201
|
Renner M, Specht CG, Triller A. Molecular dynamics of postsynaptic receptors and scaffold proteins. Curr Opin Neurobiol 2008; 18:532-40. [PMID: 18832033 DOI: 10.1016/j.conb.2008.09.009] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 09/12/2008] [Accepted: 09/15/2008] [Indexed: 11/17/2022]
Abstract
The activity of neurotransmitter receptors determines the strength of synaptic transmission. Therefore, the clustering of receptors at synapses is an important mechanism underlying synaptic plasticity. The dynamic exchange of receptors between synaptic and extrasynaptic membranes is dependent on their interaction with synaptic scaffold proteins. Here, we review the recent advances and emerging concepts related to the dynamics of synaptic proteins at inhibitory and excitatory synapses. These include the imaging techniques that enable the study of protein dynamics in cells, the differences and similarities of receptor dynamics at excitatory and inhibitory synapses, the relationship between the exchange of receptor and scaffold proteins, as well as the role of receptor fluxes in the modulation of synaptic strength.
Collapse
Affiliation(s)
- Marianne Renner
- Inserm U789, Biologie Cellulaire de la Synapse, ENS, Paris, France
| | | | | |
Collapse
|
202
|
Homeostatic regulation of synaptic GlyR numbers driven by lateral diffusion. Neuron 2008; 59:261-73. [PMID: 18667154 DOI: 10.1016/j.neuron.2008.05.030] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 02/26/2008] [Accepted: 05/29/2008] [Indexed: 11/24/2022]
Abstract
In the spinal cord, most inhibitory synapses have a mixed glycine-GABA phenotype. Using a pharmacological approach, we report an NMDAR activity-dependent regulation of the mobility of GlyRs but not GABA(A)Rs at inhibitory synapses in cultured rat spinal cord neurons. The NMDAR-induced decrease in GlyR lateral diffusion was correlated with an increase in receptor cluster number and glycinergic mIPSC amplitude. Changes in GlyR diffusion properties occurred rapidly and before the changes in the number of synaptic receptors. Regulation of synaptic GlyR content occurred without change in the amount of gephyrin. Moreover, NMDAR-dependent regulation of GlyR lateral diffusion required calcium influx and calcium release from stores. Therefore, excitation may increase GlyR levels at synapses by a calcium-mediated increase in postsynaptic GlyR trapping involving regulation of receptor-scaffold interactions. This provides a mechanism for a rapid homeostatic regulation of the inhibitory glycinergic component at mixed glycine-GABA synapses in response to increased NMDA excitatory transmission.
Collapse
|
203
|
Structural plasticity with preserved topology in the postsynaptic protein network. Proc Natl Acad Sci U S A 2008; 105:12587-92. [PMID: 18723686 DOI: 10.1073/pnas.0711669105] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The size, shape, and molecular arrangement of the postsynaptic density (PSD) determine the function of excitatory synapses in the brain. Here, we directly measured the internal dynamics of scaffold proteins within single living PSDs, focusing on the principal scaffold protein PSD-95. We found that individual PSDs undergo rapid, continuous changes in morphology driven by the actin cytoskeleton and regulated by synaptic activity. This structural plasticity is accompanied by rapid fluctuations in internal scaffold density over submicron distances. Using targeted photobleaching and photoactivation of PSD subregions, we show that PSD-95 is nearly immobile within the PSD, and PSD subdomains can be maintained over long periods. We propose a flexible matrix model of the PSD based on stable molecular positioning of PSD-95 scaffolds.
Collapse
|
204
|
Triller A, Choquet D. New Concepts in Synaptic Biology Derived from Single-Molecule Imaging. Neuron 2008; 59:359-74. [DOI: 10.1016/j.neuron.2008.06.022] [Citation(s) in RCA: 213] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 06/20/2008] [Accepted: 06/24/2008] [Indexed: 01/02/2023]
|
205
|
Hugel S, Abegg M, de Paola V, Caroni P, Gähwiler BH, McKinney RA. Dendritic spine morphology determines membrane-associated protein exchange between dendritic shafts and spine heads. ACTA ACUST UNITED AC 2008; 19:697-702. [PMID: 18653666 DOI: 10.1093/cercor/bhn118] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The purpose of this study was to examine whether variability in the shape of dendritic spines affects protein movement within the plasma membrane. Using a combination of confocal microscopy and the fluorescence loss in photobleaching technique in living hippocampal CA1 pyramidal neurons expressing membrane-linked GFP, we observed a clear correlation between spine shape parameters and the diffusion and compartmentalization of membrane-associated proteins. The kinetics of membrane-linked GFP exchange between the dendritic shaft and the spine head compartment were slower in dendritic spines with long necks and/or large heads than in those with short necks and/or small heads. Furthermore, when the spine area was reduced by eliciting epileptiform activity, the kinetics of protein exchange between the spine compartments exhibited a concomitant decrease. As synaptic plasticity is considered to involve the dynamic flux by lateral diffusion of membrane-bound proteins into and out of the synapse, our data suggest that spine shape represents an important parameter in the susceptibility of synapses to undergo plastic change.
Collapse
Affiliation(s)
- Sylvain Hugel
- Brain Research Institute, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | | | | | | | | | | |
Collapse
|
206
|
Subunit-specific surface mobility of differentially labeled AMPA receptor subunits. Eur J Cell Biol 2008; 87:763-78. [PMID: 18547676 DOI: 10.1016/j.ejcb.2008.02.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 02/27/2008] [Accepted: 02/28/2008] [Indexed: 11/21/2022] Open
Abstract
Lateral mobility of AMPA-type glutamate receptors as well as their trafficking between plasma membrane and intracellular compartments are major mechanisms for the regulation of synaptic plasticity. Here we applied a recently established labeling technique in combination with lentiviral expression in hippocampal neurons to label individual ACP-tagged AMPA receptor subunits specifically at the surface of neurons. We show that this technique allows the differential labeling of two receptor subunits on the same cell. Moreover, these subunits are integrated into heteromeric receptors together with endogenous subunits, and these labeled receptors are targeted to active synapses. Sequential labeling experiments indicate that there is basal surface insertion of GluR1, GluR2 and GluR3, and that this insertion is strongly increased following potassium depolarization. Moreover, we found that ACP-labeled GluR3 shows the highest surface mobility among GluR1, GluR2, and GluR3. In double-infected neurons the diffusion coefficient of labeled GluR2 at the surface of living neurons is significantly higher in GluR2/GluR3-infected neurons compared to GluR1/GluR2-infected neurons suggesting a higher mobility of GluR2/3 receptors compared to GluR1/2 receptors. These results indicate that surface mobility is regulated by different subunit compositions of AMPA receptors.
Collapse
|
207
|
Huang ZJ, Scheiffele P. GABA and neuroligin signaling: linking synaptic activity and adhesion in inhibitory synapse development. Curr Opin Neurobiol 2008; 18:77-83. [PMID: 18513949 DOI: 10.1016/j.conb.2008.05.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 05/05/2008] [Accepted: 05/08/2008] [Indexed: 10/22/2022]
Abstract
GABA-mediated synaptic inhibition is crucial in neural circuit operations. In mammalian brains, the development of inhibitory synapses and innervation patterns is often a prolonged postnatal process, regulated by neural activity. Emerging evidence indicates that gamma-aminobutyric acid (GABA) acts beyond inhibitory transmission and regulates inhibitory synapse development. Indeed, GABA(A) receptors not only function as chloride channels that regulate membrane voltage and conductance but also play structural roles in synapse maturation and stabilization. The link from GABA(A) receptors to postsynaptic and presynaptic adhesion is probably mediated, partly by neuroligin-reurexin interactions, which are potent in promoting GABAergic synapse formation. Therefore, similar to glutamate signaling at excitatory synapse, GABA signaling may coordinate maturation of presynaptic and postsynaptic sites at inhibitory synapses. Defining the many steps from GABA signaling to receptor trafficking/stability and neuroligin function will provide further mechanistic insights into activity-dependent development and possibly plasticity of inhibitory synapses.
Collapse
Affiliation(s)
- Z Josh Huang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA.
| | | |
Collapse
|
208
|
Sokolova IV, Mody I. Silencing-induced metaplasticity in hippocampal cultured neurons. J Neurophysiol 2008; 100:690-7. [PMID: 18509070 DOI: 10.1152/jn.90378.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Silencing-induced homeostatic plasticity is usually expressed as a change in the amplitude or the frequency of miniature postsynaptic currents. Here we report that, prolonged (approximately 24 h) silencing of mature (20-22 days in vitro) cultured hippocampal neurons using the voltage-gated sodium channel blocker tetrodotoxin (TTX) produced no effects on the amplitude or frequency of the miniature excitatory postsynaptic currents (mEPSCs). However, the silencing changed the intrinsic membrane properties of the neurons, resulting in an increased excitability and rate of action potentials firing upon TTX washout. Allowing neurons to recover in TTX-free recording solution for a short period of time after the silencing resulted in potentiation of mEPSC amplitudes. This form of activity-dependent potentiation is different from classical long-term potentiation, as similar potentiation was not seen in nonsilenced neurons treated with bicuculline to raise their spiking activity to the same level displayed by the silenced neurons during TTX washout. Also, the potentiation of mEPSC amplitudes after the recovery period was not affected by the N-methyl-d-aspartate receptor blocker d-2-amino-5-phosponopentanoic acid or by the calcium/calmodulin-dependent kinase II (CaMKII) inhibitor KN-62 but was abolished by the L-type calcium channel blocker nifedipine. We thus conclude that the potentiation of mEPSC amplitudes following brief recovery of spiking activity in chronically silenced neurons represents a novel form of metaplasticity that differs from the conventional models of homeostatic synaptic plasticity.
Collapse
Affiliation(s)
- Irina V Sokolova
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, California 90095-7335, USA
| | | |
Collapse
|
209
|
Newpher TM, Ehlers MD. Glutamate receptor dynamics in dendritic microdomains. Neuron 2008; 58:472-97. [PMID: 18498731 PMCID: PMC2572138 DOI: 10.1016/j.neuron.2008.04.030] [Citation(s) in RCA: 278] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 04/28/2008] [Accepted: 04/30/2008] [Indexed: 01/08/2023]
Abstract
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.
Collapse
Affiliation(s)
- Thomas M. Newpher
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Michael D. Ehlers
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
| |
Collapse
|
210
|
Schmid A, Hallermann S, Kittel RJ, Khorramshahi O, Frölich AMJ, Quentin C, Rasse TM, Mertel S, Heckmann M, Sigrist SJ. Activity-dependent site-specific changes of glutamate receptor composition in vivo. Nat Neurosci 2008; 11:659-66. [PMID: 18469810 DOI: 10.1038/nn.2122] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 04/14/2008] [Indexed: 02/08/2023]
Abstract
The subunit composition of postsynaptic non-NMDA-type glutamate receptors (GluRs) determines the function and trafficking of the receptor. Changes in GluR composition have been implicated in the homeostasis of neuronal excitability and synaptic plasticity underlying learning. Here, we imaged GluRs in vivo during the formation of new postsynaptic densities (PSDs) at Drosophila neuromuscular junctions coexpressing GluRIIA and GluRIIB subunits. GluR composition was independently regulated at directly neighboring PSDs on a submicron scale. Immature PSDs typically had large amounts of GluRIIA and small amounts of GluRIIB. During subsequent PSD maturation, however, the GluRIIA/GluRIIB composition changed and became more balanced. Reducing presynaptic glutamate release increased GluRIIA, but decreased GluRIIB incorporation. Moreover, the maturation of GluR composition correlated in a site-specific manner with the level of Bruchpilot, an active zone protein that is essential for mature glutamate release. Thus, we show that an activity-dependent, site-specific control of GluR composition can contribute to match pre- and postsynaptic assembly.
Collapse
Affiliation(s)
- Andreas Schmid
- Institute for Clinical Neurobiology, Medical Faculty, University of Würzburg, Zinklesweg 10, 97080 Würzburg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
211
|
Choquet D, Lounis B. [Surface mobility of postsynaptic AMPARs tunes synaptic transmission]. Med Sci (Paris) 2008; 24:548-50. [PMID: 18466736 DOI: 10.1051/medsci/2008245548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Daniel Choquet
- UMR CNRS 5091, Université de Bordeaux, 33077, Bordeaux, France.
| | | |
Collapse
|
212
|
Ibata K, Sun Q, Turrigiano GG. Rapid synaptic scaling induced by changes in postsynaptic firing. Neuron 2008; 57:819-26. [PMID: 18367083 DOI: 10.1016/j.neuron.2008.02.031] [Citation(s) in RCA: 318] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2006] [Revised: 04/27/2007] [Accepted: 02/29/2008] [Indexed: 12/17/2022]
Abstract
Homeostatic synaptic scaling adjusts a neuron's excitatory synaptic strengths up or down to compensate for perturbations in activity. Little is known about the molecular pathway(s) involved, nor is it clear which aspect of "activity"-local synaptic signaling, postsynaptic firing, or large-scale changes in network activity-is required to induce synaptic scaling. Here, we selectively block either postsynaptic firing in individual neurons or a fraction of presynaptic inputs, while optically monitoring changes in synaptic strength. We find that synaptic scaling is rapidly induced by block of postsynaptic firing, but not by local synaptic blockade, and is mediated through a drop in somatic calcium influx, reduced activation of CaMKIV, and an increase in transcription. Cortical neurons thus homeostatically adjust synaptic strengths in response to changes in their own firing rate, a mechanism with the computational advantage of efficiently normalizing synaptic strengths without interfering with synapse-specific mechanisms of information storage.
Collapse
Affiliation(s)
- Keiji Ibata
- Department of Biology and Center for Behavioral Genomics, Brandeis University, Waltham, MA 02454, USA
| | | | | |
Collapse
|
213
|
Abstract
Lateral diffusion of glutamate receptors was proposed as a mechanism for regulating receptor numbers at synapses and affecting synaptic functions, especially the efficiency of synaptic transmission. However, a direct link between receptor lateral diffusion and change in synaptic function has not yet been established. In the present study, we demonstrated NMDA receptor (NMDAR) lateral diffusion in CA1 neurons in hippocampal slices by detecting considerable recovery of spontaneous or evoked EPSCs from the block of (+)-MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate], an irreversible NMDAR open-channel blocker. We observed changes on both the number and the composition of synaptic NMDAR on recovery. More importantly, after the recovery, long-term potentiation (LTP)-producing protocol induced only LTD (long-term depression) instead of LTP. In contrast, a complete recovery from competitive NMDAR blocker D,L-AP-5 was observed without subsequent changes on synaptic plasticity. Our data suggest a revised model of NMDAR trafficking wherein extrasynaptic NMDARs, mostly NR1/NR2B receptors, move laterally into synaptic sites, resulting in altered rule of synaptic modification. Thus, CA1 synapses exhibit a novel form of metaplasticity in which the direction of synaptic modification can be reverted through subtype-specific lateral diffusion of NMDA receptors.
Collapse
|
214
|
Heine M, Groc L, Frischknecht R, Béïque JC, Lounis B, Rumbaugh G, Huganir RL, Cognet L, Choquet D. Surface mobility of postsynaptic AMPARs tunes synaptic transmission. Science 2008; 320:201-5. [PMID: 18403705 PMCID: PMC2715948 DOI: 10.1126/science.1152089] [Citation(s) in RCA: 362] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
AMPA glutamate receptors (AMPARs) mediate fast excitatory synaptic transmission. Upon fast consecutive synaptic stimulation, transmission can be depressed. Recuperation from fast synaptic depression has been attributed solely to recovery of transmitter release and/or AMPAR desensitization. We show that AMPAR lateral diffusion, observed in both intact hippocampi and cultured neurons, allows fast exchange of desensitized receptors with naïve functional ones within or near the postsynaptic density. Recovery from depression in the tens of millisecond time range can be explained in part by this fast receptor exchange. Preventing AMPAR surface movements through cross-linking, endogenous clustering, or calcium rise all slow recovery from depression. Physiological regulation of postsynaptic receptor mobility affects the fidelity of synaptic transmission by shaping the frequency dependence of synaptic responses.
Collapse
Affiliation(s)
- Martin Heine
- CNRS, UMR 5091, Université Bordeaux, Bordeaux, France
| | | | | | | | | | | | | | | | | |
Collapse
|
215
|
Rapid tumor necrosis factor alpha-induced exocytosis of glutamate receptor 2-lacking AMPA receptors to extrasynaptic plasma membrane potentiates excitotoxicity. J Neurosci 2008; 28:2119-30. [PMID: 18305246 DOI: 10.1523/jneurosci.5159-07.2008] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The postinjury inflammatory response in the CNS leads to neuronal excitotoxicity. Our previous studies show that a major component of this response, the inflammatory cytokine tumor necrosis factor alpha (TNFalpha), causes a rapid increase in AMPA glutamate receptors (AMPARs) on the plasma membrane of cultured hippocampal neurons. This may potentiate neuron death through an increased vulnerability to AMPAR-dependent excitotoxic stress. Here, we test this hypothesis with an in vitro lactose dehydrogenase death assay and examine in detail the AMPAR surface delivery time course, receptor subtype, and synaptic and extrasynaptic distribution after TNFalpha exposure. These data demonstrate that surface levels of glutamate receptor 2 (GluR2)-lacking Ca2+-permeable AMPARs peak at 15 min after TNFalpha treatment, and the majority are directed to extrasynaptic sites. TNFalpha also induces an increase in GluR2-containing surface AMPARs but with a slower time course. We propose that this activity contributes to excitotoxic neuron death because TNFalpha potentiation of kainate excitotoxicity is blocked by a Ca2+-permeable AMPAR antagonist [NASPM (1-naphthyl acetyl spermine)] and a specific phosphoinositide 3 kinase (PI3 kinase) inhibitor (LY294,002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one]) previously shown to block the TNFalpha-induced increase in AMPAR surface delivery. This information forms the basis for future in vivo studies examining AMPAR-dependent potentiation of excitotoxic neuron death and dysfunction caused by TNFalpha after acute injury and during neurodegenerative or neuropsychiatric disorders.
Collapse
|
216
|
Eichler SA, Meier JC. E-I balance and human diseases - from molecules to networking. Front Mol Neurosci 2008; 1:2. [PMID: 18946535 PMCID: PMC2526001 DOI: 10.3389/neuro.02.002.2008] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Accepted: 01/30/2008] [Indexed: 11/18/2022] Open
Abstract
Information transfer in the brain requires a homeostatic control of neuronal excitability. Therefore, a functional balance between excitatory and inhibitory systems is established during development. This review contains recent information about the molecular mechanisms orchestrating the establishment and maintenance of this excitation-inhibition (E-I) balance, and it reviews examples of deregulation of inhibitory and excitatory systems at a molecular, network and disease level of investigation.
Collapse
Affiliation(s)
- Sabrina A Eichler
- RNA Editing and Hyperexcitability Disorders Helmholtz Group, Max Delbrück Center for Molecular Medicine Berlin, Germany
| | | |
Collapse
|
217
|
Hirling H. Endosomal trafficking of AMPA-type glutamate receptors. Neuroscience 2008; 158:36-44. [PMID: 18406063 DOI: 10.1016/j.neuroscience.2008.02.057] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 02/05/2008] [Accepted: 02/22/2008] [Indexed: 10/22/2022]
Abstract
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.
Collapse
Affiliation(s)
- H Hirling
- Brain Mind Institute, Faculté des Sciences de la Vie, Ecole Polytechnique Fédérale de Lausanne EPFL, 1015 Lausanne, Switzerland.
| |
Collapse
|
218
|
Hou Q, Huang Y, Amato S, Snyder SH, Huganir RL, Man HY. Regulation of AMPA receptor localization in lipid rafts. Mol Cell Neurosci 2008; 38:213-23. [PMID: 18411055 DOI: 10.1016/j.mcn.2008.02.010] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2007] [Revised: 01/09/2008] [Accepted: 02/20/2008] [Indexed: 02/01/2023] Open
Abstract
Lipid rafts are special microdomains enriched in cholesterol, sphingolipids and certain proteins, and play important roles in a variety of cellular functions including signal transduction and protein trafficking. We report that in cultured cortical and hippocampal neurons the distribution of lipid rafts is development-dependent. Lipid rafts in mature neurons exist on the entire cell-surface and display a high degree of mobility. AMPA receptors co-localize and associate with lipid rafts in the plasma membrane. The association of AMPARs with rafts is under regulation; through the NOS-NO pathway, NMDA receptor activity increases AMPAR localization in rafts. During membrane targeting, AMPARs insert into or at close proximity of the surface raft domains. Perturbation of lipid rafts dramatically suppresses AMPA receptor exocytosis, resulting in significant reduction in AMPAR cell-surface expression.
Collapse
Affiliation(s)
- Qingming Hou
- Department of Biology, Boston University, Boston, MA 02215, USA
| | | | | | | | | | | |
Collapse
|
219
|
Rosenberg MM, Yang F, Giovanni M, Mohn JL, Temburni MK, Jacob MH. Adenomatous polyposis coli plays a key role, in vivo, in coordinating assembly of the neuronal nicotinic postsynaptic complex. Mol Cell Neurosci 2008; 38:138-52. [PMID: 18407517 DOI: 10.1016/j.mcn.2008.02.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Revised: 01/30/2008] [Accepted: 02/10/2008] [Indexed: 11/27/2022] Open
Abstract
The neuronal nicotinic synapse plays a central role in normal cognitive and autonomic function. Molecular mechanisms that direct the assembly of this synapse remain poorly defined, however. We show here that adenomatous polyposis coli (APC) organizes a multi-molecular complex that is essential for targeting alpha3(*)nAChRs to synapses. APC interaction with microtubule plus-end binding protein EB1 is required for alpha3(*)nAChR surface membrane insertion and stabilization. APC brings together EB1, the key cytoskeletal regulators macrophin and IQGAP1, and 14-3-3 adapter protein at nicotinic synapses. 14-3-3, in turn, links the alpha3-subunit to APC. This multi-molecular APC complex stabilizes the local microtubule and F-actin cytoskeleton and links postsynaptic components to the cytoskeleton--essential functions for controlling the molecular composition and stability of synapses. This work identifies macrophin, IQGAP1 and 14-3-3 as novel nicotinic synapse components and defines a new role for APC as an in vivo coordinator of nicotinic postsynaptic assembly in vertebrate neurons.
Collapse
Affiliation(s)
- Madelaine M Rosenberg
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA
| | | | | | | | | | | |
Collapse
|
220
|
Jaskolski F, Henley JM. Synaptic receptor trafficking: the lateral point of view. Neuroscience 2008; 158:19-24. [PMID: 18455319 DOI: 10.1016/j.neuroscience.2008.01.075] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 01/15/2008] [Accepted: 01/17/2008] [Indexed: 10/22/2022]
Abstract
Activity dependent modification of receptors in the post-synaptic density is a key determinant in regulating the strength of synaptic transmission during development and plasticity. A major mechanism for this recruitment and removal of postsynaptic proteins is the lateral diffusion in the plane of the plasma membrane. Therefore, the processes that regulate this lateral mobility are of fundamental importance. In recent years significant progress has been achieved using optical approaches such as single particle tracking (SPT) and fluorescence recovery after photobleach (FRAP). Here, we provide an overview of the principles and methodology of these techniques and highlight the contributions they have made to current understanding of protein mobility in the plasma membrane.
Collapse
Affiliation(s)
- F Jaskolski
- MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, Department of Anatomy, University Walk, Bristol, BS8 1TD, UK
| | | |
Collapse
|
221
|
Yao WD, Spealman RD, Zhang J. Dopaminergic signaling in dendritic spines. Biochem Pharmacol 2008; 75:2055-69. [PMID: 18353279 DOI: 10.1016/j.bcp.2008.01.018] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 01/19/2008] [Accepted: 01/29/2008] [Indexed: 01/07/2023]
Abstract
Dopamine regulates movement, motivation, reward, and learning and is implicated in numerous neuropsychiatric and neurological disorders. The action of dopamine is mediated by a family of seven-transmembrane G protein-coupled receptors encoded by at least five dopamine receptor genes (D1, D2, D3, D4, and D5), some of which are major molecular targets for diverse neuropsychiatric medications. Dopamine receptors are present throughout the soma and dendrites of the neuron, but accumulating ultrastructural and biochemical evidence indicates that they are concentrated in dendritic spines, where most of the glutamatergic synapses are established. By modulating local channels, receptors, and signaling modules in spines, this unique population of postsynaptic receptors is strategically positioned to control the excitability and synaptic properties of spines and mediate both the tonic and phasic aspects of dopaminergic signaling with remarkable precision and versatility. The molecular mechanisms that underlie the trafficking, targeting, anchorage, and signaling of dopamine receptors in spines are, however, largely unknown. The present commentary focuses on this important subpopulation of postsynaptic dopamine receptors with emphases on recent molecular, biochemical, pharmacological, ultrastructural, and physiological studies that provide new insights about their regulatory mechanisms and unique roles in dopamine signaling.
Collapse
Affiliation(s)
- Wei-Dong Yao
- Harvard Medical School, New England Primate Research Center, Southborough, MA 01772, United States.
| | | | | |
Collapse
|
222
|
Homeostatic regulation of AMPA receptor expression at single hippocampal synapses. Proc Natl Acad Sci U S A 2008; 105:775-80. [PMID: 18174334 DOI: 10.1073/pnas.0706447105] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Homeostatic synaptic response is an important measure in confining neuronal activity within a narrow physiological range. Whether or not homeostatic plasticity demonstrates synapse specificity, a key feature characteristic of Hebbian-type plasticity, is largely unknown. Here, we report that in cultured hippocampal neurons, alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid subtype glutamate receptor (AMPAR) accumulation is increased selectively in chronically inhibited single synapses, whereas the neighboring normal synapses remain unaffected. This synapse-specific homeostatic regulation depends on the disparity of synaptic activity and is mediated by GluR2-lacking AMPARs and PI3-kinase signaling. These results demonstrate the existence of synaptic specificity and the crucial role of AMPAR-gated calcium in homeostatic plasticity in central neurons.
Collapse
|
223
|
Lasiecka ZM, Yap CC, Vakulenko M, Winckler B. Chapter 7 Compartmentalizing the Neuronal Plasma Membrane. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 272:303-89. [DOI: 10.1016/s1937-6448(08)01607-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
224
|
Surface trafficking of neurotransmitter receptor: comparison between single-molecule/quantum dot strategies. J Neurosci 2007; 27:12433-7. [PMID: 18003820 DOI: 10.1523/jneurosci.3349-07.2007] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
225
|
Real-time imaging of discrete exocytic events mediating surface delivery of AMPA receptors. J Neurosci 2007; 27:11112-21. [PMID: 17928453 DOI: 10.1523/jneurosci.2465-07.2007] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We directly resolved discrete exocytic fusion events mediating insertion of AMPA-type glutamate receptors (AMPARs) to the somatodendritic surface of rat hippocampal pyramidal neurons, in slice and dissociated cultures, using protein tagging with a pH-sensitive GFP (green fluorescent protein) variant and rapid (10 frames/s) fluorescence microscopy. AMPAR-containing exocytic events occurred under basal culture conditions in both the cell body and dendrites; potentiating chemical stimuli produced an NMDA receptor-dependent increase in the frequency of individual exocytic events. The number of AMPARs inserted per exocytic event, estimated using single-molecule analysis, was quite uniform but individual events differed significantly in kinetic properties affecting the subsequent surface distribution of receptors. "Transient" events, from which AMPARs dispersed laterally immediately after surface insertion, generated a pronounced but short-lived (dissipating within approximately 1 s) increase in surface AMPAR fluorescence extending locally (2-5 microm) from the site of exocytosis. "Persistent" events, from which inserted AMPARs dispersed slowly (typically over 5-10 s), affected local surface receptor concentration to a much smaller degree. Both modes of exocytic insertion occurred throughout the dendritic shaft, but remarkably, neither mode of insertion was observed directly into synaptic spines. AMPARs entered spines preferentially from transient events occurring in the adjoining dendritic shaft, driven apparently by mass action and short-range lateral diffusion, and locally delivered AMPARs remained mostly in the mobile fraction. These results suggest a highly dynamic mechanism for both constitutive and activity-dependent surface delivery of AMPARs, mediated by kinetically distinct exocytic modes that differ in propensity to drive lateral entry of receptors to nearby synapses.
Collapse
|
226
|
Lu J, Helton TD, Blanpied TA, Rácz B, Newpher TM, Weinberg RJ, Ehlers MD. Postsynaptic positioning of endocytic zones and AMPA receptor cycling by physical coupling of dynamin-3 to Homer. Neuron 2007; 55:874-89. [PMID: 17880892 PMCID: PMC2597538 DOI: 10.1016/j.neuron.2007.06.041] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Revised: 06/08/2007] [Accepted: 07/31/2007] [Indexed: 02/07/2023]
Abstract
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.
Collapse
Affiliation(s)
- Jiuyi Lu
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Thomas D. Helton
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Thomas A. Blanpied
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Bence Rácz
- Department of Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC, 27599, USA
| | - Thomas M. Newpher
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Richard J. Weinberg
- Department of Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC, 27599, USA
- Neuroscience Center, University of North Carolina School of Medicine, Chapel Hill, NC, 27599, USA
| | - Michael D. Ehlers
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
- Corresponding Author: Michael D. Ehlers, M.D., Ph.D., Howard Hughes Medical Institute, Department of Neurobiology, Duke University Medical Center, Box 3209, Durham, NC 27710, USA, Tel: (919)684-1828, FAX (919)668-0631, e-mail:
| |
Collapse
|
227
|
Quantum dots provide an optical signal specific to full collapse fusion of synaptic vesicles. Proc Natl Acad Sci U S A 2007; 104:17843-8. [PMID: 17968015 DOI: 10.1073/pnas.0706906104] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synaptic vesicles are responsible for releasing neurotransmitters and are thus essential to brain function. The classical mode of vesicle recycling includes full collapse of the vesicle into the plasma membrane and clathrin-mediated regeneration of a new vesicle. In contrast, a nonclassical mode known as "kiss-and-run" features fusion by a transient fusion pore without complete loss of vesicle identity and offers possible advantages for increasing the throughput of neurotransmission. Studies of vesicular traffic have benefited greatly from fluorescent probes like FM dyes and synaptopHluorin. However, intrinsic properties of these probes limit their ability to provide a simple and precise distinction between classical and nonclassical modes. Here we report a novel optical probe specific to full collapse fusion, capitalizing on the size and superior photo-properties of photoluminescent quantum dots (Qdots). Qdots with exposed carboxyl groups were readily taken up by synaptic vesicles in an activity-, Ca(2+)-, and clathrin-dependent manner. Electron microscopy showed that Qdots were harbored within individual vesicles in a 1:1 ratio. The release of Qdots was activity- and Ca(2+)-dependent, similar to FM dyes. As artificial cargo, approximately 15 nm in diameter, Qdots will not escape vesicles during kiss-and-run but only with full collapse fusion. Strikingly, Qdots unloaded with kinetics substantially slower than destaining of FM dye, indicating that full-collapse fusion contributed only a fraction of all fusion events. As a full-collapse-fusion-responsive reporter, Qdots will likely promote better understanding of vesicle recycling at small CNS nerve terminals.
Collapse
|