Publications by authors named "Delphine Bouchet"

17 Publications

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NMDA receptor membrane dynamics tunes the firing pattern of midbrain dopaminergic neurons.

J Physiol 2021 Mar 2. Epub 2021 Mar 2.

Interdisciplinary Institute for Neuroscience, Université de Bordeaux, UMR 5297, Bordeaux, F-33000, France.

Key Points: NMDA receptors (NMDARs) expressed by dopamine neurons of the ventral tegmental area (VTA) play a central role in glutamate synapse plasticity, neuronal firing and adaptative behaviours. The NMDAR surface dynamics shapes synaptic adaptation in hippocampal networks, as well as associative memory. We investigated the basic properties and role of the NMDAR surface dynamics on cultured mesencephalic and VTA dopamine neurons in rodents. Using a combination of single molecule imaging and electrophysiological recordings, we demonstrate that NMDARs are highly diffusive at the surface of mesencephalic dopamine neurons. Unexpectedly, the NMDAR membrane dynamics per se regulates the firing pattern of VTA dopaminergic neurons, probably through a functional interplay between NMDARs receptors and small-conductance calcium-dependent potassium (SK) channels.

Abstract: Midbrain dopaminergic (DA) neurons play a central role in major physiological brain functions, and their dysfunctions have been associated with neuropsychiatric diseases. The activity of midbrain DA neurons is controlled by ion channels and neurotransmitter receptors, such as the glutamate NMDA receptor (NMDAR) and small-conductance calcium-dependent potassium (SK) channels. However, the cellular mechanisms through which these channels tune the firing pattern of midbrain DA neurons remain unclear. Here, we investigated whether the surface dynamics and distribution of NMDARs tunes the firing pattern of midbrain DA neurons. Using a combination of single molecule imaging and electrophysiological recordings, we report that NMDARs are highly diffusive at the surface of cultured midbrain DA neurons from rodents and humans. Reducing acutely the NMDAR membrane dynamics, which leaves the ionotropic function of the receptor intact, robustly altered the firing pattern of midbrain DA neurons without altering synaptic glutamatergic transmission. The reduction of NMDAR surface dynamics reduced apamin (SK channel blocker)-induced firing change and the distribution of SK3 channels in DA neurons. Together, these data show that the surface dynamics of NMDAR, and not solely its ionotropic function, tune the firing pattern of midbrain DA neurons partly through a functional interplay with SK channel function.
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http://dx.doi.org/10.1113/JP281104DOI Listing
March 2021

Distance-dependent regulation of NMDAR nanoscale organization along hippocampal neuron dendrites.

Proc Natl Acad Sci U S A 2020 09 14;117(39):24526-24533. Epub 2020 Sep 14.

Interdisciplinary Institute for Neuroscience, University of Bordeaux, UMR 5297, 33076 Bordeaux, France;

Hippocampal pyramidal neurons are characterized by a unique arborization subdivided in segregated dendritic domains receiving distinct excitatory synaptic inputs with specific properties and plasticity rules that shape their respective contributions to synaptic integration and action potential firing. Although the basal regulation and plastic range of proximal and distal synapses are known to be different, the composition and nanoscale organization of key synaptic proteins at these inputs remains largely elusive. Here we used superresolution imaging and single nanoparticle tracking in rat hippocampal neurons to unveil the nanoscale topography of native GluN2A- and GluN2B-NMDA receptors (NMDARs)-which play key roles in the use-dependent adaptation of glutamatergic synapses-along the dendritic arbor. We report significant changes in the nanoscale organization of GluN2B-NMDARs between proximal and distal dendritic segments, whereas the topography of GluN2A-NMDARs remains similar along the dendritic tree. Remarkably, the nanoscale organization of GluN2B-NMDARs at proximal segments depends on their interaction with calcium/calmodulin-dependent protein kinase II (CaMKII), which is not the case at distal segments. Collectively, our data reveal that the nanoscale organization of NMDARs changes along dendritic segments in a subtype-specific manner and is shaped by the interplay with CaMKII at proximal dendritic segments, shedding light on our understanding of the functional diversity of hippocampal glutamatergic synapses.
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http://dx.doi.org/10.1073/pnas.1922477117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7533699PMC
September 2020

Human Autoantibodies Against N-Methyl-D-Aspartate Receptor Modestly Alter Dopamine D1 Receptor Surface Dynamics.

Front Psychiatry 2019 13;10:670. Epub 2019 Sep 13.

Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, Bordeaux, France.

Circulating autoantibodies directed against extracellular domains of the glutamatergic N-methyl-D-aspartate receptors (NMDAR-Ab) elicit psychotic symptoms in humans and behavioral deficits in animal models. Recent advances suggest that NMDAR-Ab exert their pathogenic action by altering the trafficking of NMDAR, which results in a synaptic NMDAR hypofunction consistent with the consensual glutamatergic hypothesis of psychotic disorders. Yet, dysfunction in the dopaminergic signaling is also proposed to be at the core of psychotic disorders. Since NMDAR and dopamine D1 receptors (D1R) form membrane signaling complexes, we investigated whether NMDAR-Ab purified from patients with NMDAR-encephalitis or schizophrenia impaired D1R surface dynamics. As previous data demonstrated that NMDAR-Ab, at least from NMDAR-encephalitis patients, mainly bind to hippocampal NMDAR, we used single nanoparticle imaging to track D1R specifically at the surface of hippocampal neurons that were exposed to either purified G type immunoglobulins (IgGs) from NMDAR-Ab seropositive patients suffering from NMDAR-encephalitis or schizophrenia, or control IgGs from healthy NMDAR-Ab seropositive or seronegative subjects. We report that overnight incubation with NMDAR-Ab from patients, but not from healthy carriers, decreased the surface dynamics of D1R compared with NMDAR-Ab seronegative IgGs. This decrease was abolished, and even reversed, in D1R mutant that cannot physically interact with NMDAR. Overall, our data indicate that NMDAR-Ab from patients with psychotic symptoms alter the trafficking of D1R, likely through the surface crosstalk between NMDAR and D1R.
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http://dx.doi.org/10.3389/fpsyt.2019.00670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6754069PMC
September 2019

Aquaporin-4 Surface Trafficking Regulates Astrocytic Process Motility and Synaptic Activity in Health and Autoimmune Disease.

Cell Rep 2019 06;27(13):3860-3872.e4

Interdisciplinary Institute for NeuroSciences, CNRS UMR 5297, 33077 Bordeaux, France; Université de Bordeaux, 33077 Bordeaux, France. Electronic address:

Astrocytes constantly adapt their ramified morphology in order to support brain cell assemblies. Such plasticity is partly mediated by ion and water fluxes, which rely on the water channel aquaporin-4 (AQP4). The mechanism by which this channel locally contributes to process dynamics has remained elusive. Using a combination of single-molecule and calcium imaging approaches, we here investigated in hippocampal astrocytes the dynamic distribution of the AQP4 isoforms M1 and M23. Surface AQP4-M1 formed small aggregates that contrast with the large AQP4-M23 clusters that are enriched near glutamatergic synapses. Strikingly, stabilizing surface AQP4-M23 tuned the motility of astrocyte processes and favors glutamate synapse activity. Furthermore, human autoantibodies directed against AQP4 from neuromyelitis optica (NMO) patients impaired AQP4-M23 dynamic distribution and, consequently, astrocyte process and synaptic activity. Collectively, it emerges that the membrane dynamics of AQP4 isoform regulate brain cell assemblies in health and autoimmune brain disease targeting AQP4.
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http://dx.doi.org/10.1016/j.celrep.2019.05.097DOI Listing
June 2019

Differential Nanoscale Topography and Functional Role of GluN2-NMDA Receptor Subtypes at Glutamatergic Synapses.

Neuron 2018 10 27;100(1):106-119.e7. Epub 2018 Sep 27.

Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, 33000 Bordeaux, France; CNRS, IINS UMR 5297, Bordeaux, France. Electronic address:

NMDA receptors (NMDARs) play key roles in the use-dependent adaptation of glutamatergic synapses underpinning memory formation. In the forebrain, these plastic processes involve the varied contributions of GluN2A- and GluN2B-containing NMDARs that have different signaling properties. Although the molecular machinery of synaptic NMDAR trafficking has been under scrutiny, the postsynaptic spatial organization of these two receptor subtypes has remained elusive. Here, we used super-resolution imaging of NMDARs in rat hippocampal synapses to unveil the nanoscale topography of native GluN2A- and GluN2B-NMDARs. Both subtypes were found to be organized in separate nanodomains that vary over the course of development. Furthermore, GluN2A- and GluN2B-NMDAR nanoscale organizations relied on distinct regulatory mechanisms. Strikingly, the selective rearrangement of GluN2A- and GluN2B-NMDARs, with no overall change in NMDAR current amplitude, allowed bi-directional tuning of synaptic LTP. Thus, GluN2A- and GluN2B-NMDAR nanoscale organizations are differentially regulated and seem to involve distinct signaling complexes during synaptic adaptation.
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http://dx.doi.org/10.1016/j.neuron.2018.09.012DOI Listing
October 2018

Dynamic disorganization of synaptic NMDA receptors triggered by autoantibodies from psychotic patients.

Nat Commun 2017 11 27;8(1):1791. Epub 2017 Nov 27.

Univ. de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, 33077, Bordeaux, France.

The identification of circulating autoantibodies against neuronal receptors in neuropsychiatric disorders has fostered new conceptual and clinical frameworks. However, detection reliability, putative presence in different diseases and in health have raised questions about potential pathogenic mechanism mediated by autoantibodies. Using a combination of single molecule-based imaging approaches, we here ascertain the presence of circulating autoantibodies against glutamate NMDA receptor (NMDAR-Ab) in about 20% of psychotic patients diagnosed with schizophrenia and very few healthy subjects. NMDAR-Ab from patients and healthy subjects do not compete for binding on native receptor. Strikingly, NMDAR-Ab from patients, but not from healthy subjects, specifically alter the surface dynamics and nanoscale organization of synaptic NMDAR and its anchoring partner the EphrinB2 receptor in heterologous cells, cultured neurons and in mouse brain. Functionally, only patients' NMDAR-Ab prevent long-term potentiation at glutamatergic synapses, while leaving NMDAR-mediated calcium influx intact. We unveil that NMDAR-Ab from psychotic patients alter NMDAR synaptic transmission, supporting a pathogenically relevant role.
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http://dx.doi.org/10.1038/s41467-017-01700-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702610PMC
November 2017

Stress hormone rapidly tunes synaptic NMDA receptor through membrane dynamics and mineralocorticoid signalling.

Sci Rep 2017 08 14;7(1):8053. Epub 2017 Aug 14.

University de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000, Bordeaux, France.

Stress hormones, such as corticosteroids, modulate the transmission of hippocampal glutamatergic synapses and NMDA receptor (NMDAR)-dependent synaptic plasticity, favouring salient behavioural responses to the environment. The corticosterone-induced synaptic adaptations partly rely on changes in NMDAR signalling, although the cellular pathway underlying this effect remains elusive. Here, we demonstrate, using single molecule imaging and electrophysiological approaches in hippocampal neurons, that corticosterone specifically controls GluN2B-NMDAR surface dynamics and synaptic content through mineralocorticoid signalling. Strikingly, extracellular corticosterone was sufficient to increase the trapping of GluN2B-NMDAR within synapses. Functionally, corticosterone-induced potentiation of AMPA receptor content in synapses required the changes in NMDAR surface dynamics. These high-resolution imaging data unveiled that, in hippocampal networks, corticosterone is a natural, potent, fast and specific regulator of GluN2B-NMDAR membrane trafficking, tuning NMDAR-dependent synaptic adaptations.
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http://dx.doi.org/10.1038/s41598-017-08695-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5556050PMC
August 2017

Co-agonists differentially tune GluN2B-NMDA receptor trafficking at hippocampal synapses.

Elife 2017 06 9;6. Epub 2017 Jun 9.

Interdisciplinary Institute for NeuroSciences, CNRS UMR 5297, Bordeaux, France.

The subunit composition of synaptic NMDA receptors (NMDAR), such as the relative content of GluN2A- and GluN2B-containing receptors, greatly influences the glutamate synaptic transmission. Receptor co-agonists, glycine and D-serine, have intriguingly emerged as potential regulators of the receptor trafficking in addition to their requirement for its activation. Using a combination of single-molecule imaging, biochemistry and electrophysiology, we show that glycine and D-serine relative availability at rat hippocampal glutamatergic synapses regulate the trafficking and synaptic content of NMDAR subtypes. Acute manipulations of co-agonist levels, both ex vivo and in vitro, unveil that D-serine alter the membrane dynamics and content of GluN2B-NMDAR, but not GluN2A-NMDAR, at synapses through a process requiring PDZ binding scaffold partners. In addition, using FRET-based FLIM approach, we demonstrate that D-serine rapidly induces a conformational change of the GluN1 subunit intracellular C-terminus domain. Together our data fuels the view that the extracellular microenvironment regulates synaptic NMDAR signaling.
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http://dx.doi.org/10.7554/eLife.25492DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466419PMC
June 2017

Single nanoparticle tracking of [Formula: see text]-methyl-d-aspartate receptors in cultured and intact brain tissue.

Neurophotonics 2016 Oct 12;3(4):041808. Epub 2016 Jul 12.

Université de Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, 146 rue Leo Saignat, 33077 Bordeaux, France; Centre National de la Recherche Scientifique, Interdisciplinary Institute for Neuroscience, UMR 5297, 33000 Bordeaux, France.

Recent developments in single-molecule imaging have revealed many biological mechanisms, providing high spatial and temporal resolution maps of molecular events. In neurobiology, these techniques unveiled that plasma membrane neurotransmitter receptors and transporters laterally diffuse at the surface of cultured brain cells. The photostability of bright nanoprobes, such as quantum dots (QDs), has given access to neurotransmitter receptor tracking over long periods of time with a high spatial resolution. However, our knowledge has been restricted to cultured systems, i.e., neurons and organotypic slices, therefore lacking several aspects of the intact brain rheology and connectivity. Here, we used QDs to track single glutamatergic [Formula: see text]-methyl-d-aspartate receptors (NMDAR) in acute brain slices. By delivering functionalized nanoparticles in vivo through intraventricular injections to rats expressing genetically engineered-tagged NMDAR, we successfully tracked the receptors in native brain tissue. Comparing NMDAR tracking to different classical brain preparations (acute brain slices, cultured organotypic brain slices, and cultured neurons) revealed that the surface diffusion properties shared several features and are also influenced by the nature of the extracellular environment. Together, we describe the experimental procedures to track plasma membrane NMDAR in dissociated and native brain tissue, paving the way for investigations aiming at characterizing receptor diffusion biophysics in intact tissue and exploring the physiopathological roles of receptor surface dynamics.
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http://dx.doi.org/10.1117/1.NPh.3.4.041808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4940612PMC
October 2016

Surface dynamics of GluN2B-NMDA receptors controls plasticity of maturing glutamate synapses.

EMBO J 2014 Apr 3;33(8):842-61. Epub 2014 Mar 3.

Interdisciplinary Institute for Neuroscience University de Bordeaux UMR 5297, Bordeaux, France.

NMDA-type glutamate receptors (NMDAR) are central actors in the plasticity of excitatory synapses. During adaptive processes, the number and composition of synaptic NMDAR can be rapidly modified, as in neonatal hippocampal synapses where a switch from predominant GluN2B- to GluN2A-containing receptors is observed after the induction of long-term potentiation (LTP). However, the cellular pathways by which surface NMDAR subtypes are dynamically regulated during activity-dependent synaptic adaptations remain poorly understood. Using a combination of high-resolution single nanoparticle imaging and electrophysiology, we show here that GluN2B-NMDAR are dynamically redistributed away from glutamate synapses through increased lateral diffusion during LTP in immature neurons. Strikingly, preventing this activity-dependent GluN2B-NMDAR surface redistribution through cross-linking, either with commercial or with autoimmune anti-NMDA antibodies from patient with neuropsychiatric symptoms, affects the dynamics and spine accumulation of CaMKII and impairs LTP. Interestingly, the same impairments are observed when expressing a mutant of GluN2B-NMDAR unable to bind CaMKII. We thus uncover a non-canonical mechanism by which GluN2B-NMDAR surface dynamics plays a critical role in the plasticity of maturing synapses through a direct interplay with CaMKII.
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http://dx.doi.org/10.1002/embj.201386356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4194110PMC
April 2014

Single-molecule imaging of the functional crosstalk between surface NMDA and dopamine D1 receptors.

Proc Natl Acad Sci U S A 2013 Oct 14;110(44):18005-10. Epub 2013 Oct 14.

Interdisciplinary Institute for Neuroscience, Unité Mixte de Recherche (UMR) 5297, Université de Bordeaux, F-33000 Bordeaux, France.

Dopamine is a powerful modulator of glutamatergic neurotransmission and NMDA receptor-dependent synaptic plasticity. Although several intracellular cascades participating in this functional dialogue have been identified over the last few decades, the molecular crosstalk between surface dopamine and glutamate NMDA receptor (NMDAR) signaling still remains poorly understood. Using a combination of single-molecule detection imaging and electrophysiology in live hippocampal neurons, we demonstrate here that dopamine D1 receptors (D1Rs) and NMDARs form dynamic surface clusters in the vicinity of glutamate synapses. Strikingly, D1R activation or D1R/NMDAR direct interaction disruption decreases the size of these clusters, increases NMDAR synaptic content through a fast lateral redistribution of the receptors, and favors long-term synaptic potentiation. Together, these data demonstrate the presence of dynamic D1R/NMDAR perisynaptic reservoirs favoring a rapid and bidirectional surface crosstalk between receptors and set the plasma membrane as the primary stage of the dopamine-glutamate interplay.
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http://dx.doi.org/10.1073/pnas.1310145110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3816474PMC
October 2013

Regulation of dopamine D1 receptor dynamics within the postsynaptic density of hippocampal glutamate synapses.

PLoS One 2013 6;8(9):e74512. Epub 2013 Sep 6.

Univ. de Bordeaux, Interdisciplinary Institute for Neuroscience, Unité Mixte de recherche UMR 5297, Bordeaux, France ; Centre National de la Recherche Scientifique CNRS, IINS UMR 5297, Bordeaux, France.

Dopamine receptor potently modulates glutamate signalling, synaptic plasticity and neuronal network adaptations in various pathophysiological processes. Although key intracellular signalling cascades have been identified, the cellular mechanism by which dopamine and glutamate receptor-mediated signalling interplay at glutamate synapse remain poorly understood. Among the cellular mechanisms proposed to aggregate D1R in glutamate synapses, the direct interaction between D1R and the scaffold protein PSD95 or the direct interaction with the glutamate NMDA receptor (NMDAR) have been proposed. To tackle this question we here used high-resolution single nanoparticle imaging since it provides a powerful way to investigate at the sub-micron resolution the dynamic interaction between these partners in live synapses. We demonstrate in hippocampal neuronal networks that dopamine D1 receptors (D1R) laterally diffuse within glutamate synapses, in which their diffusion is reduced. Disrupting the interaction between D1R and PSD95, through genetical manipulation and competing peptide, did not affect D1R dynamics in glutamatergic synapses. However, preventing the physical interaction between D1R and the GluN1 subunit of NMDAR abolished the synaptic stabilization of diffusing D1R. Together, these data provide direct evidence that the interaction between D1R and NMDAR in synapses participate in the building of the dopamine-receptor-mediated signalling, and most likely to the glutamate-dopamine cross-talk.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074512PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3765443PMC
June 2014

Disrupted surface cross-talk between NMDA and Ephrin-B2 receptors in anti-NMDA encephalitis.

Brain 2012 May;135(Pt 5):1606-21

CNRS, Interdisciplinary Institute for Neurosciences UMR 5297, Universite de Bordeaux, 146 rue Leo Saignat, Bordeaux, France.

Autoimmune synaptic encephalitides are recently described human brain diseases leading to psychiatric and neurological syndromes through inappropriate brain-autoantibody interactions. The most frequent synaptic autoimmune encephalitis is associated with autoantibodies against extracellular domains of the glutamatergic N-methyl-d-aspartate receptor, with patients developing psychotic and neurological symptoms in an autoantibody titre-dependent manner. Although N-methyl-d-aspartate receptors are the primary target of these antibodies, the cellular and molecular pathway(s) that rapidly lead to N-methyl-d-aspartate receptor dysfunction remain poorly understood. In this report, we used a unique combination of high-resolution nanoparticle and bulk live imaging approaches to demonstrate that anti-N-methyl-d-aspartate receptor autoantibodies from patients with encephalitis strongly alter, in a time-dependent manner, the surface content and trafficking of GluN2-NMDA receptor subtypes. Autoantibodies laterally displaced surface GluN2A-NMDA receptors out of synapses and completely blocked synaptic plasticity. This loss of extrasynaptic and synaptic N-methyl-d-aspartate receptor is prevented both in vitro and in vivo, by the activation of EPHB2 receptors. Indeed, the anti-N-methyl-d-aspartate receptor autoantibodies weaken the interaction between the extracellular domains of the N-methyl-d-aspartate and Ephrin-B2 receptors. Together, we demonstrate that the anti-N-methyl-d-aspartate receptor autoantibodies from patients with encephalitis alter the dynamic retention of synaptic N-methyl-d-aspartate receptor through extracellular domain-dependent mechanism(s), shedding new light on the pathology of the neurological and psychiatric disorders observed in these patients and opening possible new therapeutic strategies.
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http://dx.doi.org/10.1093/brain/aws092DOI Listing
May 2012

Dynamic and specific interaction between synaptic NR2-NMDA receptor and PDZ proteins.

Proc Natl Acad Sci U S A 2010 Nov 25;107(45):19561-6. Epub 2010 Oct 25.

Laboratory for Cellular Physiology of the Synapse, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5091, 33077 Bordeaux, France.

The relative content of NR2 subunits in the NMDA receptor confers specific signaling properties and plasticity to synapses. However, the mechanisms that dynamically govern the retention of synaptic NMDARs, in particular 2A-NMDARs, remain poorly understood. Here, we investigate the dynamic interaction between NR2 C termini and proteins containing PSD-95/Discs-large/ZO-1 homology (PDZ) scaffold proteins at the single molecule level by using high-resolution imaging. We report that a biomimetic divalent competing ligand, mimicking the last 15 amino acids of NR2A C terminus, specifically and efficiently disrupts the interaction between 2A-NMDARs, but not 2B-NMDARs, and PDZ proteins on the time scale of minutes. Furthermore, displacing 2A-NMDARs out of synapses lead to a compensatory increase in synaptic NR2B-NMDARs, providing functional evidence that the anchoring mechanism of 2A- or 2B-NMDARs is different. These data reveal an unexpected role of the NR2 subunit divalent arrangement in providing specific anchoring within synapses, highlighting the need to study such dynamic interactions in native conditions.
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http://dx.doi.org/10.1073/pnas.1002690107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2984211PMC
November 2010

A single in vivo exposure to cocaine abolishes endocannabinoid-mediated long-term depression in the nucleus accumbens.

J Neurosci 2004 Aug;24(31):6939-45

Equipe Institut National de la Santé et de la Recherche Médicale Avenir (Plasticité Synaptique: Maturation et Addiction), Centre National de la Recherche Scientifique 5091, Institut Magendie des Neurosciences, 33077 Bordeaux Cedex, France.

In the nucleus accumbens (NAc), a key structure to the effects of all addictive drugs, presynaptic cannabinoid CB1 receptors (CB1Rs) and postsynaptic metabotropic glutamate 5 receptors (mGluR5s) are the principal effectors of endocannabinoid (eCB)-mediated retrograde long-term depression (LTD) (eCB-LTD) at the prefrontal cortex-NAc synapses. Both CB1R and mGluR5 are involved in cocaine-related behaviors; however, the impact of in vivo cocaine exposure on eCB-mediated retrograde synaptic plasticity remains unknown. Electrophysiological and biochemical approaches were used, and we report that a single in vivo cocaine administration abolishes eCB-LTD. This effect of cocaine was not present in D1 dopamine receptor (D1R) -/- mice and was prevented when cocaine was coadministered with the selective D1R antagonist 8-chloro-2,3,4,5-tetrahydro-3-5-1h-3-benzazepin-7-ol (0.5 mg/kg) or with the NMDA receptor (NMDAR) blocker (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate (1 mg/kg), suggesting the involvement of D1R and NMDAR. We found that the cocaine-induced blockade of retrograde signaling was correlated with enhanced expression levels of Homer scaffolding proteins containing the coiled-coil domain and accompanied by a strong reduction of mGluR5 surface expression. The results suggest that cocaine-induced loss of eCB retrograde signaling is caused by a reduction in the ability of mGluR5 to translate anterograde glutamate transmission into retrograde eCB signaling.
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http://dx.doi.org/10.1523/JNEUROSCI.0671-04.2004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6729592PMC
August 2004

Differential sensitivity of endothelial cells of various species to apoptosis induced by gene transfer of Fas ligand: role of FLIP levels.

Mol Med 2002 Oct;8(10):612-23

Institut National de la Santé et de la Recherche Médicale U437, Nantes, France.

Background: Fas ligand expression by cells of the vessel wall has been proposed to play a role in normal and pathologic conditions. Genetic engineering of vascularized organs for endothelial cell (EC) expression of FasL could protect the endothelium and underlying tissues from infiltrating Fas+ leukocytes. Nevertheless, the endogenous expression of FasL by ECs of different species and the potential deleterious effects of enforced FasL expression by ECs are largely unknown. In human ECs, levels of FLICE/caspase 8-inhibitory protein (FLIP) have been shown to control apoptosis mediated by Fas.

Materials And Methods: Cell surface expression of FasL in rat, mouse, human, and pig ECs was obtained using recombinant adenoviruses or transient plasmid transfection assays. FasL expression was evaluated by FACS analysis and cytotoxicity assays. Apoptosis was evaluated using annexin V, TUNEL, and cytotoxicity assays. FLIP levels were evaluated by Western blot analysis and overexpression was obtained by transient transfection.

Results: Analysis of ECs from different species showed that FasL was predominantly present in the cytoplasm, and depending on the species, little or no cell surface expression was detected. Enforced cell surface expression of FasL on rat or mouse ECs, either in culture or within the vessel wall resulted in massive apoptosis. In contrast, porcine or human ECs were completely resistant to apoptosis mediated by Fas-FasL interaction. Markedly reduced FLIP levels were observed in rat and mouse ECs compared to human and porcine ECs. Overexpression of FLIP in rat ECs conferred protection against cell surface expression of FasL.

Conclusions: The consequences of FasL overexpression depend on the subcellular compartment and species in which FasL enforced expression is targeted and this is at least partially related to FLIP levels.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2039943PMC
October 2002

Gene transfer of heme oxygenase-1 and carbon monoxide delivery inhibit chronic rejection.

Am J Transplant 2002 Aug;2(7):581-92

Institut National de la Santé Et de la Recherche Médicale U437, Institut de Transplantation et de Recherche en Transplantation and CHU de Nantes, France.

The hallmark of chronic rejection is the occlusion of the artery lumen by intima hyperplasia as a consequence of leukocyte infiltration and vascular smooth muscle cell (VSMC) migration and proliferation. Heme oxygenase-1 (HO-1) is a tissue protective molecule which degrades heme into carbon monoxide (CO), free iron and biliverdin. We analyzed the effects of HO-1 gene transfer into the vessel wall using an adenoviral vector (AdHO-1) and of CO delivery in a model of chronic allogeneic aorta rejection in rats. Carbon monoxide treatment was achieved by a new pharmacological approach in transplantation using methylene chloride (MC), which releases CO after degradation. AdHO-1-mediated gene transfer into aorta endothelial cells (ECs) or CO delivery resulted in a significant reduction in intimal thickness compared to untreated or noncoding adenovirus-treated controls. Aortas transduced with AdHO-1 or treated with CO showed a reduction in the number of leukocytes as well as in the expression of adhesion molecules, costimulatory molecules and cytokines, with the gene transfer treatment displaying a more pronounced effect than the CO treatment. Conversely, CO inhibited VSMC accumulation in the intima more efficiently than AdHO-1 treatment. Gene transfer of HO-1 and pharmacological manipulation of CO are novel approaches to the analysis and treatment of chronic rejection.
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http://dx.doi.org/10.1034/j.1600-6143.2002.20702.xDOI Listing
August 2002