARs/NMDARs). Palmitoylation of PSD95 changed its conformation from a compact to an extended configuration. PSD95 associated with AMPARs (via transmembrane AMPAR regulatory protein subunits) or NMDARs [via glutamate ionotropic receptor NMDA-type subunit 2B (GluN2B) subunits] only in its palmitoylated and extended conformation. In contrast, in its extended conformation, SAP97 associates with NMDARs, but not with AMPARs. Within PSDs, PSD95 and SAP97 were largely in the extended conformation, but had different orientations. PSD95 oriented perpendicular to the PSD membrane, with its palmitoylated, N-terminal domain at the membrane. SAP97 oriented parallel to the PSD membrane, likely as a dimer through interactions of its N-terminal L27 domain. Changing PSD95 palmitoylation in PSDs altered PSD95 and AMPAR levels but did not affect NMDAR levels. These results indicate that in PSDs, PSD95 palmitoylation, conformation, and its interactions are dynamic when associated with AMPARs and more stable when associated with NMDARs. Altogether, our results are consistent with differential regulation of PSD95 palmitoylation in PSDs resulting from the clustering of palmitoylating and depalmitoylating enzymes into AMPAR nanodomains segregated away from NMDAR nanodomains. PMID:27956638

  3. Identification of PSD-95 Depalmitoylating Enzymes

    PubMed Central

    Yokoi, Norihiko; Sekiya, Atsushi; Murakami, Tatsuro; Kobayashi, Kenta

    2016-01-01

    Postsynaptic density (PSD)-95, the most abundant postsynaptic scaffolding protein, plays a pivotal role in synapse development and function. Continuous palmitoylation cycles on PSD-95 are essential for its synaptic clustering and regulation of AMPA receptor function. However, molecular mechanisms for palmitate cycling on PSD-95 remain incompletely understood, as PSD-95 depalmitoylating enzymes remain unknown. Here, we isolated 38 mouse or rat serine hydrolases and found that a subset specifically depalmitoylated PSD-95 in heterologous cells. These enzymes showed distinct substrate specificity. α/β-Hydrolase domain-containing protein 17 members (ABHD17A, 17B, and 17C), showing the strongest depalmitoylating activity to PSD-95, showed different localization from other candidates in rat hippocampal neurons, and were distributed to recycling endosomes, the dendritic plasma membrane, and the synaptic fraction. Expression of ABHD17 in neurons selectively reduced PSD-95 palmitoylation and synaptic clustering of PSD-95 and AMPA receptors. Furthermore, taking advantage of the acyl-PEGyl exchange gel shift (APEGS) method, we quantitatively monitored the palmitoylation stoichiometry and the depalmitoylation kinetics of representative synaptic proteins, PSD-95, GluA1, GluN2A, mGluR5, Gαq, and HRas. Unexpectedly, palmitate on all of them did not turn over in neurons. Uniquely, most of the PSD-95 population underwent rapid palmitoylation cycles, and palmitate cycling on PSD-95 decelerated accompanied by its increased stoichiometry as synapses developed, probably contributing to postsynaptic receptor consolidation. Finally, inhibition of ABHD17 expression dramatically delayed the kinetics of PSD-95 depalmitoylation. This study suggests that local palmitoylation machinery composed of synaptic DHHC palmitoylating enzymes and ABHD17 finely controls the amount of synaptic PSD-95 and synaptic function. SIGNIFICANCE STATEMENT Protein palmitoylation, the most common lipid

  4. PMCA2 VIA PSD-95 CONTROLS CALCIUM SIGNALING BY α7-CONTAINING NICOTINIC ACETYLCHOLINE RECEPTORS ON ASPINY INTERNEURONS

    PubMed Central

    Gomez-Varela, David; Schmidt, Manuela; Schoellerman, Jeff; Peters, Eric C.; Berg, Darwin K.

    2012-01-01

    Local control of calcium concentration within neurons is critical for signaling and regulation of synaptic communication in neural circuits. How local control can be achieved in the absence of physical compartmentalization is poorly understood. Challenging examples are provided by nicotinic acetylcholine receptors that contain α7 nicotinic receptor subunits (α7-nAChRs). These receptors are highly permeable to calcium and are concentrated on aspiny dendrites of interneurons which lack obvious physical compartments for constraining calcium diffusion. Using functional proteomics on rat brain, we show that α7-nAChRs are associated with the membrane calcium pump PMCA2. Analysis of α7-nAChR function in hippocampal interneurons in culture shows that PMCA2 activity limits the duration of calcium elevations produced by the receptors. Unexpectedly, PMCA2 inhibition triggers rapid calcium-dependent loss of α7-nAChR clusters. This extreme regulatory response is mediated by CaMKII, involves proteasome activity, depends on the second intracellular loop of α7-nAChR subunits, and is specific in that it does not alter two other classes of calcium-permeable ionotropic receptors on the same neurons. A critical link is provided by the scaffold protein PSD-95, which is associated with α7-nAChRs and constrains their mobility as revealed by single-particle tracking on neurons. The PSD-95 link is required for PMCA2-mediated removal of α7-nAChR clusters. This three-component combination of PMCA2/PSD-95/α7-nAChR offers a novel mechanism for tight control of calcium dynamics in neurons. PMID:22593058

  5. Cdk5 regulates PSD-95 ubiquitination in neurons

    PubMed Central

    Bianchetta, Michael J.; Lam, TuKiet T.; Jones, Stephen N.; Morabito, Maria A.

    2011-01-01

    The kinase Cdk5 and its activator p35 have been implicated in drug addiction, neurodegenerative diseases such as Alzheimer’s, learning and memory, and synapse maturation and plasticity. However the molecular mechanisms by which Cdk5 regulates synaptic plasticity are still unclear. PSD-95 is a major postsynaptic scaffolding protein of glutamatergic synapses that regulates synaptic strength and plasticity. PSD-95 is ubiquitinated by the Ubiquitin E3 Ligase Mdm2, and rapid and transient PSD-95 ubiquitination has been implicated in NMDA receptor-induced AMPA receptor endocytosis. Here we demonstrate that genetic or pharmacological reduction of Cdk5 activity increases the interaction of Mdm2 with PSD-95 and enhances PSD-95 ubiquitination without affecting PSD-95 protein levels in vivo in mice, suggesting a non-proteolytic function of ubiquitinated PSD-95 at synapses. We show that PSD-95 ubiquitination correlates with increased interaction with β-adaptin, a subunit of the clathrin adaptor protein complex AP-2. This interaction is increased by genetic reduction of Cdk5 activity or NMDA receptor stimulation and is dependent on Mdm2. Together these results support a function for Cdk5 in regulating PSD-95 ubiqutination and its interaction with AP-2 and suggest a mechanism by which PSD-95 may regulate NMDA receptor-induced AMPA receptor endocytosis. PMID:21849563

  6. Capping of the N-terminus of PSD-95 by calmodulin triggers its postsynaptic release.

    PubMed

    Zhang, Yonghong; Matt, Lucas; Patriarchi, Tommaso; Malik, Zulfiqar A; Chowdhury, Dhrubajyoti; Park, Deborah K; Renieri, Alessandra; Ames, James B; Hell, Johannes W

    2014-06-17

    Postsynaptic density protein-95 (PSD-95) is a central element of the postsynaptic architecture of glutamatergic synapses. PSD-95 mediates postsynaptic localization of AMPA receptors and NMDA receptors and plays an important role in synaptic plasticity. PSD-95 is released from postsynaptic membranes in response to Ca(2+) influx via NMDA receptors. Here, we show that Ca(2+)/calmodulin (CaM) binds at the N-terminus of PSD-95. Our NMR structure reveals that both lobes of CaM collapse onto a helical structure of PSD-95 formed at its N-terminus (residues 1-16). This N-terminal capping of PSD-95 by CaM blocks palmitoylation of C3 and C5, which is required for postsynaptic PSD-95 targeting and the binding of CDKL5, a kinase important for synapse stability. CaM forms extensive hydrophobic contacts with Y12 of PSD-95. The PSD-95 mutant Y12E strongly impairs binding to CaM and Ca(2+)-induced release of PSD-95 from the postsynaptic membrane in dendritic spines. Our data indicate that CaM binding to PSD-95 serves to block palmitoylation of PSD-95, which in turn promotes Ca(2+)-induced dissociation of PSD-95 from the postsynaptic membrane.

  7. Activity-dependent regulation of synaptic strength by PSD-95 in CA1 neurons

    PubMed Central

    Zhang, Peng

    2012-01-01

    CaMKII and PSD-95 are the two most abundant postsynaptic proteins in the postsynaptic density (PSD). Overexpression of either can dramatically increase synaptic strength and saturate long-term potentiation (LTP). To do so, CaMKII must be activated, but the same is not true for PSD-95; expressing wild-type PSD-95 is sufficient. This raises the question of whether PSD-95's effects are simply an equilibrium process [increasing the number of AMPA receptor (AMPAR) slots] or whether activity is somehow involved. To examine this question, we blocked activity in cultured hippocampal slices with TTX and found that the effects of PSD-95 overexpression were greatly reduced. We next studied the type of receptors involved. The effects of PSD-95 were prevented by antagonists of group I metabotropic glutamate receptors (mGluRs) but not by antagonists of ionotropic glutamate receptors. The inhibition of PSD-95-induced strengthening was not simply a result of inhibition of PSD-95 synthesis. To understand the mechanisms involved, we tested the role of CaMKII. Overexpression of a CaMKII inhibitor, CN19, greatly reduced the effect of PSD-95. We conclude that PSD-95 cannot itself increase synaptic strength simply by increasing the number of AMPAR slots; rather, PSD-95's effects on synaptic strength require an activity-dependent process involving mGluR and CaMKII. PMID:22114157

  8. Durable fear memories require PSD-95

    PubMed Central

    Fitzgerald, Paul J.; Pinard, Courtney R.; Camp, Marguerite C.; Feyder, Michael; Sah, Anupam; Bergstrom, Hadley; Graybeal, Carolyn; Liu, Yan; Schlüter, Oliver; Grant, Seth G.N.; Singewald, Nicolas; Xu, Weifeng; Holmes, Andrew

    2014-01-01

    Traumatic fear memories are highly durable but also dynamic, undergoing repeated reactivation and rehearsal over time. While overly persistent fear memories underlie anxiety disorders such as posttraumatic stress disorder, the key neural and molecular mechanisms underlying fear memory durability remain unclear. Post-synaptic density 95 (PSD-95) is a synaptic protein regulating glutamate receptor anchoring, synaptic stability and certain types of memory. Employing a loss-of-function mutant mouse lacking the guanylate kinase domain of PSD-95 (PSD-95GK), we analyzed the contribution of PSD-95 to fear memory formation and retrieval, and sought to identify the neural basis of PSD-95-mediated memory maintenance using ex vivo immediate-early gene mapping, in vivo neuronal recordings and viral-mediated knockdown approaches. We show that PSD-95 is dispensable for the formation and expression of recent fear memories, but essential for the formation of precise and flexible fear memories and for the maintenance of memories at remote time points. The failure of PSD-95GK mice to retrieve remote cued fear memories was associated with hypoactivation of the infralimbic cortex (IL) (not anterior cingulate (ACC) or prelimbic cortex), reduced IL single-unit firing and bursting, and attenuated IL gamma and theta oscillations. Adeno-associated PSD-95 virus-mediated knockdown in the IL, not ACC, was sufficient to impair recent fear extinction and remote fear memory, and remodel IL dendritic spines. Collectively, these data identify PSD-95 in the IL as a critical mechanism supporting the durability of fear memories over time. These preclinical findings have implications for developing novel approaches to treating trauma-based anxiety disorders that target the weakening of overly persistent fear memories. PMID:25510511

  9. Durable fear memories require PSD-95.

    PubMed

    Fitzgerald, P J; Pinard, C R; Camp, M C; Feyder, M; Sah, A; Bergstrom, H C; Graybeal, C; Liu, Y; Schlüter, O M; Grant, S G; Singewald, N; Xu, W; Holmes, A

    2015-07-01

    Traumatic fear memories are highly durable but also dynamic, undergoing repeated reactivation and rehearsal over time. Although overly persistent fear memories underlie anxiety disorders, such as posttraumatic stress disorder, the key neural and molecular mechanisms underlying fear memory durability remain unclear. Postsynaptic density 95 (PSD-95) is a synaptic protein regulating glutamate receptor anchoring, synaptic stability and certain types of memory. Using a loss-of-function mutant mouse lacking the guanylate kinase domain of PSD-95 (PSD-95(GK)), we analyzed the contribution of PSD-95 to fear memory formation and retrieval, and sought to identify the neural basis of PSD-95-mediated memory maintenance using ex vivo immediate-early gene mapping, in vivo neuronal recordings and viral-mediated knockdown (KD) approaches. We show that PSD-95 is dispensable for the formation and expression of recent fear memories, but essential for the formation of precise and flexible fear memories and for the maintenance of memories at remote time points. The failure of PSD-95(GK) mice to retrieve remote cued fear memory was associated with hypoactivation of the infralimbic (IL) cortex (but not the anterior cingulate cortex (ACC) or prelimbic cortex), reduced IL single-unit firing and bursting, and attenuated IL gamma and theta oscillations. Adeno-associated virus-mediated PSD-95 KD in the IL, but not the ACC, was sufficient to impair recent fear extinction and remote fear memory, and remodel IL dendritic spines. Collectively, these data identify PSD-95 in the IL as a critical mechanism supporting the durability of fear memories over time. These preclinical findings have implications for developing novel approaches to treating trauma-based anxiety disorders that target the weakening of overly persistent fear memories.

  10. Hypersocial behavior and biological redundancy in mice with reduced expression of PSD95 or PSD93.

    PubMed

    Winkler, Daniela; Daher, Fernanda; Wüstefeld, Liane; Hammerschmidt, Kurt; Poggi, Giulia; Seelbach, Anna; Krueger-Burg, Dilja; Vafadari, Behnam; Ronnenberg, Anja; Liu, Yanling; Kaczmarek, Leszek; Schlüter, Oliver M; Ehrenreich, Hannelore; Dere, Ekrem

    2017-02-09

    increased PSD93 protein expression in hippocampal synaptic enrichment preparations of PSD95(+/-) mice. These data suggest that both PSD95 and PSD93 are involved in processing of social stimuli and control of social behavior. This important role may be partly assured by functional/behavioral and biological/biochemical redundancy.

  11. Early Growth Response 1 (Egr-1) Regulates N-Methyl-d-aspartate Receptor (NMDAR)-dependent Transcription of PSD-95 and α-Amino-3-hydroxy-5-methyl-4-isoxazole Propionic Acid Receptor (AMPAR) Trafficking in Hippocampal Primary Neurons*

    PubMed Central

    Qin, Xike; Jiang, Yongjun; Tse, Yiu Chung; Wang, Yunling; Wong, Tak Pan; Paudel, Hemant K.

    2015-01-01

    The N-methyl-d-aspartate receptor (NMDAR) controls synaptic plasticity and memory function and is one of the major inducers of transcription factor Egr-1 in the hippocampus. However, how Egr-1 mediates the NMDAR signal in neurons has remained unclear. Here, we show that the hippocampus of mice lacking Egr-1 displays electrophysiology properties and ultrastructure that are similar to mice overexpressing PSD-95, a major scaffolding protein of postsynaptic density involved in synapse formation, synaptic plasticity, and synaptic targeting of AMPA receptors (AMPARs), which mediate the vast majority of excitatory transmission in the CNS. We demonstrate that Egr-1 is a transcription repressor of the PSD-95 gene and is recruited to the PSD-95 promoter in response to NMDAR activation. Knockdown of Egr-1 in rat hippocampal primary neurons blocks NMDAR-induced PSD-95 down-regulation and AMPAR endocytosis. Likewise, overexpression of Egr-1 in rat hippocampal primary neurons causes reduction in PSD-95 protein level and promotes AMPAR endocytosis. Our data indicate that Egr-1 is involved in NMDAR-mediated PSD-95 down-regulation and AMPAR endocytosis, a process important in the expression of long term depression. PMID:26475861

  12. A novel role for PSD-95 in mediating ethanol intoxication, drinking and place preference.

    PubMed

    Camp, Marguerite C; Feyder, Michael; Ihne, Jessica; Palachick, Benjamin; Hurd, Benita; Karlsson, Rose-Marie; Noronha, Bianca; Chen, Yi-Chyan; Coba, Marcelo P; Grant, Seth G N; Holmes, Andrew

    2011-07-01

    The synaptic signaling mechanisms mediating the behavioral effects of ethanol (EtOH) remain poorly understood. Post-synaptic density 95 (PSD-95, SAP-90, Dlg4) is a key orchestrator of N-methyl-D-aspartate receptors (NMDAR) and glutamatergic synapses, which are known to be major sites of EtOH's behavioral actions. However, the potential contribution of PSD-95 to EtOH-related behaviors has not been established. Here, we evaluated knockout (KO) mice lacking PSD-95 for multiple measures of sensitivity to the acute intoxicating effects of EtOH (ataxia, hypothermia, sedation/hypnosis), EtOH drinking under conditions of free access and following deprivation, acquisition and long-term retention of EtOH conditioned place preference (CPP) (and lithium chloride-induced conditioned taste aversion), and intoxication-potentiating responses to NMDAR antagonism. PSD-95 KO exhibited increased sensitivity to the sedative/hypnotic, but not ataxic or hypothermic, effects of acute EtOH relative to wild-type controls (WT). PSD-95 KO consumed less EtOH than WT, particularly at higher EtOH concentrations, although increases in KO drinking could be induced by concentration-fading and deprivation. PSD-95 KO showed normal EtOH CPP 1 day after conditioning, but showed significant aversion 2 weeks later. Lithium chloride-induced taste aversion was impaired in PSD-95 KO at both time points. Finally, the EtOH-potentiating effects of the NMDAR antagonist MK-801 were intact in PSD-95 KO at the dose tested. These data reveal a major, novel role for PSD-95 in mediating EtOH behaviors, and add to growing evidence that PSD-95 is a key mediator of the effects of multiple abused drugs.

  13. Ocular Dominance Plasticity after Stroke Was Preserved in PSD-95 Knockout Mice.

    PubMed

    Greifzu, Franziska; Parthier, Daniel; Goetze, Bianka; Schlüter, Oliver M; Löwel, Siegrid

    2016-01-01

    Neuronal plasticity is essential to enable rehabilitation when the brain suffers from injury, such as following a stroke. One of the most established models to study cortical plasticity is ocular dominance (OD) plasticity in the primary visual cortex (V1) of the mammalian brain induced by monocular deprivation (MD). We have previously shown that OD-plasticity in adult mouse V1 is absent after a photothrombotic (PT) stroke lesion in the adjacent primary somatosensory cortex (S1). Exposing lesioned mice to conditions which reduce the inhibitory tone in V1, such as raising animals in an enriched environment or short-term dark exposure, preserved OD-plasticity after an S1-lesion. Here we tested whether modification of excitatory circuits can also be beneficial for preserving V1-plasticity after stroke. Mice lacking postsynaptic density protein-95 (PSD-95), a signaling scaffold present at mature excitatory synapses, have lifelong juvenile-like OD-plasticity caused by an increased number of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) -silent synapses in V1 but unaltered inhibitory tone. In fact, using intrinsic signal optical imaging, we show here that OD-plasticity was preserved in V1 of adult PSD-95 KO mice after an S1-lesion but not in PSD-95 wildtype (WT)-mice. In addition, experience-enabled enhancement of the optomotor reflex of the open eye after MD was compromised in both lesioned PSD-95 KO and PSD-95 WT mice. Basic V1-activation and retinotopic map quality were, however, not different between lesioned PSD-95 KO mice and their WT littermates. The preserved OD-plasticity in the PSD-95 KO mice indicates that V1-plasticity after a distant stroke can be promoted by either changes in excitatory circuitry or by lowering the inhibitory tone in V1 as previously shown. Furthermore, the present data indicate that an increased number of AMPA-silent synapses preserves OD-plasticity not only in the healthy brain, but also in another experimental paradigm of

  14. Ocular Dominance Plasticity after Stroke Was Preserved in PSD-95 Knockout Mice

    PubMed Central

    Greifzu, Franziska; Parthier, Daniel; Goetze, Bianka; Schlüter, Oliver M.; Löwel, Siegrid

    2016-01-01

    Neuronal plasticity is essential to enable rehabilitation when the brain suffers from injury, such as following a stroke. One of the most established models to study cortical plasticity is ocular dominance (OD) plasticity in the primary visual cortex (V1) of the mammalian brain induced by monocular deprivation (MD). We have previously shown that OD-plasticity in adult mouse V1 is absent after a photothrombotic (PT) stroke lesion in the adjacent primary somatosensory cortex (S1). Exposing lesioned mice to conditions which reduce the inhibitory tone in V1, such as raising animals in an enriched environment or short-term dark exposure, preserved OD-plasticity after an S1-lesion. Here we tested whether modification of excitatory circuits can also be beneficial for preserving V1-plasticity after stroke. Mice lacking postsynaptic density protein-95 (PSD-95), a signaling scaffold present at mature excitatory synapses, have lifelong juvenile-like OD-plasticity caused by an increased number of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) -silent synapses in V1 but unaltered inhibitory tone. In fact, using intrinsic signal optical imaging, we show here that OD-plasticity was preserved in V1 of adult PSD-95 KO mice after an S1-lesion but not in PSD-95 wildtype (WT)-mice. In addition, experience-enabled enhancement of the optomotor reflex of the open eye after MD was compromised in both lesioned PSD-95 KO and PSD-95 WT mice. Basic V1-activation and retinotopic map quality were, however, not different between lesioned PSD-95 KO mice and their WT littermates. The preserved OD-plasticity in the PSD-95 KO mice indicates that V1-plasticity after a distant stroke can be promoted by either changes in excitatory circuitry or by lowering the inhibitory tone in V1 as previously shown. Furthermore, the present data indicate that an increased number of AMPA-silent synapses preserves OD-plasticity not only in the healthy brain, but also in another experimental paradigm of

  15. Posttranslational Modifications Regulate the Postsynaptic Localization of PSD-95.

    PubMed

    Vallejo, Daniela; Codocedo, Juan F; Inestrosa, Nibaldo C

    2017-04-01

    The postsynaptic density (PSD) consists of a lattice-like array of interacting proteins that organizes and stabilizes synaptic receptors, ion channels, structural proteins, and signaling molecules required for normal synaptic transmission and synaptic function. The scaffolding and hub protein postsynaptic density protein-95 (PSD-95) is a major element of central chemical synapses and interacts with glutamate receptors, cell adhesion molecules, and cytoskeletal elements. In fact, PSD-95 can regulate basal synaptic stability as well as the activity-dependent structural plasticity of the PSD and, therefore, of the excitatory chemical synapse. Several studies have shown that PSD-95 is highly enriched at excitatory synapses and have identified multiple protein structural domains and protein-protein interactions that mediate PSD-95 function and trafficking to the postsynaptic region. PSD-95 is also a target of several signaling pathways that induce posttranslational modifications, including palmitoylation, phosphorylation, ubiquitination, nitrosylation, and neddylation; these modifications determine the synaptic stability and function of PSD-95 and thus regulate the fates of individual dendritic spines in the nervous system. In the present work, we review the posttranslational modifications that regulate the synaptic localization of PSD-95 and describe their functional consequences. We also explore the signaling pathways that induce such changes.

  16. The LGI1-ADAM22 protein complex directs synapse maturation through regulation of PSD-95 function.

    PubMed

    Lovero, Kathryn L; Fukata, Yuko; Granger, Adam J; Fukata, Masaki; Nicoll, Roger A

    2015-07-28

    Synapse development is coordinated by a number of transmembrane and secreted proteins that come together to form synaptic organizing complexes. Whereas a variety of synaptogenic proteins have been characterized, much less is understood about the molecular networks that support the maintenance and functional maturation of nascent synapses. Here, we demonstrate that leucine-rich, glioma-inactivated protein 1 (LGI1), a secreted protein previously shown to modulate synaptic AMPA receptors, is a paracrine signal released from pre- and postsynaptic neurons that acts specifically through a disintegrin and metalloproteinase protein 22 (ADAM22) to set postsynaptic strength. We go on to describe a novel role for ADAM22 in maintaining excitatory synapses through PSD-95/Dlg1/zo-1 (PDZ) domain interactions. Finally, we show that in the absence of LGI1, the mature synapse scaffolding protein PSD-95, but not the immature synapse scaffolding protein SAP102, is unable to modulate synaptic transmission. These results indicate that LGI1 and ADAM22 form an essential synaptic organizing complex that coordinates the maturation of excitatory synapses by regulating the functional incorporation of PSD-95.

  17. PSD-95 promotes the stabilization of young synaptic contacts.

    PubMed

    Taft, Christine E; Turrigiano, Gina G

    2014-01-05

    Maintaining a population of stable synaptic connections is probably of critical importance for the preservation of memories and functional circuitry, but the molecular dynamics that underlie synapse stabilization is poorly understood. Here, we use simultaneous time-lapse imaging of post synaptic density-95 (PSD-95) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) to investigate the dynamics of protein composition at axodendritic (AD) contacts. Our data reveal that this composition is highly dynamic, with both proteins moving into and out of the same synapse independently, so that synapses cycle rapidly between states in which they are enriched for none, one or both proteins. We assessed how PSD-95 and CaMKII interact at stable and transient AD sites and found that both phospho-CaMKII and PSD-95 are present more often at stable than labile contacts. Finally, we found that synaptic contacts are more stable in older neurons, and this process can be mimicked in younger neurons by overexpression of PSD-95. Taken together, these data show that synaptic protein composition is highly variable over a time-scale of hours, and that PSD-95 is probably a key synaptic protein that promotes synapse stability.

  18. Reduced SNAP-25 increases PSD-95 mobility and impairs spine morphogenesis

    PubMed Central

    Fossati, G; Morini, R; Corradini, I; Antonucci, F; Trepte, P; Edry, E; Sharma, V; Papale, A; Pozzi, D; Defilippi, P; Meier, J C; Brambilla, R; Turco, E; Rosenblum, K; Wanker, E E; Ziv, N E; Menna, E; Matteoli, M

    2015-01-01

    Impairment of synaptic function can lead to neuropsychiatric disorders collectively referred to as synaptopathies. The SNARE protein SNAP-25 is implicated in several brain pathologies and, indeed, brain areas of psychiatric patients often display reduced SNAP-25 expression. It has been recently found that acute downregulation of SNAP-25 in brain slices impairs long-term potentiation; however, the processes through which this occurs are still poorly defined. We show that in vivo acute downregulation of SNAP-25 in CA1 hippocampal region affects spine number. Consistently, hippocampal neurons from SNAP-25 heterozygous mice show reduced densities of dendritic spines and defective PSD-95 dynamics. Finally, we show that, in brain, SNAP-25 is part of a molecular complex including PSD-95 and p140Cap, with p140Cap being capable to bind to both SNAP-25 and PSD-95. These data demonstrate an unexpected role of SNAP-25 in controlling PSD-95 clustering and open the possibility that genetic reductions of the protein levels – as occurring in schizophrenia – may contribute to the pathology through an effect on postsynaptic function and plasticity. PMID:25678324

  19. A cyclic peptide targeted against PSD-95 blocks central sensitization and attenuates thermal hyperalgesia.

    PubMed

    LeBlanc, B W; Iwata, M; Mallon, A P; Rupasinghe, C N; Goebel, D J; Marshall, J; Spaller, M R; Saab, C Y

    2010-05-05

    Post-synaptic density protein PSD-95 is emerging as a valid target for modulating nociception in animal studies. Based on the key role of PSD-95 in neuronal plasticity and the maintenance of pain behavior, we predicted that CN2097, a peptide-based macrocycle of nine residues that binds to the PSD-95 Discs large, Zona occludens 1 (PDZ) domains of PSD-95, would interfere with physiologic phenomena in the spinal cord related to central sensitization. Furthermore, we tested whether spinal intrathecal injection of CN2097 attenuates thermal hyperalgesia in a rat model of sciatic neuropathy. Results demonstrate that spinal CN2097 reverses hyperexcitability of wide dynamic range (WDR) neurons in the dorsal horn of neuropathic rats and decreases their evoked responses to peripheral stimuli (brush, low caliber von Frey and pressure), whereas CN5125 ("negative control") has no effect. CN2097 also blocks C-fiber long-term potentiation (LTP) in the dorsal horn, which is linked to neuronal plasticity and central sensitization. At a molecular level, CN2097 attenuates the increase in phosphorylated p38 MAPK, a key intracellular signaling pathway in neuropathic pain. Moreover, spinal injection of CN2097 blocks thermal hyperalgesia in neuropathic rats. We conclude that CN2097 is a small molecule peptide with putative anti-nociceptive effects that modulates physiologic phenomena related to central sensitization under conditions of chronic pain.

  20. Single-Molecule Imaging of PSD-95 mRNA Translation in Dendrites and Its Dysregulation in a Mouse Model of Fragile X Syndrome.

    PubMed

    Ifrim, Marius F; Williams, Kathryn R; Bassell, Gary J

    2015-05-06

    Fragile X syndrome (FXS) is caused by the loss of the fragile X mental retardation protein (FMRP), an RNA binding protein that regulates translation of numerous target mRNAs, some of which are dendritically localized. Our previous biochemical studies using synaptoneurosomes demonstrate a role for FMRP and miR-125a in regulating the translation of PSD-95 mRNA. However, the local translation of PSD-95 mRNA within dendrites and spines, as well as the roles of FMRP or miR-125a, have not been directly studied. Herein, local synthesis of a Venus-PSD-95 fusion protein was directly visualized in dendrites and spines using single-molecule imaging of a diffusion-restricted Venus-PSD-95 reporter under control of the PSD-95 3'UTR. The basal translation rates of Venus-PSD-95 mRNA was increased in cultured hippocampal neurons from Fmr1 KO mice compared with WT neurons, which correlated with a transient elevation of endogenous PSD-95 within dendrites. Following mGluR stimulation with (S)-3,5-dihydroxyphenylglycine, the rate of Venus-PSD-95 mRNA translation increased rapidly in dendrites of WT hippocampal neurons, but not in those of Fmr1 KO neurons or when the binding site of miR125a, previously shown to bind PSD-95 3'UTR, was mutated. This study provides direct support for the hypothesis that local translation within dendrites and spines is dysregulated in FXS. Impairments in the regulated local synthesis of PSD-95, a critical regulator of synaptic structure and function, may affect the spatiotemporal control of PSD-95 levels and affect dendritic spine development and synaptic plasticity in FXS.

  1. Synaptic Clustering of PSD-95 Is Regulated by c-Abl through Tyrosine Phosphorylation

    PubMed Central

    de Arce, Karen Perez; Varela-Nallar, Lorena; Farias, Olivia; Cifuentes, Alejandra; Bull, Paulina; Couch, Brian A.; Koleske, Anthony J.; Inestrosa, Nibaldo C.; Alvarez, Alejandra R.

    2010-01-01

    The c-Abl tyrosine kinase is present in mouse brain synapses, but its precise synaptic function is unknown. We found that c-Abl levels in the rat hippocampus increase postnatally, with expression peaking at the first postnatal week. In 14 d in vitro hippocampal neuron cultures, c-Abl localizes primarily to the postsynaptic compartment, in which it colocalizes with the postsynaptic scaffold protein postsynaptic density protein-95 (PSD-95) in apposition to presynaptic markers. c-Abl associates with PSD-95, and chemical or genetic inhibition of c-Abl kinase activity reduces PSD-95 tyrosine phosphorylation, leading to reduced PSD-95 clustering and reduced synapses in treated neurons. c-Abl can phosphorylate PSD-95 on tyrosine 533, and mutation of this residue reduces the ability of PSD-95 to cluster at postsynaptic sites. Our results indicate that c-Abl regulates synapse formation by mediating tyrosine phosphorylation and clustering of PSD-95. PMID:20220006

  2. Loss of PSD-95 Enrichment is not a Prerequisite for Spine Retraction

    PubMed Central

    Woods, Georgia F.; Oh, Won Chan; Boudewyn, Lauren C.; Mikula, Sarah K.; Zito, Karen

    2011-01-01

    Changes in neuronal structure are thought to underlie long-term behavioral modifications associated with learning and memory. In particular, considerable evidence implicates the destabilization and retraction of dendritic spines along with the loss of spine synapses as an important cellular mechanism for refining brain circuits, yet the molecular mechanisms regulating spine elimination remain ill-defined. The postsynaptic density protein, PSD-95, is highly enriched in dendritic spines and has been associated with spine stability. Because spines with low levels of PSD-95 are more dynamic, and the recruitment of PSD-95 to nascent spines has been associated with spine stabilization, we hypothesized that loss of PSD-95 enrichment would be a prerequisite for spine retraction. To test this hypothesis, we used dual-color time-lapse two-photon microscopy to monitor rat hippocampal pyramidal neurons co-transfected with PSD-95-GFP and DsRed-Express, and we analyzed the relationship between PSD-95-GFP enrichment and spine morphological changes. Consistent with our hypothesis, we found that the majority of spines that retracted were relatively unenriched for PSD-95-GFP. However, in the subset of PSD-95-GFP-enriched spines that retracted, spine shrinkage and loss of PSD-95-GFP were tightly coupled, suggesting that loss of PSD-95-GFP enrichment did not precede spine retraction. Moreover, we found that in some instances spine retraction resulted in a significant enrichment of PSD-95-GFP on the dendritic shaft. Our data support a model of spine retraction in which loss of PSD-95 enrichment is not required prior to the destabilization of spines. PMID:21865455

  3. PSD-95 stabilizes NMDA receptors by inducing the degradation of STEP61

    PubMed Central

    Won, Sehoon; Incontro, Salvatore; Nicoll, Roger A.; Roche, Katherine W.

    2016-01-01

    Phosphorylation regulates surface and synaptic expression of NMDA receptors (NMDARs). Both the tyrosine kinase Fyn and the tyrosine phosphatase striatal-enriched protein tyrosine phosphatase (STEP) are known to target the NMDA receptor subunit GluN2B on tyrosine 1472, which is a critical residue that mediates NMDAR endocytosis. STEP reduces the surface expression of NMDARs by promoting dephosphorylation of GluN2B Y1472, whereas the synaptic scaffolding protein postsynaptic density protein 95 (PSD-95) stabilizes the surface expression of NMDARs. However, nothing is known about a potential functional interaction between STEP and PSD-95. We now report that STEP61 binds to PSD-95 but not to other PSD-95 family members. We find that PSD-95 expression destabilizes STEP61 via ubiquitination and degradation by the proteasome. Using subcellular fractionation, we detect low amounts of STEP61 in the PSD fraction. However, STEP61 expression in the PSD is increased upon knockdown of PSD-95 or in vivo as detected in PSD-95–KO mice, demonstrating that PSD-95 excludes STEP61 from the PSD. Importantly, only extrasynaptic NMDAR expression and currents were increased upon STEP knockdown, as is consistent with low STEP61 localization in the PSD. Our findings support a dual role for PSD-95 in stabilizing synaptic NMDARs by binding directly to GluN2B but also by promoting synaptic exclusion and degradation of the negative regulator STEP61. PMID:27457929

  4. PSD-95 mediates membrane clustering of the human plasma membrane Ca2+ pump isoform 4b.

    PubMed

    Padányi, Rita; Pászty, Katalin; Strehler, Emanuel E; Enyedi, Agnes

    2009-06-01

    Besides the control of global calcium changes, specific plasma membrane calcium ATPase (PMCA) isoforms are involved in the regulation of local calcium signals. Although local calcium signaling requires the confinement of signaling molecules into microdomains, little is known about the specific organization of PMCA molecules within the plasma membrane. Here we show that co-expression with the postsynaptic density-95 (PSD-95) scaffolding protein increased the plasma membrane expression of PMCA4b and redistributed the pump into clusters. The clustering of PMCA4b was fully dependent on the presence of its PDZ-binding sequence. Using the fluorescence recovery after photobleaching (FRAP) technique, we show that the lateral membrane mobility of the clustered PMCA4b is significantly lower than that of the non-clustered molecules. Disruption of the actin-based cytoskeleton by cytochalasin D resulted in increased cluster size. Our results suggest that PSD-95 promotes the formation of high-density PMCA4b microdomains in the plasma membrane and that the membrane cytoskeleton plays an important role in the regulation of this process.

  5. Live Imaging of Endogenous PSD-95 Using ENABLED: A Conditional Strategy to Fluorescently Label Endogenous Proteins

    PubMed Central

    Fortin, Dale A.; Tillo, Shane E.; Yang, Guang; Rah, Jong-Cheol; Melander, Joshua B.; Bai, Suxia; Soler-Cedeño, Omar; Qin, Maozhen; Zemelman, Boris V.; Guo, Caiying

    2014-01-01

    Stoichiometric labeling of endogenous synaptic proteins for high-contrast live-cell imaging in brain tissue remains challenging. Here, we describe a conditional mouse genetic strategy termed endogenous labeling via exon duplication (ENABLED), which can be used to fluorescently label endogenous proteins with near ideal properties in all neurons, a sparse subset of neurons, or specific neuronal subtypes. We used this method to label the postsynaptic density protein PSD-95 with mVenus without overexpression side effects. We demonstrated that mVenus-tagged PSD-95 is functionally equivalent to wild-type PSD-95 and that PSD-95 is present in nearly all dendritic spines in CA1 neurons. Within spines, while PSD-95 exhibited low mobility under basal conditions, its levels could be regulated by chronic changes in neuronal activity. Notably, labeled PSD-95 also allowed us to visualize and unambiguously examine otherwise-unidentifiable excitatory shaft synapses in aspiny neurons, such as parvalbumin-positive interneurons and dopaminergic neurons. Our results demonstrate that the ENABLED strategy provides a valuable new approach to study the dynamics of endogenous synaptic proteins in vivo. PMID:25505322

  6. Wnt-5a/JNK Signaling Promotes the Clustering of PSD-95 in Hippocampal Neurons*

    PubMed Central

    Farías, Ginny G.; Alfaro, Iván E.; Cerpa, Waldo; Grabowski, Catalina P.; Godoy, Juan A.; Bonansco, Christian; Inestrosa, Nibaldo C.

    2009-01-01

    During the formation of synapses, specific regions of pre- and postsynaptic cells associate to form a single functional transmission unit. In this process, synaptogenic factors are necessary to modulate pre- and postsynaptic differentiation. In mammals, different Wnt ligands operate through canonical and non-canonical Wnt pathways, and their precise functions to coordinate synapse structure and function in the mature central nervous system are still largely unknown. Here, we studied the effect of different Wnt ligands on postsynaptic organization. We found that Wnt-5a induces short term changes in the clustering of PSD-95, without affecting its total levels. Wnt-5a promotes the recruitment of PSD-95 from a diffuse dendritic cytoplasmic pool to form new PSD-95 clusters in dendritic spines. Moreover, Wnt-5a acting as a non-canonical ligand regulates PSD-95 distribution through a JNK-dependent signaling pathway, as demonstrated by using the TAT-TI-JIP peptide in mature hippocampal neurons. Finally, using adult rat hippocampal slices, we found that Wnt-5a modulates glutamatergic synaptic transmission through a postsynaptic mechanism. Our studies indicate that the Wnt-5a/JNK pathway modulates the postsynaptic region of mammalian synapse directing the clustering and distribution of the physiologically relevant scaffold protein, PSD-95. PMID:19332546

  7. Clustering of neuronal potassium channels is independent of their interaction with PSD-95

    PubMed Central

    Rasband, Matthew N.; Park, Eunice W.; Zhen, Dongkai; Arbuckle, Margaret I.; Poliak, Sebastian; Peles, Elior; Grant, Seth G.N.; Trimmer, James S.

    2002-01-01

    Voltage-dependent potassium channels regulate membrane excitability and cell–cell communication in the mammalian nervous system, and are found highly localized at distinct neuronal subcellular sites. Kv1 (mammalian Shaker family) potassium channels and the neurexin Caspr2, both of which contain COOH-terminal PDZ domain binding peptide motifs, are found colocalized at high density at juxtaparanodes flanking nodes of Ranvier of myelinated axons. The PDZ domain–containing protein PSD-95, which clusters Kv1 potassium channels in heterologous cells, has been proposed to play a major role in potassium channel clustering in mammalian neurons. Here, we show that PSD-95 colocalizes precisely with Kv1 potassium channels and Caspr2 at juxtaparanodes, and that a macromolecular complex of Kv1 channels and PSD-95 can be immunopurified from mammalian brain and spinal cord. Surprisingly, we find that the high density clustering of Kv1 channels and Caspr2 at juxtaparanodes is normal in a mutant mouse lacking juxtaparanodal PSD-95, and that the indirect interaction between Kv1 channels and Caspr2 is maintained in these mutant mice. These data suggest that the primary function of PSD-95 at juxtaparanodes lies outside of its accepted role in mediating the high density clustering of Kv1 potassium channels at these sites. PMID:12438413

  8. Small molecule inhibitors of PSD95-nNOS protein-protein interactions as novel analgesics

    PubMed Central

    Lee, Wan-Hung; Xu, Zhili; Ashpole, Nicole M.; Hudmon, Andy; Kulkarni, Pushkar M.; Thakur, Ganesh A.; Lai, Yvonne Y.; Hohmann, Andrea G.

    2015-01-01

    Aberrant increases in NMDA receptor (NMDAR) signaling contributes to central nervous system sensitization and chronic pain by activating neuronal nitric oxide synthase (nNOS) and generating nitric oxide (NO). Because the scaffolding protein postsynaptic density 95kDA (PSD95) tethers nNOS to NMDARs, the PSD95-nNOS complex represents a therapeutic target. Small molecule inhibitors IC87201 (EC5O: 23.94 µM) and ZL006 (EC50: 12.88 µM) directly inhibited binding of purified PSD95 and nNOS proteins in AlphaScreen without altering binding of PSD95 to ErbB4. Both PSD95-nNOS inhibitors suppressed glutamate-induced cell death with efficacy comparable to MK-801. IC87201 and ZL006 preferentially suppressed phase 2A pain behavior in the formalin test and suppressed allodynia induced by intraplantar complete Freund’s adjuvant administration. IC87201 and ZL006 suppressed mechanical and cold allodynia induced by the chemotherapeutic agent paclitaxel (ED50s: 2.47 and 0.93 mg/kg i.p. for IC87201 and ZL006, respectively). Efficacy of PSD95-nNOS disruptors was similar to MK-801. Motor ataxic effects were induced by MK-801 but not by ZL006 or IC87201. Finally, MK-801 produced hyperalgesia in the tail-flick test whereas IC87201 and ZL006 did not alter basal nociceptive thresholds. Our studies establish the utility of using AlphaScreen and purified protein pairs to establish and quantify disruption of protein-protein interactions. Our results demonstrate previously unrecognized antinociceptive efficacy of ZL006 and establish, using two small molecules, a broad application for PSD95-nNOS inhibitors in treating neuropathic and inflammatory pain. Collectively, our results demonstrate that disrupting PSD95-nNOS protein-protein interactions is effective in attenuating pathological pain without producing unwanted side effects (i.e. motor ataxia) associated with NMDAR antagonists. PMID:26071110

  9. Assessment of ZnT3 and PSD95 protein levels in Lewy body dementias and Alzheimer's disease: association with cognitive impairment.

    PubMed

    Whitfield, David R; Vallortigara, Julie; Alghamdi, Amani; Howlett, David; Hortobágyi, Tibor; Johnson, Mary; Attems, Johannes; Newhouse, Stephen; Ballard, Clive; Thomas, Alan J; O'Brien, John T; Aarsland, Dag; Francis, Paul T

    2014-12-01

    The loss of zinc transporter 3 (ZnT3) has been implicated in age-related cognitive decline in mice, and the protein has been associated with plaques. We investigated the levels of ZnT3 and postsynaptic density protein 95 (PSD95), a marker of the postsynaptic terminal, in people with Parkinson's disease dementia (PDD, n = 31), dementia with Lewy bodies (DLB, n = 44), Alzheimer's disease (AD, n = 16), and controls (n = 24), using semiquantitative western blotting and immunohistochemistry in 3 cortical regions. Standardized cognitive assessments during life and semiquantitative scoring of amyloid β (Aβ), tau, and α-synuclein at postmortem were used to investigate the relationship between ZnT3 and PSD95, cognition and pathology. Associations were observed between ZnT3 and PSD95 levels in prefrontal cortex and cognitive impairment (p = 0.001 and p = 0.002, respectively) and between ZnT3 levels in the parietal cortex and cognitive impairment (p = 0.036). Associations were also seen between ZnT3 levels in cingulate cortex and severity of Aβ (p = 0.003) and tau (p = 0.011) pathologies. DLB and PDD were characterized by significant reductions of PSD95 (p < 0.05) and ZnT3 (p < 0.001) in prefrontal cortex compared with controls and AD. PSD95 levels in the parietal cortex were found to be decreased in AD cases compared with controls (p = 0.02) and PDD (p = 0.005). This study has identified Zn(2+) modulation as a possible novel target for the treatment of cognitive impairment in DLB and PDD and the potential for synaptic proteins to be used as a biomarker for the differentiation of DLB and PDD from AD.

  10. A Specific Nutrient Combination Attenuates the Reduced Expression of PSD-95 in the Proximal Dendrites of Hippocampal Cell Body Layers in a Mouse Model of Phenylketonuria.

    PubMed

    Bruinenberg, Vibeke M; van Vliet, Danique; Attali, Amos; de Wilde, Martijn C; Kuhn, Mirjam; van Spronsen, Francjan J; van der Zee, Eddy A

    2016-03-26

    The inherited metabolic disease phenylketonuria (PKU) is characterized by increased concentrations of phenylalanine in the blood and brain, and as a consequence neurotransmitter metabolism, white matter, and synapse functioning are affected. A specific nutrient combination (SNC) has been shown to improve synapse formation, morphology and function. This could become an interesting new nutritional approach for PKU. To assess whether treatment with SNC can affect synapses, we treated PKU mice with SNC or an isocaloric control diet and wild-type (WT) mice with an isocaloric control for 12 weeks, starting at postnatal day 31. Immunostaining for post-synaptic density protein 95 (PSD-95), a post-synaptic density marker, was carried out in the hippocampus, striatum and prefrontal cortex. Compared to WT mice on normal chow without SNC, PKU mice on the isocaloric control showed a significant reduction in PSD-95 expression in the hippocampus, specifically in the granular cell layer of the dentate gyrus, with a similar trend seen in the cornus ammonis 1 (CA1) and cornus ammonis 3 (CA3) pyramidal cell layer. No differences were found in the striatum or prefrontal cortex. PKU mice on a diet supplemented with SNC showed improved expression of PSD-95 in the hippocampus. This study gives the first indication that SNC supplementation has a positive effect on hippocampal synaptic deficits in PKU mice.

  11. A Specific Nutrient Combination Attenuates the Reduced Expression of PSD-95 in the Proximal Dendrites of Hippocampal Cell Body Layers in a Mouse Model of Phenylketonuria

    PubMed Central

    Bruinenberg, Vibeke M.; van Vliet, Danique; Attali, Amos; de Wilde, Martijn C.; Kuhn, Mirjam; van Spronsen, Francjan J.; van der Zee, Eddy A.

    2016-01-01

    The inherited metabolic disease phenylketonuria (PKU) is characterized by increased concentrations of phenylalanine in the blood and brain, and as a consequence neurotransmitter metabolism, white matter, and synapse functioning are affected. A specific nutrient combination (SNC) has been shown to improve synapse formation, morphology and function. This could become an interesting new nutritional approach for PKU. To assess whether treatment with SNC can affect synapses, we treated PKU mice with SNC or an isocaloric control diet and wild-type (WT) mice with an isocaloric control for 12 weeks, starting at postnatal day 31. Immunostaining for post-synaptic density protein 95 (PSD-95), a post-synaptic density marker, was carried out in the hippocampus, striatum and prefrontal cortex. Compared to WT mice on normal chow without SNC, PKU mice on the isocaloric control showed a significant reduction in PSD-95 expression in the hippocampus, specifically in the granular cell layer of the dentate gyrus, with a similar trend seen in the cornus ammonis 1 (CA1) and cornus ammonis 3 (CA3) pyramidal cell layer. No differences were found in the striatum or prefrontal cortex. PKU mice on a diet supplemented with SNC showed improved expression of PSD-95 in the hippocampus. This study gives the first indication that SNC supplementation has a positive effect on hippocampal synaptic deficits in PKU mice. PMID:27102170

  12. Destabilization of the Postsynaptic Density by PSD-95 Serine 73 Phosphorylation Inhibits Spine Growth and Synaptic Plasticity

    PubMed Central

    Steiner, Pascal; Higley, Michael J.; Xu, Weifeng; Czervionke, Brian L.; Malenka, Robert C.; Sabatini, Bernardo L.

    2009-01-01

    SUMMARY Long-term potentiation (LTP) is accompanied by dendritic spine growth and changes in the composition of the postsynaptic density (PSD). We find that activity-dependent growth of apical spines of CA1 pyramidal neurons is accompanied by destabilization of the PSD that results in transient loss and rapid replacement of PSD-95 and SHANK2. Signaling through PSD-95 is required for activity-dependent spine growth and trafficking of SHANK2. N-terminal PDZ and C-terminal guanylate kinase domains of PSD-95 are required for both processes, indicating that PSD-95 coordinates multiple signals to regulate morphological plasticity. Activity-dependent trafficking of PSD-95 is triggered by phosphorylation at serine 73, a conserved calcium/calmodulin-dependent protein kinase II (CaMKII) consensus phosphorylation site, which negatively regulates spine growth and potentiation of synaptic currents. We propose that PSD-95 and CaMKII act at multiple steps during plasticity induction to initially trigger and later terminate spine growth by trafficking growth-promoting PSD proteins out of the active spine. PMID:19081375

  13. Resequencing and Association Analysis of Six PSD-95-Related Genes as Possible Susceptibility Genes for Schizophrenia and Autism Spectrum Disorders

    PubMed Central

    Xing, Jingrui; Kimura, Hiroki; Wang, Chenyao; Ishizuka, Kanako; Kushima, Itaru; Arioka, Yuko; Yoshimi, Akira; Nakamura, Yukako; Shiino, Tomoko; Oya-Ito, Tomoko; Takasaki, Yuto; Uno, Yota; Okada, Takashi; Iidaka, Tetsuya; Aleksic, Branko; Mori, Daisuke; Ozaki, Norio

    2016-01-01

    PSD-95 associated PSD proteins play a critical role in regulating the density and activity of glutamate receptors. Numerous previous studies have shown an association between the genes that encode these proteins and schizophrenia (SZ) and autism spectrum disorders (ASD), which share a substantial portion of genetic risks. We sequenced the protein-encoding regions of DLG1, DLG2, DLG4, DLGAP1, DLGAP2, and SynGAP in 562 cases (370 SZ and 192 ASD patients) on the Ion PGM platform. We detected 26 rare (minor allele frequency <1%), non-synonymous mutations, and conducted silico functional analysis and pedigree analysis when possible. Three variants, G344R in DLG1, G241S in DLG4, and R604C in DLGAP2, were selected for association analysis in an independent sample set of 1315 SZ patients, 382 ASD patients, and 1793 healthy controls. Neither DLG4-G241S nor DLGAP2-R604C was detected in any samples in case or control sets, whereas one additional SZ patient was found that carried DLG1-G344R. Our results suggest that rare missense mutations in the candidate PSD genes may increase susceptibility to SZ and/or ASD. These findings may strengthen the theory that rare, non-synonymous variants confer substantial genetic risks for these disorders. PMID:27271353

  14. Functional Uncoupling NMDAR NR2A Subunit from PSD-95 in the Prefrontal Cortex: Effects on Behavioral Dysfunction and Parvalbumin Loss after Early-Life Stress.

    PubMed

    Ganguly, Prabarna; Holland, Freedom H; Brenhouse, Heather C

    2015-11-01

    Exposure to early-life stress increases vulnerability to psychiatric disorders, including depression, schizophrenia, and anxiety. Growing evidence implicates aberrant development of the prefrontal cortex (PFC) in the effects of early-life stress, which often emerge in adolescence or young adulthood. Specifically, early-life stress in the form of maternal separation (MS) in rodents has been shown to decrease parvalbumin (PVB)-positive interneurons in the adolescent PFC; however, the mechanism underpinning behavioral dysfunction and PVB loss is not yet known. We recently reported that MS causes overexpression of the NMDA subunit NR2A in the PFC of adolescent rats. Elevated PFC NR2A is also found in developmental models of schizophrenia and is correlated with behavioral deficits, acting largely through its association with the postsynaptic protein PSD-95. In addition, adolescent maturation of PVB-positive interneurons relies on NR2A-driven NMDA activity. Therefore, it is possible that the NR2A/PSD-95 signaling complex has a role in adolescent MS effects. Here, we aimed to determine whether a discrete manipulation of PFC NR2A could prevent MS effects on PFC-controlled behaviors, including cognition, anxiety, and novelty-induced hyperlocomotion, as well as PVB loss in adolescence. We intracranially infused the NR2A-specific blocking peptide TAT2A in order to uncouple NR2A from PSD-95 in the early-adolescent PFC, without antagonizing the NMDA receptor. We demonstrated that MS rats treated with TAT2A during early adolescence were protected from MS-induced PVB loss and exhibited less anxious behavior than those infused with control peptide. These data implicate NR2A-related N-methyl-D-aspartate receptor development in adolescent behavioral and neural consequences of early-life stress.

  15. Transferrin Receptor Controls AMPA Receptor Trafficking Efficiency and Synaptic Plasticity

    PubMed Central

    Liu, Ke; Lei, Run; Li, Qiong; Wang, Xin-Xin; Wu, Qian; An, Peng; Zhang, Jianchao; Zhu, Minyan; Xu, Zhiheng; Hong, Yang; Wang, Fudi; Shen, Ying; Li, Hongchang; Li, Huashun

    2016-01-01

    Transferrin receptor (TFR) is an important iron transporter regulating iron homeostasis and has long been used as a marker for clathrin mediated endocytosis. However, little is known about its additional function other than iron transport in the development of central nervous system (CNS). Here we demonstrate that TFR functions as a regulator to control AMPA receptor trafficking efficiency and synaptic plasticity. The conditional knockout (KO) of TFR in neural progenitor cells causes mice to develop progressive epileptic seizure, and dramatically reduces basal synaptic transmission and long-term potentiation (LTP). We further demonstrate that TFR KO remarkably reduces the binding efficiency of GluR2 to AP2 and subsequently decreases AMPA receptor endocytosis and recycling. Thus, our study reveals that TFR functions as a novel regulator to control AMPA trafficking efficiency and synaptic plasticity. PMID:26880306

  16. In vitro and in vivo effects of a novel dimeric inhibitor of PSD-95 on excitotoxicity and functional recovery after experimental traumatic brain injury.

    PubMed

    Sommer, Jens Bak; Bach, Anders; Malá, Hana; Strømgaard, Kristian; Mogensen, Jesper; Pickering, Darryl S

    2017-01-01

    PSD-95 inhibitors have been shown to be neuroprotective in stroke, but have only to a very limited extent been evaluated in the treatment of traumatic brain injury (TBI) that has pathophysiological mechanisms in common with stroke. The aims of the current study were to assess the effects of a novel dimeric inhibitor of PSD-95, UCCB01-147, on histopathology and long-term cognitive outcome after controlled cortical impact (CCI) in rats. As excitotoxic cell death is thought to be a prominent part of the pathophysiology of TBI, we also investigated the neuroprotective effects of UCCB01-147 and related compounds on NMDA-induced cell death in cultured cortical neurons. Anesthetized rats were given a CCI or sham injury, and were randomized to receive an injection of either UCCB01-147 (10 mg/kg), the non-competitive NMDAR-receptor antagonist MK-801 (1 mg/kg) or saline immediately after injury. At 2 and 4 weeks post-trauma, spatial learning and memory were assessed in a water maze, and at 3 months, brains were removed for estimation of lesion volumes. Overall, neither treatment with UCCB01-147 nor MK-801 resulted in significant improvements of cognition and histopathology after CCI. Although MK-801 provided robust neuroprotection against NMDA-induced toxicity in cultured cortical neurons, UCCB01-147 failed to reduce cell death and became neurotoxic at high doses. The data suggest potential differential effects of PSD-95 inhibition in stroke and TBI that should be investigated further in future studies taking important experimental factors such as timing of treatment, dosage, and anesthesia into consideration.

  17. Effects of the dimeric PSD-95 inhibitor UCCB01-144 in mouse models of pain, cognition and motor function.

    PubMed

    Andreasen, Jesper T; Nasser, Arafat; Caballero-Puntiverio, Maitane; Sahlholt, Maj; Bach, Anders; Gynther, Mikko; Strømgaard, Kristian; Pickering, Darryl S

    2016-06-05

    NMDAR antagonism shows analgesic action in humans and animal pain models, but disrupts cognitive and motor functions. NMDAR-dependent NO production requires tethering of the NMDAR to neuronal NO synthase (nNOS) by the postsynaptic density protein-95 (PSD-95). Perturbing the NMDAR/PSD-95/nNOS interaction has therefore been proposed as an alternative analgesic mechanism. We recently reported that UCCB01-125, a dimeric PSD-95 inhibitor with limited blood-brain-barrier permeability, reduced mechanical hypersensitivity in the complete Freund's adjuvant (CFA) inflammatory pain model, without disrupting cognitive or motor functions. Here, we investigated the analgesic efficacy in the CFA model of UCCB01-144, a PSD-95 inhibitor with improved blood-brain-barrier permeability. To extend the comparison of UCCB01-125 and UCCB01-144, we also tested both compounds in the spared nerve injury (SNI) model of neuropathic pain. Potential cognitive effects of UCCB01-144 were examined using the social transmission of food preference (STFP) test and the V-maze test, and motor coordination was assessed with the rotarod test. UCCB01-144 (10mg/kg) reversed CFA-induced mechanical hypersensitivity after 1h, and completely normalised sensitivity after 24h. In the SNI model, UCCB01-144 (30mg/kg) partially reversed hypersensitivity after 1h, but no effect was observed after 24h. UCCB01-125 did not affect SNI-induced hypersensitivity. Rotarod performance was unaffected by UCCB01-144, but 30mg/kg UCCB01-144 impaired performance in the STFP test. Collectively, UCCB01-144 reversed both CFA and SNI-induced hypersensitivity, but the efficacy in the SNI model was only transient. This suggests that enhanced BBB permeability of PSD-95 inhibitors improves the analgesic action in neuropathic pain states.

  18. Interfering of the Reelin/ApoER2/PSD95 Signaling Axis Reactivates Dendritogenesis of Mature Hippocampal Neurons.

    PubMed

    Ampuero, Estibaliz; Jury, Nur; Härtel, Steffen; Marzolo, María-Paz; van Zundert, Brigitte

    2017-05-01

    Reelin, an extracellular glycoprotein secreted in embryonic and adult brain, participates in neuronal migration and neuronal plasticity. Extensive evidence shows that reelin via activation of the ApoER2 and VLDLR receptors promotes dendrite and spine formation during early development. Further evidence suggests that reelin signaling is needed to maintain a stable architecture in mature neurons, but, direct evidence is lacking. During activity-dependent maturation of the neuronal circuitry, the synaptic protein PSD95 is inserted into the postsynaptic membrane to induce structural refinement and stability of spines and dendrites. Given that ApoER2 interacts with PSD95, we tested if reelin signaling interference in adult neurons reactivates the dendritic architecture. Unlike findings in developing cultures, the presently obtained in vitro and in vivo data show, for the first time, that reelin signaling interference robustly increase dendritogenesis and reduce spine density in mature hippocampal neurons. In particular, the expression of a mutant ApoER2 form (ApoER2-tailless), which is unable to interact with PSD95 and hence cannot transduce reelin signaling, resulted in robust dendritogenesis in mature hippocampal neurons in vitro. These results indicate that reelin/ApoER2/PSD95 signaling is important for neuronal structure maintenance in mature neurons. Mechanistically, obtained immunofluorescent data indicate that reelin signaling impairment reduced synaptic PSD95 levels, consequently leading to synaptic re-insertion of NR2B-NMDARs. Our findings underscore the importance of reelin in maintaining adult network stability and reveal a new mode for reactivating dendritogenesis in neurological disorders where dendritic arbor complexity is limited, such as in depression, Alzheimer's disease, and stroke. J. Cell. Physiol. 232: 1187-1199, 2017. © 2016 Wiley Periodicals, Inc.

  19. Drug Transporters and Na+/H+ Exchange Regulatory Factor PSD-95/Drosophila Discs Large/ZO-1 Proteins

    PubMed Central

    Walsh, Dustin R.; Nolin, Thomas D.

    2015-01-01

    Drug transporters govern the absorption, distribution, and elimination of pharmacologically active compounds. Members of the solute carrier and ATP binding-cassette drug transporter family mediate cellular drug uptake and efflux processes, thereby coordinating the vectorial movement of drugs across epithelial barriers. To exert their physiologic and pharmacological function in polarized epithelia, drug transporters must be targeted and stabilized to appropriate regions of the cell membrane (i.e., apical versus basolateral). Despite the critical importance of drug transporter membrane targeting, the mechanisms that underlie these processes are largely unknown. Several clinically significant drug transporters possess a recognition sequence that binds to PSD-95/Drosophila discs large/ZO-1 (PDZ) proteins. PDZ proteins, such as the Na+/H+ exchanger regulatory factor (NHERF) family, act to stabilize and organize membrane targeting of multiple transmembrane proteins, including many clinically relevant drug transporters. These PDZ proteins are normally abundant at apical membranes, where they tether membrane-delimited transporters. NHERF expression is particularly high at the apical membrane in polarized tissue such as intestinal, hepatic, and renal epithelia, tissues important to drug disposition. Several recent studies have highlighted NHERF proteins as determinants of drug transporter function secondary to their role in controlling membrane abundance and localization. Mounting evidence strongly suggests that NHERF proteins may have clinically significant roles in pharmacokinetics and pharmacodynamics of several pharmacologically active compounds and may affect drug action in cancer and chronic kidney disease. For these reasons, NHERF proteins represent a novel class of post-translational mediators of drug transport and novel targets for new drug development. PMID:26092975

  20. TARP gamma-8 controls hippocampal AMPA receptor number, distribution and synaptic plasticity.

    PubMed

    Rouach, Nathalie; Byrd, Keith; Petralia, Ronald S; Elias, Guillermo M; Adesnik, Hillel; Tomita, Susumu; Karimzadegan, Siavash; Kealey, Colin; Bredt, David S; Nicoll, Roger A

    2005-11-01

    Synaptic plasticity involves activity-dependent trafficking of AMPA-type glutamate receptors. Numerous cytoplasmic scaffolding proteins are postulated to control AMPA receptor trafficking, but the detailed mechanisms remain unclear. Here, we show that the transmembrane AMPA receptor regulatory protein (TARP) gamma-8, which is preferentially expressed in the mouse hippocampus, is important for AMPA receptor protein levels and extrasynaptic surface expression. By controlling the number of AMPA receptors, gamma-8 is also important in long-term potentiation, but not long-term depression. This study establishes gamma-8 as a critical protein for basal AMPA receptor expression and localization at extrasynaptic sites in the hippocampus and raises the possibility that TARP-dependent control of AMPA receptors during synapse development and plasticity may be widespread.

  1. Protection of neuronal cells from excitotoxicity by disrupting nNOS-PSD95 interaction with a small molecule SCR-4026.

    PubMed

    Mo, Shi-Fu; Liao, Gao-Yong; Yang, Jie; Wang, Meng-Yu; Hu, Yang; Lian, Guo-Ning; Kong, Ling-Dong; Zhao, Yong

    2016-10-01

    Stroke is a major public health problem leading to high rates of death and disability in adults. Coupling of postsynaptic density protein-95 (PSD-95) and neuronal nitric oxide synthase (nNOS) plays an important part in neuronal damage caused by stroke. Recent studies suggest the possibility of alleviating post ischemia neuron damage by blocking ischemia-induced nNOS-PSD-95 association. Here, we report a small-molecular inhibitor of nNOS-PSD-95 interaction, SCR-4026, which exhibits neuroprotective activities in NMDA-induced or Oxygen and glucose deprivation (OGD)-induced neuronal damage in primary cortical neurons cultures, and ameliorated focal cerebral ischemic damage in rats subjected to middle cerebral artery occlusion (MCAO) and reperfusion. Furthermore, we found that SCR-4026 was also able to promote neural stem cells to differentiate into neurons-like cells, which is potentially of great significance for neural protection. Taken together, SCR-4026 is identified as a novel small molecule that shows great potential in treating stroke.

  2. Post-translational modifications modulate ligand recognition by the third PDZ domain of the MAGUK protein PSD-95.

    PubMed

    Murciano-Calles, Javier; Corbi-Verge, Carles; Candel, Adela M; Luque, Irene; Martinez, Jose C

    2014-01-01

    The relative promiscuity of hub proteins such as postsynaptic density protein-95 (PSD-95) can be achieved by alternative splicing, allosteric regulation, and post-translational modifications, the latter of which is the most efficient method of accelerating cellular responses to environmental changes in vivo. Here, a mutational approach was used to determine the impact of phosphorylation and succinimidation post-translational modifications on the binding affinity of the postsynaptic density protein-95/discs large/zonula occludens-1 (PDZ3) domain of PSD-95. Molecular dynamics simulations revealed that the binding affinity of this domain is influenced by an interplay between salt-bridges linking the α3 helix, the β2-β3 loop and the positively charged Lys residues in its high-affinity hexapeptide ligand KKETAV. The α3 helix is an extra structural element that is not present in other PDZ domains, which links PDZ3 with the following SH3 domain in the PSD-95 protein. This regulatory mechanism was confirmed experimentally via thermodynamic and NMR chemical shift perturbation analyses, discarding intra-domain long-range effects. Taken together, the results presented here reveal the molecular basis of the regulatory role of the α3 extra-element and the effects of post-translational modifications of PDZ3 on its binding affinity, both energetically and dynamically.

  3. ATP from synaptic terminals and astrocytes regulates NMDA receptors and synaptic plasticity through PSD-95 multi-protein complex

    PubMed Central

    Lalo, U.; Palygin, O.; Verkhratsky, A.; Grant, S. G. N.; Pankratov, Y.

    2016-01-01

    Recent studies highlighted the importance of astrocyte-secreted molecules, such as ATP, for the slow modulation of synaptic transmission in central neurones. Biophysical mechanisms underlying the impact of gliotransmitters on the strength of individual synapse remain, however, unclear. Here we show that purinergic P2X receptors can bring significant contribution to the signalling in the individual synaptic boutons. ATP released from astrocytes facilitates a recruitment of P2X receptors into excitatory synapses by Ca2+-dependent mechanism. P2X receptors, co-localized with NMDA receptors in the excitatory synapses, can be activated by ATP co-released with glutamate from pre-synaptic terminals and by glia-derived ATP. An activation of P2X receptors in turn leads to down-regulation of postsynaptic NMDA receptors via Ca2+-dependent de-phosphorylation and interaction with PSD-95 multi-protein complex. Genetic deletion of the PSD-95 or P2X4 receptors obliterated ATP-mediated down-regulation of NMDA receptors. Impairment of purinergic modulation of NMDA receptors in the PSD-95 mutants dramatically decreased the threshold of LTP induction and increased the net magnitude of LTP. Our findings show that synergistic action of glia- and neurone-derived ATP can pre-modulate efficacy of excitatory synapses and thereby can have an important role in the glia-neuron communications and brain meta-plasticity. PMID:27640997

  4. Seizure control by decanoic acid through direct AMPA receptor inhibition

    PubMed Central

    Chang, Pishan; Augustin, Katrin; Boddum, Kim; Williams, Sophie; Sun, Min; Terschak, John A.; Hardege, Jörg D.; Chen, Philip E.

    2016-01-01

    See Rogawski (doi:10.1093/awv369) for a scientific commentary on this article.  The medium chain triglyceride ketogenic diet is an established treatment for drug-resistant epilepsy that increases plasma levels of decanoic acid and ketones. Recently, decanoic acid has been shown to provide seizure control in vivo, yet its mechanism of action remains unclear. Here we show that decanoic acid, but not the ketones β-hydroxybutryate or acetone, shows antiseizure activity in two acute ex vivo rat hippocampal slice models of epileptiform activity. To search for a mechanism of decanoic acid, we show it has a strong inhibitory effect on excitatory, but not inhibitory, neurotransmission in hippocampal slices. Using heterologous expression of excitatory ionotropic glutamate receptor AMPA subunits in Xenopus oocytes, we show that this effect is through direct AMPA receptor inhibition, a target shared by a recently introduced epilepsy treatment perampanel. Decanoic acid acts as a non-competitive antagonist at therapeutically relevant concentrations, in a voltage- and subunit-dependent manner, and this is sufficient to explain its antiseizure effects. This inhibitory effect is likely to be caused by binding to sites on the M3 helix of the AMPA-GluA2 transmembrane domain; independent from the binding site of perampanel. Together our results indicate that the direct inhibition of excitatory neurotransmission by decanoic acid in the brain contributes to the anti-convulsant effect of the medium chain triglyceride ketogenic diet. PMID:26608744

  5. 2-Methyl-6-(phenylethynyl) pyridine (MPEP) reverses maze learning and PSD-95 deficits in Fmr1 knock-out mice

    PubMed Central

    Gandhi, Réno M.; Kogan, Cary S.; Messier, Claude

    2014-01-01

    Fragile X Syndrome (FXS) is caused by the lack of expression of the fragile X mental retardation protein (FMRP), which results in intellectual disability and other debilitating symptoms including impairment of visual-spatial functioning. FXS is the only single-gene disorder that is highly co-morbid with autism spectrum disorder and can therefore provide insight into its pathophysiology. Lack of FMRP results in altered group I metabotropic glutamate receptor (mGluR) signaling, which is a target for putative treatments. The Hebb-Williams (H-W) mazes are a set of increasingly complex spatial navigation problems that depend on intact hippocampal and thus mGluR-5 functioning. In the present investigation, we examined whether an antagonist of mGluR-5 would reverse previously described behavioral deficits in fragile X mental retardation 1 knock-out (Fmr1 KO) mice. Mice were trained on a subset of the H-W mazes and then treated with either 20 mg/kg of an mGluR-5 antagonist, 2-Methyl-6-(phenylethynyl) pyridine (MPEP; n = 11) or an equivalent dose of saline (n = 11) prior to running test mazes. Latency and errors were dependent variables recorded during the test phase. Immediately after completing each test, marble-burying behavior was assessed, which confirmed that the drug treatment was pharmacologically active during maze learning. Although latency was not statistically different between the groups, MPEP treated Fmr1 KO mice made significantly fewer errors on mazes deemed more difficult suggesting a reversal of the behavioral deficit. MPEP treated mice were also less perseverative and impulsive when navigating mazes. Furthermore, MPEP treatment reversed post-synaptic density-95 (PSD-95) protein deficits in Fmr1 KO treated mice, whereas levels of a control protein (β-tubulin) remained unchanged. These data further validate MPEP as a potentially beneficial treatment for FXS. Our findings also suggest that adapted H-W mazes may be a useful tool to document alterations in

  6. Investigation into the effects of prenatal alcohol exposure on postnatal spine development and expression of synaptophysin and PSD95 in rat hippocampus.

    PubMed

    Elibol-Can, Birsen; Kilic, Ertugrul; Yuruker, Sinan; Jakubowska-Dogru, Ewa

    2014-04-01

    Ethanol is known as a potent teratogen responsible for the fetal alcohol syndrome characterized by cognitive deficits especially pronounced in juveniles but ameliorating in adults. Since the mechanisms of these deficits and following partial recovery are not fully elucidated, the aim of the present study was to investigate the process of synaptogenesis in the hippocampus over the first two months of life in control and fetal-alcohol rats. Ethanol was delivered to the pregnant dams by intragastric intubation throughout 7-21 gestation days at the daily dose of 6g/kg generating a mean blood alcohol level of 246.6±40.9mg/dl on gestation day 20. The spine densities as well as the expression of pre- and postsynaptic proteins, synaptophysin (SYP) and PSD-95 protein, were evaluated for three distinct hippocampal regions: CA1, CA2+3, and DG and four postnatal days: PD1, PD10, PD30 and PD60, independently. Our results confirmed an intensive synaptogenesis within the brain spurt period (first 10 postnatal days), however, the temporal pattern of changes in the SYP and PSD-95 expression was different. The ethanol exposure during half of the 1st and the whole 2nd human trimester equivalent resulted in an overall trend toward lower values of synaptic indices at PD1 with a fast recovery from these deficits observed already at PD10. At PD30, around the age when the most pronounced behavioral deficits have been previously reported in juvenile fetal-alcohol subjects, no significant changes were found in either the hippocampal levels of synaptic proteins or in the spine density in principal hippocampal neurons.

  7. Spinal SIRPα1-SHP2 interaction regulates spinal nerve ligation-induced neuropathic pain via PSD-95-dependent NR2B activation in rats.

    PubMed

    Peng, Hsien-Yu; Chen, Gin-Den; Lai, Cheng-Yuang; Hsieh, Ming-Chun; Lin, Tzer-Bin

    2012-05-01

    The fact that neuropathic pain mechanisms are not well understood is a major impediment in the development of effective clinical treatments. We examined whether the interaction between signal regulatory protein alpha 1 (SIRPα1) and Src homology-2 domain-containing protein tyrosine phosphatase 2 (SHP2), and the downstream spinal SHP2/postsynaptic density 95 (PSD-95)/N-methyl-d-aspartate receptor NR2B subunit signaling cascade play a role in neuropathic pain. Following spinal nerve ligation (L5), we assessed tactile allodynia using the von Frey filament test and analyzed dorsal horn samples (L4-5) by Western blotting, reverse transcription polymerase chain reaction, coimmunoprecipitation, and immunofluorescence. Nerve ligation induced allodynia, SIRPα1, SHP2, phosphorylated SHP2 (pSHP2), and phosphorylated NR2B (pNR2B) expression, and SHP2-PSD-95, pSHP2-PSD-95, PSD-95-NR2B, and PSD-95-pNR2B coimmunoprecipitation in the ipsilateral dorsal horn. In allodynic rats, injury-induced SHP2 immunoreactivity was localized in the ipsilateral dorsal horn neurons and coincident with PSD-95 and NR2B immunoreactivity. SIRPα1 silencing using small interfering RNA (siRNA; 1, 3, or 5μg/rat for 7days) prevented injury-induced allodynia and the associated changes in protein expression, phosphorylation, and coimmunoprecipitation. Intrathecal administration of NSC-87877 (an SHP2 antagonist; 1, 10, or 100μM/rat) and SIRPα1-neutralizing antibodies (1, 10, or 30μg/rat) suppressed spinal nerve ligation-induced allodynia, spinal SHP2 and NR2B phosphorylation, and SHP2/phosphorylated SHP2-PSD-95 and PSD-95-NR2B/phosphorylated NR2B coprecipitation. SHP2 siRNA led to similar effects as the NSC-87877 and SIRPα1 antibody treatments, except it prevented the allodynia-associated spinal SHP2 expression. In conclusion, our results suggest that a spinal SIRPα1-SHP2 interaction exists that subsequently triggers SHP2/PSD-95/NR2B signaling, thereby playing a role in neuropathic pain development.

  8. Biochemical investigations of the mechanism of action of small molecules ZL006 and IC87201 as potential inhibitors of the nNOS-PDZ/PSD-95-PDZ interactions

    PubMed Central

    Bach, Anders; Pedersen, Søren W.; Dorr, Liam A.; Vallon, Gary; Ripoche, Isabelle; Ducki, Sylvie; Lian, Lu-Yun

    2015-01-01

    ZL006 and IC87201 have been presented as efficient inhibitors of the nNOS/PSD-95 protein-protein interaction and shown great promise in cellular experiments and animal models of ischemic stroke and pain. Here, we investigate the proposed mechanism of action of ZL006 and IC87201 using biochemical and biophysical methods, such as fluorescence polarization (FP), isothermal titration calorimetry (ITC), and 1H-15N HSQC NMR. Our data show that under the applied in vitro conditions, ZL006 and IC87201 do not interact with the PDZ domains of nNOS or PSD-95, nor inhibit the nNOS-PDZ/PSD-95-PDZ interface by interacting with the β-finger of nNOS-PDZ. Our findings have implications for further medicinal chemistry efforts of ZL006, IC87201 and analogues, and challenge the general and widespread view on their mechanism of action. PMID:26177569

  9. PSD95 suppresses dendritic arbor development in mature hippocampal neurons by occluding the clustering of NR2B-NMDA receptors.

    PubMed

    Bustos, Fernando J; Varela-Nallar, Lorena; Campos, Matias; Henriquez, Berta; Phillips, Marnie; Opazo, Carlos; Aguayo, Luis G; Montecino, Martin; Constantine-Paton, Martha; Inestrosa, Nibaldo C; van Zundert, Brigitte

    2014-01-01

    Considerable evidence indicates that the NMDA receptor (NMDAR) subunits NR2A and NR2B are critical mediators of synaptic plasticity and dendritogenesis; however, how they differentially regulate these processes is unclear. Here we investigate the roles of the NR2A and NR2B subunits, and of their scaffolding proteins PSD-95 and SAP102, in remodeling the dendritic architecture of developing hippocampal neurons (2-25 DIV). Analysis of the dendritic architecture and the temporal and spatial expression patterns of the NMDARs and anchoring proteins in immature cultures revealed a strong positive correlation between synaptic expression of the NR2B subunit and dendritogenesis. With maturation, the pruning of dendritic branches was paralleled by a strong reduction in overall and synaptic expression of NR2B, and a significant elevation in synaptic expression of NR2A and PSD95. Using constructs that alter the synaptic composition, we found that either over-expression of NR2B or knock-down of PSD95 by shRNA-PSD95 augmented dendritogenesis in immature neurons. Reactivation of dendritogenesis could also be achieved in mature cultured neurons, but required both manipulations simultaneously, and was accompanied by increased dendritic clustering of NR2B. Our results indicate that the developmental increase in synaptic expression of PSD95 obstructs the synaptic clustering of NR2B-NMDARs, and thereby restricts reactivation of dendritic branching. Experiments with shRNA-PSD95 and chimeric NR2A/NR2B constructs further revealed that C-terminus of the NR2B subunit (tail) was sufficient to induce robust dendritic branching in mature hippocampal neurons, and suggest that the NR2B tail is important in recruiting calcium-dependent signaling proteins and scaffolding proteins necessary for dendritogenesis.

  10. TARP phosphorylation regulates synaptic AMPA receptors through lipid bilayers.

    PubMed

    Sumioka, Akio; Yan, Dan; Tomita, Susumu

    2010-06-10

    Neurons use neurotransmitters to communicate across synapses, constructing neural circuits in the brain. AMPA-type glutamate receptors are the predominant excitatory neurotransmitter receptors mediating fast synaptic transmission. AMPA receptors localize at synapses by forming protein complexes with transmembrane AMPA receptor regulatory proteins (TARPs) and PSD-95-like membrane-associated guanylate kinases. Among the three classes of ionotropic glutamate receptors (AMPA, NMDA, and kainate type), AMPA receptor activity is most regulatable by neuronal activity to adjust synaptic strength. Here, we mutated the prototypical TARP, stargazin, and found that TARP phosphorylation regulates synaptic AMPA receptor activity in vivo. We also found that stargazin interacts with negatively charged lipid bilayers in a phosphorylation-dependent manner and that the lipid interaction inhibited stargazin binding to PSD-95. Cationic lipids dissociated stargazin from lipid bilayers and enhanced synaptic AMPA receptor activity in a stargazin phosphorylation-dependent manner. Thus, TARP phosphorylation plays a critical role in regulating AMPA receptor-mediated synaptic transmission via a lipid bilayer interaction.

  11. TARP phosphorylation regulates synaptic AMPA receptors through lipid bilayers

    PubMed Central

    Sumioka, Akio; Yan, Dan; Tomita, Susumu

    2010-01-01

    Summary Neurons use neurotransmitters to communicate across synapses, constructing neural circuits in the brain. AMPA-type glutamate receptors are the predominant excitatory neurotransmitter receptors mediating fast synaptic transmission. AMPA receptors localize at synapses by forming protein complexes with transmembrane AMPA receptor regulatory proteins (TARPs) and PSD-95-like MAGUKs. Among the three classes of ionotropic glutamate receptors (AMPA-, NMDA, kainate-type), AMPA receptor activity is most regulatable by neuronal activity to adjust synaptic strength. Here, we mutated the prototypical TARP, stargazin, and found that TARP phosphorylation regulates synaptic AMPA receptor activity in vivo. We also found that stargazin interacts with negatively-charged lipid bilayers in its phosphorylation dependent manner, and that the lipid interaction inhibited stargazin binding to PSD-95. Cationic lipids dissociated stargazin from lipid bilayers and enhanced synaptic AMPA receptor activity in a stargazin phosphorylation-dependent manner. Thus, TARP phosphorylation plays a critical role in regulating AMPA receptor-mediated synaptic transmission via a lipid bilayer interaction. PMID:20547132

  12. Spinal serum-inducible and glucocorticoid-inducible kinase 1 mediates neuropathic pain via kalirin and downstream PSD-95-dependent NR2B phosphorylation in rats.

    PubMed

    Peng, Hsien-Yu; Chen, Gin-Den; Lai, Cheng-Yuan; Hsieh, Ming-Chun; Lin, Tzer-Bin

    2013-03-20

    The coupling of the spinal postsynaptic density-95 (PSD-95) with the glutamatergic N-methyl-d-aspartate receptor NR2B subunit and the subsequent NR2B phosphorylation contribute to pain-related plasticity. Increasing evidence reveals that kalirin, a Rho-guanine nucleotide exchange factor, modulates PSD-95-NR2B-dependent neuroplasticity. Our laboratory recently demonstrated that serum-inducible and glucocorticoid-inducible kinase 1 (SGK1) participates in inflammation-associated pain hypersensitivity by modulating spinal glutamatergic neurotransmission. Because kalirin is one of the proteins in PSD that is highly phosphorylated by various kinases, we tested whether kalirin could be a downstream target of spinal SGK1 that participates in neuropathic pain development via regulation of the PSD-95-NR2B coupling-dependent phosphorylation of NR2B. We observed that spinal nerve ligation (SNL, L5) in male Sprague Dawley rats resulted in behavioral allodynia, which was associated with phosphorylated SGK1 (pSGK1), kalirin, and phosphorylated NR2B (pNR2B) expression and an increase in pSGK1-kalirin-PSD-95-pNR2B coprecipitation in the ipsilateral dorsal horn (L4-L5). SNL-enhanced kalirin immunofluorescence was coincident with pSGK1, PSD-95, and pNR2B immunoreactivity. Small-interfering RNA (siRNA) that targeted spinal kalirin mRNA expression (10 μg, 10 μl; i.t.) reduced SNL-induced allodynia, kalirin and pNR2B expression, as well as kalirin-PSD-95 and PSD-95-pNR2B coupling and costaining without affecting SGK1 phosphorylation. Daily administration of GSK-650394 (an SGK1 antagonist; 100 nm, 10 μl, i.t.) not only exhibited effects similar to the kalirin mRNA-targeting siRNA but also attenuated pSGK1-kalirin costaining and SGK1-kalirin coupling. We suggest that nerve injury could induce spinal SGK1 phosphorylation that subsequently interacts with and upregulates kalirin to participate in neuropathic pain development via PSD-95-NR2B coupling-dependent NR2B phosphorylation.

  13. ABP: a novel AMPA receptor binding protein.

    PubMed

    Srivastava, S; Ziff, E B

    1999-04-30

    We review the cloning of a novel AMPA receptor binding protein (ABP) that interacts with GluR2/3 and is homologous to GRIP. ABP is enriched in the PSD with GluR2 and is localized to the PSD by EM. ABP binds GluR2 via the C-terminal VXI motif through a Class I PDZ interaction. ABP and GRIP can also homo- and heteromultimerize. Thus, ABP and GRIP may be involved in AMPA receptor regulation and localization, by linking it to other cytoskeletal or signaling molecules. We suggest that the ABP/GRIP and PSD-95 families form distinct scaffolds that anchor, respectively, AMPA and NMDA receptors. We are currently investigating proteins that bind ABP and that may regulate the AMPA receptor.

  14. DHA-PC and PSD-95 decrease after loss of synaptophysin and before neuronal loss in patients with Alzheimer's disease.

    PubMed

    Yuki, Dai; Sugiura, Yuki; Zaima, Nobuhiro; Akatsu, Hiroyasu; Takei, Shiro; Yao, Ikuko; Maesako, Masato; Kinoshita, Ayae; Yamamoto, Takayuki; Kon, Ryo; Sugiyama, Keikichi; Setou, Mitsutoshi

    2014-11-20

    Alzheimer's disease (AD) is a progressive neurodegenerative disease that is characterized by senile plaques, neurofibrillary tangles, synaptic disruption, and neuronal loss. Several studies have demonstrated decreases of docosahexaenoic acid-containing phosphatidylcholines (DHA-PCs) in the AD brain. In this study, we used matrix-assisted laser desorption/ionization imaging mass spectrometry in postmortem AD brain to show that PC molecular species containing stearate and DHA, namely PC(18:0/22:6), was selectively depleted in the gray matter of patients with AD. Moreover, in the brain regions with marked amyloid β (Aβ) deposition, the magnitude of the PC(18:0/22:6) reduction significantly correlated with disease duration. Furthermore, at the molecular level, this depletion was associated with reduced levels of the postsynaptic protein PSD-95 but not the presynaptic protein synaptophysin. Interestingly, this reduction in PC(18:0/22:6) levels did not correlate with the degrees of Aβ deposition and neuronal loss in AD. The analysis of the correlations of key factors and disease duration showed that their effects on the disease time course were arranged in order as Aβ deposition, presynaptic disruption, postsynaptic disruption coupled with PC(18:0/22:6) reduction, and neuronal loss.

  15. Characterization of physiological phenotypes of dentate gyrus synapses of PDZ1/2 domain-deficient PSD-95-knockin mice.

    PubMed

    Nagura, Hitoshi; Doi, Tomoko; Fujiyoshi, Yoshinori

    2016-03-01

    The hippocampal formation is involved in several important brain functions of animals, such as memory formation and pattern separation, and the synapses in the dentate gyrus (DG) play critical roles as the first step in the hippocampal circuit. Previous studies have reported that mice with genetic modifications of the PDZ1/2 domains of postsynaptic density (PSD)-95 exhibit altered synaptic properties in the DG and impaired hippocampus-dependent behaviors. Based on the involvement of the DG in the regulation of behaviors, these data suggest that the abnormal behavior of these knockin (KI) mice is due partly to altered DG function. Precise understanding of the phenotypes of these mutant mice requires characterization of the synaptic properties of the DG, and here we provide detailed studies of DG synapses. We have demonstrated global changes in the PSD membrane-associated guanylate kinase expression pattern in the DG of mutant mice, and DG synapses in these mice exhibited increased long-term potentiation under a wide range of stimulus intensities, although the N-methyl-d-aspartic acid receptor dependence of the long-term potentiation was unchanged. Furthermore, our data also indicate increased silent synapses in the DG of the KI mice. These findings suggest that abnormal protein expression and physiological properties disrupt the function of DG neurons in these KI mice.

  16. The Human PDZome: A Gateway to PSD95-Disc Large-Zonula Occludens (PDZ)-mediated Functions*

    PubMed Central

    Belotti, Edwige; Polanowska, Jolanta; Daulat, Avais M.; Audebert, Stéphane; Thomé, Virginie; Lissitzky, Jean-Claude; Lembo, Frédérique; Blibek, Karim; Omi, Shizue; Lenfant, Nicolas; Gangar, Akanksha; Montcouquiol, Mireille; Santoni, Marie-Josée; Sebbagh, Michael; Aurrand-Lions, Michel; Angers, Stéphane; Kodjabachian, Laurent; Reboul, Jérome; Borg, Jean-Paul

    2013-01-01

    Protein–protein interactions organize the localization, clustering, signal transduction, and degradation of cellular proteins and are therefore implicated in numerous biological functions. These interactions are mediated by specialized domains able to bind to modified or unmodified peptides present in binding partners. Among the most broadly distributed protein interaction domains, PSD95-disc large-zonula occludens (PDZ) domains are usually able to bind carboxy-terminal sequences of their partners. In an effort to accelerate the discovery of PDZ domain interactions, we have constructed an array displaying 96% of the human PDZ domains that is amenable to rapid two-hybrid screens in yeast. We have demonstrated that this array can efficiently identify interactions using carboxy-terminal sequences of PDZ domain binders such as the E6 oncoviral protein and protein kinases (PDGFRβ, BRSK2, PCTK1, ACVR2B, and HER4); this has been validated via mass spectrometry analysis. Taking advantage of this array, we show that PDZ domains of Scrib and SNX27 bind to the carboxy-terminal region of the planar cell polarity receptor Vangl2. We also have demonstrated the requirement of Scrib for the promigratory function of Vangl2 and described the morphogenetic function of SNX27 in the early Xenopus embryo. The resource presented here is thus adapted for the screen of PDZ interactors and, furthermore, should facilitate the understanding of PDZ-mediated functions. PMID:23722234

  17. DHA-PC and PSD-95 decrease after loss of synaptophysin and before neuronal loss in patients with Alzheimer's disease

    PubMed Central

    Yuki, Dai; Sugiura, Yuki; Zaima, Nobuhiro; Akatsu, Hiroyasu; Takei, Shiro; Yao, Ikuko; Maesako, Masato; Kinoshita, Ayae; Yamamoto, Takayuki; Kon, Ryo; Sugiyama, Keikichi; Setou, Mitsutoshi

    2014-01-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disease that is characterized by senile plaques, neurofibrillary tangles, synaptic disruption, and neuronal loss. Several studies have demonstrated decreases of docosahexaenoic acid-containing phosphatidylcholines (DHA-PCs) in the AD brain. In this study, we used matrix-assisted laser desorption/ionization imaging mass spectrometry in postmortem AD brain to show that PC molecular species containing stearate and DHA, namely PC(18:0/22:6), was selectively depleted in the gray matter of patients with AD. Moreover, in the brain regions with marked amyloid β (Aβ) deposition, the magnitude of the PC(18:0/22:6) reduction significantly correlated with disease duration. Furthermore, at the molecular level, this depletion was associated with reduced levels of the postsynaptic protein PSD-95 but not the presynaptic protein synaptophysin. Interestingly, this reduction in PC(18:0/22:6) levels did not correlate with the degrees of Aβ deposition and neuronal loss in AD. The analysis of the correlations of key factors and disease duration showed that their effects on the disease time course were arranged in order as Aβ deposition, presynaptic disruption, postsynaptic disruption coupled with PC(18:0/22:6) reduction, and neuronal loss. PMID:25410733

  18. CDKL5 ensures excitatory synapse stability by reinforcing NGL-1-PSD95 interaction in the postsynaptic compartment and is impaired in patient iPSC-derived neurons.

    PubMed

    Ricciardi, Sara; Ungaro, Federica; Hambrock, Melanie; Rademacher, Nils; Stefanelli, Gilda; Brambilla, Dario; Sessa, Alessandro; Magagnotti, Cinzia; Bachi, Angela; Giarda, Elisa; Verpelli, Chiara; Kilstrup-Nielsen, Charlotte; Sala, Carlo; Kalscheuer, Vera M; Broccoli, Vania

    2012-09-01

    Mutations of the cyclin-dependent kinase-like 5 (CDKL5) and netrin-G1 (NTNG1) genes cause a severe neurodevelopmental disorder with clinical features that are closely related to Rett syndrome, including intellectual disability, early-onset intractable epilepsy and autism. We report here that CDKL5 is localized at excitatory synapses and contributes to correct dendritic spine structure and synapse activity. To exert this role, CDKL5 binds and phosphorylates the cell adhesion molecule NGL-1. This phosphorylation event ensures a stable association between NGL-1 and PSD95. Accordingly, phospho-mutant NGL-1 is unable to induce synaptic contacts whereas its phospho-mimetic form binds PSD95 more efficiently and partially rescues the CDKL5-specific spine defects. Interestingly, similarly to rodent neurons, iPSC-derived neurons from patients with CDKL5 mutations exhibit aberrant dendritic spines, thus suggesting a common function of CDKL5 in mice and humans.

  19. Binding of amyloid beta peptide to beta2 adrenergic receptor induces PKA-dependent AMPA receptor hyperactivity.

    PubMed

    Wang, Dayong; Govindaiah, G; Liu, Ruijie; De Arcangelis, Vania; Cox, Charles L; Xiang, Yang K

    2010-09-01

    Progressive decrease in neuronal function is an established feature of Alzheimer's disease (AD). Previous studies have shown that amyloid beta (Abeta) peptide induces acute increase in spontaneous synaptic activity accompanied by neurotoxicity, and Abeta induces excitotoxic neuronal death by increasing calcium influx mediated by hyperactive alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors. An in vivo study has revealed subpopulations of hyperactive neurons near Abeta plaques in mutant amyloid precursor protein (APP)-transgenic animal model of Alzheimer's disease (AD) that can be normalized by an AMPA receptor antagonist. In the present study, we aim to determine whether soluble Abeta acutely induces hyperactivity of AMPA receptors by a mechanism involving beta(2) adrenergic receptor (beta(2)AR). We found that the soluble Abeta binds to beta(2)AR, and the extracellular N terminus of beta(2)AR is critical for the binding. The binding is required to induce G-protein/cAMP/protein kinase A (PKA) signaling, which controls PKA-dependent phosphorylation of GluR1 and beta(2)AR, and AMPA receptor-mediated excitatory postsynaptic currents (EPSCs). beta(2)AR and GluR1 also form a complex comprising postsynaptic density protein 95 (PSD95), PKA and its anchor AKAP150, and protein phosphotase 2A (PP2A). Both the third intracellular (i3) loop and C terminus of beta(2)AR are required for the beta(2)AR/AMPA receptor complex. Abeta acutely induces PKA phosphorylation of GluR1 in the complex without affecting the association between two receptors. The present study reveals that non-neurotransmitter Abeta has a binding capacity to beta(2)AR and induces PKA-dependent hyperactivity in AMPA receptors.

  20. TARP subtypes differentially and dose-dependently control synaptic AMPA receptor gating.

    PubMed

    Milstein, Aaron D; Zhou, Wei; Karimzadegan, Siavash; Bredt, David S; Nicoll, Roger A

    2007-09-20

    A family of transmembrane AMPA receptor regulatory proteins (TARPs) profoundly affects the trafficking and gating of AMPA receptors (AMPARs). Although TARP subtypes are differentially expressed throughout the CNS, it is unclear whether this imparts functional diversity to AMPARs in distinct neuronal populations. Here, we examine the effects of each TARP subtype on the kinetics of AMPAR gating in heterologous cells and in neurons. We report a striking heterogeneity in the effects of TARP subtypes on AMPAR deactivation and desensitization, which we demonstrate controls the time course of synaptic transmission. In addition, we find that some TARP subtypes dramatically slow AMPAR activation kinetics. Synaptic AMPAR kinetics also depend on TARP expression level, suggesting a variable TARP/AMPAR stoichiometry. Analysis of quantal synaptic transmission in a TARP gamma-4 knockout (KO) mouse corroborates our expression data and demonstrates that TARP subtype-specific gating of AMPARs contributes to the kinetics of native AMPARs at central synapses.

  1. A thermodynamic study of the third PDZ domain of MAGUK neuronal protein PSD-95 reveals a complex three-state folding behavior.

    PubMed

    Murciano-Calles, Javier; Martinez, Jose C; Marin-Argany, Marta; Villegas, Sandra; Cobos, Eva S

    2014-01-01

    The relevance of the C-terminal α helix of the PDZ3 domain of PSD95 in its unfolding process has been explored by achieving the thermodynamic characterization of a construct where the sequence of the nine residues corresponding to such motif has been deleted. Calorimetric traces at neutral pH require the application of a three-state model displaying three different equilibrium processes in which the intermediate state self-associates upon heating, being stable and populated in a wide temperature range. Temperature scans followed by circular dichroism, Fourier transform infrared spectroscopy and dynamic light scattering support the presence of such oligomeric-partially folded species. This study reveals that the deletion of the α3-helix sequence results in a more complex description of the domain unfolding.

  2. Increased Excitatory Synaptic Transmission of Dentate Granule Neurons in Mice Lacking PSD-95-Interacting Adhesion Molecule Neph2/Kirrel3 during the Early Postnatal Period

    PubMed Central

    Roh, Junyeop D.; Choi, Su-Yeon; Cho, Yi Sul; Choi, Tae-Yong; Park, Jong-Sil; Cutforth, Tyler; Chung, Woosuk; Park, Hanwool; Lee, Dongsoo; Kim, Myeong-Heui; Lee, Yeunkum; Mo, Seojung; Rhee, Jeong-Seop; Kim, Hyun; Ko, Jaewon; Choi, Se-Young; Bae, Yong Chul; Shen, Kang; Kim, Eunjoon; Han, Kihoon

    2017-01-01

    Copy number variants and point mutations of NEPH2 (also called KIRREL3) gene encoding an immunoglobulin (Ig) superfamily adhesion molecule have been linked to autism spectrum disorders, intellectual disability and neurocognitive delay associated with Jacobsen syndrome, but the physiological roles of Neph2 in the mammalian brain remain largely unknown. Neph2 is highly expressed in the dentate granule (DG) neurons of the hippocampus and is localized in both dendrites and axons. It was recently shown that Neph2 is required for the formation of mossy fiber filopodia, the axon terminal structure of DG neurons forming synapses with GABAergic neurons of CA3. In contrast, however, it is unknown whether Neph2 also has any roles in the postsynaptic compartments of DG neurons. We here report that, through its C-terminal PDZ domain-binding motif, Neph2 directly interacts with postsynaptic density (PSD)-95, an abundant excitatory postsynaptic scaffolding protein. Moreover, Neph2 protein is detected in the brain PSD fraction and interacts with PSD-95 in synaptosomal lysates. Functionally, loss of Neph2 in mice leads to age-specific defects in the synaptic connectivity of DG neurons. Specifically, Neph2−/− mice show significantly increased spontaneous excitatory synaptic events in DG neurons at postnatal week 2 when the endogenous Neph2 protein expression peaks, but show normal excitatory synaptic transmission at postnatal week 3. The evoked excitatory synaptic transmission and synaptic plasticity of medial perforant pathway (MPP)-DG synapses are also normal in Neph2−/− mice at postnatal week 3, further confirming the age-specific synaptic defects. Together, our results provide some evidence for the postsynaptic function of Neph2 in DG neurons during the early postnatal period, which might be implicated in neurodevelopmental and cognitive disorders caused by NEPH2 mutations. PMID:28381988

  3. N-terminal SAP97 isoforms differentially regulate synaptic structure and postsynaptic surface pools of AMPA receptors.

    PubMed

    Goodman, Lucy; Baddeley, David; Ambroziak, Wojciech; Waites, Clarissa L; Garner, Craig C; Soeller, Christian; Montgomery, Johanna M

    2017-02-28

    The location and density of postsynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors is controlled by scaffolding proteins within the postsynaptic density (PSD). SAP97 is a PSD protein with two N-terminal isoforms, α and β, that have opposing effects on synaptic strength thought to result from differential targeting of AMPA receptors into distinct synaptic versus extrasynaptic locations, respectively. In this study, we have applied dSTORM super resolution imaging in order to localize the synaptic and extrasynaptic pools of AMPA receptors in neurons expressing α or βSAP97. Unexpectedly, we observed that both α and βSAP97 enhanced the localization of AMPA receptors at synapses. However, this occurred via different mechanisms: αSAP97 increased PSD size and consequently the number of receptor binding sites, whilst βSAP97 increased synaptic receptor cluster size and surface AMPA receptor density at the PSD edge and surrounding perisynaptic sites without changing PSD size. αSAP97 also strongly enlarged presynaptic active zone protein clusters, consistent with both presynaptic and postsynaptic enhancement underlying the previously observed αSAP97-induced increase in AMPA receptor-mediated currents. In contrast, βSAP97-expressing neurons increased the proportion of immature filopodia that express higher levels of AMPA receptors, decreased the number of functional presynaptic terminals, and also reduced the size of the dendritic tree and delayed the maturation of mushroom spines. Our data reveal that SAP97 isoforms can specifically regulate surface AMPA receptor nanodomain clusters, with βSAP97 increasing extrasynaptic receptor domains at peri-synaptic and filopodial sites. Moreover, βSAP97 negatively regulates synaptic maturation both structurally and functionally. These data support diverging presynaptic and postsynaptic roles of SAP97 N-terminal isoforms in synapse maturation and plasticity. As numerous splice isoforms exist in

  4. Homeostatic regulation of AMPA receptor trafficking and degradation by light-controlled single synaptic activation

    PubMed Central

    Hou, Qingming; Gilbert, James; Man, Heng-Ye

    2011-01-01

    During homeostatic adjustment in response to alterations in neuronal activity, synaptic expression of AMPA receptors (AMPARs) is globally tuned up- or down so that the neuronal activity is restored to a physiological range. Given that a central neuron receives multiple presynaptic inputs, whether and how AMPAR synaptic expression is homeostatically regulated at individual synapses remains unclear. In cultured hippocampal neurons, we report that when activity of an individual presynaptic terminal is selectively elevated by light-controlled excitation, AMPAR abundance at the excited synapses is selectively down-regulated in an NMDAR-dependent manner. The reduction in surface AMPARs is accompanied by enhanced receptor endocytosis and dependent on proteasomal activity. Synaptic activation also leads to a site-specific increase in the ubiquitin ligase Nedd4 and polyubiquitination levels, consistent with AMPAR ubiquitination and degradation in the spine. These results indicate that AMPAR accumulation at individual synapses is subject to autonomous homeostatic regulation in response to synaptic activity. PMID:22153376

  5. Hippocampal AMPA receptor gating controlled by both TARP and cornichon proteins.

    PubMed

    Kato, Akihiko S; Gill, Martin B; Ho, Michelle T; Yu, Hong; Tu, Yuan; Siuda, Edward R; Wang, He; Qian, Yue-Wei; Nisenbaum, Eric S; Tomita, Susumu; Bredt, David S

    2010-12-22

    Transmembrane AMPA receptor regulatory proteins (TARPs) and cornichon proteins (CNIH-2/3) independently modulate AMPA receptor trafficking and gating. However, the potential for interactions of these subunits within an AMPA receptor complex is unknown. Here, we find that TARPs γ-4, γ-7, and γ-8, but not γ-2, γ-3, or γ-5, cause AMPA receptors to "resensitize" upon continued glutamate application. With γ-8, resensitization occurs with all GluA subunit combinations; however, γ-8-containing hippocampal neurons do not display resensitization. In recombinant systems, CNIH-2 abrogates γ-8-mediated resensitization and modifies AMPA receptor pharmacology and gating to match that of hippocampal neurons. In hippocampus, γ-8 and CNIH-2 associate in postsynaptic densities and CNIH-2 protein levels are markedly diminished in γ-8 knockout mice. Manipulating neuronal CNIH-2 levels modulates the electrophysiological properties of extrasynaptic and synaptic γ-8-containing AMPA receptors. Thus, γ-8 and CNIH-2 functionally interact with common hippocampal AMPA receptor complexes to modulate synergistically kinetics and pharmacology.

  6. Glutamate controls the induction of GABA-mediated giant depolarizing potentials through AMPA receptors in neonatal rat hippocampal slices.

    PubMed

    Bolea, S; Avignone, E; Berretta, N; Sanchez-Andres, J V; Cherubini, E

    1999-05-01

    Glutamate controls the induction of GABA-mediated giant depolarizing potentials through AMPA receptors in neonatal rat hippocampal slices. Giant depolarizing potentials (GDPs) are generated by the interplay of the depolarizing action of GABA and glutamate. In this study, single and dual whole cell recordings (in current-clamp configuration) were performed from CA3 pyramidal cells in hippocampal slices obtained from postnatal (P) days P1- to P6-old rats to evaluate the role of ionotropic glutamate receptors in GDP generation. Superfusion of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (10-40 microM) completely blocked GDPs. However, in the presence of CNQX, it was still possible to re-induce the appearance of GDPs with GABA (20 microM) or (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxadepropionate (AMPA) (5 microM). This effect was prevented by the more potent and selective AMPA receptor antagonist GYKI 53655 (50-100 microM). In the presence of GYKI 53655, both kainic or domoic acid (0.1-1 microM) were unable to induce GDPs. In contrast, bath application of D-(-)-2-amino-5-phosphonopentanoic acid (50 microM) or (+)-3-(2carboxy-piperazin-4-yl)-propyl-L-phosphonic acid (20 microM) produced only a 37 +/- 9% (SE) and 36 +/- 11% reduction in GDPs frequency, respectively. Cyclothiazide, a selective blocker of AMPA receptor desensitization, increased GDP frequency by 76 +/- 14%. Experiments were also performed with an intracellular solution containing KF to block GABAA receptor-mediated responses. In these conditions, a glutamatergic component of GDP was revealed. GDPs could still be recorded synchronous with those detected simultaneously with KCl-filled electrodes, although their amplitude was smaller. Similar results were found in pair recordings obtained from minislices containing only a small portion of the CA3 area. These data suggest that GDP generation requires activation of AMPA receptors by local release of glutamate from recurrent collaterals.

  7. Effects of the AMPA Antagonist ZK 200775 on Visual Function: A Randomized Controlled Trial

    PubMed Central

    Bergholz, Richard; Staks, Thomas; Rüther, Klaus

    2010-01-01

    Background ZK 200775 is an antagonist at the α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor and had earned attention as a possible neuroprotective agent in cerebral ischemia. Probands receiving the agent within phase I trials reported on an alteration of visual perception. In this trial, the effects of ZK 200775 on the visual system were analyzed in detail. Methodology In a randomised controlled trial we examined eyes and vision before and after the intravenous administration of two different doses of ZK 200775 and placebo. There were 3 groups of 6 probands each: Group 1 recieved 0.03 mg/kg/h, group 2 0.75 mg/kg/h of ZK 200775, the control group received 0.9% sodium chloride solution. Probands were healthy males aged between 57 and 69 years. The following methods were applied: clinical examination, visual acuity, ophthalmoscopy, colour vision, rod absolute threshold, central visual field, pattern-reversal visual evoked potentials (pVEP), ON-OFF and full-field electroretinogram (ERG). Principal Findings No effect of ZK 200775 was seen on eye position or motility, stereopsis, pupillary function or central visual field testing. Visual acuity and dark vision deteriorated significantly in both treated groups. Color vision was most remarkably impaired. The dark-adapted ERG revealed a reduction of oscillatory potentials (OP) and partly of the a- and b-wave, furthermore an alteration of b-wave morphology and an insignificantly elevated b/a-ratio. Cone-ERG modalities showed decreased amplitudes and delayed implicit times. In the ON-OFF ERG the ON-answer amplitudes increased whereas the peak times of the OFF-answer were reduced. The pattern VEP exhibited lower amplitudes and prolonged peak times. Conclusions The AMPA receptor blockade led to a strong impairment of typical OFF-pathway functions like color vision and the cone ERG. On the other hand the ON-pathway as measured by dark vision and the scotopic ERG was affected as well. This further elucidates

  8. Ras and Rab interactor 1 controls neuronal plasticity by coordinating dendritic filopodial motility and AMPA receptor turnover

    PubMed Central

    Szíber, Zsófia; Liliom, Hanna; Morales, Carlos O. Oueslati; Ignácz, Attila; Rátkai, Anikó Erika; Ellwanger, Kornelia; Link, Gisela; Szűcs, Attila; Hausser, Angelika; Schlett, Katalin

    2017-01-01

    Ras and Rab interactor 1 (RIN1) is predominantly expressed in the nervous system. RIN1-knockout animals have deficits in latent inhibition and fear extinction in the amygdala, suggesting a critical role for RIN1 in preventing the persistence of unpleasant memories. At the molecular level, RIN1 signals through Rab5 GTPases that control endocytosis of cell-surface receptors and Abl nonreceptor tyrosine kinases that participate in actin cytoskeleton remodeling. Here we report that RIN1 controls the plasticity of cultured mouse hippocampal neurons. Our results show that RIN1 affects the morphology of dendritic protrusions and accelerates dendritic filopodial motility through an Abl kinase–dependent pathway. Lack of RIN1 results in enhanced mEPSC amplitudes, indicating an increase in surface AMPA receptor levels compared with wild-type neurons. We further provide evidence that the Rab5 GEF activity of RIN1 regulates surface GluA1 subunit endocytosis. Consequently loss of RIN1 blocks surface AMPA receptor down-regulation evoked by chemically induced long-term depression. Our findings indicate that RIN1 destabilizes synaptic connections and is a key player in postsynaptic AMPA receptor endocytosis, providing multiple ways of negatively regulating memory stabilization during neuronal plasticity. PMID:27852895

  9. GRIP1 interlinks N-cadherin and AMPA receptors at vesicles to promote combined cargo transport into dendrites

    PubMed Central

    Heisler, Frank F.; Lee, Han Kyu; Gromova, Kira V.; Pechmann, Yvonne; Schurek, Beate; Ruschkies, Laura; Schroeder, Markus; Schweizer, Michaela; Kneussel, Matthias

    2014-01-01

    The GluA2 subunit of AMPA-type glutamate receptors (AMPARs) regulates excitatory synaptic transmission in neurons. In addition, the transsynaptic cell adhesion molecule N-cadherin controls excitatory synapse function and stabilizes dendritic spine structures. At postsynaptic membranes, GluA2 physically binds N-cadherin, underlying spine growth and synaptic modulation. We report that N-cadherin binds to PSD-95/SAP90/DLG/ZO-1 (PDZ) domain 2 of the glutamate receptor interacting protein 1 (GRIP1) through its intracellular C terminus. N-cadherin and GluA2-containing AMPARs are presorted to identical transport vesicles for dendrite delivery, and live imaging reveals cotransport of both proteins. The kinesin KIF5 powers GluA2/N-cadherin codelivery by using GRIP1 as a multilink interface. Notably, GluA2 and N-cadherin use different PDZ domains on GRIP1 to simultaneously bind the transport complex, and interference with either binding motif impairs the turnover of both synaptic cargoes. Depolymerization of microtubules, deletion of the KIF5 motor domain, or specific blockade of AMPAR exocytosis affects delivery of GluA2/N-cadherin vesicles. At the functional level, interference with this cotransport reduces the number of spine protrusions and excitatory synapses. Our data suggest the concept that the multi-PDZ-domain adaptor protein GRIP1 can act as a scaffold at trafficking vesicles in the combined delivery of AMPARs and N-cadherin into dendrites. PMID:24639525

  10. The Impact of Extra-Domain Structures and Post-Translational Modifications in the Folding/Misfolding Behaviour of the Third PDZ Domain of MAGUK Neuronal Protein PSD-95

    PubMed Central

    Cobos, Eva S.; Villegas, Sandra; Martinez, Jose C.

    2014-01-01

    The modulation of binding affinities and specificities by post-translational modifications located out from the binding pocket of the third PDZ domain of PSD-95 (PDZ3) has been reported recently. It is achieved through an intra-domain electrostatic network involving some charged residues in the β2–β3 loop (were a succinimide modification occurs), the α3 helix (an extra-structural element that links the PDZ3 domain with the following SH3 domain in PSD-95, and contains the phosphorylation target Tyr397), and the ligand peptide. Here, we have investigated the main structural and thermodynamic aspects that these structural elements and their related post-translational modifications display in the folding/misfolding pathway of PDZ3 by means of site-directed mutagenesis combined with calorimetry and spectroscopy. We have found that, although all the assayed mutations generate proteins more prone to aggregation than the wild-type PDZ3, those directly affecting the α3 helix, like the E401R substitution or the truncation of the whole α3 helix, increase the population of the DSC-detected intermediate state and the misfolding kinetics, by organizing the supramacromolecular structures at the expense of the two β-sheets present in the PDZ3 fold. However, those mutations affecting the β2–β3 loop, included into the prone-to-aggregation region composed by a single β-sheet comprising β2 to β4 chains, stabilize the trimeric intermediate previously shown in the wild-type PDZ3 and slow-down aggregation, also making it partly reversible. These results strongly suggest that the α3 helix protects to some extent the PDZ3 domain core from misfolding. This might well constitute the first example where an extra-element, intended to link the PDZ3 domain to the following SH3 in PSD-95 and in other members of the MAGUK family, not only regulates the binding abilities of this domain but it also protects PDZ3 from misfolding and aggregation. The influence of the post

  11. Mice lacking the PSD-95–interacting E3 ligase, Dorfin/Rnf19a, display reduced adult neurogenesis, enhanced long-term potentiation, and impaired contextual fear conditioning

    PubMed Central

    Park, Hanwool; Yang, Jinhee; Kim, Ryunhee; Li, Yan; Lee, Yeunkum; Lee, Chungwoo; Park, Jongil; Lee, Dongmin; Kim, Hyun; Kim, Eunjoon

    2015-01-01

    Protein ubiquitination has a significant influence on diverse aspects of neuronal development and function. Dorfin, also known as Rnf19a, is a RING finger E3 ubiquitin ligase implicated in amyotrophic lateral sclerosis and Parkinson’s disease, but its in vivo functions have not been explored. We report here that Dorfin is a novel binding partner of the excitatory postsynaptic scaffolding protein PSD-95. Dorfin-mutant (Dorfin−/−) mice show reduced adult neurogenesis and enhanced long-term potentiation in the hippocampal dentate gyrus, but normal long-term potentiation in the CA1 region. Behaviorally, Dorfin−/− mice show impaired contextual fear conditioning, but normal levels of cued fear conditioning, fear extinction, spatial learning and memory, object recognition memory, spatial working memory, and pattern separation. Using a proteomic approach, we also identify a number of proteins whose ubiquitination levels are decreased in the Dorfin−/− brain. These results suggest that Dorfin may regulate adult neurogenesis, synaptic plasticity, and contextual fear memory. PMID:26553645

  12. Regulation of AMPA receptor surface trafficking and synaptic plasticity by a cognitive enhancer and antidepressant molecule.

    PubMed

    Zhang, H; Etherington, L-A; Hafner, A-S; Belelli, D; Coussen, F; Delagrange, P; Chaouloff, F; Spedding, M; Lambert, J J; Choquet, D; Groc, L

    2013-04-01

    The plasticity of excitatory synapses is an essential brain process involved in cognitive functions, and dysfunctions of such adaptations have been linked to psychiatric disorders such as depression. Although the intracellular cascades that are altered in models of depression and stress-related disorders have been under considerable scrutiny, the molecular interplay between antidepressants and glutamatergic signaling remains elusive. Using a combination of electrophysiological and single nanoparticle tracking approaches, we here report that the cognitive enhancer and antidepressant tianeptine (S 1574, [3-chloro-6-methyl-5,5-dioxo-6,11-dihydro-(c,f)-dibenzo-(1,2-thiazepine)-11-yl) amino]-7 heptanoic acid, sodium salt) favors synaptic plasticity in hippocampal neurons both under basal conditions and after acute stress. Strikingly, tianeptine rapidly reduces the surface diffusion of AMPA receptor (AMPAR) through a Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent mechanism that enhances the binding of AMPAR auxiliary subunit stargazin with PSD-95. This prevents corticosterone-induced AMPAR surface dispersal and restores long-term potentiation of acutely stressed mice. Collectively, these data provide the first evidence that a therapeutically used drug targets the surface diffusion of AMPAR through a CaMKII-stargazin-PSD-95 pathway, to promote long-term synaptic plasticity.

  13. Delayed reduction in hippocampal post-synaptic density protein-95 expression temporally correlates with cognitive dysfunction following controlled cortical impact in mice

    PubMed Central

    Wakade, Chandramohan; Sangeetha, S.R.; Laird, Melissa D.; Dhandapani, Krishnan M.; Vender, John R.

    2011-01-01

    Objective Traumatic brain injury (TBI) induces significant neurological damage, including deficits in learning and memory which contribute to a poor clinical prognosis. Treatment options to limit cognitive decline and promote neurological recovery are lacking, in part, due to a poor understanding of the secondary/delayed processes which contribute to brain injury. In the present study, we characterized the temporal and spatial changes in the expression of PSD-95, a key scaffolding protein implicated in excitatory synaptic signaling, following controlled cortical impact in mice. Neurological injury, as assessed by the open field activity test and the novel object recognition test, were compared with changes in PSD-95 expression. Methods Adult male CD-1 mice were subjected to controlled cortical impact to simulate a moderate traumatic brain injury in humans. The spatial and temporal expression of PSD-95 was analyzed in the cerebral cortex and hippocampus at various time points following injury. Neurological assessments were performed to compare changes in PSD-95 with cognitive deficits. Results A significant decrease in PSD-95 expression was observed in the ipsilateral hippocampus beginning at day 7 post-injury. The loss of PSD-95 corresponded with a concomitant reduction in immunoreactivity for NeuN, a neuronal-specific marker. Aside from the contused cortex, significant loss of PSD-95 immunoreactivity was not observed in the cerebral cortex. The delayed loss of hippocampal PSD-95 directly correlated with the onset of behavioral deficits, suggesting a possible causative role for PSD-95 in behavioral abnormalities following a head trauma. Conclusion Delayed loss of hippocampal synapses was observed following head trauma in mice. These data may suggest a cellular mechanism to explain the delayed learning and memory deficits in humans and provide a potential framework for further testing to implicate PSD-95 as a clinically-relevant therapeutic target. PMID:20397893

  14. Stress- and mitogen-induced phosphorylation of the synapse-associated protein SAP90/PSD-95 by activation of SAPK3/p38gamma and ERK1/ERK2.

    PubMed Central

    Sabio, Guadalupe; Reuver, Suzana; Feijoo, Carmen; Hasegawa, Masato; Thomas, Gareth M; Centeno, Francisco; Kuhlendahl, Sven; Leal-Ortiz, Sergio; Goedert, Michel; Garner, Craig; Cuenda, Ana

    2004-01-01

    SAPK3 (stress-activated protein kinase-3, also known as p38gamma) is a member of the mitogen-activated protein kinase family; it phosphorylates substrates in response to cellular stress, and has been shown to bind through its C-terminal sequence to the PDZ domain of alpha1-syntrophin. In the present study, we show that SAP90 [(synapse-associated protein 90; also known as PSD-95 (postsynaptic density-95)] is a novel physiological substrate for both SAPK3/p38gamma and the ERK (extracellular-signal-regulated protein kinase). SAPK3/p38gamma binds preferentially to the third PDZ domain of SAP90 and phosphorylates residues Thr287 and Ser290 in vitro, and Ser290 in cells in response to cellular stresses. Phosphorylation of SAP90 is dependent on the binding of SAPK3/p38gamma to the PDZ domain of SAP90. It is not blocked by SB 203580, which inhibits SAPK2a/p38alpha and SAPK2b/p38beta but not SAPK3/p38gamma, or by the ERK pathway inhibitor PD 184352. However, phosphorylation is abolished when cells are treated with a cell-permeant Tat fusion peptide that disrupts the interaction of SAPK3/p38gamma with SAP90. ERK2 also phosphorylates SAP90 at Thr287 and Ser290 in vitro, but this does not require PDZ-dependent binding. SAP90 also becomes phosphorylated in response to mitogens, and this phosphorylation is prevented by pretreatment of the cells with PD 184352, but not with SB 203580. In neurons, SAP90 and SAPK3/p38gamma co-localize and they are co-immunoprecipitated from brain synaptic junctional preparations. These results demonstrate that SAP90 is a novel binding partner for SAPK3/p38gamma, a first physiological substrate described for SAPK3/p38gamma and a novel substrate for ERK1/ERK2, and that phosphorylation of SAP90 may play a role in regulating protein-protein interactions at the synapse in response to adverse stress- or mitogen-related stimuli. PMID:14741046

  15. AMPA Receptors as Therapeutic Targets for Neurological Disorders.

    PubMed

    Lee, Kevin; Goodman, Lucy; Fourie, Chantelle; Schenk, Susan; Leitch, Beulah; Montgomery, Johanna M

    2016-01-01

    Almost every neurological disease directly or indirectly affects synapse function in the brain. However, these diseases alter synapses through different mechanisms, ultimately resulting in altered synaptic transmission and/or plasticity. Glutamate is the major neurotransmitter that mediates excitatory synaptic transmission in the brain through activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptors. These receptors have therefore been identified as a target for the development of therapeutic treatments for neurological disorders including epilepsy, neurodegenerative diseases, autism, and drug addiction. The fact that AMPA receptors play a dominant role throughout the brain raises the significant challenge of selectively targeting only those regions affected by disease, and clinical trials have raised doubt regarding the feasibility of specifically targeting AMPA receptors for new therapeutic options. Benzamide compounds that act as positive allosteric AMPA receptor modulators, known as AMPAkines, can act on specific brain regions and were initially proposed to revolutionize the treatment of cognitive deficits associated with neurological disorders. Their therapeutic potential has since declined due to inconsistent results in clinical trials. However, recent advances in basic biomedical research are significantly increasing our knowledge of AMPA receptor structure, binding sites, and interactions with auxiliary proteins. In particular, the large complex of postsynaptic proteins that interact with AMPA receptor subunits have been shown to control AMPA receptor insertion, location, pharmacology, synaptic transmission, and plasticity. These proteins are now being considered as alternative therapeutic target sites for modulating AMPA receptors in neurological disorders.

  16. Development- and age-related alterations in the expression of AMPA receptor subunit GluR2 and its trafficking proteins in the hippocampus of male mouse brain.

    PubMed

    Pandey, Surya P; Rai, Rakesh; Gaur, Pankaj; Prasad, S

    2015-06-01

    AMPA type glutamate receptor (AMPAR) on the post synaptic membrane plays important role in the process of synaptic plasticity involving various scaffolding and trafficking proteins. However, their alterations during development- and aging are not well understood. Here, we report that the expression of AMPAR-GluR2 subunit is gradually up regulated in the hippocampus from 0 day to adult (20 week) and down regulated thereafter in 70 week old male mice. This pattern of GluR2 during development (0-, 7- and 15 day), maturation (45 day) and adult age resembles with similar expression pattern of the scaffolding protein PSD95. Expression pattern of Stargazin (TARPγ-2) largely follows almost similar pattern up to adult age but is up regulated in old age. Pattern of PICK1 expression, however, is opposite to our GluR2 data till adult age but its expression is significantly down regulated in old age. Our data on alterations in the expression of GluR2 in the hippocampus during development and aging indicates a high- and low positive correlations with PSD95 and Stargazin, respectively whereas negative correlation with PICK1 except in old age where expression of Stargazin is higher and that of PICK1 is lower. Our findings suggest that increasing expression pattern of GluR2 during developmental periods and at adult age may be associated with achieving cognitive abilities whereas its low expression in old age may be linked with cognitive decline and proteins like PSD95, Stargazin and PICK1 might be differentially associated with development- and age-dependent alterations in AMPAR-dependent synaptic plasticity and hence learning and memory.

  17. Postsynaptic density-95 mimics and occludes hippocampal long-term potentiation and enhances long-term depression.

    PubMed

    Stein, Valentin; House, David R C; Bredt, David S; Nicoll, Roger A

    2003-07-02

    Previous studies have shown that overexpression of the protein PSD-95 (postsynaptic density-95) selectively enhances AMPA receptor-mediated synaptic responses in hippocampal pyramidal cells. To determine whether this effect is related to synaptic plasticity at these synapses, we examined whether PSD-95 expression mimics long-term potentiation (LTP), and also whether it influences LTP and long-term depression (LTD) in hippocampal slice cultures. Using simultaneous recording from transfected or infected cells and control pyramidal cells, we found that PSD-95, similar to LTP, increases the amplitude and frequency of miniature EPSCs. It also converts silent synapses to functional synapses, as does LTP. In addition, LTP is completely occluded in cells expressing PSD-95, whereas LTD is greatly enhanced. These results suggest that common mechanisms are involved in controlling synaptic AMPA receptors by PSD-95 and synaptic plasticity.

  18. GluA2-Containing AMPA Receptors Distinguish Ribbon-Associated from Ribbonless Afferent Contacts on Rat Cochlear Hair Cells123

    PubMed Central

    Martinez-Monedero, Rodrigo

    2016-01-01

    Abstract Mechanosensory hair cells release glutamate at ribbon synapses to excite postsynaptic afferent neurons, via AMPA-type ionotropic glutamate receptors (AMPARs). However, type II afferent neurons contacting outer hair cells in the mammalian cochlea were thought to differ in this respect, failing to show GluA immunolabeling and with many “ribbonless” afferent contacts. Here it is shown that antibodies to the AMPAR subunit GluA2 labeled afferent contacts below inner and outer hair cells in the rat cochlea, and that synaptic currents in type II afferents had AMPAR-specific pharmacology. Only half the postsynaptic densities of type II afferents that labeled for PSD-95, Shank, or Homer were associated with GluA2 immunopuncta or presynaptic ribbons, the “empty slots” corresponding to ribbonless contacts described previously. These results extend the universality of AMPAergic transmission by hair cells, and support the existence of silent afferent contacts. PMID:27257620

  19. Superactivation of AMPA receptors by auxiliary proteins

    PubMed Central

    Carbone, Anna L.; Plested, Andrew J. R.

    2016-01-01

    Glutamate receptors form complexes in the brain with auxiliary proteins, which control their activity during fast synaptic transmission through a seemingly bewildering array of effects. Here we devise a way to isolate the activation of complexes using polyamines, which enables us to show that transmembrane AMPA receptor regulatory proteins (TARPs) exert their effects principally on the channel opening reaction. A thermodynamic argument suggests that because TARPs promote channel opening, receptor activation promotes AMPAR-TARP complexes into a superactive state with high open probability. A simple model based on this idea predicts all known effects of TARPs on AMPA receptor function. This model also predicts unexpected phenomena including massive potentiation in the absence of desensitization and supramaximal recovery that we subsequently detected in electrophysiological recordings. This transient positive feedback mechanism has implications for information processing in the brain, because it should allow activity-dependent facilitation of excitatory synaptic transmission through a postsynaptic mechanism. PMID:26744192

  20. AMPA experimental communications systems

    NASA Technical Reports Server (NTRS)

    Beckerman, D.; Fass, S.; Keon, T.; Sielman, P.

    1982-01-01

    The program was conducted to demonstrate the satellite communication advantages of Adaptive Phased Array Technology. A laboratory based experiment was designed and implemented to demonstrate a low earth orbit satellite communications system. Using a 32 element, L-band phased array augmented with 4 sets of weights (2 for reception and 2 for transmission) a high speed digital processing system and operating against multiple user terminals and interferers, the AMPA system demonstrated: communications with austere user terminals, frequency reuse, communications in the face of interference, and geolocation. The program and experiment objectives are described, the system hardware and software/firmware are defined, and the test performed and the resultant test data are presented.

  1. Shisa6 traps AMPA receptors at postsynaptic sites and prevents their desensitization during synaptic activity

    PubMed Central

    Klaassen, Remco V.; Stroeder, Jasper; Coussen, Françoise; Hafner, Anne-Sophie; Petersen, Jennifer D.; Renancio, Cedric; Schmitz, Leanne J. M.; Normand, Elisabeth; Lodder, Johannes C.; Rotaru, Diana C.; Rao-Ruiz, Priyanka; Spijker, Sabine; Mansvelder, Huibert D.; Choquet, Daniel; Smit, August B.

    2016-01-01

    Trafficking and biophysical properties of AMPA receptors (AMPARs) in the brain depend on interactions with associated proteins. We identify Shisa6, a single transmembrane protein, as a stable and directly interacting bona fide AMPAR auxiliary subunit. Shisa6 is enriched at hippocampal postsynaptic membranes and co-localizes with AMPARs. The Shisa6 C-terminus harbours a PDZ domain ligand that binds to PSD-95, constraining mobility of AMPARs in the plasma membrane and confining them to postsynaptic densities. Shisa6 expressed in HEK293 cells alters GluA1- and GluA2-mediated currents by prolonging decay times and decreasing the extent of AMPAR desensitization, while slowing the rate of recovery from desensitization. Using gene deletion, we show that Shisa6 increases rise and decay times of hippocampal CA1 miniature excitatory postsynaptic currents (mEPSCs). Shisa6-containing AMPARs show prominent sustained currents, indicating protection from full desensitization. Accordingly, Shisa6 prevents synaptically trapped AMPARs from depression at high-frequency synaptic transmission. PMID:26931375

  2. Lamina-specific abnormalities of AMPA receptor trafficking and signaling molecule transcripts in the prefrontal cortex in schizophrenia.

    PubMed

    Beneyto, Monica; Meador-Woodruff, James H

    2006-12-15

    Ampakines, positive AMPA receptor modulators, can improve cognitive function in schizophrenia, and enhancement of AMPA receptor-mediated currents by them potentiates the activity of antipsychotics. In vitro studies have revealed that trafficking of AMPA receptors is mediated by specific interactions of a complex network of proteins that also target and anchor them at the postsynaptic density (PSD). The aim of this study was to determine whether there are abnormalities of the molecules associated with trafficking and localization of AMPA receptors at the PSD in the dorsolateral prefrontal cortex (DLPFC) in schizophrenia. We analyzed AMPA receptor expression in DLPFC in schizophrenia, major depression, bipolar disorder, and a control group, by examining transcript levels of all four AMPA receptor subunits by in situ hybridization. We found decreased GluR2 subunit expression in all three illnesses, decreased GluR3 in major depression, and decreased GluR4 in schizophrenia. However, autoradiography experiments showed no changes in AMPA receptor binding; thus, we hypothesized that these changes in receptor subunit stoichiometry do not alter binding to the assembled receptor, but rather intracellular processing. In situ hybridization for AMPA-trafficking molecules showed decreased expression of PICK1 and increased expression of stargazin in DLPFC in schizophrenia, both restricted to large cells of cortical layer III. These data suggest that AMPA-mediated glutamatergic neurotransmission is compromised in schizophrenia, particularly at the level of AMPA-related PSD proteins that mediate AMPA receptor trafficking, synaptic surface expression, and intracellular signaling.

  3. Gestational nicotine exposure regulates expression of AMPA and NMDA receptors and their signaling apparatus in developing and adult rat hippocampus

    PubMed Central

    Wang, Hong; Dávila-García, Martha I.; Yarl, Weonpo; Gondré-Lewis, Marjorie C.

    2011-01-01

    Untimely activation of nicotinic acetylcholine receptor (nAChR) by nicotine results in short- and long-term consequences on learning and behavior. In this study, the aim was to determine how prenatal nicotine exposure affects components of glutamatergic signaling in the hippocampus during postnatal development. We investigated regulation of both nAChRs and glutamate receptors for α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and N-methyl-D-aspartate (NMDA), from postnatal day (P) 1 to P63 after a temporally restricted exposure to saline or nicotine for 14 days in utero. We analyzed postsynaptic density components associated with AMPAR and NMDAR signaling: Calcium/calmodulin-dependent protein kinase II α (CaMKIIα), Calmodulin (CaM), and postsynaptic density-95 (PSD95), as well as presynaptically localized synaptosomal-associated protein 25 (SNAP25). At P1, there was significantly heightened expression of AMPAR subunit GluR1 but not GluR2, and of NMDAR subunits NR1, NR2a and NR2d but not NR2b. NR2c was not detectable. At P1, the postsynaptic proteins CaMKIIα, CaM, and PSD95 were also significantly upregulated, together with presynaptic SNAP25. This enhanced expression of glutamate receptors and signaling proteins was concomitant with elevated levels of [3H] Epibatidine (EB) binding in prenatal nicotine-exposed hippocampus, indicating that α4β2 nAChR may influence glutamatergic function in the hippocampus at P1. By P14, neither [3H]EB binding nor the expression levels of subunits GluR1, GluR2, NR1, NR2a, NR2b, NR2c, or NR2d seemed changed with prenatal nicotine. However, CaMKIIα was significantly upregulated with nicotine treatment while CaM showed downregulation at P14. The effects of nicotine persisted in young adult brains at P63. They exhibited significantly downregulated GluR2, NR1, and NR2c expression levels in hippocampal homogenates and a considerably muted overall distribution of [3H]AMPA binding in areas CA1, CA2, CA3, and the dentate

  4. Recycling Endosomes Supply AMPA Receptors for LTP

    NASA Astrophysics Data System (ADS)

    Park, Mikyoung; Penick, Esther C.; Edwards, Jeffrey G.; Kauer, Julie A.; Ehlers, Michael D.

    2004-09-01

    Long-term potentiation (LTP) of synaptic strength, the most established cellular model of information storage in the brain, is expressed by an increase in the number of postsynaptic AMPA receptors. However, the source of AMPA receptors mobilized during LTP is unknown. We report that AMPA receptors are transported from recycling endosomes to the plasma membrane for LTP. Stimuli that triggered LTP promoted not only AMPA receptor insertion but also generalized recycling of cargo and membrane from endocytic compartments. Thus, recycling endosomes supply AMPA receptors for LTP and provide a mechanistic link between synaptic potentiation and membrane remodeling during synapse modification.

  5. Electrophysiological properties of AMPA receptors are differentially modulated depending on the associated member of the TARP family.

    PubMed

    Kott, Sabine; Werner, Markus; Körber, Christoph; Hollmann, Michael

    2007-04-04

    The family of AMPA receptors is encoded by four genes that are differentially spliced to result in the flip or flop versions of the four subunits GluR1 to GluR4. GluR2 is further modified at the so-called Q/R site by posttranscriptional RNA editing. Delivery of AMPA receptors to the plasma membrane and synaptic trafficking are controlled by transmembrane AMPA receptor regulatory proteins (TARPs). Additionally, TARPs influence essential electrophysiological properties of AMPA receptor channels such as desensitization and agonist efficacies. Here, we compare the influence of all known TARPs (gamma2, gamma3, gamma4, and gamma8) on agonist-induced currents of the four AMPA receptor subunits, including flip and flop splice variants and editing variants. We show that, although agonist-induced currents of all homomeric AMPA receptor subunits as well as all heteromeric combinations tested are significantly potentiated when coexpressed with members of the TARP family in Xenopus laevis oocytes, the extent of TARP-mediated increase in agonist-induced responses is highly dependent on both the AMPA receptor subunit and the coexpressed TARP. Moreover, we demonstrate that the splice variant of the AMPA receptor plays a key role in determining the modulation of electrophysiological properties by associated TARPs. We furthermore present evidence that individual TARP-AMPA receptor interactions control the degree of desensitization of AMPA receptors. Consequently, because of their subunit-specific impact on the electrophysiological properties, TARPs play a major role as modulatory subunits of AMPA receptors and thus contribute to the functional diversity of AMPA receptors encountered in the CNS.

  6. Fate and availability of glyphosate and AMPA in agricultural soil.

    PubMed

    Simonsen, Louise; Fomsgaard, Inge S; Svensmark, Bo; Spliid, Niels Henrik

    2008-06-01

    The fate of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) was studied in soil. Labeled glyphosate was used to be able to distinguish the measured quantities of glyphosate and AMPA from the background values since the soil was sampled in a field where glyphosate had been used formerly. After addition of labeled glyphosate, the disappearance of glyphosate and the formation and disappearance of AMPA were monitored. The resulting curves were fitted according to a new EU guideline. The best fit of the glyphosate degradation data was obtained using a first-order multi compartment (FOMC) model. DT(50) values of 9 days (glyphosate) and 32 days (AMPA) indicated relatively rapid degradation. After an aging period of 6 months, the leaching risk of each residue was determined by treating the soil with pure water or a phosphate solution (pH 6), to simulate rain over a non-fertilized or fertilized field, respectively. Significantly larger (p < 0.05) amounts of aged glyphosate and AMPA were extracted from the soil when phosphate solution was used as an extraction agent, compared with pure water. This indicates that the risk of leaching of aged glyphosate and AMPA residues from soil is greater in fertilized soil. The blank soil, to which 252 g glyphosate/ha was applied 21 months before this study, contained 0.81 ng glyphosate/g dry soil and 10.46 ng AMPA/g dry soil at the start of the study. Blank soil samples were used as controls without glyphosate addition. After incubation of the blank soil samples for 6 months, a significantly larger amount of AMPA was extracted from the soil treated with phosphate solution than from that treated with pure water. To determine the degree of uptake of aged glyphosate residues by crops growing in the soil, (14)C-labeled glyphosate was applied to soil 6.5 months prior to sowing rape and barley seeds. After 41 days, 0.006 +/- 0.002% and 0.005 +/- 0.001% of the applied radioactivity was measured in rape and barley

  7. Urban contributions of glyphosate and its degradate AMPA to streams in the United States

    USGS Publications Warehouse

    Kolpin, D.W.; Thurman, E.M.; Lee, E.A.; Meyer, M.T.; Furlong, E.T.; Glassmeyer, S.T.

    2006-01-01

    Glyphosate is the most widely used herbicide in the world, being routinely applied to control weeds in both agricultural and urban settings. Microbial degradation of glyphosate produces aminomethyl phosphonic acid (AMPA). The high polarity and water-solubility of glyphosate and AMPA has, until recently, made their analysis in water samples problematic. Thus, compared to other herbicides (e.g. atrazine) there are relatively few studies on the environmental occurrence of glyphosate and AMPA. In 2002, treated effluent samples were collected from 10 wastewater treatment plants (WWTPs) to study the occurrence of glyphosate and AMPA. Stream samples were collected upstream and downstream of the 10 WWTPs. Two reference streams were also sampled. The results document the apparent contribution of WWTP effluent to stream concentrations of glyphosate and AMPA, with roughly a two-fold increase in their frequencies of detection between stream samples collected upstream and those collected downstream of the WWTPs. Thus, urban use of glyphosate contributes to glyphosate and AMPA concentrations in streams in the United States. Overall, AMPA was detected much more frequently (67.5%) compared to glyphosate (17.5%).

  8. Toxicity of AMPA to the earthworm Eisenia andrei Bouché, 1972 in tropical artificial soil

    PubMed Central

    Domínguez, Anahí; Brown, George Gardner; Sautter, Klaus Dieter; Ribas de Oliveira, Cintia Mara; de Vasconcelos, Eliane Carvalho; Niva, Cintia Carla; Bartz, Marie Luise Carolina; Bedano, José Camilo

    2016-01-01

    Aminomethylphosphonic acid (AMPA) - one of glyphosate’s main metabolites - has been classified as persistent in soils, raising concern regarding the widespread use of glyphosate in agriculture and forestry. Glyphosate may have negative or neutral effects on soil biota, but no information is available on the toxicity of AMPA to soil invertebrates. Therefore our aim was to study the effect of AMPA on mortality and reproduction of the earthworm species Eisenia andrei using standard soil ecotoxicological methods (ISO). Field-relevant concentrations of AMPA had no significant effects on mortality in acute or chronic assays. Except at the highest concentration tested, a significant biomass loss was observed compared to controls in the chronic assay. The number of juveniles and cocoons increased with higher concentrations of AMPA applied, but their mean weights decreased. This mass loss indicates higher sensitivity of juveniles than adults to AMPA. Our results suggest that earthworms coming from parents grown in contaminated soils may have reduced growth, limiting their beneficial roles in key soil ecosystem functions. Nevertheless, further research is needed to better understand the mechanisms underlying the sublethal effects observed here. PMID:26792548

  9. Toxicity of AMPA to the earthworm Eisenia andrei Bouché, 1972 in tropical artificial soil

    NASA Astrophysics Data System (ADS)

    Domínguez, Anahí; Brown, George Gardner; Sautter, Klaus Dieter; Ribas de Oliveira, Cintia Mara; de Vasconcelos, Eliane Carvalho; Niva, Cintia Carla; Bartz, Marie Luise Carolina; Bedano, José Camilo

    2016-01-01

    Aminomethylphosphonic acid (AMPA) - one of glyphosate’s main metabolites - has been classified as persistent in soils, raising concern regarding the widespread use of glyphosate in agriculture and forestry. Glyphosate may have negative or neutral effects on soil biota, but no information is available on the toxicity of AMPA to soil invertebrates. Therefore our aim was to study the effect of AMPA on mortality and reproduction of the earthworm species Eisenia andrei using standard soil ecotoxicological methods (ISO). Field-relevant concentrations of AMPA had no significant effects on mortality in acute or chronic assays. Except at the highest concentration tested, a significant biomass loss was observed compared to controls in the chronic assay. The number of juveniles and cocoons increased with higher concentrations of AMPA applied, but their mean weights decreased. This mass loss indicates higher sensitivity of juveniles than adults to AMPA. Our results suggest that earthworms coming from parents grown in contaminated soils may have reduced growth, limiting their beneficial roles in key soil ecosystem functions. Nevertheless, further research is needed to better understand the mechanisms underlying the sublethal effects observed here.

  10. Activity-Dependent Palmitoylation Controls SynDIG1 Stability, Localization, and Function

    PubMed Central

    Kaur, Inderpreet; Yarov-Yarovoy, Vladimir; Kirk, Lyndsey M.; Plambeck, Kristopher E.; Barragan, Eden V.; Ontiveros, Eric S.

    2016-01-01

    Synapses are specialized contacts between neurons. Synapse differentiation-induced gene I (SynDIG1) plays a critical role during synapse development to regulate AMPA receptor (AMPAR) and PSD-95 content at excitatory synapses. Palmitoylation regulates the localization and function of many synaptic proteins, including AMPARs and PSD-95. Here we show that SynDIG1 is palmitoylated, and investigate the effects of palmitoylation on SynDIG1 stability and localization. Structural modeling of SynDIG1 suggests that the membrane-associated region forms a three-helical bundle with two cysteine residues located at positions 191 and 192 in the juxta-transmembrane region exposed to the cytoplasm. Site-directed mutagenesis reveals that C191 and C192 are palmitoylated in heterologous cells and positively regulates dendritic targeting in neurons. Like PSD-95, activity blockade in a rat hippocampal slice culture increases SynDIG1 palmitoylation, which is consistent with our prior demonstration that SynDIG1 localization at synapses increases upon activity blockade. These data demonstrate that palmitoylation of SynDIG1 is regulated by neuronal activity, and plays a critical role in regulating its stability and subcellular localization, and thereby its function. SIGNIFICANCE STATEMENT Palmitoylation is a reversible post-translation modification that has recently been recognized as playing a critical role in the localization and function of many synaptic proteins. Here we show that activity-dependent palmitoylation of the atypical AMPA receptor auxiliary transmembrane protein SynDIG1 regulates its stability and localization at synapses to regulate function and synaptic strength. PMID:27445135

  11. AMPA-silent synapses in brain development and pathology.

    PubMed

    Hanse, Eric; Seth, Henrik; Riebe, Ilse

    2013-12-01

    Synapses are constantly generated at a high rate in the developing, prepubescent brain. Newly generated glutamatergic synapses lack functional AMPA receptor-mediated transmission. Most of these 'AMPA-silent' synapses are eliminated during the developmental period, but some are specifically selected for AMPA unsilencing by correlated pre-and postsynaptic activity as the first step in a process that leads to stabilization of the synapse. Premature, or delayed, unsilencing of AMPA-silent synapses has been implicated in neurodevelopmental disorders, and abnormal generation of AMPA-silent synapses is associated with brain trauma, addiction and neurodegenerative disorders, further highlighting the importance of AMPA-silent synapses in brain pathology.

  12. Impaired motor learning attributed to altered AMPA receptor function in the cerebellum of rats with temporal lobe epilepsy: ameliorating effects of Withania somnifera and withanolide A.

    PubMed

    Soman, Smijin; Anju, T R; Jayanarayanan, S; Antony, Sherin; Paulose, C S

    2013-06-01

    The aim of this study was to investigate the effect of Withania somnifera (WS) extract, withanolide A (WA), and carbamazepine (CBZ) on cerebellar AMPA receptor function in pilocarpine-induced temporal lobe epilepsy (TLE). In the present study, motor learning deficit was studied by rotarod test, grid walk test, and narrow beam test. Motor learning was significantly impaired in rats with epilepsy. The treatment with WS and WA significantly reversed the motor learning deficit in rats with epilepsy when compared with control rats. There was an increase in glutamate content and IP3 content observed in rats with epilepsy which was reversed in WS- and WA-treated rats with epilepsy. alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor dysfunction was analyzed using radiolabeled AMPA receptor binding assay, AMPA receptor mRNA expression, and immunohistochemistry using anti-AMPA receptor antibody. Our results suggest that there was a decrease in Bmax, mRNA expression, and AMPA receptor expression indicating AMPA receptor dysfunction, which is suggested to have contributed to the motor learning deficit observed in rats with epilepsy. Moreover, treatment with WS and WA resulted in physiological expression of AMPA receptors. There was also alteration in GAD and GLAST expression which supplemented the increase in extracellular glutamate. The treatment with WS and WA reversed the GAD and GLAST expression. These findings suggest that WS and WA regulate AMPA receptor function in the cerebellum of rats with TLE, which has therapeutic application in epilepsy.

  13. Quantitative Analysis of the Feedback of the Robust Signaling Pathway Network of Myosin V Molecular Motors on GluR1 of AMPA in Neurons: A Networking Approach for Controlling Nanobiomachines

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Qin; Nakano, Tadashi

    Acting as nanobiomachines within the cell, myosin V molecular motors contribute greatly to the LTP (Long Term Potentiation) in neural signaling, which transport the recycling endosomes from the dendrite to the spine of neurons and the GluR1 in AMPA receptors lead to the activities of memorization in brains. However it is unknown that how the restriction of GluR1 at the spine of neuron is caused by the signaling cascade of myosin V and Rab11/Rab11-FIP2 during the myosin V centered signaling process in neurons. Here we report that the feedback of the biochemical reaction for binding Myosin V and Rab11/Rab11-FIP2 plays a pivotal role to restrict the accumulation of GluR1 at the spine. We have investigated the feedback of myosin V and Rab11/Rab11-FIP2 on the convergence of GluR1 by using the computational model of intracellular signaling pathway networks we designed and the simulation software Cell Illustrator Professional Version 3.0 ®. The obtained results show that controllability of molecular motor based nanobiomachines is inevitable for exploring the molecular mechanism of neuroscience at the nanoscale.

  14. Exendin-4 promotes the membrane trafficking of the AMPA receptor GluR1 subunit and ADAM10 in the mouse neocortex.

    PubMed

    Ohtake, Nobuaki; Saito, Mieko; Eto, Masaaki; Seki, Kenjiro

    2014-05-01

    Glucagon-like peptide-1 (GLP-1) is a novel treatment modality for type 2 diabetes mellitus. However, GLP-1 has been suggested as a therapeutic target for Alzheimer's disease (AD). In rodent studies, GLP-1 reduces amyloid beta (Aβ) and facilitates synaptic plasticity. Therefore, in the present study, we investigated how GLP-1 facilitates synaptic plasticity and reduces the Aβ in vivo. Exendin-4, a GLP-1 receptor agonist that can cross the blood brain barrier, was subcutaneously administered to adult mice. We then extracted the total and the plasma membrane proteins from the mouse neocortex. Exendin-4 significantly increased the phosphorylation level of cAMP response element-binding protein (CREB). Consistently, the expression level of brain-derived neurotrophic factor (BDNF), a transcriptional target of CREB, was increased. Furthermore, exendin-4 increased the membrane protein level of the AMPA receptor GluR1 subunit and postsynaptic density protein-95 (PSD-95), whereas GluR2 was unaffected. These exendin-4-dependent increases in membrane GluR1, total PSD-95 and BDNF were abrogated by pretreatment with temozolomide (TMZ), a DNA-alkylating agent, indicating that these alterations were dependent on exendin-4-induced transcriptional activity. In addition, we found that exendin-4 increased the level of the α-C terminal fragment (α-CTF) of amyloid precursor protein (APP). Furthermore, protein levels of both mature and immature ADAM10, the α-secretase of APP in the plasma membrane, were increased, whereas the total mature and immature ADAM10 levels were unchanged. These exendin-4-dependent increases in α-CTF and ADAM10 were not affected by TMZ. These findings suggested that GLP-1 facilitates the GluR1 membrane insertion through CREB activation and increases α-secretase activity through ADAM10 membrane trafficking. Upregulation of GluR1 and ADAM10 at the plasma membrane were also observed in mice with intracerebroventricular administration of Aβ oligomer

  15. NASA Adaptive Multibeam Phased Array (AMPA): An application study

    NASA Technical Reports Server (NTRS)

    Mittra, R.; Lee, S. W.; Gee, W.

    1982-01-01

    The proposed orbital geometry for the adaptive multibeam phased array (AMPA) communication system is reviewed and some of the system's capabilities and preliminary specifications are highlighted. Typical AMPA user link models and calculations are presented, the principal AMPA features are described, and the implementation of the system is demonstrated. System tradeoffs and requirements are discussed. Recommendations are included.

  16. AMPA receptor inhibition by synaptically released zinc

    PubMed Central

    Kalappa, Bopanna I.; Anderson, Charles T.; Lippard, Stephen J.; Tzounopoulos, Thanos

    2015-01-01

    The vast amount of fast excitatory neurotransmission in the mammalian central nervous system is mediated by AMPA-subtype glutamate receptors (AMPARs). As a result, AMPAR-mediated synaptic transmission is implicated in nearly all aspects of brain development, function, and plasticity. Despite the central role of AMPARs in neurobiology, the fine-tuning of synaptic AMPA responses by endogenous modulators remains poorly understood. Here we provide evidence that endogenous zinc, released by single presynaptic action potentials, inhibits synaptic AMPA currents in the dorsal cochlear nucleus (DCN) and hippocampus. Exposure to loud sound reduces presynaptic zinc levels in the DCN and abolishes zinc inhibition, implicating zinc in experience-dependent AMPAR synaptic plasticity. Our results establish zinc as an activity-dependent, endogenous modulator of AMPARs that tunes fast excitatory neurotransmission and plasticity in glutamatergic synapses. PMID:26647187

  17. S-palmitoylation regulates AMPA receptors trafficking and function: a novel insight into synaptic regulation and therapeutics

    PubMed Central

    Han, Jun; Wu, Pengfei; Wang, Fang; Chen, Jianguo

    2014-01-01

    Glutamate acting on AMPA-type ionotropic glutamate receptor (AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translational modifications is one of the key elements that allow the nervous system to adapt to environment stimulations. S-palmitoylation, an important lipid modification by post-translational addition of a long-chain fatty acid to a cysteine residue, regulates AMPA receptor trafficking, which dynamically affects multiple fundamental brain functions, such as learning and memory. In vivo, S-palmitoylation is controlled by palmitoyl acyl transferases and palmitoyl thioesterases. In this review, we highlight advances in the mechanisms for dynamic AMPA receptors palmitoylation, and discuss how palmitoylation affects AMPA receptors function at synapses in recent years. Pharmacological regulation of S-palmitoylation may serve as a novel therapeutic strategy for neurobiological diseases. PMID:26579419

  18. Mechanism-based design of 2,3-benzodiazepine inhibitors for AMPA receptors

    PubMed Central

    Niu, Li

    2015-01-01

    2,3-Benzodiazepine (2,3-BDZ) compounds represent a group of structurally diverse, small-molecule antagonists of (R, S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptors. Antagonists of AMPA receptors are drug candidates for potential treatment of a number of neurological disorders such as epilepsy, stroke and amyotrophic lateral sclerosis (ALS). How to make better inhibitors, such as 2,3-BDZs, has been an enduring quest in drug discovery. Among a few available tools to address this specific question for making better 2,3-BDZs, perhaps the best one is to use mechanistic clues from studies of the existing antagonists to design and discover more selective and more potent antagonists. Here I review recent work in this area, and propose some ideas in the continuing effort of developing newer 2,3-BDZs for tighter control of AMPA receptor activities in vivo. PMID:26713266

  19. TARP redundancy is critical for maintaining AMPA receptor function.

    PubMed

    Menuz, Karen; O'Brien, Jessica L; Karmizadegan, Siavash; Bredt, David S; Nicoll, Roger A

    2008-08-27

    Transmembrane AMPA receptor regulatory proteins (TARPs) are AMPA receptor auxiliary subunits that influence diverse aspects of receptor function. However, the full complement of physiological roles for TARPs in vivo remains poorly understood. Here we find that double knock-out mice lacking TARPs gamma-2 and gamma-3 are profoundly ataxic and fail to thrive. We demonstrate that these TARPs are critical for the synaptic targeting and kinetics of AMPA receptors in cerebellar Golgi cells, but that either alone is sufficient to fully preserve function. By analyzing the few remaining synaptic AMPA receptors in the gamma-2, gamma-3 double knock-out mice, we unexpectedly find that these TARPs specify AMPA receptor subunit composition. This study establishes a new role for TARPs in regulating AMPA receptor assembly and suggests that TARPs are necessary for proper AMPA receptor localization and function in most, if not all, neurons of the CNS.

  20. Elevated glucose concentration changes the content and cellular localization of AMPA receptors in the retina but not in the hippocampus.

    PubMed

    Castilho, A F; Liberal, J T; Baptista, F I; Gaspar, J M; Carvalho, A L; Ambrósio, A F

    2012-09-06

    Diabetic retinopathy and diabetic encephalopathy are two common complications of diabetes mellitus. The impairment of glutamatergic neurotransmission in the retina and hippocampus has been suggested to be involved in the pathogenesis of these diabetic complications. In this study, we investigated the effect of elevated glucose concentration and diabetes on the protein content and surface expression of AMPA receptor subunits in the rat retina and hippocampus. We have used two models, cultured retinal and hippocampal cells exposed to elevated glucose concentration and an animal model of streptozotocin-induced type 1 diabetes. The immunoreactivity of GluA1, GluA2 and GluA4 was evaluated by Western blot and immunocytochemistry. The levels of these subunits at the plasma membrane were evaluated by biotinylation and purification of plasma membrane-associated proteins. Elevated glucose concentration increased the total levels of GluA2 subunit of AMPA receptors in retinal neural cells, but not of the subunits GluA1 or GluA4. However, at the plasma membrane, elevated glucose concentration induced an increase of all AMPA receptor subunits. In cultured hippocampal neurons, elevated glucose concentration did not induce significant alterations in the levels of AMPA receptor subunits. In the retinas of diabetic rats there were no persistent changes in the levels of AMPA receptor subunits comparing to aged-matched control retinas. Also, no consistent changes were detected in the levels of GluA1, GluA2 or GluA4 in the hippocampus of diabetic rats. We demonstrate that elevated glucose concentration induces early changes in AMPA receptor subunits, mainly in GluA2 subunit, in retinal neural cells. Conversely, hippocampal neurons seem to remain unaffected by elevated glucose concentration, concerning the expression of AMPA receptors, suggesting that AMPA receptors are more susceptible to the stress caused by elevated glucose concentration in retinal cells than in hippocampal neurons.

  1. The essential role of AMPA receptor GluR2 subunit RNA editing in the normal and diseased brain

    PubMed Central

    Wright, Amanda; Vissel, Bryce

    2012-01-01

    α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are comprised of different combinations of GluA1–GluA4 (also known asGluR1–GluR4 and GluR-A to GluR-D) subunits. The GluA2 subunit is subject to RNA editing by the ADAR2 enzyme, which converts a codon for glutamine (Gln; Q), present in the GluA2 gene, to a codon for arginine (Arg; R) found in the mRNA. AMPA receptors are calcium (Ca2+)-permeable if they contain the unedited GluA2(Q) subunit or if they lack the GluA2 subunit. While most AMPA receptors in the brain contain the edited GluA2(R) subunit and are therefore Ca2+-impermeable, recent evidence suggests that Ca2+-permeable AMPA receptors are important in synaptic plasticity, learning, and disease. Strong evidence supports the notion that Ca2+-permeable AMPA receptors are usually GluA2-lacking AMPA receptors, with little evidence to date for a significant role of unedited GluA2 in normal brain function. However, recent detailed studies suggest that Ca2+-permeable AMPA receptors containing unedited GluA2 do in fact occur in neurons and can contribute to excitotoxic cell loss, even where it was previously thought that there was no unedited GluA2.This review provides an update on the role of GluA2 RNA editing in the healthy and diseased brain and summarizes recent insights into the mechanisms that control this process. We suggest that further studies of the role of unedited GluA2 in normal brain function and disease are warranted, and that GluA2 editing should be considered as a possible contributing factor when Ca2+-permeable AMPA receptors are observed. PMID:22514516

  2. URBAN CONTRIBUTIONS OF GLYSPHOSATE AND ITS DEGRADATE AMPA TO STREAMS IN THE UNITED STATES

    EPA Science Inventory

    Glyphosate is the most widely used herbicide in the world, being routinely applied to control weeds in both agricultural and urban settings. Microbial degradation of glyphosate produces aminomethyl phosphonic acid (AMPA). The high polarity and water-solubility of glyphosate and A...

  3. High affinity receptor labeling based on basic leucine zipper domain peptides conjugated with pH-sensitive fluorescent dye: Visualization of AMPA-type glutamate receptor endocytosis in living neurons.

    PubMed

    Hayashi, Ayako; Asanuma, Daisuke; Kamiya, Mako; Urano, Yasuteru; Okabe, Shigeo

    2016-01-01

    Techniques to visualize receptor trafficking in living neurons are important, but currently available methods are limited in their labeling efficiency, specificity and reliability. Here we report a method for receptor labeling with a basic leucine zipper domain peptide (ZIP) and a binding cassette specific to ZIP. Receptors are tagged with a ZIP-binding cassette at their extracellular domain. Tagged receptors expressed in cultured cells were labeled with exogenously applied fluorescently labeled ZIP with low background and high affinity. To test if ZIP labeling is useful in monitoring endocytosis and intracellular trafficking, we next conjugated ZIP with a pH-sensitive dye RhP-M (ZIP-RhP-M). ZIP binding to its binding cassette was pH-resistant and RhP-M fluorescence dramatically increased in acidic environment. Thus AMPA-type glutamate receptors (AMPARs) labeled by ZIP-RhP-M can report receptor endocytosis and subsequent intracellular trafficking. Application of ZIP-RhP-M to cultured hippocampal neurons expressing AMPARs tagged with a ZIP-binding cassette resulted in appearance of fluorescent puncta in PSD-95-positive large spines, suggesting local endocytosis and acidification of AMPARs in individual mature spines. This spine pool of AMPARs in acidic environment was distinct from the early endosomes labeled by transferrin uptake. These results suggest that receptor labeling by ZIP-RhP-M is a useful technique for monitoring endocytosis and intracellular trafficking. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.

  4. AMPA receptors in the therapeutic management of depression.

    PubMed

    Bleakman, D; Alt, A; Witkin, J M

    2007-04-01

    There is an increasing body of evidence implicating a role for alpha-amino-3-hydroxy-5-methyl-4 isoxazoleproprionic acid (AMPA) receptors in major depression and in the actions of antidepressant drugs. Alterations in AMPA receptors and other ionotropic glutamate receptors have been reported in depression, and following antidepressant treatment. Compounds which augment signaling through AMPA receptors (AMPA receptor potentiators) exhibit antidepressant-like behavioral effects in animal models, and produce neuronal effects similar to those produced by currently available antidepressants, including neurotrophin induction and increases in hippocampal progenitor cell proliferation. Additionally, the antidepressant fluoxetine has been found to alter AMPA receptor phosphorylation in a manner that is expected to increase AMPA receptor signaling. Data from mutant mice suggest that AMPA receptors may regulate the expression of brain-derived neurotrophic factor, a neurotrophin which has been implicated in the actions of antidepressant therapies. Combined, these data suggest that AMPA receptors may be in a key position to regulate mood disorders, and that compounds which target AMPA receptors may prove useful in the clinical management of depression.

  5. Blockade of calcium-permeable AMPA receptors protects hippocampal neurons against global ischemia-induced death

    PubMed Central

    Noh, Kyung-Min; Yokota, Hidenori; Mashiko, Toshihiro; Castillo, Pablo E.; Zukin, R. Suzanne; Bennett, Michael V. L.

    2005-01-01

    Transient global or forebrain ischemia induced experimentally in animals can cause selective, delayed neuronal death of hippocampal CA1 pyramidal neurons. A striking feature is a delayed rise in intracellular free Zn2+ in CA1 neurons just before the onset of histologically detectable cell death. Here we show that α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) at Schaffer collateral to CA1 synapses in postischemic hippocampus exhibit properties of Ca2+/Zn2+-permeable, Glu receptor 2 (GluR2)-lacking AMPARs before the rise in Zn2+ and cell death. At 42 h after ischemia, AMPA excitatory postsynaptic currents exhibited pronounced inward rectification and marked sensitivity to 1-naphthyl acetyl spermine (Naspm), a selective channel blocker of GluR2-lacking AMPARs. In control hippocampus, AMPA excitatory postsynaptic currents were electrically linear and relatively insensitive to Naspm. Naspm injected intrahippocampally at 9-40 h after insult greatly reduced the late rise in intracellular free Zn2+ in postischemic CA1 neurons and afforded partial protection against ischemia-induced cell death. These results implicate GluR2-lacking AMPA receptors in the ischemia-induced rise in free Zn2+ and death of CA1 neurons, although a direct action at the time of the rise in Zn2+ is unproven. This receptor subtype appears to be an important therapeutic target for intervention in ischemia-induced neuronal death in humans. PMID:16093311

  6. Occurrence of glyphosate and AMPA in an agricultural watershed from the southeastern region of Argentina.

    PubMed

    Lupi, Leonardo; Miglioranza, Karina S B; Aparicio, Virginia C; Marino, Damian; Bedmar, Francisco; Wunderlin, Daniel A

    2015-12-01

    Glyphosate (GLY) and AMPA concentrations were determined in sandy soil profiles, during pre- and post-application events in two agricultural soybean fields (S1 and S2). Streamwater and sediment samples were also analyzed. Post-application sampling was carried out one month later from the event. Concentrations of GLY+AMPA in surface soils (0-5 cm depth) during pre-application period showed values 20-fold higher (0.093-0.163 μg/g d.w.) than control area (0.005 μg/g d.w.). After application event soils showed markedly higher pesticide concentrations. A predominance of AMPA (80%) was observed in S1 (early application), while 34% in S2 for surface soils. GLY+AMPA concentrations decreased with depth and correlated strongly with organic carbon (r between 0.74 and 0.88, p<0.05) and pH (r between -0.81 and -0.76, p<0.001). The slight enrichment of pesticides observed from 25 cm depth to deeper layer, in addition to the alkaline pH along the profile, is of high concern about groundwater contamination. Sediments from pre-application period showed relatively lower pesticide levels (0.0053-0.0263 μg/g d.w.) than surface soil with a predominance of glyphosate, indicating a limited degradation. Levels of contaminants (mainly AMPA) in streamwater (ND-0.5 ng/mL) denote the low persistence of these compounds. However, a direct relationship in AMPA concentration was observed between sediment and streamwater. Despite the known relatively short half-life of glyphosate in soils, GLY+AMPA occurrence is registered in almost all matrices at different sampling times (pre- and post-application events). The physicochemical characteristics (organic carbon, texture, pH) and structure of soils and sediment in addition to the time elapsed from application determined the behavior of these contaminants in the environment. As a whole, the results warn us about vertical transport trough soil profile with the possibility of reaching groundwater.

  7. Benzoxazinones as potent positive allosteric AMPA receptor modulators: part I.

    PubMed

    Mueller, Rudolf; Li, Yong-Xin; Hampson, Aidan; Zhong, Sheng; Harris, Clayton; Marrs, Christopher; Rachwal, Stanislaw; Ulas, Jolanta; Nielsson, Lena; Rogers, Gary

    2011-07-01

    AMPA receptors (AMPARs) are an increasingly important therapeutic target in the CNS. Aniracetam, the first identified potentiator of AMPARs, led to the rigid and more potent CX614. This lead molecule was optimized in order to increase affinity towards the AMPA receptor. The substitution of the dioxine with a benzoxazinone ring system increased the activity and allowed further investigation of the sidechain SAR.

  8. AMPA receptor potentiators for the treatment of CNS disorders.

    PubMed

    O'Neill, Michael J; Bleakman, David; Zimmerman, Dennis M; Nisenbaum, Eric S

    2004-06-01

    Glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors mediate most of the excitatory neurotransmission in the mammalian central nervous system and also participate in forms of synaptic plasticity thought to underlie memory and learning, and the formation of neural networks during development. Molecular cloning techniques have shown that the AMPA receptor family is composed of four different subunits named GluR1-4 or GluRA-D (newly termed as Glu(A1)-Glu(A4)) and native AMPA receptors are most likely tetramers generated by the assembly of one or more of these subunits, yielding homomeric or heteromeric receptors. Additional complexity among AMPA receptors is conferred by alternative splicing of RNA for each subunit giving rise to flip and flop variants. Clinical and experimental data have suggested that positive modulation of AMPA receptors may be therapeutically effective in the treatment of cognitive deficits. Several classes of AMPA receptor potentiators have been reported, including pyrroliddones (piracetam, aniracetam), benzothiazides (cyclothiazide), benzylpiperidines (CX-516, CX-546) and more recently biarylpropylsulfonamides (LY392098, LY404187 and LY503430). These molecules enhance cognitive function in rodents, which appears to correlate with increased hippocampal activity. In addition, clinical studies have suggested that AMPA receptor modulators enhance cognitive function in elderly subjects, as well as patients suffering from neurological and psychiatric disorders. Several independent studies have suggested that AMPA receptors can increase BDNF expression by both calcium-dependent and independent pathways. For example, recent studies have shown that AMPA receptors interact with the protein tyrosine kinase, Lyn. Activation of Lyn can recruit the mitogen-activated protein kinase (MAPK) signalling pathway and increase the expression of BDNF. Therefore, in addition to directly enhancing glutamatergic synaptic transmission, AMPA

  9. Regulation of AMPA receptor gating and pharmacology by TARP auxiliary subunits.

    PubMed

    Milstein, Aaron D; Nicoll, Roger A

    2008-07-01

    Presynaptic glutamate release elicits brief waves of membrane depolarization in neurons by activating AMPA receptors. Depending on its precise size and shape, current through AMPA receptors gates downstream processes like NMDA receptor activation and action potential generation. Over a decade of research on AMPA receptor structure and function has identified binding sites on AMPA receptors for agonists, antagonists and allosteric modulators as well as key residues underlying differences in the gating behavior of various AMPA receptor subtypes. However, the recent discovery that AMPA receptors are accompanied in the synaptic membrane by a family of auxiliary subunits known as transmembrane AMPA receptor regulatory proteins (TARPs) has revealed that the kinetics and pharmacology of neuronal AMPA receptors differ in many respects from those predicted by classical studies of AMPA receptors in heterologous systems. Here, we summarize recent work and discuss remaining questions concerning the structure and function of native TARP-AMPA receptor complexes.

  10. KIS, a kinase associated with microtubule regulators, enhances translation of AMPA receptors and stimulates dendritic spine remodeling.

    PubMed

    Pedraza, Neus; Ortiz, Raúl; Cornadó, Alba; Llobet, Artur; Aldea, Martí; Gallego, Carme

    2014-10-15

    Local regulation of protein synthesis allows a neuron to rapidly alter the proteome in response to synaptic signals, an essential mechanism in synaptic plasticity that is altered in many neurological diseases. Synthesis of many synaptic proteins is under local control and much of this regulation occurs through structures termed RNA granules. KIS is a protein kinase that associates with stathmin, a modulator of the tubulin cytoskeleton. Furthermore, KIS is found in RNA granules and stimulates translation driven by the β-actin 3'UTR in neurites. Here we explore the physiological and molecular mechanisms underlying the action of KIS on hippocampal synaptic plasticity in mice. KIS downregulation compromises spine development, alters actin dynamics, and reduces postsynaptic responsiveness. The absence of KIS results in a significant decrease of protein levels of PSD-95, a postsynaptic scaffolding protein, and the AMPAR subunits GluR1 and GluR2 in a CPEB3-dependent manner. Underlying its role in spine maturation, KIS is able to suppress the spine developmental defects caused by CPEB3 overexpression. Moreover, either by direct or indirect mechanisms, KIS counteracts the inhibitory activity of CPEB3 on the GluR2 3'UTR at both mRNA translation and polyadenylation levels. Our study provides insights into the mechanisms that mediate dendritic spine morphogenesis and functional synaptic maturation, and suggests KIS as a link regulating spine cytoskeleton and postsynaptic activity in memory formation.

  11. Differences of AMPA and kainate receptor interactomes identify a novel AMPA receptor auxiliary subunit, GSG1L

    PubMed Central

    Shanks, Natalie F.; Savas, Jeffrey N.; Maruo, Tomohiko; Cais, Ondrej; Hirao, Atsushi; Oe, Souichi; Ghosh, Anirvan; Noda, Yasuko; Greger, Ingo H.; Yates, John R.; Nakagawa, Terunaga

    2012-01-01

    AMPA receptor (AMPA-R) complexes consist of channel forming subunits, GluA1–4 and auxiliary proteins including TARPs, CNIHs, synDIG1, and CKAMP44, which can modulate AMPA-R function in specific ways. Combinatorial effects of four GluA subunits binding to various auxiliary subunits amplify the functional diversity of AMPA-Rs. The significance and magnitude of molecular diversity, however, remain elusive. To gain insight into the molecular complexity of AMPA and kainate receptors (KA-Rs), we compared the proteins that co-purify with each receptor type in rat brain. This interactome study identified the majority of known interacting proteins and more importantly, provides novel candidates for further studies. We validate the claudin homologue GSG1L as a novel binding protein and unique modulator of AMPA-R gating, as determined by detailed molecular, cellular, electrophysiological, and biochemical experiments. GSG1L extends the functional variety of AMPA-R complexes and further investigation of other candidates may reveal additional complexity of ionotropic glutamate receptor function. PMID:22813734

  12. TARP modulation of synaptic AMPA receptor trafficking and gating depends on multiple intracellular domains.

    PubMed

    Milstein, Aaron D; Nicoll, Roger A

    2009-07-07

    Previous work has established stargazin and its related family of transmembrane AMPA receptor regulatory proteins (TARPs) as auxiliary subunits of AMPA receptors (AMPARs) that control synaptic strength both by targeting AMPARs to synapses through an intracellular PDZ-binding motif and by modulating their gating through an extracellular domain. However, TARPs gamma-2 and gamma-8 differentially regulate the synaptic targeting of AMPARs, despite having identical PDZ-binding motifs. Here, we investigate the structural elements that contribute to this functional difference between TARP subtypes by using domain transplantation and truncation. We identify a component of synaptic AMPAR trafficking that is independent of the TARP C-terminal PDZ-binding motif, and we establish previously uncharacterized roles for the TARP intracellular N terminus, loop, and C terminus in modulating both the trafficking and gating of synaptic AMPARs.

  13. Brain Region-Specific Effects of cGMP-Dependent Kinase II Knockout on AMPA Receptor Trafficking and Animal Behavior

    ERIC Educational Resources Information Center

    Kim, Seonil; Pick, Joseph E.; Abera, Sinedu; Khatri, Latika; Ferreira, Danielle D. P.; Sathler, Matheus F.; Morison, Sage L.; Hofmann, Franz; Ziff, Edward B.

    2016-01-01

    Phosphorylation of GluA1, a subunit of AMPA receptors (AMPARs), is critical for AMPAR synaptic trafficking and control of synaptic transmission. cGMP-dependent protein kinase II (cGKII) mediates this phosphorylation, and cGKII knockout (KO) affects GluA1 phosphorylation and alters animal behavior. Notably, GluA1 phosphorylation in the KO…

  14. AMPA receptor subunits expression and phosphorylation in cingulate cortex in rats following esophageal acid exposure

    PubMed Central

    BANERJEE, B.; MEDDA, B. K.; POCHIRAJU, S.; KANNAMPALLI, P.; LANG, I. M.; SENGUPTA, J. N.; SHAKER, R.

    2014-01-01

    Background We recently reported an increase in N-methyl-d-aspartate (NMDA) receptor subunit expression and CaMKII-dependent phosphorylation of NR2B in the rostral cingulate cortical (rCC) neurons following esophageal acid exposure in rats. As α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors mediate the fast excitatory transmission and play a critical role in synaptic plasticity, in this study, we investigated the effect of esophageal acid exposure in rats on the expression of AMPA receptor subunits and the involvement of these molecular alterations in acid-induced sensitization of neurons in the anterior cingulate (ACC) and midcingulate (MCC) cortices. Methods In molecular study, we examined GluA1 and GluA2 expression and phosphorylation in membrane preparations and in the isolated postsynaptic densities (PSDs) from rats receiving acute esophageal exposure of either saline (control group) or 0.1 NHCl (experimental group). In electrophysiological study, the effect of selective AMPA receptor (Ca2+ permeable) antagonist IEM-1460 and CaMKII inhibitor KN-93 was tested on responses of cortical neurons during acid infusion to address the underlying molecular mechanism of acid-induced sensitization. Key Results The acid exposure significantly increased expression of GluA1, pGluA1Ser831, and phosphorylated CaMKIIThr286, in the cortical membrane preparations. In isolated PSDs, a significant increase in pGluA1Ser831 was observed in acid-treated rats compared with controls. Microinjection of IEM-1460 or KN-93 near the recording site significantly attenuated acid-induced sensitization of cortical neurons. Conclusions & Inferences The underlying mechanism of acid-induced cortical sensitization involves upregulation and CaMKII-mediated phosphorylation of GluA1. These molecular changes of AMPA receptors subunit GluA1 in the cortical neurons might play an important role in acid-induced esophageal hypersensitivity. PMID:24118589

  15. Novel bivalent positive allosteric modulators of AMPA receptor.

    PubMed

    Lavrov, M I; Grigor'ev, V V; Bachurin, S O; Palyulin, V A; Zefirov, N S

    2015-01-01

    A positive allosteric modulator of AMPA receptors has been designed using computer-aided molecular modeling techniques. It possessed a record high experimentally confirmed potency in the picomolar concentration range and belongs to a new type of bivalent AMPA receptor ligands containing bicyclo[3.3.1]nonane scaffold. The suggested structure could serve as a basis for further optimization and development of drugs for the treatment of neurodegenerative diseases, cognition enhancement, and improvement of memory.

  16. AMPA receptors as a molecular target in epilepsy therapy.

    PubMed

    Rogawski, M A

    2013-01-01

    Epileptic seizures occur as a result of episodic abnormal synchronous discharges in cerebral neuronal networks. Although a variety of non-conventional mechanisms may play a role in epileptic synchronization, cascading excitation within networks of synaptically connected excitatory glutamatergic neurons is a classical mechanism. As is the case throughout the central nervous system, fast synaptic excitation within and between brain regions relevant to epilepsy is mediated predominantly by AMPA receptors. By inhibiting glutamate-mediated excitation, AMPA receptor antagonists markedly reduce or abolish epileptiform activity in in vitro preparations and confer seizure protection in a broad range of animal seizure models. NMDA receptors may also contribute to epileptiform activity, but NMDA receptor blockade is not sufficient to eliminate epileptiform discharges. AMPA receptors move into and out of the synapse in a dynamic fashion in forms of synaptic plasticity, underlying learning and memory. Often, the trigger for these dynamic movements is the activation of NMDA receptors. While NMDA receptor antagonists inhibit these forms of synaptic plasticity, AMPA receptor antagonists do not impair synaptic plasticity and do not inhibit memory formation or retrieval. The demonstrated clinical efficacy of perampanel, a high-potency, orally active non-competitive AMPA receptor antagonist, supports the concept that AMPA receptors are critical to epileptic synchronization and the generation and spread of epileptic discharges in human epilepsy.

  17. Regulation of postsynaptic AMPA responses by synaptojanin 1.

    PubMed

    Gong, Liang-Wei; De Camilli, Pietro

    2008-11-11

    Endocytosis of postsynaptic AMPA receptors is a mechanism through which efficiency of neurotransmission is regulated. We have genetically tested the hypothesis that synaptojanin 1, a phosphoinositide phosphatase implicated in the endocytosis of synaptic vesicles presynaptically, may also function in the endocytosis of AMPA receptors postsynaptically. Electrophysiological recordings of cultured hippocampal neurons showed that miniature excitatory postsynaptic current amplitudes were larger in synaptojanin 1 knockout (KO) neurons because of an increase of surface-exposed AMPA receptors. This change did not represent an adaptive response to decreased presynaptic release in KO cultures and was rescued by the expression of wild type, but not catalytically inactive synaptojanin 1, in the postsynaptic neuron. NMDA-induced internalization of pHluorin-tagged AMPA receptors (GluR2) was impaired in KO neurons. These results reveal a function of synaptojanin 1 in constitutive and triggered internalization of AMPA receptors and thus indicate a role for phosphatidylinositol(4,5)-bisphosphate metabolism in the regulation of postsynaptic AMPA responses.

  18. AMPA Receptors as a Molecular Target in Epilepsy Therapy

    PubMed Central

    Rogawski, Michael A.

    2013-01-01

    Epileptic seizures occur as a result of episodic abnormal synchronous discharges in cerebral neuronal networks. Although a variety of nonconventional mechanisms may play a role in epileptic synchronization, cascading excitation within networks of synaptically connected excitatory glutamatergic neurons is a classical mechanism. As is the case throughout the central nervous system, fast synaptic excitation within and between brain regions relevant to epilepsy is mediated predominantly by AMPA receptors. By inhibiting glutamate-mediated excitation, AMPA receptor antagonists markedly reduce or abolish epileptiform activity in in vitro preparations and confer seizure protection in a broad range of animal seizure models. NMDA receptors may also contribute to epileptiform activity, but NMDA receptor blockade is not sufficient to eliminate epileptiform discharges. AMPA receptors move into and out of the synapse in a dynamic fashion in forms of synaptic plasticity, underlying learning and memory. Often the trigger for these dynamic movements is activation of NMDA receptors. While NMDA receptor antagonists inhibit these forms of synaptic plasticity, AMPA receptor antagonists do not impair synaptic plasticity and do not inhibit memory formation or retrieval. The demonstrated clinical efficacy of perampanel, a high-potency, orally active noncompetitive AMPA receptor antagonist, supports the concept that AMPA receptors are critical to epileptic synchronization and the generation and spread of epileptic discharges in human epilepsy. PMID:23480151

  19. Ca2+-permeable AMPA receptors in mouse olfactory bulb astrocytes

    PubMed Central

    Droste, Damian; Seifert, Gerald; Seddar, Laura; Jädtke, Oliver; Steinhäuser, Christian; Lohr, Christian

    2017-01-01

    Ca2+ signaling in astrocytes is considered to be mainly mediated by metabotropic receptors linked to intracellular Ca2+ release. However, recent studies demonstrate a significant contribution of Ca2+ influx to spontaneous and evoked Ca2+ signaling in astrocytes, suggesting that Ca2+ influx might account for astrocytic Ca2+ signaling to a greater extent than previously thought. Here, we investigated AMPA-evoked Ca2+ influx into olfactory bulb astrocytes in mouse brain slices using Fluo-4 and GCaMP6s, respectively. Bath application of AMPA evoked Ca2+ transients in periglomerular astrocytes that persisted after neuronal transmitter release was inhibited by tetrodotoxin and bafilomycin A1. Withdrawal of external Ca2+ suppressed AMPA-evoked Ca2+ transients, whereas depletion of Ca2+ stores had no effect. Both Ca2+ transients and inward currents induced by AMPA receptor activation were partly reduced by Naspm, a blocker of Ca2+-permeable AMPA receptors lacking the GluA2 subunit. Antibody staining revealed a strong expression of GluA1 and GluA4 and a weak expression of GluA2 in periglomerular astrocytes. Our results indicate that Naspm-sensitive, Ca2+-permeable AMPA receptors contribute to Ca2+ signaling in periglomerular astrocytes in the olfactory bulb. PMID:28322255

  20. Glyphosate and AMPA contents in sediments produced by wind erosion of agricultural soils in Argentina

    NASA Astrophysics Data System (ADS)

    Aparicio, Virginia; Aimar, Silvia; De Gerónimo, Eduardo; Buschiazzo, Daniel; Mendez, Mariano; Costa, José Luis

    2014-05-01

    Wind erosion of soils is an important event in arid and semiarid regions of Argentina. The magnitude of wind erosion occurring under different management practices is relatively well known in this region but less information is available on the quality of the eroded material. Considering that the intensification of agriculture may increase the concentrations of substances in the eroded material, producing potential negative effects on the environment, we analyzed the amount of glyphosate and AMPA in sediments produced by wind erosion of agricultural soils of Argentina. Wind eroded materials were collected by means of BSNE samplers in two loess sites of the semiarid region of Argentina: Chaco and La Pampa. Samples were collected from 1 ha square fields at 13.5, 50 and 150 cm height. Results showed that at higher heights the concentrations of glyphosate and AMPA were mostly higher. The glyphosate concentration was more variable and higher in Chaco (0.66 to 313 µg kg-1) than in La Pampa (4.17 to 114 µg kg-1). These results may be due to the higher use of herbicides in Chaco, where the predominant crops are soybeans and corn, produced under no-tillage. Under these conditions the use of glyphosate for weeds control is a common practice. Conversely, AMPA concentrations were higher in La Pampa (13.1 to 101.3 µg kg-1) than in Chaco (1.3 to 83 µg kg-1). These preliminary results show high concentrations of glyphosate and AMPA in wind eroded materials of agricultural soils of Argentina. More research is needed to confirm these high concentrations in other conditions in order to detect the temporal and spatial distribution patterns of the herbicide.

  1. PACSIN1 regulates the dynamics of AMPA receptor trafficking.

    PubMed

    Widagdo, Jocelyn; Fang, Huaqiang; Jang, Se Eun; Anggono, Victor

    2016-08-04

    Dynamic trafficking of AMPA receptors (AMPARs) into and out of synapses plays an important role in synaptic plasticity. We previously reported that the protein kinase C and casein kinase II substrate in neurons (PACSIN) forms a complex with AMPARs through its interaction with the protein interacting with C-kinase 1 (PICK1) to regulate NMDA receptor (NMDAR)-induced AMPAR endocytosis and cerebellar long-term depression. However, the molecular mechanism by which PACSIN regulates the dynamics of AMPAR trafficking remains unclear. Using a pH-sensitive green fluorescent protein, pHluorin, tagged to the extracellular domain of the GluA2 subunit of AMPARs, we demonstrate dual roles for PACSIN1 in controlling the internalization and recycling of GluA2 after NMDAR activation. Structure and function analysis reveals a requirement for the PACSIN1 F-BAR and SH3 domains in controlling these NMDAR-dependent processes. Interestingly, the variable region, which binds to PICK1, is not essential for NMDAR-dependent GluA2 internalization and is required only for the correct recycling of AMPARs. These results indicate that PACSIN is a versatile membrane deformation protein that links the endocytic and recycling machineries essential for dynamic AMPAR trafficking in neurons.

  2. PACSIN1 regulates the dynamics of AMPA receptor trafficking

    PubMed Central

    Widagdo, Jocelyn; Fang, Huaqiang; Jang, Se Eun; Anggono, Victor

    2016-01-01

    Dynamic trafficking of AMPA receptors (AMPARs) into and out of synapses plays an important role in synaptic plasticity. We previously reported that the protein kinase C and casein kinase II substrate in neurons (PACSIN) forms a complex with AMPARs through its interaction with the protein interacting with C-kinase 1 (PICK1) to regulate NMDA receptor (NMDAR)-induced AMPAR endocytosis and cerebellar long-term depression. However, the molecular mechanism by which PACSIN regulates the dynamics of AMPAR trafficking remains unclear. Using a pH-sensitive green fluorescent protein, pHluorin, tagged to the extracellular domain of the GluA2 subunit of AMPARs, we demonstrate dual roles for PACSIN1 in controlling the internalization and recycling of GluA2 after NMDAR activation. Structure and function analysis reveals a requirement for the PACSIN1 F-BAR and SH3 domains in controlling these NMDAR-dependent processes. Interestingly, the variable region, which binds to PICK1, is not essential for NMDAR-dependent GluA2 internalization and is required only for the correct recycling of AMPARs. These results indicate that PACSIN is a versatile membrane deformation protein that links the endocytic and recycling machineries essential for dynamic AMPAR trafficking in neurons. PMID:27488904

  3. Roles of fragile X mental retardation protein in dopaminergic stimulation-induced synapse-associated protein synthesis and subsequent alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-4-propionate (AMPA) receptor internalization.

    PubMed

    Wang, Hansen; Kim, Susan S; Zhuo, Min

    2010-07-09

    Fragile X syndrome, the most common form of inherited mental retardation, is caused by the absence of the RNA-binding protein fragile X mental retardation protein (FMRP). FMRP regulates local protein synthesis in dendritic spines. Dopamine (DA) is involved in the modulation of synaptic plasticity. Activation of DA receptors can regulate higher brain functions in a protein synthesis-dependent manner. Our recent study has shown that FMRP acts as a key messenger for DA modulation in forebrain neurons. Here, we demonstrate that FMRP is critical for DA D1 receptor-mediated synthesis of synapse-associated protein 90/PSD-95-associated protein 3 (SAPAP3) in the prefrontal cortex (PFC). DA D1 receptor stimulation induced dynamic changes of FMRP phosphorylation. The changes in FMRP phosphorylation temporally correspond with the expression of SAPAP3 after D1 receptor stimulation. Protein phosphatase 2A, ribosomal protein S6 kinase, and mammalian target of rapamycin are the key signaling molecules for FMRP linking DA D1 receptors to SAPAP3. Knockdown of SAPAP3 did not affect surface expression of alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-4-propionate (AMPA) GluR1 receptors induced by D1 receptor activation but impaired their subsequent internalization in cultured PFC neurons; the subsequent internalization of GluR1 was also impaired in Fmr1 knock-out PFC neurons, suggesting that FMRP may be involved in subsequent internalization of GluR1 through regulating the abundance of SAPAP3 after DA D1 receptor stimulation. Our study thus provides further insights into FMRP involvement in DA modulation and may help to reveal the molecular mechanisms underlying impaired learning and memory in fragile X syndrome.

  4. Mechanism of Positive Allosteric Modulators Acting on AMPA Receptors

    SciTech Connect

    Jin,R.; Clark, S.; Weeks, A.; Dudman, J.; Gouaux, E.; Partin, K.

    2005-01-01

    Ligand-gated ion channels involved in the modulation of synaptic strength are the AMPA, kainate, and NMDA glutamate receptors. Small molecules that potentiate AMPA receptor currents relieve cognitive deficits caused by neurodegenerative diseases such as Alzheimer's disease and show promise in the treatment of depression. Previously, there has been limited understanding of the molecular mechanism of action for AMPA receptor potentiators. Here we present cocrystal structures of the glutamate receptor GluR2 S1S2 ligand-binding domain in complex with aniracetam [1-(4-methoxybenzoyl)-2-pyrrolidinone] or CX614 (pyrrolidino-1, 3-oxazino benzo-1, 4-dioxan-10-one), two AMPA receptor potentiators that preferentially slow AMPA receptor deactivation. Both potentiators bind within the dimer interface of the nondesensitized receptor at a common site located on the twofold axis of molecular symmetry. Importantly, the potentiator binding site is adjacent to the 'hinge' in the ligand-binding core 'clamshell' that undergoes conformational rearrangement after glutamate binding. Using rapid solution exchange, patch-clamp electrophysiology experiments, we show that point mutations of residues that interact with potentiators in the cocrystal disrupt potentiator function. We suggest that the potentiators slow deactivation by stabilizing the clamshell in its closed-cleft, glutamate-bound conformation.

  5. Interactions between recording technique and AMPA receptor modulators.

    PubMed

    Lin, Bin; Colgin, Laura Lee; Brücher, Fernando Andres; Arai, Amy Christine; Lynch, Gary

    2002-11-15

    Whole cell recording (EPSCs) and extracellular recording (field EPSPs) were compared in hippocampal field CA1 with regard to the effects of experimental treatments that increase AMPA receptor gated currents. Cyclothiazide, which maintains AMPA receptors in the sensitized state, caused a rapid and pronounced increase in EPSCs but only minor changes in field EPSPs. This difference was evident in recordings carried out at 22 and 32 degrees C and with different solutions in the clamp pipette. The larger effect of cyclothiazide on EPSCs was unaffected by blockade of GABA and NMDA receptors. Two-dimensional current source density analyses derived from 64 recording sites were used to provide extracellular estimates of AMPA receptor mediated synaptic currents. With this method, cyclothiazide again had much smaller effects than were obtained with whole cell clamp. Differences between whole cell and extracellular recordings were present, although not as pronounced, for the ampakines, a class of drugs that slow both deactivation and desensitization of AMPA receptors. Additionally, increases in synaptic responses produced by frequency facilitation, a manipulation that enhances the number of bound receptors, were not qualitatively different between recording techniques. These results support the conclusion that the whole cell clamp technique may alter AMPA receptors in such a way as to increase the relative importance of desensitization.

  6. Are AMPA Receptor Positive Allosteric Modulators Potential Pharmacotherapeutics for Addiction?

    PubMed Central

    Watterson, Lucas R.; Olive, M. Foster

    2013-01-01

    Positive allosteric modulators (PAMs) of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are a diverse class of compounds that increase fast excitatory transmission in the brain. AMPA PAMs have been shown to facilitate long-term potentiation, strengthen communication between various cortical and subcortical regions, and some of these compounds increase the production and release of brain-derived neurotrophic factor (BDNF) in an activity-dependent manner. Through these mechanisms, AMPA PAMs have shown promise as broad spectrum pharmacotherapeutics in preclinical and clinical studies for various neurodegenerative and psychiatric disorders. In recent years, a small collection of preclinical animal studies has also shown that AMPA PAMs may have potential as pharmacotherapeutic adjuncts to extinction-based or cue-exposure therapies for the treatment of drug addiction. The present paper will review this preclinical literature, discuss novel data collected in our laboratory, and recommend future research directions for the possible development of AMPA PAMs as anti-addiction medications. PMID:24380895

  7. Molecular Mechanism of AMPA Receptor Modulation by TARP/Stargazin.

    PubMed

    Ben-Yaacov, Anat; Gillor, Moshe; Haham, Tomer; Parsai, Alon; Qneibi, Mohammad; Stern-Bach, Yael

    2017-03-08

    AMPA receptors (AMPARs) mediate the majority of fast excitatory transmission in the brain and critically contribute to synaptic plasticity and pathology. AMPAR trafficking and gating are tightly controlled by auxiliary transmembrane AMPAR regulatory proteins (TARPs). Here, using systematic domain swaps with the TARP-insensitive kainate receptor GluK2, we show that AMPAR interaction with the prototypical TARP stargazin/γ2 primarily involves the AMPAR membrane domains M1 and M4 of neighboring subunits, initiated or stabilized by the AMPAR C-tail, and that these interactions are sufficient to enable full receptor modulation. Moreover, employing TARP chimeras disclosed a key role in this process also for the TARP transmembrane domains TM3 and TM4 and extracellular loop 2. Mechanistically, our data support a two-step action in which binding of TARP to the AMPAR membrane domains destabilizes the channel closed state, thereby enabling an efficient opening upon agonist binding, which then stabilizes the open state via subsequent interactions.

  8. The PARP inhibitor benzamide protects against kainate and NMDA but not AMPA lesioning of the mouse striatum in vivo.

    PubMed

    Cosi, Cristina; Guerin, Karen; Marien, Marc; Koek, Wouter; Rollet, Karin

    2004-01-16

    Overactivation of poly(ADP-ribose) polymerase (PARP) in response to genotoxic insults can cause cell death by energy deprivation. We previously reported that neurotoxic amounts of kainic acid (KA) injected into the rat striatum produce time-dependent changes in striatal PARP activity in vivo. Here, we have investigated the time-course of KA-induced toxicity and the effects of the PARP inhibitor benzamide on KA, AMPA and NMDA neurotoxicities in vivo, by measuring changes in the volume of the lesion and in NAD+ and ATP levels induced by the intra-striatal injection of these excitotoxins in C57Bl/6N mice. The KA-induced lesion volume was dependent on the amount of toxin injected and the survival time. The lesion was well developed at 48 h and was almost undetectable after one week. KA produced an extensive astrogliosis at one week. Benzamide partially prevented both KA- and NMDA- but not AMPA-induced lesions when measured at 48 h after the treatment. The effects of benzamide appeared to be in part related to changes in energy metabolism, since KA produced decreases in striatal levels of NAD+ and ATP that were partially prevented by benzamide at 48 h and which returned to control levels at one week. NMDA did not affect NAD+ and induced little alteration in ATP levels. Benzamide had no effect on AMPA-induced decreases in either NAD+ or ATP levels at 48 h. These results (1) indicate that PARP overactivation and energy depletion could be responsible in part for the cellular demise during the development of the lesion induced by KA; (2) confirm that PARP is involved in NMDA but not AMPA toxicities; (3) suggest the existence of differences between KA and AMPA-mediated toxicities; and (4) provide further evidence supporting PARP as a novel target for new drug treatments against neurodegenerative disorders.

  9. The neurosteroid dehydroepiandrosterone (DHEA) protects the retina from AMPA-induced excitotoxicity: NGF TrkA receptor involvement.

    PubMed

    Kokona, Despina; Charalampopoulos, Ioannis; Pediaditakis, Iosif; Gravanis, Achille; Thermos, Kyriaki

    2012-04-01

    The aim of the present study was to investigate the neuroprotective properties of the endogenous neurosteroid dehydroepiandrosterone (DHEA) in an in vivo model of retinal excitotoxicity, and the involvement of Nerve Growth Factor (NGF) in its actions. Adult Sprague-Dawley rats (250-300 g) received intravitreally (RS)-alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid hydrobromide (AMPA; 42 nmol/eye) alone or in combination with DHEA (10(-8), 10(-7), 10(-6) M), or PBS (50 mM, control group). To examine the involvement of NGF and its TrkA receptor in the pharmacological effects of DHEA, animals received AMPA and NGF (60 pg/eye) in the absence or presence of a TrkA receptor inhibitor (Calbiochem 648450, 10(-6) M) or AMPA, DHEA (10(-6) M) and TrkA receptor inhibitor (10(-6), 10(-5) M). Immunohistochemistry studies [choline acetyltransferase (ChAT), brain nitric oxide synthetase (bNOS), calbindin, and TUNEL] and fluorescence-activated cell sorting (FACS) were used to examine retinal cell loss and protection. TrkA receptor immunoreactivity (-IR) and colocalization studies with relevant markers were also performed. AMPA (42 nmol) treatment resulted in a loss of bNOS, ChAT and calbindin immunoreactivities 24 h after its administration. DHEA, administered intravitreally, protected the retina from excitotoxicity in a dose-dependent manner. This effect was mimicked by NGF, and reversed by the NGF TrkA receptor inhibitor. The TrkA receptor is expressed in ganglion cells of rat retina. TUNEL staining and FACS analysis substantiated the neuroprotective actions of DHEA. These results demonstrate for the first time that the neurosteroid DHEA, administered intravitreally, protects the retina from AMPA excitotoxicity. An NGF TrkA receptor mechanism appears to be involved in this neuroprotection.

  10. AMPA receptors as drug targets in neurological disease--advantages, caveats, and future outlook.

    PubMed

    Chang, Philip K-Y; Verbich, David; McKinney, R Anne

    2012-06-01

    Most excitatory transmission in the brain is mediated by the AMPA receptor subtype of the ionotropic glutamate receptors. In many neurological diseases, synapse structure and AMPA receptor function are altered, thus making AMPA receptors potential therapeutic targets for clinical intervention. The work summarized in this review suggests a link between AMPA receptor function and debilitating neuropathologies, and discusses the current state of therapies targeting AMPA receptors in four diseases. In amyotrophic lateral sclerosis, AMPA receptors allow cytotoxic levels of calcium into neurons, leading to motor neuron death. Likewise, in some epilepsies, overactivation of AMPA receptors leads to neuron damage. The same is true for ischemia, where oxygen deprivation leads to excitotoxicity. Conversely, Alzheimer's disease is characterized by decreased AMPA activation and synapse loss. Unfortunately, many clinical studies have had limited success by directly targeting AMPA receptors in these diseases. We also discuss how the use of AMPA receptor modulators, commonly known as ampakines, in neurological diseases initially seemed promising in animal studies, but mostly ineffective in clinical trials. We propose that indirectly affecting AMPA receptors, such as by modulating transmembrane AMPA receptor regulatory proteins or, more generally, by regulating glutamatergic transmission, may provide new therapeutic potential for neurological disorders.

  11. Ganglioside Regulation of AMPA Receptor Trafficking

    PubMed Central

    Prendergast, Jillian; Umanah, George K.E.; Yoo, Seung-Wan; Lagerlöf, Olof; Motari, Mary G.; Cole, Robert N.; Huganir, Richard L.; Dawson, Ted M.; Dawson, Valina L.

    2014-01-01

    Gangliosides are major cell-surface determinants on all vertebrate neurons. Human congenital disorders of ganglioside biosynthesis invariably result in intellectual disability and are often associated with intractable seizures. To probe the mechanisms of ganglioside functions, affinity-captured ganglioside-binding proteins from rat cerebellar granule neurons were identified by quantitative proteomic mass spectrometry. Of the six proteins that bound selectively to the major brain ganglioside GT1b (GT1b:GM1 > 4; p < 10−4), three regulate neurotransmitter receptor trafficking: Thorase (ATPase family AAA domain-containing protein 1), soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (γ-SNAP), and the transmembrane protein Nicalin. Thorase facilitates endocytosis of GluR2 subunit-containing AMPA-type glutamate receptors (AMPARs) in an ATPase-dependent manner; its deletion in mice results in learning and memory deficits (J. Zhang et al., 2011b). GluR2-containing AMPARs did not bind GT1b, but bound specifically to another ganglioside, GM1. Addition of noncleavable ATP (ATPγS) significantly disrupted ganglioside binding, whereas it enhanced AMPAR association with Thorase, NSF, and Nicalin. Mutant mice lacking GT1b expressed markedly higher brain Thorase, whereas Thorase-null mice expressed higher GT1b. Treatment of cultured hippocampal neurons with sialidase, which cleaves GT1b (and other sialoglycans), resulted in a significant reduction in the size of surface GluR2 puncta. These data support a model in which GM1-bound GluR2-containing AMPARs are functionally segregated from GT1b-bound AMPAR-trafficking complexes. Release of ganglioside binding may enhance GluR2-containing AMPAR association with its trafficking complexes, increasing endocytosis. Disrupting ganglioside biosynthesis may result in reduced synaptic expression of GluR2-contianing AMPARs resulting in intellectual deficits and seizure susceptibility in mice and humans. PMID:25253868

  12. Ganglioside regulation of AMPA receptor trafficking.

    PubMed

    Prendergast, Jillian; Umanah, George K E; Yoo, Seung-Wan; Lagerlöf, Olof; Motari, Mary G; Cole, Robert N; Huganir, Richard L; Dawson, Ted M; Dawson, Valina L; Schnaar, Ronald L

    2014-09-24

    Gangliosides are major cell-surface determinants on all vertebrate neurons. Human congenital disorders of ganglioside biosynthesis invariably result in intellectual disability and are often associated with intractable seizures. To probe the mechanisms of ganglioside functions, affinity-captured ganglioside-binding proteins from rat cerebellar granule neurons were identified by quantitative proteomic mass spectrometry. Of the six proteins that bound selectively to the major brain ganglioside GT1b (GT1b:GM1 > 4; p < 10(-4)), three regulate neurotransmitter receptor trafficking: Thorase (ATPase family AAA domain-containing protein 1), soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (γ-SNAP), and the transmembrane protein Nicalin. Thorase facilitates endocytosis of GluR2 subunit-containing AMPA-type glutamate receptors (AMPARs) in an ATPase-dependent manner; its deletion in mice results in learning and memory deficits (J. Zhang et al., 2011b). GluR2-containing AMPARs did not bind GT1b, but bound specifically to another ganglioside, GM1. Addition of noncleavable ATP (ATPγS) significantly disrupted ganglioside binding, whereas it enhanced AMPAR association with Thorase, NSF, and Nicalin. Mutant mice lacking GT1b expressed markedly higher brain Thorase, whereas Thorase-null mice expressed higher GT1b. Treatment of cultured hippocampal neurons with sialidase, which cleaves GT1b (and other sialoglycans), resulted in a significant reduction in the size of surface GluR2 puncta. These data support a model in which GM1-bound GluR2-containing AMPARs are functionally segregated from GT1b-bound AMPAR-trafficking complexes. Release of ganglioside binding may enhance GluR2-containing AMPAR association with its trafficking complexes, increasing endocytosis. Disrupting ganglioside biosynthesis may result in reduced synaptic expression of GluR2-contianing AMPARs resulting in intellectual deficits and seizure susceptibility in mice and humans.

  13. AMPA receptor/TARP stoichiometry visualized by single-molecule subunit counting.

    PubMed

    Hastie, Peter; Ulbrich, Maximilian H; Wang, Hui-Li; Arant, Ryan J; Lau, Anthony G; Zhang, Zhenjie; Isacoff, Ehud Y; Chen, Lu

    2013-03-26

    Members of the transmembrane AMPA receptor-regulatory protein (TARP) family modulate AMPA receptor (AMPA-R) trafficking and function. AMPA-Rs consist of four pore-forming subunits. Previous studies show that TARPs are an integral part of the AMPA-R complex, acting as accessory subunits for mature receptors in vivo. The TARP/AMPA-R stoichiometry was previously measured indirectly and found to be variable and dependent on TARP expression level, with at most four TARPs associated with each AMPA-R complex. Here, we use a single-molecule technique in live cells that selectively images proteins located in the plasma membrane to directly count the number of TARPs associated with each AMPA-R complex. Although individual GFP-tagged TARP subunits are observed as freely diffusing fluorescent spots on the surface of Xenopus laevis oocytes when expressed alone, coexpression with AMPA-R-mCherry immobilizes the stargazin-GFP spots at sites of AMPA-R-mCherry, consistent with complex formation. We determined the number of TARP molecules associated with each AMPA-R by counting bleaching steps for three different TARP family members: γ-2, γ-3, and γ-4. We confirm that the TARP/AMPA-R stoichiometry depends on TARP expression level and discover that the maximum number of TARPs per AMPA-R complex falls into two categories: up to four γ-2 or γ-3 subunits, but rarely above two for γ-4 subunit. This unexpected AMPA-R/TARP stoichiometry difference has important implications for the assembly and function of TARP/AMPA-R complexes.

  14. SynDIG1 promotes excitatory synaptogenesis independent of AMPA receptor trafficking and biophysical regulation.

    PubMed

    Lovero, Kathryn L; Blankenship, Sabine M; Shi, Yun; Nicoll, Roger A

    2013-01-01

    AMPA receptors-mediators of fast, excitatory transmission and synaptic plasticity in the brain-achieve great functional diversity through interaction with different auxiliary subunits, which alter both the trafficking and biophysical properties of these receptors. In the past several years an abundance of new AMPA receptor auxiliary subunits have been identified, adding astounding variety to the proteins known to directly bind and modulate AMPA receptors. SynDIG1 was recently identified as a novel AMPA receptor interacting protein that directly binds to the AMPA receptor subunit GluA2 in heterologous cells. Functionally, SynDIG1 was found to regulate the strength and density of AMPA receptor containing synapses in hippocampal neurons, though the way in which SynDIG1 exerts these effects remains unknown. Here, we aimed to determine if SynDIG1 acts as a traditional auxiliary subunit, directly regulating the function and localization of AMPA receptors in the rat hippocampus. We find that, unlike any of the previously characterized AMPA receptor auxiliary subunits, SynDIG1 expression does not impact AMPA receptor gating, pharmacology, or surface trafficking. Rather, we show that SynDIG1 regulates the number of functional excitatory synapses, altering both AMPA and NMDA receptor mediated transmission. Our findings suggest that SynDIG1 is not a typical auxiliary subunit to AMPA receptors, but instead is a protein critical to excitatory synaptogenesis.

  15. Effects of cyclothiazide on GluR1/AMPA receptors

    PubMed Central

    Fucile, Sergio; Miledi, Ricardo; Eusebi, Fabrizio

    2006-01-01

    Cyclothiazide (CTZ), a positive allosteric modulator of ionotropic α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors, is used frequently to block the desensitization of both native and heterologously expressed AMPA receptors. Specifically, CTZ is known to produce a fast inhibition of AMPA receptor desensitization and a much slower potentiation of the AMPA current. By using patch-clamp techniques, the effects of CTZ were studied in HEK 293 cells stably transfected with the rat flip GluR1 subunit. Upon CTZ treatment, we found an increased apparent affinity for the agonist, a slow whole-cell current potentiation, a fast inhibition of desensitization, and a lengthening of single-channel openings. Furthermore, we show that CTZ alters the channel gating events modifying the relative contribution of different single-channel classes of conductance (γ), increasing and decreasing, respectively, the contributions of γM (medium) and γL (low) without altering that of the γH (high) conductance channels. We also present a kinetic model that predicts well all of the experimental findings of CTZ action. Finally, we suggest a protocol for standard cell treatment with CTZ to attain maximal efficacy of CTZ on GluR1 receptors. PMID:16473938

  16. Redefining the classification of AMPA-selective ionotropic glutamate receptors

    PubMed Central

    Bowie, Derek

    2012-01-01

    Abstract AMPA-type ionotropic glutamate receptors (iGluRs) represent the major excitatory neurotransmitter receptor in the developing and adult vertebrate CNS. They are crucial for the normal hardwiring of glutamatergic circuits but also fine tune synaptic strength by cycling into and out of synapses during periods of sustained patterned activity or altered homeostasis. AMPARs are grouped into two functionally distinct tetrameric assemblies based on the inclusion or exclusion of the GluA2 receptor subunit. GluA2-containing receptors are thought to be the most abundant AMPAR in the CNS, typified by their small unitary events, Ca2+ impermeability and insensitivity to polyamine block. In contrast, GluA2-lacking AMPARs exhibit large unitary conductance, marked divalent permeability and nano- to micromolar polyamine affinity. Here, I review evidence for the existence of a third class of AMPAR which, though similarly Ca2+ permeable, is characterized by its near-insensitivity to internal and external channel block by polyamines. This novel class of AMPAR is most notably found at multivesicular release synapses found in the avian auditory brainstem and mammalian retina. Curiously, these synapses lack NMDA-type iGluRs, which are conventionally associated with controlling AMPAR insertion. The lack of NMDARs suggests that a different set of rules may govern AMPAR cycling at these synapses. AMPARs with similar functional profiles are also found on some glial cells suggesting they may have a more widespread distribution in the mammalian CNS. I conclude by noting that modest changes to the ion-permeation pathway might be sufficient to retain divalent permeability whilst eliminating polyamine sensitivity. Consequently, this emerging AMPAR subclass need not be assembled from novel subunits, yet to be cloned, but could simply occur by varying the stoichiometry of existing proteins. PMID:22106175

  17. Positive modulation of AMPA receptors increases neurotrophin expression by hippocampal and cortical neurons.

    PubMed

    Lauterborn, J C; Lynch, G; Vanderklish, P; Arai, A; Gall, C M

    2000-01-01

    This study investigated whether positive modulators of AMPA-type glutamate receptors influence neurotrophin expression by forebrain neurons. Treatments with the ampakine CX614 markedly and reversibly increased brain-derived neurotrophic factor (BDNF) mRNA and protein levels in cultured rat entorhinal/hippocampal slices. Acute effects of CX614 were dose dependent over the range in which the drug increased synchronous neuronal discharges; threshold concentrations for acute responses had large effects on mRNA content when applied for 3 d. Comparable results were obtained with a second, structurally distinct ampakine CX546. Ampakine-induced upregulation was broadly suppressed by AMPA, but not NMDA, receptor antagonists and by reducing transmitter release. Antagonism of L-type voltage-sensitive calcium channels blocked induction in entorhinal cortex but not hippocampus. Prolonged infusions of suprathreshold ampakine concentrations produced peak BDNF mRNA levels at 12 hr and a return to baseline levels by 48 hr. In contrast, BDNF protein remained elevated throughout a 48 hr incubation with the drug. Nerve growth factor mRNA levels also were increased by ampakines but with a much more rapid return to control levels during chronic administration. Finally, intraperitoneal injections of CX546 increased hippocampal BDNF mRNA levels in aged rats and middle-aged mice. The present results provide evidence of regional differences in mechanisms via which activity regulates neurotrophin expression. Moreover, these data establish that changes in synaptic potency produce sufficient network level physiological effects for inducing neurotrophin genes, indicate that the response becomes refractory during prolonged ampakine exposure, and raise the possibility of using positive AMPA modulators to regulate neurotrophin levels in aged brain.

  18. Acute Footshock Stress Induces Time-Dependent Modifications of AMPA/NMDA Protein Expression and AMPA Phosphorylation.

    PubMed

    Bonini, Daniela; Mora, Cristina; Tornese, Paolo; Sala, Nathalie; Filippini, Alice; La Via, Luca; Milanese, Marco; Calza, Stefano; Bonanno, Gianbattista; Racagni, Giorgio; Gennarelli, Massimo; Popoli, Maurizio; Musazzi, Laura; Barbon, Alessandro

    2016-01-01

    Clinical studies on patients with stress-related neuropsychiatric disorders reported functional and morphological changes in brain areas where glutamatergic transmission is predominant, including frontal and prefrontal areas. In line with this evidence, several preclinical works suggest that glutamate receptors are targets of both rapid and long-lasting effects of stress. Here we found that acute footshock- (FS-) stress, although inducing no transcriptional and RNA editing alterations of ionotropic AMPA and NMDA glutamate receptor subunits, rapidly and transiently modulates their protein expression, phosphorylation, and localization at postsynaptic spines in prefrontal and frontal cortex. In total extract, FS-stress increased the phosphorylation levels of GluA1 AMPA subunit at Ser(845) immediately after stress and of GluA2 Ser(880) 2 h after start of stress. At postsynaptic spines, stress induced a rapid decrease of GluA2 expression, together with an increase of its phosphorylation at Ser(880), suggesting internalization of GluA2 AMPA containing receptors. GluN1 and GluN2A NMDA receptor subunits were found markedly upregulated in postsynaptic spines, 2 h after start of stress. These results suggest selected time-dependent changes in glutamatergic receptor subunits induced by acute stress, which may suggest early and transient enhancement of AMPA-mediated currents, followed by a transient activation of NMDA receptors.

  19. Acute Footshock Stress Induces Time-Dependent Modifications of AMPA/NMDA Protein Expression and AMPA Phosphorylation

    PubMed Central

    Bonini, Daniela; Mora, Cristina; Tornese, Paolo; Sala, Nathalie; Filippini, Alice; La Via, Luca; Milanese, Marco; Calza, Stefano; Bonanno, Gianbattista; Racagni, Giorgio; Gennarelli, Massimo; Popoli, Maurizio; Musazzi, Laura; Barbon, Alessandro

    2016-01-01

    Clinical studies on patients with stress-related neuropsychiatric disorders reported functional and morphological changes in brain areas where glutamatergic transmission is predominant, including frontal and prefrontal areas. In line with this evidence, several preclinical works suggest that glutamate receptors are targets of both rapid and long-lasting effects of stress. Here we found that acute footshock- (FS-) stress, although inducing no transcriptional and RNA editing alterations of ionotropic AMPA and NMDA glutamate receptor subunits, rapidly and transiently modulates their protein expression, phosphorylation, and localization at postsynaptic spines in prefrontal and frontal cortex. In total extract, FS-stress increased the phosphorylation levels of GluA1 AMPA subunit at Ser845 immediately after stress and of GluA2 Ser880 2 h after start of stress. At postsynaptic spines, stress induced a rapid decrease of GluA2 expression, together with an increase of its phosphorylation at Ser880, suggesting internalization of GluA2 AMPA containing receptors. GluN1 and GluN2A NMDA receptor subunits were found markedly upregulated in postsynaptic spines, 2 h after start of stress. These results suggest selected time-dependent changes in glutamatergic receptor subunits induced by acute stress, which may suggest early and transient enhancement of AMPA-mediated currents, followed by a transient activation of NMDA receptors. PMID:26966584

  20. AMPA receptor trafficking and the mechanisms underlying synaptic plasticity and cognitive aging.

    PubMed

    Henley, Jeremy M; Wilkinson, Kevin A

    2013-03-01

    Even in healthy individuals there is an inexorable agerelated decline in cognitive function. This is due, in large part, to reduced synaptic plasticity caused by changes in the molecular composition of the postsynaptic membrane. AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate the overwhelming majority of fast excitatory transmission in the brain. Changes in AMPAR number and/or function are a core feature of synaptic plasticity and age-related cognitive decline, AMPARs are highly dynamic proteins that are subject to highly controlled trafficking, recycling, and/or degradation and replacement. This active regulation of AMPAR synthesis, targeting, synaptic dwell time, and degradation is fundamentally important for memory formation and storage. Further, aberrant AMPAR trafficking and consequent detrimental changes in synapses are strongly implicated in many brain diseases, which represent a vast social and economic burden. The purpose of this article is to provide an overview of the molecular and cellular AMPA receptor trafficking events that control synaptic responsiveness and plasticity, and highlight what is known currently known about how these processes change with age and disease.

  1. AMPA receptors in post-mortem brains of Cloninger type 1 and 2 alcoholics: a whole-hemisphere autoradiography study.

    PubMed

    Kärkkäinen, Olli; Kupila, Jukka; Häkkinen, Merja; Laukkanen, Virpi; Tupala, Erkki; Kautiainen, Hannu; Tiihonen, Jari; Storvik, Markus

    2013-12-30

    Dysfunction of the brain glutamate system has been associated with alcoholism. Ionotropic glutamatergic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) play an important role in both neurotransmission and post-synaptic plasticity. Alterations in AMPAR densities may also play a role in the neurobiological changes associated with alcoholism. In the present study, [(3)H] AMPA binding density was evaluated in the nucleus accumbens (NAc), frontal cortex, anterior cingulate cortex (ACC), dentate gyrus and hippocampus of Cloninger type 1 (n=9) and 2 (n=8) alcoholics, and compared with non-alcoholic control subjects (n=10) by post-mortem whole-hemisphere autoradiography. The [(3)H] AMPA binding density was significantly higher in the ACC of early onset type 2 alcoholics when compared with controls (p=0.011). There was also a significant negative correlation between [(3)H] AMPA binding and previously published results of dopamine transporter (DAT) density in the ACC in these same brain samples (R=-0.95, p=0.001). Although preliminary, and from a relatively small diagnostic group, the present results help to further explain the pathology of alcohol dependence and impulsive behaviour in type 2 alcoholics.

  2. [Reciprocal suppression of the AMPA and NMDA components of the excitatory postsynaptic potentials in the CA1 area of the rat hippocampus in vitro].

    PubMed

    Bazhenov, A V; Kleshchevnikov, A M

    1998-01-01

    The interaction between N-methyl-d-aspartate (NMDA)- and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-dependent components of excitatory postsynaptic potentials (EPSP) was studied in rat hippocampal slices. Responses evoked by stimulation of the collateral commissural fibers were recorded in the radial layer of the CA1 area. Contribution of the NMDA component was changed by application of solutions with different concentrations of magnesium. In solutions with low magnesium concentration, when both AMPA and NMDA components contribute significantly to EPSP, suppression of one of the components by application of selective antagonist resulted in increase in the area of another component. Thus, the sum of pharmacologically isolated AMPA and NMDA components was significantly higher than the control EPSP. For example, at 0.1 mM of magnesium in the extracellular solution the sum of the components was 340 +/- 120% of the control EPSP (p < 0.01, N = 6). The data imply that under the control conditions the EPSP components suppress each other. The mutual suppression of the AMPA and NMDA component of the EPSP can be an important factor which influences the conductivity and plastic properties of central glutamatergic synaptic pathways.

  3. The AMPA receptor subunit GluR1 regulates dendritic architecture of motor neurons

    NASA Technical Reports Server (NTRS)

    Inglis, Fiona M.; Crockett, Richard; Korada, Sailaja; Abraham, Wickliffe C.; Hollmann, Michael; Kalb, Robert G.

    2002-01-01

    The morphology of the mature motor neuron dendritic arbor is determined by activity-dependent processes occurring during a critical period in early postnatal life. The abundance of the AMPA receptor subunit GluR1 in motor neurons is very high during this period and subsequently falls to a negligible level. To test the role of GluR1 in dendrite morphogenesis, we reintroduced GluR1 into rat motor neurons at the end of the critical period and quantitatively studied the effects on dendrite architecture. Two versions of GluR1 were studied that differed by the amino acid in the "Q/R" editing site. The amino acid occupying this site determines single-channel conductance, ionic permeability, and other essential electrophysiologic properties of the resulting receptor channels. We found large-scale remodeling of dendritic architectures in a manner depending on the amino acid occupying the Q/R editing site. Alterations in the distribution of dendritic arbor were not prevented by blocking NMDA receptors. These observations suggest that the expression of GluR1 in motor neurons modulates a component of the molecular substrate of activity-dependent dendrite morphogenesis. The control of these events relies on subunit-specific properties of AMPA receptors.

  4. Amyloid-β-Induced Dysregulation of AMPA Receptor Trafficking

    PubMed Central

    Guntupalli, Sumasri; Widagdo, Jocelyn; Anggono, Victor

    2016-01-01

    Evidence from neuropathological, genetic, animal model, and biochemical studies has indicated that the accumulation of amyloid-beta (Aβ) is associated with, and probably induces, profound neuronal changes in brain regions critical for memory and cognition in the development of Alzheimer's disease (AD). There is considerable evidence that synapses are particularly vulnerable to AD, establishing synaptic dysfunction as one of the earliest events in pathogenesis, prior to neuronal loss. It is clear that excessive Aβ levels can disrupt excitatory synaptic transmission and plasticity, mainly due to dysregulation of the AMPA and NMDA glutamate receptors in the brain. Importantly, AMPA receptors are the principal glutamate receptors that mediate fast excitatory neurotransmission. This is essential for synaptic plasticity, a cellular correlate of learning and memory, which are the cognitive functions that are most disrupted in AD. Here we review recent advances in the field and provide insights into the molecular mechanisms that underlie Aβ-induced dysfunction of AMPA receptor trafficking. This review focuses primarily on NMDA receptor- and metabotropic glutamate receptor-mediated signaling. In particular, we highlight several mechanisms that underlie synaptic long-term depression as common signaling pathways that are hijacked by the neurotoxic effects of Aβ. PMID:27073700

  5. AMPA receptor potentiation can prevent ethanol-induced intoxication.

    PubMed

    Jones, Nicholas; Messenger, Marcus J; O'Neill, Michael J; Oldershaw, Anna; Gilmour, Gary; Simmons, Rosa M A; Iyengar, Smriti; Libri, Vincenzo; Tricklebank, Mark; Williams, Steve C R

    2008-06-01

    We present a substantial series of behavioral and imaging experiments, which demonstrate, for the first time, that increasing AMPA receptor-mediated neurotransmission via administration of potent and selective biarylsulfonamide AMPA potentiators LY404187 and LY451395 reverses the central effects of an acutely intoxicating dose of ethanol in the rat. Using pharmacological magnetic resonance imaging (phMRI), we observed that LY404187 attenuated ethanol-induced reductions in blood oxygenation level dependent (BOLD) in the anesthetized rat brain. A similar attenuation was apparent when measuring local cerebral glucose utilization (LCGU) via C14-2-deoxyglucose autoradiography in freely moving conscious rats. Both LY404187 and LY451395 significantly and dose-dependently reversed ethanol-induced deficits in both motor coordination and disruptions in an operant task where animals were trained to press a lever for food reward. Both prophylactic and acute intervention treatment with LY404187 reversed ethanol-induced deficits in motor coordination. Given that LY451395 and related AMPA receptor potentiators/ampakines are tolerated in both healthy volunteers and elderly patients, these data suggest that such compounds may form a potential management strategy for acute alcohol intoxication.

  6. TARP γ-8 glycosylation regulates the surface expression of AMPA receptors.

    PubMed

    Zheng, Chan-Ying; Chang, Kai; Suh, Young Ho; Roche, Katherine W

    2015-02-01

    TARP [transmembrane AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor regulatory protein] γ-8 is an auxiliary subunit of AMPA receptors that is widely distributed in the hippocampus. It has been shown that TARP γ-8 promotes surface expression of AMPA receptors; however, how TARP γ-8 regulates the expression of AMPA receptors remains unclear. In the present study, we examined the effect of TARP glycosylation on AMPA receptor trafficking. We first showed that TARP γ-8 is an N-glycosylated protein, which contains two glycosylation sites, Asn53 and Asn56, and compared this with the glycosylation of TARP γ-2 and the AMPA receptor auxiliary protein CNIH-2 (cornichon homologue 2). We next examine the effect of TARP glycosylation on TARP trafficking and also on AMPA receptor surface expression. We find that TARP γ-8 glycosylation is critical for surface expression of both TARP γ-8 and GluA1 in heterologous cells and neurons. Specifically, knockdown of TARP γ-8 causes a decrease in both total and surface AMPA receptors. We find that the expression of unglycosylated TARP γ-8 in cultured neurons is unable to restore GluA1 expression fully. Furthermore, when the maturation of TARP γ-8 is impaired, a large pool of immature GluA1 is retained intracellularly. Taken together, our data reveal an important role for the maturation of TARP γ-8 in the trafficking and function of the AMPA receptor complex.

  7. Activity Level-Dependent Synapse-Specific AMPA Receptor Trafficking Regulates Transmission Kinetics

    PubMed Central

    Zhu, J. Julius

    2009-01-01

    Central glutamatergic synapses may express AMPA-sensitive glutamate receptors (AMPA-Rs) with distinct gating properties and exhibit different transmission dynamics, which are important for computing various synaptic inputs received at different populations of synapses. However, how glutamatergic synapses acquire AMPA-Rs with distinct kinetics to influence synaptic integration remains poorly understood. Here I report synapse-specific trafficking of distinct AMPA-Rs in rat cortical layer 4 stellate and layer 5 pyramidal neurons. The analysis indicates that in single layer 4 stellate neurons thalamocortical synapses generate faster synaptic responses than intracortical synapses. Moreover, GluR1-containing AMPA-Rs traffic selectively into intracortical synapses, and this process requires sensory experience-dependent activity and slows down transmission kinetics. GluR4-containing AMPA-Rs traffic more heavily into thalamocortical synapses than intracortical synapses, and this process requires spontaneous synaptic activity and speeds up transmission kinetics. GluR2-containing AMPA-Rs traffic equally into both thalamocortical and intracortical synapses, and this process requires no synaptic activity and resets transmission kinetics. Notably, synaptic trafficking of distinct AMPA-Rs differentially regulates synaptic integration. Thus, synapse-specific AMPA-R trafficking coarsely sets and synaptic activity finely tunes transmission kinetics and integration properties at different synapses in central neurons. PMID:19439609

  8. Identification and Characterization of RNA Aptamers: A Long Aptamer Blocks the AMPA Receptor and a Short Aptamer Blocks Both AMPA and Kainate Receptors.

    PubMed

    Jaremko, William J; Huang, Zhen; Wen, Wei; Wu, Andrew; Karl, Nicholas; Niu, Li

    2017-03-21

    AMPA and kainate receptors, along with NMDA receptors, represent different subtypes of glutamate ion channels. AMPA and kainate receptors share a high degree of sequence and structural similarities, and excessive activity of these receptors has been implicated in neurological diseases such as epilepsy. Therefore, blocking detrimental activity of both receptor types could be therapeutically beneficial. Here, we report the use of an in vitro evolution approach involving systematic evolution of ligands by exponential enrichment with a single AMPA receptor target (i.e. GluA1/2R) to isolate RNA aptamers that can potentially inhibit both AMPA and kainate receptors. A full-length or 101-nucleotide (nt) aptamer selectively inhibited GluA1/2R with a KI of ~5 µM, along with GluA1 and GluA2 AMPA receptor subunits. Of note, its shorter version (55 nt) inhibited both AMPA and kainate receptors. In particular, this shorter aptamer blocked equally potently the activity of both the GluK1 and GluK2 kainate receptors. Using homologous binding and whole-cell recording assays, we found that an RNA aptamer most likely binds to the receptor's regulatory site and inhibits it noncompetitively. Our results suggest the potential of using a single receptor target to develop RNA aptamers with dual activity for effectively blocking both AMPA and kainate receptors.

  9. Discovery of the First α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Antagonist Dependent upon Transmembrane AMPA Receptor Regulatory Protein (TARP) γ-8.

    PubMed

    Gardinier, Kevin M; Gernert, Douglas L; Porter, Warren J; Reel, Jon K; Ornstein, Paul L; Spinazze, Patrick; Stevens, F Craig; Hahn, Patric; Hollinshead, Sean P; Mayhugh, Daniel; Schkeryantz, Jeff; Khilevich, Albert; De Frutos, Oscar; Gleason, Scott D; Kato, Akihiko S; Luffer-Atlas, Debra; Desai, Prashant V; Swanson, Steven; Burris, Kevin D; Ding, Chunjin; Heinz, Beverly A; Need, Anne B; Barth, Vanessa N; Stephenson, Gregory A; Diseroad, Benjamin A; Woods, Tim A; Yu, Hong; Bredt, David; Witkin, Jeffrey M

    2016-05-26

    Transmembrane AMPA receptor regulatory proteins (TARPs) are a family of scaffolding proteins that regulate AMPA receptor trafficking and function. TARP γ-8 is one member of this family and is highly expressed within the hippocampus relative to the cerebellum. A selective TARP γ-8-dependent AMPA receptor antagonist (TDAA) is an innovative approach to modulate AMPA receptors in specific brain regions to potentially increase the therapeutic index relative to known non-TARP-dependent AMPA antagonists. We describe here, for the first time, the discovery of a noncompetitive AMPA receptor antagonist that is dependent on the presence of TARP γ-8. Three major iteration cycles were employed to improve upon potency, CYP1A2-dependent challenges, and in vivo clearance. An optimized molecule, compound (-)-25 (LY3130481), was fully protective against pentylenetetrazole-induced convulsions in rats without the motor impairment associated with non-TARP-dependent AMPA receptor antagonists. Compound (-)-25 could be utilized to provide proof of concept for antiepileptic efficacy with reduced motor side effects in patients.

  10. Forebrain-selective AMPA-receptor antagonism guided by TARP γ-8 as an antiepileptic mechanism.

    PubMed

    Kato, Akihiko S; Burris, Kevin D; Gardinier, Kevin M; Gernert, Douglas L; Porter, Warren J; Reel, Jon; Ding, Chunjin; Tu, Yuan; Schober, Douglas A; Lee, Matthew R; Heinz, Beverly A; Fitch, Thomas E; Gleason, Scott D; Catlow, John T; Yu, Hong; Fitzjohn, Stephen M; Pasqui, Francesca; Wang, He; Qian, Yuewei; Sher, Emanuele; Zwart, Ruud; Wafford, Keith A; Rasmussen, Kurt; Ornstein, Paul L; Isaac, John T R; Nisenbaum, Eric S; Bredt, David S; Witkin, Jeffrey M

    2016-12-01

    Pharmacological manipulation of specific neural circuits to optimize therapeutic index is an unrealized goal in neurology and psychiatry. AMPA receptors are important for excitatory synaptic transmission, and their antagonists are antiepileptic. Although efficacious, AMPA-receptor antagonists, including perampanel (Fycompa), the only approved antagonist for epilepsy, induce dizziness and motor impairment. We hypothesized that blockade of forebrain AMPA receptors without blocking cerebellar AMPA receptors would be antiepileptic and devoid of motor impairment. Taking advantage of an AMPA receptor auxiliary protein, TARP γ-8, which is selectively expressed in the forebrain and modulates the pharmacological properties of AMPA receptors, we discovered that LY3130481 selectively antagonized recombinant and native AMPA receptors containing γ-8, but not γ-2 (cerebellum) or other TARP members. Two amino acid residues unique to γ-8 determined this selectivity. We also observed antagonism of AMPA receptors expressed in hippocampal, but not cerebellar, tissue from an patient with epilepsy. Corresponding to this selective activity, LY3130481 prevented multiple seizure types in rats and mice and without motor side effects. These findings demonstrate the first rationally discovered molecule targeting specific neural circuitries for therapeutic advantage.

  11. Insulin inhibits AMPA-induced neuronal damage via stimulation of protein kinase B (Akt).

    PubMed

    Kim, S-J; Han, Y

    2005-02-01

    We designed a series of experiments to explore the neuroprotective effects of insulin. Insulin significantly inhibited the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-induced neuronal cell damage as evidenced by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay. However, insulin had little affect on the AMPA-induced glial cell damage. To determine whether insulin inhibits AMPA-induced excitotoxicity, we performed grease-gap recording assays using rat brain slices. In these experiments, insulin also significantly inhibited AMPA-induced depolarization. Flow cytometry and DNA fragmentation assays showed that insulin inhibits AMPA-induced apoptosis and DNA fragmentation, respectively. Insulin stimulated protein kinase B (Akt) activity, whereas AMPA pretreatment did not alter the insulin-stimulated Akt activity. On the contrary, insulin blocked induction of SAPK/JNK, which AMPA stimulated. Taken together, these results suggest that insulin exerts neuroprotective effects by inhibiting AMPA-induced excitotoxicity and apoptosis, possibly by activating Akt and blocking SAPK/JNK.

  12. Afferent-specific innervation of two distinct AMPA receptor subtypes on single hippocampal interneurons.

    PubMed

    Tóth, K; McBain, C J

    1998-11-01

    Using the polyamine toxin philanthotoxin, which selectively blocks calcium-permeable AMPA receptors, we show that synaptic transmission onto single hippocampal interneurons occurs by afferent-specific activation of philanthotoxin-sensitive and -insensitive AMPA receptors. Calcium-permeable AMPA receptors are found exclusively at synapses from mossy fibers. In contrast, synaptic responses evoked by stimulation of CA3 pyramidal neurons are mediated by calcium-impermeable AMPA receptors. Both pathways converge onto single interneurons and can be discriminated with Group II mGluR agonists. Thus, single interneurons target AMPA receptors of different subunit composition to specific postsynaptic sites, providing a mechanism to increase the synapse-specific computational properties of hippocampal interneurons.

  13. The SOL-2/Neto auxiliary protein modulates the function of AMPA-subtype ionotropic glutamate receptors.

    PubMed

    Wang, Rui; Mellem, Jerry E; Jensen, Michael; Brockie, Penelope J; Walker, Craig S; Hoerndli, Frédéric J; Hauth, Linda; Madsen, David M; Maricq, Andres V

    2012-09-06

    The neurotransmitter glutamate mediates excitatory synaptic transmission by gating ionotropic glutamate receptors (iGluRs). AMPA receptors (AMPARs), a subtype of iGluR, are strongly implicated in synaptic plasticity, learning, and memory. We previously discovered two classes of AMPAR auxiliary proteins in C. elegans that modify receptor kinetics and thus change synaptic transmission. Here, we have identified another auxiliary protein, SOL-2, a CUB-domain protein that associates with both the related auxiliary subunit SOL-1 and with the GLR-1 AMPAR. In sol-2 mutants, behaviors dependent on glutamatergic transmission are disrupted, GLR-1-mediated currents are diminished, and GLR-1 desensitization and pharmacology are modified. Remarkably, a secreted variant of SOL-1 delivered in trans can rescue sol-1 mutants, and this rescue depends on in cis expression of SOL-2. Finally, we demonstrate that SOL-1 and SOL-2 have an ongoing role in the adult nervous system to control AMPAR-mediated currents.

  14. Glyphosate and AMPA inhibit cancer cell growth through inhibiting intracellular glycine synthesis.

    PubMed

    Li, Qingli; Lambrechts, Mark J; Zhang, Qiuyang; Liu, Sen; Ge, Dongxia; Yin, Rutie; Xi, Mingrong; You, Zongbing

    2013-01-01

    Glycine is a nonessential amino acid that is reversibly converted from serine intracellularly by serine hydroxymethyltransferase. Glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), are analogs to glycine, thus they may inhibit serine hydroxymethyltransferase to decrease intracellular glycine synthesis. In this study, we found that glyphosate and AMPA inhibited cell growth in eight human cancer cell lines but not in two immortalized human normal prostatic epithelial cell lines. AMPA arrested C4-2B and PC-3 cancer cells in the G1/G0 phase and inhibited entry into the S phase of the cell cycle. AMPA also promoted apoptosis in C4-2B and PC-3 cancer cell lines. AMPA upregulated p53 and p21 protein levels as well as procaspase 9 protein levels in C4-2B cells, whereas it downregulated cyclin D3 protein levels. AMPA also activated caspase 3 and induced cleavage of poly (adenosine diphosphate [ADP]-ribose) polymerase. This study provides the first evidence that glyphosate and AMPA can inhibit proliferation and promote apoptosis of cancer cells but not normal cells, suggesting that they have potentials to be developed into a new anticancer therapy.

  15. Urban and agricultural contribution of annual loads of glyphosate and AMPA towards surface waters at the Orge River catchment scale (France)

    NASA Astrophysics Data System (ADS)

    Botta, Fabrizio; Chevreuil, Marc; Blanchoud, Hélène

    2010-05-01

    The general use of pesticides in the Orge Basin, located in the southern part of the Paris suburb (France), is damaging surface water quality. Consequently, an increase in the water supply costs is registered by the water supply agencies that are situated downstream the Orge confluence with the Seine River. In this catchment, high uses of glyphosate are registered for fallow fields (upstream part) and for roadway weed control (downstream part). The proportion of glyphosate coming from these two zones was not well known, along with the double source of its metabolite AMPA originated from the degradation of some detergent phosphonates. The aim of this work was firstly to identify the potential sources of glyphosate and AMPA in urban sectors (such as sewerage system inputs) and in agricultural areas and to quantify the origins of urban pesticides pathways towards surface waters at the basin scale. The new approach of this project was to collect information at three different scales to establish a first step of modeling. At the basin scale, 1 year of surface water monitoring at the outlet of the Orge River was useful to establish the inputs towards the Seine River. At the urban catchment scale, the investigations have permitted to record glyphosate and AMPA loads transferred by storm waters and by wastewaters. Loads were estimated during and out of application calendar, in different hydrological conditions such as rainfall with high intensity or dry conditions. Impact of WWTP on surface water was also demonstrated. The third phase of this work was the interpretation of agricultural inputs from two different agricultural catchments of the Orge River. The results showed the impact of urban uses of glyphosate upon the Orge River contamination with annual loads from 100 times higher from the urban zone than from the agricultural one. Storm sewers were recognized to be the main way for glyphosate transfer towards surface waters. A budget of glyphosate and AMPA inputs and

  16. AMPA Receptors Are Involved in Store-Operated Calcium Entry and Interact with STIM Proteins in Rat Primary Cortical Neurons

    PubMed Central

    Gruszczynska-Biegala, Joanna; Sladowska, Maria; Kuznicki, Jacek

    2016-01-01

    The process of store-operated calcium entry (SOCE) leads to refilling the endoplasmic reticulum (ER) with calcium ions (Ca2+) after their release into the cytoplasm. Interactions between (ER)-located Ca2+ sensors (stromal interaction molecule 1 [STIM1] and STIM2) and plasma membrane-located Ca2+ channel-forming protein (Orai1) underlie SOCE and are well described in non-excitable cells. In neurons, however, SOCE appears to be more complex because of the importance of Ca2+ influx via voltage-gated or ionotropic receptor-operated Ca2+ channels. We found that the SOCE inhibitors ML-9 and SKF96365 reduced α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-induced [Ca2+]i amplitude by 80% and 53%, respectively. To assess the possible involvement of AMPA receptors (AMPARs) in SOCE, we used their specific inhibitors. As estimated by Fura-2 acetoxymethyl (AM) single-cell Ca2+ measurements in the presence of CNQX or NBQX, thapsigargin (TG)-induced Ca2+ influx decreased 2.2 or 3.7 times, respectively. These results suggest that under experimental conditions of SOCE when Ca2+ stores are depleted, Ca2+ can enter neurons also through AMPARs. Using specific antibodies against STIM proteins or GluA1/GluA2 AMPAR subunits, co-immunoprecipitation assays indicated that when Ca2+ levels are low in the neuronal ER, a physical association occurs between endogenous STIM proteins and endogenous AMPAR receptors. Altogether, our data suggest that STIM proteins in neurons can control AMPA-induced Ca2+ entry as a part of the mechanism of SOCE. PMID:27826230

  17. Alternative Splicing of AMPA Subunits in Prefrontal Cortical Fields of Cynomolgus Monkeys Following Chronic Ethanol Self-Administration

    PubMed Central

    Acosta, Glen; Freidman, David P.; Grant, Kathleen A.; Hemby, Scott E.

    2012-01-01

    Functional impairment of the orbital and medial prefrontal cortex underlies deficits in executive control that characterize addictive disorders, including alcohol addiction. Previous studies indicate that alcohol alters glutamate neurotransmission and one substrate of these effects may be through the reconfiguration of the subunits constituting ionotropic glutamate receptor (iGluR) complexes. Glutamatergic transmission is integral to cortico-cortical and cortico-subcortical communication and alcohol-induced changes in the abundance of the receptor subunits and/or their splice variants may result in critical functional impairments of prefrontal cortex in alcohol dependence. To this end, the effects of chronic ethanol self-administration on glutamate receptor ionotropic AMPA (GRIA) subunit variant and kainate (GRIK) subunit mRNA expression were studied in the orbitofrontal cortex (OFC), dorsolateral prefrontal cortex (DLPFC), and anterior cingulate cortex (ACC) of male cynomolgus monkeys. In DLPFC, total AMPA splice variant expression and total kainate receptor subunit expression were significantly decreased in alcohol drinking monkeys. Expression levels of GRIA3 flip and flop and GRIA4 flop mRNAs in this region were positively correlated with daily ethanol intake and blood ethanol concentrations (BEC) averaged over the 6 months prior to necropsy. In OFC, AMPA subunit splice variant expression was reduced in the alcohol treated group. GRIA2 flop mRNA levels in this region were positively correlated with daily ethanol intake and BEC averaged over the 6 months prior to necropsy. Results from these studies provide further evidence of transcriptional regulation of iGluR subunits in the primate brain following chronic alcohol self-administration. Additional studies examining the cellular localization of such effects in the framework of primate prefrontal cortical circuitry are warranted. PMID:22291662

  18. Chemical labelling for visualizing native AMPA receptors in live neurons.

    PubMed

    Wakayama, Sho; Kiyonaka, Shigeki; Arai, Itaru; Kakegawa, Wataru; Matsuda, Shinji; Ibata, Keiji; Nemoto, Yuri L; Kusumi, Akihiro; Yuzaki, Michisuke; Hamachi, Itaru

    2017-04-07

    The location and number of neurotransmitter receptors are dynamically regulated at postsynaptic sites. However, currently available methods for visualizing receptor trafficking require the introduction of genetically engineered receptors into neurons, which can disrupt the normal functioning and processing of the original receptor. Here we report a powerful method for visualizing native α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) which are essential for cognitive functions without any genetic manipulation. This is based on a covalent chemical labelling strategy driven by selective ligand-protein recognition to tether small fluorophores to AMPARs using chemical AMPAR modification (CAM) reagents. The high penetrability of CAM reagents enables visualization of native AMPARs deep in brain tissues without affecting receptor function. Moreover, CAM reagents are used to characterize the diffusion dynamics of endogenous AMPARs in both cultured neurons and hippocampal slices. This method will help clarify the involvement of AMPAR trafficking in various neuropsychiatric and neurodevelopmental disorders.

  19. AMPA receptor potentiators: from drug design to cognitive enhancement.

    PubMed

    Partin, Kathryn M

    2015-02-01

    Positive allosteric modulators of ionotropic glutamate receptors have emerged as a target for treating cognitive impairment and neurodegeneration, but also mental illnesses such as major depressive disorder. The possibility of creating a new class of pharmaceutical agent to treat refractive mental health issues has compelled researchers to redouble their efforts to develop a safe, effective treatment for memory and cognition impairments. Coupled with the more robust research methodologies that have emerged, including more sophisticated high-throughput-screens, higher resolution structural biology techniques, and more focused assessment on pharmacokinetics, the development of positive modulators of AMPA receptors holds great promise. We describe recent approaches that improve our understanding of the basic physiology underlying memory and cognition, and their application toward promoting human health.

  20. AMPA RECEPTOR POTENTIATORS: FROM DRUG DESIGN TO COGNITIVE ENHANCEMENT

    PubMed Central

    PARTIN, KATHRYN M.

    2014-01-01

    Positive allosteric modulators of ionotropic glutamate receptors have emerged as a target for treating cognitive impairment and neurodegeneration, but also mental illnesses such as major depressive disorder. The possibility of creating a new class of pharmaceutical agent to treat refractive mental health issues has compelled researchers to redouble their efforts to develop a safe, effective treatment for memory and cognition impairments. Coupled with the more robust research methodologies that have emerged, including more sophisticated high-throughput-screens, higher resolution structural biology techniques, and more focused assessment on pharmacokinetics, the development of positive modulators of AMPA receptors holds great promise. We describe recent approaches that improve our understanding of the basic physiology underlying memory and cognition, and their application towards promoting human health. PMID:25462292

  1. 3’-Deoxyadenosine (Cordycepin) Produces a Rapid and Robust Antidepressant Effect via Enhancing Prefrontal AMPA Receptor Signaling Pathway

    PubMed Central

    Li, Bai; Hou, Yangyang; Zhu, Ming; Bao, Hongkun; Nie, Jun; Zhang, Grace Y.; Shan, Liping; Yao, Yao; Du, Kai; Yang, Hongju; Li, Meizhang; Zheng, Bingrong; Xu, Xiufeng; Xiao, Chunjie; Du, Jing

    2016-01-01

    Background: The development of rapid and safe antidepressants for the treatment of major depression is in urgent demand. Converging evidence suggests that glutamatergic signaling seems to play important roles in the pathophysiology of depression. Methods: We studied the antidepressant effects of 3’-deoxyadenosine (3’-dA, Cordycepin) and the critical role of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor in male CD-1 mice via behavioral and biochemical experiments. After 3’-dA treatment, the phosphorylation and synaptic localization of the AMPA receptors GluR1 and GluR2 were determined in the prefrontal cortex (PFC) and hippocampus (HIP). The traditional antidepressant imipramine was applied as a positive control. Results: We found that an injection of 3’-dA led to a rapid and robust antidepressant effect, which was significantly faster and stronger than imipramine, after 45min in tail suspension and forced swim tests. This antidepressant effect remained after 5 days of treatment with 3’-dA. Unlike the psycho-stimulants, 3’-dA did not show a hyperactive effect in the open field test. After 45min or 5 days of treatment, 3’-dA enhanced GluR1 S845 phosphorylation in both the PFC and HIP. In addition, after 45min of treatment, 3’-dA significantly up-regulated GluR1 S845 phosphorylation and GluR1, but not GluR2 levels, at the synapses in the PFC. After 5 days of treatment, 3’-dA significantly enhanced GluR1 S845 phosphorylation and GluR1, but not GluR2, at the synapses in the PFC and HIP. Moreover, the AMPA-specific antagonist GYKI 52466 was able to block the rapid antidepressant effects of 3’-dA. Conclusion: This study identified 3’-dA as a novel rapid antidepressant with clinical potential and multiple beneficial mechanisms, particularly in regulating the prefrontal AMPA receptor signaling pathway. PMID:26443809

  2. Prenatal nicotine is associated with reduced AMPA and NMDA receptor-mediated rises in calcium within the laterodorsal tegmentum: a pontine nucleus involved in addiction processes.

    PubMed

    McNair, L F; Kohlmeier, K A

    2015-06-01

    Despite huge efforts from public sectors to educate society as to the deleterious physiological consequences of smoking while pregnant, 12-25% of all babies worldwide are born to mothers who smoked during their pregnancies. Chief among the negative legacies bestowed to the exposed individual is an enhanced proclivity postnatally to addict to drugs of abuse, which suggests that the drug exposure during gestation changed the developing brain in such a way that biased it towards addiction. Glutamate signalling has been shown to be altered by prenatal nicotine exposure (PNE) and glutamate is the major excitatory neurotransmitter within the laterodorsal tegmental nucleus (LDT), which is a brainstem region importantly involved in responding to motivational stimuli and critical in development of drug addiction-associated behaviours, however, it is unknown whether PNE alters glutamate signalling within this nucleus. Accordingly, we used calcium imaging, to evaluate AMPA and NMDA receptor-mediated calcium responses in LDT brain slices from control and PNE mice. We also investigated whether the positive AMPA receptor modulator cyclothiazide (CYZ) had differential actions on calcium in the LDT following PNE. Our data indicated that PNE significantly decreased AMPA receptor-mediated calcium responses, and altered the neuronal calcium response to consecutive NMDA applications within the LDT. Furthermore, CYZ strongly potentiated AMPA-induced responses, however, this action was significantly reduced in the LDT of PNE mice when compared with enhancements in responses in control LDT cells. Immunohistochemical processing confirmed that calcium imaging recordings were obtained from the LDT nucleus as determined by presence of cholinergic neurons. Our results contribute to the body of evidence suggesting that neurobiological changes are induced if gestation is accompanied by nicotine exposure. We conclude that in light of the role played by the LDT in motivated behaviour, the

  3. Glyphosate and AMPA in the estuaries of the Baltic Sea method optimization and field study.

    PubMed

    Skeff, Wael; Neumann, Christine; Schulz-Bull, Detlef E

    2015-11-15

    Water samples from ten German Baltic estuaries were collected in 2012 in order to study the presence of the herbicide glyphosate, its primary metabolite AMPA and their potential transport to the marine environment. For the analyses an LC-MS/MS based analytical method after derivatization with FMOC-Cl was optimized and validated for marine water samples. All investigated estuarine stations were contaminated with AMPA and nine of them also with glyphosate. Concentration ranges observed were 28 to 1690ng/L and 45 to 4156ng/L for glyphosate and AMPA, respectively with strong spatial and temporal fluctuations. Both contaminants were found at inbound sampling sites in the stream Muehlenfliess and concentrations decreased along the salinity gradient to the estuaries of the Baltic Sea. The data obtained in this study clearly depict the transport of glyphosate and AMPA to the Baltic Sea. Hence, detailed fate and risk assessment for both contaminants in marine environments are required.

  4. Mechanisms for Antagonistic Regulation of AMPA and NMDA-D1 Receptor Complexes at Postsynaptic Sites

    NASA Technical Reports Server (NTRS)

    Schumann, Johann; Scheler, Gabriele

    2004-01-01

    From the analysis of these pathways we conclude that postsynaptic processes that regulate synaptic transmission undergo significant cross-talk with respect to glutamatergic and neuromodulatory (dopamine) signals. The main hypothesis is that of a compensatory regulation, a competitive switch between the induction of increased AMPA conductance by CaMKII-dependent phosphorylation and reduced expression of PP2A, and increased D1 receptor sensitivity and expression by increased PKA, PP2A and decreased PP-1/calcineurin expression. Both types of plasticity are induced by NMDA receptor activation and increased internal calcium, they require different internal conditions to become expressed. Specifically we propose that AMPA regulation and D1 regulation are inversely coupled;The net result may be a bifurcation of synaptic state into predominantly AMPA or NMDA-D1 synapses. This could have functional consequences: stable connections for AMPA and conditional gating for NMDA-D1 synapses.

  5. Calcium permeable AMPA receptors and autoreceptors in external tufted cells of rat olfactory bulb

    PubMed Central

    Ma, Jie; Lowe, Graeme

    2007-01-01

    Glomeruli are functional units of the olfactory bulb responsible for early processing of odor information encoded by single olfactory receptor genes. Glomerular neural circuitry includes numerous external tufted (ET) cells whose rhythmic burst firing may mediate synchronization of bulbar activity with the inhalation cycle. Bursting is entrained by glutamatergic input from olfactory nerve terminals, so specific properties of ionotropic glutamate receptors on ET cells are likely to be important determinants of olfactory processing. Particularly intriguing is recent evidence that α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors of juxta-glomerular neurons may permeate calcium. This could provide a novel pathway for regulating ET cell signaling. We tested the hypothesis that ET cells express functional calcium-permeable AMPA receptors. In rat olfactory bulb slices, excitatory postsynaptic currents (EPSCs) in ET cells were evoked by olfactory nerve shock, and by uncaging glutamate. We found attenuation of AMPA/kainate EPSCs by 1-naphthyl acetyl-spermine (NAS), an open-channel blocker specific for calcium permeable AMPA receptors. Cyclothiazide strongly potentiated EPSCs, indicating a major contribution from AMPA receptors. The current-voltage (I-V) relation of uncaging EPSCs showed weak inward rectification which was lost after > ~ 10 min of whole-cell dialysis, and was absent in NAS. In kainate-stimulated slices, Co2+ ions permeated cells of the glomerular layer. Large AMPA EPSCs were accompanied by fluorescence signals in fluo-4 loaded cells, suggesting calcium permeation. Depolarizing pulses evoked slow tail currents with pharmacology consistent with involvement of calcium permeable AMPA autoreceptors. Tail currents were abolished by Cd2+ and NBQX, and were sensitive to NAS block. Glutamate autoreceptors were confirmed by uncaging intracellular calcium to evoke a large inward current. Our results provide evidence that calcium permeable AMPA

  6. Rational Design of a Novel AMPA Receptor Modulator through a Hybridization Approach.

    PubMed

    Caldwell, Nicola; Harms, Jonathan E; Partin, Kathryn M; Jamieson, Craig

    2015-04-09

    The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are a family of glutamate ion channels of considerable interest in excitatory neurotransmission and associated disease processes. Here, we demonstrate how exploitation of the available X-ray crystal structure of the receptor ligand binding domain enabled the development of a new class of AMPA receptor positive allosteric modulators (7) through hybridization of known ligands (5 and 6), leading to a novel chemotype with promising pharmacological properties.

  7. Rational Design of a Novel AMPA Receptor Modulator through a Hybridization Approach

    PubMed Central

    2015-01-01

    The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are a family of glutamate ion channels of considerable interest in excitatory neurotransmission and associated disease processes. Here, we demonstrate how exploitation of the available X-ray crystal structure of the receptor ligand binding domain enabled the development of a new class of AMPA receptor positive allosteric modulators (7) through hybridization of known ligands (5 and 6), leading to a novel chemotype with promising pharmacological properties. PMID:25893038

  8. Incorporation of inwardly rectifying AMPA receptors at silent synapses during hippocampal long-term potentiation.

    PubMed

    Morita, Daiju; Rah, Jong Cheol; Isaac, John T R

    2014-01-05

    Despite decades of study, the mechanisms by which synapses express the increase in strength during long-term potentiation (LTP) remain an area of intense interest. Here, we have studied how AMPA receptor subunit composition changes during the early phases of hippocampal LTP in CA1 pyramidal neurons. We studied LTP at silent synapses that initially lack AMPA receptors, but contain NMDA receptors. We show that strongly inwardly rectifying AMPA receptors are initially incorporated at silent synapses during LTP and are then subsequently replaced by non-rectifying AMPA receptors. These findings suggest that silent synapses initially incorporate GluA2-lacking, calcium-permeable AMPA receptors during LTP that are then replaced by GluA2-containing calcium-impermeable receptors. We also show that LTP consolidation at CA1 synapses requires a rise in intracellular calcium concentration during the early phase of expression, indicating that calcium influx through the GluA2-lacking AMPA receptors drives their replacement by GluA2-containing receptors during LTP consolidation. Taken together with previous studies in hippocampus and in other brain regions, these findings suggest that a common mechanism for the expression of activity-dependent glutamatergic synaptic plasticity involves the regulation of GluA2-subunit composition and highlights a critical role for silent synapses in this process.

  9. Differential effects of glyphosate and aminomethylphosphonic acid (AMPA) on photosynthesis and chlorophyll metabolism in willow plants.

    PubMed

    Gomes, Marcelo Pedrosa; Le Manac'h, Sarah Gingras; Maccario, Sophie; Labrecque, Michel; Lucotte, Marc; Juneau, Philippe

    2016-06-01

    We used a willow species (Salix miyabeana cultivar SX64) to examine the differential secondary-effects of glyphosate and aminomethylphosphonic acid (AMPA), the principal glyphosate by-product, on chlorophyll metabolism and photosynthesis. Willow plants were treated with different concentrations of glyphosate (equivalent to 0, 1.4, 2.1 and 2.8kgha(-1)) and AMPA (equivalent to 0, 0.28, 1.4 and 2.8kgha(-1)) and evaluations of pigment contents, chlorophyll fluorescence, and oxidative stress markers (hydrogen peroxide content and antioxidant enzyme activities) in leaves were performed after 12h of exposure. We observed that AMPA and glyphosate trigger different mechanisms leading to decreases in chlorophyll content and photosynthesis rates in willow plants. Both chemicals induced ROS accumulation in willow leaves although only glyphosate-induced oxidative damage through lipid peroxidation. By disturbing chlorophyll biosynthesis, AMPA induced decreases in chlorophyll contents, with consequent effects on photosynthesis. With glyphosate, ROS increases were higher than the ROS-sensitive threshold, provoking chlorophyll degradation (as seen by pheophytin accumulation) and invariable decreases in photosynthesis. Peroxide accumulation in both AMPA and glyphosate-treated plants was due to the inhibition of antioxidant enzyme activities. The different effects of glyphosate on chlorophyll contents and photosynthesis as described in the literature may be due to various glyphosate:AMPA ratios in those plants.

  10. Glyphosate-Resistant and Conventional Canola (Brassica napus L.) Responses to Glyphosate and Aminomethylphosphonic Acid (AMPA) Treatment.

    PubMed

    Corrêa, Elza Alves; Dayan, Franck E; Owens, Daniel K; Rimando, Agnes M; Duke, Stephen O

    2016-05-11

    Glyphosate-resistant (GR) canola contains two transgenes that impart resistance to the herbicide glyphosate: (1) the microbial glyphosate oxidase gene (gox) encoding the glyphosate oxidase enzyme (GOX) that metabolizes glyphosate to aminomethylphosphonic acid (AMPA) and (2) cp4 that encodes a GR form of the glyphosate target enzyme 5-enolpyruvylshikimic acid-3-phosphate synthase. The objectives of this research were to determine the phytotoxicity of AMPA to canola, the relative metabolism of glyphosate to AMPA in GR and conventional non-GR (NGR) canola, and AMPA pool sizes in glyphosate-treated GR canola. AMPA applied at 1.0 kg ha(-1) was not phytotoxic to GR or NGR. At this AMPA application rate, NGR canola accumulated a higher concentration of AMPA in its tissues than GR canola. At rates of 1 and 3.33 kg ae ha(-1) of glyphosate, GR canola growth was stimulated. This stimulatory effect is similar to that of much lower doses of glyphosate on NGR canola. Both shikimate and AMPA accumulated in tissues of these glyphosate-treated plants. In a separate experiment in which young GR and NGR canola plants were treated with non-phytotoxic levels of [(14)C]-glyphosate, very little glyphosate was metabolized in NGR plants, whereas most of the glyphosate was metabolized to AMPA in GR plants at 7 days after application. Untreated leaves of GR plants accumulated only metabolites (mostly AMPA) of glyphosate, indicating that GOX activity is very high in the youngest leaves. These data indicate that more glyphosate is transformed to AMPA rapidly in GR canola and that the accumulated AMPA is not toxic to the canola plant.

  11. AMPA-Kainate Receptor Inhibition Promotes Neurologic Recovery in Premature Rabbits with Intraventricular Hemorrhage

    PubMed Central

    Dohare, Preeti; Zia, Muhammad T.; Ahmed, Ehsan; Ahmed, Asad; Yadala, Vivek; Schober, Alexandra L.; Ortega, Juan Alberto; Kayton, Robert; Ungvari, Zoltan; Mongin, Alexander A.

    2016-01-01

    Intraventricular hemorrhage (IVH) in preterm infants leads to cerebral inflammation, reduced myelination of the white matter, and neurological deficits. No therapeutic strategy exists against the IVH-induced white matter injury. AMPA-kainate receptor induced excitotoxicity contributes to oligodendrocyte precursor cell (OPC) damage and hypomyelination in both neonatal and adult models of brain injury. Here, we hypothesized that IVH damages white matter via AMPA receptor activation, and that AMPA-kainate receptor inhibition suppresses inflammation and restores OPC maturation, myelination, and neurologic recovery in preterm newborns with IVH. We tested these hypotheses in a rabbit model of glycerol-induced IVH and evaluated the expression of AMPA receptors in autopsy samples from human preterm infants. GluR1-GluR4 expressions were comparable between preterm humans and rabbits with and without IVH. However, GluR1 and GluR2 levels were significantly lower in the embryonic white matter and germinal matrix relative to the neocortex in both infants with and without IVH. Pharmacological blockade of AMPA-kainate receptors with systemic NBQX, or selective AMPA receptor inhibition by intramuscular perampanel restored myelination and neurologic recovery in rabbits with IVH. NBQX administration also reduced the population of apoptotic OPCs, levels of several cytokines (TNFα, IL-β, IL-6, LIF), and the density of Iba1+ microglia in pups with IVH. Additionally, NBQX treatment inhibited STAT-3 phosphorylation, but not astrogliosis or transcription factors regulating gliosis. Our data suggest that AMPA-kainate receptor inhibition alleviates OPC loss and IVH-induced inflammation and restores myelination and neurologic recovery in preterm rabbits with IVH. Therapeutic use of FDA-approved perampanel treatment might enhance neurologic outcome in premature infants with IVH. SIGNIFICANCE STATEMENT Intraventricular hemorrhage (IVH) is a major complication of prematurity and a large number

  12. Excitatory Mechanisms in the Suprachiasmatic Nucleus: The Role of AMPA/KA Glutamate Receptors

    PubMed Central

    Michel, Stephan; Itri, Jason; Colwell, Christopher S.

    2008-01-01

    A variety of evidence suggests that the effects of light on the mammalian circadian system are mediated by direct retinal ganglion cell projection to the suprachiasmatic nucleus (SCN). This synaptic connection is glutamatergic and the release of glutamate is detected by both N-methyl-d-asparate (NMDA) and amino-methyl proprionic acid/kainate (AMPA/KA) iontotropic glutamate receptors (GluRs). It is well established that NMDA GluRs play a critical role in mediating the effects of light on the circadian system; however, the role of AMPA/KA GluRs has received less attention. In the present study, we sought to better understand the contribution of AMPA/KA-mediated currents in the circadian system based in the SCN. First, whole cell patch-clamp electrophysiological techniques were utilized to measure spontaneous excitatory postsynaptic currents (sEPSCs) from SCN neurons. These currents were widespread in the SCN and not just restricted to the retino-recipient region. The sEPSC frequency and amplitude did not vary with the daily cycle. Similarly, currents evoked by the exogenous application of AMPA onto SCN neurons were widespread within the SCN and did not exhibit a diurnal rhythm in their magnitude. Fluorometric techniques were utilized to estimate AMPA-induced calcium (Ca2+) concentration changes in SCN neurons. The resulting data indicate that AMPA-evoked Ca2+ transients were widespread in the SCN and that there was a daily rhythm in the magnitude of AMPA-induced Ca2+ transients that peaked during the night. By itself, blocking AMPA/KA GluRs with a receptor blocker decreased the spontaneous firing of some SCN neurons as well as reduced resting Ca2+ levels, suggesting tonic glutamatergic excitation. Finally, immunohistochemical techniques were used to describe expression of the AMPA-preferring GluR subunits GluR1 and GluR2/3s within the SCN. Overall, our data suggest that glutamatergic synaptic transmission mediated by AMPA/KA GluRs play an important role throughout

  13. Losses of glyphosate and AMPA via drainflow in a typical Belgian residential area

    NASA Astrophysics Data System (ADS)

    Tang, Ting; Boënne, Wesley; van Griensven, Ann; Seuntjens, Piet; Bronders, Jan; Desmet, Nele

    2014-05-01

    Urban hard surfaces are considered as important facilitators for pesticide transport into urban streams. To obtain concurrent high-resolution data for a detailed investigation on the losses of pesticide runoff from hard surfaces, a monitoring campaign was performed in a typical Belgian residential area (9.5 ha) between 7 May and 7 August, 2013. The campaign yielded a concurrent dataset of rainfall (1-mm rainfall interval), discharge (1-min interval), glyphosate application by the residents and the occurrences of glyphosate and its major degradation product - aminomethylphosphonic acid (AMPA) in the separated storm drainage outflow during 12 rainfall events. In addition, detailed information was obtained on the spatial characteristics of the study area. The resulting dataset allows us to investigate the relevance of catchment hydrology, urban surface properties and pesticide application to the transport and losses of glyphosate in a residential environment. During the campaign, glyphosate was only applied by local residents, mainly on their private driveways. As a result of their continuous use, both glyphosate and AMPA were detected in all analysed outflow samples, with maximum concentrations of 6.1 μg/L and 5.8 μg/L, respectively. Overall, the storm drainage system collected 0.43% of the applied amount of glyphosate. However, this loss rate varied considerably among rainfall events, ranging from 0.04% to 23.36%. According to statistical analysis of the 12 rainfall events, the loss rate was significantly correlated with three factors: the application amount prior to a rainfall event (p < 0.005), rainfall amount during the event (p < 0.02) and the weighted lag time between glyphosate application and the start of the rainfall event (negatively, p < 0.05). A regression analysis showed that these three factors can explain more than 85% of the variation in the loss rate of glyphosate. Furthermore, three types of glyphosate runoff were classified by a clustering

  14. Individual stress vulnerability is predicted by short-term memory and AMPA receptor subunit ratio in the hippocampus.

    PubMed

    Schmidt, Mathias V; Trümbach, Dietrich; Weber, Peter; Wagner, Klaus; Scharf, Sebastian H; Liebl, Claudia; Datson, Nicole; Namendorf, Christian; Gerlach, Tamara; Kühne, Claudia; Uhr, Manfred; Deussing, Jan M; Wurst, Wolfgang; Binder, Elisabeth B; Holsboer, Florian; Müller, Marianne B

    2010-12-15

    Increased vulnerability to aversive experiences is one of the main risk factors for stress-related psychiatric disorders as major depression. However, the molecular bases of vulnerability, on the one hand, and stress resilience, on the other hand, are still not understood. Increasing clinical and preclinical evidence suggests a central involvement of the glutamatergic system in the pathogenesis of major depression. Using a mouse paradigm, modeling increased stress vulnerability and depression-like symptoms in a genetically diverse outbred strain, and we tested the hypothesis that differences in AMPA receptor function may be linked to individual variations in stress vulnerability. Vulnerable and resilient animals differed significantly in their dorsal hippocampal AMPA receptor expression and AMPA receptor binding. Treatment with an AMPA receptor potentiator during the stress exposure prevented the lasting effects of chronic social stress exposure on physiological, neuroendocrine, and behavioral parameters. In addition, spatial short-term memory, an AMPA receptor-dependent behavior, was found to be predictive of individual stress vulnerability and response to AMPA potentiator treatment. Finally, we provide evidence that genetic variations in the AMPA receptor subunit GluR1 are linked to the vulnerable phenotype. Therefore, we propose genetic variations in the AMPA receptor system to shape individual stress vulnerability. Those individual differences can be predicted by the assessment of short-term memory, thereby opening up the possibility for a specific treatment by enhancing AMPA receptor function.

  15. AMPA receptor-induced local brain-derived neurotrophic factor signaling mediates motor recovery after stroke.

    PubMed

    Clarkson, Andrew N; Overman, Justine J; Zhong, Sheng; Mueller, Rudolf; Lynch, Gary; Carmichael, S Thomas

    2011-03-09

    Stroke is the leading cause of adult disability. Recovery after stroke shares similar molecular and cellular properties with learning and memory. A main component of learning-induced plasticity involves signaling through AMPA receptors (AMPARs). We systematically tested the role of AMPAR function in motor recovery in a mouse model of focal stroke. AMPAR function controls functional recovery beginning 5 d after the stroke. Positive allosteric modulators of AMPARs enhance recovery of limb control when administered after a delay from the stroke. Conversely, AMPAR antagonists impair motor recovery. The contributions of AMPARs to recovery are mediated by release of brain-derived neurotrophic factor (BDNF) in periinfarct cortex, as blocking local BDNF function in periinfarct cortex blocks AMPAR-mediated recovery and prevents the normal pattern of motor recovery. In contrast to a delayed AMPAR role in motor recovery, early administration of AMPAR agonists after stroke increases stroke damage. These findings indicate that the role of glutamate signaling through the AMPAR changes over time in stroke: early potentiation of AMPAR signaling worsens stroke damage, whereas later potentiation of the same signaling system improves functional recovery.

  16. Differential roles for NSF and GRIP/ABP in AMPA receptor cycling.

    PubMed

    Braithwaite, Steven P; Xia, Houhui; Malenka, Robert C

    2002-05-14

    alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) stability and movement at synapses are important factors controlling synaptic strength. Here, we study the roles of proteins [N-ethylmaleimide-sensitive fusion protein (NSF), glutamate receptor AMPAR binding protein (ABP)-interacting protein (GRIP)/(ABP), and protein interacting with C-kinase-1 (PICK1) that interact with the GluR2 subunit in the control of the surface expression and cycling of AMPARs. Epitope-tagged GluR2 formed functional receptors that exhibited targeting to synaptic sites. Constructs in which binding to NSF, PDZ proteins (GRIP/ABP and PICK1), or GRIP/ABP alone was eliminated each exhibited normal surface targeting and constitutive cycling. The lack of NSF binding, however, resulted in receptors that were endocytosed to a greater extent than wild-type receptors in response to application of AMPA or N-methyl-d-aspartate (NMDA). Conversely, the behavior of the GluR2 mutants incapable of binding to GRIP/ABP suggests that these PDZ proteins play a role in the stabilization of an intracellular pool of AMPARs that have been internalized on stimulation, thus inhibiting their recycling to the synaptic membrane. These results provide further evidence for distinct functional roles of GluR2-interacting proteins in AMPAR trafficking.

  17. Glyphosate and AMPA distribution in wind-eroded sediment derived from loess soil.

    PubMed

    Bento, Célia P M; Goossens, Dirk; Rezaei, Mahrooz; Riksen, Michel; Mol, Hans G J; Ritsema, Coen J; Geissen, Violette

    2017-01-01

    Glyphosate is one of the most used herbicides in agricultural lands worldwide. Wind-eroded sediment and dust, as an environmental transport pathway of glyphosate and of its main metabolite aminomethylphosphonic acid (AMPA), can result in environmental- and human exposure far beyond the agricultural areas where it has been applied. Therefore, special attention is required to the airborne transport of glyphosate and AMPA. In this study, we investigated the behavior of glyphosate and AMPA in wind-eroded sediment by measuring their content in different size fractions (median diameters between 715 and 8 μm) of a loess soil, during a period of 28 days after glyphosate application. Granulometrical extraction was done using a wind tunnel and a Soil Fine Particle Extractor. Extractions were conducted on days 0, 3, 7, 14, 21 and 28 after glyphosate application. Results indicated that glyphosate and AMPA contents were significantly higher in the finest particle fractions (median diameters between 8 and 18 μm), and lowered significantly with the increase in particle size. However, their content remained constant when aggregates were present in the sample. Glyphosate and AMPA contents correlated positively with clay, organic matter, and silt content. The dissipation of glyphosate over time was very low, which was most probably due to the low soil moisture content of the sediment. Consequently, the formation of AMPA was also very low. The low dissipation of glyphosate in our study indicates that the risk of glyphosate transport in dry sediment to off-target areas by wind can be very high. The highest glyphosate and AMPA contents were found in the smallest soil fractions (PM10 and less), which are easily inhaled and, therefore, contribute to human exposure.

  18. Cornichon proteins determine the subunit composition of synaptic AMPA receptors.

    PubMed

    Herring, Bruce E; Shi, Yun; Suh, Young Ho; Zheng, Chan-Ying; Blankenship, Sabine M; Roche, Katherine W; Nicoll, Roger A

    2013-03-20

    Cornichon-2 and cornichon-3 (CNIH-2/-3) are AMPA receptor (AMPAR) binding proteins that promote receptor trafficking and markedly slow AMPAR deactivation in heterologous cells, but their role in neurons is unclear. Using CNIH-2 and CNIH-3 conditional knockout mice, we find a profound reduction of AMPAR synaptic transmission in the hippocampus. This deficit is due to the selective loss of surface GluA1-containing AMPARs (GluA1A2 heteromers), leaving a small residual pool of synaptic GluA2A3 heteromers. The kinetics of AMPARs in neurons lacking CNIH-2/-3 are faster than those in WT neurons due to the fast kinetics of GluA2A3 heteromers. The remarkably selective effect of CNIHs on the GluA1 subunit is probably mediated by TARP γ-8, which prevents a functional association of CNIHs with non-GluA1 subunits. These results point to a sophisticated interplay between CNIHs and γ-8 that dictates subunit-specific AMPAR trafficking and the strength and kinetics of synaptic AMPAR-mediated transmission.

  19. Contextual learning requires synaptic AMPA receptor delivery in the hippocampus.

    PubMed

    Mitsushima, Dai; Ishihara, Kouji; Sano, Akane; Kessels, Helmut W; Takahashi, Takuya

    2011-07-26

    The hippocampus plays a central role in learning and memory. Although synaptic delivery of AMPA-type glutamate receptors (AMPARs) contributes to experience-dependent synaptic strengthening, its role in hippocampus-dependent learning remains elusive. By combining viral-mediated in vivo gene delivery with in vitro patch-clamp recordings, we found that the inhibitory avoidance task, a hippocampus-dependent contextual fear-learning paradigm, delivered GluR1-containing AMPARs into CA3-CA1 synapses of the dorsal hippocampus. To block the synaptic delivery of endogenous AMPARs, we expressed a fragment of the GluR1-cytoplasmic tail (the 14-aa GluR1 membrane-proximal region with two serines mutated to phospho-mimicking aspartates: MPR-DD). MPR-DD prevented learning-driven synaptic AMPAR delivery in CA1 neurons. Bilateral expression of MPR-DD in the CA1 region of the rat impaired inhibitory avoidance learning, indicating that synaptic GluR1 trafficking in the CA1 region of the hippocampus is required for encoding contextual fear memories. The fraction of CA1 neurons that underwent synaptic strengthening positively correlated with the performance in the inhibitory avoidance fear memory task. These data suggest that the robustness of a contextual memory depends on the number of hippocampal neurons that participate in the encoding of a memory trace.

  20. Characterization of the AMPA-activated receptors present on motoneurons.

    PubMed

    Greig, A; Donevan, S D; Mujtaba, T J; Parks, T N; Rao, M S

    2000-01-01

    Motoneurons have been shown to be particularly sensitive to Ca2+-dependent glutamate excitotoxicity, mediated via AMPA receptors (AMPARs). To determine the molecular basis for this susceptibility we have used immunocytochemistry, RT-PCR, and electrophysiology to profile AMPARs on embryonic day 14.5 rat motoneurons. Motoneurons show detectable AMPAR-mediated calcium permeability in vitro and in vivo as determined by cobalt uptake and electrophysiology. Motoneurons express all four AMPAR subunit mRNAs, with glutamate receptor (GluR) 2 being the most abundant (63.9+/-4.8%). GluR2 is present almost exclusively in the edited form, and electrophysiology confirms that most AMPARs present are calcium-impermeant. However, the kainate current in motoneurons was blocked an average of 32.0% by Joro spider toxin, indicating that a subset of the AM PARs is Ca2+-permeable. Therefore, heterogeneity of AMPARs, rather than the absence of GluR2 or the presence of unedited GluR2, explains AMPAR-mediated Ca2+ permeability. The relative levels of flip/flop isoforms of each subunit were also examined by semiquantitative PCR. Both isoforms were present, but the relative proportion varied for each subunit, and the flip isoform predominated. Thus, our data show that despite high levels of edited GluR2 mRNA, some AMPARs are Ca2+-permeable, and this subset of AMPARs can account for the AMPAR-mediated Ca2+ inflow inferred from cobalt uptake and electrophysiology studies.

  1. Transfer of glyphosate and its degradate AMPA to surface waters through urban sewerage systems.

    PubMed

    Botta, Fabrizio; Lavison, Gwenaëlle; Couturier, Guillaume; Alliot, Fabrice; Moreau-Guigon, Elodie; Fauchon, Nils; Guery, Bénédicte; Chevreuil, Marc; Blanchoud, Hélène

    2009-09-01

    A study of glyphosate and aminomethyl phosphonic acid (AMPA) transfer in the Orge watershed (France) was carried out during 2007 and 2008. Water samples were collected in surface water, wastewater sewer, storm sewer and wastewater treatment plant (WWTP). These two molecules appeared to be the most frequently detected ones in the rivers and usually exceeded the European quality standard concentrations of 0.1microg L(-1) for drinking water. The annual glyphosate estimated load was 1.9 kg year(-1) upstream (agricultural zone) and 179.5 kg year(-1) at the catchment outlet (urban zone). This result suggests that the contamination of this basin by glyphosate is essentially from urban origin (road and railway applications). Glyphosate reached surface water prevalently through storm sewer during rainfall event. Maximum concentrations were detected in storm sewer just after a rainfall event (75-90 microg L(-1)). High concentrations of glyphosate in surface water during rainfall events reflected urban runoff impact. AMPA was always detected in the sewerage system. This molecule reached surface water mainly via WWTP effluent and also through storm sewer. Variations in concentrations of AMPA during hydrological episodes were minor compared to glyphosate variations. Our study highlights that AMPA and glyphosate origins in urban area are different. During dry period, detergent degradation seemed to be the major AMPA source in wastewater.

  2. Pathogenic Mechanism of an Autism-Associated Neuroligin Mutation Involves Altered AMPA-Receptor Trafficking

    PubMed Central

    Chanda, Soham; Aoto, Jason; Lee, Sung-Jin; Wernig, Marius; Südhof, Thomas C.

    2015-01-01

    Neuroligins are postsynaptic cell-adhesion molecules that bind to presynaptic neurexins. Although the general synaptic role of neuroligins is undisputed, their specific functions at a synapse remain unclear, even controversial. Moreover, many neuroligin gene mutations were associated with autism, but the pathophysiological relevance of these mutations is often unknown, and their mechanisms of action uninvestigated. Here, we examine the synaptic effects of an autism-associated neuroligin-4 substitution (called R704C) which mutates a cytoplasmic arginine residue that is conserved in all neuroligins. We show that the R704C mutation, when introduced into neuroligin-3, enhances the interaction between neuroligin-3 and AMPA-receptors, increases AMPA-receptor internalization, and decreases postsynaptic AMPA-receptor levels. When introduced into neuroligin-4, conversely, the R704C mutation unexpectedly elevated AMPA-receptor mediated synaptic responses. These results suggest a general functional link between neuroligins and AMPA-receptors, indicate that both neuroligin-3 and -4 act at excitatory synapses but perform surprisingly distinct functions, and demonstrate that the R704C mutation significantly impairs the normal function of neuroligin-4, thereby validating its pathogenicity. PMID:25778475

  3. Erbin interacts with TARP γ-2 for surface expression of AMPA receptors in cortical interneurons.

    PubMed

    Tao, Yanmei; Chen, Yong-Jun; Shen, Chengyong; Luo, Zhengyi; Bates, C Ryan; Lee, Daehoon; Marchetto, Sylvie; Gao, Tian-Ming; Borg, Jean-Paul; Xiong, Wen-Cheng; Mei, Lin

    2013-03-01

    Inhibitory neurons control the firing of glutamatergic neurons and synchronize brain activity. However, little is known about mechanisms of excitatory synapse formation in inhibitory neurons. Here we demonstrate that Erbin is specifically expressed in cortical inhibitory neurons. It localizes at excitatory synapses and regulates AMPA receptor (AMPAR) surface expression. Erbin mutation reduced mEPSCs and AMPAR currents specifically in parvalbumin (PV)-positive interneurons but not in pyramidal neurons. We found that the AMPAR auxiliary protein TARP γ-2 was specifically expressed in cortical interneurons. Erbin interacts with TARP γ-2 and is crucial for its stability. Deletion of the γ-2-interacting domain in Erbin attenuated surface AMPAR and excitatory transmission in PV-positive interneurons. Furthermore, we observed behavioral deficits in Erbin-null mice and in mice expressing an Erbin truncation mutant that is unable to interact with TARP γ-2. These observations demonstrate a crucial function for Erbin in AMPAR surface expression in cortical PV-positive interneurons and may contribute to a better understanding of psychiatric disorders.

  4. GluA1 signal peptide determines the spatial assembly of heteromeric AMPA receptors

    PubMed Central

    Li, Yan-Jun; Kalyanaraman, Chakrapani; Qiu, Li-Li; Chen, Chen; Xiao, Qi; Liu, Wen-Xue; Zhang, Wei; Yang, Jian-Jun; Chen, Guiquan; Jacobson, Matthew P.; Shi, Yun Stone

    2016-01-01

    AMPA-type glutamate receptors (AMPARs) mediate fast excitatory neurotransmission and predominantly assemble as heterotetramers in the brain. Recently, the crystal structures of homotetrameric GluA2 demonstrated that AMPARs are assembled with two pairs of conformationally distinct subunits, in a dimer of dimers formation. However, the structure of heteromeric AMPARs remains unclear. Guided by the GluA2 structure, we performed cysteine mutant cross-linking experiments in full-length GluA1/A2, aiming to draw the heteromeric AMPAR architecture. We found that the amino-terminal domains determine the first level of heterodimer formation. When the dimers further assemble into tetramers, GluA1 and GluA2 subunits have preferred positions, possessing a 1–2–1–2 spatial assembly. By swapping the critical sequences, we surprisingly found that the spatial assembly pattern is controlled by the excisable signal peptides. Replacements with an unrelated GluK2 signal peptide demonstrated that GluA1 signal peptide plays a critical role in determining the spatial priority. Our study thus uncovers the spatial assembly of an important type of glutamate receptors in the brain and reveals a novel function of signal peptides. PMID:27601647

  5. PICK1 interacts with ABP/GRIP to regulate AMPA receptor trafficking.

    PubMed

    Lu, Wei; Ziff, Edward B

    2005-08-04

    PICK1 and ABP/GRIP bind to the AMPA receptor (AMPAR) GluR2 subunit C terminus. Transfer of the receptor from ABP/GRIP to PICK1, facilitated by GluR2 S880 phosphorylation, may initiate receptor trafficking. Here we report protein interactions that regulate these steps. The PICK1 BAR domain interacts intermolecularly with the ABP/GRIP linker II region and intramolecularly with the PICK1 PDZ domain. Binding of PKCalpha or GluR2 to the PICK1 PDZ domain disrupts the intramolecular interaction and facilitates the PICK1 BAR domain association with ABP/GRIP. Interference with the PICK1-ABP/GRIP interaction impairs S880 phosphorylation of GluR2 by PKC and decreases the constitutive surface expression of GluR2, the NMDA-induced endocytosis of GluR2, and recycling of internalized GluR2. We suggest that the PICK1 interaction with ABP/GRIP is a critical step in controlling GluR2 trafficking.

  6. GSG1L suppresses AMPA receptor-mediated synaptic transmission and uniquely modulates AMPA receptor kinetics in hippocampal neurons

    PubMed Central

    Gu, Xinglong; Mao, Xia; Lussier, Marc P.; Hutchison, Mary Anne; Zhou, Liang; Hamra, F. Kent; Roche, Katherine W.; Lu, Wei

    2016-01-01

    Regulation of AMPA receptor (AMPAR)-mediated synaptic transmission is a key mechanism for synaptic plasticity. In the brain, AMPARs assemble with a number of auxiliary subunits, including TARPs, CNIHs and CKAMP44, which are important for AMPAR forward trafficking to synapses. Here we report that the membrane protein GSG1L negatively regulates AMPAR-mediated synaptic transmission. Overexpression of GSG1L strongly suppresses, and GSG1L knockout (KO) enhances, AMPAR-mediated synaptic transmission. GSG1L-dependent regulation of AMPAR synaptic transmission relies on the first extracellular loop domain and its carboxyl-terminus. GSG1L also speeds up AMPAR deactivation and desensitization in hippocampal CA1 neurons, in contrast to the effects of TARPs and CNIHs. Furthermore, GSG1L association with AMPARs inhibits CNIH2-induced slowing of the receptors in heterologous cells. Finally, GSG1L KO rats have deficits in LTP and show behavioural abnormalities in object recognition tests. These data demonstrate that GSG1L represents a new class of auxiliary subunit with distinct functional properties for AMPARs. PMID:26932439

  7. Quantal release of glutamate generates pure kainate and mixed AMPA/kainate EPSCs in hippocampal neurons.

    PubMed

    Cossart, Rosa; Epsztein, Jérôme; Tyzio, Roman; Becq, Hélène; Hirsch, June; Ben-Ari, Yehezkel; Crépel, Valérie

    2002-07-03

    The relative contribution of kainate receptors to ongoing glutamatergic activity is at present unknown. We report the presence of spontaneous, miniature, and minimal stimulation-evoked excitatory postsynaptic currents (EPSCs) that are mediated solely by kainate receptors (EPSC(kainate)) or by both AMPA and kainate receptors (EPSC(AMPA/kainate)). EPSC(kainate) and EPSC(AMPA/kainate) are selectively enriched in CA1 interneurons and mossy fibers synapses of CA3 pyramidal neurons, respectively. In CA1 interneurons, the decay time constant of EPSC(kainate) (circa 10 ms) is comparable to values obtained in heterologous expression systems. In both hippocampal neurons, the quantal release of glutamate generates kainate receptor-mediated EPSCs that provide as much as half of the total glutamatergic current. Kainate receptors are, therefore, key players of the ongoing glutamatergic transmission in the hippocampus.

  8. Probing TARP modulation of AMPA receptor conductance with polyamine toxins.

    PubMed

    Jackson, Alexander C; Milstein, Aaron D; Soto, David; Farrant, Mark; Cull-Candy, Stuart G; Nicoll, Roger A

    2011-05-18

    The properties of synaptic AMPA receptors (AMPARs) depend on their subunit composition and association with transmembrane AMPAR regulatory proteins (TARPs). Although both GluA2 incorporation and TARP association have been shown to influence AMPAR channel conductance, the manner in which different TARPs modulate the mean channel conductance of GluA2-containing AMPARs is unknown. Using ultrafast agonist application and nonstationary fluctuation analysis, we found that TARP subtypes differentially increase the mean channel conductance, but not the peak open probability, of recombinant GluA2-containing AMPARs. TARP γ-8, in particular, enhances mean channel conductance to a greater degree than γ-2, γ-3, or γ-4. We then examined the action of a use-dependent antagonist of GluA2-containing AMPARs, philanthotoxin-74 (PhTx-74), on recombinant AMPARs and on GluA2-containing AMPARs in cerebellar granule neurons from stargazer mice transfected with TARPs. We found that the rate and extent of channel block varies with TARP subtype, in a manner that correlates linearly with mean channel conductance. Furthermore, block of GluA2-containing AMPARs by polyamine toxins varied depending on whether channels were activated by the full agonist glutamate or the partial agonist kainate, consistent with conductance state-dependent block. Block of GluA2-lacking AMPARs by PhTx-433 is also modulated by TARP association and is a function of agonist efficacy. Our data indicate that channel block by polyamine toxins is sensitive to the mean channel conductance of AMPARs, which varies with TARP subtype and agonist efficacy. Furthermore, our results illustrate the utility of polyamine toxins as sensitive probes of AMPAR channel conductance and suggest the possibility that TARPs may influence their channel properties by selectively stabilizing specific channel conformations, rather than altering the pore structure.

  9. Screening for AMPA receptor auxiliary subunit specific modulators

    PubMed Central

    Azumaya, Caleigh M.; Days, Emily L.; Vinson, Paige N.; Stauffer, Shaun; Sulikowski, Gary; Weaver, C. David; Nakagawa, Terunaga

    2017-01-01

    AMPA receptors (AMPAR) are ligand gated ion channels critical for synaptic transmission and plasticity. Their dysfunction is implicated in a variety of psychiatric and neurological diseases ranging from major depressive disorder to amyotrophic lateral sclerosis. Attempting to potentiate or depress AMPAR activity is an inherently difficult balancing act between effective treatments and debilitating side effects. A newly explored strategy to target subsets of AMPARs in the central nervous system is to identify compounds that affect specific AMPAR-auxiliary subunit complexes. This exploits diverse spatio-temporal expression patterns of known AMPAR auxiliary subunits, providing means for designing brain region-selective compounds. Here we report a high-throughput screening-based pipeline that can identify compounds that are selective for GluA2-CNIH3 and GluA2-stargazin complexes. These compounds will help us build upon the growing library of AMPAR-auxiliary subunit specific inhibitors, which have thus far all been targeted to TARP γ-8. We used a cell-based assay combined with a voltage-sensitive dye (VSD) to identify changes in glutamate-gated cation flow across the membranes of HEK cells co-expressing GluA2 and an auxiliary subunit. We then used a calcium flux assay to further validate hits picked from the VSD assay. VU0612951 and VU0627849 are candidate compounds from the initial screen that were identified as negative and positive allosteric modulators (NAM and PAM), respectively. They both have lower IC50/EC50s on complexes containing stargazin and CNIH3 than GSG1L or the AMPAR alone. We have also identified a candidate compound, VU0539491, that has NAM activity in GluA2(R)-CNIH3 and GluA2(Q) complexes and PAM activity in GluA2(Q)-GSG1L complexes. PMID:28358902

  10. CNQX and AMPA inhibit electrical synaptic transmission: a potential interaction between electrical and glutamatergic synapses

    PubMed Central

    Li, Qin; Burrell, Brian D.

    2008-01-01

    Electrical synapses play an important role in signaling between neurons and the synaptic connections between many neurons possess both electrical and chemical components. Although modulation of electrical synapses is frequently observed, the cellular processes that mediate such changes have not been studied as thoroughly as plasticity in chemical synapses. In the leech (Hirudo sp), the competitive AMPA receptor antagonist CNQX inhibited transmission at the rectifying electrical synapse of a mixed glutamatergic/electrical synaptic connection. This CNQX-mediated inhibition of the electrical synapse was blocked by concanavalin A (Con A) and dynamin inhibitory peptide (DIP), both of which are known to inhibit endocytosis of neurotransmitter receptors. CNQX-mediated inhibition was also blocked by pep2-SVKI (SVKI), a synthetic peptide that prevents internalization of AMPA-type glutamate receptor. AMPA itself also inhibited electrical synaptic transmission and this AMPA-mediated inhibition was partially blocked by Con A, DIP and SVKI. Low frequency stimulation induced long-term depression (LTD) in both the electrical and chemical components of these synapses and this LTD was blocked by SVKI. GYKI 52466, a selective non-competitive antagonist of AMPA receptors, did not affect the electrical EPSP, although it did block the chemical component of these synapses. CNQX did not affect non-rectifying electrical synapses in two different pairs of neurons. These results suggest an interaction between AMPA-type glutamate receptors and the gap junction proteins that mediate electrical synaptic transmission. This putative interaction between glutamate receptors and gap junction proteins represents a novel mechanism for regulating the strength of synaptic transmission. PMID:18601913

  11. Exacerbation of NMDA, AMPA, and L-glutamate excitotoxicity by the succinate dehydrogenase inhibitor malonate.

    PubMed

    Greene, J G; Greenamyre, J T

    1995-05-01

    We report that a subtoxic dose of the succinate dehydrogenase (SDH) inhibitor malonate greatly enhances the neurotoxicity of three different excitatory amino acid agonists: N-methyl-D-aspartate (NMDA), S-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (S-AMPA), and L-glutamate. In male Sprague-Dawley rats, intrastriatal stereotaxic injection of malonate alone (0.6 mumol), NMDA alone (15 nmol), S-AMPA alone (1 nmol), or glutamate alone (0.6 mumol) produced negligible toxicity as assessed by measurement of lesion volume. Coinjection of subtoxic malonate with NMDA produced a large lesion (15.2 +/- 1.4 mm3), as did coinjection of malonate with S-AMPA (11.0 +/- 1.0 mm3) or glutamate (12.8 +/- 0.7 mm3). Administration of the noncompetitive NMDA antagonist MK-801 (5 mg/kg i.p.) completely blocked the toxicity of malonate plus NMDA (0.5 +/- 0.3 mm3). This dose of MK-801 had little effect on the lesion produced by malonate plus S-AMPA (9.0 +/- 0.7 mm3), but it attenuated the toxicity of malonate plus glutamate by approximately 40% (7.5 +/- 0.9 mm3). Coinjection of the AMPA antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)-quinoxaline (NBQX; 2 nmol) had no effect on malonate plus NMDA or malonate plus glutamate toxicity (12.3 +/- 1.8 and 14.0 +/- 0.9 mm3, respectively) but greatly attenuated malonate plus S-AMPA toxicity (1.5 +/- 0.9 mm3). Combination of the two antagonists conferred no additional neuroprotection in any paradigm. These results indicate that metabolic inhibition exacerbates both NMDA receptor- and non-NMDA receptor-mediated excitotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. AMPA GluA1-flip targeted oligonucleotide therapy reduces neonatal seizures and hyperexcitability

    PubMed Central

    Lykens, Nicole M.; Reddi, Jyoti M.

    2017-01-01

    Glutamate-activated α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-Rs) mediate the majority of excitatory neurotransmission in brain and thus are major drug targets for diseases associated with hyperexcitability or neurotoxicity. Due to the critical nature of AMPA-Rs in normal brain function, typical AMPA-R antagonists have deleterious effects on cognition and motor function, highlighting the need for more precise modulators. A dramatic increase in the flip isoform of alternatively spliced AMPA-R GluA1 subunits occurs post-seizure in humans and animal models. GluA1-flip produces higher gain AMPA channels than GluA1-flop, increasing network excitability and seizure susceptibility. Splice modulating oligonucleotides (SMOs) bind to pre-mRNA to influence alternative splicing, a strategy that can be exploited to develop more selective drugs across therapeutic areas. We developed a novel SMO, GR1, which potently and specifically decreased GluA1-flip expression throughout the brain of neonatal mice lasting at least 60 days after single intracerebroventricular injection. GR1 treatment reduced AMPA-R mediated excitatory postsynaptic currents at hippocampal CA1 synapses, without affecting long-term potentiation or long-term depression, cellular models of memory, or impairing GluA1-dependent cognition or motor function in mice. Importantly, GR1 demonstrated anti-seizure properties and reduced post-seizure hyperexcitability in neonatal mice, highlighting its drug candidate potential for treating epilepsies and other neurological diseases involving network hyperexcitability. PMID:28178321

  13. Involvement of prefrontal AMPA receptors in encounter stimulation-induced hyperactivity in isolation-reared mice.

    PubMed

    Araki, Ryota; Ago, Yukio; Hasebe, Shigeru; Nishiyama, Saki; Tanaka, Tatsunori; Oka, Satoshi; Takuma, Kazuhiro; Matsuda, Toshio

    2014-06-01

    We recently showed that social encounter stimulation induces hyperactivity in mice reared in social isolation from early life and this is associated with the transient activation of prefrontal dopaminergic and serotonergic systems. In the present study, we examined the effect of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist 2, 3-dioxo-6-nitro-1, 2, 3, 4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX) on encounter-induced behavioural and neurochemical changes to study the role of the receptor in abnormal behaviours in isolation-reared mice. The encounter to an intruder mouse induced hyperactivity with transient increases in prefrontal dopamine and serotonin levels in isolation-reared mice. NBQX attenuated the encounter-induced hyperactivity and the associated neurochemical changes in isolation-reared mice. In addition, NBQX reduced aggressive behaviour and cognitive impairment in isolation-reared mice, but did not affect depressive-like behaviour or spontaneous hyper-locomotion in these animals. The AMPA receptor agonist (S)-AMPA increased prefrontal dopamine and serotonin release, and this effect was higher in isolation-reared mice than in the group-reared mice, suggesting higher prefrontal AMPA receptor activity in isolation-reared mice. Furthermore, isolation rearing increased the expression of AMPA receptor subunits (GluR1, GluR2 and GluR3) and GluR1 Ser845 phosphorylation in the prefrontal cortex, but not in the hippocampus or nucleus accumbens. Taken together, these results suggest that an increase in AMPA receptor activity in the prefrontal cortex contributes to some, but not all, abnormal behaviours in isolation-reared mice.

  14. The Fate and Transport of Glyphosate and its Degradation Product, Aminomethylphosphonic Acid (AMPA), in Water

    NASA Astrophysics Data System (ADS)

    Scribner, E.; Meyer, M. T.

    2006-05-01

    Since 2001, the U.S. Geological Survey (USGS) has investigated the fate and transport of glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), in surface water, and more recently in tile-drain flow, soil, and wet deposition. According to U.S. Environmental Protection Agency sources, glyphosate is among the world's most widely used herbicides. In 2004, glyphosate usage estimates indicated that between 103 and 113 million pounds were applied annually to crops in the United States. The use of glyphosate over a wide geographic area suggests that this herbicide might be a potential concern for air, water, and soil quality as well as measured in high concentrations in streams; therefore, it is important to monitor its fate and transport in ground-water/surface-water systems. National, regional, and field-scale studies conducted by the USGS National Water-Quality Assessment and Toxic Substance Hydrology Programs have studied the fate and transport of glyphosate in overland flow, tile- drain flow, surface water, soil, and wet-deposition samples. The samples were analyzed for glyphosate and AMPA by using derivatization and online solid-phase extraction with liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS methods developed by the USGS Organic Geochemistry Research Laboratory in Lawrence, Kansas. During spring, summer, and fall 2002 runoff periods in 50 Midwestern streams, glyphosate was detected at or above the 0.10 micrograms per liter detection limit in 35, 41, and 31 percent of samples, respectively. AMPA was detected in 53, 82, and 75 percent of samples, respectively. Results of 128 samples from a field study showed that glyphosate was transported as a narrow high- concentration pulse during the first period of runoff after application and that the concentration of glyphosate in runoff was greater than the concentration of AMPA. In tile-drain flow, glyphosate and AMPA were transported in a broad low-concentration pulse during these same

  15. Enhanced AMPA Receptor Function Promotes Cerebellar Long-Term Depression Rather than Potentiation

    ERIC Educational Resources Information Center

    van Beugen, Boeke J.; Qiao, Xin; Simmons, Dana H.; De Zeeuw, Chris I.; Hansel, Christian

    2014-01-01

    Ampakines are allosteric modulators of AMPA receptors that facilitate hippocampal long-term potentiation (LTP) and learning, and have been considered for the treatment of cognition and memory deficits. Here, we show that the ampakine CX546 raises the amplitude and slows the decay time of excitatory postsynaptic currents (EPSCs) at cerebellar…

  16. AMPA Receptor Endocytosis in Rat Perirhinal Cortex Underlies Retrieval of Object Memory

    ERIC Educational Resources Information Center

    Cazakoff, Brittany N.; Howland, John G.

    2011-01-01

    Mechanisms consistent with long-term depression in the perirhinal cortex (PRh) play a fundamental role in object recognition memory; however, whether AMPA receptor endocytosis is involved in distinct phases of recognition memory is not known. To address this question, we used local PRh infusions of the cell membrane-permeable Tat-GluA2[subscript…

  17. Topiramate antagonizes NMDA- and AMPA-induced seizure-like activity in planarians.

    PubMed

    Rawls, Scott M; Thomas, Timmy; Adeola, Mobilaji; Patil, Tanvi; Raymondi, Natalie; Poles, Asha; Loo, Michael; Raffa, Robert B

    2009-10-01

    The mechanism of anticonvulsant action of topiramate includes inhibition of glutamate-activated ion channels. The evidence is most convincing for direct inhibitory action at the ionotropic AMPA (alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and kainate ((2S,3S,4S)-3-(Carboxymethyl)-4-prop-1-en-2-ylpyrrolidine-2-carboxylic acid) glutamate receptor subtypes. Less direct connection has been made to the NMDA (N-Methyl-d-aspartate) subtype. In the present study, we demonstrate that NMDA and AMPA produce concentration-dependent seizure-like activity in planarians, a type of flatworm which possesses mammalian-like neurotransmitters. In contrast, planarians exposed to the inhibitory amino acid, glycine, did not display pSLA. For combination experiments, topiramate significantly reduced planarian seizure-like activity (pSLA) produced by NMDA or AMPA. Additionally, NMDA-induced pSLA was antagonized by either an NMDA receptor antagonist (MK-801) or AMPA receptor antagonist (DNQX), thus suggesting that NMDA-induced pSLA was mediated by NMDA and non-NMDA receptors. The present results provide pharmacologic evidence of a functional inhibitory action of topiramate on glutamate receptor activity in invertebrates and provide a sensitive, quantifiable end-point for studying anti-seizure pharmacology.

  18. Involvement of AMPA receptors in the antidepressant-like effects of dextromethorphan in mice.

    PubMed

    Nguyen, Linda; Matsumoto, Rae R

    2015-12-15

    Dextromethorphan (DM) is an antitussive with rapid acting antidepressant potential based on pharmacodynamic similarities to ketamine. Building upon our previous finding that DM produces antidepressant-like effects in the mouse forced swim test (FST), the present study aimed to establish the antidepressant-like actions of DM in the tail suspension test (TST), another well-established model predictive of antidepressant efficacy. Additionally, using the TST and FST, we investigated the role of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors in the antidepressant-like properties of DM because accumulating evidence suggests that AMPA receptors play an important role in the pathophysiology of depression and may contribute to the efficacy of antidepressant medications, including that of ketamine. We found that DM displays antidepressant-like effects in the TST similar to the conventional and fast acting antidepressants characterized by imipramine and ketamine, respectively. Moreover, decreasing the first-pass metabolism of DM by concomitant administration of quinidine (CYP2D6 inhibitor) potentiated antidepressant-like actions, implying DM itself has antidepressant efficacy. Finally, in both the TST and FST, pretreatment with the AMPA receptor antagonist NBQX (2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide) significantly attenuated the antidepressant-like behavior elicited by DM. Together, the data show that DM exerts antidepressant-like actions through AMPA receptors, further suggesting DM may act as a safe and effective fast acting antidepressant drug.

  19. mTOR Is Essential for Corticosteroid Effects on Hippocampal AMPA Receptor Function and Fear Memory

    ERIC Educational Resources Information Center

    Xiong, Hui; Casse, Frédéric; Zhou, Yang; Zhou, Ming; Xiong, Zhi-Qi; Joëls, Marian; Martin, Stéphane; Krugers, Harm J.

    2015-01-01

    Glucocorticoid hormones, via activation of their receptors, promote memory consolidation, but the exact underlying mechanisms remain elusive. We examined how corticosterone regulates AMPA receptors (AMPARs), which are crucial for synaptic plasticity and memory formation. Combining a live imaging fluorescent recovery after photobleaching approach…

  20. A profile of the behavioral changes produced by facilitation of AMPA-type glutamate receptors.

    PubMed

    Davis, C M; Moskovitz, B; Nguyen, M A; Tran, B B; Arai, A; Lynch, G; Granger, R

    1997-09-01

    A newly developed group of benzoylpiperidine drugs that enhance AMPA-receptor-gated currents ("ampakines") has been shown to improve memory encoding in rats across a variety of experimental paradigms. The present experiments were intended to i) provide a partial profile of the behavioral changes produced by ampakines, ii) test if two ampakines (BDP-12 and BDP-20) that differ significantly in their effects on AMPA receptor kinetics produce similar behavioral profiles, and iii) determine if physiological potency is reflected in behavioral potency. BDP-20 reduced two measures of exploratory activity in aged rats but increased speed of performance in a radial maze; the drug also caused substantially improved retention of spatial information. These results are similar to those obtained with BDP-12, an analog that differs from BDP-20 in its effects on ligand binding to the AMPA receptor and on the physiological responses of the receptors to glutamate. BDP-20 was approximately ten-fold more potent in behavioral effects than BDP-12, which agrees with the relative potencies of the two drugs as assessed with excised patches and excitatory synaptic responses. These findings indicate that ampakines, though differing in their effects on AMPA-receptor-mediated responses, have similar effects at the behavioral level.

  1. Determination of glyphosate and AMPA on polyester-toner electrophoresis microchip with contactless conductivity detection.

    PubMed

    da Silva, Eduardo R; Segato, Thiago P; Coltro, Wendell K T; Lima, Renato S; Carrilho, Emanuel; Mazo, Luiz H

    2013-07-01

    This paper reports a method for rapid, simple, direct, and reproducible determination of glyphosate and its major metabolite aminomethylphosphonic acid (AMPA). The platform described herein uses polyester-toner microchips incorporating capacitively coupled contactless conductivity detection and electrophoresis separation of the analytes. The polyester-toner microchip presented 150 μm-wide and 12 μm-deep microchannels, with injection and separation lengths of 10 and 40 mm long, respectively. The best results were obtained with 320 kHz frequency, 4.5 Vpp excitation voltage, 80 mmol/L CHES/Tris buffer at pH 8.8, injection in -1.0 kV for 7 s, and separation in -1.5 kV. RSD values related to the peak areas for glyphosate and AMPA were 1.5 and 3.3% and 10.1 and 8.6% for intra- and interchip assays, respectively. The detection limits were 45.1 and 70.5 μmol/L, respectively, without any attempt of preconcentration of the analytes. Finally, the method was applied to river water samples in which glyphosate and AMPA (1.0 mmol/L each) were added. The recovery results were 87.4 and 83.7% for glyphosate and AMPA, respectively. The recovery percentages and LOD values obtained here were similar to others reported in the literature.

  2. AmpA protein functions by different mechanisms to influence early cell type specification and to modulate cell adhesion and actin polymerization in Dictyostelium discoideum.

    PubMed

    Cost, Hoa N; Noratel, Elizabeth F; Blumberg, Daphne D

    2013-01-01

    The Dictyostelium discoideum ampA gene encodes a multifunctional regulator protein that modulates cell-cell and cell-substrate adhesions and actin polymerization during growth and is necessary for correct cell type specification and patterning during development. Insertional inactivation of the ampA gene results in defects that define two distinct roles for the ampA gene during development. AmpA is necessary in a non-cell autonomous manner to prevent premature expression of a prespore gene marker. It is also necessary in a cell autonomous manner for the anterior like cells, which express the ampA gene, to migrate to the upper cup during culmination. It is also necessary to prevent excessive cell-cell agglutination when cells are developed in a submerged suspension culture. Here, we demonstrate that a supernatant source of AmpA protein, added extracellularly, can prevent the premature mis-expression of the prespore marker. Synthetic oligopeptides are used to identify the domain of the AmpA protein that is important for preventing cells from mis-expressing the prespore gene. We further demonstrate that a factor capable of inducing additional cells to express the prespore gene marker accumulates extracellularly in the absence of AmpA protein. While the secreted AmpA acts extracellularly to suppress prespore gene expression, the effects of AmpA on cell agglutination and on actin polymerization in growing cells are not due to an extracellular role of secreted AmpA protein. Rather, these effects appear to reflect a distinct cell autonomous role of the ampA gene. Finally, we show that secretion of AmpA protein is brought about by elevating the levels of expression of ampA so that the protein accumulates to an excessive level.

  3. Mathematical modelling of non-stationary fluctuation analysis for studying channel properties of synaptic AMPA receptors.

    PubMed

    Benke, T A; Lüthi, A; Palmer, M J; Wikström, M A; Anderson, W W; Isaac, J T; Collingridge, G L

    2001-12-01

    1. The molecular properties of synaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are an important factor determining excitatory synaptic transmission in the brain. Changes in the number (N) or single-channel conductance (gamma) of functional AMPA receptors may underlie synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). These parameters have been estimated using non-stationary fluctuation analysis (NSFA). 2. The validity of NSFA for studying the channel properties of synaptic AMPA receptors was assessed using a cable model with dendritic spines and a microscopic kinetic description of AMPA receptors. Electrotonic, geometric and kinetic parameters were altered in order to determine their effects on estimates of the underlying gamma. 3. Estimates of gamma were very sensitive to the access resistance of the recording (R(A)) and the mean open time of AMPA channels. Estimates of gamma were less sensitive to the distance between the electrode and the synaptic site, the electrotonic properties of dendritic structures, recording electrode capacitance and background noise. Estimates of gamma were insensitive to changes in spine morphology, synaptic glutamate concentration and the peak open probability (P(o)) of AMPA receptors. 4. The results obtained using the model agree with biological data, obtained from 91 dendritic recordings from rat CA1 pyramidal cells. A correlation analysis showed that R(A) resulted in a slowing of the decay time constant of excitatory postsynaptic currents (EPSCs) by approximately 150 %, from an estimated value of 3.1 ms. R(A) also greatly attenuated the absolute estimate of gamma by approximately 50-70 %. 5. When other parameters remain constant, the model demonstrates that NSFA of dendritic recordings can readily discriminate between changes in gamma vs. changes in N or P(o). Neither background noise nor asynchronous activation of multiple synapses prevented reliable

  4. The effects of AMPA blockade on the spectral profile of human early visual cortex recordings studied with non-invasive MEG.

    PubMed

    Muthukumaraswamy, Suresh D; Routley, Bethany; Droog, Wouter; Singh, Krish D; Hamandi, Khalid

    2016-08-01

    The generation of gamma-band (>30 Hz) cortical activity is thought to depend on the reciprocal connections of excitatory glutamatergic principal cells with inhibitory GABAergic interneurons. Both in vitro and in vivo animal studies have shown that blockade of glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors reduces the amplitude of gamma-band activity. In this registered report, we hypothesised that similar effects would be observed in humans following administration of perampanel, a first in class AMPA antagonist, used in the treatment of epilepsy. In a single-blind placebo-controlled crossover study, 20 healthy male participants completed two study days. On one day participants were given a 6 mg dose of perampanel and on the other an inactive placebo. magnetoencephalography (MEG) recordings of brain activity were taken before and two hours after drug administration, with activity in the visual cortex probed using a stimulation protocol known to induce gamma-band activity in the primary visual cortex. As hypothesised, our results indicated a decrease in gamma-band amplitudes following perampanel administration. The decreases in gamma-band amplitudes observed were temporally restricted to the early time-period of stimulus presentation (up to 400 msec) with no significant effects observed on early evoked responses or alpha rhythms. This suggests that the early time-window of induced visual gamma-band activity, thought to reflect input to the visual cortex from the lateral geniculate nucleus, is most sensitive to AMPA blocking drugs.

  5. Reciprocal inhibition of the AMPA and NMDA components of excitatory postsynaptic potentials in field CA1 of the rat hippocampus in vitro.

    PubMed

    Bazhenov, A V; Kleshchevnikov, A M

    1999-01-01

    The mutual effects of components of excitatory postsynaptic potentials (EPSP) induced by activation of glutamate receptors sensitive to alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) were studied on living slices of rat hippocampus. Evoked responses were recorded in the radial layer (stratum radialis) in field CA1 after stimulation of collateral-commissural fibers. The contribution of the NMDA component to the total EPSP was altered by extracellular application of solutions containing different concentrations of magnesium. At low magnesium concentrations, when both components made significant contributions to EPSP, inhibition of one of the components by application of antagonists of the appropriate receptors led to increases in the area of the other component. Thus, the total magnitude of pharmacologically isolated components were significantly greater than the control response (for example, at 0.1 mM magnesium, the sum of the components was 340 +/- 120% of the control two-component EPSP (p < 0.01; N = 6). These results suggest that in controls, the AMPA and NMDA components of EPSP inhibit each other. The mutual inhibition of components may be an important factor affecting the conductivity and plastic properties of central glutamatergic synaptic pathways.

  6. Synaptic Consolidation Normalizes AMPAR Quantal Size following MAGUK Loss.

    PubMed

    Levy, Jonathan M; Chen, Xiaobing; Reese, Thomas S; Nicoll, Roger A

    2015-08-05

    The mechanisms controlling synapse growth and maintenance are of critical importance for learning and memory. The MAGUK family of synaptic scaffolding proteins is abundantly expressed at glutamatergic central synapses, but their importance in controlling the synaptic content of glutamate receptors is poorly understood. Here, we use a chained RNAi-mediated knockdown approach to simultaneously remove PSD-93, PSD-95, and SAP102, the MAGUKs previously shown to be responsible for synaptic localization of glutamate receptors. We find that MAGUKs are specifically responsible for creating functional synapses after initial spine formation by filling functionally silent spines with glutamate receptors. Removal of the MAGUKs causes a transient reduction in AMPA receptor quantal size followed by synaptic consolidation resulting in a normalization of quantal size at the few remaining functional synapses. Consolidation requires signaling through L-type calcium channels, CaM kinase kinase, and the GluA2 AMPA receptor subunit, akin to a homeostatic process.

  7. Role of AMPA and NMDA receptors and back-propagating action potentials in spike timing-dependent plasticity.

    PubMed

    Fuenzalida, Marco; Fernández de Sevilla, David; Couve, Alejandro; Buño, Washington

    2010-01-01

    The cellular mechanisms that mediate spike timing-dependent plasticity (STDP) are largely unknown. We studied in vitro in CA1 pyramidal neurons the contribution of AMPA and N-methyl-d-aspartate (NMDA) components of Schaffer collateral (SC) excitatory postsynaptic potentials (EPSPs; EPSP(AMPA) and EPSP(NMDA)) and of the back-propagating action potential (BAP) to the long-term potentiation (LTP) induced by a STDP protocol that consisted in pairing an EPSP and a BAP. Transient blockade of EPSP(AMPA) with 7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile (CNQX) during the STDP protocol prevented LTP. Contrastingly LTP was induced under transient inhibition of EPSP(AMPA) by combining SC stimulation, an imposed EPSP(AMPA)-like depolarization, and BAP or by coupling the EPSP(NMDA) evoked under sustained depolarization (approximately -40 mV) and BAP. In Mg(2+)-free solution EPSP(NMDA) and BAP also produced LTP. Suppression of EPSP(NMDA) or BAP always prevented LTP. Thus activation of NMDA receptors and BAPs are needed but not sufficient because AMPA receptor activation is also obligatory for STDP. However, a transient depolarization of another origin that unblocks NMDA receptors and a BAP may also trigger LTP.

  8. Member of the Ampakine class of memory enhancers prolongs the single channel open time of reconstituted AMPA receptors.

    PubMed

    Suppiramaniam, V; Bahr, B A; Sinnarajah, S; Owens, K; Rogers, G; Yilma, S; Vodyanoy, V

    2001-05-01

    Ampakines are small benzamide compounds that allosterically produce the positive modulation of AMPA receptors and improve performance on a variety of behavioral tasks. To test if the native synaptic membrane is necessary for the effects of such positive modulators, the mechanism of action of the Ampakine 1-(1,3-benzodioxol-5-ylcarbonyl)-1,2,3,6-tetrahydropyridine (CX509) was investigated in isolated rat brain AMPA receptors reconstituted in lipid bilayers. The drug increased the open time of AMPA-induced single channel current fluctuations with an EC(50) of 4 microM. The action of CX509 was highly selective since it had no effect on the amplitude or close time of channel events. The open time effect had a maximum enhancement of 70-fold and the modulated currents were blocked by CNQX. It is concluded that the synaptic membrane environment is not necessary for Ampakine effects. In fact, CX509 was about 100 times more potent on the reconstituted AMPA receptors than on receptors in their native membrane. These findings indicate that centrally active Ampakines modulate specific kinetic properties of AMPA currents. They also raise the possibility that AMPA receptors are regulated by factors present in situ, thus explaining the more efficient modulatory effects of CX509 when acting on receptors removed from their synaptic location.

  9. Odor preference learning and memory modify GluA1 phosphorylation and GluA1 distribution in the neonate rat olfactory bulb: testing the AMPA receptor hypothesis in an appetitive learning model.

    PubMed

    Cui, Wen; Darby-King, Andrea; Grimes, Matthew T; Howland, John G; Wang, Yu Tian; McLean, John H; Harley, Carolyn W

    2011-01-01

    An increase in synaptic AMPA receptors is hypothesized to mediate learning and memory. AMPA receptor increases have been reported in aversive learning models, although it is not clear if they are seen with memory maintenance. Here we examine AMPA receptor changes in a cAMP/PKA/CREB-dependent appetitive learning model: odor preference learning in the neonate rat. Rat pups were given a single pairing of peppermint and 2 mg/kg isoproterenol, which produces a 24-h, but not a 48-h, peppermint preference in the 7-d-old rat pup. GluA1 PKA-dependent phosphorylation peaked 10 min after the 10-min training trial and returned to baseline within 90 min. At 24 h, GluA1 subunits did not change overall but were significantly increased in synaptoneurosomes, consistent with increased membrane insertion. Immunohistochemistry revealed a significant increase in GluA1 subunits in olfactory bulb glomeruli, the targets of olfactory nerve axons. Glomerular increases were seen at 3 and 24 h after odor exposure in trained pups, but not in control pups. GluA1 increases were not seen as early as 10 min after training and were no longer observed 48 h after training when odor preference is no longer expressed behaviorally. Thus, the pattern of increased GluA1 membrane expression closely follows the memory timeline. Further, blocking GluA1 insertion using an interference peptide derived from the carboxyl tail of the GluA1 subunit inhibited 24 h odor preference memory providing causative support for our hypothesis. PKA-mediated GluA1 phosphorylation and later GluA1 insertion could, conjointly, provide increased AMPA function to support both short-term and long-term appetitive memory.

  10. Ionotropic AMPA-type glutamate and metabotropic GABAB receptors: determining cellular physiology by proteomes.

    PubMed

    Bettler, Bernhard; Fakler, Bernd

    2017-03-07

    Ionotropic AMPA-type glutamate receptors and G-protein-coupled metabotropic GABAB receptors are key elements of neurotransmission whose cellular functions are determined by their protein constituents. Over the past couple of years unbiased proteomic approaches identified comprehensive sets of protein building blocks of these two types of neurotransmitter receptors in the brain (termed receptor proteomes). This provided the opportunity to match receptor proteomes with receptor physiology and to study the structural organization, regulation and function of native receptor complexes in an unprecedented manner. In this review we discuss the principles of receptor architecture and regulation emerging from the functional characterization of the proteomes of AMPA and GABAB receptors. We also highlight progress in unraveling the role of unexpected protein components for receptor physiology.

  11. Reconsolidation of Reminder-Induced Amnesia: Role of NMDA and AMPA Glutamate Receptors.

    PubMed

    Nikitin, V P; Kozyrev, S A; Solntseva, S V

    2015-11-01

    We studied the role of glutamate receptors and reminder in the mechanisms of amnesia maintenance caused by disruption of conditioned food aversion reconsolidation with an antagonist of NMDA glutamate receptor in snails. At the early stage of amnesia (day 3 after induction), injection or NMDA of AMPA glutamate receptor antagonists prior to reminder (presentation of the conditioned food stimulus) led to memory recovery. Reminder alone or injection of antagonists without reminder or after reminder was ineffective. At the late stage of amnesia (day 10), antagonists/reminder had no effect on amnesia maintenance. It was hypothesized that reminder at the early stage of amnesia led to reactivation and reconsolidation of the molecular processes of amnesia including activation NMDA and AMPA glutamate receptors. Injection of antagonists of these receptors prior to reminder led to disruption of reactivation/reconsolidation of amnesia and recovery of the conditioned food aversion memory.

  12. Differential trafficking of AMPA receptors following activation of NMDA receptors and mGluRs.

    PubMed

    Sanderson, Thomas M; Collingridge, Graham L; Fitzjohn, Stephen M

    2011-07-27

    The removal of AMPA receptors from synapses is a major component of long-term depression (LTD). How this occurs, however, is still only partially understood. To investigate the trafficking of AMPA receptors in real-time we previously tagged the GluA2 subunit of AMPA receptors with ecliptic pHluorin and studied the effects of NMDA receptor activation. In the present study we have compared the effect of NMDA receptor and group I mGluR activation, using GluA2 tagged with super ecliptic pHluorin (SEP-GluA2) expressed in cultured hippocampal neurons. Surprisingly, agonists of the two receptors, which are both able to induce chemical forms of LTD, had clearly distinct effects on AMPA receptor trafficking. In agreement with our previous work we found that transient NMDA receptor activation results in an initial decrease in surface GluA2 from extrasynaptic sites followed by a delayed reduction in GluA2 from puncta (putative synapses). In contrast, transient activation of group I mGluRs, using DHPG, led to a pronounced but more delayed decrease in GluA2 from the dendritic shafts. Surprisingly, there was no average change in the fluorescence of the puncta. Examination of fluorescence at individual puncta, however, indicated that alterations did take place, with some puncta showing an increase and others a decrease in fluorescence. The effects of DHPG were, like DHPG-induced LTD, prevented by treatment with a protein tyrosine phosphatase (PTP) inhibitor. The electrophysiological correlate of the effects of DHPG in the SEP-GluA2 infected cultures was a reduction in mEPSC frequency with no change in amplitude. The implications of these findings for the initial mechanisms of expression of both NMDA receptor- and mGluR-induced LTD are discussed.

  13. Discovery and Characterization of AMPA Receptor Modulators Selective for TARP-γ8.

    PubMed

    Maher, Michael P; Wu, Nyantsz; Ravula, Suchitra; Ameriks, Michael K; Savall, Brad M; Liu, Changlu; Lord, Brian; Wyatt, Ryan M; Matta, Jose A; Dugovic, Christine; Yun, Sujin; Ver Donck, Luc; Steckler, Thomas; Wickenden, Alan D; Carruthers, Nicholas I; Lovenberg, Timothy W

    2016-05-01

    Members of the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) subtype of ionotropic glutamate receptors mediate the majority of fast synaptic transmission within the mammalian brain and spinal cord, representing attractive targets for therapeutic intervention. Here, we describe novel AMPA receptor modulators that require the presence of the accessory protein CACNG8, also known as transmembrane AMPA receptor regulatory protein γ8 (TARP-γ8). Using calcium flux, radioligand binding, and electrophysiological assays of wild-type and mutant forms of TARP-γ8, we demonstrate that these compounds possess a novel mechanism of action consistent with a partial disruption of the interaction between the TARP and the pore-forming subunit of the channel. One of the molecules, 5-[2-chloro-6-(trifluoromethoxy)phenyl]-1,3-dihydrobenzimidazol-2-one (JNJ-55511118), had excellent pharmacokinetic properties and achieved high receptor occupancy following oral administration. This molecule showed strong, dose-dependent inhibition of neurotransmission within the hippocampus, and a strong anticonvulsant effect. At high levels of receptor occupancy in rodent in vivo models, JNJ-55511118 showed a strong reduction in certain bands on electroencephalogram, transient hyperlocomotion, no motor impairment on rotarod, and a mild impairment in learning and memory. JNJ-55511118 is a novel tool for reversible AMPA receptor inhibition, particularly within the hippocampus, with potential therapeutic utility as an anticonvulsant or neuroprotectant. The existence of a molecule with this mechanism of action demonstrates the possibility of pharmacological targeting of accessory proteins, increasing the potential number of druggable targets.

  14. Distribution of transmembrane AMPA receptor regulatory protein (TARP) isoforms in the rat spinal cord.

    PubMed

    Larsson, M; Agalave, N; Watanabe, M; Svensson, C I

    2013-09-17

    The transmembrane α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor regulatory proteins (TARPs) are a family of auxiliary AMPA receptor subunits that differentially modulate trafficking and many functional properties of the receptor. To investigate which TARP isoforms may be involved in AMPA receptor-mediated spinal synaptic transmission, we have mapped the localization of five of the known TARP isoforms, namely γ-2 (also known as stargazin), γ-3, γ-4, γ-7 and γ-8, in the rat spinal cord. Immunoblotting showed expression of all isoforms in the spinal cord to varying degrees. At the light microscopic level, immunoperoxidase labeling of γ-4, γ-7 and γ-8 was found throughout spinal gray matter. In white matter, γ-4 and γ-7 immunolabeling was observed in astrocytic processes and in mature oligodendrocytes. In pepsin-treated spinal cord, γ-7 often colocalized with GluA2 immunopositive puncta in the deep dorsal horn as well as in the ventral horn, but not in the superficial dorsal horn. Postembedding immunogold labeling was further used to assess the synaptic localization of γ-2, γ-7 and γ-8 in the dorsal horn. Synaptic immunogold labeling of γ-2 was sparse throughout the dorsal horn, with some primary afferent synapses weakly labeled, whereas relatively strong γ-7 immunogold labeling was found at deep dorsal horn synapses, including at synapses formed by low-threshold mechanosensitive primary afferent terminals. Prominent immunogold labeling of γ-8 was frequently detected at synapses established by primary afferent fibers. The spinal localization patterns of TARP isoforms reported here suggest that AMPA receptors at spinal synaptic populations and in glial cells may exhibit different functional characteristics owing to differences in auxiliary subunit composition.

  15. Differential palmitoylation directs the AMPA receptor-binding protein ABP to spines or to intracellular clusters.

    PubMed

    DeSouza, Sunita; Fu, Jie; States, Bradley A; Ziff, Edward B

    2002-05-01

    Long-term changes in excitatory synapse strength are thought to reflect changes in synaptic abundance of AMPA receptors mediated by receptor trafficking. AMPA receptor-binding protein (ABP) and glutamate receptor-interacting protein (GRIP) are two similar PDZ (postsynaptic density 95/Discs large/zona occludens 1) proteins that interact with glutamate receptors 2 and 3 (GluR2 and GluR3) subunits. Both proteins have proposed roles during long-term potentiation and long-term depression in the delivery and anchorage of AMPA receptors at synapses. Here we report a variant of ABP-L (seven PDZ form of ABP) called pABP-L that is palmitoylated at a cysteine residue at position 11 within a novel 18 amino acid N-terminal leader sequence encoded through differential splicing. In cultured hippocampal neurons, nonpalmitoylated ABP-L localizes with internal GluR2 pools expressed from a Sindbis virus vector, whereas pABP-L is membrane targeted and associates with surface-localized GluR2 receptors at the plasma membrane in spines. Mutation of Cys-11 to alanine blocks the palmitoylation of pABP-L and targets the protein to intracellular clusters, confirming that targeting the protein to spines is dependent on palmitoylation. Non-palmitoylated GRIP is primarily intracellular, but a chimera with the pABP-L N-terminal palmitoylation sequence linked to the body of the GRIP protein is targeted to spines. We suggest that pABP-L and ABP-L provide, respectively, synaptic and intracellular sites for the anchorage of AMPA receptors during receptor trafficking to and from the synapse.

  16. Glutamate receptors on myelinated spinal cord axons: II)AMPA and GluR5 receptors

    PubMed Central

    Ouardouz, M.; Coderre, E.; Zamponi, G. W.; Hameed, S.; Yin, X.; Trapp, B.D.; Stys, P.K.

    2010-01-01

    Objective Glutamate receptors, which play a major role in the physiology and pathology of CNS gray matter, are also involved in the pathophysiology of white matter. However the cellular and molecular mechanisms responsible for excitotoxic damage to white matter elements are not fully understood. We explored the roles of AMPA and GluR5 kainate receptors in axonal Ca2+ deregulation. Methods Dorsal column axons were loaded with a Ca2+ indicator and imaged in vitro using confocal microscopy. Results Both AMPA and a GluR5 kainate receptor agonists increased intra-axonal Ca2+ in myelinated rat dorsal column fibers. These responses were inhibited by selective antagonists of these glutamate receptors. The GluR5-mediated Ca2+ rise was mediated by both canonical (i.e. ionotropic) and non-canonical (metabotropic) signalling, dependent on a pertussis toxin-sensitive G protein and a phospholipase C-dependent pathway, promoting Ca2+ release from IP3-dependent stores. Additionally, the GluR5 response was significantly reduced by intra-axonal NO scavengers. In contrast, GluR4 AMPA receptors operated via Ca2+ induced Ca2+ release, dependent on ryanodine receptors, and unaffected by NO scavengers. Neither pathway depended on L-type Ca2+ channels, in contrast to GlurR6 kainate receptor action 1. Immunohistochemistry confirmed the presence of GluR4 and GluR5 clustered at the surface of myelinated axons; GluR5 co-immunoprecipitated with nNOS and often co-localized with nNOS clusters on the internodal axon. Interpretation Central myelinated axons express functional AMPA and GluR5 kainate receptors, and can directly respond to glutamate receptor agonists. These glutamate receptor-dependent signalling pathways promote an increase in intra-axonal Ca2+ levels potentially contributing to axonal degeneration. PMID:19224531

  17. EM colocalization of AMPA and NMDA receptor subunits at synapses in rat cerebral cortex.

    PubMed

    Kharazia, V N; Phend, K D; Rustioni, A; Weinberg, R J

    1996-05-24

    Electrophysiology and light microscopy suggest that a single excitatory synapse may use both amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors. Using immunogold electron microscopy, we here provide direct evidence for colocalization at individual synapses in sensorimotor cortex of adult rats. Colocalization was most commonly observed on dendritic spines; subunits of the two classes of receptors seemed to be independently distributed within the synaptic active zone.

  18. Ca(2+) -permeable AMPA receptors associated with epileptogenesis of hypothalamic hamartoma.

    PubMed

    Kitaura, Hiroki; Sonoda, Masaki; Teramoto, Sayaka; Shirozu, Hiroshi; Shimizu, Hiroshi; Kimura, Tadashi; Masuda, Hiroshi; Ito, Yosuke; Takahashi, Hitoshi; Kwak, Shin; Kameyama, Shigeki; Kakita, Akiyoshi

    2017-04-01

    Hypothalamic hamartoma (HH), composed of neurons and glia without apparent cytologic abnormalities, is a rare developmental malformation in humans. Patients with HH often have characteristic medically refractory gelastic seizures, and intrinsic epileptogenesis within the lesions has been speculated. Herein we provide evidence to suggest that in HH neurons, Ca(2+) permeability through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors is aberrantly elevated. In needle biopsy specimens of HH tissue, field potential recordings demonstrated spontaneous epileptiform activities similar to those observed in other etiologically distinct epileptogenic tissues. In HH, however, these activities were clearly abolished by application of Joro Spider Toxin (JSTX), a specific inhibitor of the Ca(2+) -permeable AMPA receptor. Consistent with these physiologic findings, the neuronal nuclei showed disappearance of adenosine deaminase acting on RNA 2 (ADAR2) immunoreactivity. Furthermore, examination of glutamate receptor 2 (GluA2) messenger RNA (mRNA) revealed that editing efficiency at the glutamine/arginine site was significantly low. These results suggest that neurons in HH may bear Ca(2+) -permeable AMPA receptors due to dislocation of ADAR2.

  19. The influence of synaptic size on AMPA receptor activation: a Monte Carlo model.

    PubMed

    Montes, Jesus; Peña, Jose M; DeFelipe, Javier; Herreras, Oscar; Merchan-Perez, Angel

    2015-01-01

    Physiological and electron microscope studies have shown that synapses are functionally and morphologically heterogeneous and that variations in size of synaptic junctions are related to characteristics such as release probability and density of postsynaptic AMPA receptors. The present article focuses on how these morphological variations impact synaptic transmission. We based our study on Monte Carlo computational simulations of simplified model synapses whose morphological features have been extracted from hundreds of actual synaptic junctions reconstructed by three-dimensional electron microscopy. We have examined the effects that parameters such as synaptic size or density of AMPA receptors have on the number of receptors that open after release of a single synaptic vesicle. Our results indicate that the maximum number of receptors that will open after the release of a single synaptic vesicle may show a ten-fold variation in the whole population of synapses. When individual synapses are considered, there is also a stochastical variability that is maximal in small synapses with low numbers of receptors. The number of postsynaptic receptors and the size of the synaptic junction are the most influential parameters, while the packing density of receptors or the concentration of extrasynaptic transporters have little or no influence on the opening of AMPA receptors.

  20. The Influence of Synaptic Size on AMPA Receptor Activation: A Monte Carlo Model

    PubMed Central

    Montes, Jesus; Peña, Jose M.; DeFelipe, Javier; Herreras, Oscar; Merchan-Perez, Angel

    2015-01-01

    Physiological and electron microscope studies have shown that synapses are functionally and morphologically heterogeneous and that variations in size of synaptic junctions are related to characteristics such as release probability and density of postsynaptic AMPA receptors. The present article focuses on how these morphological variations impact synaptic transmission. We based our study on Monte Carlo computational simulations of simplified model synapses whose morphological features have been extracted from hundreds of actual synaptic junctions reconstructed by three-dimensional electron microscopy. We have examined the effects that parameters such as synaptic size or density of AMPA receptors have on the number of receptors that open after release of a single synaptic vesicle. Our results indicate that the maximum number of receptors that will open after the release of a single synaptic vesicle may show a ten-fold variation in the whole population of synapses. When individual synapses are considered, there is also a stochastical variability that is maximal in small synapses with low numbers of receptors. The number of postsynaptic receptors and the size of the synaptic junction are the most influential parameters, while the packing density of receptors or the concentration of extrasynaptic transporters have little or no influence on the opening of AMPA receptors. PMID:26107874

  1. Memory retrieval requires ongoing protein synthesis and NMDA receptor activity-mediated AMPA receptor trafficking.

    PubMed

    Lopez, Joëlle; Gamache, Karine; Schneider, Rilla; Nader, Karim

    2015-02-11

    Whereas consolidation and reconsolidation are considered dynamic processes requiring protein synthesis, memory retrieval has long been considered a passive readout of previously established plasticity. However, previous findings suggest that memory retrieval may be more dynamic than previously thought. This study therefore aimed at investigating the molecular mechanisms underlying memory retrieval in the rat. Infusion of protein synthesis inhibitors (rapamycin or anisomycin) in the amygdala 10 min before memory retrieval transiently impaired auditory fear memory expression, suggesting ongoing protein synthesis is required to enable memory retrieval. We then investigated the role of protein synthesis in NMDA receptor activity-mediated AMPA receptor trafficking. Coinfusion of an NMDA receptor antagonist (ifenprodil) or infusion of an AMPA receptor endocytosis inhibitor (GluA23Y) before rapamycin prevented this memory impairment. Furthermore, rapamycin transiently decreased GluA1 levels at the postsynaptic density (PSD), but did not affect extrasynaptic sites. This effect at the PSD was prevented by an infusion of GluA23Y before rapamycin. Together, these data show that ongoing protein synthesis is required before memory retrieval is engaged, and suggest that this protein synthesis may be involved in the NMDAR activity-mediated trafficking of AMPA receptors that takes place during memory retrieval.

  2. in Silico investigation of the structural requirements for the AMPA receptor antagonism by quinoxaline derivatives.

    PubMed

    Azam, Faizul; Abugrain, Ismaiel Mohamed; Sanalla, Mohamed Hussin; Elnaas, Radwan Fatahalla; Rajab, Ibrahim Abdassalam Ibn

    2013-01-01

    Glutamate receptors have been implicated in various neurological disorders and their antagonism offers a suitable approach for the treatment of such disorders. The field of drug design and discovery aims to find best medicines to prevent, treat and cure diseases quickly and efficiently. In this regard, computational tools have helped medicinal chemists modify and optimize molecules to potent drug candidates with better pharmacokinetic profiles, and guiding biologists and pharmacologists to explore new disease genes as well as novel drug targets. In the present study, to understand the structural requirements for AMPA receptor antagonism, molecular docking study was performed on 41 structurally diverse antagonists based on quinoxaline nucleus. Lamarckian genetic algorithm methodology was employed for docking simulations using AutoDock 4.2 program. The results obtained signify that the molecular docking approach is reliable and produces a good correlation coefficient (r(2) = 0.6) between experimental and docking predicted AMPA receptor antagonistic activity. The aromatic moiety of quinoxaline core has been proved to be vital for hydrophobic contacts exhibiting - interactions in docked conformations. However, polar moieties such as carboxylic group and 1,2,4-triazole moieties were noted to be sites for hydrophilic interactions in terms of hydrogen bonding with the receptor. These analyses can be exploited to design and develop novel AMPA receptor antagonists for the treatment of different neurological disorders.

  3. X-ray structures of AMPA receptor-cone snail toxin complexes illuminate activation mechanism.

    PubMed

    Chen, Lei; Dürr, Katharina L; Gouaux, Eric

    2014-08-29

    AMPA-sensitive glutamate receptors are crucial to the structural and dynamic properties of the brain, to the development and function of the central nervous system, and to the treatment of neurological conditions from depression to cognitive impairment. However, the molecular principles underlying AMPA receptor activation have remained elusive. We determined multiple x-ray crystal structures of the GluA2 AMPA receptor in complex with a Conus striatus cone snail toxin, a positive allosteric modulator, and orthosteric agonists, at 3.8 to 4.1 angstrom resolution. We show how the toxin acts like a straightjacket on the ligand-binding domain (LBD) "gating ring," restraining the domains via both intra- and interdimer cross-links such that agonist-induced closure of the LBD "clamshells" is transduced into an irislike expansion of the gating ring. By structural analysis of activation-enhancing mutants, we show how the expansion of the LBD gating ring results in pulling forces on the M3 helices that, in turn, are coupled to ion channel gating.

  4. Synergy of AMPA and NMDA Receptor Currents in Dopaminergic Neurons: A Modeling Study

    PubMed Central

    Zakharov, Denis; Lapish, Christopher; Gutkin, Boris; Kuznetsov, Alexey

    2016-01-01

    Dopaminergic (DA) neurons display two modes of firing: low-frequency tonic and high-frequency bursts. The high frequency firing within the bursts is attributed to NMDA, but not AMPA receptor activation. In our models of the DA neuron, both biophysical and abstract, the NMDA receptor current can significantly increase their firing frequency, whereas the AMPA receptor current is not able to evoke high-frequency activity and usually suppresses firing. However, both currents are produced by glutamate receptors and, consequently, are often co-activated. Here we consider combined influence of AMPA and NMDA synaptic input in the models of the DA neuron. Different types of neuronal activity (resting state, low frequency, or high frequency firing) are observed depending on the conductance of the AMPAR and NMDAR currents. In two models, biophysical and reduced, we show that the firing frequency increases more effectively if both receptors are co-activated for certain parameter values. In particular, in the more quantitative biophysical model, the maximal frequency is 40% greater than that with NMDAR alone. The dynamical mechanism of such frequency growth is explained in the framework of phase space evolution using the reduced model. In short, both the AMPAR and NMDAR currents flatten the voltage nullcline, providing the frequency increase, whereas only NMDA prevents complete unfolding of the nullcline, providing robust firing. Thus, we confirm a major role of the NMDAR in generating high-frequency firing and conclude that AMPAR activation further significantly increases the frequency. PMID:27252643

  5. FUNCTIONAL INSIGHT INTO DEVELOPMENT OF POSITIVE ALLOSTERIC MODULATORS OF AMPA RECEPTORS

    PubMed Central

    Weeks, Autumn M.; Harms, Jonathan E.; Partin, Kathryn M.; Benveniste, Morris

    2014-01-01

    Positive allosteric modulators of α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) ionotropic glutamate receptors facilitate synaptic plasticity and contribute essentially to learning and memory, properties which make AMPA receptors targets for drug discovery and development. One region at which several different classes of positive allosteric modulators bind lies at the dimer interface between the ligand-binding core of the second, membrane-proximal, extracellular domain of AMPA receptors. This solvent-accessible binding pocket has been the target of drug discovery efforts, leading to the recent delineation of five “subsites” which differentially allow access to modulator moieties, and for which distinct modulator affinities and apparent efficacies are attributed. Here we use the voltage-clamp technique in conjunction with rapid drug application to study the effects of mutants lining subsites “A” and “B” of the allosteric modulator pocket to assess affinity and efficacy of allosteric modulation by cyclothiazide, CX614, CMPDA and CMPDB. A novel analysis of the decay of current produced by the onset of desensitization has allowed us to estimate both affinity and efficacy from single concentrations of modulator. Such an approach may be useful for effective high throughput screening of new target compounds. PMID:24878241

  6. Functional insight into development of positive allosteric modulators of AMPA receptors.

    PubMed

    Weeks, Autumn M; Harms, Jonathan E; Partin, Kathryn M; Benveniste, Morris

    2014-10-01

    Positive allosteric modulators of α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) ionotropic glutamate receptors facilitate synaptic plasticity and contribute essentially to learning and memory, properties which make AMPA receptors targets for drug discovery and development. One region at which several different classes of positive allosteric modulators bind lies at the dimer interface between the ligand-binding core of the second, membrane-proximal, extracellular domain of AMPA receptors. This solvent-accessible binding pocket has been the target of drug discovery efforts, leading to the recent delineation of five "subsites" which differentially allow access to modulator moieties, and for which distinct modulator affinities and apparent efficacies are attributed. Here we use the voltage-clamp technique in conjunction with rapid drug application to study the effects of mutants lining subsites "A" and "B" of the allosteric modulator pocket to assess affinity and efficacy of allosteric modulation by cyclothiazide, CX614, CMPDA and CMPDB. A novel analysis of the decay of current produced by the onset of desensitization has allowed us to estimate both affinity and efficacy from single concentrations of modulator. Such an approach may be useful for effective high throughput screening of new target compounds.

  7. Precision therapy for a new disorder of AMPA receptor recycling due to mutations in ATAD1

    PubMed Central

    Ahrens-Nicklas, Rebecca C.; Umanah, George K.E.; Sondheimer, Neal; Deardorff, Matthew A.; Wilkens, Alisha B.; Conlin, Laura K.; Santani, Avni B.; Nesbitt, Addie; Juulsola, Jane; Ma, Erica; Dawson, Ted M.; Dawson, Valina L.

    2017-01-01

    Objective: ATAD1 encodes Thorase, a mediator of α-amino-3-hydroxy-5-methylisoxazole-4-proprionate (AMPA) receptor recycling; in this work, we characterized the phenotype resulting from ATAD1 mutations and developed a targeted therapy in both mice and humans. Methods: Using exome sequencing, we identified a novel ATAD1 mutation (p.E276X) as the etiology of a devastating neurologic disorder characterized by hypertonia, seizures, and death in a consanguineous family. We postulated that pathogenesis was a result of excessive AMPA receptor activity and designed a targeted therapeutic approach using perampanel, an AMPA-receptor antagonist. Results: Perampanel therapy in ATAD1 knockout mice reversed behavioral defects, normalized brain MRI abnormalities, prevented seizures, and prolonged survival. The ATAD1 patients treated with perampanel showed improvement in hypertonicity and resolution of seizures. Conclusions: This work demonstrates that identification of novel monogenic neurologic disorders and observation of response to targeted therapeutics can provide important insights into human nervous system functioning. PMID:28180185

  8. Influence of AMPA/kainate receptors on extracellular 5-hydroxytryptamine in rat midbrain raphe and forebrain

    PubMed Central

    Tao, Rui; Ma, Zhiyuan; Auerbach, Sidney B

    1997-01-01

    The regulation of 5-hydroxytryptamine (5-HT) release by excitatory amino acid (EAA) receptors was examined by use of microdialysis in the CNS of freely behaving rats. Extracellular 5-HT was measured in the dorsal raphe nucleus (DRN), median raphe nucleus (MRN), nucleus accumbens, hypothalamus, frontal cortex, dorsal and ventral hippocampus. Local infusion of kainate produced increases in extracellular 5-HT in the DRN and MRN. Kainate infusion into forebrain sites had a less potent effect. In further studies of the DRN and nucleus accumbens, kainate-induced increases in extracellular 5-HT were blocked by the EAA receptor antagonists, kynurenate and 6,7-dinitroquinoxaline-2,3-dione (DNQX). The effect of infusing kainate into the DRN or nucleus accumbens was attenuated or abolished by tetrodotoxin (TTX), suggesting that the increase in extracellular 5-HT is dependent on 5-HT neuronal activity. In contrast, ibotenate-induced lesion of intrinsic neurones did not attenuate the effect of infusing kainate into the nucleus accumbens. Thus, the effect of kainate in the nucleus accumbens does not depend on intrinsic neurones. Infusion of α-amino-3-hydroxy-5-methyl-4-isoxazolaproprionate (AMPA) into the DRN and nucleus accumbens induced nonsignificant changes in extracellular 5-HT. Cyclothiazide and diazoxide, which attenuate receptor desensitization, greatly enhanced the effect of AMPA on 5-HT in the DRN, but not in the nucleus accumbens. In conclusion, AMPA/kainate receptors regulate 5-HT in the raphe and in forebrain sites. PMID:9283707

  9. Immunohistochemical Localization of AMPA Type Glutamate Receptor Subunits in the Striatum of Rhesus Monkey

    PubMed Central

    Deng, Yun-Ping; Shelby, Evan; Reiner, Anton J.

    2010-01-01

    Corticostriatal and thalamostriatal projections utilize glutamate as their neurotransmitter. Their influence on striatum is mediated, in part, by ionotropic AMPA-type glutamate receptors, which are heteromers composed of GluR1-4 subunits. While the cellular localization of AMPA-type subunits in the basal ganglia has been well characterized in rodents, the cellular localization of AMPA subunits in primate basal ganglia is not. We thus carried out immunohistochemical studies of GluR1-4 distribution in rhesus monkey basal ganglia in conjunction with characterization of each major neuron type. In striatum, about 65% of striatal neurons immunolabeled for GluR1, 75%-79% immunolabeled for GluR2 or GluR2/3, and only 2.5% possessed GluR4. All neurons the large size of cholinergic interneurons (mean diameter 26.1μm) were moderately labeled for GluR1, while all neurons in the size range of parvalbuminergic interneurons (mean diameter 13.8μm) were intensely rich in GluR1. Additionally, somewhat more than half of neurons in the size range of projection neurons (mean diameter 11.6μm) immunolabeled for GluR1, and about one third of these were very rich in GluR1. About half of neurons the size of cholinergic interneurons were immunolabeled for GluR2, and the remainder of the neurons that were immunolabeled for GluR2 coincided with projection neurons in size and shape (GluR2 diameter=10.7μm), indicating that the vast majority of striatal projection neurons possess immunodectible GluR2. Similar results were observed with GluR2/3 immunolabeling. Half of the neurons the size of cholinergic interneurons immunolabeled for GluR4 and seemingly all neurons in the size range of parvalbuminergic interneurons possessed GluR4. These results indicate that AMPA receptor subunit combinations for striatal projection neurons in rhesus monkey are similar to those for the corresponding neuron types in rodents, and thus their AMPA responses to glutamate likely to be similar to those demonstrated

  10. Enhancement of AMPA currents and GluR1 membrane expression through PKA-coupled adenosine A(2A) receptors.

    PubMed

    Dias, Raquel B; Ribeiro, Joaquim A; Sebastião, Ana M

    2012-02-01

    Phosphorylation of glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors by Protein Kinase A (PKA) is known to regulate AMPA receptor (AMPAR) trafficking and stabilization at the postsynaptic membrane, which in turn is one of the key mechanisms by which synaptic transmission and plasticity are tuned. However, not much is known as to how Gs-coupled receptors contribute to endogenous PKA-mediated regulation of AMPA receptor function. Here we report that activation of the excitatory A(2A) adenosine receptor by 2-[4-(2-p-carboxyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680, 1-30 nM) facilitates AMPA-evoked currents in CA1 pyramidal neurons, by a mechanism dependent on PKA activation, but not on protein synthesis. This modulation of AMPA currents was mimicked by forskolin (1 μM) and did not occur in stratum radiatum interneurons. Superfusion of the A(2A) receptor agonist also caused an increase in the amplitude of miniature excitatory postsynaptic currents (mEPSCs), as well as in the membrane levels of GluR1 subunits phosphorylated at the PKA site (Ser845). The impact of this increase on GluR1-containing AMPA receptor expression was evidenced by the potentiation of LTP at the CA3-CA1 synapse that followed brief activation of A(2A) receptors. We thus propose that in conditions of increased adenosine availability, A(2A) receptor activation is responsible for setting part of the endogenous GluR1 Ser-845 phosphorylation tonus and hence, the availability of the GluR1-containing AMPA receptor extrasynaptic pool for synaptic insertion and reinforcement of synaptic strength.

  11. Actin/alpha-actinin-dependent transport of AMPA receptors in dendritic spines: role of the PDZ-LIM protein RIL.

    PubMed

    Schulz, Torsten W; Nakagawa, Terunaga; Licznerski, Pawel; Pawlak, Verena; Kolleker, Alexander; Rozov, Andrei; Kim, Jinhyun; Dittgen, Tanjew; Köhr, Georg; Sheng, Morgan; Seeburg, Peter H; Osten, Pavel

    2004-09-29

    The efficacy of excitatory transmission in the brain depends to a large extent on synaptic AMPA receptors, hence the importance of understanding the delivery and recycling of the receptors at the synaptic sites. Here we report a novel regulation of the AMPA receptor transport by a PDZ (postsynaptic density-95/Drosophila disc large tumor suppressor zona occludens 1) and LIM (Lin11/rat Isl-1/Mec3) domain-containing protein, RIL (reversion-induced LIM protein). We show that RIL binds to the AMPA glutamate receptor subunit GluR-A C-terminal peptide via its LIM domain and to alpha-actinin via its PDZ domain. RIL is enriched in the postsynaptic density fraction isolated from rat forebrain, strongly localizes to dendritic spines in cultured neurons, and coprecipitates, together with alpha-actinin, in a protein complex isolated by immunoprecipitation of AMPA receptors from forebrain synaptosomes. Functionally, in heterologous cells, RIL links AMPA receptors to the alpha-actinin/actin cytoskeleton, an effect that appears to apply selectively to the endosomal surface-internalized population of the receptors. In cultured neurons, an overexpression of recombinant RIL increases the accumulation of AMPA receptors in dendritic spines, both at the total level, as assessed by immunodetection of endogenous GluR-A-containing receptors, and at the synaptic surface, as assessed by recording of miniature EPSCs. Our results thus indicate that RIL directs the transport of GluR-A-containing AMPA receptors to and/or within dendritic spines, in an alpha-actinin/actin-dependent manner, and that such trafficking function promotes the synaptic accumulation of the receptors.

  12. Sources and Input Pathways of Glyphosate and its Degradation Product AMPA

    NASA Astrophysics Data System (ADS)

    Bischofberger, S.; Hanke, I.; Wittmer, I.; Singer, H.; Stamm, C.

    2009-04-01

    Despite being the pesticide used in the largest quantities worldwide, the environmental relevance of glyphosate has been considered low for many years. Reasons for this assessment were the observations that glyphosate degrades quickly into its degradation product AMPA and that it sorbs strongly to soil particles. Hence, little losses to water bodies had been expected. Research during the last few years however contradicts this expectation. Although glyphosate is a dominant pesticide used in agriculture, recent studies on other pesticides revealed that urban sources may play a significant role for water quality. Therefore this study compares glyphosate input into streams from agricultural and urban sources. For that purpose, a catchment of an area of 25 km2 was selected. It has by about 12'000 inhabitants and about 15 % of the area is used as arable land. Four sampling sites were selected in the river system in order to reflect different urban and agricultural sources. Additionally, we sampled a combined sewer overflow, a rain sewer and the outflow of a waste water treatment plant. At each site discharge was measured continuously from March to November 2007. During 16 rain events samples were taken by automatic devices at a high temporal resolution. To analyze the concentration of glyphosate and its degradation product AMPA, the samples were derivatized with FMOC-Cl at low pH conditions and then filtrated. The solid phase extraction was conducted with Strata-X sorbent cartridge. Glyphosate and AMPA were detected with API 4000 after the chromatography with X bridge column C18. To assure the data quality, interne standards of Glyphosate and AMPA were added to every sample. The limit of detection and quantification for glyphosate and AMPA are bellow 1ng/l. We analyzed two rain events at a high resolution for all stations and several events at the outlet of the catchment. We measured high glyphosate concentration in urban and agriculture dominated catchments with up to

  13. Architecture of fully occupied GluA2 AMPA receptor-TARP complex elucidated by cryo-EM.

    PubMed

    Zhao, Yan; Chen, Shanshuang; Yoshioka, Craig; Baconguis, Isabelle; Gouaux, Eric

    2016-08-04

    Fast excitatory neurotransmission in the mammalian central nervous system is largely carried out by AMPA-sensitive ionotropic glutamate receptors. Localized within the postsynaptic density of glutamatergic spines, AMPA receptors are composed of heterotetrameric receptor assemblies associated with auxiliary subunits, the most common of which are transmembrane AMPA receptor regulatory proteins (TARPs). The association of TARPs with AMPA receptors modulates receptor trafficking and the kinetics of receptor gating and pharmacology. Here we report the cryo-electron microscopy (cryo-EM) structure of the homomeric rat GluA2 AMPA receptor saturated with TARP γ2 subunits, which shows how the TARPs are arranged with four-fold symmetry around the ion channel domain and make extensive interactions with the M1, M2 and M4 transmembrane helices. Poised like partially opened ‘hands’ underneath the two-fold symmetric ligand-binding domain (LBD) 'clamshells', one pair of TARPs is juxtaposed near the LBD dimer interface, whereas the other pair is near the LBD dimer-dimer interface. The extracellular ‘domains’ of TARP are positioned to not only modulate LBD clamshell closure, but also affect conformational rearrangements of the LBD layer associated with receptor activation and desensitization, while the TARP transmembrane domains buttress the ion channel pore.

  14. Two families of TARP isoforms that have distinct effects on the kinetic properties of AMPA receptors and synaptic currents.

    PubMed

    Cho, Chang-Hoon; St-Gelais, Fannie; Zhang, Wei; Tomita, Susumu; Howe, James R

    2007-09-20

    Transmembrane AMPA receptor regulatory proteins (TARPs) are auxiliary AMPA receptor subunits that regulate both the trafficking and gating properties of AMPA receptors, and different TARP isoforms display distinct expression patterns in brain. Here, we compared the effects of four TARP isoforms on the kinetics of AMPA receptor currents. Each isoform slowed the deactivation of GluR1 currents, but the slowing was greatest with gamma-4 and gamma-8. Isoform-specific differences in desensitization were also observed that correlated with effects on deactivation. TARP isoforms also differentially modulated responses to trains of glutamate applications designed to mimic high-frequency presynaptic firing. Importantly, whereas both stargazin and gamma-4 rescued excitatory synaptic transmission in cerebellar granule cells from stargazer mice, the decay of miniature EPSCs was 2-fold slower in neurons expressing gamma-4. The results show that heterogeneity in the composition of AMPA receptor/TARP complexes contributes to synapse-specific differences in EPSC decays and frequency-dependent modulation of neurotransmission.

  15. Selective regulation of long-form calcium-permeable AMPA receptors by an atypical TARP, gamma-5.

    PubMed

    Soto, David; Coombs, Ian D; Renzi, Massimiliano; Zonouzi, Marzieh; Farrant, Mark; Cull-Candy, Stuart G

    2009-03-01

    Although the properties and trafficking of AMPA-type glutamate receptors (AMPARs) depend critically on associated transmembrane AMPAR regulatory proteins (TARPs) such as stargazin (gamma-2), no TARP has been described that can specifically regulate the important class of calcium-permeable (CP-) AMPARs. We examined the stargazin-related protein gamma-5, which is highly expressed in Bergmann glia, a cell type possessing only CP-AMPARs. gamma-5 was previously thought not to be a TARP, and it has been widely used as a negative control. Here we find that, contrary to expectation, gamma-5 acts as a TARP and serves this role in Bergmann glia. Whereas gamma-5 interacts with all AMPAR subunits, and modifies their behavior to varying extents, its main effect is to regulate the function of AMPAR subunit combinations that lack short-form subunits, which constitute predominantly CP-AMPARs. Our results suggest an important role for gamma-5 in regulating the functional contribution of CP-AMPARs.

  16. A single high dose of dexamethasone affects the phosphorylation state of glutamate AMPA receptors in the human limbic system

    PubMed Central

    Lopes, M W; Leal, R B; Guarnieri, R; Schwarzbold, M L; Hoeller, A; Diaz, A P; Boos, G L; Lin, K; Linhares, M N; Nunes, J C; Quevedo, J; Bortolotto, Z A; Markowitsch, H J; Lightman, S L; Walz, R

    2016-01-01

    Glucocorticoids (GC) released during stress response exert feedforward effects in the whole brain, but particularly in the limbic circuits that modulates cognition, emotion and behavior. GC are the most commonly prescribed anti-inflammatory and immunosuppressant medication worldwide and pharmacological GC treatment has been paralleled by the high incidence of acute and chronic neuropsychiatric side effects, which reinforces the brain sensitivity for GC. Synapses can be bi-directionally modifiable via potentiation (long-term potentiation, LTP) or depotentiation (long-term depression, LTD) of synaptic transmission efficacy, and the phosphorylation state of Ser831 and Ser845 sites, in the GluA1 subunit of the glutamate AMPA receptors, are a critical event for these synaptic neuroplasticity events. Through a quasi-randomized controlled study, we show that a single high dexamethasone dose significantly reduces in a dose-dependent manner the levels of GluA1-Ser831 phosphorylation in the amygdala resected during surgery for temporal lobe epilepsy. This is the first report demonstrating GC effects on key markers of synaptic neuroplasticity in the human limbic system. The results contribute to understanding how GC affects the human brain under physiologic and pharmacologic conditions. PMID:27959333

  17. Dopamine D4 receptors regulate AMPA receptor trafficking and glutamatergic transmission in GABAergic interneurons of prefrontal cortex.

    PubMed

    Yuen, Eunice Y; Yan, Zhen

    2009-01-14

    GABAergic interneurons in prefrontal cortex (PFC) play a critical role in cortical circuits by providing feedforward and feedback inhibition and synchronizing neuronal activity. Impairments in GABAergic inhibition to PFC pyramidal neurons have been implicated in the abnormal neural synchrony and working memory disturbances in schizophrenia. The dopamine D(4) receptor, which is strongly linked to neuropsychiatric disorders, such as attention deficit-hyperactivity disorder (ADHD) and schizophrenia, is highly expressed in PFC GABAergic interneurons, while the physiological role of D(4) in these interneurons is largely unknown. In this study, we found that D(4) activation caused a persistent suppression of AMPAR-mediated synaptic transmission in PFC interneurons. This effect of D(4) receptors on AMPAR-EPSC was via a mechanism dependent on actin/myosin V motor-based transport of AMPA receptors, which was regulated by cofilin, a major actin depolymerizing factor. Moreover, we demonstrated that the major cofilin-specific phosphatase Slingshot, which was activated by calcineurin downstream of D(4) signaling, was required for the D(4) regulation of glutamatergic transmission. Thus, D(4) receptors, by using the unique calcineurin/Slingshot/cofilin signaling mechanism, regulate actin dynamics and AMPAR trafficking in PFC GABAergic interneurons. It provides a potential mechanism for D(4) receptors to control the excitatory synaptic strength in local-circuit neurons and GABAergic inhibition in the PFC network, which may underlie the role of D(4) receptors in normal cognitive processes and mental disorders.

  18. Lack of NMDA-AMPA interaction in antidepressant-like effect of CGP 37849, an antagonist of NMDA receptor, in the forced swim test.

    PubMed

    Dybała, Małgorzata; Siwek, Agata; Poleszak, Ewa; Pilc, Andrzej; Nowak, Gabriel

    2008-11-01

    The NMDA receptor antagonist, CGP 37849-induced reduction in immobility time in the forced swim test in mice was not antagonized by pre-treatment with the AMPA receptor antagonist NBQX. This is the first demonstration of the antidepressant effect of the NMDA antagonist not being dependent on the AMPA transmission.

  19. Odor Preference Learning and Memory Modify GluA1 Phosphorylation and GluA1 Distribution in the Neonate Rat Olfactory Bulb: Testing the AMPA Receptor Hypothesis in an Appetitive Learning Model

    ERIC Educational Resources Information Center

    Cui, Wen; Darby-King, Andrea; Grimes, Matthew T.; Howland, John G.; Wang, Yu Tian; McLean, John H.; Harley, Carolyn W.

    2011-01-01

    An increase in synaptic AMPA receptors is hypothesized to mediate learning and memory. AMPA receptor increases have been reported in aversive learning models, although it is not clear if they are seen with memory maintenance. Here we examine AMPA receptor changes in a cAMP/PKA/CREB-dependent appetitive learning model: odor preference learning in…

  20. Sources of aminomethylphosphonic acid (AMPA) in urban and rural catchments in Ontario, Canada: Glyphosate or phosphonates in wastewater?

    PubMed

    Struger, J; Van Stempvoort, D R; Brown, S J

    2015-09-01

    Correlation analysis suggests that occurrences of AMPA in streams of southern Ontario are linked mainly to glyphosate in both urban and rural settings, rather than to wastewater sources, as some previous studies have suggested. For this analysis the artificial sweetener acesulfame was analyzed as a wastewater indicator in surface water samples collected from urban and rural settings in southern Ontario, Canada. This interpretation is supported by the concurrence of seasonal fluctuations of glyphosate and AMPA concentrations. Herbicide applications in larger urban centres and along major transportation corridors appear to be important sources of glyphosate and AMPA in surface water, in addition to uses of this herbicide in rural and mixed use areas. Fluctuations in concentrations of acesulfame and glyphosate residues were found to be related to hydrologic events.

  1. FUNCTIONAL ANALYSIS OF A NOVEL POSITIVE ALLOSTERIC MODULATOR OF AMPA RECEPTORS DERIVED FROM A STRUCTURE-BASED DRUG DESIGN STRATEGY

    PubMed Central

    Harms, Jonathan E.; Benveniste, Morris; Maclean, John K. F.; Partin, Kathryn M.; Jamieson, Craig

    2012-01-01

    Positive allosteric modulators of α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) receptors facilitate synaptic plasticity and can improve various forms of learning and memory. These modulators show promise as therapeutic agents for the treatment of neurological disorders such as schizophrenia, ADHD, and mental depression. Three classes of positive modulator, the benzamides, the thiadiazides, and the biarylsulfonamides differentially occupy a solvent accessible binding pocket at the interface between the two subunits that form the AMPA receptor ligand-binding pocket. Here, we describe the electrophysiological properties of a new chemotype derived from a structure-based drug design strategy (SBDD), which makes similar receptor interactions compared to previously reported classes of modulator. This pyrazole amide derivative, JAMI1001A, with a promising developability profile, efficaciously modulates AMPA receptor deactivation and desensitization of both flip and flop receptor isoforms. PMID:22735771

  2. AMPA receptor modulators have different impact on hippocampal pyramidal cells and interneurons.

    PubMed

    Xia, Y-F; Arai, A C

    2005-01-01

    Positive modulators of AMPA receptors enhance synaptic plasticity and memory encoding. Facilitation of AMPA receptor currents not only results in enhanced activation of excitatory neurons but also increases the activity of inhibitory interneurons by up-modulating their excitatory input. However, little is known about the effects of these modulators on cells other than pyramidal neurons and about their impact on local microcircuits. This study examined the effects of members from three subfamilies of modulators (mainly CX516, CX546 and cyclothiazide) on excitatory synaptic responses in four classes of hippocampal CA1 neurons and on excitatory and disynaptically induced inhibitory field potentials in hippocampal slices. Effects on excitatory postsynaptic currents (EPSCs) were examined in pyramidal cells, in two types of inhibitory interneurons located in stratum radiatum and oriens, and in stratum radiatum giant cells, a novel type of excitatory neuron. With CX516, increases in EPSC amplitude in pyramidal cells were two to three times larger than in interneurons and six times larger than in radiatum giant cells. The effects of CX546 on response duration similarly were largest in pyramidal cells. However, this drug also strongly differentiated between stratum oriens and radiatum interneurons with increases being four times larger in the latter. In contrast, cyclothiazide had similar effects on response duration in all cell types. In field recordings, CX516 was several times more potent in enhancing excitatory postsynaptic potentials (EPSPs) than feedback or feedforward circuits, as expected from its larger influence on pyramidal cells. In contrast, BDP-20, a CX546 analog, was more potent in enhancing feedforward inhibition than either EPSPs or feedback inhibition. This preference for feedforward over feedback circuits is probably related to its higher potency in stratum radiatum versus oriens interneurons. Taken together, AMPA receptor modulators differ substantially

  3. Depth distribution of glyphosate and AMPA under diferent tillage system and soils in long-term experiments

    NASA Astrophysics Data System (ADS)

    Aparicio, Virginia; Costa, Jose Luis; De Geronimo, Eduardo

    2016-04-01

    Glyphosate (N-(phosphonomethyl glycine) is a post-emergence, non-selective, foliar herbicide. Around 200 million liters of this herbicide are applied every year in Argentina, where the main agricultural practice is no-till (NT), accounting for 78 % of the cultivated land. In this work, we studied the depth distribution of glyphosate in long-term experiments (more than 15 years) at different locations under NT and conventional tillage (CT). Samples from 0-2, 2-5, 5-10, 10-15, and 15-20 cm depth with four replication and two treatments NT CT at three locations: Balcarce (BA) a loam soil, Bordenave (BO) a sandy loam soil y Marcos Juarez a silty loam soil (MJ). The glyphosate concentration in the first 2 cm of soil was, on the average, 70% greater than in the next 2-5 cm. The mass of glyphosate in CT was higher at 2 to 10 cm depth. The depth concentration of AMPA follows the same trend than glyphosate, although its average concentration at 0-2 cm depth is 28 times higher than the glyphosate concentration at 2-5 cm (glyphosate = 147 ppb and AMPA = 4100 ppb). Beside the AMPA concentration at 0-2 cm depth is greater in NT than in CT, the mass of AMPA is higher in CT only for the Balcarce location. To our knowledge, this study is the first dealing with the depth distribution of glyphosate concentration in soils under different soil managements. In the present study, it was demonstrated that glyphosate and AMPA are present in soils under agricultural activity with maximum concentration in the first two cm of soil and the AMPA concentration at this depth is greater in NT than in CT.

  4. Restoring Light Sensitivity in Blind Retinae Using a Photochromic AMPA Receptor Agonist.

    PubMed

    Laprell, L; Hüll, K; Stawski, P; Schön, C; Michalakis, S; Biel, M; Sumser, M P; Trauner, D

    2016-01-20

    Retinal degenerative diseases can have many possible causes and are currently difficult to treat. As an alternative to therapies that require genetic manipulation or the implantation of electronic devices, photopharmacology has emerged as a viable approach to restore visual responses. Here, we present a new photopharmacological strategy that relies on a photoswitchable excitatory amino acid, ATA. This freely diffusible molecule selectively activates AMPA receptors in a light-dependent fashion. It primarily acts on amacrine and retinal ganglion cells, although a minor effect on bipolar cells has been observed. As such, it complements previous pharmacological approaches based on photochromic channel blockers and increases the potential of photopharmacology in vision restoration.

  5. An AMPA receptor potentiator modulates hippocampal expression of BDNF: an in vivo study.

    PubMed

    Mackowiak, Marzena; O'Neill, Michael J; Hicks, Caroline A; Bleakman, David; Skolnick, Phil

    2002-07-01

    AMPA receptor activation has been demonstrated to increase the neuronal expression of brain derived neurotrophic factor (BDNF). In the present study, we investigated the effect of a novel AMPA receptor potentiator (LY404187) and its active isomer (LY451646) on the expression of BDNF protein and mRNA, as well as TrkB mRNA in rat hippocampus. LY404187 administered for 7 days (1 mg/kg) significantly increased the number of BDNF immunopositive cells in the dentate gyrus, but not other hippocampal subfields. Chronic treatment (7 days) with LY451646 (0.5 mg/kg, comparable to 1 mg/kg of LY404187) increased the level of both BDNF and TrkB mRNA expression in the dentate gyrus, CA3 and CA4 of the hippocampus. However, chronic treatment with lower doses of LY451646 (0.125 and 0.25 mg/kg) decreased the level of BDNF and TrkB mRNA in hippocampus, whilst the highest used dose of LY451646 (1 mg/kg) had no effect on BDNF and TrkB mRNA in hippocampus. In contrast, acute treatment with LY451646 produced an increase in BDNF mRNA levels at doses of 0.125 and 0.25 mg/kg in the hippocampus (CA4, CA3 and dentate gyrus, but not in CA1). LY451646 at 0.5 mg/kg had no effect, but at 1.0 mg/kg decreased the level of BDNF mRNA in hippocampus. Acute treatment with LY451646 did not affect the TrkB receptor mRNA levels in hippocampus. Our results demonstrate that biarylpropylsulfonamide AMPA receptor potentiators are capable of modulating the expression of BDNF and TrkB mRNA in a dose- and time-dependent manner. The increase in both BDNF protein and mRNA expression in the dentate gyrus but not in CA1 indicates a specific role of AMPA receptors in the regulation of BDNF expression in this hippocampal subfield. The regulation of BDNF expression by biarylpropylsulfonamids such as LY451646 may have important therapeutical implications for this class of molecule in the treatment of depression and other CNS disorders.

  6. Blocking GABA(A) inhibition reveals AMPA- and NMDA-receptor-mediated polysynaptic responses in the CA1 region of the rat hippocampus.

    PubMed

    Crépel, V; Khazipov, R; Ben-Ari, Y

    1997-04-01

    We have investigated the conditions required to evoke polysynaptic responses in the isolated CA1 region of hippocampal slices from Wistar adult rats. Experiments were performed with extracellular and whole cell recording techniques. In the presence of bicuculline (10 microM), 6-cyano-7-nitroquinoxaline-2-3-dione (10 microM), glycine (10 microM), and a low external concentration of Mg2+ (0.3 mM), electrical stimulation of the Schaffer collaterals/commissural pathway evoked graded N-methyl-D-aspartate (NMDA)-receptor-mediated late field potentials in the stratum radiatum of the CA1 region. These responses were generated via polysynaptic connections because their latency varied strongly and inversely with the stimulation intensity and they were abolished by a high concentration of divalent cations (7 mM Ca2+). These responses likely were driven by local collateral branches of CA1 pyramidal cell axons because focal application of tetrodotoxin (30 microM) in the stratum oriens strongly reduced the late synaptic component and antidromic stimulation of CA1 pyramidal cells could evoke the polysynaptic response. Current-source density analysis suggested that the polysynaptic response was generated along the proximal part of the apical dendrites of CA1 pyramidal cells (50-150 microm below the pyramidal cell layer in the stratum radiatum). In physiological concentration of Mg2+ (1.3 mM), the pharmacologically isolated NMDA-receptor-mediated polysynaptic response was abolished. In control artificial cerebrospinal fluid (with physiological concentration of Mg2+), bicuculline ( 10 microM) generated a graded polysynaptic response. Under these conditions, this response was mediated both by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/NMDA receptors. In the presence of D-2-amino-5-phosphonovalerate (50 microM), the polysynaptic response could be mediated by AMPA receptors, although less efficiently. In conclusion, suppression of gamma-aminobutyric acid

  7. Episodic sucrose intake during food restriction increases synaptic abundance of AMPA receptors in nucleus accumbens and augments intake of sucrose following restoration of ad libitum feeding.

    PubMed

    Peng, X-X; Lister, A; Rabinowitsch, A; Kolaric, R; Cabeza de Vaca, S; Ziff, E B; Carr, K D

    2015-06-04

    Weight-loss dieting often leads to loss of control, rebound weight gain, and is a risk factor for binge pathology. Based on findings that food restriction (FR) upregulates sucrose-induced trafficking of glutamatergic AMPA receptors to the nucleus accumbens (NAc) postsynaptic density (PSD), this study was an initial test of the hypothesis that episodic "breakthrough" intake of forbidden food during dieting interacts with upregulated mechanisms of synaptic plasticity to increase reward-driven feeding. Ad libitum (AL) fed and FR subjects consumed a limited amount of 10% sucrose, or had access to water, every other day for 10 occasions. Beginning three weeks after return of FR rats to AL feeding, when 24-h chow intake and rate of body weight gain had normalized, subjects with a history of sucrose intake during FR consumed more sucrose during a four week intermittent access protocol than the two AL groups and the group that had access to water during FR. In an experiment that substituted noncontingent administration of d-amphetamine for sucrose, FR subjects displayed an enhanced locomotor response during active FR but a blunted response, relative to AL subjects, during recovery from FR. This result suggests that the enduring increase in sucrose consumption is unlikely to be explained by residual enhancing effects of FR on dopamine signaling. In a biochemical experiment which paralleled the sucrose behavioral experiment, rats with a history of sucrose intake during FR displayed increased abundance of pSer845-GluA1, GluA2, and GluA3 in the NAc PSD relative to rats with a history of FR without sucrose access and rats that had been AL throughout, whether they had a history of episodic sucrose intake or not. A history of FR, with or without a history of sucrose intake, was associated with increased abundance of GluA1. A terminal 15-min bout of sucrose intake produced a further increase in pSer845-GluA1 and GluA2 in subjects with a history of sucrose intake during FR

  8. Sleep-Dependent Declarative Memory Consolidation—Unaffected after Blocking NMDA or AMPA Receptors but Enhanced by NMDA Coagonist D-Cycloserine

    PubMed Central

    Feld, Gordon B; Lange, Tanja; Gais, Steffen; Born, Jan

    2013-01-01

    Sleep has a pivotal role in the consolidation of declarative memory. The coordinated neuronal replay of information encoded before sleep has been identified as a key process. It is assumed that the repeated reactivation of firing patterns in glutamatergic neuron assemblies translates into plastic synaptic changes underlying the formation of longer-term neuronal representations. Here, we tested the effects of blocking and enhancing glutamatergic neurotransmission during sleep on declarative memory consolidation in humans. We conducted three placebo-controlled, crossover, double-blind studies in which participants learned a word-pair association task. Afterwards, they slept in a sleep laboratory and received glutamatergic modulators. Our first two studies aimed at impairing consolidation by administering the NMDA receptor blocker ketamine and the AMPA receptor blocker caroverine during retention sleep, which, paradoxically, remained unsuccessful, inasmuch as declarative memory performance was unaffected by the treatment. However, in the third study, administration of the NMDA receptor coagonist D-cycloserine (DCS) during retention sleep facilitated consolidation of declarative memory (word pairs) but not consolidation of a procedural control task (finger sequence tapping). Administration of DCS during a wake interval remained without effect on retention of word pairs but improved encoding of numbers. From the overall pattern, we conclude that the consolidation of hippocampus-dependent declarative memory during sleep relies on NMDA-related plastic processes that differ from those processes leading to wake encoding. We speculate that glutamatergic activation during sleep is not only involved in consolidation but also in forgetting of hippocampal memory with both processes being differentially sensitive to DCS and unselective blockade of NMDA and AMPA receptors. PMID:23887151

  9. ATP P2X receptors downregulate AMPA receptor trafficking and postsynaptic efficacy in hippocampal neurons.

    PubMed

    Pougnet, Johan-Till; Toulme, Estelle; Martinez, Audrey; Choquet, Daniel; Hosy, Eric; Boué-Grabot, Eric

    2014-07-16

    P2X receptors (P2XRs) are ATP-gated cation channels widely expressed in the brain where they mediate action of extracellular ATP released by neurons or glia. Although purinergic signaling has multiple effects on synaptic transmission and plasticity, P2XR function at brain synapses remains to be established. Here, we show that activation of postsynaptic P2XRs by exogenous ATP or noradrenaline-dependent glial release of endogenous ATP decreases the amplitude of miniature excitatory postsynaptic currents and AMPA-evoked currents in cultured hippocampal neurons. We also observed a P2X-mediated depression of field potentials recorded in CA1 region from brain slices. P2X2Rs trigger dynamin-dependent internalization of AMPA receptors (AMPARs), leading to reduced surface AMPARs in dendrites and at synapses. AMPAR alteration required calcium influx through opened ATP-gated channels and phosphatase or CamKII activities. These findings indicate that postsynaptic P2XRs play a critical role in regulating the surface expression of AMPARs and thereby regulate the synaptic strength.

  10. AMPA receptor mediated D-serine release from retinal glial cells

    PubMed Central

    Sullivan, Steve J.; Miller, Robert F.

    2010-01-01

    The NMDA receptor coagonist D-serine is important in a number of different processes in the central nervous system, ranging from synaptic plasticity to disease states, including schizophrenia. D-serine appears to be the major coagonist acting on retinal ganglion cell NMDA receptors, but the cell type from which it originates and whether its release can be modulated by activity are unknown. In this study, we utilized a mutant mouse line with elevated D-serine to investigate this question. Direct measurements of extracellular D-serine using capillary electrophoresis demonstrate that D-serine can be released from the intact mouse retina through an AMPA receptor dependent mechanism. AMPA-evoked D-serine release persisted in the presence of a cocktail of neural inhibitors but was abolished after administration of a glial toxin. These findings provide the first evidence that extracellular D-serine levels in the retina can be modulated, and that such modulation is contingent upon glial cell activity. PMID:20969576

  11. Evidence for loss of synaptic AMPA receptors in anterior piriform cortex of aged mice.

    PubMed

    Gocel, James; Larson, John

    2013-01-01

    It has been suggested that age-related impairments in learning and memory may be due to age-related deficits in long-term potentiation of glutamatergic synaptic transmission. For example, olfactory discrimination learning is significantly affected by aging in mice and this may be due, in part, to diminished synaptic plasticity in piriform cortex. In the present study, we tested for alterations in electrophysiological properties and synaptic transmission in this simple cortical network. Whole-cell recordings were made from principal neurons in slices of anterior piriform cortex from young (3-6 months old) and old (24-28 months) C57Bl/6 mice. Miniature excitatory postsynaptic currents (mEPSCs) mediated by AMPA receptors were collected from cells in presence of tetrodotoxin (TTX) and held at -80 mV in voltage-clamp. Amplitudes of mEPSCs were significantly reduced in aged mice, suggesting that synaptic AMPA receptor expression is decreased during aging. In a second set of experiments, spontaneous excitatory postsynaptic currents (s/mEPSCs) were recorded in slices from different cohorts of young and old mice, in the absence of TTX. These currents resembled mEPSCs and were similarly reduced in amplitude in old mice. The results represent the first electrophysiological evidence for age-related declines in glutamatergic synaptic function in the mammalian olfactory system.

  12. BMAA selectively injures motor neurons via AMPA/kainate receptor activation.

    PubMed

    Rao, Shyam D; Banack, Sandra Anne; Cox, Paul Alan; Weiss, John H

    2006-09-01

    The toxin beta-methylamino-l-alanine (BMAA) has been proposed to contribute to amyotrophic lateral sclerosis-Parkinsonism Dementia Complex of Guam (ALS/PDC) based on its ability to induce a similar disease phenotype in primates and its presence in cycad seeds, which constituted a dietary item in afflicted populations. Concerns about the apparent low potency of this toxin in relation to estimated levels of human ingestion led to a slowing of BMAA research. However, recent reports identifying potential new routes of exposure compel a re-examination of the BMAA/cycad hypothesis. BMAA was found to induce selective motor neuron (MN) loss in dissociated mixed spinal cord cultures at concentrations ( approximately 30 muM) significantly lower than those previously found to induce widespread neuronal degeneration. The glutamate receptor antagonist NBQX prevented BMAA-induced death, implicating excitotoxic activation of AMPA/kainate receptors. Using microfluorimetric techniques, we further found that BMAA induced preferential [Ca(2+)](i) rises and selective reactive oxygen species (ROS) generation in MNs with minimal effect on other spinal neurons. Cycad seed extracts also triggered preferential AMPA/kainate-receptor-dependent MN injury, consistent with the idea that BMAA is a crucial toxic component in this plant. Present findings support the hypothesis that BMAA may contribute to the selective MN loss in ALS/PDC.

  13. Accumbens shell AMPA receptors mediate expression of extinguished reward seeking through interactions with basolateral amygdala.

    PubMed

    Millan, E Zayra; McNally, Gavan P

    2011-07-01

    Extinction is the reduction in drug seeking when the contingency between drug seeking behavior and the delivery of drug reward is broken. Here, we investigated a role for the nucleus accumbens shell (AcbSh). Rats were trained to respond for 4% (v/v) alcoholic beer in one context (Context A) followed by extinction in a second context (Context B). Rats were subsequently tested in the training context, A (ABA), or the extinction context, B (ABB). Pre-test injections of the glutamate AMPA receptor antagonist, NBQX (1 µg) into AcbSh had no effect on renewal of alcoholic beer seeking when rats were returned to the training context (ABA). However, NBQX increased responding when rats were tested in the extinction context (ABB). In a second experiment, rats received training, extinction, and test in the same context. Pre-test injections of NBQX (0, 0.3, and 1 µg) into the AcbSh dose-dependently attenuated expression of extinction. We also found that NBQX in the AcbSh had no effect on initial acquisition of extinction or the motivation to respond for reward as measured by break point on a progressive ratio schedule. Finally, we show that pharmacological disconnection of a basolateral amygdala (BLA) → AcbSh pathway via NBQX in AcbSh combined with reversible inactivation of the contralateral BLA attenuates expression of extinction. Together, these results suggest that AcbSh AMPA receptors mediate expression of extinguished reward seeking through glutamatergic inputs from the BLA.

  14. Effects of positive AMPA receptor modulators on calpain-mediated spectrin degradation in cultured hippocampal slices.

    PubMed

    Jourdi, Hussam; Yanagihara, Ted; Martinez, Ulises; Bi, Xiaoning; Lynch, Gary; Baudry, Michel

    2005-01-01

    Positive modulators of AMPA receptors (AMPAr), also known as ampakines, are allosteric effectors of the receptors and have been extensively studied in past years due to their potential use as treatment for various diseases and ailments of the central nervous system such as mild cognitive impairment, schizophrenia, and Alzheimer's disease. Ampakines have been shown to improve performance on memory tasks in animals and in human subjects, an effect linked to their ability to increase agonist-mediated ion influx through AMPAr, thus leading to enhanced synaptic responses and facilitation of long-term potentiation (LTP) induction at glutamatergic synapses. As LTP is associated with calpain activation and spectrin degradation, we determined the effects of ampakine treatment of cultured hippocampal slices on spectrin degradation. Calpain activation was evaluated by determining the levels of the 145-150kDa degradation products of spectrin. Our data indicated that incubation of hippocampal slices with some, but not all positive modulators of AMPA receptors resulted in enhanced spectrin degradation, an effect that was blocked by a calpain inhibitor. In addition, an antagonist of AMPAr but not of NMDAr blocked ampakine-induced spectrin degradation. These results indicate that prolonged treatment with selected ampakines leads to spectrin degradation mediated by activation of the calcium-dependent protease calpain.

  15. Post-anesthesia AMPA receptor potentiation prevents anesthesia-induced learning and synaptic deficits

    PubMed Central

    Huang, Lianyan; Cichon, Joseph; Ninan, Ipe; Yang, Guang

    2016-01-01

    Accumulating evidence has shown that repeated exposure to general anesthesia during critical stages of brain development results in long-lasting behavioral deficits later in life. To date, there has been no effective treatment to mitigate the neurotoxic effects of anesthesia on brain development. By performing calcium imaging in the mouse motor cortex, we show that ketamine anesthesia causes a marked and prolonged reduction in neuronal activity during the period of post-anesthesia recovery. Administration of the AMPAkine drug CX546 [1-(1,4-benzodioxan-6-ylcarbonyl)piperidine] to potentiate AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor activity during emergence from anesthesia in mice enhances neuronal activity and prevents long-term motor learning deficits induced by repeated neonatal anesthesia. In addition, we show that CX546 administration also ameliorates various synaptic deficits induced by anesthesia, including reductions in synaptic expression of NMDA (N-methyl-D-aspartate) and AMPA receptor subunits, motor training-evoked neuronal activity, and dendritic spine remodeling associated with motor learning. Together, our results indicate that pharmacologically enhancing neuronal activity during the post-anesthesia recovery period could effectively reduce the adverse effects of early-life anesthesia. PMID:27334260

  16. Basal Levels of AMPA Receptor GluA1 Subunit Phosphorylation at Threonine 840 and Serine 845 in Hippocampal Neurons

    ERIC Educational Resources Information Center

    Babiec, Walter E.; Guglietta, Ryan; O'Dell, Thomas J.

    2016-01-01

    Dephosphorylation of AMPA receptor (AMPAR) GluA1 subunits at two sites, serine 845 (S845) and threonine 840 (T840), is thought to be involved in NMDA receptor-dependent forms of long-term depression (LTD). Importantly, the notion that dephosphorylation of these sites contributes to LTD assumes that a significant fraction of GluA1 subunits are…

  17. Glycine Potentiates AMPA Receptor Function through Metabotropic Activation of GluN2A-Containing NMDA Receptors

    PubMed Central

    Li, Li-Jun; Hu, Rong; Lujan, Brendan; Chen, Juan; Zhang, Jian-Jian; Nakano, Yasuko; Cui, Tian-Yuan; Liao, Ming-Xia; Chen, Jin-Cao; Man, Heng-Ye; Feng, Hua; Wan, Qi

    2016-01-01

    NMDA receptors are Ca2+-permeable ion channels. The activation of NMDA receptors requires agonist glutamate and co-agonist glycine. Recent evidence indicates that NMDA receptor also has metabotropic function. Here we report that in cultured mouse hippocampal neurons, glycine increases AMPA receptor-mediated currents independent of the channel activity of NMDA receptors and the activation of glycine receptors. The potentiation of AMPA receptor function by glycine is antagonized by the inhibition of ERK1/2. In the hippocampal neurons and in the HEK293 cells transfected with different combinations of NMDA receptors, glycine preferentially acts on GluN2A-containing NMDA receptors (GluN2ARs), but not GluN2B-containing NMDA receptors (GluN2BRs), to enhance ERK1/2 phosphorylation independent of the channel activity of GluN2ARs. Without requiring the channel activity of GluN2ARs, glycine increases AMPA receptor-mediated currents through GluN2ARs. Thus, these results reveal a metabotropic function of GluN2ARs in mediating glycine-induced potentiation of AMPA receptor function via ERK1/2 activation. PMID:27807405

  18. GluN2B-Containing NMDA Receptors Regulate AMPA Receptor Traffic through Anchoring of the Synaptic Proteasome.

    PubMed

    Ferreira, Joana S; Schmidt, Jeannette; Rio, Pedro; Águas, Rodolfo; Rooyakkers, Amanda; Li, Ka Wan; Smit, August B; Craig, Ann Marie; Carvalho, Ana Luisa

    2015-06-03

    NMDA receptors play a central role in shaping the strength of synaptic connections throughout development and in mediating synaptic plasticity mechanisms that underlie some forms of learning and memory formation in the CNS. In the hippocampus and the neocortex, GluN1 is combined primarily with GluN2A and GluN2B, which are differentially expressed during development and confer distinct molecular and physiological properties to NMDA receptors. The contribution of each subunit to the synaptic traffic of NMDA receptors and therefore to their role during development and in synaptic plasticity is still controversial. We report a critical role for the GluN2B subunit in regulating NMDA receptor synaptic targeting. In the absence of GluN2B, the synaptic levels of AMPA receptors are increased and accompanied by decreased constitutive endocytosis of GluA1-AMPA receptor. We used quantitative proteomic analysis to identify changes in the composition of postsynaptic densities from GluN2B(-/-) mouse primary neuronal cultures and found altered levels of several ubiquitin proteasome system components, in particular decreased levels of proteasome subunits. Enhancing the proteasome activity with a novel proteasome activator restored the synaptic levels of AMPA receptors in GluN2B(-/-) neurons and their endocytosis, revealing that GluN2B-mediated anchoring of the synaptic proteasome is responsible for fine tuning AMPA receptor synaptic levels under basal conditions.

  19. Modelling fate and transport of glyphosate and AMPA in the Meuse catchment to assess the contribution of different pollution sources

    NASA Astrophysics Data System (ADS)

    Desmet, Nele; Seuntjens, Piet

    2013-04-01

    Large river basins have multiple sources of pesticides and usually the pollution sources are spread over the entire catchment. The cumulative effect of pesticides entering the river system in upstream areas and the formation of persistent degradation products can compromise downstream water use e.g. raw water quality for drinking water abstractions. For assessments at catchment scale pesticide fluxes coming from different sources and sub basins need to be taken into account. To improve management strategies, a sound understanding of the sources, emission routes, transport, environmental fate and conversion of pesticides is needed. In the Netherlands, the Meuse river basin is an important source for drinking water production. The river suffers from elevated concentrations of glyphosate and aminomethylphosphonic acid (AMPA). For AMPA it is rather unclear to what extent the pollution is related to glyphosate degradation and what is the contribution of other sources, especial phosphonates in domestic and industrial waste water. Based on the available monitoring data only it is difficult to distinguish between AMPA sources in such a large river basin. This hampers interpretation and decision making for water quality management in the Meuse catchment. Here, application of water quality models is very useful to obtain complementary information and insights. Modelling allows accounting for temporal and spatial variability in discharge and concentrations as well as distinguishing the contribution from conversion processes. In this study, a model for the river Meuse was developed and applied to assess the contribution of tributary and transnational influxes, glyphosate degradation and other sources to the AMPA pollution.

  20. Identification of an ionotropic glutamate receptor AMPA1/GRIA1 polymorphism in crossbred beef cows differing in fertility

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A proposed functional polymorphism in the ionotropic glutamate receptor AMPA1 (GRIA1) has been reported to influence antral follicle numbers and fertility in cows. Repeat Breeder cows that fail to produce a calf in multiple seasons have been reported to have reduced numbers of small (1-3 mm) antral ...

  1. Glyphosate-resistant and conventional canola (Brassica napus L.) responses to glyphosate and Aminomethylphosphonic Acid (AMPA) treatment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glyphosate-resistant (GR) canola expresses two transgenes: 1) the microbial glyphosate oxidase gene (gox) encoding the glyphosate oxidase enzyme (GOX) that metabolizes glyphosate to aminomethylphosphonic acid (AMPA) and 2) cp4 that encodes a GR form of the glyphosate target enzyme 5-enolpyruvylshiki...

  2. Deletion of the GluA1 AMPA Receptor Subunit Alters the Expression of Short-Term Memory

    ERIC Educational Resources Information Center

    Sanderson, David J.; Sprengel, Rolf; Seeburg, Peter H.; Bannerman, David M.

    2011-01-01

    Deletion of the GluA1 AMPA receptor subunit selectively impairs short-term memory for spatial locations. We further investigated this deficit by examining memory for discrete nonspatial visual stimuli in an operant chamber. Unconditioned suppression of magazine responding to visual stimuli was measured in wild-type and GluA1 knockout mice.…

  3. Ampakine CX516 ameliorates functional deficits in AMPA receptors in a hippocampal slice model of protein accumulation.

    PubMed

    Kanju, Patrick M; Parameshwaran, Kodeeswaran; Sims, Catrina; Bahr, Ben A; Shonesy, Brian C; Suppiramaniam, Vishnu

    2008-11-01

    AMPAkines are positive modulators of AMPA receptors, and previous work has shown that these compounds can facilitate synaptic plasticity and improve learning and memory in both animals and humans; thus, their role in the treatment of cognitive impairment is worthy of investigation. In this study, we have utilized an organotypic slice model in which chloroquine-induced lysosomal dysfunction produces many of the pathogenic attributes of Alzheimer's disease. Our previous work demonstrated that synaptic AMPA receptor function is impaired in hippocampal slice cultures exhibiting lysosomal dysfunction leading to protein accumulation. The present study investigated the effect of the AMPAkine CX516 on AMPAR-mediated synaptic transmission as well as the CX516 induced modification of single channel AMPA receptor properties in this organotypic slice-culture model. In whole cell recordings from CA1 pyramidal neurons in chloroquine-treated slices we observed a significant decrease in AMPAR-mediated mEPSC frequency and amplitude indicating synaptic dysfunction. Following application of CX516, these parameters returned to nearly normal levels. Similarly, we report chloroquine-induced impairment of AMPAR single channel properties (decreased probability of opening and mean open time), and significant recovery of these properties following CX516 administration. These results suggest that AMPA receptors may be potential pharmaceutical targets for the treatment of neurodegenerative diseases, and highlights AMPAkines, in particular, as possible therapeutic agents.

  4. BDNF and AMPA receptors in the cNTS modulate the hyperglycemic reflex after local carotid body NaCN stimulation.

    PubMed

    Cuéllar, R; Montero, S; Luquín, S; García-Estrada, J; Melnikov, V; Virgen-Ortiz, A; Lemus, M; Pineda-Lemus, M; de Álvarez-Buylla, E

    2017-02-03

    The application of sodium cyanide (NaCN) to the carotid body receptors (CBR) (CBR stimulation) induces rapid blood hyperglycemia and an increase in brain glucose retention. The commissural nucleus tractus solitarius (cNTS) is an essential relay nucleus in this hyperglycemic reflex; it receives glutamatergic afferents (that also release brain derived neurotrophic factor, BDNF) from the nodose-petrosal ganglia that relays CBR information. Previous work showed that AMPA in NTS blocks hyperglycemia and brain glucose retention after CBR stimulation. In contrast, BDNF, which attenuates glutamatergic AMPA currents in NTS, enhances these glycemic responses. Here we investigated the combined effects of BDNF and AMPA (and their antagonists) in NTS on the glycemic responses to CBR stimulation. Microinjections of BDNF plus AMPA into the cNTS before CBR stimulation in anesthetized rats, induced blood hyperglycemia and an increase in brain arteriovenous (a-v) of blood glucose concentration difference, which we infer is due to increased brain glucose retention. By contrast, the microinjection of the TrkB antagonist K252a plus AMPA abolished the glycemic responses to CBR stimulation similar to what is observed after AMPA pretreatments. In BDNF plus AMPA microinjections preceding CBR stimulation, the number of c-fos immunoreactive cNTS neurons increased. In contrast, in the rats microinjected with K252a plus AMPA in NTS, before CBR stimulation, c-fos expression in cNTS decreased. The expression of AMPA receptors GluR2/3 did not change in any of the studied groups. These results indicate that BDNF in cNTS plays a key role in the modulation of the hyperglycemic reflex initiated by CBR stimulation.

  5. Zebrafish TARP Cacng2 is required for the expression and normal development of AMPA receptors at excitatory synapses.

    PubMed

    Roy, Birbickram; Ahmed, Kazi T; Cunningham, Marcus E; Ferdous, Jannatul; Mukherjee, Rajarshi; Zheng, Wang; Chen, Xing-Zhen; Ali, Declan W

    2016-05-01

    Fast excitatory synaptic transmission in the CNS is mediated by the neurotransmitter glutamate, binding to and activating AMPA receptors (AMPARs). AMPARs are known to interact with auxiliary proteins that modulate their behavior. One such family of proteins is the transmembrane AMPA receptor-related proteins, known as TARPs. Little is known about the role of TARPs during development, or about their function in non-mammalian organisms. Here we report the presence of TARPs, specifically the prototypical TARP, stargazin, in developing zebrafish. We find that zebrafish express two forms of stargazin, Cacng2a and Cacng2b from as early as 12-h post fertilization (hpf). Knockdown of Cacng2a and Cacng2b via splice-blocking morpholinos resulted in embryos that exhibited deficits in C-start escape responses, showing reduced C-bend angles, smaller tail velocities and aberrant C-bend turning directions. Injection of the morphants with Cacng2a or 2b mRNA rescued the morphological phenotype and the synaptic deficits. To investigate the effect of reduced Cacng2a and 2b levels on synaptic physiology, we performed whole cell patch clamp recordings of AMPA mEPSCs from zebrafish Mauthner cells. Knockdown of Cacng2a results in reduced AMPA currents and lower mEPSC frequencies, whereas knockdown of Cacng2b displayed no significant change in mEPSC amplitude or frequency. Non-stationary fluctuation analysis confirmed a reduction in the number of active synaptic receptors in the Cacng2a but not in the Cacng2b morphants. Together, these results suggest that Cacng2a is required for normal trafficking and function of synaptic AMPARs, while Cacng2b is largely non-functional with respect to the development of AMPA synaptic transmission.

  6. AMPA/kainate glutamate receptors contribute to inflammation, degeneration and pain related behaviour in inflammatory stages of arthritis

    PubMed Central

    Bonnet, Cleo S; Williams, Anwen S; Gilbert, Sophie J; Harvey, Ann K; Evans, Bronwen A; Mason, Deborah J

    2015-01-01

    Objectives Synovial fluid glutamate concentrations increase in arthritis. Activation of kainate (KA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors (GluRs) increase interleukin-6 (IL-6) release and cause arthritic pain, respectively. We hypothesised that AMPA and KA GluRs are expressed in human arthritis, and that intra-articular NBQX (AMPA/KA GluR antagonist) prevents pain and pathology in antigen-induced arthritis (AIA). Methods GluR immunohistochemistry was related to synovial inflammation and degradation in osteoarthritis (OA) and rheumatoid arthritis (RA). A single intra-articular NBQX injection was given at induction, and knee swelling and gait of AIA and AIA+NBQX rats compared over 21 days, before imaging, RT-qPCR, histology and immunohistochemistry of joints. Effects of NBQX on human primary osteoblast (HOB) activity were determined. Results AMPAR2 and KA1 immunolocalised to remodelling bone, cartilage and synovial cells in human OA and RA, and rat AIA. All arthritic tissues showed degradation and synovial inflammation. NBQX reduced GluR abundance, knee swelling (p<0.001, days 1–21), gait abnormalities (days 1–2), end-stage joint destruction (p<0.001), synovial inflammation (p<0.001), and messenger RNA expression of meniscal IL-6 (p<0.05) and whole joint cathepsin K (p<0.01). X-ray and MRI revealed fewer cartilage and bone erosions, and less inflammation after NBQX treatment. NBQX reduced HOB number and prevented mineralisation. Conclusions AMPA/KA GluRs are expressed in human OA and RA, and in AIA, where a single intra-articular injection of NBQX reduced swelling by 33%, and inflammation and degeneration scores by 34% and 27%, respectively, exceeding the efficacy of approved drugs in the same model. AMPA/KA GluR antagonists represent a potential treatment for arthritis. PMID:24130267

  7. Concomitant manipulation of murine NMDA- and AMPA-receptors to produce pro-cognitive drug effects in mice.

    PubMed

    Vignisse, Julie; Steinbusch, Harry W M; Grigoriev, Vladimir; Bolkunov, Alexei; Proshin, Alexey; Bettendorff, Lucien; Bachurin, Sergey; Strekalova, Tatyana

    2014-02-01

    Bifunctional drug therapy targeting distinct receptor signalling systems can generate increased efficacy at lower concentrations compared to monofunctional therapy. Non-competitive blockade of the NMDA receptors or the potentiation of AMPA receptors is well documented to result in memory enhancement. Here, we compared the efficacy of the low-affinity NMDA receptor blocker memantine or the positive modulator of AMPA receptor QXX (in C57BL/6J at 1 or 5mg/kg, ip) with new derivatives of isothiourea (0.5-1 mg/kg, ip) that have bifunctional efficacy. Low-affinity NMDA blockade by these derivatives was achieved by introducing greater flexibility into the molecule, and AMPA receptor stimulation was produced by a sulfamide-containing derivative of isothiourea. Contextual learning was examined in a step-down avoidance task and extinction of contextual memory was studied in a fear-conditioning paradigm. Memantine enhanced contextual learning while QXX facilitated memory extinction; both drugs were effective at 5 mg/kg. The new derivative IPAC-5 elevated memory scores in both tasks at the dose 0.5 mg/kg and exhibited the lowest IC₅₀ values of NMDA receptor blockade and highest potency of AMPA receptor stimulation. Thus, among the new drugs tested, IPAC-5 replicated the properties of memantine and QXX in one administration with increased potency. Our data suggest that a concomitant manipulation of NMDA- and AMPA-receptors results in pro-cognitive effects and supports the concept bifunctional drug therapy as a promising strategy to replace monofunctional therapies with greater efficacy and improved compliance.

  8. Reinforcement-related regulation of AMPA glutamate receptor subunits in the ventral tegmental area enhances motivation for cocaine.

    PubMed

    Choi, Kwang Ho; Edwards, Scott; Graham, Danielle L; Larson, Erin B; Whisler, Kimberly N; Simmons, Diana; Friedman, Allyson K; Walsh, Jessica J; Rahman, Zia; Monteggia, Lisa M; Eisch, Amelia J; Neve, Rachael L; Nestler, Eric J; Han, Ming-Hu; Self, David W

    2011-05-25

    Chronic cocaine use produces numerous biological changes in brain, but relatively few are functionally associated with cocaine reinforcement. Here we show that daily intravenous cocaine self-administration, but not passive cocaine administration, induces dynamic upregulation of the AMPA glutamate receptor subunits GluR1 and GluR2 in the ventral tegmental area (VTA) of rats. Increases in GluR1 protein and GluR1(S845) phosphorylation are associated with increased GluR1 mRNA in self-administering animals, whereas increased GluR2 protein levels occurred despite substantial decreases in GluR2 mRNA. We investigated the functional significance of GluR1 upregulation in the VTA on cocaine self-administration using localized viral-mediated gene transfer. Overexpression of GluR1(WT) in rat VTA primarily infected dopamine neurons (75%) and increased AMPA receptor-mediated membrane rectification in these neurons with AMPA application. Similar GluR1(WT) overexpression potentiated locomotor responses to intra-VTA AMPA, but not NMDA, infusions. In cocaine self-administering animals, overexpression of GluR1(WT) in the VTA markedly increased the motivation for cocaine injections on a progressive ratio schedule of cocaine reinforcement. In contrast, overexpression of protein kinase A-resistant GluR1(S845A) in the VTA reduced peak rates of cocaine self-administration on a fixed ratio reinforcement schedule. Neither viral vector altered sucrose self-administration, and overexpression of GluR1(WT) or GluR1(S845A) in the adjacent substantia nigra had no effect on cocaine self-administration. Together, these results suggest that dynamic regulation of AMPA receptors in the VTA during cocaine self-administration contributes to cocaine addiction by acting to facilitate subsequent cocaine use.

  9. Facilitating actions of an AMPA receptor potentiator upon extinction of contextually conditioned fear response in stressed mice.

    PubMed

    Yamada, Daisuke; Wada, Keiji; Sekiguchi, Masayuki

    2011-01-25

    Extinction of conditioned fear response is thought to be a biological process underlying exposure therapy for anxiety disorders. We have previously reported that an AMPA receptor potentiator, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluorophenoxyacetamide (PEPA), facilitates extinction of fear memory formed through contextual fear conditioning in mice that had never been exposed to experimental stress. On the other hand, recent findings suggest that the fear extinction is impaired in stressed rats or mice. The purpose of the present study was to examine whether PEPA facilitates impaired extinction of fear in stressed mice. For this purpose, mice were applied stress (a 2h restraint, a 20min forced swim, and ether inhalation), and contextual fear conditioning was carried out 7 days later. After 1-3 days of conditioning, mice were re-exposed to the context for 6min, and behavioral freezing response was measured. The time mice spent frozen decreased following every extinction session, and the decrease was remarkably slower in the stressed mice than in control non-stressed mice. PEPA (3, 10, 30mg/kg body weight) or vehicle was intraperitoneally administered into stressed mice once before the first extinction session. The significant decrease of the freezing response in the extinction sessions was only seen in the 30mg/kg PEPA-administered stressed mice, compared with vehicle-administered stressed mice. A similar extent of decrease in the freezing response in the extinction sessions was observed in the PEPA-administered (30mg/kg) and d-cycloserine-administered (30mg/kg) mice. These results suggest that PEPA facilitates extinction of contextual fear in stressed mice.

  10. Differential dendritic targeting of AMPA receptor subunit mRNAs in adult rat hippocampal principal neurons and interneurons.

    PubMed

    Cox, David J; Racca, Claudia

    2013-06-15

    In hippocampal neurons, AMPA receptors (AMPARs) mediate fast excitatory postsynaptic responses at glutamatergic synapses, and are involved in various forms of synaptic plasticity. Dendritic local protein synthesis of selected AMPAR subunit mRNAs is considered an additional mechanism to independently and rapidly control the strength of individual synapses. We have used fluorescent in situ hybridization and immunocytochemistry to analyze the localization of AMPAR subunit (GluA1-4) mRNAs and their relationship with the translation machinery in principal cells and interneurons of the adult rat hippocampus. The mRNAs encoding all four AMPAR subunits were detected in the somata and dendrites of CA3 and CA1 pyramidal cells and those of six classes of CA1 γ-aminobutyric acid (GABA)ergic interneurons. GluA1-4 subunit mRNAs were highly localized to the apical dendrites of pyramidal cells, whereas in interneurons they were present in multiple dendrites. In contrast, in the dentate gyrus, GluA1-4 subunit mRNAs were virtually restricted to the somata and were absent from the dendrites of granule cells. These different regional and cell type-specific labeling patterns also correlated with the localization of markers for components of the protein synthesis machinery. Our results support the local translation of GluA1-4 mRNAs in dendrites of hippocampal pyramidal cells and CA1 interneurons but not in granule cells of the dentate gyrus. Furthermore, the regional and cell type-specific differences we observed suggest that each cell type uses distinct ways of regulating the local translation of AMPAR subunits.

  11. Methylphenidate amplifies long-term potentiation in rat hippocampus CA1 area involving the insertion of AMPA receptors by activation of β-adrenergic and D1/D5 receptors.

    PubMed

    Rozas, C; Carvallo, C; Contreras, D; Carreño, M; Ugarte, G; Delgado, R; Zeise, M L; Morales, B

    2015-12-01

    Methylphenidate (MPH, Ritalin©) is widely used in the treatment of Attention Deficit Hyperactivity Disorder and recently as a drug of abuse. Although the effect of MPH has been studied in brain regions such as striatum and prefrontal cortex (PFC), the hippocampus has received relatively little attention. It is known that MPH increases the TBS-dependent Long Term Potentiation (LTP) in the CA1 area. However, the cellular and molecular mechanisms involved in this process are still unknown. Using field potential recordings and western blot analysis in rat hippocampal slices of young rats, we found that acute application of MPH enhances LTP in CA3-CA1 synapses in a dose-dependent manner with an EC50 of 73.44±6.32 nM. Using specific antagonists and paired-pulse facilitation protocols, we observed that the MPH-dependent increase of LTP involves not only β-adrenergic receptors activation but also post-synaptic D1/D5 dopamine receptors. The inhibition of PKA with PKI, suppressed the facilitation of LTP induced by MPH consistent with an involvement of the adenyl cyclase-cAMP-PKA dependent cascade downstream of the activation of D1/D5 receptors. In addition, samples of CA1 areas taken from slices potentiated with MPH presented an increase in the phosphorylation of the Ser845 residue of the GluA1 subunit of AMPA receptors compared to control slices. This effect was reverted by SCH23390, antagonist of D1/D5 receptors, and PKI. Moreover, we found an increase of surface-associated functional AMPA receptors. We propose that MPH increases TBS-dependent LTP in CA3-CA1 synapses through a polysynaptic mechanism involving activation of β-adrenergic and D1/D5 dopaminergic receptors and promoting the trafficking and insertion of functional AMPA receptors to the plasma membrane.

  12. Auxiliary Subunit GSG1L Acts to Suppress Calcium-Permeable AMPA Receptor Function

    PubMed Central

    McGee, Thomas P.; Bats, Cécile

    2015-01-01

    AMPA-type glutamate receptors are ligand-gated cation channels responsible for a majority of the fast excitatory synaptic transmission in the brain. Their behavior and calcium permeability depends critically on their subunit composition and the identity of associated auxiliary proteins. Calcium-permeable AMPA receptors (CP-AMPARs) contribute to various forms of synaptic plasticity, and their dysfunction underlies a number of serious neurological conditions. For CP-AMPARs, the prototypical transmembrane AMPAR regulatory protein stargazin, which acts as an auxiliary subunit, enhances receptor function by increasing single-channel conductance, slowing channel gating, increasing calcium permeability, and relieving the voltage-dependent block by endogenous intracellular polyamines. We find that, in contrast, GSG1L, a transmembrane auxiliary protein identified recently as being part of the AMPAR proteome, acts to reduce the weighted mean single-channel conductance and calcium permeability of recombinant CP-AMPARs, while increasing polyamine-dependent rectification. To examine the effects of GSG1L on native AMPARs, we manipulated its expression in cerebellar and hippocampal neurons. Transfection of GSG1L into mouse cultured cerebellar stellate cells that lack this protein increased the inward rectification of mEPSCs. Conversely, shRNA-mediated knockdown of endogenous GSG1L in rat cultured hippocampal pyramidal neurons led to an increase in mEPSC amplitude and in the underlying weighted mean single-channel conductance, revealing that GSG1L acts to suppress current flow through native CP-AMPARs. Thus, our data suggest that GSG1L extends the functional repertoire of AMPAR auxiliary subunits, which can act not only to enhance but also diminish current flow through their associated AMPARs. SIGNIFICANCE STATEMENT Calcium-permeable AMPA receptors (CP-AMPARs) are an important group of receptors for the neurotransmitter glutamate. These receptors contribute to various forms of

  13. Glyphosate and AMPA in U.S. streams, groundwater, precipitation and soils

    USGS Publications Warehouse

    Battaglin, William A.; Meyer, Michael T.; Kuivila, Kathryn; Dietze, Julie E.

    2014-01-01

    Herbicides containing glyphosate are used in more than 130 countries on more than 100 crops. In the United States (U.S.), agricultural use of glyphosate [N-(phosphonomethyl)glycine] has increased from less than 10,000 metric tons per year (active ingredient) in 1993 to more than 70,000 metric tons per year in 2006. In 2006, glyphosate accounted for about 20 percent of all herbicide use (by weight of active ingredient). Glyphosate formulations such as Roundup® are used in homes and in agriculture. Part of the reason for the popularity of glyphosate is the perception that it is an “environmentally benign” herbicide that has low toxicity and little mobility or persistence in the environment. The U.S. Geological Survey developed an analytical method using liquid chromatography/tandem mass spectrometry that can detect small amounts of glyphosate and its primary degradation product aminomethylphosphonic acid (AMPA) in water and sediment. Results from more than 2,000 samples collected from locations distributed across the U.S. indicate that glyphosate is more mobile and occurs more widely in the environment than was previously thought. Glyphosate and AMPA were detected (reporting limits between 0.1 and 0.02 micrograms per liter) in samples collected from surface water, groundwater, rainfall, soil water, and soil, at concentrations from less than 0.1 to more than 100 micrograms per liter. Glyphosate was detected more frequently in rain (86%), ditches and drains (71%), and soil (63%); and less frequently in groundwater (3%) and large rivers (18%). AMPA was detected more frequently in rain (86%), soil (82%), and large rivers (78%); and less frequently in groundwater (8%) and wetlands or vernal pools (37%). Most observed concentrations of glyphosate were well below levels of concern for humans or wildlife, and none exceeded the U.S. Environmental Protection Agency’s Maximum Contaminant Level of 700 micrograms per liter. However, the ecosystem effects of chronic low

  14. Amyloid-β effects on synapses and memory require AMPA receptor subunit GluA3

    PubMed Central

    Reinders, Niels R.; Pao, Yvonne; Renner, Maria C.; da Silva-Matos, Carla M.; Lodder, Tessa R.; Malinow, Roberto; Kessels, Helmut W.

    2016-01-01

    Amyloid-β (Aβ) is a prime suspect for causing cognitive deficits during the early phases of Alzheimer’s disease (AD). Experiments in AD mouse models have shown that soluble oligomeric clusters of Aβ degrade synapses and impair memory formation. We show that all Aβ-driven effects measured in these mice depend on AMPA receptor (AMPAR) subunit GluA3. Hippocampal neurons that lack GluA3 were resistant against Aβ-mediated synaptic depression and spine loss. In addition, Aβ oligomers blocked long-term synaptic potentiation only in neurons that expressed GluA3. Furthermore, although Aβ-overproducing mice showed significant memory impairment, memories in GluA3-deficient congenics remained unaffected. These experiments indicate that the presence of GluA3-containing AMPARs is critical for Aβ-mediated synaptic and cognitive deficits. PMID:27708157

  15. KCC2 Gates Activity-Driven AMPA Receptor Traffic through Cofilin Phosphorylation.

    PubMed

    Chevy, Quentin; Heubl, Martin; Goutierre, Marie; Backer, Stéphanie; Moutkine, Imane; Eugène, Emmanuel; Bloch-Gallego, Evelyne; Lévi, Sabine; Poncer, Jean Christophe

    2015-12-02

    Expression of the neuronal K/Cl transporter KCC2 is tightly regulated throughout development and by both normal and pathological neuronal activity. Changes in KCC2 expression have often been associated with altered chloride homeostasis and GABA signaling. However, recent evidence supports a role of KCC2 in the development and function of glutamatergic synapses through mechanisms that remain poorly understood. Here we show that suppressing KCC2 expression in rat hippocampal neurons precludes long-term potentiation of glutamatergic synapses specifically by preventing activity-driven membrane delivery of AMPA receptors. This effect is independent of KCC2 transporter function and can be accounted for by increased Rac1/PAK- and LIMK-dependent cofilin phosphorylation and actin polymerization in dendritic spines. Our results demonstrate that KCC2 plays a critical role in the regulation of spine actin cytoskeleton and gates long-term plasticity at excitatory synapses in cortical neurons.

  16. Synaptic fusion pore structure and AMPA receptor activation according to Brownian simulation of glutamate diffusion.

    PubMed

    Ventriglia, Francesco; Maio, Vito Di

    2003-03-01

    The rising phase of fast, AMPA-mediated Excitatory Post Synaptic Currents (EPSCs) has a primary role in the computational ability of neurons. The structure and radial expansion velocity of the fusion pore between the vesicle and the presynaptic membrane could be important factors in determining the time course of the EPSC. We have used a Brownian simulation model for glutamate neurotransmitter diffusion to test two hypotheses on the fusion pore structure, namely, the proteinaceous pore and the purely lipidic pore. Three more hypotheses on the radial expansion velocity were also tested. The rising phases of the EPSC, computed under various conditions, were compared with experimental data from the literature. Our present results show that a proteinaceous fusion pore should produce a more marked foot at the beginning of the rising phase of the EPSC. They also confirm the hypothesis that the structure of the fusion pore and its radial expansion velocity play significant roles in shaping the fast EPSC time course.

  17. The AAA+ ATPase, Thorase Regulates AMPA Receptor-Dependent Synaptic Plasticity and Behavior

    PubMed Central

    Zhang, Jianmin; Wang, Yue; Chi, Zhikai; Keuss, Matthew J.; Pai, Ying-Min Emily; Kang, Ho Chul; Shin, Jooho; Bugayenko, Artem; Wang, Hong; Xiong, Yulan; Pletnikov, Mikhail V.; Mattson, Mark P.; Dawson, Ted M.; Dawson, Valina L.

    2011-01-01

    SUMMARY The synaptic insertion or removal of AMPA receptors (AMPAR) plays critical roles in the regulation of synaptic activity reflected in the expression of long-term potentiation (LTP) and long-term depression (LTD). The cellular events underlying this important process in learning and memory are still being revealed. Here we describe and characterize the AAA+ ATPase, Thorase, that regulates the expression of surface AMPAR. In an ATPase-dependent manner Thorase mediates the internalization of AMPAR by disassembling the AMPAR-GRIP1 complex. Following genetic deletion of Thorase, the internalization of AMPAR is substantially reduced, leading to increased amplitudes of miniature excitatory postsynaptic currents, enhancement of LTP and elimination of LTD. These molecular events are expressed as deficits in learning and memory in Thorase null mice. This study identifies an AAA+ ATPase that plays a critical role in regulating the surface expression of AMPAR and thereby regulates synaptic plasticity and learning and memory. PMID:21496646

  18. Calcium-permeable AMPA receptors in neonatal hypoxic-ischemic encephalopathy (Review)

    PubMed Central

    TANG, XIAO-JUAN; XING, FENG

    2013-01-01

    Hypoxic-ischemic encephalopathy (HIE) is an important cause of brain injury in the newborn and may result in long-term devastating consequences. Excessive stimulation of glutamate receptors (GluRs) is a pivotal mechanism underlying ischemia-induced selective and delayed neuronal death. Although initial studies focused on N-methyl-D-aspartic acid (NMDA) receptors as critical mediators in HIE, subsequent studies supported a more central role for α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (AMPARs), particularly Ca2+-permeable AMPARs, in brain damage associated with hypoxia-ischemia. This study reviewed the important role of Ca2+-permeable AMPARs in HIE and the future potential neuroprotective strategies associated with Ca2+-permeable AMPARs. PMID:24649036

  19. Synaptic transmission and plasticity require AMPA receptor anchoring via its N-terminal domain.

    PubMed

    Watson, Jake F; Ho, Hinze; Greger, Ingo H

    2017-03-14

    AMPA-type glutamate receptors (AMPARs) mediate fast excitatory neurotransmission and are selectively recruited during activity-dependent plasticity to increase synaptic strength. A prerequisite for faithful signal transmission is the positioning and clustering of AMPARs at postsynaptic sites. The mechanisms underlying this positioning have largely been ascribed to the receptor cytoplasmic C-termini and to AMPAR-associated auxiliary subunits, both interacting with the postsynaptic scaffold. Here, using mouse organotypic hippocampal slices, we show that the extracellular AMPAR N-terminal domain (NTD), which projects midway into the synaptic cleft, plays a fundamental role in this process. This highly sequence-diverse domain mediates synaptic anchoring in a subunit-selective manner. Receptors lacking the NTD exhibit increased mobility in synapses, depress synaptic transmission and are unable to sustain long-term potentiation (LTP). Thus, synaptic transmission and the expression of LTP are dependent upon an AMPAR anchoring mechanism that is driven by the NTD.

  20. Ca2+ Permeable AMPA Channels in Diseases of the Nervous System

    PubMed Central

    Weiss, John H.

    2011-01-01

    Since the discovery and molecular characterization of Ca2+-permeable AMPA channels just over two decades ago, a large body of evidence has accumulated implicating contributions of these unusual glutamate activated channels to selective neurodegeneration in certain conditions, including ischemia and amyotrophic lateral sclerosis. Factors likely involved in their contributions to disease include their distinct patterns of expression in certain neuronal populations, their upregulation via various mechanisms in response to disease associated stresses, and their high permeability to Zn2+ as well as to Ca2+. However, full characterization of their contributions to certain diseases as well as development of therapeutics has been limited by the lack of selective and bioavailable blockers of these channels that can be employed in animals or humans. This review summarizes some of the clues that have emerged over recent years to the contributions of these channels in disease. PMID:22102834

  1. Costimulation of AMPA and metabotropic glutamate receptors underlies phospholipase C activation by glutamate in hippocampus.

    PubMed

    Kim, Hye-Hyun; Lee, Kyu-Hee; Lee, Doyun; Han, Young-Eun; Lee, Suk-Ho; Sohn, Jong-Woo; Ho, Won-Kyung

    2015-04-22

    Glutamate, a major neurotransmitter in the brain, activates ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs, respectively). The two types of glutamate receptors interact with each other, as exemplified by the modulation of iGluRs by mGluRs. However, the other way of interaction (i.e., modulation of mGluRs by iGluRs) has not received much attention. In this study, we found that group I mGluR-specific agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) alone is not sufficient to activate phospholipase C (PLC) in rat hippocampus, while glutamate robustly activates PLC. These results suggested that additional mechanisms provided by iGluRs are involved in group I mGluR-mediated PLC activation. A series of experiments demonstrated that glutamate-induced PLC activation is mediated by mGluR5 and is facilitated by local Ca(2+) signals that are induced by AMPA-mediated depolarization and L-type Ca(2+) channel activation. Finally, we found that PLC and L-type Ca(2+) channels are involved in hippocampal mGluR-dependent long-term depression (mGluR-LTD) induced by paired-pulse low-frequency stimulation, but not in DHPG-induced chemical LTD. Together, we propose that AMPA receptors initiate Ca(2+) influx via the L-type Ca(2+) channels that facilitate mGluR5-PLC signaling cascades, which underlie mGluR-LTD in rat hippocampus.

  2. Pharmacology of ampakine modulators: from AMPA receptors to synapses and behavior.

    PubMed

    Arai, A C; Kessler, M

    2007-05-01

    Ampakines are drugs structurally derived from aniracetam that potentiate currents mediated by AMPA type glutamate receptors. These drugs slow deactivation and attenuate desensitization of AMPA receptor currents, increase synaptic responses and enhance long-term potentiation. This review focuses mainly on recent physiological studies and on evidence for two distinct subfamilies. Type I compounds like CX546 are very effective in prolonging synaptic responses while type II compounds like CX516 mainly increase response amplitude. Type I and II drugs do not compete in binding assays and thus presumably act through separate sites. Their differences are likely to have consequences also for synaptic plasticity and behavior. Thus, while all ampakines facilitated long-term potentiation, only CX546 enhanced long-term depression. Further discussed are studies showing that ampakine effects vary substantially between neurons, with increases in EPSCs being larger in CA1 pyramidal cells than in thalamus and in hippocampal interneurons. In behavioral tests, ampakines facilitate learning in many paradigms including odor discrimination, spatial mazes, and conditioning, and they improved short-term memory in a non-matching-to-sample task. Positive results were also obtained in various psychological tests with human subjects. The drugs were effective in correcting behaviors in various animal models of schizophrenia and depression. Lastly, evidence is discussed that ampakines have few adverse effects at therapeutically relevant concentrations and that they protect neurons against neurotoxic insults, in part by mobilizing growth factors like BDNF. Type II drugs like CX516 in particular appear to be inherently safe since their ability to prolong responses is kinetically limited.

  3. AMPA receptor activation causes preferential mitochondrial Ca²⁺ load and oxidative stress in motor neurons.

    PubMed

    Joshi, Dinesh C; Tewari, Bhanu P; Singh, Mahendra; Joshi, Preeti G; Joshi, Nanda B

    2015-08-07

    It is well established that motor neurons are highly vulnerable to glutamate induced excitotoxicity. The selective vulnerability of these neurons has been attributed to AMPA receptor mediated excessive rise in cytosolic calcium and consequent mitochondrial Ca(2+) loading. Earlier we have reported that in motor neurons a generic rise in [Ca(2+)]i does not always lead to mitochondrial Ca(2+) loading and membrane depolarization but it occurs upon AMPA receptor activation. The mechanism of such specific mitochondrial involvement upon AMPA receptor activation is not known. The present study examines the mitochondrial Ca(2+) regulation and oxidative stress in spinal cord neurons upon AMPA subtype of glutamate receptor activation. Stimulating the spinal neurons with AMPA exhibited a sharp rise in [Ca(2+)]m in both motor and other spinal neurons that was sustained up to the end of recording time of 30min. The rise in [Ca(2+)]m was substantially higher in motor neurons than in other spinal neurons which could be due to the differential mitochondrial homeostasis in two types of neurons. To examine this possibility, we measured AMPA induced [Ca(2+)]m loading in the presence of mitochondrial inhibitors. In both cell types the AMPA induced [Ca(2+)]m loading was blocked by mitochondrial calcium uniporter blocker ruthenium red. In motor neurons it was also inhibited substantially by CGP37157 and cyclosporine-A, the blockers of Na(+)/Ca(2+) exchanger and mitochondrial permeability transition pore (MPTP) respectively, whereas no effect of these agents was observed in other spinal neurons. Thus in motor neurons the Ca(2+) sequestration by mitochondria occurs through mitochondrial calcium uniporter as well as due to reversal of Na(+)/Ca(2+) exchanger, in contrast the latter pathway does not contribute in other spinal neurons. The ROS formation was inhibited by nitric oxide synthase (NOS) inhibitor L-NAME in both types of neurons, however the mitochondrial complex-I inhibitor rotenone

  4. Editing for an AMPA receptor subunit RNA in prefrontal cortex and striatum in Alzheimer's disease, Huntington's disease and schizophrenia

    NASA Technical Reports Server (NTRS)

    Akbarian, S.; Smith, M. A.; Jones, E. G.; Bloom, F. E. (Principal Investigator)

    1995-01-01

    Animal studies and cell culture experiments demonstrated that posttranscriptional editing of the transcript of the GluR-2 gene, resulting in substitution of an arginine for glutamine in the second transmembrane region (TM II) of the expressed protein, is associated with a reduction in Ca2+ permeability of the receptor channel. Thus, disturbances in GluR-2 RNA editing with alteration of intracellular Ca2+ homeostasis could lead to neuronal dysfunction and even neuronal degeneration. The present study determined the proportions of edited and unedited GluR-2 RNA in the prefrontal cortex of brains from patients with Alzheimer's disease, in the striatum of brains from patients with Huntington's disease, and in the same areas of brains from age-matched schizophrenics and controls, by using reverse transcriptase-polymerase chain reaction, restriction endonuclease digestion, gel electrophoresis and scintillation radiometry. In the prefrontal cortex of controls, < 0.1% of all GluR-2 RNA molecules were unedited and > 99.9% were edited; in the prefrontal cortex both of schizophrenics and of Alzheimer's patients approximately 1.0% of all GluR-2 RNA molecules were unedited and 99% were edited. In the striatum of controls and of schizophrenics, approximately 0.5% of GluR-2 RNA molecules were unedited and 99.5% were edited; in the striatum of Huntington's patients nearly 5.0% of GluR-2 RNA was unedited. In the prefrontal white matter of controls, approximately 7.0% of GluR-2 RNA was unedited. In the normal human prefrontal cortex and striatum, the large majority of GluR-2 RNA molecules contains a CGG codon for arginine in the TMII coding region; this implies that the corresponding AMPA receptors have a low Ca2+ permeability, as previously demonstrated for the rat brain. The process of GluR-2 RNA editing is compromised in a region-specific manner in schizophrenia, in Alzheimer's disease and Huntington's Chorea although in each of these disorders there is still a large excess of

  5. Nucleus Accumbens AMPA Receptors Are Necessary for Morphine-Withdrawal-Induced Negative-Affective States in Rats

    PubMed Central

    Russell, Shayla E.; Puttick, Daniel J.; Sawyer, Allison M.; Potter, David N.; Mague, Stephen; Carlezon, William A.

    2016-01-01

    Dependence is a hallmark feature of opiate addiction and is defined by the emergence of somatic and affective withdrawal signs. The nucleus accumbens (NAc) integrates dopaminergic and glutamatergic inputs to mediate rewarding and aversive properties of opiates. Evidence suggests that AMPA glutamate-receptor-dependent synaptic plasticity within the NAc underlies aspects of addiction. However, the degree to which NAc AMPA receptors (AMPARs) contribute to somatic and affective signs of opiate withdrawal is not fully understood. Here, we show that microinjection of the AMPAR antagonist NBQX into the NAc shell of morphine-dependent rats prevented naloxone-induced conditioned place aversions and decreases in sensitivity to brain stimulation reward, but had no effect on somatic withdrawal signs. Using a protein cross-linking approach, we found that the surface/intracellular ratio of NAc GluA1, but not GluA2, increased with morphine treatment, suggesting postsynaptic insertion of GluA2-lacking AMPARs. Consistent with this, 1-naphthylacetyl spermine trihydrochloride (NASPM), an antagonist of GluA2-lacking AMPARs, attenuated naloxone-induced decreases in sensitivity to brain stimulation reward. Naloxone decreased the surface/intracellular ratio and synaptosomal membrane levels of NAc GluA1 in morphine-dependent rats, suggesting a compensatory removal of AMPARs from synaptic zones. Together, these findings indicate that chronic morphine increases synaptic availability of GluA1-containing AMPARs in the NAc, which is necessary for triggering negative-affective states in response to naloxone. This is broadly consistent with the hypothesis that activation of NAc neurons produces acute aversive states and raises the possibility that inhibiting AMPA transmission selectively in the NAc may have therapeutic value in the treatment of addiction. SIGNIFICANCE STATEMENT Morphine dependence and withdrawal result in profound negative-affective states that play a major role in the

  6. Modulation of N-methyl-D-aspartate and (R,S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) responses of spinal nociceptive neurons by a N-terminal fragment of substance P.

    PubMed

    Budai, D; Wilcox, G L; Larson, A A

    1992-06-17

    The effects of an N-terminal fragment of substance P, substance P-(1-7) [SP-(1-7)], on the responses of dorsal horn nociceptive neurons to N-methyl-D-aspartate (NMDA) and (R,S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) were tested by combined single-unit extracellular recordings/microiontophoresis. While SP-(1-7) had no effects when applied by itself, it was a potent and long-lasting modulator of both NMDA- and AMPA-mediated excitation of spinal dorsal horn nociceptive neurons. NMDA responses were transiently decreased (by an average of 36% of control at minimum) by SP-(1-7) followed by a more sustained increase (by 76% at maximum). In contrast, AMP responses were only increased by SP-(1-7) (by 81% at maximum). It is hypothesized that the actions of SP-(1-7) on excitatory amino acid (EAA) responses of dorsal horn nociceptive neurons reflect a novel mechanism by which SP and EAAs interact to modulate pain transmission.

  7. Parvalbumin-containing interneurons in rat hippocampus have an AMPA receptor profile suggestive of vulnerability to excitotoxicity.

    PubMed

    Moga, Diana; Hof, Patrick R; Vissavajjhala, Prabhakar; Moran, Thomas M; Morrison, John H

    2002-05-01

    alpha-Amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors mediate excitatory neurotransmission in the central nervous system, and contain combinations of four subunits (GluR1-4). We developed a GluR3-specific monoclonal antibody and quantified the cellular distribution of GluR3 in rat hippocampus. GluR3 immunoreactivity was detected in all pyramidal neurons and most interneurons. In addition, we found a subset of parvalbumin (PV)-containing interneurons in the hippocampus and neocortex that was notable for its intense GluR3 immunoreactivity and lack of GluR2 immunoreactivity. Such an expression pattern of AMPA receptor subunits is likely to make these interneurons selectively vulnerable to excitotoxicity.

  8. [EFfect of quinazolone-alkyl-carboxylic acid derivatives on the transmembrane Ca2+ ion flux mediated by AMPA receptors].

    PubMed

    Szárics, Eva; LaszTóczi, Bálint; Nyikos, Lajos; Barabás, Péter; Kovács, Ilona; Skuban, Nina; Nagy, Péter I; Kökösi, József; Takácsné, Novák Krisztina; Kardos, Julianna

    2002-01-01

    The excitatory neurotransmitter, Glu, plays a crucial role in many sensory and motor functions as well as in brain development, learning and memory and it is also involved in the pathogenesis of a number of neurological disorders, including epilepsy, Alzheimer's and Parkinson's diseases. Therefore, the study of Glu receptors (GluRs) is of therapeutical importance. We showed here by fluorescence monitoring of transmembrane Ca2+ ion fluxes in response to (S)-alpha-amino-3-hidroxi-5-metil-4-izoxazol propionic acid ((S)-AMPA) on the time scale of 0.00004-10 s that Ca2+ ion influx proceeds through faster and slower desensitizing receptors. Pharmacological isolation of the slower and faster desensitizing AMPA receptor was possible by fluorescence monitoring of Ca2+ ion translocation in response to (S)-AMPA in the presence and absence of various 2-methyl-4-oxo-3H-quinazoline-3-alkyl-carboxilic acid derivatives (Qxs): the acetic acid Q1 inhibits the slower desensitizing receptor response specifically, while the acetyl-piperidine Q5 is a more potent inhibitor of the faster desensitizing receptor response. In addition, spontaneous interictal activity, as induced by high [K+] conditions in hippocampal slices, was reduced significantly by Q5, suggesting a possible anticonvulsant property of Q5. Substitutions of Qxs into the GluR2 S1S2 binding core were consistent with their effect by causing variable degree of S1S2 bridging interaction as one of the main determinants of AMPA receptor agonist activity. The exploitation of differences between similar receptors will be important in the development and use of drugs with high pharmacological specificity.

  9. STAT1 Regulates the Homeostatic Component of Visual Cortical Plasticity via an AMPA Receptor-Mediated Mechanism

    PubMed Central

    Van Wart, Audra; Petravicz, Jeremy; Tropea, Daniela

    2014-01-01

    Accumulating evidence points to a role for Janus kinase/signal transducers and activators of transcription (STAT) immune signaling in neuronal function; however, its role in experience-dependent plasticity is unknown. Here we show that one of its components, STAT1, negatively regulates the homeostatic component of ocular dominance plasticity in visual cortex. After brief monocular deprivation (MD), STAT1 knock-out (KO) mice show an accelerated increase of open-eye responses, to a level comparable with open-eye responses after a longer duration of MD in wild-type (WT) mice. Therefore, this component of plasticity is abnormally enhanced in KO mice. Conversely, increasing STAT1 signaling by IFNγ treatment in WT mice reduces the homeostatic component of plasticity by impairing open-eye responses. Enhanced plasticity in KO mice is accompanied by sustained surface levels of GluA1 AMPA receptors and increased amplitude and frequency of AMPA receptor-mediated mEPSCs, which resemble changes in WT mice after a longer duration of MD. These results demonstrate a unique role for STAT1 during visual cortical plasticity in vivo through a mechanism that includes AMPA receptors. PMID:25080587

  10. Reversal of aging-related emotional memory deficits by norepinephrine via regulating the stability of surface AMPA receptors.

    PubMed

    Luo, Yi; Zhou, Jun; Li, Ming-Xing; Wu, Peng-Fei; Hu, Zhuang-Li; Ni, Lan; Jin, You; Chen, Jian-Guo; Wang, Fang

    2015-04-01

    Aging-related emotional memory deficit is a well-known complication in Alzheimer's disease and normal aging. However, little is known about its molecular mechanism. To address this issue, we examined the role of norepinephrine (NE) and its relevant drug desipramine in the regulation of hippocampal long-term potentiation (LTP), surface expression of AMPA receptor, and associative fear memory in rats. We found that there was a defective regulation of NE content and AMPA receptor trafficking during fear conditioning, which were accompanied by impaired emotional memory and LTP in aged rats. Furthermore, we also found that the exogenous upregulation of NE ameliorated the impairment of LTP and emotional memory via enhancing AMPA receptor trafficking in aged rats, and the downregulation of NE impaired LTP in adult rats. Finally, acute treatment with NE or desipramine rescued the impaired emotional memory in aged rats. These results imply a pivotal role for NE in synaptic plasticity and associative fear memory in aging rats and suggest that desipramine is a potential candidate for treating aging-related emotional memory deficit.

  11. Amyotrophic Lateral Sclerosis 2-Deficiency Leads to Neuronal Degeneration in Amyotrophic Lateral Sclerosis through Altered AMPA Receptor Trafficking

    PubMed Central

    Lai, Chen; Xie, Chengsong; McCormack, Stefanie G.; Chiang, Hsueh-Cheng; Michalak, Marta K.; Lin, Xian; Chandran, Jayanth; Shim, Hoon; Shimoji, Mika; Cookson, Mark R.; Huganir, Richard L.; Rothstein, Jeffrey D.; Price, Donald L.; Wong, Philip C.; Martin, Lee J.; Zhu, J. Julius; Cai, Huaibin

    2008-01-01

    Amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron disease is caused by a selective loss of motor neurons. One form of juvenile onset autosomal recessive ALS (ALS2) has been linked to the loss of function of the ALS2 gene. The pathogenic mechanism of ALS2-deficiency, however, remains unclear. To further understand the function of alsin that is encoded by the full-length ALS2 gene, we screened proteins interacting with alsin. Here, we report that alsin interacted with glutamate receptor interacting protein 1 (GRIP1) both in vitro and in vivo, and colocalized with GRIP1 in neurons. In support of the physiological interaction between alsin and GRIP1, the subcellular distribution of GRIP1 was altered in ALS2-/- spinal motor neurons, which correlates with a significant reduction of AMPA-type glutamate receptor subunit 2 (GluR2) at the synaptic/cell surface of ALS2-/- neurons. The decrease of calcium-impermeable GluR2-containing AMPA receptors at the cell/synaptic surface rendered ALS2-/- neurons more susceptible to glutamate receptor-mediated neurotoxicity. Our findings reveal a novel function of alsin in AMPA receptor trafficking and provide a novel pathogenic link between ALS2-deficiency and motor neuron degeneration, suggesting a protective role of alsin in maintaining the survival of motor neurons. PMID:17093100

  12. Laboratory calibration of a POCIS-like sampler based on molecularly imprinted polymers for glyphosate and AMPA sampling in water.

    PubMed

    Berho, Catherine; Claude, Bérengère; Coisy, Emeline; Togola, Anne; Bayoudh, Sami; Morin, Philippe; Amalric, Laurence

    2017-03-01

    For more than 15 years, integrative passive sampling has been successfully used for monitoring contaminants in water, but no passive sampling device exists for strongly polar organic compounds, such as glyphosate. We thus propose a polar organic chemical integrative sampler (POCIS)-like tool dedicated to glyphosate and its main degradation product aminomethylphosphonic acid (AMPA), and describe the laboratory calibration of such a tool for calculating the sampling rates of glyphosate and AMPA. This passive sampler consists of a POCIS with molecularly imprinted polymer as a receiving phase and a polyethersulfone diffusion membrane. The calibration experiment for the POCIS was conducted for 35 days in a continuous water-flow-through exposure system. The calibration results show that the sampling rates are 111 and 122 mL day(-1) for glyphosate and AMPA respectively, highlighting the potential interest in and the applicability of this method for environmental monitoring. The influence of membrane porosity on the glyphosate sampling rate was also tested. Graphical Abstract ᅟ.

  13. Structurally dissimilar antimanic agents modulate synaptic plasticity by regulating AMPA glutamate receptor subunit GluR1 synaptic expression.

    PubMed

    Du, Jing; Gray, Neil A; Falke, Cynthia; Yuan, Peixiong; Szabo, Steven; Manji, Husseini K

    2003-11-01

    A growing body of data from clinical and preclinical studies suggests that the glutamatergic system may represent a novel therapeutic target for severe recurrent mood disorders. Since synapse-specific glutamate receptor expression/localization is known to play critical roles in synaptic plasticity, we investigated the effects of mood stabilizers on AMPA receptor expression. Rats were treated chronically with lithium or valproate, hippocampal synaptosomes were isolated, and GluR1 levels were determined. Additionally, hippocampal neurons were prepared from E18 rat embryos and treated with lithium or valproate. Surface expression of GluR1 was determined using a biotinylation assay, and double-immunostaining with anti-GluR1 and anti-synaptotagmin antibodies was used to determine synaptic GluR1 levels. The AMPA receptor subunit GluR1 expression in hippocampal synaptosomes was significantly reduced by both chronic lithium and valproate. Overall, these studies show that AMPA receptor subunit GluR1 is a common target for two structurally highly dissimilar, but highly efficacious, mood stabilizers, lithium and valproate. These studies suggest that regulation of glutamatergically mediated synaptic plasticity may play a role in the treatment of mood disorders, and raise the possibility that agents more directly affecting synaptic GluR1 may represent novel therapies for this devastating illness.

  14. Calcium-Permeable AMPA Receptors in the Nucleus Accumbens Regulate Depression-Like Behaviors in the Chronic Neuropathic Pain State

    PubMed Central

    Goffer, Yossef; Xu, Duo; Eberle, Sarah E.; D'amour, James; Lee, Michelle; Tukey, David; Froemke, Robert C.; Ziff, Edward B.

    2013-01-01

    Depression is a salient emotional feature of chronic pain. Depression alters the pain threshold and impairs functional recovery. To date, however, there has been limited understanding of synaptic or circuit mechanisms that regulate depression in the pain state. Here, we demonstrate that depression-like behaviors are induced in a rat model of chronic neuropathic pain. Using this model, we show that chronic pain selectively increases the level of GluA1 subunits of AMPA-type glutamate receptors at the synapses of the nucleus accumbens (NAc), a key component of the brain reward system. We find, in addition, that this increase in GluA1 levels leads to the formation of calcium-permeable AMPA receptors (CPARs). Surprisingly, pharmacologic blockade of these CPARs in the NAc increases depression-like behaviors associated with pain. Consistent with these findings, an AMPA receptor potentiator delivered into the NAc decreases pain-induced depression. These results show that transmission through CPARs in the NAc represents a novel molecular mechanism modulating the depressive symptoms of pain, and thus CPARs may be a promising therapeutic target for the treatment of pain-induced depression. More generally, these findings highlight the role of central glutamate signaling in pain states and define the brain reward system as an important region for the regulation of depressive symptoms of pain. PMID:24285907

  15. AMPA-receptor activation is involved in the antiamnesic effect of DM 232 (unifiram) and DM 235 (sunifiram).

    PubMed

    Galeotti, N; Ghelardini, C; Pittaluga, A; Pugliese, A M; Bartolini, A; Manetti, D; Romanelli, M N; Gualtieri, F

    2003-12-01

    DM 232 and DM 235 are novel antiamnesic compounds structurally related to ampakines. The involvement of AMPA receptors in the mechanism of action of DM 232 and DM 235 was, therefore, investigated in vivo and in vitro. Both compounds (0.1 mg/kg(-1) i.p.) were able to reverse the amnesia induced by the AMPA receptor antagonist NBQX (30 mg/kg(-1) i.p.) in the mouse passive avoidance test. At the effective doses, the investigated compounds did not impair motor coordination, as revealed by the rota rod test, nor modify spontaneous motility and inspection activity, as revealed by the hole board test. DM 232 and DM 235 reversed the antagonism induced by kynurenic acid of the NMDA-mediated release of [(3)H]NA in the kynurenate test performed in rat hippocampal slices. This effect was abolished by NBQX. DM 232 increases, in a concentration dependent manner, excitatory synaptic transmission in the rat hippocampus in vitro. These results suggest that DM 232 and DM 235 act as cognition enhancers through the activation of the AMPA-mediated neurotransmission system.

  16. Growth hormone (GH) increases cognition and expression of ionotropic glutamate receptors (AMPA and NMDA) in transgenic zebrafish (Danio rerio).

    PubMed

    Studzinski, Ana Lupe Motta; Barros, Daniela Martí; Marins, Luis Fernando

    2015-11-01

    The growth hormone/insulin-like factor I (GH/IGF-I) somatotropic axis is responsible for somatic growth in vertebrates, and has important functions in the nervous system. Among these, learning and memory functions related to the neural expression of ionotropic glutamate receptors, mainly types AMPA (α-amino-3hydroxy-5methylisoxazole-4propionic) and NMDA (N-methyl-d-aspartate) can be highlighted. Studies on these mechanisms have been almost exclusively conducted on mammal models, with little information available on fish. Consequently, this study aimed at evaluating the effects of the somatotropic axis on learning and memory of a GH-transgenic zebrafish (Danio rerio) model (F0104 strain). Long-term memory (LTM) was tested in an inhibitory avoidance apparatus, and brain expression of igf-I and genes that code for the main subunits of the AMPA and NMDA receptors were evaluated. Results showed a significant increase in LTM for transgenic fish. Transgenic animals also showed a generalized pattern of increase in the expression of AMPA and NMDA genes, as well as a three-fold induction in igf-I expression in the brain. When analyzed together, these results indicate that GH, mediated by IGF-I, has important effects on the brain, with improvement in LTM as a result of increased glutamate receptors. The transgenic strain F0104 was shown to be an interesting model for elucidating the intricate mechanisms related to the effect of the somatotropic axis on learning and memory in vertebrates.

  17. Tracing the origin and mobilization of Glyphosate and AMPA in a vineyard catchment

    NASA Astrophysics Data System (ADS)

    Gassmann, Matthias; Olsson, Oliver; Payraudeau, Sylvain; Imfeld, Gwenaël; Kümmerer, Klaus

    2014-05-01

    Pesticides residues are often found in storm-water runoff in agricultural areas. There are several pathways along which pesticides may be transported from their application point towards the river. Although the primary target of pesticide application is the agricultural area, wind drift transports pesticide droplets to non-target areas. Furthermore, miss-operation of application machines results in the deposition of pesticides at filter strips or roads from where they can be washed off. Therefore, it may be difficult to identify the origin of pesticides in storm-water runoff. However, management of water quality requires that critical source areas are clearly delineated in order to effectively reduce water pollution. In the Rouffach catchment, a 42.7 ha vineyard catchment in France, Glyphosate and its transformation product AMPA occurred frequently and in high concentrations in runoff water during rainfall-runoff events in 2008. In order to identify the source areas of Glyphosate residue pollution and its mobilization, we used here a combination of sampling data analysis techniques and distributed pollutant transfer modelling. Available sampling data allowed for an analysis by Normalized Cumulative Loads (NCL) at a high temporal resolution (10 min). The results imply that pollutant mobilization took place mainly at the beginning of an event. This First Flush suggests a wash off of substances from impervious surfaces such as roads. This assumption was confirmed by local hydrological knowledge about infiltration rates in the vineyard, which were not exceeded by rainfall intensities in most considered events. Additionally, the distributed process-based reactive transport model ZIN-AgriTra was used as a learning tool to evaluate the pesticide mobilization and export processes. The hydrological model was successfully calibrated and validated for long high-resolution time series of discharge data. Pesticide export modelling focused on the first rainfall-runoff event

  18. Positive AMPA receptor modulation rapidly stimulates BDNF release and increases dendritic mRNA translation.

    PubMed

    Jourdi, Hussam; Hsu, Yu-Tien; Zhou, Miou; Qin, Qingyu; Bi, Xiaoning; Baudry, Michel

    2009-07-08

    Brain-derived neurotrophic factor (BDNF) stimulates local dendritic mRNA translation and is involved in formation and consolidation of memory. 2H,3H,6aH-pyrrolidino[2'',1''-3',2']1,3-oxazino[6',5'-5,4]-benzo[e]1,4-dioxan-10-one (CX614), one of the best-studied positive AMPA receptor modulators (also known as ampakines), increases BDNF mRNA and protein and facilitates long-term potentiation (LTP) induction. Several other ampakines also improve performance in various behavioral and learning tasks. Since local dendritic protein synthesis has been implicated in LTP stabilization and in memory consolidation, this study investigated whether CX614 could influence synaptic plasticity by upregulating dendritic protein translation. CX614 treatment of primary neuronal cultures and acute hippocampal slices rapidly activated the translation machinery and increased local dendritic protein synthesis. CX614-induced activation of translation was blocked by K252a [(9S,10R,12R)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester], CNQX, APV, and TTX, and was inhibited in the presence of an extracellular BDNF scavenger, TrkB-Fc. The acute effect of CX614 on translation was mediated by increased BDNF release as demonstrated with a BDNF scavenging assay using TrkB-Fc during CX614 treatment of cultured primary neurons and was blocked by nifedipine, ryanodine, and lack of extracellular Ca(2+) in acute hippocampal slices. Finally, CX614, like BDNF, rapidly increased dendritic translation of an exogenous translation reporter. Together, our results demonstrate that positive modulation of AMPA receptors rapidly stimulates dendritic translation, an effect mediated by BDNF secretion and TrkB receptor activation. They also suggest that increased BDNF secretion and stimulation of local protein synthesis contribute to the effects of ampakines on synaptic plasticity.

  19. Involvement of AMPA receptor phosphorylation in antidepressant actions with special reference to tianeptine.

    PubMed

    Svenningsson, Per; Bateup, Helen; Qi, Hongshi; Takamiya, Kogo; Huganir, Richard L; Spedding, Michael; Roth, Bryan L; McEwen, Bruce S; Greengard, Paul

    2007-12-01

    Depression is associated with abnormal neuronal plasticity. AMPA receptors mediate transmission and plasticity at excitatory synapses in a manner which is positively regulated by phosphorylation at Ser831-GluR1, a CaMKII/PKC site, and Ser845-GluR1, a PKA site. Treatment with the selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitor fluoxetine increases P-Ser845-GluR1 but not P-Ser831-GluR1. Here, it was found that treatment with another antidepressant, tianeptine, increased P-Ser831-GluR1 in the frontal cortex and the CA3 region of hippocampus and P-Ser845-GluR1 in the CA3 region of hippocampus. A receptorome profile detected no affinity for tianeptine at any monaminergic receptors or transporters, confirming an atypical profile for this compound. Behavioural analyses showed that mice bearing point mutations at both Ser831- and Ser845-GluR1, treated with saline, exhibited increased latency to enter the centre of an open field and increased immobility in the tail-suspension test compared to their wild-type counterparts. Chronic tianeptine treatment increased open-field locomotion and reduced immobility in wild-type mice but not in phosphomutant GluR1 mice. P-Ser133-CREB was reduced in the CA3 region of hippocampus in phosphomutant mice, and tianeptine decreased P-Ser133-CREB in this region in wild-type, but not in phosphomutant, mice. Tianeptine increased P-Ser133-CREB in the CA1 region in wild-type mice but not in phosphomutant GluR1 mice. There were higher basal P-Ser133-CREB and c-fos levels in frontal and cingulate cortex in phosphomutant GluR1 mice; these changes in level were counteracted by tianeptine in a GluR1-independent manner. Using phosphorylation assays and phosphomutant GluR1 mice, this study provides evidence that AMPA receptor phosphorylation mediates certain explorative and antidepressant-like actions under basal conditions and following tianeptine treatment.

  20. DRUG FOCUS: S 18986: A positive allosteric modulator of AMPA-type glutamate receptors pharmacological profile of a novel cognitive enhancer.

    PubMed

    Bernard, Katy; Danober, Laurence; Thomas, Jean-Yves; Lebrun, Cécile; Muñoz, Carmen; Cordi, Alex; Desos, Patrice; Lestage, Pierre; Morain, Philippe

    2010-10-01

    Alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) type glutamate receptors are critical for synaptic plasticity and induction of long-term potentiation (LTP), considered as one of the synaptic mechanisms underlying learning and memory. Positive allosteric modulators of AMPA receptors could provide a therapeutic approach to the treatment of cognitive disorders resulting from aging and/or neurodegenerative diseases, such as Alzheimer disease (AD). Several AMPA potentiators have been described in the last decade, but for the moment their clinical efficacy has not been demonstrated due to the complexity of the target, AMPA receptors, and the difficulty in studying cognition in animals and humans. A better understanding of the mechanism of action of this type of drug remains an important issue, if knowledge of these compounds is to be increased and if this novel therapeutic approach is to be an interesting research area. Among the AMPA potentiators, S 18986 is emerging as a new selective positive allosteric modulator of AMPA-type glutamate receptors. S 18986, as with other positive AMPA receptor modulators, increased induction and maintenance of LTP in the hippocampus as well as the expression of brain-derived neurotrophic factor (BDNF) both in vitro and in vivo. Its cognitive-enhancing properties have been demonstrated in various behavioral models (procedural, spatial, "episodic," working, and relational/declarative memory) in young-adult and aged rodents. It is interesting to note that memory-enhancing effects appeared more robust in middle-aged animals compared with aged ones and in "episodic" and spatial memory tasks. From these results, S 18986 is expected to treat memory deficits associated with early cerebral aging and neurological diseases in elderly people.

  1. Neuroprotective effect of Chuk-Me-Sun-Dan on NMDA- and AMPA-evoked nitric oxide synthase activity in mouse brain.

    PubMed

    Koo, Byung-Soo; Choi, Eun-Gyu; Park, Jae-Bok; Cho, Chang-Ho; Chung, Kang-Hyun; Kim, Cheorl-Ho

    2005-01-01

    Chukmesundan (CMSD) is composed of 8 medicinal herbs including Panex ginseng C.A. MEYER, Atractylodes macrocephala KOID, Poria cocos WOLF, Pinellia ternata BREIT, Brassica alba BOISS, Aconitum carmichaeli DEBX, Cynanchum atratum BGE, and Cuscuta chinensis LAM and used for the treatment of various symptoms accompanying hypertension and cerebrovascular disorders. This study was carried out to examine the effects of CMSD on N-methyl-D-aspartate (NMDA)-evoked, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-evoked nitric oxide synthase (NOS) activity in mouse brain. In adult forebrain, CMSD influences neuronal maintenance and is neuroprotective in several injury models through mechanisms that are incompletely understood. Interaction is observed between CMSD and nitric oxide (NO). Because NO affects both neural plasticity and degeneration, we hypothesized that CMSD might rapidly modulate NO production. Using in vivo microdialysis we measured conversion of L-[14C] arginine to L-[14C] citrulline as an accurate reflection of NOS activity in adult mouse hippocampus. CMSD significantly reduced NOS activities to 62% of basal levels within 2 days of onset of delivery and maintained NOS activity at less than 45% of baseline throughout 3 days of delivery. These effects did not occur with control (distilled water) and were not mediated by effect of CMSD on glutamate levels. In addition, simultaneous delivery of CMSD treatment prevented significant increases in NOS activity triggered by the glutamate receptor agonists NMDA and AMPA. Rapid suppression by CMSD of basal and glutamate-stimulated NOS activity may regulate neuromodulatory functions of NO or protect neurons from NO toxicity and suggests a novel mechanism for rapidly mediating functions of CMSD. It is shown that NMDA receptor stimulation leads to activation of p21ras (Ras) through generation of NO via neuronal NOS. The competitive NOS inhibitor, L-nitroarginine methyl ester, and CMSD prevents Ras

  2. Developmental origin dictates interneuron AMPA and NMDA receptor subunit composition and plasticity.

    PubMed

    Matta, Jose A; Pelkey, Kenneth A; Craig, Michael T; Chittajallu, Ramesh; Jeffries, Brian W; McBain, Chris J

    2013-08-01

    Disrupted excitatory synapse maturation in GABAergic interneurons may promote neuropsychiatric disorders such as schizophrenia. However, establishing developmental programs for nascent synapses in GABAergic cells is confounded by their sparsity, heterogeneity and late acquisition of subtype-defining characteristics. We investigated synaptic development in mouse interneurons targeting cells by lineage from medial ganglionic eminence (MGE) or caudal ganglionic eminence (CGE) progenitors. MGE-derived interneuron synapses were dominated by GluA2-lacking AMPA-type glutamate receptors (AMPARs), with little contribution from NMDA-type receptors (NMDARs) throughout development. In contrast, CGE-derived cell synapses had large NMDAR components and used GluA2-containing AMPARs. In neonates, both MGE- and CGE-derived interneurons expressed primarily GluN2B subunit-containing NMDARs, which most CGE-derived interneurons retained into adulthood. However, MGE-derived interneuron NMDARs underwent a GluN2B-to-GluN2A switch that could be triggered acutely with repetitive synaptic activity. Our findings establish ganglionic eminence-dependent rules for early synaptic integration programs of distinct interneuron cohorts, including parvalbumin- and cholecystokinin-expressing basket cells.

  3. The Fate and Transport of Glyphosate and AMPA into Surface Waters of Agricultural Watersheds

    NASA Astrophysics Data System (ADS)

    Coupe, R.; Kalkhoff, S.; Capel, P.; Gregoire, C.

    2010-12-01

    Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used widely throughout the world in the production of many crops, but is particularly heavily used on crops which are genetically modified to be glyphosate tolerant: predominately soybeans, corn, potatoes, and cotton. Glyphosate is used extensively in almost all agricultural areas of the United States, and annual application has increased from less than 10,000 Mg in 1992 to more than 80,000 Mg in 2007. The greatest areal use is in the Midwest where glyphosate is applied on genetically modified corn and soybeans. Although use is increasing, the characterization of glyphosate transport on the watershed scale is lacking. Glyphosate, and its degradate AMPA [aminomethylphosphoric acid], was frequently detected in the surface waters of four agricultural watersheds. The load as a percent of use of glyphosate ranged from 0.009 to 0.86 percent and can be related to three factors: source strength, hydrology, and flowpath. Glyphosate use within a watershed results in some occurrence in surface water at the part per billion level; however watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff, and a flowpath that does not include transport through the soil.

  4. Distinct Structural Pathways Coordinate the Activation of AMPA Receptor-Auxiliary Subunit Complexes

    PubMed Central

    Dawe, G. Brent; Musgaard, Maria; Aurousseau, Mark R.P.; Nayeem, Naushaba; Green, Tim; Biggin, Philip C.; Bowie, Derek

    2016-01-01

    Summary Neurotransmitter-gated ion channels adopt different gating modes to fine-tune signaling at central synapses. At glutamatergic synapses, high and low activity of AMPA receptors (AMPARs) is observed when pore-forming subunits coassemble with or without auxiliary subunits, respectively. Whether a common structural pathway accounts for these different gating modes is unclear. Here, we identify two structural motifs that determine the time course of AMPAR channel activation. A network of electrostatic interactions at the apex of the AMPAR ligand-binding domain (LBD) is essential for gating by pore-forming subunits, whereas a conserved motif on the lower, D2 lobe of the LBD prolongs channel activity when auxiliary subunits are present. Accordingly, channel activity is almost entirely abolished by elimination of the electrostatic network but restored via auxiliary protein interactions at the D2 lobe. In summary, we propose that activation of native AMPAR complexes is coordinated by distinct structural pathways, favored by the association/dissociation of auxiliary subunits. PMID:26924438

  5. Role of TARP interaction in S-SCAM-mediated regulation of AMPA receptors.

    PubMed

    Danielson, Eric; Metallo, Jacob; Lee, Sang H

    2012-01-01

    Scaffolding proteins are involved in the incorporation, anchoring, maintenance, and removal of AMPA receptors (AMPARs) at synapses, either through a direct interaction with AMPARs or via indirect association through auxiliary subunits of transmembrane AMPAR regulatory proteins (TARPs). Synaptic scaffolding molecule (S-SCAM) is a newly characterized member of the scaffolding proteins critical for the regulation and maintenance of AMPAR levels at synapses, and directly binds to TARPs through a PDZ interaction. However, the functional significance of S-SCAM-TARP interaction in the regulation of AMPARs has not been tested. Here we show that overexpression of the C-terminal peptide of TARP-γ2 fused to EGFP abolished the S-SCAM-mediated enhancement of surface GluA2 expression. Conversely, the deletion of the PDZ-5 domain of S-SCAM that binds TARPs greatly attenuated the S-SCAM-induced increase of surface GluA2 expression. In contrast, the deletion of the guanylate kinase domain of S-SCAM did not show a significant effect on the regulation of AMPARs. Together, these results suggest that S-SCAM is regulating AMPARs through TARPs.

  6. The Sorting Receptor SorCS1 Regulates Trafficking of Neurexin and AMPA Receptors

    PubMed Central

    Savas, Jeffrey N.; Ribeiro, Luís F.; Wierda, Keimpe D.; Wright, Rebecca; DeNardo, Laura A.; Rice, Heather C.; Chamma, Ingrid; Wang, Yi-Zhi; Zemla, Roland; Lavallée-Adam, Mathieu; Vennekens, Kristel M.; O'Sullivan, Matthew L.; Antonios, Joseph K.; Hall, Elizabeth A.; Thoumine, Olivier; Attie, Alan D.; Ghosh, Anirvan; Yates, John R.; de Wit, Joris

    2015-01-01

    The formation, function, and plasticity of synapses require dynamic changes in synaptic receptor composition. Here we identify the sorting receptor SorCS1 as a key regulator of synaptic receptor trafficking. Four independent proteomic analyses identify the synaptic adhesion molecule neurexin and the AMPA glutamate receptor (AMPAR) as major proteins sorted by SorCS1. SorCS1 localizes to early and recycling endosomes and regulates neurexin and AMPAR surface trafficking. Surface proteome analysis of SorCS1-deficient neurons shows decreased surface levels of these, and additional, receptors. Quantitative in vivo analysis of SorCS1 knockout synaptic proteomes identifies SorCS1 as a global trafficking regulator and reveals decreased levels of receptors regulating adhesion and neurotransmission, including neurexins and AMPARs. Consequently, glutamatergic transmission at SorCS1–deficient synapses is reduced due to impaired AMPAR surface expression. SORCS1 mutations have been associated with autism and Alzheimer's disease, suggesting that perturbed receptor trafficking contributes to defects in synaptic composition and function underlying synaptopathies. PMID:26291160

  7. Phosphorylation of AMPA receptors is required for sensory deprivation-induced homeostatic synaptic plasticity.

    PubMed

    Goel, Anubhuti; Xu, Linda W; Snyder, Kevin P; Song, Lihua; Goenaga-Vazquez, Yamila; Megill, Andrea; Takamiya, Kogo; Huganir, Richard L; Lee, Hey-Kyoung

    2011-03-31

    Sensory experience, and the lack thereof, can alter the function of excitatory synapses in the primary sensory cortices. Recent evidence suggests that changes in sensory experience can regulate the synaptic level of Ca(2+)-permeable AMPA receptors (CP-AMPARs). However, the molecular mechanisms underlying such a process have not been determined. We found that binocular visual deprivation, which is a well-established in vivo model to produce multiplicative synaptic scaling in visual cortex of juvenile rodents, is accompanied by an increase in the phosphorylation of AMPAR GluR1 (or GluA1) subunit at the serine 845 (S845) site and the appearance of CP-AMPARs at synapses. To address the role of GluR1-S845 in visual deprivation-induced homeostatic synaptic plasticity, we used mice lacking key phosphorylation sites on the GluR1 subunit. We found that mice specifically lacking the GluR1-S845 site (GluR1-S845A mutants), which is a substrate of cAMP-dependent kinase (PKA), show abnormal basal excitatory synaptic transmission and lack visual deprivation-induced homeostatic synaptic plasticity. We also found evidence that increasing GluR1-S845 phosphorylation alone is not sufficient to produce normal multiplicative synaptic scaling. Our study provides concrete evidence that a GluR1 dependent mechanism, especially S845 phosphorylation, is a necessary pre-requisite step for in vivo homeostatic synaptic plasticity.

  8. X-ray structure, symmetry and mechanism of an AMPA-subtype glutamate receptor

    SciTech Connect

    Sobolevsky, Alexander I.; Rosconi, Michael P.; Gouaux, Eric

    2010-02-02

    Ionotropic glutamate receptors mediate most excitatory neurotransmission in the central nervous system and function by opening a transmembrane ion channel upon binding of glutamate. Despite their crucial role in neurobiology, the architecture and atomic structure of an intact ionotropic glutamate receptor are unknown. Here we report the crystal structure of the {alpha}-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-sensitive, homotetrameric, rat GluA2 receptor at 3.6 {angstrom} resolution in complex with a competitive antagonist. The receptor harbours an overall axis of two-fold symmetry with the extracellular domains organized as pairs of local dimers and with the ion channel domain exhibiting four-fold symmetry. A symmetry mismatch between the extracellular and ion channel domains is mediated by two pairs of conformationally distinct subunits, A/C and B/D. Therefore, the stereochemical manner in which the A/C subunits are coupled to the ion channel gate is different from the B/D subunits. Guided by the GluA2 structure and site-directed cysteine mutagenesis, we suggest that GluN1 and GluN2A NMDA (N-methyl-D-aspartate) receptors have a similar architecture, with subunits arranged in a 1-2-1-2 pattern. We exploit the GluA2 structure to develop mechanisms of ion channel activation, desensitization and inhibition by non-competitive antagonists and pore blockers.

  9. Synaptic transmission and plasticity require AMPA receptor anchoring via its N-terminal domain

    PubMed Central

    Watson, Jake F; Ho, Hinze; Greger, Ingo H

    2017-01-01

    AMPA-type glutamate receptors (AMPARs) mediate fast excitatory neurotransmission and are selectively recruited during activity-dependent plasticity to increase synaptic strength. A prerequisite for faithful signal transmission is the positioning and clustering of AMPARs at postsynaptic sites. The mechanisms underlying this positioning have largely been ascribed to the receptor cytoplasmic C-termini and to AMPAR-associated auxiliary subunits, both interacting with the postsynaptic scaffold. Here, using mouse organotypic hippocampal slices, we show that the extracellular AMPAR N-terminal domain (NTD), which projects midway into the synaptic cleft, plays a fundamental role in this process. This highly sequence-diverse domain mediates synaptic anchoring in a subunit-selective manner. Receptors lacking the NTD exhibit increased mobility in synapses, depress synaptic transmission and are unable to sustain long-term potentiation (LTP). Thus, synaptic transmission and the expression of LTP are dependent upon an AMPAR anchoring mechanism that is driven by the NTD. DOI: http://dx.doi.org/10.7554/eLife.23024.001 PMID:28290985

  10. AMPA glutamate receptors are required for sensory-organ formation and morphogenesis in the basal chordate.

    PubMed

    Hirai, Shinobu; Hotta, Kohji; Kubo, Yoshihiro; Nishino, Atsuo; Okabe, Shigeo; Okamura, Yasushi; Okado, Haruo

    2017-04-11

    AMPA-type glutamate receptors (GluAs) mediate fast excitatory transmission in the vertebrate central nervous system (CNS), and their function has been extensively studied in the mature mammalian brain. However, GluA expression begins very early in developing embryos, suggesting that they may also have unidentified developmental roles. Here, we identify developmental roles for GluAs in the ascidian Ciona intestinalis Mammals express Ca(2+)-permeable GluAs (Ca-P GluAs) and Ca(2+)-impermeable GluAs (Ca-I GluAs) by combining subunits derived from four genes. In contrast, ascidians have a single gluA gene. Taking advantage of the simple genomic GluA organization in ascidians, we knocked down (KD) GluAs in Ciona and observed severe impairments in formation of the ocellus, a photoreceptive organ used during the swimming stage, and in resorption of the tail and body axis rotation during metamorphosis to the adult stage. These defects could be rescued by injection of KD-resistant GluAs. GluA KD phenotypes could also be reproduced by expressing a GluA mutant that dominantly inhibits glutamate-evoked currents. These results suggest that, in addition to their role in synaptic communication in mature animals, GluAs also have critical developmental functions.

  11. Cysteine 893 is a target of regulatory thiol modifications of GluA1 AMPA receptors

    PubMed Central

    von Ossowski, Lotta; Li, Li-Li; Möykkynen, Tommi; Coleman, Sarah K.; Courtney, Michael J.

    2017-01-01

    Recent studies indicate that glutamatergic signaling involves, and is regulated by, thiol modifying and redox-active compounds. In this study, we examined the role of a reactive cysteine residue, Cys-893, in the cytosolic C-terminal tail of GluA1 AMPA receptor as a potential regulatory target. Elimination of the thiol function by substitution of serine for Cys-893 led to increased steady-state expression level and strongly reduced interaction with SAP97, a major cytosolic interaction partner of GluA1 C-terminus. Moreover, we found that of the three cysteine residues in GluA1 C-terminal tail, Cys-893 is the predominant target for S-nitrosylation induced by exogenous nitric oxide donors in cultured cells and lysates. Co-precipitation experiments provided evidence for native association of SAP97 with neuronal nitric oxide synthase (nNOS) and for the potential coupling of Ca2+-permeable GluA1 receptors with nNOS via SAP97. Our results show that Cys-893 can serve as a molecular target for regulatory thiol modifications of GluA1 receptors, including the effects of nitric oxide. PMID:28152104

  12. Enhanced AMPA receptor function promotes cerebellar long-term depression rather than potentiation

    PubMed Central

    van Beugen, Boeke J.; Qiao, Xin; Simmons, Dana H.; De Zeeuw, Chris I.

    2014-01-01

    Ampakines are allosteric modulators of AMPA receptors that facilitate hippocampal long-term potentiation (LTP) and learning, and have been considered for the treatment of cognition and memory deficits. Here, we show that the ampakine CX546 raises the amplitude and slows the decay time of excitatory postsynaptic currents (EPSCs) at cerebellar parallel fiber (PF) to Purkinje cell synapses, thus resembling CX546 effects described at hippocampal synapses. Using the fluorescent calcium indicator dye Oregon Green BAPTA-2 and an ultra-high-speed CCD camera, we also monitored calcium transients in Purkinje cell dendrites. In the presence of CX546 in the bath, PF-evoked calcium transients were enhanced and prolonged, suggesting that CX546 not only enhances synaptic transmission, but also boosts dendritic calcium signaling at cerebellar synapses. In contrast to previous observations in the hippocampus, however, CX546 applied during cerebellar recordings facilitates long-term depression (LTD) rather than LTP at PF synapses. These findings show that ampakines selectively modify the LTP–LTD balance depending on the brain area and type of synapse, and may provide tools for the targeted regulation of synaptic memories. PMID:25403454

  13. Enhanced AMPA receptor function promotes cerebellar long-term depression rather than potentiation.

    PubMed

    van Beugen, Boeke J; Qiao, Xin; Simmons, Dana H; De Zeeuw, Chris I; Hansel, Christian

    2014-12-01

    Ampakines are allosteric modulators of AMPA receptors that facilitate hippocampal long-term potentiation (LTP) and learning, and have been considered for the treatment of cognition and memory deficits. Here, we show that the ampakine CX546 raises the amplitude and slows the decay time of excitatory postsynaptic currents (EPSCs) at cerebellar parallel fiber (PF) to Purkinje cell synapses, thus resembling CX546 effects described at hippocampal synapses. Using the fluorescent calcium indicator dye Oregon Green BAPTA-2 and an ultra-high-speed CCD camera, we also monitored calcium transients in Purkinje cell dendrites. In the presence of CX546 in the bath, PF-evoked calcium transients were enhanced and prolonged, suggesting that CX546 not only enhances synaptic transmission, but also boosts dendritic calcium signaling at cerebellar synapses. In contrast to previous observations in the hippocampus, however, CX546 applied during cerebellar recordings facilitates long-term depression (LTD) rather than LTP at PF synapses. These findings show that ampakines selectively modify the LTP-LTD balance depending on the brain area and type of synapse, and may provide tools for the targeted regulation of synaptic memories.

  14. The balance of NMDA- and AMPA/kainate receptor-mediated activity in normal adult goldfish and during optic nerve regeneration.

    PubMed

    Taylor, Andrew L; Rodger, Jennifer; Stirling, R Victoria; Beazley, Lyn D; Dunlop, Sarah A

    2005-10-01

    Retinotectal topography is established during development and relies on the sequential recruitment of glutamate receptors within postsynaptic tectal cells. NMDA receptors underpin plastic changes at early stages when retinal ganglion cell (RGC) terminal arbors are widespread and topography is coarse; AMPA/kainate receptors mediate fast secure neurotransmission characteristic of mature circuits once topography is refined. Here, we have examined the relative contributions of these receptors to visually evoked activity in normal adult goldfish, in which retinotectal topography is constantly adjusted to compensate for the continual neurogenesis and the addition of new RGC arbors. Furthermore, we examined animals at two stages of optic nerve regeneration. In the first, RGC arbors are widespread and receptive fields large resulting in coarse topography; in the second, RGC arbors are pruned to reduce receptive fields leading to refined topography. Antagonists were applied to the tectum during multiunit recording of postsynaptic responses. Normal goldfish have low levels of NMDA receptor-mediated activity and high levels of AMPA/kainate. When coarse topography has been restored, NMDA receptor-mediated activity is increased and that of AMPA/kainate decreased. Once topography has been refined, the balance of NMDA and AMPA/kainate receptor-mediated activity returns to normal. The data suggest that glutamatergic neurotransmission in normal adult goldfish is dual with NMDA receptors fine-tuning topography and AMPA receptors allowing stable synaptic function. Furthermore, the normal operation of both receptors allows a response to injury in which the balance can be transiently reversed to restore topography and vision.

  15. Modulator effects of interleukin-1beta and tumor necrosis factor-alpha on AMPA-induced excitotoxicity in mouse organotypic hippocampal slice cultures.

    PubMed

    Bernardino, Liliana; Xapelli, Sara; Silva, Ana P; Jakobsen, Birthe; Poulsen, Frantz R; Oliveira, Catarina R; Vezzani, Annamaria; Malva, João O; Zimmer, Jens

    2005-07-20

    The inflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha (TNF-alpha) have been identified as mediators of several forms of neurodegeneration in the brain. However, they can produce either deleterious or beneficial effects on neuronal function. We investigated the effects of these cytokines on neuronal death caused by exposure of mouse organotypic hippocampal slice cultures to toxic concentrations of AMPA. Either potentiation of excitotoxicity or neuroprotection was observed, depending on the concentration of the cytokines and the timing of exposure. A relatively high concentration of mouse recombinant TNF-alpha (10 ng/ml) enhanced excitotoxicity when the cultures were simultaneously exposed to AMPA and to this cytokine. Decreasing the concentration of TNF-alpha to 1 ng/ml resulted in neuroprotection against AMPA-induced neuronal death independently on the application protocol. By using TNF-alpha receptor (TNFR) knock-out mice, we demonstrated that the potentiation of AMPA-induced toxicity by TNF-alpha involves TNF receptor-1, whereas the neuroprotective effect is mediated by TNF receptor-2. AMPA exposure was associated with activation and proliferation of microglia as assessed by macrophage antigen-1 and bromodeoxyuridine immunohistochemistry, suggesting a functional recruitment of cytokine-producing cells at sites of neurodegeneration. Together, these findings are relevant for understanding the role of proinflammatory cytokines and microglia activation in acute and chronic excitotoxic conditions.

  16. Peripheral inflamation-induced increase of AMPA-mediated currents and Ca2+ transients in the presence of cyclothiazide in the rat substantia gelatinosa neurons.

    PubMed

    Voitenko, N; Gerber, G; Youn, D; Randic, M

    2004-05-01

    This study employing a rodent model of acute pain investigated the influence of carrageenan-induced inflammation on the ability of S-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor activation to induce membrane currents and rises in cytosolic free calcium concentration ([Ca2+]i) in the rat substantia gelatinosa (SG) neurons using simultaneous whole-cell patch-clamp recording and fura-2 calcium imaging in spinal cord slices of L4-L5 segments. The novel finding of this study is that carrageenan-induced inflammation, in the presence of cyclothiazide, an inhibitor of AMPA receptor desensitization, produces a sustained facilitation of the AMPA-mediated membrane current and rises in [Ca2+]i in both the soma and proximal dendrites of SG neurons recorded on the injected side 3 h after the induction of inflammation. These results suggest that in carrageenan-inflamed rats AMPA receptors undergo some alterations that influence AMPA receptors desensitization and/or sensitivity to cyclothiazide.

  17. The role of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in depression: central mediators of pathophysiology and antidepressant activity?

    PubMed

    Freudenberg, Florian; Celikel, Tansu; Reif, Andreas

    2015-05-01

    Depression is a major psychiatric disorder affecting more than 120 million people worldwide every year. Changes in monoaminergic transmitter release are suggested to take part in the pathophysiology of depression. However, more recent experimental evidence suggests that glutamatergic mechanisms might play a more central role in the development of this disorder. The importance of the glutamatergic system in depression was particularly highlighted by the discovery that N-methyl-D-aspartate (NMDA) receptor antagonists (particularly ketamine) exert relatively long-lasting antidepressant like effects with rapid onset. Importantly, the antidepressant-like effects of NMDA receptor antagonists, but also other antidepressants (both classical and novel), require activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Additionally, expression of AMPA receptors is altered in patients with depression. Moreover, preclinical evidence supports an important involvement of AMPA receptor-dependent signaling and plasticity in the pathophysiology and treatment of depression. Here we summarize work published on the involvement of AMPA receptors in depression and discuss a possible central role for AMPA receptors in the pathophysiology, course and treatment of depression.

  18. Plexin-A4-dependent retrograde semaphorin 3A signalling regulates the dendritic localization of GluA2-containing AMPA receptors.

    PubMed

    Yamashita, Naoya; Usui, Hiroshi; Nakamura, Fumio; Chen, Sandy; Sasaki, Yukio; Hida, Tomonobu; Suto, Fumikazu; Taniguchi, Masahiko; Takei, Kohtaro; Goshima, Yoshio

    2014-03-06

    The dendritic targeting of neurotransmitter receptors is vital for dendritic development and function. However, how such localization is established remains unclear. Here we show that semaphorin 3A (Sema3A) signalling at the axonal growth cone is propagated towards the cell body by retrograde axonal transport and drives AMPA receptor GluA2 to the distal dendrites, which regulates dendritic development. Sema3A enhances glutamate receptor interacting protein 1-dependent localization of GluA2 in dendrites, which is blocked by knockdown of cytoplasmic dynein heavy chain. PlexinA (PlexA), a receptor component for Sema3A, interacts with GluA2 at the immunoglobulin-like Plexin-transcription-factor domain (PlexA-IPT) in somatodendritic regions. Overexpression of PlexA-IPT suppresses dendritic localization of GluA2 and induces aproximal bifurcation phenotype in the apical dendrites of CA1 hippocampal neurons. Thus, we propose a control mechanism by which retrograde Sema3A signalling regulates the glutamate receptor localization through trafficking of cis-interacting PlexA with GluA2 along dendrites.

  19. Channel-lining residues of the AMPA receptor M2 segment: structural environment of the Q/R site and identification of the selectivity filter.

    PubMed

    Kuner, T; Beck, C; Sakmann, B; Seeburg, P H

    2001-06-15

    In AMPA receptor channels, a single amino acid residue (Q/R site) of the M2 segment controls permeation of calcium ions, single-channel conductance, blockade by intracellular polyamines, and permeation of anions. The structural environment of the Q/R site and its positioning with regard to a narrow constriction were probed with the accessibility of substituted cysteines to positively and negatively charged methanethiosulfonate reagents, applied from the extracellular and cytoplasmic sides of the channel. The accessibility patterns confirm that the M2 segment forms a pore loop with the Q/R site positioned at the tip of the loop (position 0) facing the extracellular vestibule. Cytoplasmically accessible residues on the N- and C-terminal sides of position 0 form the ascending alpha-helical (-8 to -1) and descending random coil (+1 to +6) components of the loop, respectively. Substitution of a glycine residue at position +2 with alanine strongly decreased the permeability of organic cations, indicating that position +2 contributes to the narrow constriction. The anionic 2-sulfonatoethyl-methanethiosufonate reacted with a cysteine at position 0 only from the external side and with cysteines at positions +1 to +4 only from the cytoplasmic side. These results suggest that charge selectivity occurs external to the constriction (+2) and possibly involves interactions of ions with the negative electrostatic potential created by the dipole of the alpha-helix formed by the ascending limb of the loop.

  20. Inhibition of Ca2+-activated large-conductance K+ channel activity alters synaptic AMPA receptor phenotype in mouse cerebellar stellate cells.

    PubMed

    Liu, Yu; Savtchouk, Iaroslav; Acharjee, Shoana; Liu, Siqiong June

    2011-07-01

    Many fast-spiking inhibitory interneurons, including cerebellar stellate cells, fire brief action potentials and express α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors (AMPAR) that are permeable to Ca(2+) and do not contain the GluR2 subunit. In a recent study, we found that increasing action potential duration promotes GluR2 gene transcription in stellate cells. We have now tested the prediction that activation of potassium channels that control the duration of action potentials can suppress the expression of GluR2-containing AMPARs at stellate cell synapses. We find that large-conductance Ca(2+)-activated potassium (BK) channels mediate a large proportion of the depolarization-evoked noninactivating potassium current in stellate cells. Pharmacological blockade of BK channels prolonged the action potential duration in postsynaptic stellate cells and altered synaptic AMPAR subtype from GluR2-lacking to GluR2-containing Ca(2+)-impermeable AMPARs. An L-type channel blocker abolished an increase in Ca(2+) entry that was associated with spike broadening and also prevented the BK channel blocker-induced switch in AMPAR phenotype. Thus blocking BK potassium channels prolongs the action potential duration and increases the expression of GluR2-containing receptors at the synapse by enhancing Ca(2+) entry in cerebellar stellate cells.

  1. Inhibition of Ca2+-activated large-conductance K+ channel activity alters synaptic AMPA receptor phenotype in mouse cerebellar stellate cells

    PubMed Central

    Liu, Yu; Savtchouk, Iaroslav; Acharjee, Shoana

    2011-01-01

    Many fast-spiking inhibitory interneurons, including cerebellar stellate cells, fire brief action potentials and express α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)-type glutamate receptors (AMPAR) that are permeable to Ca2+ and do not contain the GluR2 subunit. In a recent study, we found that increasing action potential duration promotes GluR2 gene transcription in stellate cells. We have now tested the prediction that activation of potassium channels that control the duration of action potentials can suppress the expression of GluR2-containing AMPARs at stellate cell synapses. We find that large-conductance Ca2+-activated potassium (BK) channels mediate a large proportion of the depolarization-evoked noninactivating potassium current in stellate cells. Pharmacological blockade of BK channels prolonged the action potential duration in postsynaptic stellate cells and altered synaptic AMPAR subtype from GluR2-lacking to GluR2-containing Ca2+-impermeable AMPARs. An L-type channel blocker abolished an increase in Ca2+ entry that was associated with spike broadening and also prevented the BK channel blocker-induced switch in AMPAR phenotype. Thus blocking BK potassium channels prolongs the action potential duration and increases the expression of GluR2-containing receptors at the synapse by enhancing Ca2+ entry in cerebellar stellate cells. PMID:21562198

  2. Modulation of agonist binding to AMPA receptors by 1-(1,4-benzodioxan-6-ylcarbonyl)piperidine (CX546): differential effects across brain regions and GluA1-4/transmembrane AMPA receptor regulatory protein combinations.

    PubMed

    Montgomery, Kyle E; Kessler, Markus; Arai, Amy C

    2009-12-01

    Ampakines are cognitive enhancers that potentiate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor currents and synaptic responses by slowing receptor deactivation. Their efficacy varies greatly between classes of neurons and brain regions, but the factor responsible for this effect remains unclear. Ampakines also increase agonist affinity in binding tests in ways that are related to their physiological action. We therefore examined 1) whether ampakine effects on agonist binding vary across brain regions and 2) whether they differ across receptor subunits expressed alone and together with transmembrane AMPA receptor regulatory proteins (TARPs), which associate with AMPA receptors in the brain. We found that the maximal increase in agonist binding (E(max)) caused by the prototypical ampakine 1-(1,4-benzodioxan-6-ylcarbonyl)piperidine (CX546) differs significantly between brain regions, with effects in hippocampus and cerebellum being nearly three times larger than that in thalamus, brainstem, and striatum, and cortex being intermediate. These differences can be explained at least in part by regional variations in receptor subunit and TARP expression because combinations prevalent in hippocampus (GluA2 with TARPs gamma3 and gamma8) exhibited E(max) values nearly twice those of combinations abundant in thalamus (GluA4 with gamma2 or gamma4). TARPs seem to be critical because GluA2 and GluA4 alone had comparable E(max) and also because hippocampal and thalamic receptors had similar E(max) after solubilization with Triton X-100, which probably removes associated proteins. Taken together, our data suggest that variations in physiological drug efficacy, such as the 3-fold difference previously seen in recordings from hippocampus versus thalamus, may be explained by region-specific expression of GluA1-4 as well as TARPs.

  3. Work plan for determining the occurrence of glyphosate, its transformation product AMPA, other herbicide compounds, and antibiotics in midwestern United States streams, 2002

    USGS Publications Warehouse

    Battaglin, W.A.; Thurman, E.M.; Kolpin, D.W.; Scribner, E.A.; Sandstrom, M.W.; Kuivila, K.M.

    2003-01-01

    The objective of this study is to determine the distribution of glyphosate and its primary transformation product aminomethylphosphonic acid (AMPA) in midwestern streams during post-application and harvest-season runoff events. Water samples will be collected in 2002 during two post-herbicide-application runoff events and one harvest-season runoff event from 53 sites on streams in the Midwestern United States. All samples will be analyzed at the U.S. Geological Survey Organic Geochemistry Research Laboratory in Lawrence, Kansas, for glyphosate and 20 other herbicides. Samples will also be analyzed for a glyphosate transformation product (AMPA) and 26 other herbicide transformation products, using GC/MS or HPLC/MS. Selected samples will be analyzed for 36 antibiotics or antibiotic transformational products. Results from this study will represent the first broad-scale investigation of glyphosate and AMPA in U.S. water resources.

  4. GABA(A)- and AMPA-like receptors modulate the activity of an identified neuron within the central pattern generator of the pond snail Lymnaea stagnalis.

    PubMed

    Moccia, Francesco; Di Cristo, Carlo; Winlow, William; Di Cosmo, Anna

    2009-03-01

    To examine the neurochemistry underlying the firing of the RPeD1 neuron in the respiratory central pattern generator of the pond snail, Lymnaea stagnalis, we examined electrophysiologically and pharmacologically either "active" or "silent" preparations by intracellular recording and pharmacology. GABA inhibited electrical firing by hyperpolarizing RPeD1, while picrotoxin, an antagonist of GABA(A) receptors, excited silent cells and reversed GABA-induced inhibition. Action potential activity was terminated by 1 mM glutamate (Glu) while silent cells were depolarized by the GluR agonists, AMPA, and NMDA. Kainate exerted a complex triphasic effect on membrane potential. However, only bath application of AMPA desensitized the firing. These data indicate that GABA inhibits RPeD1 via activation of GABA(A) receptors, while Glu stimulates the neuron by activating AMPA-sensitive GluRs.

  5. Distribution of NMDA and AMPA receptor subunits at thalamo-amygdaloid dendritic spines.

    PubMed

    Radley, Jason J; Farb, Claudia R; He, Yong; Janssen, William G M; Rodrigues, Sarina M; Johnson, Luke R; Hof, Patrick R; LeDoux, Joseph E; Morrison, John H

    2007-02-23

    Synapses onto dendritic spines in the lateral amygdala formed by afferents from the auditory thalamus represent a site of plasticity in Pavlovian fear conditioning. Previous work has demonstrated that thalamic afferents synapse onto LA spines expressing glutamate receptor (GluR) subunits, but the GluR subunit distribution at the synapse and within the cytoplasm has not been characterized. Therefore, we performed a quantitative analysis for alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunits GluR2 and GluR3 and N-methyl-D-aspartate (NMDA) receptor subunits NR1 and NR2B by combining anterograde labeling of thalamo-amygdaloid afferents with postembedding immunoelectron microscopy for the GluRs in adult rats. A high percentage of thalamo-amygdaloid spines was immunoreactive for GluR2 (80%), GluR3 (83%), and NR1 (83%), while a smaller proportion of spines expressed NR2B (59%). To compare across the various subunits, the cytoplasmic to synaptic ratios of GluRs were measured within thalamo-amygdaloid spines. Analyses revealed that the cytoplasmic pool of GluR2 receptors was twice as large compared to the GluR3, NR1, and NR2B subunits. Our data also show that in the adult brain, the NR2B subunit is expressed in the majority of in thalamo-amygdaloid spines and that within these spines, the various GluRs are differentially distributed between synaptic and non-synaptic sites. The prevalence of the NR2B subunit in thalamo-amygdaloid spines provides morphological evidence supporting its role in the fear conditioning circuit while the differential distribution of the GluR subtypes may reflect distinct roles for their involvement in this circuitry and synaptic plasticity.

  6. Stress at learning facilitates memory formation by regulating AMPA receptor trafficking through a glucocorticoid action.

    PubMed

    Conboy, Lisa; Sandi, Carmen

    2010-02-01

    Stress and glucocorticoids (GCs) can facilitate memory formation. However, the molecular mechanisms mediating their effects are largely unknown. Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR) trafficking has been implicated in the changes in synaptic strength at central glutamatergic synapses associated with memory formation. In cell cultures, corticosterone has been shown to condition the synaptic trafficking of the AMPAR GluA2 subunit. In this study, we investigated the involvement of GluA2 trafficking in the facilitation of learning by stress. Using the water maze spatial task involving different stress levels, mice trained under more stressful conditions (water at 22 degrees C) showed better learning and memory, and higher post-training corticosterone levels, than mice trained under lower stress (water at 30 degrees C). Strikingly, this facilitated learning by stress was accompanied by enhanced synaptic expression of GluA2 AMPARs that was not observed in mice trained under less stressful conditions. Interfering with GC actions by injecting the GC synthesis inhibitor, metyrapone, blocked both the memory facilitation and the enhanced GluA2 trafficking induced by stressful learning. Intracerebroventricular infusion of the peptide, pep2m, that blocks GluA2 synaptic trafficking by interfering with the interaction between N-ethylmaleimide-sensitive factor and GluA2, impaired immediate performance at learning as well as long-term memory retrieval, supporting a causal role for GluA2 trafficking in stress-induced facilitation of spatial learning and memory. Evidence for the involvement of the neural cell adhesion molecule N-cadherin in interaction with GluA2 is also provided. These findings underscore a new mechanism whereby stress can improve memory function.

  7. Molecular mechanisms underlying activity-dependent AMPA receptor cycling in retinal ganglion cells

    PubMed Central

    Casimiro, Tanya M.; Nawy, Scott; Carroll, Reed C.

    2013-01-01

    On retinal ganglion cells (RGCs) transmit light encoded information to the brain and receive excitatory input from On cone bipolar cells (CBPs). The synaptic CBP input onto On RGCs is mediated by AMPA-type glutamate receptors (AMPARs) that include both those lacking a GluA2 subunit, and are therefore permeable to Ca2+, and those that possess at least one GluA2 subunit and are Ca2+-impermeable. We have previously demonstrated in electrophysiological studies that periods of low synaptic activity, brought about by housing animals in darkness, enhances the proportion of GluA2-lacking AMPARs at the On CBP-On RGC synapse by mobilizing surface GluA2 containing receptors into a receptor pool that rapidly cycles in and out of the membrane. AMPAR cycling induction by reduced synaptic activity takes several hours. This delay suggests that changes in expression of proteins which regulate AMPAR trafficking may mediate the altered mobility of GluA2 AMPARs in RGCs. In this study, we test the hypothesis that AMPAR trafficking proteins couple synaptic activity to AMPAR cycling in RGCs. Immunocytochemical and biochemical analysis confirmed that darkness decreases surface GluA2 in RGCs and changed the expression levels of three proteins associated with GluA2 trafficking. GRIP was decreased, while PICK1 and Arc were increased. Knockdown of GRIP with siRNA elevated constitutive AMPAR cycling, mimicking effects of reduced synaptic activity, while knockdown of PICK1 and ARC blocked increases in constitutive GluA2 trafficking. Our results support a role for correlated, activity-driven changes in multiple AMPAR trafficking proteins that modulate GluA2 cycling which can in turn affect synaptic AMPAR composition in RGCs. PMID:23911793

  8. Transmembrane AMPA receptor regulatory protein (TARP) dysregulation in anterior cingulate cortex in schizophrenia.

    PubMed

    Drummond, Jana B; Tucholski, Janusz; Haroutunian, Vahram; Meador-Woodruff, James H

    2013-06-01

    The glutamate hypothesis of schizophrenia proposes that abnormal glutamatergic neurotransmission occurs in this illness, and a major contribution may involve dysregulation of the AMPA subtype of ionotropic glutamate receptor (AMPAR). Transmembrane AMPAR regulatory proteins (TARPs) form direct associations with AMPARs to modulate the trafficking and biophysical functions of these receptors, and their dysregulation may alter the localization and activity of AMPARs, thus having a potential role in the pathophysiology of schizophrenia. We performed comparative quantitative real-time PCR and Western blot analysis to measure transcript (schizophrenia, N=25; comparison subjects, N=25) and protein (schizophrenia, N=36; comparison subjects, N=33) expression of TARPs (γ subunits 1-8) in the anterior cingulate cortex (ACC) in schizophrenia and a comparison group. TARP expression was also measured in frontal cortex of rats chronically treated with haloperidol decanoate (28.5mg/kg every three weeks for nine months) to determine the effect of antipsychotic treatment on the expression of these molecules. We found decreased transcript expression of TARP γ-8 in schizophrenia. At the protein level, γ-3 and γ-5 were increased, while γ-4, γ-7 and γ-8 were decreased in schizophrenia. No changes in any of the molecules were noted in the frontal cortex of haloperidol-treated rats. TARPs are abnormally expressed at transcript and protein levels in ACC in schizophrenia, and these changes are likely due to the illness and not to the antipsychotic treatment. Alterations in the expression of TARPs may contribute to the pathophysiology of schizophrenia, and represent a potential mechanism of glutamatergic dysregulation in this illness.

  9. Exome Sequence Data From Multigenerational Families Implicate AMPA Receptor Trafficking in Neurocognitive Impairment and Schizophrenia Risk.

    PubMed

    Kos, Mark Z; Carless, Melanie A; Peralta, Juan; Blackburn, August; Almeida, Marcio; Roalf, David; Pogue-Geile, Michael F; Prasad, Konasale; Gur, Ruben C; Nimgaonkar, Vishwajit; Curran, Joanne E; Duggirala, Ravi; Glahn, David C; Blangero, John; Gur, Raquel E; Almasy, Laura

    2016-03-01

    Schizophrenia is a mental disorder characterized by impairments in behavior, thought, and neurocognitive performance. We searched for susceptibility loci at a quantitative trait locus (QTL) previously reported for abstraction and mental flexibility (ABF), a cognitive function often compromised in schizophrenia patients and their unaffected relatives. Exome sequences were determined for 134 samples in 8 European American families from the original linkage study, including 25 individuals with schizophrenia or schizoaffective disorder. At chromosome 5q32-35.3, we analyzed 407 protein-altering variants for association with ABF and schizophrenia status. For replication, significant, Bonferroni-corrected findings were tested against cognitive traits in Mexican American families (n = 959), as well as interrogated for schizophrenia risk using GWAS results from the Psychiatric Genomics Consortium (PGC). From the gene SYNPO, rs6579797 (MAF = 0.032) shows significant associations with ABF (P = .015) and schizophrenia (P = .040), as well as jointly (P = .0027). In the Mexican American pedigrees, rs6579797 exhibits significant associations with IQ (P = .011), indicating more global effects on neurocognition. From the PGC results, other SYNPO variants were identified with near significant effects on schizophrenia risk, with a local linkage disequilibrium block displaying signatures of positive selection. A second missense variant within the QTL, rs17551608 (MAF = 0.19) in the gene WWC1, also displays a significant effect on schizophrenia in our exome sequences (P = .038). Remarkably, the protein products of SYNPO and WWC1 are interaction partners involved in AMPA receptor trafficking, a brain process implicated in synaptic plasticity. Our study reveals variants in these genes with significant effects on neurocognition and schizophrenia risk, identifying a potential pathogenic mechanism for schizophrenia spectrum disorders.

  10. ERK regulation of phosphodiesterase 4 enhances dopamine-stimulated AMPA receptor membrane insertion.

    PubMed

    Song, Roy S; Massenburg, Ben; Wenderski, Wendy; Jayaraman, Vino; Thompson, Lauren; Neves, Susana R

    2013-09-17

    AMPA-type glutamate receptor (AMPAR) trafficking is essential for modulating synaptic transmission strength. Prior studies that have characterized signaling pathways underlying AMPAR trafficking have identified the cAMP/PKA-mediated phosphorylation of GluA1, an AMPAR subunit, as a key step in the membrane insertion of AMPAR. Inhibition of ERK impairs AMPAR membrane insertion, but the mechanism by which ERK exerts its effect is unknown. Dopamine, an activator of both PKA and ERK, induces AMPAR insertion, but the relationship between the two protein kinases in the process is not understood. We used a combination of computational modeling and live cell imaging to determine the relationship between ERK and PKA in AMPAR insertion. We developed a dynamical model to study the effects of phosphodiesterase 4 (PDE4), a cAMP phosphodiesterase that is phosphorylated and inhibited by ERK, on the membrane insertion of AMPAR. The model predicted that PKA could be a downstream effector of ERK in regulating AMPAR insertion. We experimentally tested the model predictions and found that dopamine-induced ERK phosphorylates and inhibits PDE4. This regulation results in increased cAMP levels and PKA-mediated phosphorylation of DARPP-32 and GluA1, leading to increased GluA1 trafficking to the membrane. These findings provide unique insight into an unanticipated network topology in which ERK uses PDE4 to regulate PKA output during dopamine signaling. The combination of dynamical models and experiments has helped us unravel the complex interactions between two protein kinase pathways in regulating a fundamental molecular process underlying synaptic plasticity.

  11. Molecular Dissection of the Interaction between the AMPA Receptor and Cornichon Homolog-3

    PubMed Central

    Shanks, Natalie F.; Cais, Ondrej; Maruo, Tomohiko; Savas, Jeffrey N.; Zaika, Elena I.; Azumaya, Caleigh M.; Yates, John R.; Greger, Ingo

    2014-01-01

    Cornichon homologs (CNIHs) are AMPA-type glutamate receptor (AMPAR) auxiliary subunits that modulate AMPAR ion channel function and trafficking. Mechanisms underlying this interaction and functional modulation of the receptor complex are currently unclear. Here, using proteins expressed from mouse and rat cDNA, we show that CNIH-3 forms a stable complex with tetrameric AMPARs and contributes to the transmembrane density in single-particle electron microscopy structures. Peptide array-based screening and in vitro mutagenesis identified two clusters of conserved membrane-proximal residues in CNIHs that contribute to AMPAR binding. Because CNIH-1 binds to AMPARs but modulates gating at a significantly lower magnitude compared with CNIH-3, these conserved residues mediate a direct interaction between AMPARs and CNIHs. In addition, residues in the extracellular loop of CNIH-2/3 absent in CNIH-1/4 are critical for both AMPAR interaction and gating modulation. On the AMPAR extracellular domains, the ligand-binding domain and possibly a stretch of linker, connecting the ligand-binding domain to the fourth membrane-spanning segment, is the principal contact point with the CNIH-3 extracellular loop. In contrast, the membrane-distal N-terminal domain is less involved in AMPAR gating modulation by CNIH-3 and AMPAR binding to CNIH-3. Collectively, our results identify conserved residues in the membrane-proximal region of CNIHs that contribute to AMPAR binding and an additional unique segment in the CNIH-2/3 extracellular loop required for both physical interaction and gating modulation of the AMPAR. Consistent with the dissociable properties of binding and gating modulation, we identified a mutant CNIH-3 that preserves AMPAR binding capability but has attenuated activity of gating modulation. PMID:25186755

  12. Hippocampal GluA1-containing AMPA receptors mediate context-dependent sensitization to morphine.

    PubMed

    Xia, Yan; Portugal, George S; Fakira, Amanda K; Melyan, Zara; Neve, Rachael; Lee, H Thomas; Russo, Scott J; Liu, Jie; Morón, Jose A

    2011-11-09

    Glutamatergic systems, including AMPA receptors (AMPARs), are involved in opiate-induced neuronal and behavioral plasticity, although the mechanisms underlying these effects are not fully understood. In the present study, we investigated the effects of repeated morphine administration on AMPAR expression, synaptic plasticity, and context-dependent behavioral sensitization to morphine. We found that morphine treatment produced changes of synaptic AMPAR expression in the hippocampus, a brain area that is critically involved in learning and memory. These changes could be observed 1 week after the treatment, but only when mice developed context-dependent behavioral sensitization to morphine in which morphine treatment was associated with drug administration environment. Context-dependent behavioral sensitization to morphine was also associated with increased basal synaptic transmission and disrupted hippocampal long-term potentiation (LTP), whereas these effects were less robust when morphine administration was not paired with the drug administration environment. Interestingly, some effects may be related to the prior history of morphine exposure in the drug-associated environment, since alterations of AMPAR expression, basal synaptic transmission, and LTP were observed in mice that received a saline challenge 1 week after discontinuation of morphine treatment. Furthermore, we demonstrated that phosphorylation of GluA1 AMPAR subunit plays a critical role in the acquisition and expression of context-dependent behavioral sensitization, as this behavior is blocked by a viral vector that disrupts GluA1 phosphorylation. These data provide evidence that glutamatergic signaling in the hippocampus plays an important role in context-dependent sensitization to morphine and supports further investigation of glutamate-based strategies for treating opiate addiction.

  13. AMPA Receptor Antagonist NBQX Decreased Seizures by Normalization of Perineuronal Nets

    PubMed Central

    Chen, Wen; Li, Yan-Shuang; Gao, Jing; Lin, Xiao-Ying; Li, Xiao-Hong

    2016-01-01

    Epilepsy is a serious brain disorder with diverse seizure types and epileptic syndromes. AMPA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzoquinoxaline-2,3-dione (NBQX) attenuates spontaneous recurrent seizures in rats. However, the anti-epileptic effect of NBQX in chronic epilepsy model is poorly understood. Perineuronal nets (PNNs), specialized extracellular matrix structures, surround parvalbumin-positive inhibitory interneurons, and play a critical role in neuronal cell development and synaptic plasticity. Here, we focused on the potential involvement of PNNs in the treatment of epilepsy by NBQX. Rats were intraperitoneally (i.p.) injected with pentylenetetrazole (PTZ, 50 mg/kg) for 28 consecutive days to establish chronic epilepsy models. Subsequently, NBQX (20 mg/kg, i.p.) was injected for 3 days for the observation of behavioral measurements of epilepsy. The Wisteria floribundi agglutinin (WFA)-labeled PNNs were measured by immunohistochemical staining to evaluate the PNNs. The levels of three components of PNNs such as tenascin-R, aggrecan and neurocan were assayed by Western blot assay. The results showed that there are reduction of PNNs and decrease of tenascin-R, aggrecan and neurocan in the medial prefrontal cortex (mPFC) in the rats injected with PTZ. However, NBQX treatment normalized PNNs, tenascin-R, aggrecan and neurocan levels. NBQX was sufficient to decrease seizures through increasing the latency to seizures, decrease the duration of seizure onset, and reduce the scores for the severity of seizures. Furthermore, the degradation of mPFC PNNs by chondroitinase ABC (ChABC) exacerbated seizures in PTZ-treated rats. Finally, the anti-epileptic effect of NBQX was reversed by pretreatment with ChABC into mPFC. These findings revealed that PNNs degradation in mPFC is involved in the pathophysiology of epilepsy and enhancement of PNNs may be effective for the treatment of epilepsy. PMID:27880801

  14. Ceftriaxone attenuates cocaine relapse after abstinence through modulation of nucleus accumbens AMPA subunit expression.

    PubMed

    LaCrosse, Amber L; Hill, Kristine; Knackstedt, Lori A

    2016-02-01

    Using the extinction-reinstatement model of cocaine relapse, we and others have demonstrated that the antibiotic ceftriaxone attenuates cue- and cocaine-primed reinstatement of cocaine-seeking. Reinstatement is contingent on the release of glutamate in the nucleus accumbens core (NAc) and manipulations that reduce glutamate efflux or block post-synaptic glutamate receptors attenuate reinstatement. We have demonstrated that the mechanism of action by which ceftriaxone attenuates reinstatement involves increased NAc GLT-1 expression and a reduction in NAc glutamate efflux during reinstatement. Here we investigated the effects of ceftriaxone (100 and 200 mg/kg) on context-primed relapse following abstinence without extinction training and examined the effects of ceftriaxone on GluA1, GluA2 and GLT-1 expression. We conducted microdialysis during relapse to determine if an increase in NAc glutamate accompanies relapse after abstinence and whether ceftriaxone blunts glutamate efflux. We found that both doses of ceftriaxone attenuated relapse. While relapse was accompanied by an increase in NAc glutamate, ceftriaxone (200 mg/kg) was unable to significantly reduce NAc glutamate efflux during relapse despite its ability to upregulate GLT-1. GluA1 was reduced in the NAc by both doses of ceftriaxone while GluA2 expression was unchanged, indicating that ceftriaxone altered AMPA subunit composition following cocaine. Finally, GLT-1 was not altered in the PFC by ceftriaxone. These results indicate that it is possible to attenuate context-primed relapse to cocaine-seeking through modification of post-synaptic receptor properties without attenuating glutamate efflux during relapse. Furthermore, increasing NAc GLT-1 protein expression is not sufficient to attenuate glutamate efflux.

  15. Expression of ionotropic glutamate receptors, AMPA, kainite and NMDA, in the pigeon retina.

    PubMed

    Atoji, Yasuro

    2015-07-01

    Glutamate is an excitatory neurotransmitter in the vertebrate retina. A previous study found vesicular glutamate transporter 2 (vGluT2) mRNA in the pigeon retina, suggesting that bipolar and ganglion cells are glutamatergic. The present study examined the localization of ionotropic glutamate receptors to identify receptor cells in the pigeon retina using in situ hybridization histochemistry. Nine subunits of AMPA receptor (GluA1, GluA2, GluA3, and GluA4), kainate receptor (GluK1, GluK2, and GluK4), and NMDA receptor (GluN1 and GluN2A) were found to be expressed in the inner nuclear layer (INL) and ganglion cell layers. GluA1, GluA2, GluA3, and GluA4 were primarily expressed in the inner half of INL, and the signal intensity was strong for GluA2, GluA3, and GluA4. GluK1 was intensely expressed in the outer half of INL, whereas GluK2 and GluK4 were mainly localized in the inner half of INL. GluN1 and GluN2A were moderately expressed in the inner half of INL. Horizontal cells expressed GluA3 and GluA4, and ganglion cells expressed all subunits examined. These results suggest that the glutamatergic neurotransmission in the pigeon retina is similar to that in mammals.

  16. Transmembrane AMPA receptor regulatory protein (TARP) dysregulation in anterior cingulate cortex in schizophrenia

    PubMed Central

    Drummond, Jana B.; Tucholski, Janusz; Haroutunian, Vahram; Meador-Woodruff, James H.

    2013-01-01

    The glutamate hypothesis of schizophrenia proposes that abnormal glutamatergic neurotransmission occurs in this illness, and a major contribution may involve dysregulation of the AMPA subtype of ionotropic glutamate receptor (AMPAR). Transmembrane AMPAR regulatory proteins (TARPs) form direct associations with AMPARs to modulate the trafficking and biophysical functions of these receptors, and their dysregulation may alter the localization and activity of AMPARs, thus having a potential role in the pathophysiology of schizophrenia. We performed comparative quantitative real-time PCR and Western blot analysis to measure transcript (schizophrenia, N = 25; comparison subjects, N = 25) and protein (schizophrenia, N = 36; comparison subjects, N = 33) expression of TARPs (γ subunits 1-8) in the anterior cingulate cortex (ACC) in schizophrenia and a comparison group. TARP expression was also measured in frontal cortex of rats chronically treated with haloperidol decanoate (28.5 mg/kg every three weeks for nine months) to determine the effect of antipsychotic treatment on the expression of these molecules. We found decreased transcript expression of TARP γ-8 in schizophrenia. At the protein level, γ-3 and γ-5 were increased, while γ-4, γ-7 and γ-8 were decreased in schizophrenia. No changes in any of the molecules were noted in the frontal cortex of haloperidol-treated rats. TARPs are abnormally expressed at transcript and protein levels in ACC in schizophrenia, and these changes are likely due to the illness and not antipsychotic treatment. Alterations in the expression of TARPs may contribute to the pathophysiology of schizophrenia, and represent a potential mechanism of glutamatergic dysregulation in this illness. PMID:23566497

  17. Cooling unit for the AmpaCity project - One year successful operation

    NASA Astrophysics Data System (ADS)

    Herzog, Friedhelm; Kutz, Thomas; Stemmle, Mark; Kugel, Torsten

    2016-12-01

    High temperature super conductors (HTS) can efficiently be cooled with liquid nitrogen down to a temperature of 64 K (-209 °C). Lower temperatures are not practical, because at 63 K (-210 °C) nitrogen becomes solid. To achieve this temperature level the coolant has to be vaporized below atmospheric pressure. Messer has developed a cooling unit with an adequate vacuum subcooler, a liquid nitrogen circulation system, and a storage vessel for cooling an HTS-power cable. Liquid nitrogen is circulated through the superconducting cable to take out the heat, and afterward it is pumped through the subcooler to be recooled. In the circulation system liquid nitrogen is used as a dielectric fluid and as a heat transfer medium. It stays always liquid (subcooled) and does not vaporize. On the secondary side of the subcooler liquid nitrogen from the storage vessel is used as refrigerant. It is vaporized under a pressure of 150 mbar to achieve the desired low temperatures. The cooling unit was delivered in 2013 for the German AmpaCity project of RWE Deutschland AG, Nexans and Karlsruhe Institute of Technology. Within this project RWE and Nexans installed the worldwide longest superconducting power cable in the city of Essen, Germany. The cooling unit cools a 10 kV concentric HTS cable (40 MV A) with a length of 1000 m. The cable is in operation since March 10th, 2014. After more than one year of practical operation many important figures from cable and cooling unit are available. These figures are discussed and a total energy balance is shown to compare liquid nitrogen cooling with alternative mechanical cooling systems.

  18. Exome Sequence Data From Multigenerational Families Implicate AMPA Receptor Trafficking in Neurocognitive Impairment and Schizophrenia Risk

    PubMed Central

    Kos, Mark Z.; Carless, Melanie A.; Peralta, Juan; Blackburn, August; Almeida, Marcio; Roalf, David; Pogue-Geile, Michael F.; Prasad, Konasale; Gur, Ruben C.; Nimgaonkar, Vishwajit; Curran, Joanne E.; Duggirala, Ravi; Glahn, David C.; Blangero, John; Gur, Raquel E.; Almasy, Laura

    2016-01-01

    Schizophrenia is a mental disorder characterized by impairments in behavior, thought, and neurocognitive performance. We searched for susceptibility loci at a quantitative trait locus (QTL) previously reported for abstraction and mental flexibility (ABF), a cognitive function often compromised in schizophrenia patients and their unaffected relatives. Exome sequences were determined for 134 samples in 8 European American families from the original linkage study, including 25 individuals with schizophrenia or schizoaffective disorder. At chromosome 5q32–35.3, we analyzed 407 protein-altering variants for association with ABF and schizophrenia status. For replication, significant, Bonferroni-corrected findings were tested against cognitive traits in Mexican American families (n = 959), as well as interrogated for schizophrenia risk using GWAS results from the Psychiatric Genomics Consortium (PGC). From the gene SYNPO, rs6579797 (MAF = 0.032) shows significant associations with ABF (P = .015) and schizophrenia (P = .040), as well as jointly (P = .0027). In the Mexican American pedigrees, rs6579797 exhibits significant associations with IQ (P = .011), indicating more global effects on neurocognition. From the PGC results, other SYNPO variants were identified with near significant effects on schizophrenia risk, with a local linkage disequilibrium block displaying signatures of positive selection. A second missense variant within the QTL, rs17551608 (MAF = 0.19) in the gene WWC1, also displays a significant effect on schizophrenia in our exome sequences (P = .038). Remarkably, the protein products of SYNPO and WWC1 are interaction partners involved in AMPA receptor trafficking, a brain process implicated in synaptic plasticity. Our study reveals variants in these genes with significant effects on neurocognition and schizophrenia risk, identifying a potential pathogenic mechanism for schizophrenia spectrum disorders. PMID:26405221

  19. Different AMPA receptor subtypes mediate the distinct kinetic components of a biphasic EPSC in hippocampal interneurons

    PubMed Central

    Stincic, Todd L.; Frerking, Matthew E.

    2015-01-01

    CA1 hippocampal interneurons at the border between stratum radiatum (SR) and stratum lacunosum-moleculare (SLM) have AMPA receptor (AMPAR)-mediated excitatory postsynaptic currents (EPSCs) that consist of two distinct phases: a typical fast component (FC), and a highly unusual slow component (SC) that persists for hundreds of milliseconds. To determine whether these kinetically distinct components of the EPSC are mediated by distinct AMPAR subpopulations, we examined the relative contributions of GluA2-containing and—lacking AMPARs to the SC. GluA2-containing AMPARs mediated the majority of the FC whereas GluA2-lacking AMPARs preferentially generated the SC. When glutamate uptake through the glial glutamate transporter excitatory amino acid transporter (EAAT1) was inhibited, spill over-mediated AMPAR activation recruited an even slower third kinetic component that persisted for several seconds; however, this spillover-mediated current was mediated predominantly by GluA2-containing AMPARs and therefore was clearly distinct from the SC when uptake is intact. Thus, different AMPAR subpopulations that vary in GluA2 content mediate the distinct components of the AMPAR EPSC. The SC is developmentally downregulated in mice, declining after the second postnatal week. This downregulation affects both GluA2-containing and GluA2-lacking AMPARs mediating the SC, and is not accompanied by developmental changes in the GluA2 content of AMPARs underlying the FC. Thus, the downregulation of the SC appears to be independent of synaptic GluA2 expression, suggesting the involvement of another AMPAR subunit or an auxiliary protein. Our results therefore identify GluA2-dependent and GluA2-independent determinants of the SC: GluA2-lacking AMPARs preferentially contribute to the SC, while the developmental downregulation of the SC is independent of GluA2 content. PMID:26042027

  20. Dysregulation of AMPA receptor transmission in the nucleus accumbens in animal models of cocaine addiction

    PubMed Central

    Wolf, Marina E.

    2014-01-01

    Plasticity of glutamate transmission in neuronal circuits involving the nucleus accumbens (NAc) is now recognized to play a critical role in cocaine addiction. NAc neurons are excited primarily by AMPA-type glutamate receptors (AMPAR) and this is required for cocaine seeking. This review will briefly describe AMPAR properties and trafficking, with a focus on studies in NAc neurons, and then consider mechanisms by which cocaine may alter AMPAR transmission. Two examples will be discussed that may be important in two different stages of addiction: learning about drugs and drug-related cues during the period of drug exposure, and persistent vulnerability to craving and relapse after abstinence is achieved. The first example is drawn from studies of cultured NAc neurons. Elevation of DA levels (as would occur following cocaine exposure) facilitates activity-dependent strengthening of excitatory synapses onto medium spiny neurons, the main cell type and projection neuron of the NAc. This occurs because activation of D1-class receptors primes AMPAR for synaptic insertion, creating a temporal window in which stimuli related to cocaine-taking are more efficacious at eliciting synaptic plasticity and thus being encoded into memory. The second example involves rat models of cocaine addiction. Cell surface and synaptic expression of AMPAR on NAc neurons is persistently increased after withdrawal from repeated cocaine exposure. We hypothesize that this increases the reactivity of NAc neurons to glutamate inputs from cortex and limbic structures, facilitating the ability of these inputs to trigger cocaine seeking and thus contributing to the persistent vulnerability to relapse that characterizes addiction. PMID:20361291

  1. Behavioural and neuronal activation after microinjections of AMPA and NMDA into the perifornical lateral hypothalamus in rats.

    PubMed

    Li, Frederick W; Deurveilher, Samuel; Semba, Kazue

    2011-10-31

    The perifornical lateral hypothalamic area (PeFLH), which houses orexin/hypocretin (OX) neurons, is thought to play an important role in arousal, feeding, and locomotor activity. The present study examined behavioural effects of activating PeFLH neurons with microinjections of ionotropic glutamate receptor agonists. Three separate unilateral microinjections of either (1) AMPA (1 and 2mM in 0.1 μL artificial cerebrospinal fluid, ACSF) and ACSF, or (2) NMDA (1 and 10mM in 0.1 μL ACSF), and ACSF were made into the PeFLH of adult male rats. Following each injection, the rats were placed into an open field for behavioural scoring for 45 min. Rats were perfused after the third injection for immunohistochemistry for c-Fos and OX to assess the level of activation of OX neurons. Behavioural analyses showed that, as compared to ACSF conditions, AMPA injections produced a dose-dependent increase in locomotion and rearing that persisted throughout the 45 min recording period, and an increase in drinking. Injection of NMDA at 10mM, but not 1mM, induced a transient increase in locomotion and an increase in feeding. Histological analyses showed that while both agonists increased the number of neurons immunoreactive for c-Fos in the PeFLH, only AMPA increased the number of neurons immunoreactive for both c-Fos and OX. There were positive correlations between the number of c-Fos/OX-immunoreactive neurons and the amounts of locomotion, rearing, and drinking. These results support the role of ionotropic glutamate receptors on OX and other neurons in the PeFLH in the regulation of locomotor and ingestive behaviours.

  2. Role of zinc influx via AMPA/kainate receptor activation in metabotropic glutamate receptor-mediated calcium release.

    PubMed

    Takeda, Atsushi; Fuke, Sayuri; Minami, Akira; Oku, Naoto

    2007-05-01

    The uptake of free zinc into CA3 pyramidal cells and its significance was examined in rat hippocampal slices with ZnAF-2DA, a membrane-permeable zinc indicator. Intracellular ZnAF-2 signal in the CA3 pyramidal cell layer was increased during delivery of tetanic stimuli to the dentate granule cell layer. This increase was completely blocked in the presence of CNQX, an AMPA/kainate receptor antagonist. These results suggest that free zinc is taken up into CA3 pyramidal cells via activation of AMPA/kainate receptors. The effect of free zinc levels in the CA3 pyramidal cells on the increase in intracellular calcium via Group I metabotropic glutamate receptors was examined by regional delivery of tADA, a Group I metabotropic glutamate receptor agonist, to the stratum lucidum after blockade of AMPA/kainate receptor-mediated calcium and zinc influx. Intracellular calcium orange signal in the CA3 pyramidal cell layer was increased by tADA, whereas intracellular ZnAF-2 signal was not increased even in the presence of 100 muM zinc, suggesting that tADA induces calcium release from internal stores in CA3 pyramidal cells and is not involved in zinc uptake. The increase in calcium orange signal by tADA was enhanced by perfusion with pyrithione, a zinc ionophore that decreased basal ZnAF-2 signal in the CA3 pyramidal cell layer. It was blocked by perfusion with pyrithione and zinc that increased basal ZnAF-2 signal. The present study indicates that the increase in free calcium levels via the metabotropic glutamate receptor pathway is inversely related to free zinc levels in CA3 pyramidal cells.

  3. Effects of the potent ampakine CX614 on hippocampal and recombinant AMPA receptors: interactions with cyclothiazide and GYKI 52466.

    PubMed

    Arai, A C; Kessler, M; Rogers, G; Lynch, G

    2000-10-01

    R,S-alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor up-modulators of the benzamide type ("ampakines") have previously been shown to enhance excitatory synaptic transmission in vivo and in vitro and AMPA receptor currents in excised patches. The present study analyzed the effects of an ampakine (CX614; 2H,3H, 6aH-pyrrolidino[2",1"-3',2']1,3-oxazino[6',5'-5,4]benz o[e]1, 4-dioxan-10-one) that belongs to a benzoxazine subgroup characterized by greater structural rigidity and higher potency. CX614 enhanced the size (amplitude and duration) of field excitatory postsynaptic potentials in hippocampal slices and autaptically evoked excitatory postsynaptic currents in neuronal cultures with EC(50) values of 20 to 40 microM. The compound blocked desensitization (EC(50) = 44 microM) and slowed deactivation of responses to glutamate by a factor of 8.4 in excised patches. Currents through homomeric, recombinant AMPA receptors were enhanced with EC(50) values that did not differ greatly across GluR1-3 flop subunits (19-37 microM) but revealed slightly lower potency at corresponding flip variants. Competition experiments using modulation of [(3)H]fluorowillardiine binding suggested that CX614 and cyclothiazide share a common binding site but cyclothiazide seems to bind to an additional site not recognized by the ampakine. CX614 did not reverse the effect of GYKI 52466 on responses to brief glutamate pulses, which indicates that they act through separate sites, a conclusion that was confirmed in binding experiments. In sum, these results extend prior evidence that ampakines are effective in enhancing synaptic responses, most likely by slowing deactivation, and that their effects are exerted through sites that are only in part shared with other modulators.

  4. Preliminary recovery study of a commercial molecularly imprinted polymer for the extraction of glyphosate and AMPA in different environmental waters using MS.

    PubMed

    Claude, Bérengère; Berho, Catherine; Bayoudh, Sami; Amalric, Laurence; Coisy, Emeline; Nehmé, Reine; Morin, Philippe

    2017-03-29

    A commercial molecularly imprinted polymer (MIP) dedicated to glyphosate (GLY) and its main metabolite, aminomethylphosphonic acid (AMPA), was lately assessed as "POCIS-like" sampler on mineral water. The obtained results were encouraging with 111 and 122 mL day(-1) as sampling rates for GLY and AMPA, respectively. Therefore, before applying this passive sampler to environmental waters, the commercial phase was tested on different water matrices as a solid-phase extraction (SPE) device. The SPE protocol was carried on 250 mg of MIP with the following three steps: conditioning by Milli-Q water, loading of the sample (15 mL), and elution of the analytes by 4 mL 0.1 M HCl that were evaporated to dryness and recovered in 15 mL of the suitable solvent for analysis. This protocol was first applied to mineral water spiked by GLY and AMPA at environmental concentration levels (25-750 ng L(-1)). Analyses were carried out by ultra-performance liquid chromatography hyphenated to tandem mass after derivatization of GLY and AMPA by 9-fluorenylmethylchloroformate. The linear correlation between concentrations measured with and without SPE on MIP was proved.Furthermore, other extractions showed that high concentrations of metal ion interferents (lead(II), cadmium(II), and zinc(II)) in groundwaters did not reduce SPE performance of the MIP.Then, concentration assays were undertaken and brought noteworthy results, such as the recovery of 80% GLY and AMPA from groundwater spiked at 10 ng L(-1) and concentrated 100 times. For this purpose, ion exclusion chromatography hyphenated to mass was applied without previous derivatization of the analytes. The same concentration factor and analytical method were applied to 100 ng L(-1) spiked sea water with recoveries of 96% for GLY and 121% for AMPA.

  5. Decreased AMPA GluR2, but not GluR3, mRNA expression in rat amygdala and dorsal hippocampus following morphine-induced behavioural sensitization.

    PubMed

    Sepehrizadeh, Zargham; Bahrololoumi Shapourabadi, Mina; Ahmadi, Shamseddin; Hashemi Bozchlou, Saeed; Zarrindast, Mohammad-Reza; Sahebgharani, Mousa

    2008-11-01

    1. Repeated administration of psychostimulants and micro-opioid receptor agonists elicits a progressive enhancement of drug-induced behavioural responses, a phenomenon termed behavioural sensitization. These changes in behaviour may reflect plastic changes requiring regulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) receptor function. 2. In the present study, rats were treated for 7 days with saline or morphine (10 mg/kg). After a washout period of either 24 h or 7 days, locomotion, oral stereotypy and state-dependent memory in a passive avoidance test were measured in the presence or absence of 6-cyano-7-nitroquinoxaline-2,3-dione disodium salt (CNQX; 3 mg/kg), an AMPA receptor antagonist. In order to evaluate the mechanism underlying the behavioural responses, quantitative real-time reverse transcription-polymerase chain reaction was used to evaluate mRNA expression of the AMPA receptor subunits GluR2 and GluR3 in the striatum, prefrontal cortex, hippocampus, hypothalamus and amygdala of animals treated repeatedly with morphine. 3. The results indicate that repeated morphine treatment followed by 7 days (but not 24 h) washout produces behavioural sensitization, as determined by locomotion, oral stereotypy and state-dependent memory. Blockade of AMPA receptors with CNQX on the test day did not alter these behavioural responses. In addition, repeated morphine treatment followed by 7 days (but not 24 h) washout decreased GluR2 mRNA expression in both the amygdala (by 50%) and hippocampus (by 35%). Repeated morphine treatment did not alter GluR3 mRNA expression in any brain area assessed. 4. These data imply that AMPA receptors are involved in the development (but not expression) phase of behavioural sensitization. The decreases in GluR2 mRNA expression in the amygdala and hippocampus may result in the formation of calcium-permeable AMPA receptors, which are believed to play an important role in behavioural sensitization.

  6. Involvement of AMPA receptors in the antidepressant-like effects of lithium in the mouse tail suspension test and forced swim test.

    PubMed

    Gould, Todd D; O'Donnell, Kelley C; Dow, Eliot R; Du, Jing; Chen, Guang; Manji, Husseini K

    2008-03-01

    In addition to its clinical antimanic effects, lithium also has efficacy in the treatment of depression. However, the mechanism by which lithium exerts its antidepressant effects is unclear. Our objective was to further characterize the effects of peripheral and central administration of lithium in mouse models of antidepressant efficacy as well as to investigate the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors in these behaviors. We utilized the mouse forced swim test (FST) and tail suspension test (TST), intracerebroventricular (ICV) lithium administration, AMPA receptor inhibitors, and BS3 crosslinking followed by Western blot. Both short- and long-term administration of lithium resulted in robust antidepressant-like effects in the mouse FST and TST. Using ICV administration of lithium, we show that these effects are due to actions of lithium on the brain, rather than to peripheral effects of the drug. Both ICV and rodent chow (0.4% LiCl) administration paradigms resulted in brain lithium concentrations within the human therapeutic range. The antidepressant-like effects of lithium in the FST and TST were blocked by administration of AMPA receptor inhibitors. Additionally, administration of lithium increased the cell surface expression of GluR1 and GluR2 in the mouse hippocampus. Collectively, these data show that lithium exerts centrally mediated antidepressant-like effects in the mouse FST and TST that require AMPA receptor activation. Lithium may exert its antidepressant effects in humans through AMPA receptors, thus further supporting a role of targeting AMPA receptors as a therapeutic approach for the treatment of depression.

  7. Involvement of AMPA Receptors in the Antidepressant-Like Effects of Lithium in the Mouse Tail Suspension Test and Forced Swim Test

    PubMed Central

    Gould, Todd D.; O’Donnell, Kelley C.; Dow, Eliot R.; Du, Jing; Chen, Guang; Manji, Husseini K.

    2008-01-01

    In addition to its clinical antimanic effects, lithium also has efficacy in the treatment of depression. However, the mechanism by which lithium exerts its antidepressant effects is unclear. Our objective was to further characterize the effects of peripheral and central administration of lithium in mouse models of antidepressant efficacy as well as to investigate the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors in these behaviors. We utilized the mouse forced swim test (FST) and tail suspension test (TST), intracerebroventricular (ICV) lithium administration, AMPA receptor inhibitors, and BS3 crosslinking followed by western blot. Both short- and long-term administration of lithium resulted in robust antidepressant-like effects in the mouse FST and TST. Using ICV administration of lithium, we show that these effects are due to actions of lithium on the brain, rather than to peripheral effects of the drug. Both ICV and rodent chow (0.4% LiCl) administration paradigms resulted in brain lithium concentrations within the human therapeutic range. The effects of lithium to decrease immobility in the FST and TST were blocked by administration of AMPA receptor inhibitors. Additionally, administration of lithium increased the cell surface expression of GluR1 and GluR2 in the mouse hippocampus. Collectively, these data show that lithium exerts centrally mediated antidepressant-like effects in the mouse FST and TST that require AMPA receptor activation. Lithium may exert its antidepressant effects in humans through AMPA receptors, thus further supporting a role of targeting AMPA receptors as a therapeutic approach for the treatment of depression. PMID:18096191

  8. Evidence that Subanesthetic Doses of Ketamine Cause Sustained Disruptions of NMDA and AMPA-Mediated Frontoparietal Connectivity in Humans

    PubMed Central

    Shaw, Alexander D.; Jackson, Laura E.; Hall, Judith; Moran, Rosalyn; Saxena, Neeraj

    2015-01-01

    Following the discovery of the antidepressant properties of ketamine, there has been a recent resurgence in the interest in this NMDA receptor antagonist. Although detailed animal models of the molecular mechanisms underlying ketamine's effects have emerged, there are few MEG/EEG studies examining the acute subanesthetic effects of ketamine infusion in man. We recorded 275 channel MEG in two experiments (n = 25 human males) examining the effects of subanesthetic ketamine infusion. MEG power spectra revealed a rich set of significant oscillatory changes compared with placebo sessions, including decreases in occipital, parietal, and anterior cingulate alpha power, increases in medial frontal theta power, and increases in parietal and cingulate cortex high gamma power. Each of these spectral effects demonstrated their own set of temporal dynamics. Dynamic causal modeling of frontoparietal connectivity changes with ketamine indicated a decrease in NMDA and AMPA-mediated frontal-to-parietal connectivity. AMPA-mediated connectivity changes were sustained for up to 50 min after ketamine infusion had ceased, by which time perceptual distortions were absent. The results also indicated a decrease in gain of parietal pyramidal cells, which was correlated with participants' self-reports of blissful state. Based on these results, we suggest that the antidepressant effects of ketamine may depend on its ability to change the balance of frontoparietal connectivity patterns. SIGNIFICANCE STATEMENT In this paper, we found that subanesthetic doses of ketamine, similar to those used in antidepressant studies, increase anterior theta and gamma power but decrease posterior theta, delta, and alpha power, as revealed by magnetoencephalographic recordings. Dynamic causal modeling of frontoparietal connectivity changes with ketamine indicated a decrease in NMDA and AMPA-mediated frontal-to-parietal connectivity. AMPA-mediated connectivity changes were sustained for up to 50 min after

  9. AMPA receptor pHluorin-GluA2 reports NMDA receptor-induced intracellular acidification in hippocampal neurons.

    PubMed

    Rathje, Mette; Fang, Huaqiang; Bachman, Julia L; Anggono, Victor; Gether, Ulrik; Huganir, Richard L; Madsen, Kenneth L

    2013-08-27

    NMDA receptor activation promotes endocytosis of AMPA receptors, which is an important mechanism underlying long-term synaptic depression. The pH-sensitive GFP variant pHluorin fused to the N terminus of GluA2 (pH-GluA2) has been used to assay NMDA-mediated AMPA receptor endocytosis and recycling. Here, we demonstrate that in somatic and dendritic regions of hippocampal neurons a large fraction of the fluorescent signal originates from intracellular pH-GluA2, and that the decline in fluorescence in response to NMDA and AMPA primarily describes an intracellular acidification, which quenches the pHluorin signal from intracellular receptor pools. Neurons expressing an endoplasmic reticulum-retained mutant of GluA2 (pH-GluA2 ΔC49) displayed a larger response to NMDA than neurons expressing wild-type pH-GluA2. A similar NMDA-elicited decline in pHluorin signal was observed by expressing cytosolic pHluorin alone without fusion to GluA2 (cyto-pHluorin). Intracellular acidification in response to NMDA was further confirmed by using the ratiometric pH indicator carboxy-SNARF-1. The NMDA-induced decline was followed by rapid recovery of the fluorescent signal from both cyto-pHluorin and pH-GluA2. The recovery was sodium-dependent and sensitive to Na(+)/H(+)-exchanger (NHE) inhibitors. Moreover, recovery was more rapid after shRNA-mediated knockdown of the GluA2 binding PDZ domain-containing protein interacting with C kinase 1 (PICK1). Interestingly, the accelerating effect of PICK1 knockdown on the fluorescence recovery was eliminated in the presence of the NHE1 inhibitor zoniporide. Our results indicate that the pH-GluA2 recycling assay is an unreliable assay for studying AMPA receptor trafficking and also suggest a role for PICK1 in regulating intracellular pH via modulation of NHE activity.

  10. The AMPA receptor modulator S18986 in the prelimbic cortex enhances acquisition and retention of an odor-reward association.

    PubMed

    Yefimenko, Natalya; Portero-Tresserra, Marta; Martí-Nicolovius, Margarita; Guillazo-Blanch, Gemma; Vale-Martínez, Anna

    2013-08-26

    Systemic administration of S18986, a positive allosteric modulator of AMPA receptors, improves cognition. The present study further characterizes the drug's memory-enhancing properties and is the first to investigate its intracerebral effects on learning and memory. The results showed that rats receiving a single dose of S18986 (3 μg/site) into the prelimbic cortex, prior to olfactory discrimination acquisition, exhibited significantly shorter latencies and fewer errors to make the correct response, both in the acquisition and two drug-free retention tests. Such findings corroborate the involvement of glutamate receptors in odor-reward learning and confirm the role of the AMPAkine S18986 as a cognitive enhancer.

  11. Inquiries into the Biological Significance of Transmembrane AMPA Receptor Regulatory Protein (TARP) γ-8 Through Investigations of TARP γ-8 Null Mice§.

    PubMed

    Gleason, Scott D; Kato, Akihiko; Bui, Hai H; Thompson, Linda K; Valli, Sabrina N; Stutz, Patrick V; Kuo, Ming-Shang; Falcone, Julie F; Anderson, Wesley H; Li, Xia; Witkin, Jeffrey M

    2015-01-01

    Transmembrane AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor regulatory protein (TARP) γ-8 is an auxiliary protein associated with some AMPA receptors. Most strikingly, AMPA receptors associated with this TARP have a relatively high localization in the hippocampus. TARP γ-8 also modifies the pharmacology and trafficking of AMPA receptors. However, to date there is little understanding of the biological significance of this auxiliary protein. In the present set of studies we provide a characterization of the differential pharmacology and behavioral consequences of deletion of TARP γ-8 by comparing the wild type (WT) and γ-8 -/- (knock-out, KO) mouse. KO mice were mildly hyperactive in a locomotor arena but not in other environments compared to WT mice. Additionally, the KO mice demonstrated enhanced locomotor stimulatory effects of both d-amphetamine and phencyclidine. Marble-burying and digging behaviors were dramatically reduced in KO mice. In another assay that can detect anxiety-like phenotypes, the elevated plus maze, no differences were observed in overall movement or open arm entries. In the forced-swim assay, KO mice displayed decreases in immobility time like the antidepressant imipramine and the AMPA receptor potentiator, LY392098. In KO mice, the antidepressant-like effects of LY392098 were prevented whereas the effects of imipramine were unaffected. Convulsions were induced by pentylenetetrazole, N-methyl-D-aspartate, and by kainic acid. However, in KO mice, kainic acid produced less tonic convulsions and lethality. KO mice had reduced levels of norepinephrine in hippocampus and cerebellum but not in hypothalamus or prefrontal cortex, decreased levels of cAMP in hippocampus, and increased levels of acetylcholine in the hypothalamus and prefrontal cortex. KO mice displayed decreased turnover of dopamine and increased histamine turnover in multiple brain areas In contrast, serotonin and its metabolites were not significantly

  12. Modulation of NMDA and AMPA-mediated synaptic transmission by CB1 receptors in frontal cortical pyramidal cells.

    PubMed

    Li, Qiang; Yan, Haidun; Wilson, Wilkie A; Swartzwelder, H Scott

    2010-06-25

    Although the endogenous cannabinoid system modulates a variety of physiological and pharmacological processes, the specific role of cannabinoid CB1 receptors in the modulation of glutamatergic neurotransmission and neural plasticity is not well understood. Using whole-cell patch clamp recording techniques, evoked or spontaneous excitatory postsynaptic currents (eEPSCs or sEPSCs) were recorded from visualized, layer II/III pyramidal cells in frontal cortical slices from rat brain. Bath application of the CB1 receptor agonist, WIN 55212-2 (WIN), reduced the amplitude of NMDA receptor-mediated EPSCs in a concentration-dependent manner. When co-applied with the specific CB1 antagonists, AM251 or AM281, WIN did not suppress NMDA receptor-mediated EPSCs. WIN also reduced the amplitude of evoked AMPA receptor-mediated EPSCs, an effect that was also reversed by AM251. Both the frequency and amplitude of spontaneous AMPA receptor-mediated EPSCs were significantly reduced by WIN. In contrast, WIN reduced the frequency, but not the amplitude of miniature EPSCs, suggesting that the suppression of glutamatergic activity by CB1 receptors in the frontal neocortex is mediated by a presynaptic mechanism. Taken together, these data indicate a critical role for endocannabinoid signaling in the regulation of excitatory synaptic transmission in frontal neocortex, and suggest a possible neuronal mechanism whereby THC regulates cortical function.

  13. Calcyon is Necessary for Activity Dependent AMPA Receptor Internalization and LTD in CA1 Neurons of Hippocampus

    PubMed Central

    Davidson, Heather Trantham; Xiao, Jiping; Dai, Rujuan; Bergson, Clare

    2009-01-01

    Calcyon is a single transmembrane endocytic protein that regulates clathrin assembly and clathrin mediated endocytosis in brain. Ultrastructural studies indicate that calcyon localizes to spines, but whether it regulates glutamate neurotransmission is not known. Here, we show that deletion of the calcyon gene in mice inhibits agonist stimulated endocytosis of AMPA receptors, without altering basal surface levels of the GluR1 or GluR2 subunits. Whole cell patch clamp studies of hippocampal neurons in culture and CA1 synapses in slices revealed that knockout of calcyon abolishes long term synaptic depression (LTD) whereas mini-analysis in slices indicated basal transmission in hippocampus is unaffected by the deletion. Further, transfection of GFP-tagged calcyon rescued the ability of knockout cultures to undergo LTD. In contrast, intracellular dialysis of a fusion protein containing the clathrin light chain binding domain of calcyon blocked the induction of LTD in wild type hippocampal slices. Taken together, the present studies involving biochemical, immunological and electrophysiological analyses raise the possibility that calcyon plays a specialized role in regulating activity-dependent removal of synaptic AMPA receptors. PMID:19120439

  14. Structure and dynamics of AMPA receptor GluA2 in resting, pre-open and desensitized states

    PubMed Central

    Dürr, Katharina L.; Chen, Lei; Stein, Richard A.; De Zorzi, Rita; MihaelaFolea, I.; Walz, Thomas; Mchaourab, Hassane S.; Gouaux, Eric

    2014-01-01

    Summary Ionotropic glutamate receptors (iGluRs) mediate the majority of fast excitatory signaling in the nervous system. Despite the profound importance of iGluRs in the nervous system, little is known about the structures and dynamics of intact receptors in distinct functional states. Here we elucidate the structures of the intact GluA2 AMPA receptor in an apo resting/closed state, in an activated/pre-open state bound with the partial agonists and a positive allosteric modulator and in a desensitized/closed state in complex with FW alone. To probe the conformational properties of these states, we carried out double electron-electron resonance experiments on cysteine mutants and cryo-electron microscopy studies. We show how agonist binding modulates the conformation of the ligand binding domain 'layer' of the intact receptors and how, upon desensitization, the receptor undergoes large conformational rearrangements of amino-terminal and ligand-binding domains. We define mechanistic principles by which to understand antagonism, activation and desensitization in AMPA iGluRs. PMID:25109876

  15. Basal adenosine modulates the functional properties of AMPA receptors in mouse hippocampal neurons through the activation of A1R A2AR and A3R

    PubMed Central

    Di Angelantonio, Silvia; Bertollini, Cristina; Piccinin, Sonia; Rosito, Maria; Trettel, Flavia; Pagani, Francesca; Limatola, Cristina; Ragozzino, Davide

    2015-01-01

    Adenosine is a widespread neuromodulator within the CNS and its extracellular level is increased during hypoxia or intense synaptic activity, modulating pre- and postsynaptic sites. We studied the neuromodulatory action of adenosine on glutamatergic currents in the hippocampus, showing that activation of multiple adenosine receptors (ARs) by basal adenosine impacts postsynaptic site. Specifically, the stimulation of both A1R and A3R reduces AMPA currents, while A2AR has an opposite potentiating effect. The effect of ARs stimulation on glutamatergic currents in hippocampal cultures was investigated using pharmacological and genetic approaches. A3R inhibition by MRS1523 increased GluR1-Ser845 phosphorylation and potentiated AMPA current amplitude, increasing the apparent affinity for the agonist. A similar effect was observed blocking A1R with DPCPX or by genetic deletion of either A3R or A1R. Conversely, impairment of A2AR reduced AMPA currents, and decreased agonist sensitivity. Consistently, in hippocampal slices, ARs activation by AR agonist NECA modulated glutamatergic current amplitude evoked by AMPA application or afferent fiber stimulation. Opposite effects of AR subtypes stimulation are likely associated to changes in GluR1 phosphorylation and represent a novel mechanism of physiological modulation of glutamatergic transmission by adenosine, likely acting in normal conditions in the brain, depending on the level of extracellular adenosine and the distribution of AR subtypes. PMID:26528137

  16. Transcriptome profile reveals AMPA receptor dysfunction in the hippocampus of the Rsk2-knockout mice, an animal model of Coffin-Lowry syndrome.

    PubMed

    Mehmood, Tahir; Schneider, Anne; Sibille, Jérémie; Sibillec, Jérémie; Marques Pereira, Patricia; Pannetier, Solange; Ammar, Mohamed Raafet; Dembele, Doulaye; Thibault-Carpentier, Christelle; Rouach, Nathalie; Hanauer, André

    2011-03-01

    Coffin-Lowry syndrome (CLS) is a syndromic form of mental retardation caused by loss of function mutations in the X-linked RPS6KA3 gene, which encodes RSK2, a serine/threonine kinase acting in the MAPK/ERK pathway. The mouse invalidated for the Rps6ka3 (Rsk2-KO) gene displays learning and long-term spatial memory deficits. In the current study, we compared hippocampal gene expression profiles from Rsk2-KO and normal littermate mice to identify changes in molecular pathways. Differential expression was observed for 100 genes encoding proteins acting in various biological pathways, including cell growth and proliferation, cell death and higher brain function. The twofold up-regulated gene (Gria2) was of particular interest because it encodes the subunit GLUR2 of the AMPA glutamate receptor. AMPA receptors mediate most fast excitatory synaptic transmission in the central nervous system. We provide evidence that in the hippocampus of Rsk2-KO mice, expression of GLUR2 at the mRNA and at the protein levels is significantly increased, whereas basal AMPA receptor-mediated transmission in the hippocampus of Rsk2-KO mice is significantly decreased. This is the first time that such deregulations have been demonstrated in the mouse model of the Coffin-Lowry syndrome. Our findings suggest that a defect in AMPA neurotransmission and plasticity contribute to mental retardation in CLS patients.

  17. Administration of a PTEN inhibitor BPV(pic) attenuates early brain injury via modulating AMPA receptor subunits after subarachnoid hemorrhage in rats.

    PubMed

    Chen, Yujie; Luo, Chunxia; Zhao, Mingyue; Li, Qiang; Hu, Rong; Zhang, John H; Liu, Zhi; Feng, Hua

    2015-02-19

    The aim of this study was to investigate whether the phosphatase and tensin homolog deleted on chromosome ten (PTEN) inhibitor dipotassium bisperoxo(pyridine-2-carboxyl) oxovanadate (BPV(pic)) attenuates early brain injury by modulating α-amino-3-hydroxy-5-methyl-4-isoxa-zolep-propionate (AMPA) receptor subunits after subarachnoid hemorrhage (SAH). A standard intravascular perforation model was used to produce the experimental SAH in Sprague-Dawley rats. BPV(pic) treatment (0.2mg/kg) was evaluated for effects on neurological score, brain water content, Evans blue extravasation, hippocampal neuronal death and AMPA receptor subunits alterations after SAH. We found that BPV(pic) is effective in attenuating BBB disruption, lowering edema, reducing hippocampal neural death and improving neurological outcomes. In addition, the AMPA receptor subunit GluR1 protein expression at cytomembrane was downregulated, whereas the expression of GluR2 and GluR3 was upregulated after BPV(pic) treatment. Our results suggest that PTEN inhibited by BPV(pic) plays a neuroprotective role in SAH pathophysiology, possibly by alterations in glutamate AMPA receptor subunits.

  18. AMPA receptor activation, but not the accumulation of endogenous extracellular glutamate, induces paralysis and motor neuron death in rat spinal cord in vivo.

    PubMed

    Corona, Juan Carlos; Tapia, Ricardo

    2004-05-01

    The mechanisms of motor neuron (MN) degeneration in amyotrophic lateral sclerosis (ALS) are unknown, but glutamate-mediated excitotoxicity may be involved. To examine directly this idea in vivo, we have used microdialysis in the rat lumbar spinal cord and showed that four- to fivefold increases in the concentration of endogenous extracellular glutamate during at least 1 h, by perfusion with the glutamate transport inhibitor L-2,4-trans-pyrrolidine-dicarboxylate, elicited no motor alterations or MN damage. Stimulation of glutamate release with 4-aminopyridine induced transitory ipsilateral hindlimb muscular twitches but no MN damage. In contrast, perfusion of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) did not modify glutamate levels but produced intense muscular spasms, followed by ipsilateral permanent hindlimb paralysis and a remarkable loss of MNs. These effects of AMPA were prevented by co-perfusion with the AMPA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline. Perfusion with NMDA or kainate produced no motor effects or MN damage. Thus, the elevation of endogenous extracellular glutamate in vivo due to blockade of its transport is innocuous for spinal MNs. Because this resistance is observed under the same experimental conditions in which MNs are highly vulnerable to AMPA, these results indicate that excitotoxicity due to this mechanism might not be an important factor in the pathogenesis of ALS.

  19. AMPA receptors in the rat and primate hippocampus: a possible absence of GluR2/3 subunits in most interneurons.

    PubMed

    Leranth, C; Szeidemann, Z; Hsu, M; Buzsáki, G

    1996-02-01

    Amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are assembled from the four subunits GluR1, 2, 3, 4 (or GluRA, B, C, D). AMPA channels that do not contain the GluR2 subunit are permeable to calcium. Recent studies indicate that excitotoxic as well as epileptic and ischemic cell damage may be mediated not only by N-methyl-Daspartate receptors, but also by AMPA receptors. The majority of interneurons in the hippocampus are resistant, but subsets of interneurons are consistently damaged in different disease states. Single immunolabeling using antibodies against AMPA receptor subunits, together with double immunolabeling for calcium-binding proteins (parvalbumin, calbindin and calretinin) and the neuropeptide somatostatin, were performed to study GluR1-4 immunoreactivity in interneuronal populations and principal cells. The ultrastructure of GluR1-4 labeled neurons was also examined using electron microscopy. With the exception of calbindin-positive interneurons, GluR2/3 was absent from hippocampal interneurons in both rat and monkey. In the rat, interneurons were more strongly immunoreactive against GluR1 than principal cells. In the monkey, immunoreactivity for GluR4 in interneurons was stronger than for GluR1. All GluR subunits were confined to spines, dendritic membrane and cytoplasm surrounding the nucleus but absent from axons and presynaptic terminals. Our findings suggest that hippocampal principal cells and interneurons express different complements of AMPA receptor subunits. Furthermore, the absence of GluR2 and/or GluR3 in both vulnerable and resistant interneurons subtypes indicates that knowledge of receptor subunit composition is not sufficient to predict neuronal vulnerability.

  20. Phenobarbital but Not Diazepam Reduces AMPA/kainate Receptor Mediated Currents and Exerts Opposite Actions on Initial Seizures in the Neonatal Rat Hippocampus

    PubMed Central

    Nardou, Romain; Yamamoto, Sumii; Bhar, Asma; Burnashev, Nail; Ben-Ari, Yehezkel; Khalilov, Ilgam

    2011-01-01

    Diazepam (DZP) and phenobarbital (PB) are extensively used as first and second line drugs to treat acute seizures in neonates and their actions are thought to be mediated by increasing the actions of GABAergic signals. Yet, their efficacy is variable with occasional failure or even aggravation of recurrent seizures questioning whether other mechanisms are not involved in their actions. We have now compared the effects of DZP and PB on ictal-like events (ILEs) in an in vitro model of mirror focus (MF). Using the three-compartment chamber with the two immature hippocampi and their commissural fibers placed in three different compartments, kainate was applied to one hippocampus and PB or DZP to the contralateral one, either after one ILE, or after many recurrent ILEs that produce an epileptogenic MF. We report that in contrast to PB, DZP aggravated propagating ILEs from the start, and did not prevent the formation of MF. PB reduced and DZP increased the network driven giant depolarizing potentials suggesting that PB may exert additional actions that are not mediated by GABA signaling. In keeping with this, PB but not DZP reduced field potentials recorded in the presence of GABA and NMDA receptor antagonists. These effects are mediated by a direct action on AMPA/kainate receptors since PB: (i) reduced AMPA/kainate receptor mediated currents induced by focal applications of glutamate; (ii) reduced the amplitude and the frequency of AMPA but not NMDA receptor mediated miniature excitatory postsynaptic currents (EPSCs); (iii) augmented the number of AMPA receptor mediated EPSCs failures evoked by minimal stimulation. These effects persisted in MF. Therefore, PB exerts its anticonvulsive actions partly by reducing AMPA/kainate receptors mediated EPSCs in addition to the pro-GABA effects. We suggest that PB may have advantage over DZP in the treatment of initial neonatal seizures since the additional reduction of glutamate receptors mediated signals may reduce the severity

  1. Numbers, Densities, and Colocalization of AMPA- and NMDA-Type Glutamate Receptors at Individual Synapses in the Superficial Spinal Dorsal Horn of Rats

    PubMed Central

    Fukazawa, Yugo; Eördögh, Mária; Muszil, Dóra; Molnár, Elek; Itakura, Makoto; Takahashi, Masami; Shigemoto, Ryuichi

    2008-01-01

    Ionotropic glutamate receptors play important roles in spinal processing of nociceptive sensory signals and induction of central sensitization in chronic pain. Here we applied highly sensitive freeze-fracture replica labeling to laminae I–II of the spinal dorsal horn of rats and investigated the numbers, densities, and colocalization of AMPA- and NMDA-type glutamate receptors at individual postsynaptic membrane specializations with a high resolution. All glutamatergic postsynaptic membranes in laminae I–II expressed AMPA receptors, and most of them (96%) were also immunoreactive for the NR1 subunit of NMDA receptors. The numbers of gold particles for AMPA and NMDA receptors at individual postsynaptic membranes showed a linear correlation with the size of postsynaptic membrane specializations and varied in the range of 8–214 and 5–232 with median values of 37 and 28, whereas their densities varied in the range of 325–3365/μm2 and 102–2263/μm2 with median values of 1115/μm2 and 777/μm2, respectively. Virtually all (99%) glutamatergic postsynaptic membranes expressed GluR2, and most of them (87%) were also immunoreactive for GluR1. The numbers of gold particles for pan-AMPA, NR1, and GluR2 subunits showed a linear correlation with the size of postsynaptic surface areas. Concerning GluR1, there may be two populations of synapses with high and low GluR1 densities. In synapses larger than 0.1 μm2, GluR1 subunits were recovered in very low numbers. Differential expression of GluR1 and GluR2 subunits suggests regulation of AMPA receptor subunit composition by presynaptic mechanism. PMID:18815255

  2. Activation of AMPA receptor promotes TNF-α release via the ROS-cSrc-NFκB signaling cascade in RAW264.7 macrophages

    SciTech Connect

    Cheng, Xiu-Li; Ding, Fan; Li, Hui; Tan, Xiao-Qiu; Liu, Xiao; Cao, Ji-Min; Gao, Xue

    2015-05-29

    The relationship between glutamate signaling and inflammation has not been well defined. This study aimed to investigate the role of AMPA receptor (AMPAR) in the expression and release of tumor necrosis factor-alpha (TNF-α) from macrophages and the underlying mechanisms. A series of approaches, including confocal microscopy, immunofluorescency, flow cytometry, ELISA and Western blotting, were used to estimate the expression of AMPAR and downstream signaling molecules, TNF-α release and reactive oxygen species (ROS) generation in the macrophage-like RAW264.7 cells. The results demonstrated that AMPAR was expressed in RAW264.7 cells. AMPA significantly enhanced TNF-α release from RAW264.7 cells, and this effect was abolished by CNQX (AMPAR antagonist). AMPA also induced elevation of ROS production, phosphorylation of c-Src and activation of nuclear factor (NF)-κB in RAW264.7 cells. Blocking c-Src by PP2, scavenging ROS by glutathione (GSH) or inhibiting NF-κB activation by pyrrolidine dithiocarbamate (PDTC) decreased TNF-α production from RAW264.7 cells. We concluded that AMPA promotes TNF-α release in RAW264.7 macrophages likely through the following signaling cascade: AMPAR activation → ROS generation → c-Src phosphorylation → NF-κB activation → TNF-α elevation. The study suggests that AMPAR may participate in macrophage activation and inflammation. - Highlights: • AMPAR is expressed in RAW264.7 macrophages and is upregulated by AMPA stimulation. • Activation of AMPAR stimulates TNF-α release in macrophages through the ROS-cSrc-NFκB signaling cascade. • Macrophage AMPAR signaling may play an important role in inflammation.

  3. Therapeutic window of opportunity for the neuroprotective effect of valproate versus the competitive AMPA receptor antagonist NS1209 following status epilepticus in rats.

    PubMed

    Langer, Melanie; Brandt, Claudia; Zellinger, Christina; Löscher, Wolfgang

    2011-01-01

    Epileptogenesis, i.e., the process leading to epilepsy, is a presumed consequence of brain insults including head trauma, stroke, infections, tumors, status epilepticus (SE), and complex febrile seizures. Typically, brain insults produce morphological and functional alterations in the hippocampal formation, including neurodegeneration in CA1, CA3, and, most consistently, the dentate hilus. Most of these alterations develop gradually, over several days, after the insult, providing a therapeutic window of opportunity for neuroprotective agents in the immediate post-injury period. We have previously reported that prolonged (four weeks) treatment with the antiepileptic drug valproate (VPA) after SE prevents hippocampal damage and most of the behavioral alterations that occur after brain insult, but not the development of spontaneously occurring seizures. These data indicated that VPA, although not preventing epilepsy, might be an effective disease-modifying treatment following brain insult. The present study was designed to (1) determine the therapeutic window for the neuroprotective effect of VPA after SE; (2) compare the efficacy of different intermittent i.p. versus continuous i.v. VPA treatment protocols; and (3) compare VPA with the glutamate (AMPA) receptor antagonist NS1209. As in our previous study with VPA, SE was induced by sustained electrical stimulation of the basolateral amygdala in rats and terminated after 4 h by diazepam. In vehicle controls, >90% of the animals developed significant neurodegeneration in the dentate hilus, whereas damage in CA1 and CA3 was more variable. Hilar parvalbumin-expressing interneurons were more sensitive to the effects of seizures than somatostatin-stained hilar interneurons or hilar mossy cells. Among the various VPA treatment protocols, continuous infusion of VPA for 24 immediately following the SE was the most effective neuroprotective treatment, preventing most of the neuronal damage. Infusion with NS1209 for 24 h

  4. Blockade of Ca2+-permeable AMPA/kainate channels decreases oxygen-glucose deprivation-induced Zn2+ accumulation and neuronal loss in hippocampal pyramidal neurons.

    PubMed

    Yin, Hong Z; Sensi, Stefano L; Ogoshi, Fumio; Weiss, John H

    2002-02-15

    Synaptic release of Zn2+ and its translocation into postsynaptic neurons probably contribute to neuronal injury after ischemia or epilepsy. Studies in cultured neurons have revealed that of the three major routes of divalent cation entry, NMDA channels, voltage-sensitive Ca2+ channels (VSCCs), and Ca2+-permeable AMPA/kainate (Ca-A/K) channels, Ca-A/K channels exhibit the highest permeability to exogenously applied Zn2+. However, routes through which synaptically released Zn2+ gains entry to postsynaptic neurons have not been characterized in vivo. To model ischemia-induced Zn2+ movement in a system approximating the in vivo situation, we subjected mouse hippocampal slice preparations to controlled periods of oxygen and glucose deprivation (OGD). Timm's staining revealed little reactive Zn2+ in CA1 and CA3 pyramidal neurons of slices exposed in the presence of O2 and glucose. However, 15 min of OGD resulted in marked labeling in both regions. Whereas strong Zn2+ labeling persisted if both the NMDA antagonist MK-801 and the VSCC blocker Gd3+ were present during OGD, the presence of either the Ca-A/K channel blocker 1-naphthyl acetyl spermine (NAS) or the extracellular Zn2+ chelator Ca2+ EDTA substantially decreased Zn2+ accumulation in pyramidal neurons of both subregions. In parallel experiments, slices were subjected to 5 min OGD exposures as described above, followed 4 hr later by staining with the cell-death marker propidium iodide. As in the Timm's staining experiments, substantial CA1 or CA3 pyramidal neuronal damage occurred despite the presence of MK-801 and Gd3+, whereas injury was decreased by NAS or by Ca2+ EDTA (in CA1).

  5. Orexin-A differentially modulates AMPA-preferring responses of ganglion cells and amacrine cells in rat retina.

    PubMed

    Zheng, Chao; Deng, Qin-Qin; Liu, Lei-Lei; Wang, Meng-Ya; Zhang, Gong; Sheng, Wen-Long; Weng, Shi-Jun; Yang, Xiong-Li; Zhong, Yong-Mei

    2015-06-01

    By activating their receptors (OX1R and OX2R) orexin-A/B regulate wake/sleeping states, feeding behaviors, but the function of these peptides in the retina remains unknown. Using patch-clamp recordings and calcium imaging in rat isolated retinal cells, we demonstrated that orexin-A suppressed α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)-preferring receptor-mediated currents (AMPA-preferring currents) in ganglion cells (GCs) through OX1R, but potentiated those in amacrine cells (ACs) through OX2R. Consistently, in rat retinal slices orexin-A suppressed light-evoked AMPA-preferring receptor-mediated excitatory postsynaptic currents in GCs, but potentiated those in ACs. Intracellular dialysis of GDP-β-S or preincubation with the Gi/o inhibitor pertussis toxin (PTX) abolished both the effects. Either cAMP/the protein kinase A (PKA) inhibitor Rp-cAMP or cGMP/the PKG blocker KT5823 failed to alter the orexin-A effects. Whilst both of them involved activation of protein kinase C (PKC), the effects on GCs and ACs were respectively eliminated by the phosphatidylinositol (PI)-phospholipase C (PLC) inhibitor and phosphatidylcholine (PC)-PLC inhibitor. Moreover, in GCs orexin-A increased [Ca(2+)]i and the orexin-A effect was blocked by intracellular Ca(2+)-free solution and by inositol 1,4,5-trisphosphate (IP3) receptor antagonists. In contrast, orexin-A did not change [Ca(2+)]i in ACs and the orexin-A effect remained in intracellular or extracellular Ca(2+)-free solution. We conclude that a distinct Gi/o/PI-PLC/IP3/Ca(2+)-dependent PKC signaling pathway, following the activation of OX1R, is likely responsible for the orexin-A effect on GCs, whereas a Gi/o/PC-PLC/Ca(2+)-independent PKC signaling pathway, following the activation of OX2R, mediates the orexin-A effect on ACs. These two actions of orexin-A, while working in concert, provide a characteristic way for modulating information processing in the inner retina.

  6. Acoustic trauma slows AMPA receptor‐mediated EPSCs in the auditory brainstem, reducing GluA4 subunit expression as a mechanism to rescue binaural function

    PubMed Central

    Pilati, Nadia; Linley, Deborah M.; Selvaskandan, Haresh; Uchitel, Osvaldo; Hennig, Matthias H.; Kopp‐Scheinpflug, Cornelia

    2016-01-01

    Key points Lateral superior olive (LSO) principal neurons receive AMPA receptor (AMPAR) ‐ and NMDA receptor (NMDAR)‐mediated EPSCs and glycinergic IPSCs.Both EPSCs and IPSCs have slow kinetics in prehearing animals, which during developmental maturation accelerate to sub‐millisecond decay time‐constants. This correlates with a change in glutamate and glycine receptor subunit composition quantified via mRNA levels.The NMDAR‐EPSCs accelerate over development to achieve decay time‐constants of 2.5 ms. This is the fastest NMDAR‐mediated EPSC reported.Acoustic trauma (AT, loud sounds) slow AMPAR‐EPSC decay times, increasing GluA1 and decreasing GluA4 mRNA.Modelling of interaural intensity difference suggests that the increased EPSC duration after AT shifts interaural level difference to the right and compensates for hearing loss.Two months after AT the EPSC decay times recovered to control values.Synaptic transmission in the LSO matures by postnatal day 20, with EPSCs and IPSCs having fast kinetics. AT changes the AMPAR subunits expressed and slows the EPSC time‐course at synapses in the central auditory system. Abstract Damaging levels of sound (acoustic trauma, AT) diminish peripheral synapses, but what is the impact on the central auditory pathway? Developmental maturation of synaptic function and hearing were characterized in the mouse lateral superior olive (LSO) from postnatal day 7 (P7) to P96 using voltage‐clamp and auditory brainstem responses. IPSCs and EPSCs show rapid acceleration during development, so that decay kinetics converge to similar sub‐millisecond time‐constants (τ, 0.87 ± 0.11 and 0.77 ± 0.08 ms, respectively) in adult mice. This correlated with LSO mRNA levels for glycinergic and glutamatergic ionotropic receptor subunits, confirming a switch from Glyα2 to Glyα1 for IPSCs and increased expression of GluA3 and GluA4 subunits for EPSCs. The NMDA receptor (NMDAR)‐EPSC decay τ accelerated from >40 ms in

  7. Region-specific alterations of AMPA receptor phosphorylation and signaling pathways in the pilocarpine model of epilepsy.

    PubMed

    Lopes, Mark William; Lopes, Samantha Cristiane; Costa, Ana Paula; Gonçalves, Filipe Marques; Rieger, Débora Kurrle; Peres, Tanara Vieira; Eyng, Helena; Prediger, Rui Daniel; Diaz, Alexandre Paim; Nunes, Jean Costa; Walz, Roger; Leal, Rodrigo Bainy

    2015-08-01

    Disturbances in glutamatergic transmission and signaling pathways have been associated with temporal lobe epilepsy (TLE) in humans. However, the profile of these alterations within specific regions of the hippocampus and cerebral cortex has not yet been examined. The pilocarpine model in rodents reproduces the main features of TLE in humans. The present study aims to characterize specific alterations of the glutamatergic transmission and signaling pathways in the dorsal (DH) and ventral hippocampus (VH) and temporal cortex (Ctx) of male adult Wistar rats 60 days after pilocarpine treatment (chronic period). The western blotting analyzes show a decrease of AMPA glutamate receptor subunit (GluA1)-Ser(845) phosphorylation; reduction of ERK1 and PKA activity; up-regulation of GFAP and down-regulation of the glutamate transporter EAAT2 expression in the DH. In contrast, in the VH it was observed a decrease of GluA1-Ser(831) phosphorylation and JNKp54 and PKC activity. In the Ctx, only ERK1 phosphorylation/activity decreased. The level of GluA1-Ser(845) phosphorylation and PKA activity (DH) and the level of GluA1-Ser(831) phosphorylation and PKC activity (VH) appear to be correlated, respectively. These findings suggest a differential imbalance of the signaling pathways involved in the site-specific phosphorylation of AMPA receptor in the hippocampus. Furthermore, we suggest that dorsal hippocampus is probably more susceptible to the impairment of glutamate uptake and gliose, since only this area displayed a significant decrease of EAAT2 and increment of GFAP. Taken together, our study suggests that specific neurochemical alterations take place in hippocampal sub regions. This approach may be valuable for understanding the onset of seizures and the alterations of neuronal excitability in specific regions and may help to establish therapeutic targets for treatment of this neuropathology.

  8. Control of Transmembrane Protein Diffusion within the Postsynaptic Density Assessed by Simultaneous Single-Molecule Tracking and Localization Microscopy

    PubMed Central

    Li, Tuo P.; Blanpied, Thomas A.

    2016-01-01

    Postsynaptic transmembrane proteins are critical elements of synapses, mediating trans-cellular contact, sensitivity to neurotransmitters and other signaling molecules, and flux of Ca and other ions. Positioning and mobility of each member of this large class of proteins is critical to their individual function at the synapse. One critical example is that the position of glutamate receptors within the postsynaptic density (PSD) strongly modulates their function by aligning or misaligning them with sites of presynaptic vesicle fusion. In addition, the regulated ability of receptors to move in or out of the synapse is critical for activity-dependent plasticity. However, factors that control receptor mobility within the boundaries of the synapse are not well understood. Notably, PSD scaffold molecules accumulate in domains much smaller than the synapse. Within these nanodomains, the density of proteins is considerably higher than that of the synapse as a whole, so high that steric hindrance is expected to reduce receptor mobility substantially. However, while numerical modeling has demonstrated several features of how the varying protein density across the face of a single PSD may modulate receptor motion, there is little experimental information about the extent of this influence. To address this critical aspect of synaptic organizational dynamics, we performed single-molecule tracking of transmembrane proteins using universal point accumulation-for-imaging-in-nanoscale-topography (uPAINT) over PSDs whose internal structure was simultaneously resolved using photoactivated localization microscopy (PALM). The results provide important experimental confirmation that PSD scaffold protein density strongly influences the mobility of transmembrane proteins. A protein with a cytosolic domain that does not bind PSD-95 was still slowed in regions of high PSD-95 density, suggesting that crowding by scaffold molecules and perhaps other proteins is sufficient to stabilize

  9. Requirement of AMPA receptor stimulation for the sustained antidepressant activity of ketamine and LY341495 during the forced swim test in rats.

    PubMed

    Koike, Hiroyuki; Chaki, Shigeyuki

    2014-09-01

    Ketamine, a non-competitive N-methyl-d-aspartate receptor antagonist, and group II metabotropic glutamate (mGlu2/3) receptor antagonists produce antidepressant effects in animal models of depression, which last for at least 24h, through the transient increase in glutamate release, leading to activation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) receptor. Both ketamine and an mGlu2/3 receptor antagonist reportedly increase the expression of GluR1, an AMPA receptor subunit, within 24h, which may account for the sustained enhancement of excitatory synaptic transmission following ketamine administration. However, whether the sustained increase in AMPA receptor-mediated synaptic transmission is associated with the antidepressant effects of ketamine and mGlu2/3 receptor antagonists has not yet been investigated. In the present study, to address this question, we tested whether AMPA receptor stimulation at 24h after a single injection of ketamine or an mGlu2/3 receptor antagonist, (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl)propanoic acid (LY341495) was necessary for the antidepressant effect of these compounds using a forced swim test in rats. A single injection of ketamine or LY341495 at 24h before the test significantly decreased the immobility time. An AMPA receptor antagonist, 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), administered 30min prior to the test significantly and dose-dependently reversed the antidepressant effects of ketamine and LY341495, while NBQX itself had no effect on the immobility time. Our findings suggest that AMPA receptor stimulation at 24h after a single injection of ketamine or LY341495 is required to produce the anti-immobility effects of these compounds. Moreover, the present results provide additional evidence that an mGlu2/3 receptor antagonist may share some of neural mechanisms with ketamine to exert antidepressant effects.

  10. Synthetic and endogenous cannabinoids protect retinal neurons from AMPA excitotoxicity in vivo, via activation of CB1 receptors: Involvement of PI3K/Akt and MEK/ERK signaling pathways.

    PubMed

    Kokona, Despina; Thermos, Kyriaki

    2015-07-01

    Cannabinoids have been suggested to protect retinal ganglion cells in different models of toxicity, but their effects on other retinal neurons are poorly known. We investigated the neuroprotective actions of the endocannabinoid N-arachidonoyl ethanolamine (Anandamide/AEA) and the synthetic cannabinoids R1-Methanandamide (MethAEA) and HU-210, in an in vivo retinal model of AMPA excitotoxicity, and the mechanisms involved in the neuroprotection. Sprague-Dawley rats were intravitreally injected with PBS or AMPA in the absence or presence of the cannabinoid agonists. Brain nitric oxide synthase (bNOS) and choline acetyltransferase (ChAT) immunoreactivity (IR), as well as TUNEL staining, assessed the AMPA-induced retinal amacrine cell loss and the dose-dependent neuroprotection afforded by cannabinoids. The CB1 receptor selective antagonist AM251 and the PI3K/Akt inhibitor wortmannin reversed the cannabinoid-induced neuroprotection, suggesting the involvement of CB1 receptors and the PI3K/Akt pathway in cannabinoids' actions. Experiments with the CB2 agonist JWH015 and [(3)H]CP55940 radioligand binding suggested that the CB2 receptor is not involved in the neuroprotection. AEA and HU-210 induced phosphorylation of Akt but only AEA induced phosphorylation of ERK1/2 kinases, as revealed by western blot analysis. To investigate the role of caspase-3 in the AMPA-induced cell death, the caspase-3 inhibitor Z-DEVD-FMK was co-injected with AMPA. Z-DEVD-FMK had no effect on AMPA excitotoxicity. Moreover, no difference was observed in the phosphorylation of SAPK/JNK kinases between PBS- and AMPA-treated retinas. These results suggest that endogenous and synthetic cannabinoids protect retinal amacrine neurons from AMPA excitotoxicity in vivo via a mechanism involving the CB1 receptors, and the PI3K/Akt and/or MEK/ERK1/2 signaling pathways.

  11. Fragile X mental retardation protein control of neuronal mRNA metabolism: Insights into mRNA stability.

    PubMed

    De Rubeis, Silvia; Bagni, Claudia

    2010-01-01

    The fragile X mental retardation protein (FMRP) is an RNA binding protein that has an essential role in neurons. From the soma to the synapse, FMRP is associated with a specific subset of messenger RNAs and controls their posttranscriptional fates, i.e., dendritic localization and local translation. Because FMRP target mRNAs encode important neuronal proteins, the deregulation of their expression in the absence of FMRP leads to a strong impairment of synaptic function. Here, we review emerging evidence indicating a critical role for FMRP in the control of mRNA stability. To date, two mRNAs have been identified as being regulated in this manner: PSD-95 mRNA, encoding a scaffolding protein, and Nxf1 mRNA, encoding a general export factor. Moreover, expression studies suggest that the turnover of other neuronal mRNAs, including those encoding for the GABA(A) receptors subunits, could be affected by the loss of FMRP. According to the specific target and/or cellular context, FMRP could influence mRNA stability in the brain.

  12. Adult AMPA GLUA1 receptor subunit loss in 5-HT neurons results in a specific anxiety-phenotype with evidence for dysregulation of 5-HT neuronal activity.

    PubMed

    Weber, Tillmann; Vogt, Miriam A; Gartside, Sarah E; Berger, Stefan M; Lujan, Rafael; Lau, Thorsten; Herrmann, Elke; Sprengel, Rolf; Bartsch, Dusan; Gass, Peter

    2015-05-01

    Both the glutamatergic and serotonergic (5-HT) systems are implicated in the modulation of mood and anxiety. Descending cortical glutamatergic neurons regulate 5-HT neuronal activity in the midbrain raphe nuclei through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors. To analyze the functional role of GLUA1-containing AMPA receptors in serotonergic neurons, we used the Cre-ERT2/loxP-system for the conditional inactivation of the GLUA1-encoding Gria1 gene selectively in 5-HT neurons of adult mice. These Gria1(5-HT-/-) mice exhibited a distinct anxiety phenotype but showed no alterations in locomotion, depression-like behavior, or learning and memory. Increased anxiety-related behavior was associated with significant decreases in tryptophan hydroxylase 2 (TPH2) expression and activity, and subsequent reductions in tissue levels of 5-HT, its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and norepinephrine in the raphe nuclei. However, TPH2 expression and activity as well as monoamine levels were unchanged in the projection areas of 5-HT neurons. Extracellular electrophysiological recordings of 5-HT neurons revealed that, while α1-adrenoceptor-mediated excitation was unchanged, excitatory responses to AMPA were enhanced and the 5-HT1A autoreceptor-mediated inhibitory response to 5-HT was attenuated in Gria1(5-HT-/-) mice. Our data show that a loss of GLUA1 protein in 5-HT neurons enhances AMPA receptor function and leads to multiple local molecular and neurochemical changes in the raphe nuclei that dysregulate 5-HT neuronal activity and induce anxiety-like behavior.

  13. Occurrence of the herbicide glyphosate and its metabolite AMPA in surface waters in Switzerland determined with on-line solid phase extraction LC-MS/MS.

    PubMed

    Poiger, Thomas; Buerge, Ignaz J; Bächli, Astrid; Müller, Markus D; Balmer, Marianne E

    2017-01-01

    Glyphosate is currently one of the most important herbicides worldwide. Its unique properties provide for a wide range of uses in agriculture but also in non-agricultural areas. At the same time, its zwitterionic nature prevents the inclusion in multi-residue analytical methods for environmental monitoring. Consequently, despite its extensive use, data on occurrence of glyphosate in the aquatic environment is still scarce. Based on existing methods, we developed a simplified procedure for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water samples using derivatization with fluorenylmethyl chloroformate FMOC-Cl, combined with on-line solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. This method was extensively tested on over 1000 samples of surface water, groundwater, and treated wastewater and proved to be simple, sensitive, and reliable. Limits of quantification of 0.005 μg/L were routinely achieved. Glyphosate and AMPA were detected in the vast majority of stream water samples in the area of Zurich, Switzerland, with median concentrations of 0.11 and 0.20 μg/L and 95th percentile concentrations of 2.1 and 2.6 μg/L, respectively. Stream water data and data from treated wastewater indicated that non-agricultural uses may significantly contribute to the overall loads of glyphosate and AMPA in surface waters. In the investigated groundwater samples, selected specifically because they had shown presence of other herbicides in previous monitoring programs, glyphosate and AMPA were generally not detected, except for two monitoring sites in Karst aquifers, indicating that these compounds show much less tendency for leaching.

  14. Tianeptine potentiates AMPA receptors by activating CaMKII and PKA via the p38, p42/44 MAPK and JNK pathways.

    PubMed

    Szegedi, Viktor; Juhász, Gábor; Zhang, Xiaoqun; Barkóczi, Balázs; Qi, Hongshi; Madeira, Alexandra; Kapus, Gábor; Svenningsson, Per; Spedding, Michael; Penke, Botond

    2011-12-01

    Impairments of cellular plasticity appear to underlie the pathophysiology of major depression. Recently, elevated levels of phosphorylated AMPA receptor were implicated in the antidepressant effect of various drugs. Here, we investigated the effects of an antidepressant, Tianeptine, on synaptic function and GluA1 phosphorylation using murine hippocampal slices and in vivo single-unit recordings. Tianeptine, but not imipramine, increased AMPA receptor-mediated neuronal responses both in vitro and in vivo, in a staurosporine-sensitive manner. Paired-pulse ratio was unaltered by Tianeptine, suggesting a postsynaptic site of action. Tianeptine, 10 μM, enhanced the GluA1-dependent initial phase of LTP, whereas 100 μM impaired the latter phases, indicating a critical role of GluA1 subunit phosphorylation in the excitation. Tianeptine rapidly increased the phosphorylation level of Ser(831)-GluA1 and Ser(845)-GluA1. Using H-89 and KN-93, we show that the activation of both PKA and CaMKII is critical in the effect of Tianeptine on AMPA responses. Moreover, the phosphorylation states of Ser(217/221)-MEK and Thr(183)/Tyr(185)-p42MAPK were increased by Tianeptine and specific kinase blockers of the MAPK pathways (PD 98095, SB 203580 and SP600125) prevented the effects of Tianeptine. Overall these data suggest that Tianeptine potentiates several signaling cascades associated with synaptic plasticity and provide further evidence that a major mechanism of action for Tianeptine is to act as an enhancer of glutamate neurotransmission via AMPA receptors.

  15. The involvement of NMDA and AMPA receptors in the mechanism of antidepressant-like action of zinc in the forced swim test.

    PubMed

    Szewczyk, B; Poleszak, E; Sowa-Kućma, M; Wróbel, A; Słotwiński, S; Listos, J; Wlaź, P; Cichy, A; Siwek, A; Dybała, M; Gołembiowska, K; Pilc, A; Nowak, Gabriel

    2010-06-01

    Antidepressant-like activity of zinc in the forced swim test (FST) was demonstrated previously. Enhancement of such activity by joint administration of zinc and antidepressants was also shown. However, mechanisms involved in this activity have not yet been established. The present study examined the involvement of the NMDA and AMPA receptors in zinc activity in the FST in mice and rats. Additionally, the influence of zinc on both glutamate and aspartate release in the rat brain was also determined. Zinc-induced antidepressant-like activity in the FST in both mice and rats was antagonized by N-methyl-D-aspartic acid (NMDA, 75 mg/kg, i.p.) administration. Moreover, low and ineffective doses of NMDA antagonists (CGP 37849, L-701,324, D-cycloserine, and MK-801) administered together with ineffective doses of zinc exhibit a significant reduction of immobility time in the FST. Additionally, we have demonstrated the reduction of immobility time by AMPA receptor potentiator, CX 614. The antidepressant-like activity of both CX 614 and zinc in the FST was abolished by NBQX (an antagonist of AMPA receptor, 10 mg/kg, i.p.), while the combined treatment of sub-effective doses of zinc and CX 614 significantly reduces the immobility time in the FST. The present study also demonstrated that zinc administration potentiated a veratridine-evoked glutamate and aspartate release in the rat's prefrontal cortex and hippocampus. The present study further suggests the antidepressant properties of zinc and indicates the involvement of the NMDA and AMPA glutamatergic receptors in this activity.

  16. Water quality of the main tributaries of the Paraná Basin: glyphosate and AMPA in surface water and bottom sediments.

    PubMed

    Ronco, A E; Marino, D J G; Abelando, M; Almada, P; Apartin, C D

    2016-08-01

    The Paraná River, the sixth largest in the world, is the receptor of pollution loads from tributaries traversing urban and industrialized areas plus agricultural expanses, particularly so in the river's middle and lower reaches along the Argentine sector. In the present study, we analyzed and discussed the main water quality parameters, sediment compositions, and content of the herbicide glyphosate plus its metabolite aminomethylphosphonic acid (AMPA) in water and sediments. Samples were obtained from distal positions in the principal tributaries of the Paraná and the main watercourse during surveys conducted in 2011 and 2012 to monitor the basin. Only 15 % of the water samples contained detectable concentrations of glyphosate at an average concentration of 0.60 μg/L, while no detectable levels of AMPA were observed. The herbicide and metabolite were primarily present in sediments of the middle and lower stretch's tributaries, there occurring at a respective average of 37 and 17 % in samples. The mean detectable concentrations measured were 742 and 521 μg/kg at mean, maximum, and minimum glyphosate/AMPA ratios of 2.76, 7.80, and 0.06, respectively. The detection of both compounds was correlated with the presence of sulfides and copper in the sediment matrix.

  17. The Prefrontal Dectin-1/AMPA Receptor Signaling Pathway Mediates The Robust and Prolonged Antidepressant Effect of Proteo-β-Glucan from Maitake

    PubMed Central

    Bao, Hongkun; Ran, Pengzhan; Zhu, Ming; Sun, Lijuan; Li, Bai; Hou, Yangyang; Nie, Jun; Shan, Liping; Li, Hongliang; Zheng, Shangyong; Xu, Xiufeng; Xiao, Chunjie; Du, Jing

    2016-01-01

    Proteo-β-glucan from Maitake (PGM) is a strong immune regulator, and its receptor is called Dectin-1. Cumulative evidence suggests that AMPA receptors are important for the treatment of depression. Here, we report that PGM treatment leads to a significant antidepressant effect in the tail suspension test and forced swim test after sixty minutes of treatment in mice. After five consecutive days of PGM treatment, this antidepressant effect remained. PGM treatment did not show a hyperactive effect in the open field test. PGM significantly enhanced the expression of its receptor Dectin-1, as well as p-GluA1(S845) and GluA1, but not GluA2 or GluA3 in the prefrontal cortex (PFC) after five days of treatment. The Dectin-1 inhibitor Laminarin was able to block the antidepressant effect of PGM. At the synapses of PFC, PGM treatment significantly up-regulated the p-GluA1(S845), GluA1, GluA2, and GluA3 levels. Moreover, PGM’s antidepressant effects and the increase of p-GluA1(S845)/GluA1 lasted for 3 days after stopping treatment. The AMPA-specific antagonist GYKI 52466 was able to block the antidepressant effect of PGM. This study identified PGM as a novel antidepressant with clinical potential and a new antidepressant mechanism for regulating prefrontal Dectin-1/AMPA receptor signalling. PMID:27329257

  18. 5-HT(1A) and 5-HT(7) receptors differently modulate AMPA receptor-mediated hippocampal synaptic transmission.

    PubMed

    Costa, L; Trovato, C; Musumeci, S A; Catania, M V; Ciranna, L

    2012-04-01

    We have studied the effects of 5-HT(1A) and 5-HT(7) serotonin receptor activation in hippocampal CA3-CA1 synaptic transmission using patch clamp on mouse brain slices. Application of either 5-HT or 8-OH DPAT, a mixed 5-HT(1A)/5-HT(7) receptor agonist, inhibited AMPA receptor-mediated excitatory post synaptic currents (EPSCs); this effect was mimicked by the 5-HT(1A) receptor agonist 8-OH PIPAT and blocked by the 5-HT(1A) antagonist NAN-190. 8-OH DPAT increased paired-pulse facilitation and reduced the frequency of mEPSCs, indicating a presynaptic reduction of glutamate release probability. In another group of neurons, 8-OH DPAT enhanced EPSC amplitude but did not alter paired-pulse facilitation, suggesting a postsynaptic action; this effect persisted in the presence of NAN-190 and was blocked by the 5-HT(7) receptor antagonist SB-269970. To confirm that EPSC enhancement was mediated by 5-HT(7) receptors, we used the compound LP-44, which is considered a selective 5-HT(7) agonist. However, LP-44 reduced EPSC amplitude in most cells and instead increased EPSC amplitude in a subset of neurons, similarly to 8-OH DPAT. These effects were respectively antagonized by NAN-190 and by SB-269970, indicating that under our experimental condition LP-44 behaved as a mixed agonist. 8-OH DPAT also modulated the current evoked by exogenously applied AMPA, inducing either a reduction or an increase of amplitude in distinct neurons; these effects were respectively blocked by 5-HT(1A) and 5-HT(7) receptor antagonists, indicating that both receptors exert a postsynaptic action. Our results show that 5-HT(1A) receptors inhibit CA3-CA1 synaptic transmission acting both pre- and postsynaptically, whereas 5-HT(7) receptors enhance CA3-CA1 synaptic transmission acting exclusively at a postsynaptic site. We suggest that a selective pharmacological targeting of either subtype may be envisaged in pathological loss of hippocampal-dependent cognitive functions. In this respect, we underline the

  19. LY404187, a potentiator of AMPARs, enhances both the amplitude and 1/CV2 of AMPA EPSCs but not NMDA EPSCs at CA3-CA1 synapses in the hippocampus of neonatal rats.

    PubMed

    Song, Beomjong; Lee, Sukwon; Choi, Sukwoo

    2012-12-07

    Cyclothiazide is a well-known AMPAR potentiator, but it has also been shown to enhance the probability of presynaptic release in some cases. Interestingly, cyclothiazide has been shown to reveal AMPA EPSCs at silent CA3-CA1 synapses (which exhibit NMDA EPSCs but not AMPA EPSCs) in the hippocampus of neonatal or developing rats, but this particular result has not been reproduced at other types of synapses. Although this discrepancy may be due to the different mechanisms underlying silent synapses in distinct brain subregions, it is also possible that cyclothiazide has pre- and postsynaptic molecular targets that are differentially expressed at the different types (or different developing stages) of synapses. In this study, we reexamined, using a new AMPAR potentiator, LY404187, whether AMPAR potentiation leads to the conversion of silent CA3-CA1 synapses into functional synapses (exhibiting both AMPA and NMDA EPSCs) in the hippocampus of neonatal rats. LY404187 did not appear to alter the probability of presynaptic release, as evidenced by the lack of significant changes in both the amplitude and the paired-pulse facilitation ratio (an index of release probability) of NMDA EPSCs. LY404187 enhanced both the amplitude and 1/CV(2) (CV: coefficient of variation) of AMPA EPSCs but not NMDA EPSCs. Because an increase in 1/CV(2) reflects an increased number of functional synapses and/or an enhanced release probability, the LY404187-induced increase in the 1/CV(2) value of AMPA EPSCs, but not NMDA EPSCs, likely indicates an increased number of synapses exhibiting AMPA EPSCs but not an increased number of synapses exhibiting NMDA EPSCs. Because AMPARs and NMDARs are co-localized at the same synapses, our findings are consistent with a scenario in which LY404187 enables silent synapses to acquire AMPA EPSCs.

  20. Calcium-permeable AMPA receptors provide a common mechanism for LTP in glutamatergic synapses of distinct hippocampal interneuron types.

    PubMed

    Szabo, Andras; Somogyi, Jozsef; Cauli, Bruno; Lambolez, Bertrand; Somogyi, Peter; Lamsa, Karri P

    2012-05-09

    Glutamatergic synapses on some hippocampal GABAergic interneurons exhibit activity-induced long-term potentiation (LTP). Interneuron types within the CA1 area expressing mutually exclusive molecular markers differ in LTP responses. Potentiation that depends on calcium-permeable (CP) AMPA receptors has been characterized in oriens-lacunosum moleculare (O-LM) interneurons, which express parvalbumin and somatostatin (SM). However, it is unknown how widely CP-AMPAR-dependent plasticity is expressed among different GABAergic interneuron types. Here we examine synaptic plasticity in rat hippocampal O-LM cells and two other interneuron types expressing either nitric oxide synthase (NOS) or cholecystokinin (CCK), which are known to be physiologically and developmentally distinct. We report similar CP-AMPAR-dependent LTP in NOS-immunopositive ivy cells and SM-expressing O-LM cells to afferent fiber theta burst stimulation. The potentiation in both cell types is induced at postsynaptic membrane potentials below firing threshold, and induction is blocked by intense spiking simultaneously with afferent stimulation. The strong inward rectification and calcium permeability of AMPARs is explained by a low level of GluA2 subunit mRNA expression. LTP is not elicited in CCK-expressing Schaffer collateral-associated cells, which lack CP-AMPARs and express high levels of the GluA2 subunit. The results show that CP-AMPAR-mediated synaptic potentiation is common in hippocampal interneuron types and occurs in interneurons of both feedforward and feedback inhibitory pathways.

  1. Changes in hippocampal AMPA receptors and cognitive impairments in chronic ketamine addiction models: another understanding of ketamine CNS toxicity

    PubMed Central

    Ding, Runtao; Li, Yanning; Du, Ao; Yu, Hao; He, Bolin; Shen, Ruipeng; Zhou, Jichuan; Li, Lu; Cui, Wen; Zhang, Guohua; Lu, Yan; Wu, Xu

    2016-01-01

    Ketamine has been reported to impair human cognitive function as a recreational drug of abuse. However, chronic effects of ketamine on central nervous system need to be further explored. We set out to establish chronic ketamine addiction models by giving mice a three or six month course of daily intraperitoneal injections of ketamine, then examined whether long-term ketamine administration induced cognition deficits and changed hippocampal post-synaptic protein expression in adult mice. Behavior tests results showed that mice exhibited dose- and time-dependent learning and memory deficits after long-term ketamine administration. Western blot results showed levels of GluA1, p-S845 and p-S831 proteins demonstrated significant decline with ketamine 60 mg/kg until six months administration paradigm. But levels of p-S845 and p-S831 proteins exhibited obvious increase with ketamine 60 mg/kg three months administration paradigm. NR1 protein levels significantly decrease with ketamine 60 mg/kg three and six months administration paradigm. Our results indicate that reduced expression levels and decreased phosphorylation levels of hippocampal post-synaptic membrane GluA1- containing AMPA receptors maybe involved in cognition impairment after long-term ketamine administration. These findings provide further evidence for the cognitive damage of chronic ketamine addiction as a recreational drug. PMID:27934938

  2. Alteration of AMPA Receptor-Mediated Synaptic Transmission by Alexa Fluor 488 and 594 in Cerebellar Stellate Cells.

    PubMed

    Maroteaux, Matthieu; Liu, Siqiong June

    2016-01-01

    The fluorescent dyes, Alexa Fluor 488 and 594 are commonly used to visualize dendritic structures and the localization of synapses, both of which are critical for the spatial and temporal integration of synaptic inputs. However, the effect of the dyes on synaptic transmission is not known. Here we investigated whether Alexa Fluor dyes alter the properties of synaptic currents mediated by two subtypes of AMPA receptors (AMPARs) at cerebellar stellate cell synapses. In naive mice, GluA2-lacking AMPAR-mediated synaptic currents displayed an inwardly rectifying current-voltage (I-V) relationship due to blockade by cytoplasmic spermine at depolarized potentials. We found that the inclusion of 100 µm Alexa Fluor dye, but not 10 µm, in the pipette solution led to a gradual increase in the amplitude of EPSCs at +40 mV and a change in the I-V relationship from inwardly rectifying to more linear. In mice exposed to an acute stress, AMPARs switched to GluA2-containing receptors, and 100 µm Alexa Fluor 594 did not alter the I-V relationship of synaptic currents. Therefore, a high concentration of Alexa Fluor dye changed the I-V relationship of EPSCs at GluA2-lacking AMPAR synapses.

  3. TARP-associated AMPA receptors display an increased maximum channel conductance and multiple kinetically distinct open states.

    PubMed

    Shelley, Chris; Farrant, Mark; Cull-Candy, Stuart G

    2012-11-15

    Fast excitatory synaptic transmission in the CNS is mediated mainly by AMPA-type glutamate receptors (AMPARs), whose biophysical properties are dramatically modulated by the presence of transmembrane AMPAR regulatory proteins (TARPs). To help construct a kinetic model that will realistically describe native AMPAR/TARP function, we have examined the single-channel properties of homomeric GluA1 AMPARs in combination with the TARPs, γ-2, γ-4 and γ-5. In a saturating concentration of agonist, each of these AMPAR/TARP combinations gave rise to single-channel currents with multiple conductance levels that appeared intrinsic to the receptor-channel complex, and showed long-lived subconductance states. The open time and burst length distributions of the receptor complexes displayed multiple dwell-time components. In the case of γ-2- and γ-4-associated receptors, these distributions included a long-lived component lasting tens of milliseconds that was absent from both GluA1 alone and γ-5-associated receptors. The open time distributions for each conductance level required two dwell-time components, indicating that at each conductance level the channel occupies a minimum of two kinetically distinct open states. We have explored how these data place novel constraints on possible kinetic models of TARP-associated AMPARs that may be used to define AMPAR-mediated synaptic transmission.

  4. Alteration of AMPA Receptor-Mediated Synaptic Transmission by Alexa Fluor 488 and 594 in Cerebellar Stellate Cells123

    PubMed Central

    2016-01-01

    Abstract The fluorescent dyes, Alexa Fluor 488 and 594 are commonly used to visualize dendritic structures and the localization of synapses, both of which are critical for the spatial and temporal integration of synaptic inputs. However, the effect of the dyes on synaptic transmission is not known. Here we investigated whether Alexa Fluor dyes alter the properties of synaptic currents mediated by two subtypes of AMPA receptors (AMPARs) at cerebellar stellate cell synapses. In naive mice, GluA2-lacking AMPAR-mediated synaptic currents displayed an inwardly rectifying current–voltage (I–V) relationship due to blockade by cytoplasmic spermine at depolarized potentials. We found that the inclusion of 100 µm Alexa Fluor dye, but not 10 µm, in the pipette solution led to a gradual increase in the amplitude of EPSCs at +40 mV and a change in the I–V relationship from inwardly rectifying to more linear. In mice exposed to an acute stress, AMPARs switched to GluA2-containing receptors, and 100 µm Alexa Fluor 594 did not alter the I–V relationship of synaptic currents. Therefore, a high concentration of Alexa Fluor dye changed the I–V relationship of EPSCs at GluA2-lacking AMPAR synapses. PMID:27280156

  5. Activation of AMPA receptor in the infralimbic cortex facilitates extinction and attenuates the heroin-seeking behavior in rats.

    PubMed

    Chen, Weisheng; Wang, Yiqi; Sun, Anna; Zhou, Linyi; Xu, Wenjin; Zhu, Huaqiang; Zhuang, Dingding; Lai, Miaojun; Zhang, Fuqiang; Zhou, Wenhua; Liu, Huifen

    2016-01-26

    Infralimbic cortex (IL) is proposed to suppress cocaine seeking after extinction, but whether the IL regulates the extinction and reinstatement of heroin-seeking behavior is unknown. To address this issue, the male SD rats were trained to self-administer heroin under a FR1 schedule for consecutive 14 days, then the rats underwent 7 daily 2h extinction session in the operant chamber. The activation of IL by microinjection PEPA, an allosteric AMPA receptor potentiator into IL before each of extinction session facilitated the extinction responding after heroin self-administration, but did not alter the locomotor activity in an open field testing environment. Other rats were first trained under a FR1 schedule for heroin self-administration for 14 days, followed by 14 days of extinction training, and reinstatement of heroin-seeking induced by cues was measured for 2h. Intra-IL microinjecting of PEPA at 15min prior to test inhibited the reinstatement of heroin-seeking induced by cues. Moreover, the expression of GluR1 in the IL and NAc remarkably increased after treatment with PEPA during the reinstatement. These finding suggested that activation of glutamatergic projection from IL to NAc shell may be involved in the extinction and reinstatement of heroin-seeking.

  6. Non-fibrillar amyloid-{beta} peptide reduces NMDA-induced neurotoxicity, but not AMPA-induced neurotoxicity

    SciTech Connect

    Niidome, Tetsuhiro; Goto, Yasuaki; Kato, Masaru; Wang, Pi-Lin; Goh, Saori; Tanaka, Naoki; Akaike, Akinori; Kihara, Takeshi; Sugimoto, Hachiro

    2009-09-04

    Amyloid-{beta} peptide (A{beta}) is thought to be linked to the pathogenesis of Alzheimer's disease. Recent studies suggest that A{beta} has important physiological roles in addition to its pathological roles. We recently demonstrated that A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity, but the relationship between A{beta}42 assemblies and their neuroprotective effects remains largely unknown. In this study, we prepared non-fibrillar and fibrillar A{beta}42 based on the results of the thioflavin T assay, Western blot analysis, and atomic force microscopy, and examined the effects of non-fibrillar and fibrillar A{beta}42 on glutamate-induced neurotoxicity. Non-fibrillar A{beta}42, but not fibrillar A{beta}42, protected hippocampal neurons from glutamate-induced neurotoxicity. Furthermore, non-fibrillar A{beta}42 decreased both neurotoxicity and increases in the intracellular Ca{sup 2+} concentration induced by N-methyl-D-aspartate (NMDA), but not by {alpha}-amino-3-hydrozy-5-methyl-4-isoxazole propionic acid (AMPA). Our results suggest that non-fibrillar A{beta}42 protects hippocampal neurons from glutamate-induced neurotoxicity through regulation of the NMDA receptor.

  7. Alterations in Hippocampal Oxidative Stress, Expression of AMPA Receptor GluR2 Subunit and Associated Spatial Memory Loss by Bacopa monnieri Extract (CDRI-08) in Streptozotocin-Induced Diabetes Mellitus Type 2 Mice.

    PubMed

    Pandey, Surya P; Singh, Hemant K; Prasad, S

    2015-01-01

    Bacopa monnieri extract has been implicated in the recovery of memory impairments due to various neurological disorders in animal models and humans. However, the precise molecular mechanism of the role of CDRI-08, a well characterized fraction of Bacopa monnieri extract, in recovery of the diabetes mellitus-induced memory impairments is not known. Here, we demonstrate that DM2 mice treated orally with lower dose of CDRI-08 (50- or 100 mg/kg BW) is able to significantly enhance spatial memory in STZ-DM2 mice and this is correlated with a significant decline in oxidative stress and up regulation of the AMPA receptor GluR2 subunit gene expression in the hippocampus. Treatment of DM2 mice with its higher dose (150 mg/kg BW or above) shows anti-diabetic effect in addition to its ability to recover the spatial memory impairment by reversing the DM2-induced elevated oxidative stress and decreased GluR2 subunit expression near to their values in normal and CDRI-08 treated control mice. Our results provide evidences towards molecular basis of the memory enhancing and anti diabetic role of the Bacopa monnieri extract in STZ-induced DM2 mice, which may have therapeutic implications.

  8. Alterations in Hippocampal Oxidative Stress, Expression of AMPA Receptor GluR2 Subunit and Associated Spatial Memory Loss by Bacopa monnieri Extract (CDRI-08) in Streptozotocin-Induced Diabetes Mellitus Type 2 Mice

    PubMed Central

    Pandey, Surya P.; Singh, Hemant K.; Prasad, S.

    2015-01-01

    Bacopa monnieri extract has been implicated in the recovery of memory impairments due to various neurological disorders in animal models and humans. However, the precise molecular mechanism of the role of CDRI-08, a well characterized fraction of Bacopa monnieri extract, in recovery of the diabetes mellitus-induced memory impairments is not known. Here, we demonstrate that DM2 mice treated orally with lower dose of CDRI-08 (50- or 100 mg/kg BW) is able to significantly enhance spatial memory in STZ-DM2 mice and this is correlated with a significant decline in oxidative stress and up regulation of the AMPA receptor GluR2 subunit gene expression in the hippocampus. Treatment of DM2 mice with its higher dose (150 mg/kg BW or above) shows anti-diabetic effect in addition to its ability to recover the spatial memory impairment by reversing the DM2-induced elevated oxidative stress and decreased GluR2 subunit expression near to their values in normal and CDRI-08 treated control mice. Our results provide evidences towards molecular basis of the memory enhancing and anti diabetic role of the Bacopa monnieri extract in STZ-induced DM2 mice, which may have therapeutic implications. PMID:26161865

  9. High-resolution immunogold localization of AMPA type glutamate receptor subunits at synaptic and non-synaptic sites in rat hippocampus.

    PubMed

    Baude, A; Nusser, Z; Molnár, E; McIlhinney, R A; Somogyi, P

    1995-12-01

    The cellular and subcellular localization of the GluRA, GluRB/C and GluRD subunits of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type glutamate receptor was determined in the rat hippocampus using polyclonal antipeptide antibodies in immunoperoxidase and immunogold procedures. For the localization of the GluRD subunit a new polyclonal antiserum was developed using the C-terminal sequence of the protein (residues 869-881), conjugated to carrier protein and absorbed to colloidal gold for immunization. The purified antibodies immunoprecipitated about 25% of 3[H]AMPA binding activity from the hippocampus, cerebellum or whole brain, but very little from neocortex. These antibodies did not precipitate a significant amount of 3[H]kainate binding activity. The antibodies also recognize the GluRD subunit, but not the other AMPA receptor subunits, when expressed in transfected COS-7 cells and only when permeabilized with detergent, indicating an intracellular epitope. All subunits were enriched in the neuropil of the dendritic layers of the hippocampus and in the molecular layer of the dentate gyrus. The cellular distribution of the GluRD subunit was studied more extensively. The strata radiatum, oriens and the dentate molecular layer were more strongly immunoreactive than the stratum lacunosum moleculare, the stratum lucidum and the hilus. However, in the stratum lucidum of the CA3 area and in the hilus the weakly reacting dendrites were surrounded by immunopositive rosettes, shown in subsequent electron microscopic studies to correspond to complex dendritic spines. In the stratum radiatum, the weakly reacting apical dendrites contrasted with the surrounding intensely stained neuropil. The cell bodies of pyramidal and granule cells were moderately reactive. Some non-principal cells and their dendrites in the pyramidal cell layer and in the alveus also reacted very strongly for the GluRD subunit. At the subcellular level, silver intensified immunogold

  10. AMPA receptor subunits are differentially expressed in parvalbumin- and calretinin-positive neurons of the rat hippocampus.

    PubMed

    Catania, M V; Bellomo, M; Giuffrida, R; Giuffrida, R; Stella, A M; Albanese, V

    1998-11-01

    Recent studies suggest a functional diversity of native alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate-type glutamate receptor channels (AMPARs). In several types of interneurons, AMPARs are characterized by higher Ca2+ permeability and faster kinetics than AMPARs in principal cells. We studied the expression profile of AMPAR subunits in the hippocampal parvalbumin (PV)- and calretinin (CR)-positive cells, which represent different populations of non-principal cells. To this end, non-radioactive in situ hybridization with AMPAR subunit specific cRNAs was combined with immunocytochemistry for PV or CR. Double-immunolabelling using antibodies against AMPAR subunits and PV or CR was also performed. PV-containing neurons represent a fairly homogeneous population of cells expressing high levels of GluR-A and GluR-D mRNAs, moderate levels of GluR-C and low levels of GluR-B mRNAs in all the examined regions of hippocampus. The vast majority of CR-containing cells have a much lower expression of GluR-A, -C and -D mRNA than PV-positive neurons, although similarly featuring low levels of GluR-B mRNA. Only a subpopulation of CR-containing cells, the spiny neurons of the dentate gyrus and CA3 region of the hippocampus were characterized by a strong expression of GluR-A and -D subunit mRNAs. The differential pattern found for the AMPAR subunit mRNA expression was confirmed by immunocytochemistry at protein level. Despite the common feature of low GluR-B subunit expression, PV- and CR-containing interneurons differ with respect to the density and combination of their expressed AMPAR subunits. The different combination of subunits might subserve different properties of the AMPA channels featured by these cell types, with implications for the functioning of the hippocampal network.

  11. AMPA Receptor Phosphorylation and Synaptic Colocalization on Motor Neurons Drive Maladaptive Plasticity below Complete Spinal Cord Injury

    PubMed Central

    Stuck, Ellen D.; Irvine, Karen-Amanda; Bresnahan, Jacqueline C.

    2015-01-01

    Abstract Clinical spinal cord injury (SCI) is accompanied by comorbid peripheral injury in 47% of patients. Human and animal modeling data have shown that painful peripheral injuries undermine long-term recovery of locomotion through unknown mechanisms. Peripheral nociceptive stimuli induce maladaptive synaptic plasticity in dorsal horn sensory systems through AMPA receptor (AMPAR) phosphorylation and trafficking to synapses. Here we test whether ventral horn motor neurons in rats demonstrate similar experience-dependent maladaptive plasticity below a complete SCI in vivo. Quantitative biochemistry demonstrated that intermittent nociceptive stimulation (INS) rapidly and selectively increases AMPAR subunit GluA1 serine 831 phosphorylation and localization to synapses in the injured spinal cord, while reducing synaptic GluA2. These changes predict motor dysfunction in the absence of cell death signaling, suggesting an opportunity for therapeutic reversal. Automated confocal time-course analysis of lumbar ventral horn motor neurons confirmed a time-dependent increase in synaptic GluA1 with concurrent decrease in synaptic GluA2. Optical fractionation of neuronal plasma membranes revealed GluA2 removal from extrasynaptic sites on motor neurons early after INS followed by removal from synapses 2 h later. As GluA2-lacking AMPARs are canonical calcium-permeable AMPARs (CP-AMPARs), their stimulus- and time-dependent insertion provides a therapeutic target for limiting calcium-dependent dynamic maladaptive plasticity after SCI. Confirming this, a selective CP-AMPAR antagonist protected against INS-induced maladaptive spinal plasticity, restoring adaptive motor responses on a sensorimotor spinal training task. These findings highlight the critical involvement of AMPARs in experience-dependent spinal cord plasticity after injury and provide a pharmacologically targetable synaptic mechanism by which early postinjury experience shapes motor plasticity. PMID:26668821

  12. Stargazin (TARP gamma-2) is required for compartment-specific AMPA receptor trafficking and synaptic plasticity in cerebellar stellate cells.

    PubMed

    Jackson, Alexander C; Nicoll, Roger A

    2011-03-16

    In the cerebellar cortex, parallel fiber-to-stellate cell (PF-SC) synapses exhibit a form of synaptic plasticity manifested as a switch in the subunit composition of synaptic AMPA receptors (AMPARs) from calcium-permeable, GluA2-lacking to calcium-impermeable, GluA2-containing receptors. Here, we examine the role of stargazin (γ-2), canonical member of the transmembrane AMPAR regulatory protein (TARP) family, in the regulation of GluA2-lacking AMPARs and synaptic plasticity in SCs from epileptic and ataxic stargazer mutant mice. We found that AMPAR-mediated synaptic transmission is severely diminished in stargazer SCs, and that the rectification index (RI) of AMPAR current is reduced. Activity-dependent plasticity in the rectification of synaptic AMPARs is also impaired in stargazer SCs. Despite the dramatic loss in synaptic AMPARs, extrasynaptic AMPARs are preserved. We then examined the role of stargazin in regulating the rectification of extrasynaptic AMPARs in nucleated patches and found, in contrast to previous reports, that wild-type extrasynaptic AMPARs have moderate RI values (average RI = 0.38), while those in stargazer SCs are low (average RI = 0.24). The GluA2-lacking AMPAR blocker, philanthotoxin-433 (PhTx-433), was used as an alternative measure of GluA2 content in wild-type and stargazer SCs. Despite the difference in RI, PhTx-433 sensitivity of both synaptic and extrasynaptic AMPARs remains unchanged, suggesting that the dramatic changes in RI and the impairment in synaptic plasticity observed in the stargazer mouse are not the result of a specific impairment in GluA2 trafficking. Together, these data suggest that stargazin regulates compartment-specific AMPAR trafficking, as well as activity-dependent plasticity in synaptic AMPAR rectification at cerebellar PF-SC synapses.

  13. Molecular mechanisms contributing to TARP regulation of channel conductance and polyamine block of calcium-permeable AMPA receptors.

    PubMed

    Soto, David; Coombs, Ian D; Gratacòs-Batlle, Esther; Farrant, Mark; Cull-Candy, Stuart G

    2014-08-27

    Many properties of fast synaptic transmission in the brain are influenced by transmembrane AMPAR regulatory proteins (TARPs) that modulate the pharmacology and gating of AMPA-type glutamate receptors (AMPARs). Although much is known about TARP influence on AMPAR pharmacology and kinetics through their modulation of the extracellular ligand-binding domain (LBD), less is known about their regulation of the ion channel region. TARP-induced modifications in AMPAR channel behavior include increased single-channel conductance and weakened block of calcium-permeable AMPARs (CP-AMPARs) by endogenous intracellular polyamines. To investigate how TARPs modify ion flux and channel block, we examined the action of γ-2 (stargazin) on GluA1 and GluA4 CP-AMPARs. First, we compared the permeation of organic cations of different sizes. We found that γ-2 increased the permeability of several cations but not the estimated AMPAR pore size, suggesting that TARP-induced relief of polyamine block does not reflect altered pore diameter. Second, to determine whether residues in the TARP intracellular C-tail regulate polyamine block and channel conductance, we examined various γ-2 C-tail mutants. We identified the membrane proximal region of the C terminus as crucial for full TARP-attenuation of polyamine block, whereas complete deletion of the C-tail markedly enhanced the TARP-induced increase in channel conductance; thus, the TARP C-tail influences ion permeation. Third, we identified a site in the pore-lining region of the AMPAR, close to its Q/R site, that is crucial in determining the TARP-induced changes in single-channel conductance. This conserved residue represents a site of TARP action, independent of the AMPAR LBD.

  14. Nicotine and ethanol cooperate to enhance ventral tegmental area AMPA receptor function via α6-containing nicotinic receptors.

    PubMed

    Engle, Staci E; McIntosh, J Michael; Drenan, Ryan M

    2015-04-01

    Nicotine + ethanol co-exposure results in additive and/or synergistic effects in the ventral tegmental area (VTA) to nucleus accumbens (NAc) dopamine (DA) pathway, but the mechanisms supporting this are unclear. We tested the hypothesis that nAChRs containing α6 subunits (α6* nAChRs) are involved in the response to nicotine + ethanol co-exposure. Exposing VTA slices from C57BL/6 WT animals to drinking-relevant concentrations of ethanol causes a marked enhancement of α-amino-3-hydroxy-5-methyl-isoxazolepropionic acid (AMPA) receptor (AMPAR) function in VTA neurons. This effect was sensitive to α-conotoxin MII (an α6β2* nAChR antagonist), suggesting that α6* nAChR function is required. In mice expressing hypersensitive α6* nAChRs (α6L9S mice), we found that lower concentrations (relative to C57BL/6 WT) of ethanol were sufficient to enhance AMPAR function in VTA neurons. Exposure of live C57BL/6 WT mice to ethanol also produced AMPAR functional enhancement in VTA neurons, and studies in α6L9S mice strongly suggest a role for α6* nAChRs in this response. We then asked whether nicotine and ethanol cooperate to enhance VTA AMPAR function. We identified low concentrations of nicotine and ethanol that were capable of strongly enhancing VTA AMPAR function when co-applied to slices, but that did not enhance AMPAR function when applied alone. This effect was sensitive to both varenicline (an α4β2* and α6β2* nAChR partial agonist) and α-conotoxin MII. Finally, nicotine + ethanol co-exposure also enhanced AMPAR function in VTA neurons from α6L9S mice. Together, these data identify α6* nAChRs as important players in the response to nicotine + ethanol co-exposure in VTA neurons.

  15. Molecular Mechanisms Contributing to TARP Regulation of Channel Conductance and Polyamine Block of Calcium-Permeable AMPA Receptors

    PubMed Central

    Coombs, Ian D.; Gratacòs-Batlle, Esther

    2014-01-01

    Many properties of fast synaptic transmission in the brain are influenced by transmembrane AMPAR regulatory proteins (TARPs) that modulate the pharmacology and gating of AMPA-type glutamate receptors (AMPARs). Although much is known about TARP influence on AMPAR pharmacology and kinetics through their modulation of the extracellular ligand-binding domain (LBD), less is known about their regulation of the ion channel region. TARP-induced modifications in AMPAR channel behavior include increased single-channel conductance and weakened block of calcium-permeable AMPARs (CP-AMPARs) by endogenous intracellular polyamines. To investigate how TARPs modify ion flux and channel block, we examined the action of γ-2 (stargazin) on GluA1 and GluA4 CP-AMPARs. First, we compared the permeation of organic cations of different sizes. We found that γ-2 increased the permeability of several cations but not the estimated AMPAR pore size, suggesting that TARP-induced relief of polyamine block does not reflect altered pore diameter. Second, to determine whether residues in the TARP intracellular C-tail regulate polyamine block and channel conductance, we examined various γ-2 C-tail mutants. We identified the membrane proximal region of the C terminus as crucial for full TARP-attenuation of polyamine block, whereas complete deletion of the C-tail markedly enhanced the TARP-induced increase in channel conductance; thus, the TARP C-tail influences ion permeation. Third, we identified a site in the pore-lining region of the AMPAR, close to its Q/R site, that is crucial in determining the TARP-induced changes in single-channel conductance. This conserved residue represents a site of TARP action, independent of the AMPAR LBD. PMID:25164663

  16. Cell class-specific regulation of neocortical dendrite and spine growth by AMPA receptor splice and editing variants.

    PubMed

    Hamad, Mohammad I K; Ma-Högemeier, Zhan-Lu; Riedel, Christian; Conrads, Claudius; Veitinger, Thomas; Habijan, Tim; Schulz, Jan-Niklas; Krause, Martin; Wirth, Marcus J; Hollmann, Michael; Wahle, Petra

    2011-10-01

    Glutamatergic transmission converging on calcium signaling plays a key role in dendritic differentiation. In early development, AMPA receptor (AMPAR) transcripts are extensively spliced and edited to generate subunits that differ in their biophysical properties. Whether these subunits have specific roles in the context of structural differentiation is unclear. We have investigated the role of nine GluA variants and revealed a correlation between the expression of flip variants and the period of major dendritic growth. In interneurons, only GluA1(Q)-flip increased dendritic length and branching. In pyramidal cells, GluA2(Q)-flop, GluA2(Q)-flip, GluA3(Q)-flip and calcium-impermeable GluA2(R)-flip promoted dendritic growth, suggesting that flip variants with slower desensitization kinetics are more important than receptors with elevated calcium permeability. Imaging revealed significantly higher calcium signals in pyramidal cells transfected with GluA2(R)-flip as compared with GluA2(R)-flop, suggesting a contribution of voltage-activated calcium channels. Indeed, dendritic growth induced by GluA2(R)-flip in pyramidal cells was prevented by blocking NMDA receptors (NMDARs) or voltage-gated calcium channels (VGCCs), suggesting that they act downstream of AMPARs. Intriguingly, the action of GluA1(Q)-flip in interneurons was also dependent on NMDARs and VGCCs. Cell class-specific effects were not observed for spine formation, as GluA2(Q)-flip and GluA2(Q)-flop increased spine density in pyramidal cells as well as in interneurons. The results suggest that AMPAR variants expressed early in development are important determinants for activity-dependent dendritic growth in a cell type-specific and cell compartment-specific manner.

  17. BDNF contributes to both rapid and homeostatic alterations in AMPA receptor surface expression in nucleus accumbens medium spiny neurons

    PubMed Central

    Reimers, Jeremy M.; Loweth, Jessica A.; Wolf, Marina E.

    2015-01-01

    Brain-derived neurotrophic factor (BDNF) plays a critical role in plasticity at glutamate synapses and the effects of repeated cocaine exposure. We recently showed that intracranial injection of BDNF into the rat nucleus accumbens (NAc), a key region for cocaine addiction, rapidly increases AMPA receptor (AMPAR) surface expression. To further characterize BDNF’s role in both rapid AMPAR trafficking and slower, homeostatic changes in AMPAR surface expression, we investigated the effects of acute (30 min) and long-term (24 h) treatment with BDNF on AMPAR distribution in NAc medium spiny neurons from postnatal rats co-cultured with mouse prefrontal cortex (PFC) neurons to restore excitatory inputs. Immunocytochemical studies showed that acute BDNF treatment increased cell surface GluA1 and GluA2 levels, as well as their co-localization, on NAc neurons. This effect of BDNF, confirmed using a protein crosslinking assay, was dependent on ERK but not AKT signaling. In contrast, long-term BDNF treatment decreased AMPAR surface expression on NAc neurons. Based on this latter result, we tested the hypothesis that BDNF plays a role in AMPAR “scaling down” in response to a prolonged increase in neuronal activity produced by bicuculline (24 h). Supporting this hypothesis, decreasing BDNF signaling with the extracellular BDNF scavenger TrkB-Fc prevented the scaling down of GluA1 and GluA2 surface levels in NAc neurons normally produced by bicuculline. In conclusion, BDNF exerts bidirectional effects on NAc AMPAR surface expression, depending on duration of exposure. Furthermore, BDNF’s involvement in synaptic scaling in the NAc differs from its previously described role in the visual cortex. PMID:24712995

  18. AMPA Receptor Phosphorylation and Synaptic Colocalization on Motor Neurons Drive Maladaptive Plasticity below Complete Spinal Cord Injury.

    PubMed

    Huie, J Russell; Stuck, Ellen D; Lee, Kuan H; Irvine, Karen-Amanda; Beattie, Michael S; Bresnahan, Jacqueline C; Grau, James W; Ferguson, Adam R

    2015-01-01

    Clinical spinal cord injury (SCI) is accompanied by comorbid peripheral injury in 47% of patients. Human and animal modeling data have shown that painful peripheral injuries undermine long-term recovery of locomotion through unknown mechanisms. Peripheral nociceptive stimuli induce maladaptive synaptic plasticity in dorsal horn sensory systems through AMPA receptor (AMPAR) phosphorylation and trafficking to synapses. Here we test whether ventral horn motor neurons in rats demonstrate similar experience-dependent maladaptive plasticity below a complete SCI in vivo. Quantitative biochemistry demonstrated that intermittent nociceptive stimulation (INS) rapidly and selectively increases AMPAR subunit GluA1 serine 831 phosphorylation and localization to synapses in the injured spinal cord, while reducing synaptic GluA2. These changes predict motor dysfunction in the absence of cell death signaling, suggesting an opportunity for therapeutic reversal. Automated confocal time-course analysis of lumbar ventral horn motor neurons confirmed a time-dependent increase in synaptic GluA1 with concurrent decrease in synaptic GluA2. Optical fractionation of neuronal plasma membranes revealed GluA2 removal from extrasynaptic sites on motor neurons early after INS followed by removal from synapses 2 h later. As GluA2-lacking AMPARs are canonical calcium-permeable AMPARs (CP-AMPARs), their stimulus- and time-dependent insertion provides a therapeutic target for limiting calcium-dependent dynamic maladaptive plasticity after SCI. Confirming this, a selective CP-AMPAR antagonist protected against INS-induced maladaptive spinal plasticity, restoring adaptive motor responses on a sensorimotor spinal training task. These findings highlight the critical involvement of AMPARs in experience-dependent spinal cord plasticity after injury and provide a pharmacologically targetable synaptic mechanism by which early postinjury experience shapes motor plasticity.

  19. Cellular distribution of AMPA receptor subunits and mGlu5 following acute and repeated administration of morphine or methamphetamine.

    PubMed

    Herrold, Amy A; Persons, Amanda L; Napier, T Celeste

    2013-08-01

    Ionotropic AMPA receptors (AMPAR) and metabotropic glutamate group I subtype 5 receptors (mGlu5) mediate neuronal and behavioral effects of abused drugs. mGlu5 stimulation increases expression of striatal-enriched tyrosine phosphatase isoform 61 (STEP61 ) which internalizes AMPARs. We determined the rat brain profile of these proteins using two different classes of abused drugs, opiates, and stimulants. STEP61 levels, and cellular distribution/expression of AMPAR subunits (GluA1, GluA2) and mGlu5, were evaluated via a protein cross-linking assay in medial prefrontal cortex (mPFC), nucleus accumbens (NAc), and ventral pallidum (VP) harvested 1 day after acute, or fourteen days after repeated morphine (8 mg/kg) or methamphetamine (1 mg/kg) (treatments producing behavioral sensitization). Acute morphine decreased GluA1 and GluA2 surface expression in mPFC and GluA1 in NAc. Fourteen days after repeated morphine or methamphetamine, mGlu5 surface expression increased in VP. In mPFC, mGlu5 were unaltered; however, after methamphetamine, STEP61 levels decreased and GluA2 surface expression increased. Pre-treatment with a mGlu5-selective negative allosteric modulator, blocked methamphetamine-induced behavioral sensitization and changes in mPFC GluA2 and STEP61 . These data reveal (i) region-specific distinctions in glutamate receptor trafficking between acute and repeated treatments of morphine and methamphetamine, and (ii) that mGlu5 is necessary for methamphetamine-induced alterations in mPFC GluA2 and STEP61 .

  20. Loss of Ca(2+)-permeable AMPA receptors in synapses of tonic firing substantia gelatinosa neurons in the chronic constriction injury model of neuropathic pain.

    PubMed

    Chen, Yishen; Derkach, Victor A; Smith, Peter A

    2016-05-01

    Synapses transmitting nociceptive information in the spinal dorsal horn undergo enduring changes following peripheral nerve injury. Indeed, such injury alters the expression of the GluA2 subunit of glutamatergic AMPA receptors (AMPARs) in the substantia gelatinosa and this predicts altered channel conductance and calcium permeability, leading to an altered function of excitatory synapses. We therefore investigated the functional properties of synaptic AMPA receptors in rat substantia gelatinosa neurons following 10-20d chronic constriction injury (CCI) of the sciatic nerve; a model of neuropathic pain. We measured their single-channel conductance and sensitivity to a blocker of calcium permeable AMPA receptors (CP-AMPARs), IEM1460 (50μM). In putative inhibitory, tonic firing neurons, CCI reduced the average single-channel conductance of synaptic AMPAR from 14.4±3.5pS (n=12) to 9.2±1.0pS (n=10, p<0.05). IEM1460 also more effectively antagonized evoked, spontaneous and miniature EPSCs in tonic neurons from sham operated animals than in those from animals that had been subjected to CCI. By contrast, CCI did not change the effectiveness of IEM1460 in delay firing neurons although average single channel conductance was increased from 7.6±1.2pS (n=11) to 12.2±1.5pS (n=10, p<0.01). CCI thus elicits plastic changes in a specific set of glutamatergic synapses of substantia gelatinosa due to subunit recomposition and loss of GluA2-lacking CP-AMPAR. These insights reveal a molecular mechanism of nerve injury acting at synapses of inhibitory neurons to reduce their drive and therefore inhibitory tone in the spinal cord, therefore contributing to the central sensitization associated with neuropathic pain.

  1. Factors affecting the fate and transport of glyphosate and AMPA into surface waters of agricultural watersheds in the United States and Europe

    NASA Astrophysics Data System (ADS)

    Coupe, R.; Kalkhoff, S.; Capel, P.; Gregoire, C.

    2012-04-01

    Glyphosate [N-(phosphonomethyl)glycine] is a herbicide used extensively in almost all agricultural and urban areas of the United States and Europe. Although, glyphosate is used widely throughout the world in the production of many crops, it is predominately used in the United States on soybeans, corn, potatoes, and cotton that have been genetically modified to be tolerant to glyphosate. From 1992 to 2007, the agricultural use of glyphosate has increased from less than 10,000 Mg to more than 80,000 Mg, respectively. The greatest areal use is in the midwestern United States where glyphosate is applied on transgenic corn and soybeans. Because of the difficulty and expense in analyzing for glyphosate and AMPA (aminomethylphosphonic acid, a primary glyphosate degradate) in water, there have been only small scale studies on the fate and transport of glyphosate. The characterization of the transport of glyphosate and AMPA on a watershed scale is lacking. Glyphosate and AMPA were frequently detected in the surface waters of 4 agricultural watersheds in studies conducted by the U.S. Geological Survey in the United States and at the Laboratory of Hydrology and Geochemistry of Strasbourg. Two of these basins were located in the midwestern United States where the major crops are corn and soybean, the third is located the lower Mississippi River Basin where the major crops are soybean, corn, rice, and cotton, and the fourth was located near Strasbourg, France where the use of glyphosate was on a vineyard. The load as a percent of use ranged from 0.009 to 0.86 percent and could be related to 3 factors: source strength, hydrology, and flowpath. Glyphosate use in a watershed results in some occurrence in surface water at the part per billion level; however, those watersheds most at risk for the offsite transport of glyphosate are those with high application rates, rainfall that results in overland runoff, and a flowpath that does not include transport through the soil.

  2. The antidepressant-like effects of glutamatergic drugs ketamine and AMPA receptor potentiator LY 451646 are preserved in bdnf⁺/⁻ heterozygous null mice.

    PubMed

    Lindholm, Jesse S O; Autio, Henri; Vesa, Liisa; Antila, Hanna; Lindemann, Lothar; Hoener, Marius C; Skolnick, Phil; Rantamäki, Tomi; Castrén, Eero

    2012-01-01

    Accumulating evidence suggests that biogenic amine-based antidepressants act, at least in part, via regulation of brain-derived neurotrophic factor (BDNF) signaling. Biogenic amine-based antidepressants increase BDNF synthesis and activate its signaling pathway through TrkB receptors. Moreover, the antidepressant-like effects of these molecules are abolished in BDNF deficient mice. Glutamate-based drugs, including the NMDA antagonist ketamine, and the AMPA receptor potentiator LY 451646, mimic the effects of antidepressants in preclinical tests with high predictive validity. In humans, a single intravenous dose of ketamine produces an antidepressant effect that is rapid, robust and persistent. In this study, we examined the role of BDNF in expression of the antidepressant-like effects of ketamine and an AMPA receptor potentiator (LY 451646) in the forced swim test (FST). Ketamine and LY 451646 produced antidepressant-like effects in the FST in mice at 45 min after a single injection, but no effects were observed one week after a single ketamine injection. As previously reported, the effects of imipramine in the forced swim test were blunted in heterozygous BDNF knockout (bdnf(+/-)) mice. However ketamine and LY 451646 produced similar antidepressant-like responses in wildtype and bdnf(+/-) mice. Neither ketamine nor LY 451646 significantly influenced the levels BDNF or TrkB phosphorylation in the hippocampus when assessed at 45 min or 7 days after the drug administration. These data demonstrate that under the conditions tested, neither ketamine nor the AMPA-potentiator LY 451656 activate BDNF signaling, but produce a characteristic antidepressant-like response in heterozygous bdnf(+/-) mice. These data indicate that unlike biogenic amine-based agents, BDNF signaling does not play a pivotal role in the antidepressant effects of glutamate-based compounds. This article is part of a Special Issue entitled 'Anxiety and Depression'.

  3. Positive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor modulators have different impact on synaptic transmission in the thalamus and hippocampus.

    PubMed

    Xia, Yan-Fang; Kessler, Markus; Arai, Amy C

    2005-04-01

    Earlier studies showed that positive modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors enhance synaptic responses and facilitate synaptic plasticity. Those studies focused mainly on hippocampal functions. However, AMPA receptors have regionally distinct subunit compositions and thus potencies and efficacies of modulators may vary across the brain. The present study compared the effects of CX546 [1-(1,4-benzodioxan-6-ylcarbonyl) piperidine], a benzamide-type modulator, on synaptic transmission in neurons of the reticular thalamic nucleus (RTN), which regulates the firing mode of relay cells in other thalamic nuclei, and on hippocampal CA1 pyramidal cells. CX546 greatly prolonged synaptic responses in CA1 pyramidal cells, but at the same concentration it had only weak modulatory effects in RTN neurons. Effects on miniature excitatory postsynaptic currents (EPSCs) were similar to those on EPSCs in both regions, suggesting that variations in neuronal morphology and transmitter release kinetics do not account for the differences. Relay cells in the ventrobasal thalamus also exhibited weak modulatory effects that were comparable with those in RTN neurons. Regionally different effects on response duration were also observed with CX516 [BDP-12, 1-(quinoxalin-6-ylcarbonyl)piperidine], a second benzamide drug. In contrast, 100 microM cyclothiazide produced comparable synaptic enhancements in hippocampus and RTN. The regional selectivity of benzamide drugs (ampakines) may be explained, at least in part, by a lower potency at thalamic AMPA receptors, perhaps due to the prevalence of the subunits GluR3 and 4. Although regional preferences of the ampakines were modest in their extent, they may be sufficient to be of relevance when considering future therapeutic applications of such compounds.

  4. Ampakines cause sustained increases in brain-derived neurotrophic factor signaling at excitatory synapses without changes in AMPA receptor subunit expression.

    PubMed

    Lauterborn, J C; Pineda, E; Chen, L Y; Ramirez, E A; Lynch, G; Gall, C M

    2009-03-03

    Recent demonstrations that positive modulators of AMPA-type glutamate receptors (ampakines) increase neuronal brain-derived neurotrophic factor (BDNF) expression have suggested a novel strategy for treating neurodegenerative diseases. However, reports that AMPA and BDNF receptors are down-regulated by prolonged activation raise concerns about the extent to which activity-induced increases in BDNF levels can be sustained without compromising glutamate receptor function. The present study constitutes an initial test of whether ampakines can cause enduring increases in BDNF content and signaling without affecting AMPA receptor (AMPAR) expression. Prolonged (12-24 h) treatment with the ampakine CX614 reduced AMPAR subunit (glutamate receptor subunit (GluR) 1-3) mRNA and protein levels in cultured rat hippocampal slices whereas treatment with AMPAR antagonists had the opposite effects. The cholinergic agonist carbachol also depressed GluR1-3 mRNA levels, suggesting that AMPAR down-regulation is a global response to extended periods of elevated neuronal activity. Analyses of time courses and thresholds indicated that BDNF expression is influenced by lower doses of, and shorter treatments with, the ampakine than is AMPAR expression. Accordingly, daily 3 h infusions of CX614 chronically elevated BDNF content with no effect on GluR1-3 concentrations. Restorative deconvolution microscopy provided the first evidence that chronic up-regulation of BDNF is accompanied by increased activation of the neurotrophin's TrkB-Fc receptor at spine synapses. These results show that changes in BDNF and AMPAR expression are dissociable and that up-regulation of the former leads to enhanced trophic signaling at excitatory synapses. These findings are encouraging with regard to the feasibility of using ampakines to tonically enhance BDNF-dependent functions in adult brain.

  5. PARP-1 activation causes neuronal death in the hippocampal CA1 region by increasing the expression of Ca(2+)-permeable AMPA receptors.

    PubMed

    Gerace, E; Masi, A; Resta, F; Felici, R; Landucci, E; Mello, T; Pellegrini-Giampietro, D E; Mannaioni, G; Moroni, F

    2014-10-01

    An excessive activation of poly(ADP-ribose) polymerases (PARPs) may trigger a form of neuronal death similar to that occurring in neurodegenerative disorders. To investigate this process, we exposed organotypic hippocampal slices to N-methyl-N'-nitro-N'-nitrosoguanidine (MNNG, 100μM for 5min), an alkylating agent widely used to activate PARP-1. MNNG induced a pattern of degeneration of the CA1 pyramidal cells morphologically similar to that observed after a brief period of oxygen and glucose deprivation (OGD). MNNG exposure was also associated with a dramatic increase in PARP-activity and a robust decrease in NAD(+) and ATP content. These effects were prevented by PARP-1 but not PARP-2 inhibitors. In our experimental conditions, cell death was not mediated by AIF translocation (parthanatos) or caspase-dependent apoptotic processes. Furthermore, we found that PARP activation was followed by a significant deterioration of neuronal membrane properties. Using electrophysiological recordings we firstly investigated the suggested ability of ADP-ribose to open TRPM2 channels in MNNG-induced cells death, but the results we obtained showed that TRPM2 channels are not involved. We then studied the involvement of glutamate receptor-ion channel complex and we found that NBQX, a selective AMPA receptor antagonist, was able to effectively prevent CA1 neuronal loss while MK801, a NMDA antagonist, was not active. Moreover, we observed that MNNG treatment increased the ratio of GluA1/GluA2 AMPAR subunit expression, which was associated with an inward rectification of the IV relationship of AMPA sEPSCs in the CA1 but not in the CA3 subfield. Accordingly, 1-naphthyl acetyl spermine (NASPM), a selective blocker of Ca(2+)-permeable GluA2-lacking AMPA receptors, reduced MNNG-induced CA1 pyramidal cell death. In conclusion, our results show that activation of the nuclear enzyme PARP-1 may change the expression of membrane proteins and Ca(2+) permeability of AMPA channels, thus affecting

  6. Piracetam Defines a New Binding Site for Allosteric Modulators of α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors§

    PubMed Central

    Ahmed, Ahmed H.; Oswald, Robert E.

    2010-01-01

    Glutamate receptors are the most prevalent excitatory neurotransmitter receptors in the vertebrate central nervous system and are important potential drug targets for cognitive enhancement and the treatment of schizophrenia. Allosteric modulators of AMPA receptors promote dimerization by binding to a dimer interface and reducing desensitization and deactivation. The pyrrolidine allosteric modulators, piracetam and aniracetam, were among the first of this class of drugs to be discovered. We have determined the structure of the ligand binding domain of the AMPA receptor subtypes GluA2 and GluA3 with piracetam and a corresponding structure of GluA3 with aniracetam. Both drugs bind to both GluA2 and GluA3 in a very similar manner, suggesting little subunit specificity. However, the binding sites for piracetam and aniracetam differ considerably. Aniracetam binds to a symmetrical site at the center of the dimer interface. Piracetam binds to multiple sites along the dimer interface with low occupation, one of which is a unique binding site for potential allosteric modulators. This new site may be of importance in the design of new allosteric regulators. PMID:20163115

  7. Piracetam defines a new binding site for allosteric modulators of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors.

    PubMed

    Ahmed, Ahmed H; Oswald, Robert E

    2010-03-11

    Glutamate receptors are the most prevalent excitatory neurotransmitter receptors in the vertebrate central nervous system and are important potential drug targets for cognitive enhancement and the treatment of schizophrenia. Allosteric modulators of AMPA receptors promote dimerization by binding to a dimer interface and reducing desensitization and deactivation. The pyrrolidine allosteric modulators, piracetam and aniracetam, were among the first of this class of drugs to be discovered. We have determined the structure of the ligand binding domain of the AMPA receptor subtypes GluA2 and GluA3 with piracetam and a corresponding structure of GluA3 with aniracetam. Both drugs bind to GluA2 and GluA3 in a very similar manner, suggesting little subunit specificity. However, the binding sites for piracetam and aniracetam differ considerably. Aniracetam binds to a symmetrical site at the center of the dimer interface. Piracetam binds to multiple sites along the dimer interface with low occupation, one of which is a unique binding site for potential allosteric modulators. This new site may be of importance in the design of new allosteric regulators.

  8. Structural and Single-Channel Results Indicate that the Rates of Ligand Binding Domain Closing and Opening Directly Impact AMPA Receptor Gating

    SciTech Connect

    Zhang,W.; Cho, Y.; Lolis, E.; Howe, J.

    2008-01-01

    At most excitatory central synapses, glutamate is released from presynaptic terminals and binds to postsynaptic AMPA receptors, initiating a series of conformational changes that result in ion channel opening. Efficient transmission at these synapses requires that glutamate binding to AMPA receptors results in rapid and near-synchronous opening of postsynaptic receptor channels. In addition, if the information encoded in the frequency of action potential discharge is to be transmitted faithfully, glutamate must dissociate from the receptor quickly, enabling the synapse to discriminate presynaptic action potentials that are spaced closely in time. The current view is that the efficacy of agonists is directly related to the extent to which ligand binding results in closure of the binding domain. For glutamate to dissociate from the receptor, however, the binding domain must open. Previously, we showed that mutations in glutamate receptor subunit 2 that should destabilize the closed conformation not only sped deactivation but also altered the relative efficacy of glutamate and quisqualate. Here we present x-ray crystallographic and single-channel data that support the conclusions that binding domain closing necessarily precedes channel opening and that the kinetics of conformational changes at the level of the binding domain importantly influence ion channel gating. Our findings suggest that the stability of the closed-cleft conformation has been tuned during evolution so that glutamate dissociates from the receptor as rapidly as possible but remains an efficacious agonist.

  9. Effects of the blood components on the AMPA and NMDA synaptic responses in brain slices in the onset of hemorrhagic stroke.

    PubMed

    Mokrushin, Anatoly A; Pavlinova, Larisa I

    2013-12-01

    Blood-borne events play a major role in post bleeding disturbances of the neuronal network. However, very little is known about the early effects of blood plasma, leucocytes, and the red blood cells on the AMPA and NMDA-mediated synaptic responses in the onset of experimental intracranial hemorrhage (ICH). In this study, we used the technique of on-line monitoring of electrophysiological parameters referred to synaptic activity in piriform cortex of SHR rat slice. We exposed the olfactory cortex slices to diluted autologous blood or its components and compared with effects of ferric chloride. Whole blood exerted a total inhibition of synaptic activity in piriform cortex within first 5 min. Dilution of blood induced prolonged epileptic synaptic activation of NMDA receptors. Blood plasma and fraction of leucocytes induced hyperactivation of neurons transforming to epileptiform discharges. Fraction of red blood cells acted biphasic, an initial sharp activity of AMPA- and NMDA-mediated receptors replaced by a following total depression. Our slice-based models of experimental stroke revealed the mechanism of the earliest pathophysiologic events occur in brain tissue during bleeding that may be relevant to the human ICH.

  10. Roles of the AMPA receptor subunit GluA1 but not GluA2 in synaptic potentiation and activation of ERK in the anterior cingulate cortex.

    PubMed

    Toyoda, Hiroki; Zhao, Ming-Gao; Ulzhöfer, Bettina; Wu, Long-Jun; Xu, Hui; Seeburg, Peter H; Sprengel, Rolf; Kuner, Rohini; Zhuo, Min

    2009-08-10

    Cortical areas including the anterior cingulate cortex (ACC) are important for pain and pleasure. Recent studies using genetic and physiological approaches have demonstrated that the investigation of basic mechanism for long-term potentiation (LTP) in the ACC may reveal key cellular and molecular mechanisms for chronic pain in the cortex. Glutamate N-methyl D-aspartate (NMDA) receptors in the ACC are critical for the induction of LTP, including both NR2A and NR2B subunits. However, cellular and molecular mechanisms for the expression of ACC LTP have been less investigated. Here, we report that the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit, GluA1 but not GluA2 contributes to LTP in the ACC using genetic manipulated mice lacking GluA1 or GluA2 gene. Furthermore, GluA1 knockout mice showed decreased extracellular signal-regulated kinase (ERK) phosphorylation in the ACC in inflammatory pain models in vivo. Our results demonstrate that AMPA receptor subunit GluA1 is a key mechanism for the expression of ACC LTP and inflammation-induced long-term plastic changes in the ACC.

  11. Dynamics and environmental risk assessment of the herbicide glyphosate and its metabolite AMPA in a small vineyard river of the Lake Geneva catchment.

    PubMed

    Daouk, Silwan; Copin, Pierre-Jean; Rossi, Luca; Chèvre, Nathalie; Pfeifer, Hans-Rudolf

    2013-09-01

    The use of pesticides may lead to environmental problems, such as surface water pollution, with a risk for aquatic organisms. In the present study, a typical vineyard river of western Switzerland was first monitored to measure discharged loads, identify sources, and assess the dynamic of the herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA). Second, based on river concentrations, an associated environmental risk was calculated using laboratory tests and ecotoxicity data from the literature. Measured concentrations confirmed the mobility of these molecules with elevated peaks during flood events, up to 4970 ng/L. From April 2011 to September 2011, a total load of 7.1 kg was calculated, with 85% coming from vineyards and minor urban sources and 15% from arable crops. Compared with the existing literature, this load represents an important fraction (6-12%) of the estimated amount applied because of the steep vineyard slopes (∼10%). The associated risk of these compounds toward aquatic species was found to be negligible in the present study, as well as for other rivers in Switzerland. A growth stimulation was nevertheless observed for the algae Scenedesmus vacuolatus with low concentrations of glyphosate, which could indicate a risk of perturbation in aquatic ecosystems, such as eutrophication. The combination of field and ecotoxicity data allowed the performance of a realistic risk assessment for glyphosate and AMPA, which should be applied to other pesticide molecules.

  12. Studies on an (S)-2-Amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic Acid (AMPA) Receptor Antagonist IKM-159: Asymmetric Synthesis, Neuroactivity, and Structural Characterization

    PubMed Central

    Juknaitė, Lina; Sugamata, Yutaro; Tokiwa, Kazuya; Ishikawa, Yuichi; Takamizawa, Satoshi; Eng, Andrew; Sakai, Ryuichi; Pickering, Darryl S.; Frydenvang, Karla; Swanson, Geoffrey T.; Kastrup, Jette S.; Oikawa, Masato

    2015-01-01

    IKM-159 was developed and identified as a member of a new class of heterotricyclic glutamate analogues that act as AMPA receptor-selective antagonists. However, it was not known which enantiomer of IKM-159 was responsible for its pharmacological activities. Here, we report in vivo and in vitro neuronal activities of both enantiomers of IKM-159 prepared by enantioselective asymmetric synthesis. By employment of (R)-2-amino-2-(4-methoxyphenyl)ethanol as a chiral auxiliary, (2R)-IKM-159 and the (2S)-counterpart were successfully synthesized in 0.70% and 1.5% yields, respectively, over a total of 18 steps. Both behavioral and electrophysiological assays showed that the biological activity observed for the racemic mixture was reproduced only with (2R)-IKM-159, whereas the (2S)-counterpart was inactive in both assays. Racemic IKM-159 was crystallized with the ligand-binding domain of GluA2, and the structure revealed a complex containing (2R)-IKM-159 at the glutamate binding site. (2R)-IKM-159 locks the GluA2 in an open form, consistent with a pharmacological action as competitive antagonist of AMPA receptors. PMID:23432124

  13. NMDA but not AMPA glutamatergic receptors are involved in the antidepressant-like activity of MTEP during the forced swim test in mice.

    PubMed

    Pomierny-Chamioło, Lucyna; Poleszak, Ewa; Pilc, Andrzej; Nowak, Gabriel

    2010-01-01

    Several lines of evidence suggest an antidepressant-like activity for 3-[(methyl-1,3-thiazol-4-yl)ethynyl]-pyridine (MTEP), a highly selective, non-competitive antagonist of metabotropic glutamate receptors subtype 5 (mGluR(5)). This effect has been observed following both acute and chronic MTEP treatments in behavioral tests and experimental models of depression, such as the forced swim test (FST), the tail suspension test, and the olfactory bulbectomy model of depression. However, the mechanism of action for mGluR(5) antagonists remains unclear. The aim of this study was to investigate whether the antidepressant-like action of MTEPis dependent on ionotropic glutamatergic receptors. Male Albino Swiss mice were used, and antidepressant-like activity was evaluated using the FST. The antidepressant-like effect of MTEP (0.3 mg/kg) was significantly antagonized by pre-treatment with the NMDA receptor agonist N-methyl-D-aspartic acid (NMDA, 75 mg/kg, i.p.). The AMPA receptor antagonist NBQX (10 mg/kg, i.p.) did not affect the MTEP activity. Our results indicate that the antidepressant-like activity of MTEP in the FST involves NMDA but not AMPA receptors and suggest that the interaction between mGluR(5) and NMDA receptors plays an important role in the underlying antidepressant mechanism(s).

  14. NMDA and AMPA receptors are involved in the antidepressant-like activity of tianeptine in the forced swim test in mice.

    PubMed

    Wlaź, Piotr; Kasperek, Regina; Wlaź, Aleksandra; Szumiło, Michał; Wróbel, Andrzej; Nowak, Gabriel; Poleszak, Ewa

    2011-01-01

    It is known that tianeptine exhibits antidepressant-like activity. Its influence on the glutamatergic system is also known, but the mechanisms involved in this activity remain to be established. The aim of this study was to investigate the involvement of the glutamate pathway in the antidepressant-like action of tianeptine. We investigated the effects of N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor ligands on tianeptine-induced activity in the forced swim test (FST) in mice. The antidepressant-like activity of tianeptine (30 m/kg, ip) was significantly antagonized by D-serine (100 nmol/mouse icv) and NBQX (10 mg/kg, ip). Moreover, low, ineffective doses of the glycine/NMDA site antagonist L-701,324 (1 mg/kg, ip) administered together with low, ineffective doses of tianeptine (20 mg/kg, ip) exhibited a significant reduction of immobility time in the FST. These doses of the examined agents, which did have an effect in the FST, did not alter locomotor activity. The present study indicates that the antidepressant-like activity of tianeptine in the FST involves both NMDA and AMPA receptors and suggests that the interaction between serotonergic and glutamatergic transmission may play an important role in the action of tianeptine.

  15. Morphological features and responses to AMPA receptor-mediated excitotoxicity of mouse motor neurons: comparison in purified, mixed anterior horn or motor neuron/glia cocultures.

    PubMed

    De Paola, Massimiliano; Diana, Valentina; Bigini, Paolo; Mennini, Tiziana

    2008-05-15

    Primary motor neuron cultures are widely used as in vitro model to study the early mechanisms involved in the aetiology of amyotrophic lateral sclerosis. In this study, we directly compared the morphological features and the responses to AMPA receptor (AMPAR) activation of mouse spinal cord motor neurons under different culture conditions (OptiPrep-purified, mixed anterior horn or motor neuron/glia cocultures). Motor neurons cocultured with a confluent glial layer had significant improvements in axonal length and in somata perimeter and area, compared both to mixed anterior horn cultures and to purified cultures, suggesting that the presence of more "mature" glial cells was determinant to obtain healthier motor neurons. By immuno-cytochemical assays we found that both in mixed anterior horn cultures and in cocultures, lower AMPA (0.3 microM) or kainate (5 microM) concentrations, but not the higher (1 or 15 microM, respectively), induced classical apoptotic events such as the nuclear fragmentation, the membrane externalization of phosphatidylserine residues and the activation of caspases-9 and -3. The morphological features and the different degenerative pathways induced by AMPAR agonist concentrations suggest that the experimental conditions used for in vitro studies are key factors that should be deeply considered to obtain more valid and reproducible results.

  16. Increase of AMPA receptor glutamate receptor 1 subunit and B-cell receptor-associated protein 31 gene expression in hippocampus of fatigued mice.

    PubMed

    Kamakura, Masaki; Tamaki, Keisuke; Sakaki, Toshiyuki; Yoneda, Yukio

    2005-10-14

    Central fatigue is an indispensable biosignal for maintaining life, but the neuronal and molecular mechanisms involved remain unclear. In this study, we searched for genes differentially expressed in the hippocampus of fatigued mice to elucidate the mechanisms underlying fatigue. Mice were forced to swim in an adjustable-current water pool, and the maximum swimming time (endurance) until fatigue was measured thrice. Fatigued and nonfatigued mice with equal swimming capacity and body weight were compared. We found that the genes of GluR1 and B-cell receptor-associated protein 31 (Bap31), which acts as a transport molecule in the secretory pathway or as a mediator of apoptosis, were upregulated in the hippocampus of fatigued mice, and increases of GluR1 and Bap31 were confirmed by Northern blotting and real-time PCR. No change of gene expression of AMPA receptor subunits other than GluR1 was observed. These results suggest that a compositional change of AMPA receptor (increase of GluR1) and upregulation of the Bap31 gene may be implicated in fatigue in mice.

  17. Efficacy of the GluK1/AMPA Receptor Antagonist LY293558 against Seizures and Neuropathology in a Soman-Exposure Model without Pretreatment and its Pharmacokinetics after Intramuscular Administration

    PubMed Central

    Apland, James P.; Aroniadou-Anderjaska, Vassiliki; Figueiredo, Taiza H.; Green, Carol E.; Swezey, Robert; Yang, Chun; Qashu, Felicia

    2013-01-01

    Control of brain seizures after exposure to nerve agents is imperative for the prevention of brain damage and death. Animal models of nerve agent exposure make use of pretreatments, or medication administered within 1 minute after exposure, in order to prevent rapid death from peripheral toxic effects and respiratory failure, which then allows the testing of anticonvulsant compounds. However, in a real-case scenario of an unexpected attack with nerve agents, pretreatment would not be possible, and medical assistance may not be available immediately. To determine if control of seizures and survival are still possible without pretreatment or immediate pharmacologic intervention, we studied the anticonvulsant efficacy of the GluK1 (GluR5)/α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist (3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl]decahydroisoquinoline-3-carboxylic acid (LY293558) in rats that did not receive any treatment until 20 minutes after exposure to the nerve agent soman. We injected LY293558 intramuscularly, as this would be the most likely route of administration to humans. LY293558 (15 mg/kg), injected along with atropine and the oxime HI-6 at 20 minutes after soman exposure, stopped seizures and increased survival rate from 64% to 100%. LY293558 also prevented neuronal loss in the amygdala and hippocampus, and reduced neurodegeneration in a number of brain regions studied 7 days after soman exposure. Analysis of the LY293558 pharmacokinetics after intramuscular administration showed that this compound readily crosses the blood–brain barrier. There was good correspondence between the time course of seizure suppression by LY293558 and the brain levels of the compound. PMID:23042954

  18. Adaptations in AMPA receptor transmission in the nucleus accumbens contributing to incubation of cocaine craving

    PubMed Central

    Loweth, Jessica A.; Tseng, Kuei Y.; Wolf, Marina E.

    2013-01-01

    Cue-induced cocaine craving in rodents intensifies or “incubates” during the first months of withdrawal from long access cocaine self-administration. This incubation phenomenon is relevant to human users who achieve abstinence but exhibit persistent vulnerability to cue-induced relapse. It is well established that incubation of cocaine craving involves complex neuronal circuits. Here we will focus on neuroadaptations in the nucleus accumbens (NAc), a region of convergence for pathways that control cocaine seeking. A key adaptation is a delayed (~3–4 weeks) accumulation of Ca2+-permeable AMPAR receptors (CP-AMPARs) in synapses on medium spiny neurons (MSN) of the NAc. These CP-AMPARs mediate the expression of incubation after prolonged withdrawal, although different mechanisms must be responsible during the first weeks of withdrawal, prior to CP-AMPAR accumulation. The cascade of events leading to CP-AMPAR accumulation is still unclear. However, several candidate mechanisms have been identified. First, mGluR1 has been shown to negatively regulate CP-AMPAR levels in NAc synapses, and it is possible that a withdrawal-dependent decrease in this effect may help explain CP-AMPAR accumulation during incubation. Second, an increase in phosphorylation of GluA1 subunits (at the protein kinase A site) within extrasynaptic homomeric GluA1 receptors (CP-AMPARs) may promote their synaptic insertion and oppose their removal. Finally, elevation of brain-derived neurotrophic factor (BDNF) levels in the NAc may contribute to maintenance of incubation after months of withdrawal, although incubation-related increases in BDNF accumulation do not account for CP-AMPAR accumulation. Receptors and pathways that negatively regulate incubation, such as mGluR1, are promising targets for the development of therapeutic strategies to help recovering addicts maintain abstinence. PMID:23727437

  19. Enhanced Long-Term and Impaired Short-Term Spatial Memory in GluA1 AMPA Receptor Subunit Knockout Mice: Evidence for a Dual-Process Memory Model

    ERIC Educational Resources Information Center

    Sanderson, David J.; Good, Mark A.; Skelton, Kathryn; Sprengel, Rolf; Seeburg, Peter H.; Rawlins, J. Nicholas P.; Bannerman, David M.

    2009-01-01

    The GluA1 AMPA receptor subunit is a key mediator of hippocampal synaptic plasticity and is especially important for a rapidly-induced, short-lasting form of potentiation. GluA1 gene deletion impairs hippocampus-dependent, spatial working memory, but spares hippocampus-dependent spatial reference memory. These findings may reflect the necessity of…

  20. What a Nostril Knows: Olfactory Nerve-Evoked AMPA Responses Increase while NMDA Responses Decrease at 24-h Post-Training for Lateralized Odor Preference Memory in Neonate Rat

    ERIC Educational Resources Information Center

    Yuan, Qi; Harley, Carolyn W.

    2012-01-01

    Increased AMPA signaling is proposed to mediate long-term memory. Rat neonates acquire odor preferences in a single olfactory bulb if one nostril is occluded at training. Memory testing here confirmed that only trained bulbs support increased odor preference at 24 h. Olfactory nerve field potentials were tested at 24 h in slices from trained and…

  1. Non-fibrillar beta-amyloid abates spike-timing-dependent synaptic potentiation at excitatory synapses in layer 2/3 of the neocortex by targeting postsynaptic AMPA receptors.

    PubMed

    Shemer, Isaac; Holmgren, Carl; Min, Rogier; Fülöp, Livia; Zilberter, Misha; Sousa, Kyle M; Farkas, Tamás; Härtig, Wolfgang; Penke, Botond; Burnashev, Nail; Tanila, Heikki; Zilberter, Yuri; Harkany, Tibor

    2006-04-01

    Cognitive decline in Alzheimer's disease (AD) stems from the progressive dysfunction of synaptic connections within cortical neuronal microcircuits. Recently, soluble amyloid beta protein oligomers (Abeta(ol)s) have been identified as critical triggers for early synaptic disorganization. However, it remains unknown whether a deficit of Hebbian-related synaptic plasticity occurs during the early phase of AD. Therefore, we studied whether age-dependent Abeta accumulation affects the induction of spike-timing-dependent synaptic potentiation at excitatory synapses on neocortical layer 2/3 (L2/3) pyramidal cells in the APPswe/PS1dE9 transgenic mouse model of AD. Synaptic potentiation at excitatory synapses onto L2/3 pyramidal cells was significantly reduced at the onset of Abeta pathology and was virtually absent in mice with advanced Abeta burden. A decreased alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)/N-methyl-D-aspartate (NMDA) receptor-mediated current ratio implicated postsynaptic mechanisms underlying Abeta synaptotoxicity. The integral role of Abeta(ol)s in these processes was verified by showing that pretreatment of cortical slices with Abeta((25-35)ol)s disrupted spike-timing-dependent synaptic potentiation at unitary connections between L2/3 pyramidal cells, and reduced the amplitude of miniature excitatory postsynaptic currents therein. A robust decrement of AMPA, but not NMDA, receptor-mediated currents in nucleated patches from L2/3 pyramidal cells confirmed that Abeta(ol)s perturb basal glutamatergic synaptic transmission by affecting postsynaptic AMPA receptors. Inhibition of AMPA receptor desensitization by cyclothiazide significantly increased the amplitude of excitatory postsynaptic potentials evoked by afferent stimulation, and rescued synaptic plasticity even in mice with pronounced Abeta pathology. We propose that soluble Abeta(ol)s trigger the diminution of synaptic plasticity in neocortical pyramidal cell networks during early

  2. The Inhibitory Effect of α/β-Hydrolase Domain-Containing 6 (ABHD6) on the Surface Targeting of GluA2- and GluA3-Containing AMPA Receptors

    PubMed Central

    Wei, Mengping; Jia, Moye; Zhang, Jian; Yu, Lulu; Zhao, Yunzhi; Chen, Yingqi; Ma, Yimeng; Zhang, Wei; Shi, Yun S.; Zhang, Chen

    2017-01-01

    The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) are major excitatory receptors that mediate fast neurotransmission in the mammalian brain. The surface expression of functional AMPARs is crucial for synaptic transmission and plasticity. AMPAR auxiliary subunits control the biosynthesis, membrane trafficking, and synaptic targeting of AMPARs. Our previous report showed that α/β-hydrolase domain-containing 6 (ABHD6), an auxiliary subunit for AMPARs, suppresses the membrane delivery and function of GluA1-containing receptors in both heterologous cells and neurons. However, it remained unclear whether ABHD6 affects the membrane trafficking of glutamate receptor subunits, GluA2 and GluA3. Here, we examine the effects of ABHD6 overexpression in HEK293T cells expressing GluA1, GluA2, GluA3, and stargazin, either alone or in combination. The results show that ABHD6 suppresses the glutamate-induced currents and the membrane expression of AMPARs when expressing GluA2 or GluA3 in the HEK293T cells. We generated a series of GluA2 and GluA3 C-terminal deletion constructs and confirm that the C-terminus of GluAs is required for ABHD6’s inhibitory effects on glutamate-induced currents and surface expression of GluAs. Meanwhile, our pull-down experiments reveal that ABHD6 binds to GluA1–3, and deletion of the C-terminal domain of GluAs abolishes this binding. These findings demonstrate that ABHD6 inhibits the AMPAR-mediated currents and its surface expression, independent of the type of AMPAR subunits, and this inhibitor’s effects are mediated through the binding with the GluAs C-terminal regions. PMID:28303090

  3. Group I mGluR activation reverses cocaine-induced accumulation of calcium-permeable AMPA receptors in nucleus accumbens synapses via a protein kinase C-dependent mechanism.

    PubMed

    McCutcheon, James E; Loweth, Jessica A; Ford, Kerstin A; Marinelli, Michela; Wolf, Marina E; Tseng, Kuei Y

    2011-10-12

    Following prolonged withdrawal from extended access cocaine self-administration in adult rats, high conductance Ca2+ -ermeable AMPA receptors (CP-AMPARs) accumulate in nucleus accumbens (NAc) synapses and mediate the expression of "incubated" cue-induced cocaine craving. Using patch-clamp recordings from NAc slices prepared after extended access cocaine self-administration and >45 d of withdrawal, we found that group I metabotropic glutamate receptor (mGluR) stimulation using 3,5-dihydroxyphenylglycine (DHPG; 50 μm) rapidly eliminates the postsynaptic CP-AMPAR contribution to NAc synaptic transmission. This is accompanied by facilitation of Ca2+ -impermeable AMPAR (CI-AMPAR)-mediated transmission, suggesting that DHPG may promote an exchange between CP-AMPARs and CI-AMPARs. In saline controls, DHPG also reduced excitatory transmission but this occurred through a CB1 receptor-dependent presynaptic mechanism rather than an effect on postsynaptic AMPARs. Blockade of CB1 receptors had no significant effect on the alterations in AMPAR transmission produced by DHPG in the cocaine group. Interestingly, the effect of DHPG in the cocaine group was mediated by mGluR1 whereas its effect in the saline group was mediated by mGluR5. These results indicate that regulation of synaptic transmission in the NAc is profoundly altered after extended access cocaine self-administration and prolonged withdrawal. Furthermore, they suggest that activation of mGluR1 may represent a potential strategy for reducing cue-induced cocaine craving in abstinent cocaine addicts.

  4. Ca2+ imaging of mouse neocortical interneurone dendrites: Contribution of Ca2+-permeable AMPA and NMDA receptors to subthreshold Ca2+dynamics

    PubMed Central

    Goldberg, Jesse H; Yuste, Rafael; Tamas, Gabor

    2003-01-01

    In this second study, we have combined two-photon calcium imaging with whole-cell recording and anatomic reconstructions to directly characterize synaptically evoked calcium signals in three types of mouse V1 supragranular interneurones: parvalbumin-positive fast spikers (FS), calretinin-positive irregular spikers (IS), and adapting cells (AD). We observed that subthreshold synaptic activation evoked calcium signals locally restricted to individual dendritic compartments. These signals were mediated by NMDA receptors (NMDARs) in AD and IS cells, whereas in FS cells, calcium-permeable AMPA receptors (CP-AMPARs) provided an additional and kinetically distinct influx. Furthermore, even a single, subthreshold synaptic activation evoked a larger dendritic calcium influx than backpropagating action potentials. Our results demonstrate that NMDARs dominate subthreshold calcium dynamics in interneurones and reveal the functional contribution of CP-AMPARs to a specific subclass of cortical interneurone. These data highlight different strategies in dendritic signal processing by distinct classes of interneurones. PMID:12844507

  5. Q/R RNA editing of the AMPA receptor subunit 2 (GRIA2) transcript evolves no later than the appearance of cartilaginous fishes.

    PubMed

    Kung, S S; Chen, Y C; Lin, W H; Chen, C C; Chow, W Y

    2001-12-07

    The amino acid, either a glutamine (Q) or an arginine (R), at the Q/R site of the pore-lining segment (M2) of a vertebrate AMPA receptor subunit critically influences the properties of the receptor. The R codon of the mammalian AMPA receptor subunit 2 (GRIA2) transcript is not coded by the chromosomal sequence, but is created by posttranscriptional RNA editing activities. On the other hand, the R codons of some teleost GRIA2 homologs are coded by chromosomal sequences. To elucidate the evolution of the utilization of Q/R RNA editing in modifying vertebrate GRIA2 transcripts, the GRIA2 genes of five fish species and an amphibian were studied. The putative hagfish GRIA2 homolog (hfGRIA2) encodes an R codon, whereas shark and bullfrog GRIA2 genes specify a Q codon at the genomic Q/R site. All gnathostoma GRIA2 genes possess an intron splitting the coding regions of M2 and the third hydrophobic region (M3). The intronic components required for Q/R RNA editing are preserved in all the Q-coding vertebrate GRIA2 genes but are absent from the R-coding GRIA2 genes. Interestingly, the hfGRIA2 is intronless, suggesting that hfGRIA2 is unlikely evolved from a Q/R editing-competent gene. Results of this study suggest that modification of GRIA2 transcripts by Q/R editing is most likely acquired after the separation of the Agnatha and Gnathostome.

  6. PICK1 and phosphorylation of the glutamate receptor 2 (GluR2) AMPA receptor subunit regulates GluR2 recycling after NMDA receptor-induced internalization.

    PubMed

    Lin, Da-Ting; Huganir, Richard L

    2007-12-12

    Changes in surface trafficking of AMPA receptors play an important role in synaptic plasticity. Phosphorylation of the C terminus of the AMPA receptor (AMPAR) subunit glutamate receptor 2 (GluR2) and the binding of GluR2 to the PDZ [postsynaptic density-95/Discs large/zona occludens-1]-domain containing protein, protein interacting with protein kinase C (PICK1), have been proposed to play an important role in NMDA receptor dependent internalization of GluR2. However, the fate of internalized GluR2 after NMDA receptor (NMDAR) activation is still unclear. Both recycling and degradation of GluR2 after the activation of NMDAR have been reported. Here, we used a pH-sensitive green fluorescent protein variant, pHluorin, tagged to the N terminus of GluR2 (pH-GluR2) to study the dynamic internalization and recycling of GluR2 after NMDAR activation. Using fluorescence recovery after photobleach (FRAP), we directly demonstrate that internalized pH-GluR2 subunits recycle back to the cell surface after NMDAR activation. We further demonstrate that changing the phosphorylation state of the S880 residue at the C terminus of GluR2 does not affect NMDAR-dependent GluR2 internalization, but alters the recycling of GluR2 after NMDAR activation. In addition, mutation of the N-ethylmaleimide-sensitive fusion protein (NSF) binding site in the pH-GluR2 slows receptor recycling. Finally, neurons lacking PICK1 display normal NMDAR dependent GluR2 internalization compared with wild-type neurons, but demonstrate accelerated GluR2 recycling after NMDAR activation. These results indicate that phosphorylation of GluR2 S880 and NSF and PICK1 binding to GluR2 dynamically regulate GluR2 recycling.

  7. Role of bed nucleus of the stria terminalis and amygdala AMPA receptors in the development and expression of context conditioning and sensitization of startle by prior shock

    PubMed Central

    Davis, Michael

    2013-01-01

    A core symptom of post-traumatic stress disorder is hyper-arousal—manifest in part by increases in the amplitude of the acoustic startle reflex. Gewirtz et al. (Prog Neuropsychopharmacol Biol Psychiatry 22:625–648, 1998) found that, in rats, persistent shock-induced startle increases were prevented by pre-test electrolytic lesions of the bed nucleus of the stria terminalis (BNST). We used reversible inactivation to determine if similar effects reflect actions on (a) BNST neurons themselves versus fibers-of-passage, (b) the development versus expression of such increases, and (c) associative fear versus non-associative sensitization. Twenty-four hours after the last of three shock sessions, startle was markedly enhanced when rats were tested in a non-shock context. These increases decayed over the course of several days. Decay was unaffected by context exposure, and elevated startle was restored when rats were tested for the first time in the original shock context. Thus, both associative and non-associative components could be measured under different conditions. Pre-test intra-BNST infusions of the AMPA receptor antagonist NBQX (3 μg/side) blocked the non-associative (as did infusions into the basolateral amygdala) but not the associative component, whereas pre-shock infusions disrupted both. NBQX did not affect baseline startle or shock reactivity. These results indicate that AMPA receptors in or very near to the BNST are critical for the expression and development of non-associative shock-induced startle sensitization, and also for context fear conditioning, but not context fear expression. More generally, they suggest that treatments targeting the BNST may be clinically useful for treating trauma-related hyper-arousal and perhaps for retarding its development. PMID:23934654

  8. An increase in AMPA and a decrease in SK conductance increase burst firing by different mechanisms in a model of a dopamine neuron in vivo

    PubMed Central

    Canavier, C.C.; Landry, R.S.

    2007-01-01

    A stylized, symmetric, compartmental model of a dopamine neuron in vivo shows how rate and pattern can be modulated either concurrently or differentially. If two or more parameters in the model are varied concurrently, the baseline firing rate and the extent of bursting become de-correlated, which provides an explanation for the lack of a tight correlation in vivo, and is consistent with some independence of the mechanisms that generate baseline firing rates versus bursts. We hypothesize that most bursts are triggered by a barrage of synaptic input, and that particularly meaningful stimuli recruit larger numbers of synapses in a more synchronous way. An example of concurrent modulation is that increasing the short-lived AMPA current evokes additional spikes without regard to pattern, producing comparable increases in spike frequency and fraction fired in bursts. On the other hand, blocking the SK current evokes additional bursts by allowing a depolarization that previously produced only a single spike to elicit two or more, and elongates existing bursts by the same principle, resulting in a greater effect on pattern than rate. A probabilistic algorithm for the random insertion of spikes into the firing pattern produces a good approximation to the pattern changes induced by increasing the AMPA conductance, but not by blocking the SK current, consistent with a differential modulation in the latter case. Furthermore, blocking SK produced a longer burst with a greater intra-burst frequency in response to a simulated meaningful input, suggesting that reduction of this current may augment reward-related responses. PMID:16885519

  9. Association of the AMPA receptor-related postsynaptic density proteins GRIP and ABP with subsets of glutamate-sensitive neurons in the rat retina.

    PubMed

    Gábriel, Robert; de Souza, Sunita; Ziff, Edward B; Witkovsky, Paul

    2002-07-22

    We used specific antibodies against two postsynaptic density proteins, GRIP (glutamate receptor interacting protein) and ABP (AMPA receptor-binding protein), to study their distribution in the rat retina. In the central nervous system, it has been shown that both proteins bind strongly to the AMPA glutamate receptor (GluR) 2/3 subunits, but not other GluRs, through a set of three PDZ domains. Western blots detected a single GRIP protein that was virtually identical in retina and brain, whereas retinal ABP corresponded to only one of three ABP peptides found in brain. The retinal distributions of GluR2/3, GRIP, and ABP immunoreactivity (IR) were similar but not identical. GluR2/3 immunoreactivity (IR) was abundant in both plexiform layers and in large perikarya. ABP IR was concentrated in large perikarya but was sparse in the plexiform layers, whereas GRIP IR was relatively more abundant in the plexiform layers than in perikarya. Immunolabel for these three antibodies consisted of puncta < or = 0.2 microm in diameter. The cellular localization of GRIP and ABP IR was examined by double labeling subclasses of retinal neuron with characteristic marker proteins, e.g., calbindin. GRIP, ABP, and GluR2/3 IR were detected in horizontal cells, dopaminergic and glycinergic AII amacrine cells and large ganglion cells. Immunolabel was absent in rod bipolar and weak or absent in cholinergic amacrine cells. By using the tyramide method of signal amplification, a colocalization of GluR2/3 was found with either GRIP or ABP in horizontal cell terminals, and perikarya of amacrine and ganglion cells. Our results show that ABP and GRIP colocalize with GluR2/3 in particular subsets of retinal neuron, as was previously established for certain neurons in the brain.

  10. 7, 8-Dihydroxyflavone induces synapse expression of AMPA GluA1 and ameliorates cognitive and spine abnormalities in a mouse model of fragile X syndrome.

    PubMed

    Tian, Mi; Zeng, Yan; Hu, Yilan; Yuan, Xiuxue; Liu, Shumin; Li, Jie; Lu, Pan; Sun, Yao; Gao, Lei; Fu, Daan; Li, Yi; Wang, Shasha; McClintock, Shawn M

    2015-02-01

    Fragile X syndrome (FXS) is characterized by immature dendritic spine architectures and cognitive impairment. 7, 8-Dihydroxyflavone (7, 8-DHF) has recently been identified as a high affinity tropomyosin receptor kinase B (TrkB) agonist. The purpose of this paper was to examine the utility of 7, 8-DHF as an effective pharmacotherapeutic agent that targets dendritic pathology and cognitive impairments in FXS mutant. We synthesized pharmacologic, behavioral, and biochemical approaches to examine the effects of 7, 8-DHF on spatial and fear memory functions, and morphological spine abnormalities in fragile X mental retardation 1 (Fmr1) gene knock-out mice. The study found that 4 weeks of treatment with 7, 8-DHF improved spatial and fear memory, and ameliorated morphological spine abnormalities including the number and elongation of spines in the hippocampus and amygdala. Further mechanism analysis revealed that 7, 8-DHF enhanced the expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) GluA1 receptor, but reduced the normal levels of GluA2 at the synapses in Fmr1. Potentially related to drug-induced changes in AMPA receptor subunits, 7, 8-DHF at the synapses led to phosphorylation of specific serine sites on subunits Ser818 and Ser813 of GluA1, and Ser880 of GluA2, as well as phosphorylation of TrkB, calcium/calmodulin-dependent protein kinase II, and protein kinase C. However, 7, 8-DHF neither affected behavioral performance nor increased TrkB phosphorylation in WT mice, which suggested that it had FXS-specific correcting effect. Altogether, these results demonstrated that 7, 8-DHF improved learning and memory, and reduced abnormalities in spine morphology, thus providing a potential pharmacotherapeutic strategy for FXS.

  11. Insights into the mechanisms of ifosfamide encephalopathy: drug metabolites have agonistic effects on alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors and induce cellular acidification in mouse cortical neurons.

    PubMed

    Chatton, J Y; Idle, J R; Vågbø, C B; Magistretti, P J

    2001-12-01

    Therapeutic value of the alkylating agent ifosfamide has been limited by major side effects including encephalopathy. Although the underlying biochemical processes of the neurotoxic side effects are still unclear, they could be attributed to metabolites rather than to ifosfamide itself. In the present study, the effects of selected ifosfamide metabolites on indices of neuronal activity have been investigated, in particular for S-carboxymethylcysteine (SCMC) and thiodiglycolic acid (TDGA). Because of structural similarities of SCMC with glutamate, the Ca(2+)(i) response of single mouse cortical neurons to SCMC and TDGA was investigated. SCMC, but not TDGA, evoked a robust increase in Ca(2+)(i) concentration that could be abolished by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), but only partly diminished by the N-methyl-D-aspartate receptor antagonist 10,11-dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK=801). Cyclothiazide (CYZ), used to prevent AMPA/kainate receptor desensitization, potentiated the response to SCMC. Because activation of AMPA/kainate receptors is known to induce proton influx, the intracellular pH (pH(i)) response to SCMC was investigated. SCMC caused a concentration-dependent acidification that was amplified by CYZ. Since H(+)/monocarboxylate transporter (MCT) activity leads to similar cellular acidification, we tested its potential involvement in the pH(i) response. Application of the lactate transport inhibitor quercetin diminished the pH(i) response to SCMC and TDGA by 43 and 51%, respectively, indicating that these compounds may be substrates of MCTs. Taken together, this study indicates that hitherto apparently inert ifosfamide metabolites, in particular SCMC, activate AMPA/kainate receptors and induce cellular acidification. Both processes could provide the biochemical basis of the observed ifosfamide-associated encephalopathy.

  12. The herbicide glyphosate and its metabolite AMPA in the Lavaux vineyard area, Western Switzerland: proof of widespread export to surface waters. Part I: method validation in different water matrices.

    PubMed

    Daouk, Silwan; Grandjean, Dominique; Chevre, Nathalie; De Alencastro, Luiz F; Pfeifer, Hans-Rudolf

    2013-01-01

    An analytical method for the quantification of the widely used herbicide, glyphosate, its main by-product, aminomethylphosphonic acid (AMPA) and the herbicide glufosinate at trace level was developed and tested in different aqueous matrices. Their derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) was done prior to their concentration and purification by solid phase extraction. The concentrated derivates were then analyzed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Spiking tests at three different concentrations were realized in several water matrices: ultrapure water, Evian(©) mineral water, river water, soil solution and runoff water of a vineyard. Except for AMPA in runoff water, obtained regression curves for all matrices of interest showed no statistical differences of their slopes and intercepts, validating the method for the matrix effect correction in relevant environmental samples. The limits of detection and quantification of the method were as low as 5 and 10 ng/l respectively for the three compounds. Spiked Evian(©) and river water samples at two different concentrations (30 and 130 ng/l) showed mean recoveries between 86 and 109%, and between 90 and 133% respectively. Calibration curves established in spiked Evian(©) water samples between 10 and 1000 ng/l showed r(2) values above 0.989. Monitoring of a typical vineyard river showed peaks of pollution by glyphosate and AMPA during main rain events, sometimes above the legal threshold of 100 ng/l, suggesting the diffuse export of these compounds by surface runoff. The depth profile sampled in the adjacent lake near a waste water treatment plant outlet showed a concentration peak of AMPA at 25m depth, indicating its release with treated urban wastewater.

  13. NMDA and AMPA/kainate glutamatergic receptors in the prelimbic medial prefrontal cortex modulate the elaborated defensive behavior and innate fear-induced antinociception elicited by GABAA receptor blockade in the medial hypothalamus.

    PubMed

    de Freitas, Renato Leonardo; Salgado-Rohner, Carlos José; Biagioni, Audrey Francisco; Medeiros, Priscila; Hallak, Jaime Eduardo Cecílio; Crippa, José Alexandre S; Coimbra, Norberto Cysne

    2014-06-01

    The aim of the present study was to investigate the involvement of N-methyl-d-aspartate (NMDA) and amino-3-hydroxy-5-methyl-isoxazole-4-proprionate (AMPA)/kainate receptors of the prelimbic (PL) division of the medial prefrontal cortex (MPFC) on the panic attack-like reactions evoked by γ-aminobutyric acid-A receptor blockade in the medial hypothalamus (MH). Rats were pretreated with NaCl 0.9%, LY235959 (NMDA receptor antagonist), and NBQX (AMPA/kainate receptor antagonist) in the PL at 3 different concentrations. Ten minutes later, the MH was treated with bicuculline, and the defensive responses were recorded for 10 min. The antagonism of NMDA receptors in the PL decreased the frequency and duration of all defensive behaviors evoked by the stimulation of the MH and reduced the innate fear-induced antinociception. However, the pretreatment of the PL cortex with NBQX was able to decrease only part of defensive responses and innate fear-induced antinociception. The present findings suggest that the NMDA-glutamatergic system of the PL is critically involved in panic-like responses and innate fear-induced antinociception and those AMPA/kainate receptors are also recruited during the elaboration of fear-induced antinociception and in panic attack-related response. The activation of the glutamatergic neurotransmission of PL division of the MPFC during the elaboration of oriented behavioral reactions elicited by the chemical stimulation of the MH recruits mainly NMDA receptors in comparison with AMPA/kainate receptors.

  14. Dual element ((15)N/(14)N, (13)C/(12)C) isotope analysis of glyphosate and AMPA by derivatization-gas chromatography isotope ratio mass spectrometry (GC/IRMS) combined with LC/IRMS.

    PubMed

    Mogusu, Emmanuel O; Wolbert, J Benjamin; Kujawinski, Dorothea M; Jochmann, Maik A; Elsner, Martin

    2015-07-01

    To assess sources and degradation of the herbicide glyphosate [N-(phosphonomethyl) glycine] and its metabolite AMPA (aminomethylphosphonic acid), concentration measurements are often inconclusive and even (13)C/(12)C analysis alone may give limited information. To advance isotope ratio analysis of an additional element, we present compound-specific (15)N/(14)N analysis of glyphosate and AMPA by a two step derivatization in combination with gas chromatography/isotope ratio mass spectrometry (GC/IRMS). The N-H group was derivatized with isopropyl chloroformate (iso-PCF), and remaining acidic groups were subsequently methylated with trimethylsilyldiazomethane (TMSD). Iso-PCF treatment at pH <10 gave too low (15)N/(14)N ratios indicating an incomplete derivatization; in contrast, too high (15)N/(14)N ratios at pH >10 indicated decomposition of the derivative. At pH 10, and with an excess of iso-PCF by 10-24, greatest yields and accurate (15)N/(14)N ratios were obtained (deviation from elemental analyzer-IRMS: -0.2 ± 0.9% for glyphosate; -0.4 ± 0.7% for AMPA). Limits for accurate δ(15)N analysis of glyphosate and AMPA were 150 and 250 ng injected, respectively. A combination of δ(15)N and δ(13)C analysis by liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) (1) enabled an improved distinction of commercial glyphosate products and (2) showed that glyphosate isotope values during degradation by MnO2 clearly fell ou