101
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Rabinowitch I, Segev I. The endurance and selectivity of spatial patterns of long-term potentiation/depression in dendrites under homeostatic synaptic plasticity. J Neurosci 2007; 26:13474-84. [PMID: 17192430 PMCID: PMC6674716 DOI: 10.1523/jneurosci.4333-06.2006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We investigated analytically and numerically the interplay between two opposing forms of synaptic plasticity: positive-feedback, long-term potentiation/depression (LTP/LTD), and negative-feedback, homeostatic synaptic plasticity (HSP). A detailed model of a CA1 pyramidal neuron, with numerous HSP-modifiable dendritic synapses, demonstrates that HSP may have an important role in selecting which spatial patterns of LTP/LTD are to last. Several measures are developed for predicting the net residual potentiation/depression after HSP from the initial spatial pattern of LTP/LTD. Under a local dendritic HSP mechanism, sparse patterns of LTP/LTD, which we show, using information theoretical tools, to have a significant impact on the output of the postsynaptic neuron, will persist. In contrast, spatially clustered patterns with a smaller impact on the output will diminish. A global somatic HSP mechanism, conversely, will favor distally occurring LTP/LTDs over proximal ones. Despite the negative-feedback nature of HSP, under both local and global HSP, numerous synaptic potentiations/depressions can persist. These experimentally testable results imply that HSP could be significantly involved in shaping the spatial distribution of synaptic weights in the dendrites and not just normalizing it, as is currently believed.
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Affiliation(s)
- Ithai Rabinowitch
- Interdisciplinary Center for Neural Computation and the Department of Neurobiology, Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond Safra Campus, Givat Ram, Jerusalem, 91904, Israel
| | - Idan Segev
- Interdisciplinary Center for Neural Computation and the Department of Neurobiology, Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond Safra Campus, Givat Ram, Jerusalem, 91904, Israel
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102
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Gerkin RC, Lau PM, Nauen DW, Wang YT, Bi GQ. Modular competition driven by NMDA receptor subtypes in spike-timing-dependent plasticity. J Neurophysiol 2007; 97:2851-62. [PMID: 17267756 DOI: 10.1152/jn.00860.2006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
N-methyl-d-aspartate receptors (NMDARs) play a critical role in transducing neuronal activity patterns into changes in synaptic strength. However, how they mediate this transduction in response to physiological stimuli has remained elusive. In particular, it has been debated whether different NMDAR subtypes play opposing signaling roles in synaptic plasticity. Using perforated patch-clamp recordings from pairs of synaptically connected glutamatergic neurons in dissociated hippocampal culture, we found that spike-timing-dependent potentiation induced by pairing pre- and postsynaptic spikes required the activation of a fast component of NMDAR current that is likely to be mediated by NR2A-containing NMDARs (NR2A-NRs). In contrast, spike-timing-dependent depression required a slow component of NMDAR current carried by NR2B-containing NMDARs (NR2B-NRs). CV analysis showed that the locus of this depression was primarily presynaptic in pairs of cells making strong synaptic connections, whereas weaker synapses showed no clear preference for pre- or postsynaptic expression. This depression was not significantly reduced by antagonism of the CB1 receptor, in contrast to spike-timing-dependent depression in the neocortex that requires presynaptic CB1 signaling. With blockade of NR2B-NRs, spike triplets that contained both potentiating and depressing spike-timing components induced net potentiation. However, when the putative NR2A-NR population is inhibited, these spike triplets resulted in either depression or no net change, depending on the temporal order of the spike-timing components. These results imply a dynamic competition between signaling modules that can be biased by differentially antagonizing NMDAR subtypes during the induction of spike-timing-dependent plasticity. Using a simple model, we show that such a modular competition recapitulates our observations.
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Affiliation(s)
- Richard C Gerkin
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
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103
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Matsuzaki M. Factors critical for the plasticity of dendritic spines and memory storage. Neurosci Res 2007; 57:1-9. [PMID: 17070951 DOI: 10.1016/j.neures.2006.09.017] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 09/16/2006] [Accepted: 09/25/2006] [Indexed: 11/17/2022]
Abstract
The structure of dendritic spines is highly plastic and responds to synaptic activity, including activity patterns that induce long-term potentiation (LTP) and depression (LTD). Induction of LTP causes enlargement of spine heads, while LTD causes spine head shrinkage. In addition, spine structure is well associated with synaptic weight and the extent of synaptic plasticity, such that structural changes of the spine may represent forms of memory storage. While the correlation between structural and functional plasticity appears to be simple, the underlying mechanisms of spine plasticity are intricate. Spine plasticity requires multiple molecular interactions, and is affected by the surrounding environment and by cellular metabolic state. Here, I synthesize the latest progress in this field by defining six determinants of spine plasticity, and discuss the role of each factor in memory storage.
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Affiliation(s)
- Masanori Matsuzaki
- Division of Biophysics, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
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104
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Lauri SE, Palmer M, Segerstrale M, Vesikansa A, Taira T, Collingridge GL. Presynaptic mechanisms involved in the expression of STP and LTP at CA1 synapses in the hippocampus. Neuropharmacology 2007; 52:1-11. [PMID: 16919682 DOI: 10.1016/j.neuropharm.2006.06.017] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 06/22/2006] [Accepted: 06/23/2006] [Indexed: 11/28/2022]
Abstract
The study of long-term potentiation (LTP) has for many years been the centre of a raging debate as to whether the process is expressed by presynaptic or postsynaptic mechanisms. Here we present evidence that two forms of synaptic plasticity at CA3-CA1 synapses in the hippocampus are expressed by presynaptic changes. One form is short-term potentiation (STP) and the other a neonatal form of early-LTP (E-LTP). We review recent experimental data that suggests that this latter form of LTP involves an increase in the probability of neurotransmitter release (Pr). We describe how this is caused by the rapid down-regulation of a high affinity kainate receptor, which otherwise responds to ambient levels of l-glutamate by depressing Pr.
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Affiliation(s)
- Sari E Lauri
- Neuroscience Center and Department of Biological and Environmental Sciences, University of Helsinki, 00014 Helsinki, Finland
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105
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Sobczyk A, Svoboda K. Activity-Dependent Plasticity of the NMDA-Receptor Fractional Ca2+ Current. Neuron 2007; 53:17-24. [PMID: 17196527 DOI: 10.1016/j.neuron.2006.11.016] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 10/23/2006] [Accepted: 11/16/2006] [Indexed: 11/28/2022]
Abstract
Ca(2+) influx through NMDA receptors (NMDA-Rs) triggers synaptic plasticity, gene transcription, and cytotoxicity, but little is known about the regulation of NMDA-Rs themselves. We used two-photon glutamate uncaging to activate NMDA-Rs on individual dendritic spines in rat CA1 neurons while we measured NMDA-R currents at the soma and [Ca(2+)] changes in spines. Low-frequency uncaging trains induced Ca(2+)-dependent long-term depression of NMDA-R-mediated synaptic currents. Additionally, uncaging trains caused a reduction in the Ca(2+) accumulation per unit of NMDA-R current in spines due to a reduction in the fraction of the NMDA-R current carried by Ca(2+). Induction of depression of NMDA-R-mediated Ca(2+) influx required activation of NR2B-containing receptors. Receptors in single spines depressed rapidly in an all-or-none manner. These adaptive changes in NMDA-R function likely play a critical role in metaplasticity and in stabilizing activity levels in neuronal networks with Hebbian synapses.
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Affiliation(s)
- Aleksander Sobczyk
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
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106
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Zhang YP, Oertner TG. Optical induction of synaptic plasticity using a light-sensitive channel. Nat Methods 2006; 4:139-41. [PMID: 17195846 DOI: 10.1038/nmeth988] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Accepted: 11/01/2006] [Indexed: 11/08/2022]
Abstract
We have combined millisecond activation of channelrhodopsin-2 (ChR2), a light-gated ion channel, with two-photon calcium imaging to investigate active synaptic contacts in rat hippocampal slice cultures. Calcium influx was larger during light-induced action potentials than during action potentials induced by somatic current injection, leading to highly reproducible synaptic transmission. Pairing of light stimulation with postsynaptic depolarization induced long-term potentiation, making this technique ideal for genetic and pharmacological dissection of synaptic plasticity.
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Affiliation(s)
- Yan-Ping Zhang
- Friedrich Miescher Institute, Novartis Research Foundation, Maulbeerstr. 66, WRO-1066.4.04, CH-4058 Basel, Switzerland
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107
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Korkotian E, Segal M. Morphological constraints on calcium dependent glutamate receptor trafficking into individual dendritic spine. Cell Calcium 2006; 42:41-57. [PMID: 17187855 DOI: 10.1016/j.ceca.2006.11.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2006] [Revised: 11/14/2006] [Accepted: 11/16/2006] [Indexed: 11/28/2022]
Abstract
Glutamate receptor trafficking into dendritic spines is a pivotal step in synaptic plasticity, yet the relevance of plasticity-producing rise of [Ca2+]i and of spine morphology to subsequent delivery of glutamate receptors into dendritic spine heads are still not well understood. Following chemical induction of LTP, an increase in eGFP-GluR1 fluorescence in short but not long dendritic spines of cultured hippocampal neurons was found. Repeated flash photolysis of caged calcium, which produced a transient rise of [Ca2+]i inside spine heads caused a selective, actin and protein synthesis dependent increase of eGFP-GluR1 in these spines. Strikingly, GluR1 increase was correlated with the ability of a calcium transient generated in the spine head to diffuse into the parent dendrite, and inversely correlated with the length of the spine: short spines were more likely to raise GluR1 than long ones. These observations link, for the first time, calcium transients in dendritic spines with spine morphology and its ability to undergo synaptic plasticity.
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Affiliation(s)
- Eduard Korkotian
- Department of Neurobiology, The Weizmann Institute, Rehovot 76100, Israel
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108
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Béïque JC, Lin DT, Kang MG, Aizawa H, Takamiya K, Huganir RL. Synapse-specific regulation of AMPA receptor function by PSD-95. Proc Natl Acad Sci U S A 2006; 103:19535-40. [PMID: 17148601 PMCID: PMC1748260 DOI: 10.1073/pnas.0608492103] [Citation(s) in RCA: 284] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PSD-95 is a major protein found in virtually all mature excitatory glutamatergic synapses in the brain. Here, we have addressed the role of PSD-95 in controlling glutamatergic synapse function by generating and characterizing a PSD-95 KO mouse. We found that the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)subtype of glutamate receptor (AMPAR)-mediated synaptic transmission was reduced in these mice. Two-photon (2P) uncaging of MNI-glutamate onto individual spines suggested that the decrease in AMPAR function in the PSD-95 KO mouse stems from an increase in the proportion of "silent" synapses i.e., synapses containing N-methyl-d-aspartate (NMDA) receptors (NMDARs) but no AMPARs. Unexpectedly, the silent synapses in the KO mouse were located onto morphologically mature spines. We also observed that a significant population of synapses appeared unaffected by PSD-95 gene deletion, suggesting that the functional role of PSD-95 displays synapse-specificity. In addition, we report that the decay of NMDAR-mediated current was slower in KO mice: The contribution of NR2B subunit containing receptors to the NMDAR-mediated synaptic current was greater in KO mice. The greater occurrence of silent synapses might be related to the greater magnitude of potentiation after long-term potentiation induction observed in these mice. Together, these results suggest a synapse-specific role for PSD-95 in controlling synaptic function that is independent of spine morphology.
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Affiliation(s)
- Jean-Claude Béïque
- Department of Neuroscience, Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, 725 North Wolfe Street, Baltimore, MD 21205
| | - Da-Ting Lin
- Department of Neuroscience, Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, 725 North Wolfe Street, Baltimore, MD 21205
| | - Myoung-Goo Kang
- Department of Neuroscience, Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, 725 North Wolfe Street, Baltimore, MD 21205
| | - Hiro Aizawa
- Department of Neuroscience, Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, 725 North Wolfe Street, Baltimore, MD 21205
| | - Kogo Takamiya
- Department of Neuroscience, Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, 725 North Wolfe Street, Baltimore, MD 21205
| | - Richard L. Huganir
- Department of Neuroscience, Johns Hopkins University School of Medicine and Howard Hughes Medical Institute, 725 North Wolfe Street, Baltimore, MD 21205
- *To whom correspondence should be addressed. E-mail:
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109
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Lai C, Xie C, McCormack SG, Chiang HC, Michalak MK, Lin X, Chandran J, Shim H, Shimoji M, Cookson MR, Huganir RL, Rothstein JD, Price DL, Wong PC, Martin LJ, Zhu JJ, Cai H. Amyotrophic lateral sclerosis 2-deficiency leads to neuronal degeneration in amyotrophic lateral sclerosis through altered AMPA receptor trafficking. J Neurosci 2006; 26:11798-806. [PMID: 17093100 PMCID: PMC2556290 DOI: 10.1523/jneurosci.2084-06.2006] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron disease is caused by a selective loss of motor neurons. One form of juvenile onset autosomal recessive ALS (ALS2) has been linked to the loss of function of the ALS2 gene. The pathogenic mechanism of ALS2-deficiency, however, remains unclear. To further understand the function of alsin that is encoded by the full-length ALS2 gene, we screened proteins interacting with alsin. Here, we report that alsin interacted with glutamate receptor interacting protein 1 (GRIP1) both in vitro and in vivo, and colocalized with GRIP1 in neurons. In support of the physiological interaction between alsin and GRIP1, the subcellular distribution of GRIP1 was altered in ALS2(-/-) spinal motor neurons, which correlates with a significant reduction of AMPA-type glutamate receptor subunit 2 (GluR2) at the synaptic/cell surface of ALS2(-/-) neurons. The decrease of calcium-impermeable GluR2-containing AMPA receptors at the cell/synaptic surface rendered ALS2(-/-) neurons more susceptible to glutamate receptor-mediated neurotoxicity. Our findings reveal a novel function of alsin in AMPA receptor trafficking and provide a novel pathogenic link between ALS2-deficiency and motor neuron degeneration, suggesting a protective role of alsin in maintaining the survival of motor neurons.
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Affiliation(s)
- Chen Lai
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Chengsong Xie
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Stefanie G. McCormack
- Department of Pharmacology and Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | | | - Marta K. Michalak
- Department of Pharmacology and Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, Virginia 22908
- Biotechnology Graduate Program, Technical University of Łódź, 90-924 Łódź, Poland
| | - Xian Lin
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Jayanth Chandran
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Hoon Shim
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Mika Shimoji
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Mark R. Cookson
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
| | - Richard L. Huganir
- Neuroscience, and
- Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | | | | | | | | | - J. Julius Zhu
- Department of Pharmacology and Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, Virginia 22908
| | - Huaibin Cai
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892
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110
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Sapoznik S, Ivenshitz M, Segal M. Age-dependent glutamate induction of synaptic plasticity in cultured hippocampal neurons. Learn Mem 2006; 13:719-27. [PMID: 17101873 PMCID: PMC1783625 DOI: 10.1101/lm.351706] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A common denominator for the induction of morphological and functional plasticity in cultured hippocampal neurons involves the activation of excitatory synapses. We now demonstrate massive morphological plasticity in mature cultured hippocampal neurons caused by a brief exposure to glutamate. This plasticity involves a slow, 70%-80% increase in spine cross-section area associated with a significant reduction in the width of dendrites. These changes are age dependent and expressed only in cells >18 d in vitro (DIV). Activation of both NMDARs and AMPARs as well as a sustained rise of internal calcium levels are necessary for induction of this plasticity. On the other hand, blockade of network activity or mGluRs does not abolish the observed morphological plasticity. Electrophysiologically, a brief exposure to glutamate induces an increase in the magnitude of EPSCs evoked between pairs of neurons, as well as in mEPSC frequency and amplitude, in mature but not young cultures. These results demonstrate an age-dependent, rapid and robust morphological and functional change in cultured central neurons that may contribute to their ability to express long term synaptic plasticity.
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Affiliation(s)
- Stav Sapoznik
- Department of Neurobiology, the Weizmann Institute of Science, Rehovot 76100, Israel
| | - Miriam Ivenshitz
- Department of Neurobiology, the Weizmann Institute of Science, Rehovot 76100, Israel
- Corresponding author.E-mail ; fax 972-8-9344140
| | - Menahem Segal
- Department of Neurobiology, the Weizmann Institute of Science, Rehovot 76100, Israel
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111
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Lisman J, Raghavachari S. A unified model of the presynaptic and postsynaptic changes during LTP at CA1 synapses. ACTA ACUST UNITED AC 2006; 2006:re11. [PMID: 17033044 DOI: 10.1126/stke.3562006re11] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Long-term potentiation (LTP) has been studied extensively at CA1 synapses of the hippocampus, and there is evidence implicating both postsynaptic and presynaptic changes in this process. These changes include (i) addition of AMPA channels to the extrasynaptic membrane and diffusional equilibrium of extrasynaptic receptors with synaptic receptors, (ii) sudden addition of AMPA channels to the synapse in large groups, (iii) a change in the mode of glutamate release (presumably from kiss-and-run to full fusion), and (iv) a delayed increase in the number of vesicles released. However, it remains unclear whether (or how) these changes work together. We have incorporated all of these processes into a structural model of the synapse. We propose that the synapse is composed of transsynaptic modules that function quasi-independently in AMPA-mediated transmission. Under basal conditions, synapses are partially silent; some modules are AMPA-silent (but contribute to NMDA-mediated transmission), whereas others are functional (and contribute to both AMPA- and NMDA-mediated transmission). During LTP, there is both a rapid change in the mode of vesicle fusion and a rapid insertion of a postsynaptic complex (a hyperslot) containing many proteins (slots) capable of binding AMPA channels. The combined effect of these pre- and postsynaptic changes is to convert AMPA-silent modules into functional modules. Slot filling is transiently enhanced by a rapid increase in extrasynaptic GluR1, a form of the AMPA-type receptor. A slower transsynaptic growth process adds AMPA-silent modules to the synapse, enhancing the number of vesicles released and thereby enhancing the NMDA response. This model accounts for a broad range of data, including the LTP-induced changes in quantal parameters. The model also provides a coherent explanation for the diverse effects of GluR1 knockout on basal transmission, LTP, and distance-dependent scaling.
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Affiliation(s)
- John Lisman
- Department of Biology, Brandeis University, Waltham, MA 02454, USA.
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112
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Abstract
Neurons are among the largest and most complex cells in the body. Their immense size and intricate geometry pose many unique cell-biological problems. How is dendritic architecture established and maintained? How do neurons traffic newly synthesized integral membrane proteins over such long distances to synapses? Functionally, protein trafficking to and from the postsynaptic membrane has emerged as a key mechanism underlying various forms of synaptic plasticity. Which organelles are involved in postsynaptic trafficking, and how do they integrate and respond to activity at individual synapses? Here we review what is currently known about long-range trafficking of newly synthesized postsynaptic proteins as well as the local rules that govern postsynaptic trafficking at individual synapses.
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Affiliation(s)
- Matthew J Kennedy
- Howard Hughes Medical Institute, Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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113
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Parrish AR, Wang W, Wang L. Manipulating proteins for neuroscience. Curr Opin Neurobiol 2006; 16:585-92. [PMID: 16956756 DOI: 10.1016/j.conb.2006.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Accepted: 08/24/2006] [Indexed: 10/24/2022]
Abstract
The design and manipulation of proteins has created many tools that have become popular in neurobiological studies, and new developments in protein science will be the fuel for future research. Genetically encoded protein-based biosensors have been developed with a wider range of sensing moieties, enabling detection of changes in localized protein synthesis, voltage, glutamate and/or glucose levels. Existing sensors, such as cameleon, have been modified and improved. Heterologous expression of Channelrhodopsin-2 and other light-gated methods for controlling cellular polarization enable action potentials to be non-invasively evoked, facilitating the study and modulation of behavior in intact animals. Finally, new methods in protein manipulation, including the site-specific incorporation of unnatural amino acids in vivo and the directed evolution of proteins, show promise in elucidating neural function with greater precision and flexibility.
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Affiliation(s)
- Angela R Parrish
- The Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037-1099 USA
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114
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Groc L, Choquet D. AMPA and NMDA glutamate receptor trafficking: multiple roads for reaching and leaving the synapse. Cell Tissue Res 2006; 326:423-38. [PMID: 16847641 DOI: 10.1007/s00441-006-0254-9] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Accepted: 05/18/2006] [Indexed: 11/29/2022]
Abstract
Glutamate receptor trafficking in and out of synapses is one of the core mechanisms for rapid changes in the number of functional receptors during synaptic plasticity. Recent data have shown that the fast gain and loss of receptors from synaptic sites are accounted for by endocytic/exocytic processes and by their lateral diffusion in the plane of the membrane. These events are interdependent and regulated by neuronal activity and interactions with scaffolding proteins. We review here the main cellular steps for AMPA and NMDA receptor synthesis, traffic within intracellular organelles, membrane exocytosis/endocytosis and surface trafficking. We focus on new findings that shed light on the regulation of receptor cycling events and surface trafficking and the way that this might reshape our thinking about the specific regulation of receptor accumulation at synapses.
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Affiliation(s)
- Laurent Groc
- UMR 5091 CNRS-Université de Bordeaux 2 Physiologie Cellulaire de la Synapse, Institut François Magendie, Rue Camille Saint Saëns, 33077 Bordeaux Cédex, France
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115
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Abstract
Nascent synaptic networks have a high incidence of silent synapses. In this issue of Neuron, Shen et al. show that a brief burst of action potentials rapidly awaken silent synapses by increasing the availability of synaptic vesicles for fusion through BDNF-triggered presynaptic actin remodeling mediated by the small GTPase Cdc42.
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Affiliation(s)
- Deniz Atasoy
- Center for Basic Neuroscience, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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116
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McCormack SG, Stornetta RL, Zhu JJ. Synaptic AMPA receptor exchange maintains bidirectional plasticity. Neuron 2006; 50:75-88. [PMID: 16600857 DOI: 10.1016/j.neuron.2006.02.027] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2005] [Revised: 12/31/2005] [Accepted: 02/22/2006] [Indexed: 11/20/2022]
Abstract
Activity-dependent synaptic delivery of GluR1-, GluR2L-, and GluR4-containing AMPA receptors (-Rs) and removal of GluR2-containing AMPA-Rs mediate synaptic potentiation and depression, respectively. The obvious puzzle is how synapses maintain the capacity for bidirectional plasticity if different AMPA-Rs are utilized for potentiation and depression. Here, we show that synaptic AMPA-R exchange is essential for maintaining the capacity for bidirectional plasticity. The exchange process consists of activity-independent synaptic removal of GluR1-, GluR2L-, or GluR4-containing AMPA-Rs and refilling with GluR2-containing AMPA-Rs at hippocampal and cortical synapses in vitro and in intact brains. In GluR1 and GluR2 knockout mice, initiation or completion of synaptic AMPA-R exchange is compromised, respectively. The complementary AMPA-R removal and refilling events in the exchange process ultimately maintain synaptic strength unchanged, but their long rate time constants ( approximately 15-18 hr) render transmission temporarily depressed in the middle of the exchange. These results suggest that the previously hypothesized "slot" proteins, rather than AMPA-Rs, code and maintain transmission efficacy at central synapses.
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Affiliation(s)
- Stefanie G McCormack
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
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117
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Cull-Candy S, Kelly L, Farrant M. Regulation of Ca2+-permeable AMPA receptors: synaptic plasticity and beyond. Curr Opin Neurobiol 2006; 16:288-97. [PMID: 16713244 DOI: 10.1016/j.conb.2006.05.012] [Citation(s) in RCA: 335] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Accepted: 05/08/2006] [Indexed: 12/13/2022]
Abstract
AMPA-type glutamate receptors (AMPARs) mediate most fast excitatory synaptic transmission in the brain. Diversity in excitatory signalling arises, in part, from functional differences among AMPAR subtypes. Although the rapid insertion or deletion of AMPARs is recognised as important for the expression of conventional forms of long-term synaptic plasticity--triggered, for example, by Ca2+ entry through NMDA-type glutamate receptors--only recently has attention focused on novel forms of plasticity that are regulated by, or alter the expression of, Ca2+-permeable AMPARs. The dynamic regulation of these receptors is important for normal synaptic function and in disease states.
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Affiliation(s)
- Stuart Cull-Candy
- Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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Stephan KE, Baldeweg T, Friston KJ. Synaptic plasticity and dysconnection in schizophrenia. Biol Psychiatry 2006; 59:929-39. [PMID: 16427028 DOI: 10.1016/j.biopsych.2005.10.005] [Citation(s) in RCA: 586] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 10/14/2005] [Accepted: 10/29/2005] [Indexed: 11/24/2022]
Abstract
Current pathophysiological theories of schizophrenia highlight the role of altered brain connectivity. This dysconnectivity could manifest 1) anatomically, through structural changes of association fibers at the cellular level, and/or 2) functionally, through aberrant control of synaptic plasticity at the synaptic level. In this article, we review the evidence for these theories, focusing on the modulation of synaptic plasticity. In particular, we discuss how dysconnectivity, observed between brain regions in schizophrenic patients, could result from abnormal modulation of N-methyl-D-aspartate (NMDA)-dependent plasticity by other neurotransmitter systems. We focus on the implication of the dysconnection hypothesis for functional imaging at the systems level. In particular, we review recent advances in measuring plasticity in the human brain using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) that can be used to address dysconnectivity in schizophrenia. Promising experimental paradigms include perceptual and reinforcement learning. We describe how theoretical and causal models of brain responses might contribute to a mechanistic understanding of synaptic plasticity in schizophrenia.
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Affiliation(s)
- Klaas E Stephan
- Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London, London, United Kingdom.
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120
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Plant K, Pelkey KA, Bortolotto ZA, Morita D, Terashima A, McBain CJ, Collingridge GL, Isaac JTR. Transient incorporation of native GluR2-lacking AMPA receptors during hippocampal long-term potentiation. Nat Neurosci 2006; 9:602-4. [PMID: 16582904 DOI: 10.1038/nn1678] [Citation(s) in RCA: 409] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Accepted: 03/06/2006] [Indexed: 11/08/2022]
Abstract
Postnatal glutamatergic principal neuron synapses are typically presumed to express only calcium-impermeable (CI), GluR2-containing AMPARs under physiological conditions. Here, however, we demonstrate that long-term potentiation (LTP) in CA1 hippocampal pyramidal neurons causes rapid incorporation of GluR2-lacking calcium-permeable (CP)-AMPARs: CP-AMPARs are present transiently, being replaced by GluR2-containing AMPARs approximately 25 min after LTP induction. Thus, CP-AMPARs are physiologically expressed at CA1 pyramidal cell synapses during LTP, and may be required for LTP consolidation.
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Affiliation(s)
- Karen Plant
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, School of Medical Sciences, Bristol BS8 1TD, UK
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121
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Aronoff R, Petersen CCH. Controlled and localized genetic manipulation in the brain. J Cell Mol Med 2006; 10:333-52. [PMID: 16796803 PMCID: PMC3933125 DOI: 10.1111/j.1582-4934.2006.tb00403.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Accepted: 04/26/2006] [Indexed: 12/28/2022] Open
Abstract
Brain structure and function are determined in part through experience and in part through our inherited genes. A powerful approach for unravelling the balance between activity-dependent neuronal plasticity and genetic programs is to directly manipulate the genome. Such molecular genetic studies have been greatly aided by the remarkable progress of large-scale genome sequencing efforts. Sophisticated mouse genetic manipulations allow targeted point-mutations, deletions and additions to the mouse genome. These can be regulated through inducible promoters expressing in genetically specified neuronal cell types. However, despite significant progress it remains difficult to target specific brain regions through transgenesis alone. Recent work suggests that transduction vectors, like lentiviruses and adeno-associated viruses, may provide suitable additional tools for localized and controlled genetic manipulation. Furthermore, studies with such vectors may aid the development of human genetic therapies for brain diseases.
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Affiliation(s)
- Rachel Aronoff
- Laboratory of Sensory Processing, Brain Mind Institute, Ecole Polytechnique Fédérale de LausanneLausanne, Switzerland
| | - C C H Petersen
- Laboratory of Sensory Processing, Brain Mind Institute, Ecole Polytechnique Fédérale de LausanneLausanne, Switzerland
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122
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Abstract
Glutamate, the major excitatory neurotransmitter in the brain, acts primarily on two types of ionotropic receptors: alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and N-methyl-d-aspartate (NMDA) receptors. Work over the past decade indicates that regulated changes in the number of synaptic AMPA receptors may serve as a mechanism for information storage. Recent studies demonstrate that a family of small transmembrane AMPA receptor regulatory proteins (TARPs) controls both AMPA receptor trafficking and channel gating. TARPs provide the first example of auxiliary subunits of ionotropic receptors. Here we review the pivotal role that TARPs play in the life cycle of AMPA receptors.
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Affiliation(s)
- Roger A Nicoll
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, CA 94143, USA.
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123
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Thompson SM, Kao JPY, Kramer RH, Poskanzer KE, Silver RA, Digregorio D, Wang SSH. Flashy science: controlling neural function with light. J Neurosci 2006; 25:10358-65. [PMID: 16280572 PMCID: PMC6725808 DOI: 10.1523/jneurosci.3515-05.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Scott M Thompson
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA.
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Liu SJ, Zukin RS. Phosphorylation of the AMPA receptor GluR1 subunit is required for synaptic plasticity and retention of spatial memory. Cell 2003; 30:126-34. [PMID: 17275103 DOI: 10.1016/j.tins.2007.01.006] [Citation(s) in RCA: 403] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 12/21/2006] [Accepted: 01/18/2007] [Indexed: 10/23/2022]
Abstract
Plasticity of the nervous system is dependent on mechanisms that regulate the strength of synaptic transmission. Excitatory synapses in the brain undergo long-term potentiation (LTP) and long-term depression (LTD), cellular models of learning and memory. Protein phosphorylation is required for the induction of many forms of synaptic plasticity, including LTP and LTD. However, the critical kinase substrates that mediate plasticity have not been identified. We previously reported that phosphorylation of the GluR1 subunit of AMPA receptors, which mediate rapid excitatory transmission in the brain, is modulated during LTP and LTD. To test if GluR1 phosphorylation is necessary for plasticity and learning and memory, we generated mice with knockin mutations in the GluR1 phosphorylation sites. The phosphomutant mice show deficits in LTD and LTP and have memory defects in spatial learning tasks. These results demonstrate that phosphorylation of GluR1 is critical for LTD and LTP expression and the retention of memories.
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Affiliation(s)
- Siqiong June Liu
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA.
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