Modulation of AMPA receptor surface diffusion restores hippocampal plasticity and memory in Huntington’s disease models

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Rapid and Differential Regulation of AMPA and Kainate Receptors at Hippocampal Mossy Fibre Synapses by PICK1 and GRIP

AbstractWe identified four PDZ domain-containing proteins, syntenin, PICK1, GRIP, and PSD95, as interactors with the kainate receptor (KAR) subunits GluR52b, GluR52c, and GluR6. Of these, we show that both GRIP and PICK1 interactions are required to maintain KAR-mediated synaptic function at mossy fiber-CA3 synapses. In addition, PKCα can phosphorylate ct-GluR52b at residues S880 and S886, and PKC activity is required to maintain KAR-mediated synaptic responses. We propose that PICK1 targets PKCα to phosphorylate KARs, causing their stabilization at the synapse by an interaction with GRIP. Importantly, this mechanism is not involved in the constitutive recycling of AMPA receptors since blockade of PDZ interactions can simultaneously increase AMPAR- and decrease KAR-mediated synaptic transmission at the same population of synapses

Distribution subcellulaire des récepteurs du glutamate de type kaïnate

Les récepteurs kaïnates sont des récepteurs ionotropiques du glutamate impliqués dans la régulation de l'activité des réseaux neuronaux. Les récepteurs kaïnates peuvent être pré-synaptiques mais également péri-synaptiques. Les mécanismes qui distribuent ces récepteurs dans les sous-domaines des neurones sont peu documentés.Il existe différents variants d'épissage C-terminaux des sous-unités GluR5-7 des récepteurs kaïnates. Ce domaine cytosolique constitue un site de régulation de la distribution subcellulaire des récepteurs kaïnate. L'étude de la distribution de ces sous-unités par immunocytochimie et imagerie de fluorescence dans des neurones d'hippocampe en culture permet de mettre en évidence qur l'épissage alternatif et la composition en sous-unités déterminent l'adressage membranaire de ces récepteurs. Ces résultats soulignent le rôle essentiel de l'épissage alternatif dans la distribution subcellulaire des récepteurs kaïnate.Glutamate receptors of the kainate type (KA receptors) have recently emerged as key players in the modulation of neuronal network activity. The various roles of KA receptors critically depend on their precise subcellular localization in presynaptic, postsynaptic or extrasynaptic domains. Subcellular localization of KA receptors has been mainly inferred from electrophysiological studies with the help of selective pharmacological tools and KA receptor mutant mice. These studies highlight the diversity of subcellular localization for KA receptors. It is then important to understand the molecular mechanisms underlying the polarized trafficking of KA receptors in distinct neuronal domains. This thesis shed light on the trafficking and membrane delivery of KA receptor subunits isoforms.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

Neuronal Activity and Intracellular Calcium Levels Regulate Intracellular Transport of Newly Synthesized AMPAR

International audienceRegulation of AMPA receptor (AMPAR) trafficking is a key modulator of excitatory synaptic transmission; however, intracellular vesicular transport of newly synthesized AMPARs has been little studied due to technical limitations. By combining molecular tools with imaging strategies in cultured rat hippocampal neurons, we found that vesicles containing newly synthesized, GluA1-subunit-containing AMPARs are transported antero- and retrogradely at a mean speed of 1.5 μm.s−1. Synaptic activity and variations in intracellular calcium levels bidirectionally modulate GluA1 transport. Chemical long-term potentiation (cLTP) initially induces a halt in GluA1 transport, followed by a sustained increase, while acute glutamate uncaging on synaptic spines arrests vesicular movements. GluA1 phosphomimetic mutants preferentially travel to the dendritic tip, probably to replenish extrasynaptic pools, distal to the soma. Our findings indicate that AMPAR intracellular transport is highly regulated during synaptic plasticity and likely controls AMPAR numbers at the plasma membrane

Fluorescence microscopy of single autofluorescent proteins for cellular biology

In this paper we review the applicability of autofluorescent proteins for single-molecule imaging in biology. The photophysical characteristics of several mutants of the Green Fluorescent Protein (GFP) and those of DsRed are compared and critically discussed for their use in cellular biology. The alternative use of two-photon excitation at the single-molecule level or Fluorescence Correlation Spectroscopy is envisaged for the study of individual autofluorescent proteins. Single-molecule experiments performed in live cells using eGFP and preferably eYFP fusion proteins are reviewed. Finally, the first use at the single-molecule level of citrine, a more photostable variant of the eYFP is reported when fused to a receptor for neurotransmitter in live cells

Fluorescence microscopy of single autofluorescent proteins for cellular biology

In this paper we review the applicability of autofluorescent proteins for single-molecule imaging in biology. The photophysical characteristics of several mutants of the Green Fluorescent Protein (GFP) and those of DsRed are compared and critically discussed for their use in cellular biology. The alternative use of two-photon excitation at the single-molecule level or Fluorescence Correlation Spectroscopy is envisaged for the study of individual autofluorescent proteins. Single-molecule experiments performed in live cells using eGFP and preferably eYFP fusion proteins are reviewed. Finally, the first use at the single-molecule level of citrine, a more photostable variant of the eYFP is reported when fused to a receptor for neurotransmitter in live cells

Role of intracellular trafficking of AMPAR during LTP

International audienceAbundance of AMPA receptors (AMPAR) at synapse is essential for the establishment and maintenance of synaptic function. Their synaptic localization is dependent on a highly dynamic exocytosis, endocytosis and plasma membrane mobility events. Using our new biochemical tool combined with photonic live imaging, we controlled and followed the intracellular transport of tagged GluA1 containing receptors in cultured rat hippocampal neurons. Analyzes are performed for GluA1 WT and mutants of GluA1 C-terminus domain in basal condition and during LTP. In organotypic hippocampal slices we combine imaging and electrophysiology experiments to analyze the impact of intracellular transport of AMPAR on LTP. Localization of AMPAR is regulated by their intracellular trafficking thru interaction of their C-terminus domains with different intracellular partners. These interactions play a major rule in the exocytosis and localization of the receptor at the plasma membrane both in basal condition of during cLTP. In hippocampal slice intracellular transport of AMPAR plays a major role during LTP

Role of intracellular trafficking of AMPAR during LTP

International audienceAbundance of AMPA receptors (AMPAR) at synapse is essential for the establishment and maintenance of synaptic function. Their synaptic localization is dependent on a highly dynamic exocytosis, endocytosis and plasma membrane mobility events