Thu, 21 Aug 2008 09:52:30 BST CiteULike: lechristophe's dendritic_spines http://www.citeulike.org/user/lechristophe/tag/dendritic_spines CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/lechristophe/article/3080826 <i>The Journal of physiology, Vol. 558, No. Pt 2. (15 July 2004), pp. 503-512.</i><br /><br />Dendritic spines are the site of most excitatory connections in the hippocampus. We have investigated the diffusibility of a membrane-bound green fluorescent protein (mGFP) within the inner leaflet of the plasma membrane using Fluorescence Recovery After Photobleaching. In dendritic spines the diffusion of mGFP was significantly retarded relative to the dendritic shaft. In parallel, we have assessed the motility of dendritic spines, and found an inverse correlation between spine motility and the rate of diffusion of mGFP. We then tested the influence of glutamate receptor activation or blockade, and the involvement of the actin cytoskeleton (using latrunculin A) on spine motility and mGFP diffusion. These results show that glutamate receptors regulate the mobility of molecules in the inner leaflet of the plasma membrane through an action upon the actin cytoskeleton, suggesting a novel mechanism for the regulation of postsynaptic receptor density and composition. AMPA-receptor activation regulates the diffusion of a membrane marker in parallel with dendritic spine motility in the mouse hippocampus. DA Richards V De Paola P Caroni BH Gähwiler RA McKinney doi:10.1113/jphysiol.2004.062091 The Journal of physiology, Vol. 558, No. Pt 2. (15 July 2004), pp. 503-512. 2008-08-04T12:37:08-00:00 2004 The Journal of physiology 0022-3751 558 Pt 2 503 512 ampar dendritic_spines frap membrane_diffusion slice_culture http://www.citeulike.org/user/lechristophe/article/2868886 <i>Neuron, Vol. 58, No. 4. (22 May 2008), pp. 472-497.</i><br /><br />Among diverse factors regulating excitatory synaptic transmission, the abundance of postsynaptic glutamate receptors figures prominently in molecular memory and learning-related synaptic plasticity. To allow for both long-term maintenance of synaptic transmission and acute changes in synaptic strength, the relative rates of glutamate receptor insertion and removal must be tightly regulated. Interactions with scaffolding proteins control the targeting and signaling properties of glutamate receptors within the postsynaptic membrane. In addition, extrasynaptic receptor populations control the equilibrium of receptor exchange at synapses and activate distinct signaling pathways involved in plasticity. Here, we review recent findings that have shaped our current understanding of receptor mobility between synaptic and extrasynaptic compartments at glutamatergic synapses, focusing on AMPA and NMDA receptors. We also examine the cooperative relationship between intracellular trafficking and surface diffusion of glutamate receptors that underlies the expression of learning-related synaptic plasticity. Glutamate receptor dynamics in dendritic microdomains. TM Newpher MD Ehlers doi:10.1016/j.neuron.2008.04.030 Neuron, Vol. 58, No. 4. (22 May 2008), pp. 472-497. 2008-06-06T09:23:22-00:00 2008 Neuron 1097-4199 58 4 472 497 dendrites dendritic_spines endocytosis glur membrane_diffusion review http://www.citeulike.org/user/lechristophe/article/2895997 <i>Physiological reviews, Vol. 88, No. 2. (April 2008), pp. 769-840.</i><br /><br />Most synaptic inputs are made onto the dendritic tree. Recent work has shown that dendrites play an active role in transforming synaptic input into neuronal output and in defining the relationships between active synapses. In this review, we discuss how these dendritic properties influence the rules governing the induction of synaptic plasticity. We argue that the location of synapses in the dendritic tree, and the type of dendritic excitability associated with each synapse, play decisive roles in determining the plastic properties of that synapse. Furthermore, since the electrical properties of the dendritic tree are not static, but can be altered by neuromodulators and by synaptic activity itself, we discuss how learning rules may be dynamically shaped by tuning dendritic function. We conclude by describing how this reciprocal relationship between plasticity of dendritic excitability and synaptic plasticity has changed our view of information processing and memory storage in neuronal networks. Dendritic excitability and synaptic plasticity. PJ Sjöström EA Rancz A Roth M Häusser doi:10.1152/physrev.00016.2007 Physiological reviews, Vol. 88, No. 2. (April 2008), pp. 769-840. 2008-06-15T09:17:23-00:00 2008 Physiological reviews 0031-9333 88 2 769 840 dendritic_spines electrophysiology review http://www.citeulike.org/user/lechristophe/article/2737420 <i>Current biology : CB, Vol. 17, No. 20. (23 October 2007), pp. 1752-1758.</i><br /><br />Septins are GTP-binding proteins that polymerize into heteromeric filaments and form microscopic bundles or ring structures in vitro and in vivo. Because of these properties and their ability to associate with membrane, F-actin, and microtubules, septins have been generally regarded as cytoskeletal components [1, 2]. Septins are known to play roles in cytokinesis, in membrane trafficking, and as structural scaffolds; however, their function in neurons is poorly understood. Many members of the septin family, including Septin 7 (Sept7), were found by mass-spectrometry analysis of postsynaptic density (PSD) fractions of the brain [3, 4], suggesting a possible postsynaptic function of septins in neurons. We report that Sept7 is localized at the base of dendritic protrusions and at dendritic branch points in cultured hippocampal neurons--a distribution reminiscent of septin localization in the bud neck of budding yeast. Overexpression of Sept7 increased dendrite branching and the density of dendritic protrusions, whereas RNA interference (RNAi)-mediated knockdown of Sept7 led to reduced dendrite arborization and a greater proportion of immature protrusions. These data suggest that Sept7 is critical for spine morphogenesis and dendrite development during neuronal maturation. Role of Septin cytoskeleton in spine morphogenesis and dendrite development in neurons. T Tada A Simonetta M Batterton M Kinoshita D Edbauer M Sheng doi:10.1016/j.cub.2007.09.039 Current biology : CB, Vol. 17, No. 20. (23 October 2007), pp. 1752-1758. 2008-04-30T09:53:48-00:00 2007 Current biology : CB 0960-9822 17 20 1752 1758 cytosqueleton dendritic_spines neurites_growth http://www.citeulike.org/user/lechristophe/article/2669700 <i>Neuron, Vol. 57, No. 5. (13 March 2008), pp. 719-729.</i><br /><br />Summary Synapse function and plasticity depend on the physical structure of dendritic spines as determined by the actin cytoskeleton. We have investigated the organization of filamentous (F-) actin within individual spines on CA1 pyramidal neurons in rat hippocampal slices. Using two-photon photoactivation of green fluorescent protein fused to [beta]-actin, we found that a dynamic pool of F-actin at the tip of the spine quickly treadmilled to generate an expansive force. The size of a stable F-actin pool at the base of the spine depended on spine volume. Repeated two-photon uncaging of glutamate formed a third pool of F-actin and enlarged the spine. The spine often released this "enlargement pool" into the dendritic shaft, but the pool had to be physically confined by a spine neck for the enlargement to be long-lasting. Ca2+/calmodulin-dependent protein kinase II regulated this confinement. Thus, spines have an elaborate mechanical nature that is regulated by actin fibers. The Subspine Organization of Actin Fibers Regulates the Structure and Plasticity of Dendritic Spines Naoki Honkura Masanori Matsuzaki Jun Noguchi Graham Ellis-Davies Haruo Kasai doi:10.1016/j.neuron.2008.01.013 Neuron, Vol. 57, No. 5. (13 March 2008), pp. 719-729. 2008-04-14T16:24:42-00:00 2008 Neuron 57 5 719 729 actin cytosqueleton dendritic_spines photoactivation http://www.citeulike.org/user/lechristophe/article/2681007 <i>Neuroscience, Vol. In Press, Corrected Proof</i><br /><br />Many different forms of synaptic plasticity have been shown to ultimately modulate the number of AMPA-type glutamate receptors at the synapse. This trafficking involves lateral movements between synaptic and extrasynaptic sites at the neuron surface, as well as vesicular transport between the plasma membrane and intracellular compartments. Several new studies have shed light on the location and regulation of AMPA-type receptor (AMPAR) endocytosis, their intracellular sorting to divergent pathways at the level of endosomes, and the mechanism and sites of receptor recycling. This review summarizes this recent data on the trafficking along the endocytic pathway, and follows the path of internalized AMPAR from endocytosis up to sites of recycling. Endosomal trafficking of AMPA-type glutamate receptors H Hirling doi:10.1016/j.neuroscience.2008.02.057 Neuroscience, Vol. In Press, Corrected Proof 2008-04-17T08:12:05-00:00 Neuroscience In Press, Corrected Proof ampar dendritic_spines endocytosis neurons review http://www.citeulike.org/user/lechristophe/article/2108896 <i>Neuron, Vol. 55, No. 6. (20 September 2007), pp. 874-889.</i><br /><br />Summary Endocytosis of AMPA receptors and other postsynaptic cargo occurs at endocytic zones (EZs), stably positioned sites of clathrin adjacent to the postsynaptic density (PSD). The tight localization of postsynaptic endocytosis is thought to control spine composition and regulate synaptic transmission. However, the mechanisms that situate the EZ near the PSD and the role of spine endocytosis in synaptic transmission are unknown. Here, we report that a physical link between dynamin-3 and the postsynaptic adaptor Homer positions the EZ near the PSD. Disruption of dynamin-3 or its interaction with Homer uncouples the PSD from the EZ, resulting in synapses lacking postsynaptic clathrin. Loss of the EZ leads to a loss of synaptic AMPA receptors and reduced excitatory synaptic transmission that corresponds with impaired synaptic recycling. Thus, a physical link between the PSD and the EZ ensures localized endocytosis and recycling by recapturing and maintaining a proximate pool of cycling AMPA receptors. Postsynaptic Positioning of Endocytic Zones and AMPA Receptor Cycling by Physical Coupling of Dynamin-3 to Homer Jiuyi Lu Thomas Helton Thomas Blanpied Bence Racz Thomas Newpher Richard Weinberg Michael Ehlers doi:10.1016/j.neuron.2007.06.041 Neuron, Vol. 55, No. 6. (20 September 2007), pp. 874-889. 2007-12-13T23:42:15-00:00 2007 Neuron 55 6 874 889 ampar cultured_hippo_neurons dendritic_spines endocytosis synapse http://www.citeulike.org/user/lechristophe/article/2191090 <i>Neuron, Vol. 54, No. 6. (21 June 2007), pp. 933-947.</i><br /><br />Voltage-gated A-type K+ channel Kv4.2 subunits are highly expressed in the dendrites of hippocampal CA1 neurons. However, little is known about the subcellular distribution and trafficking of Kv4.2-containing channels. Here we provide evidence for activity-dependent trafficking of Kv4.2 in hippocampal spines and dendrites. Live imaging and electrophysiological recordings showed that Kv4.2 internalization is induced rapidly upon glutamate receptor stimulation. Kv4.2 internalization was clathrin mediated and required NMDA receptor activation and Ca2+ influx. In dissociated hippocampal neurons, mEPSC amplitude depended on functional Kv4.2 expression level and was enhanced by stimuli that induced Kv4.2 internalization. Long-term potentiation (LTP) induced by brief glycine application resulted in synaptic insertion of GluR1-containing AMPA receptors along with Kv4.2 internalization. We also found evidence of Kv4.2 internalization upon synaptically evoked LTP in CA1 neurons of hippocampal slice cultures. These results present an additional mechanism for synaptic integration and plasticity through the activity-dependent regulation of Kv4.2 channel surface expression. Regulation of dendritic excitability by activity-dependent trafficking of the A-type K+ channel subunit Kv4.2 in hippocampal neurons. J Kim SC Jung AM Clemens RS Petralia DA Hoffman doi:10.1016/j.neuron.2007.05.026 Neuron, Vol. 54, No. 6. (21 June 2007), pp. 933-947. 2008-01-03T10:19:57-00:00 2007 Neuron 0896-6273 54 6 933 947 dendrites dendritic_spines endocytosis kv neuronal_activity trafficking http://www.citeulike.org/user/lechristophe/article/977951 <i>Neuron, Vol. 52, No. 5. (7 December 2006), pp. 817-830.</i><br /><br />SummaryDendritic spines are micron-sized membrane protrusions receiving most excitatory synaptic inputs in the mammalian brain. Spines form and grow during long-term potentiation (LTP) of synaptic strength. However, the source of membrane for spine formation and enlargement is unknown. Here we report that membrane trafficking from recycling endosomes is required for the growth and maintenance of spines. Using live-cell imaging and serial section electron microscopy, we demonstrate that LTP-inducing stimuli promote the mobilization of recycling endosomes and vesicles into spines. Preventing recycling endosomal transport abolishes LTP-induced spine formation. Using a pH-sensitive recycling cargo, we show that exocytosis from recycling endosomes occurs locally in spines, is triggered by activation of synaptic NMDA receptors, and occurs concurrently with spine enlargement. Thus, recycling endosomes provide membrane for activity-dependent spine growth and remodeling, defining a novel membrane trafficking mechanism for spine morphological plasticity and providing a mechanistic link between structural and functional plasticity during LTP. Plasticity-Induced Growth of Dendritic Spines by Exocytic Trafficking from Recycling Endosomes Mikyoung Park Jennifer Salgado Linnaea Ostroff Thomas Helton Camenzind Robinson Kristen Harris Michael Ehlers doi:10.1016/j.neuron.2006.09.040 Neuron, Vol. 52, No. 5. (7 December 2006), pp. 817-830. 2006-12-07T14:15:09-00:00 2006 Neuron 52 5 817 830 dendritic_spines electron_microscopy endosomes live_cell_imaging membrane_insertion postsynaptic recycling tfr http://www.citeulike.org/user/lechristophe/article/935769 <i>PLoS Biology, Vol. 4, No. 11. (1 November 2006), e370.</i><br /><br />Most excitatory synapses terminate on dendritic spines. Spines vary in size, and their volumes are proportional to the area of the postsynaptic density (PSD) and synaptic strength. PSD-95 is an abundant multi-domain postsynaptic scaffolding protein that clusters glutamate receptors and organizes the associated signaling complexes. PSD-95 is thought to determine the size and strength of synapses. Although spines and their synapses can persist for months in vivo, PSD-95 and other PSD proteins have shorter half-lives in vitro, on the order of hours. To probe the mechanisms underlying synapse stability, we measured the dynamics of synaptic PSD-95 clusters in vivo. Using two-photon microscopy, we imaged PSD-95 tagged with GFP in layer 2/3 dendrites in the developing (postnatal day 10–21) barrel cortex. A subset of PSD-95 clusters was stable for days. Using two-photon photoactivation of PSD-95 tagged with photoactivatable GFP (paGFP), we measured the time over which PSD-95 molecules were retained in individual spines. Synaptic PSD-95 turned over rapidly (median retention times τr ~ 22–63 min from P10–P21) and exchanged with PSD-95 in neighboring spines by diffusion. PSDs therefore share a dynamic pool of PSD-95. Large PSDs in large spines captured more diffusing PSD-95 and also retained PSD-95 longer than small PSDs. Changes in the sizes of individual PSDs over days were associated with concomitant changes in PSD-95 retention times. Furthermore, retention times increased with developmental age (τr ~ 100 min at postnatal day 70) and decreased dramatically following sensory deprivation. Our data suggest that individual PSDs compete for PSD-95 and that the kinetic interactions between PSD molecules and PSDs are tuned to regulate PSD size. Rapid Redistribution of Synaptic PSD-95 in the Neocortex In Vivo Noah Gray Robby Weimer Ingrid Bureau Karel Svoboda doi:10.1371/journal.pbio.0040370 PLoS Biology, Vol. 4, No. 11. (1 November 2006), e370. 2006-11-07T20:04:32-00:00 2006 PLoS Biology 4 11 e370 cortical_neurons dendritic_spines fluorescent_proteins live_cell_imaging photoactivation postsynaptic http://www.citeulike.org/user/lechristophe/article/525971 <i>Nature Cell Biology, Vol. 8, No. 3. (12 February 2006), pp. 227-237.</i><br /><br />PAR-3 (partitioning-defective gene 3) is essential for cell polarization in many contexts, including axon specification. However, polarity proteins have not been implicated in later steps of neuronal differentiation, such as dendritic spine morphogenesis. Here, we show that PAR-3 is necessary for normal spine development in primary hippocampal neurons. Depletion of PAR-3 causes the formation of multiple filopodia- and lamellipodia-like dendritic protrusions - a phenotype similar to neurons expressing activated Rac. PAR-3 regulates spine formation by binding the Rac guanine nucleotide-exchange factor (GEF) TIAM1, and spatially restricting it to dendritic spines. Thus, a balance of PAR-3 and TIAM1 is essential to modulate Rac-GTP levels and to allow spine morphogenesis. The polarity protein PAR-3 and TIAM1 cooperate in dendritic spine morphogenesis Huaye Zhang Ian Macara doi:10.1038/ncb1368 Nature Cell Biology, Vol. 8, No. 3. (12 February 2006), pp. 227-237. 2006-03-01T19:56:09-00:00 2006 Nature Cell Biology 1465-7392 8 3 227 237 Nature Publishing Group dendrites dendritic_spines somatodendritic synapse