151
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Therapeutic gene silencing strategies for polyglutamine disorders. Trends Genet 2010; 26:29-38. [DOI: 10.1016/j.tig.2009.11.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 11/05/2009] [Accepted: 11/05/2009] [Indexed: 11/18/2022]
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152
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Rojas C, Thomas AG, Alt J, Stathis M, Zhang J, Rubenstein EB, Sebastiani S, Cantoreggi S, Slusher BS. Palonosetron triggers 5-HT3 receptor internalization and causes prolonged inhibition of receptor function. Eur J Pharmacol 2010; 626:193-9. [DOI: 10.1016/j.ejphar.2009.10.002] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Accepted: 10/07/2009] [Indexed: 10/20/2022]
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153
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Micevych P, Bondar G, Kuo J. Estrogen actions on neuroendocrine glia. Neuroendocrinology 2010; 91:211-22. [PMID: 20332598 PMCID: PMC2889254 DOI: 10.1159/000289568] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 02/18/2010] [Indexed: 12/25/2022]
Abstract
Astrocytes are the most abundant cells in the central nervous system (CNS). It appears that astrocytes are as diverse as neurons, having different phenotypes in various regions throughout the brain and participating in intercellular communication that involves signaling to neurons. It is not surprising then that astrocytes in the hypothalamus have an active role in the CNS regulation of reproduction. In addition to the traditional mechanism involving ensheathment of neurons and processes, astrocytes may have a critical role in regulating estrogen-positive feedback. Work in our laboratory has focused on the relationship between circulating estradiol and progesterone synthesized de novo in the brain. We have demonstrated that circulating estradiol stimulates the synthesis of progesterone in adult hypothalamic astrocytes, and this neuroprogesterone is critical for initiating the LH surge. Estradiol cell signaling is initiated at the cell membrane and involves the transactivation of metabotropic glutamate receptor type 1a (mGluR1a) leading to the release of intracellular stores of calcium. We used surface biotinylation to demonstrate that estrogen receptor-alpha (ERalpha) is present in the cell membrane and has an extracellular portion. Like other membrane receptors, ERalpha is inserted into the membrane and removed via internalization after agonist stimulation. This trafficking is directly regulated by estradiol, which rapidly and transiently increases the levels of membrane ERalpha, and upon activation, increases internalization that finally leads to ERalpha degradation. This autoregulation temporally limits membrane-initiated estradiol cell signaling. Thus, neuroprogesterone, the necessary signal for the LH surge, is released when circulating levels of estradiol peak on proestrus and activate progesterone receptors whose expression has been induced by the gradual rise of estradiol during follicular development.
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Affiliation(s)
- Paul Micevych
- Department of Neurobiology, Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, Calif., USA
- *Paul Micevych, Department of Neurobiology, David Geffen School of Medicine at UCLA, 10833 LeConte Avenue, 73-078 CHS, Los Angeles, CA 90095-1763 (USA), Tel. +1 310 206 8265, Fax +1 310 825 2224, E-Mail
| | - Galyna Bondar
- Department of Neurobiology, Laboratory of Neuroendocrinology, UCLA Brain Research Institute, Los Angeles, Calif., USA
| | - John Kuo
- Department of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA, Los Angeles, Calif., USA
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154
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HAGEWOUD ROELINA, HAVEKES ROBBERT, NOVATI ARIANNA, KEIJSER JANN, VAN DER ZEE EDDYA, MEERLO PETER. Sleep deprivation impairs spatial working memory and reduces hippocampal AMPA receptor phosphorylation. J Sleep Res 2009; 19:280-8. [DOI: 10.1111/j.1365-2869.2009.00799.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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155
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Spicarova D, Palecek J. Modulation of AMPA excitatory postsynaptic currents in the spinal cord dorsal horn neurons by insulin. Neuroscience 2009; 166:305-11. [PMID: 20005924 DOI: 10.1016/j.neuroscience.2009.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Revised: 11/16/2009] [Accepted: 12/02/2009] [Indexed: 11/17/2022]
Abstract
Glutamate AMPA receptors are critical for sensory transmission at the spinal cord dorsal horn (DH). Plasma membrane AMPA receptor endocytosis that can be induced by insulin may underlie long term modulation of synaptic transmission. Insulin receptors (IRs) are known to be expressed on spinal cord DH neurons, but their possible role in sensory transmission has not been studied. In this work the effect of insulin application on fast excitatory postsynaptic currents (EPSCs) mediated by AMPA receptors evoked in DH neurons was evaluated. Acute spinal cord slices from 6 to 10 day old mice were used to record EPSCs evoked in visually identified superficial DH neurons by dorsal root primary afferent stimulation. AMPA EPSCs could be evoked in all of the tested neurons. In 75% of the neurons the size of the AMPA EPSCs was reduced to 62.1% and to 68.9% of the control values when 0.5 or 10 microM insulin was applied. There was no significant change in the size of the AMPA EPSCs in the remaining 25% of DH neurons. The membrane permeable protein tyrosine kinase inhibitor, lavendustin A (10 microM), prevented the insulin induced AMPA EPSC depression. Our results suggest a possible role of the insulin pathway in modulation of sensory and nociceptive synaptic transmission in the spinal cord.
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Affiliation(s)
- D Spicarova
- Department of Functional Morphology, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 14220 Prague 4, Czech Republic
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156
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Zhao WQ, Santini F, Breese R, Ross D, Zhang XD, Stone DJ, Ferrer M, Townsend M, Wolfe AL, Seager MA, Kinney GG, Shughrue PJ, Ray WJ. Inhibition of calcineurin-mediated endocytosis and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors prevents amyloid beta oligomer-induced synaptic disruption. J Biol Chem 2009; 285:7619-32. [PMID: 20032460 DOI: 10.1074/jbc.m109.057182] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synaptic degeneration, including impairment of synaptic plasticity and loss of synapses, is an important feature of Alzheimer disease pathogenesis. Increasing evidence suggests that these degenerative synaptic changes are associated with an accumulation of soluble oligomeric assemblies of amyloid beta (Abeta) known as ADDLs. In primary hippocampal cultures ADDLs bind to a subpopulation of neurons. However the molecular basis of this cell type-selective interaction is not understood. Here, using siRNA screening technology, we identified alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits and calcineurin as candidate genes potentially involved in ADDL-neuron interactions. Immunocolocalization experiments confirmed that ADDL binding occurs in dendritic spines that express surface AMPA receptors, particularly the calcium-impermeable type II AMPA receptor subunit (GluR2). Pharmacological removal of the surface AMPA receptors or inhibition of AMPA receptors with antagonists reduces ADDL binding. Furthermore, using co-immunoprecipitation and photoreactive amino acid cross-linking, we found that ADDLs interact preferentially with GluR2-containing complexes. We demonstrate that calcineurin mediates an endocytotic process that is responsible for the rapid internalization of bound ADDLs along with surface AMPA receptor subunits, which then both colocalize with cpg2, a molecule localized specifically at the postsynaptic endocytic zone of excitatory synapses that plays an important role in activity-dependent glutamate receptor endocytosis. Both AMPA receptor and calcineurin inhibitors prevent oligomer-induced surface AMPAR and spine loss. These results support a model of disease pathogenesis in which Abeta oligomers interact selectively with neurotransmission pathways at excitatory synapses, resulting in synaptic loss via facilitated endocytosis. Validation of this model in human disease would identify therapeutic targets for Alzheimer disease.
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Affiliation(s)
- Wei-Qin Zhao
- Department of Neurology, Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
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157
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Abstract
Estradiol has rapid actions in the CNS that are mediated by membrane estrogen receptors (ERs) and activate cell signaling pathways through interaction with metabotropic glutamate receptors (mGluRs). Membrane-initiated estradiol signaling increases the free cytoplasmic calcium concentration ([Ca(2+)](i)) that stimulates the synthesis of neuroprogesterone in astrocytes. We used surface biotinylation to demonstrate that ERalpha has an extracellular portion. In addition to the full-length ERalpha [apparent molecular weight (MW), 66 kDa], surface biotinylation labeled an ERalpha-immunoreactive protein (MW, approximately 52 kDa) identified by both COOH- and NH(2)-directed antibodies. Estradiol treatment regulated membrane levels of both proteins in parallel: within 5 min, estradiol significantly increased membrane levels of the 66 and 52 kDa ERalpha. Internalization, a measure of membrane receptor activation, was also increased by estradiol with a similar time course. Continuous treatment with estradiol for 24-48 h reduced ERalpha levels, suggesting receptor downregulation. Estradiol also increased mGluR1a trafficking and internalization, consistent with the proposed ERalpha-mGluR1a interaction. Blocking ER with ICI 182,780 or mGluR1a with LY 367385 prevented ERalpha trafficking to and from the membrane. Estradiol-induced [Ca(2+)](i) flux was also significantly increased at the time of peak ERalpha activation/internalization. These results demonstrate that ERalpha is present in the membrane and has an extracellular portion. Furthermore, membrane levels and internalization of ERalpha are regulated by estradiol and mGluR1a ligands. The pattern of trafficking into and out of the membrane suggests that the changing concentration of estradiol during the estrous cycle regulates ERalpha to augment and then terminate membrane-initiated signaling.
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158
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Loebrich S, Nedivi E. The function of activity-regulated genes in the nervous system. Physiol Rev 2009; 89:1079-103. [PMID: 19789377 DOI: 10.1152/physrev.00013.2009] [Citation(s) in RCA: 166] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The mammalian brain is plastic in the sense that it shows a remarkable capacity for change throughout life. The contribution of neuronal activity to brain plasticity was first recognized in relation to critical periods of development, when manipulating the sensory environment was found to profoundly affect neuronal morphology and receptive field properties. Since then, a growing body of evidence has established that brain plasticity extends beyond development and is an inherent feature of adult brain function, spanning multiple domains, from learning and memory to adaptability of primary sensory maps. Here we discuss evolution of the current view that plasticity of the adult brain derives from dynamic tuning of transcriptional control mechanisms at the neuronal level, in response to external and internal stimuli. We then review the identification of "plasticity genes" regulated by changes in the levels of electrical activity, and how elucidating their cellular functions has revealed the intimate role transcriptional regulation plays in fundamental aspects of synaptic transmission and circuit plasticity that occur in the brain on an every day basis.
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Affiliation(s)
- Sven Loebrich
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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159
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Han K, Kim MH, Seeburg D, Seo J, Verpelli C, Han S, Chung HS, Ko J, Lee HW, Kim K, Heo WD, Meyer T, Kim H, Sala C, Choi SY, Sheng M, Kim E. Regulated RalBP1 binding to RalA and PSD-95 controls AMPA receptor endocytosis and LTD. PLoS Biol 2009; 7:e1000187. [PMID: 19823667 PMCID: PMC2730530 DOI: 10.1371/journal.pbio.1000187] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Accepted: 07/30/2009] [Indexed: 11/18/2022] Open
Abstract
Long-term depression (LTD) is a long-lasting activity-dependent decrease in synaptic strength. NMDA receptor (NMDAR)-dependent LTD, an extensively studied form of LTD, involves the endocytosis of AMPA receptors (AMPARs) via protein dephosphorylation, but the underlying mechanism has remained unclear. We show here that a regulated interaction of the endocytic adaptor RalBP1 with two synaptic proteins, the small GTPase RalA and the postsynaptic scaffolding protein PSD-95, controls NMDAR-dependent AMPAR endocytosis during LTD. NMDAR activation stimulates RalA, which binds and translocates widespread RalBP1 to synapses. In addition, NMDAR activation dephosphorylates RalBP1, promoting the interaction of RalBP1 with PSD-95. These two regulated interactions are required for NMDAR-dependent AMPAR endocytosis and LTD and are sufficient to induce AMPAR endocytosis in the absence of NMDAR activation. RalA in the basal state, however, maintains surface AMPARs. We propose that NMDAR activation brings RalBP1 close to PSD-95 to promote the interaction of RalBP1-associated endocytic proteins with PSD-95-associated AMPARs. This suggests that scaffolding proteins at specialized cellular junctions can switch their function from maintenance to endocytosis of interacting membrane proteins in a regulated manner.
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Affiliation(s)
- Kihoon Han
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Myoung-Hwan Kim
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Daniel Seeburg
- The Picower Institute for Learning and Memory, RIKEN-MIT Neuroscience Research Center
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Jinsoo Seo
- Department of Physiology and Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea
| | - Chiara Verpelli
- CNR Institute of Neuroscience and Department of Neurological Sciences, University of Milan, Milan, Italy
| | - Seungnam Han
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Hye Sun Chung
- Department of Anatomy and Division of Brain Korea 21 Biomedical Science, College of Medicine, Korea University, Seoul, Korea
| | - Jaewon Ko
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Hyun Woo Lee
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Karam Kim
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Won Do Heo
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University, Stanford, California, United States of America
| | - Hyun Kim
- Department of Anatomy and Division of Brain Korea 21 Biomedical Science, College of Medicine, Korea University, Seoul, Korea
| | - Carlo Sala
- CNR Institute of Neuroscience and Department of Neurological Sciences, University of Milan, Milan, Italy
| | - Se-Young Choi
- Department of Physiology and Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea
| | - Morgan Sheng
- The Picower Institute for Learning and Memory, RIKEN-MIT Neuroscience Research Center
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Eunjoon Kim
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea
- * E-mail:
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160
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Mielke JG, Mealing GAR. Cellular distribution of the nicotinic acetylcholine receptor alpha7 subunit in rat hippocampus. Neurosci Res 2009; 65:296-306. [PMID: 19682509 DOI: 10.1016/j.neures.2009.08.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 07/31/2009] [Accepted: 08/04/2009] [Indexed: 11/24/2022]
Abstract
The hippocampus is a region of the mammalian brain that has been extensively studied due to its role in many forms of memory. To better understand hippocampal function, significant attention has focused upon the cellular distribution of ligand-gated ion channels. Despite strong cholinergic innervation from the basal forebrain and a dense expression of nicotinic acetylchoine receptors (nAChRs), the cellular distribution of subunits forming these receptors has received little attention. We used organotypic hippocampal slice cultures (OHSCs) to study native alpha7 subunits, which, unlike other nAChR subunits, form a homomeric receptor. Cell-surface biotinylation, cross-linking of surface proteins, and sub-cellular fractionation all revealed a very limited presence of the subunit at the plasma membrane. In contrast, subunits of other receptors displayed significant surface expression. Notably, subunits in adult hippocampal tissue were distributed in a fashion similar to that observed in OHSCs. To monitor alpha7 subunits contained in functional nAChRs, a colourimetric assay using alpha-bungarotoxin (a specific alpha7 nAChR antagonist) was developed, and revealed a majority of binding at the cell surface. To change alpha7 subunit distribution, OHSCs were treated with compounds known to affect other ionotropic receptors-insulin, genistein, and elevated external K(+); however, neither subunit surface expression nor antagonist binding was affected. Our data reveal that hippocampal neurons possess a large internal population of alpha7 subunits under basal conditions, which persists during stimuli affecting tyrosine phosphorylation or neuronal activity. The nature of the internal pool of alpha7 subunits remains to be determined, but should have important implications for hippocampal activity.
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Affiliation(s)
- John G Mielke
- Department of Health Studies and Gerontology, Faculty of Applied Health Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1.
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161
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Trifilieff P, Lavaur J, Pascoli V, Kappès V, Brami-Cherrier K, Pagès C, Micheau J, Caboche J, Vanhoutte P. Endocytosis controls glutamate-induced nuclear accumulation of ERK. Mol Cell Neurosci 2009; 41:325-36. [DOI: 10.1016/j.mcn.2009.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 04/17/2009] [Accepted: 04/20/2009] [Indexed: 10/20/2022] Open
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162
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Maekawa F, Tsuboi T, Pellerin L. Regulation of the intracellular distribution, cell surface expression, and protein levels of AMPA receptor GluR2 subunits by the monocarboxylate transporter MCT2 in neuronal cells. J Neurochem 2009; 109:1767-78. [DOI: 10.1111/j.1471-4159.2009.06100.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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163
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Pierre K, Chatton JY, Parent A, Repond C, Gardoni F, Di Luca M, Pellerin L. Linking supply to demand: the neuronal monocarboxylate transporter MCT2 and the alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid receptor GluR2/3 subunit are associated in a common trafficking process. Eur J Neurosci 2009; 29:1951-63. [PMID: 19453627 DOI: 10.1111/j.1460-9568.2009.06756.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
MCT2 is the major neuronal monocarboxylate transporter (MCT) that allows the supply of alternative energy substrates such as lactate to neurons. Recent evidence obtained by electron microscopy has demonstrated that MCT2, like alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, is localized in dendritic spines of glutamatergic synapses. Using immunofluorescence, we show in this study that MCT2 colocalizes extensively with GluR2/3 subunits of AMPA receptors in neurons from various mouse brain regions as well as in cultured neurons. It also colocalizes with GluR2/3-interacting proteins, such as C-kinase-interacting protein 1, glutamate receptor-interacting protein 1 and clathrin adaptor protein. Coimmunoprecipitation of MCT2 with GluR2/3 and C-kinase-interacting protein 1 suggests their close interaction within spines. Parallel changes in the localization of both MCT2 and GluR2/3 subunits at and beneath the plasma membrane upon various stimulation paradigms were unraveled using an original immunocytochemical and transfection approach combined with three-dimensional image reconstruction. Cell culture incubation with AMPA or insulin triggered a marked intracellular accumulation of both MCT2 and GluR2/3, whereas both tumor necrosis factor alpha and glycine (with glutamate) increased their cell surface immunolabeling. Similar results were obtained using Western blots performed on membrane or cytoplasm-enriched cell fractions. Finally, an enhanced lactate flux into neurons was demonstrated after MCT2 translocation on the cell surface. These observations provide unequivocal evidence that MCT2 is linked to AMPA receptor GluR2/3 subunits and undergoes a similar translocation process in neurons upon activation. MCT2 emerges as a novel component of the synaptic machinery putatively linking neuroenergetics to synaptic transmission.
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Affiliation(s)
- Karin Pierre
- Département de Physiologie, Université de Lausanne, 7 Rue du Bugnon, CH-1005 Lausanne, Switzerland.
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164
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Essmann CL, Martinez E, Geiger JC, Zimmer M, Traut MH, Stein V, Klein R, Acker-Palmer A. Serine phosphorylation of ephrinB2 regulates trafficking of synaptic AMPA receptors. Nat Neurosci 2009; 11:1035-43. [PMID: 19160501 DOI: 10.1038/nn.2171] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Plasticity in the brain is essential for maintaining memory and learning and is associated with the dynamic membrane trafficking of AMPA receptors. EphrinB proteins, ligands for EphB receptor tyrosine kinases, are transmembrane molecules with signaling capabilities that are required for spine morphogenesis, synapse formation and synaptic plasticity. Here, we describe a molecular mechanism for ephrinB2 function in controlling synaptic transmission. EphrinB2 signaling is critical for the stabilization of AMPA receptors at the cellular membrane. Mouse hippocampal neurons from conditional ephrinB2 knockouts showed enhanced constitutive internalization of AMPA receptors and reduced synaptic transmission. Mechanistically, glutamate receptor interacting proteins bridge ephrinB ligands and AMPA receptors. Moreover, this function involved a regulatory aspect of ephrinB reverse signaling that involves the phosphorylation of a single serine residue in their cytoplasmic tails. In summary, our findings uncover a model of cooperative AMPA receptor and ephrinB reverse signaling at the synapse.
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Affiliation(s)
- Clara L Essmann
- Institute of Cell Biology and Neuroscience and Cluster of Excellence Macromolecular Complexes, Goethe University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
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165
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Zhang D, Hou Q, Wang M, Lin A, Jarzylo L, Navis A, Raissi A, Liu F, Man HY. Na,K-ATPase activity regulates AMPA receptor turnover through proteasome-mediated proteolysis. J Neurosci 2009; 29:4498-511. [PMID: 19357275 PMCID: PMC2680442 DOI: 10.1523/jneurosci.6094-08.2009] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2008] [Revised: 02/27/2009] [Accepted: 03/09/2009] [Indexed: 02/07/2023] Open
Abstract
Neuronal activity largely depends on two key components on the membrane: the Na,K-ATPase (NKA) that maintains the ion gradients and sets the foundation of excitability, and the ionotropic glutamatergic AMPA receptors (AMPARs) through which sodium influx forms the driving force for excitation. Because the frequent sodium transients from glutamate receptor activity need to be efficiently extruded, a functional coupling between NKA and AMPARs should be a necessary cellular device for synapse physiology. We show that NKA is enriched at synapses and associates with AMPARs. NKA dysfunction induces a rapid reduction in AMPAR cell-surface expression as well as total protein abundance, leading to a long-lasting depression in synaptic transmission. AMPAR proteolysis requires sodium influx, proteasomal activity and receptor internalization. These data elucidate a novel mechanism by which NKA regulates AMPAR turnover and thereby synaptic strength and brain function.
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Affiliation(s)
- Dawei Zhang
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
| | - Qingming Hou
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
| | - Min Wang
- Department of Neuroscience, Centre for Addiction and Mental Health, Clarke Division, University of Toronto, Toronto, Ontario, Canada M5T 1R8
| | - Amy Lin
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
| | - Larissa Jarzylo
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
| | - Allison Navis
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
| | - Aram Raissi
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
| | - Fang Liu
- Department of Neuroscience, Centre for Addiction and Mental Health, Clarke Division, University of Toronto, Toronto, Ontario, Canada M5T 1R8
| | - Heng-Ye Man
- Department of Biology, Boston University, Boston, Massachusetts 02215, and
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166
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Park JS, Voitenko N, Petralia RS, Guan X, Xu JT, Steinberg JP, Takamiya K, Sotnik A, Kopach O, Huganir RL, Tao YX. Persistent inflammation induces GluR2 internalization via NMDA receptor-triggered PKC activation in dorsal horn neurons. J Neurosci 2009; 29:3206-19. [PMID: 19279258 PMCID: PMC2664544 DOI: 10.1523/jneurosci.4514-08.2009] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Revised: 02/04/2009] [Accepted: 02/09/2009] [Indexed: 01/23/2023] Open
Abstract
Spinal cord GluR2-lacking AMPA receptors (AMPARs) contribute to nociceptive hypersensitivity in persistent pain, but the molecular mechanisms underlying this event are not completely understood. We report that complete Freund's adjuvant (CFA)-induced peripheral inflammation induces synaptic GluR2 internalization in dorsal horn neurons during the maintenance of CFA-evoked nociceptive hypersensitivity. This internalization is initiated by GluR2 phosphorylation at Ser(880) and subsequent disruption of GluR2 binding to its synaptic anchoring protein (GRIP), resulting in a switch of GluR2-containing AMPARs to GluR2-lacking AMPARs and an increase of AMPAR Ca(2+) permeability at the synapses in dorsal horn neurons. Spinal cord NMDA receptor-mediated triggering of protein kinase C (PKC) activation is required for the induction and maintenance of CFA-induced dorsal horn GluR2 internalization. Moreover, preventing CFA-induced spinal GluR2 internalization through targeted mutation of the GluR2 PKC phosphorylation site impairs CFA-evoked nociceptive hypersensitivity during the maintenance period. These results suggest that dorsal horn GluR2 internalization might participate in the maintenance of NMDA receptor/PKC-dependent nociceptive hypersensitivity in persistent inflammatory pain.
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Affiliation(s)
- Jang-Su Park
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Nana Voitenko
- Department of General Physiology of Nervous System, Bogomoletz Institute of Physiology, Kiev 01024, Ukraine
| | - Ronald S. Petralia
- Laboratory of Neurochemistry, National Institute of Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, and
| | - Xiaowei Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Ji-Tian Xu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | | | | | - Andrij Sotnik
- Department of General Physiology of Nervous System, Bogomoletz Institute of Physiology, Kiev 01024, Ukraine
| | - Olga Kopach
- Department of General Physiology of Nervous System, Bogomoletz Institute of Physiology, Kiev 01024, Ukraine
| | - Richard L. Huganir
- Departments of Neuroscience and
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287
| | - Yuan-Xiang Tao
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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167
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Bezprozvanny I. Calcium signaling and neurodegenerative diseases. Trends Mol Med 2009; 15:89-100. [PMID: 19230774 PMCID: PMC3226745 DOI: 10.1016/j.molmed.2009.01.001] [Citation(s) in RCA: 354] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 01/06/2009] [Accepted: 01/06/2009] [Indexed: 01/08/2023]
Abstract
Neurodegenerative disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD) and spinocerebellar ataxias (SCAs), present an enormous medical, social, financial and scientific problem. Recent evidence indicates that neuronal calcium (Ca2+) signaling is abnormal in many of these disorders. Similar, but less severe, changes in neuronal Ca2+ signaling occur as a result of the normal aging process. The role of aberrant neuronal Ca2+ signaling in the pathogenesis of neurodegenerative disorders is discussed here. The potential utility of Ca2+ blockers for treatment of these disorders is also highlighted. It is reasoned that Ca2+ blockers will be most beneficial clinically when used in combination with other disease-specific therapeutic approaches.
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Affiliation(s)
- Ilya Bezprozvanny
- Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX 75390-9040, USA.
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168
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Bhattacharyya S, Biou V, Xu W, Schlüter O, Malenka RC. A critical role for PSD-95/AKAP interactions in endocytosis of synaptic AMPA receptors. Nat Neurosci 2009; 12:172-81. [PMID: 19169250 PMCID: PMC2694745 DOI: 10.1038/nn.2249] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Accepted: 12/02/2008] [Indexed: 02/04/2023]
Abstract
The endocytosis of AMPA receptors (AMPARs) underlies several forms of synaptic plasticity, including NMDA receptor (NMDAR)-dependent long-term depression (LTD), but the molecular mechanisms responsible for this trafficking remain unknown. We found that PSD-95, a major postsynaptic density protein, is important for NMDAR-triggered endocytosis of synaptic AMPARs in rat neuron cultures because of its binding to A kinase-anchoring protein 150 (AKAP150), a scaffold for specific protein kinases and phosphatases. Knockdown of PSD-95 with shRNA blocked NMDAR-triggered, but not constitutive or mGluR-triggered, endocytosis of AMPARs. Deletion of PSD-95's Src homology 3 and guanylate kinase-like domains, as well as a point mutation (L460P), both of which inhibit binding of PSD-95 to AKAP150, also blocked NMDAR-triggered AMPAR endocytosis. Furthermore, expression of a mutant AKAP150 that does not bind calcineurin inhibited this NMDAR-triggered trafficking event. Our results suggest that PSD-95's interaction with AKAP150 is critical for NMDAR-triggered AMPAR endocytosis and LTD, possibly because these scaffolds position calcineurin in the appropriate subsynaptic domain.
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Affiliation(s)
- Samarjit Bhattacharyya
- Nancy Pritzker Laboratory, Department of Psychiatry and Behavioral Sciences, 1050 Arastradero Road, Stanford University School of Medicine, Palo Alto, California 94304-5552, USA
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169
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Clathrin adaptor AP-1 complex excludes multiple postsynaptic receptors from axons in C. elegans. Proc Natl Acad Sci U S A 2009; 106:1632-7. [PMID: 19164532 DOI: 10.1073/pnas.0812078106] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neurons are highly polarized cells with morphologically and molecularly distinct axonal and dendritic compartments. It is not well understood how postsynaptic receptors are selectively enriched in dendrites in vivo. We investigated the molecular mechanisms of dendritically polarized localization of a glutamate receptor, an acetylcholine receptor, and a ROR-type receptor tyrosine kinase in the interneuron RIA in C. elegans. We found that the clathrin adaptor AP-1 complex mu1 subunit UNC-101 functions cell autonomously to maintain the correct localization of these receptors in a dynamin-dependent manner. In unc-101 mutants, instead of being dendritically enriched, all 3 receptors are evenly distributed in the axonal and dendritic compartments. Surprisingly, UNC-101 predominantly localizes to the axonal compartment, suggesting a possible transcytosis model for the dendritic targeting of neurotransmitter receptors.
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170
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Barrett AB, Billings GO, Morris RGM, van Rossum MCW. State Based Model of Long-Term Potentiation and Synaptic Tagging and Capture. PLoS Comput Biol 2009. [DOI: 10.1117/12.945264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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171
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Bassani S, Valnegri P, Beretta F, Passafaro M. The GLUR2 subunit of AMPA receptors: synaptic role. Neuroscience 2009; 158:55-61. [PMID: 18977416 DOI: 10.1016/j.neuroscience.2008.10.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 09/02/2008] [Accepted: 10/02/2008] [Indexed: 11/26/2022]
Abstract
Ampa receptors mediate the majority of excitatory synaptic transmission in the brain. Thus, the mechanisms that control the developmental and activity-dependent changes in the functional synaptic expression of AMPA receptors are of fundamental importance. Here we focus on the role of GluR2 subunit in synaptic function and plasticity.
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172
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Santos S, Carvalho A, Caldeira M, Duarte C. Regulation of AMPA receptors and synaptic plasticity. Neuroscience 2009; 158:105-25. [DOI: 10.1016/j.neuroscience.2008.02.037] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 01/02/2008] [Accepted: 02/13/2008] [Indexed: 10/22/2022]
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173
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Abstract
Neurodegenerative trinucleotide (CAG) repeat disorders are caused by the expansion of polyglutamine tracts within the disease proteins. Some of these proteins have an unknown function. How does expanded polyglutamine cause target neurons to degenerate, is not clear. Recent evidence suggests that intercellular miscommunication may contribute to polyglutamine pathogenesis in CAG repeat disorders. Polyglutamine induced degeneration of the target neuron can be mediated via glia-neuron interactions. Here we hypothesize during neurodegenerative process the failure of cell: cell interactions have more severe consequences than alterations in intracellular neuron biology. We further believe that bidirectional communication between neurons and glia are prerequisite for the normal development and function of either cell-type. Understanding intercellular signaling mechanisms such as glial trophic factors and their receptors, cell adhesion or other well-defined signaling molecules provide opportunities for developing potential therapies.
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Affiliation(s)
- Parminder J S Vig
- Department of Neurology, University of Mississippi Medical Center, Jackson, Mississippi 39216
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174
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Davidson HT, Xiao J, Dai R, Bergson C. Calcyon is necessary for activity-dependent AMPA receptor internalization and LTD in CA1 neurons of hippocampus. Eur J Neurosci 2009; 29:42-54. [PMID: 19120439 PMCID: PMC2771427 DOI: 10.1111/j.1460-9568.2008.06563.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Calcyon is a single transmembrane endocytic protein that regulates clathrin assembly and clathrin-mediated endocytosis in the brain. Ultrastructural studies indicate that calcyon localizes to spines, but whether it regulates glutamate neurotransmission is not known. Here, we show that deletion of the calcyon gene in mice inhibits agonist-stimulated endocytosis of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), without altering basal surface levels of the GluR1 or GluR2 subunits. Whole-cell patch-clamp studies of hippocampal neurons in culture and CA1 synapses in slices revealed that knockout (KO) of calcyon abolishes long-term synaptic depression (LTD), whereas mini-analysis in slices indicated basal transmission in the hippocampus is unaffected by the deletion. Further, transfection of green fluorescent protein-tagged calcyon rescued the ability of KO cultures to undergo LTD. In contrast, intracellular dialysis of a fusion protein containing the clathrin light-chain-binding domain of calcyon blocked the induction of LTD in wild-type hippocampal slices. Taken together, the present studies involving biochemical, immunological and electrophysiological analyses raise the possibility that calcyon plays a specialized role in regulating activity-dependent removal of synaptic AMPARs.
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175
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Barrett AB, Billings GO, Morris RGM, van Rossum MCW. State based model of long-term potentiation and synaptic tagging and capture. PLoS Comput Biol 2009; 5:e1000259. [PMID: 19148264 PMCID: PMC2603667 DOI: 10.1371/journal.pcbi.1000259] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 11/24/2008] [Indexed: 11/17/2022] Open
Abstract
Recent data indicate that plasticity protocols have not only synapse-specific but also more widespread effects. In particular, in synaptic tagging and capture (STC), tagged synapses can capture plasticity-related proteins, synthesized in response to strong stimulation of other synapses. This leads to long-lasting modification of only weakly stimulated synapses. Here we present a biophysical model of synaptic plasticity in the hippocampus that incorporates several key results from experiments on STC. The model specifies a set of physical states in which a synapse can exist, together with transition rates that are affected by high- and low-frequency stimulation protocols. In contrast to most standard plasticity models, the model exhibits both early- and late-phase LTP/D, de-potentiation, and STC. As such, it provides a useful starting point for further theoretical work on the role of STC in learning and memory.
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Affiliation(s)
- Adam B Barrett
- Institute for Adaptive and Neural Computation, University of Edinburgh, Edinburgh, United Kingdom.
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176
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Mao SC, Lin HC, Gean PW. Augmentation of fear extinction by D-cycloserine is blocked by proteasome inhibitors. Neuropsychopharmacology 2008; 33:3085-95. [PMID: 18368037 DOI: 10.1038/npp.2008.30] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
D-Cycloserine (DCS) has been shown to facilitate extinction of conditioned fear in rats and to improve fear reduction of social phobia and fear of heights in human studies. Here, we investigate the mechanism of DCS effect by measuring internalized GluR1 and GluR2 using cell-surface biotinylation techniques. DCS selectively increased NMDA receptor-mediated synaptic response without affecting AMPA receptor-mediated synaptic response. Low-frequency stimulation (LFS) when applied in the presence of DCS induced GluR1 and GluR2 internalization in the amygdala slices. Proteasome inhibitors block DCS facilitation of LFS-induced depotentiation and a reduction in surface levels of GluR1 and GluR2. Furthermore, DCS in combination with LFS reduced cellular levels of PSD-95 and synapse-associated protein 97 (SAP97), which were also blocked by proteasome inhibitors. In the in vivo experiments, DCS-induced reduction of fear-potentiated startle and reversal of conditioning-induced increase in surface expression of GluR1 were blocked by proteasome inhibitors. DCS-treated rats fail to exhibit reinstatement after US-alone presentations. These results suggest that DCS facilitates receptor internalization in the presence of extinction training, resulting in augmented reduction of startle potentiation.
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Affiliation(s)
- Sheng-Chun Mao
- Institute of Basic Medical Sciences, National Cheng-Kung University, Tainan, Taiwan
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177
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Insulin resistance and amyloidogenesis as common molecular foundation for type 2 diabetes and Alzheimer's disease. Biochim Biophys Acta Mol Basis Dis 2008; 1792:482-96. [PMID: 19026743 DOI: 10.1016/j.bbadis.2008.10.014] [Citation(s) in RCA: 241] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2008] [Revised: 10/18/2008] [Accepted: 10/21/2008] [Indexed: 12/22/2022]
Abstract
Characterized as a peripheral metabolic disorder and a degenerative disease of the central nervous system respectively, it is now widely recognized that type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) share several common abnormalities including impaired glucose metabolism, increased oxidative stress, insulin resistance and amyloidogenesis. Several recent studies suggest that this is not an epiphenomenon, but rather these two diseases disrupt common molecular pathways and each disease compounds the progression of the other. For instance, in AD the accumulation of the amyloid-beta peptide (Abeta), which characterizes the disease and is thought to participate in the neurodegenerative process, may also induce neuronal insulin resistance. Conversely, disrupting normal glucose metabolism in transgenic animal models of AD that over-express the human amyloid precursor protein (hAPP) promotes amyloid-peptide aggregation and accelerates the disease progression. Studying these processes at a cellular level suggests that insulin resistance and Abeta aggregation may not only be the consequence of excitotoxicity, aberrant Ca(2+) signals, and proinflammatory cytokines such as TNF-alpha, but may also promote these pathological effectors. At the molecular level, insulin resistance and Abeta disrupt common signal transduction cascades including the insulin receptor family/PI3 kinase/Akt/GSK3 pathway. Thus both disease processes contribute to overlapping pathology, thereby compounding disease symptoms and progression.
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178
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Sanchez-Mejia RO, Newman JW, Toh S, Yu GQ, Zhou Y, Halabisky B, Cissé M, Scearce-Levie K, Cheng IH, Gan L, Palop JJ, Bonventre JV, Mucke L. Phospholipase A2 reduction ameliorates cognitive deficits in a mouse model of Alzheimer's disease. Nat Neurosci 2008; 11:1311-8. [PMID: 18931664 PMCID: PMC2597064 DOI: 10.1038/nn.2213] [Citation(s) in RCA: 290] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Accepted: 09/17/2008] [Indexed: 11/09/2022]
Abstract
Neuronal expression of familial Alzheimer's disease-mutant human amyloid precursor protein (hAPP) and hAPP-derived amyloid-beta (Abeta) peptides causes synaptic dysfunction, inflammation and abnormal cerebrovascular tone in transgenic mice. Fatty acids may be involved in these processes, but their contribution to Alzheimer's disease pathogenesis is uncertain. We used a lipidomics approach to generate a broad profile of fatty acids in brain tissues of hAPP-expressing mice and found an increase in arachidonic acid and its metabolites, suggesting increased activity of the group IV isoform of phospholipase A(2) (GIVA-PLA(2)). The levels of activated GIVA-PLA(2) in the hippocampus were increased in individuals with Alzheimer's disease and in hAPP mice. Abeta caused a dose-dependent increase in GIVA-PLA(2) phosphorylation in neuronal cultures. Inhibition of GIVA-PLA(2) diminished Abeta-induced neurotoxicity. Genetic ablation or reduction of GIVA-PLA(2) protected hAPP mice against Abeta-dependent deficits in learning and memory, behavioral alterations and premature mortality. Inhibition of GIVA-PLA(2) may be beneficial in the treatment and prevention of Alzheimer's disease.
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Affiliation(s)
- Rene O Sanchez-Mejia
- Gladstone Institute of Neurological Disease, San Francisco, California 94158, USA.
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179
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New roles for insulin-like hormones in neuronal signalling and protection: new hopes for novel treatments of Alzheimer's disease? Neurobiol Aging 2008; 31:1495-502. [PMID: 18930564 DOI: 10.1016/j.neurobiolaging.2008.08.023] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 06/21/2008] [Accepted: 08/30/2008] [Indexed: 01/06/2023]
Abstract
Type 2 diabetes has been identified as a risk factor for Alzheimer's disease (AD). This is most likely due to the desensitisation of insulin receptors in the brain. Insulin acts as a growth factor and supports neuronal repair, dendritic sprouting, and differentiation. This review discusses the potential role that insulin-like hormones could play in ameliorating the reduced growth factor signalling in the brains of people with AD. The incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) have very similar properties in protecting neurons from toxic effects, and are capable of reversing the detrimental effects that beta-amyloid fragments have on synaptic plasticity. Therefore, incretins show great promise as a novel treatment for reducing degenerative processes in AD.
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180
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Cruz LA, Estébanez-Perpiñá E, Pfaff S, Borngraeber S, Bao N, Blethrow J, Fletterick RJ, England PM. 6-Azido-7-nitro-1,4-dihydroquinoxaline-2,3-dione (ANQX) forms an irreversible bond to the active site of the GluR2 AMPA receptor. J Med Chem 2008; 51:5856-60. [PMID: 18754610 PMCID: PMC2945402 DOI: 10.1021/jm701517b] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
AMPA receptors mediate fast excitatory synaptic transmission and are essential for synaptic plasticity. ANQX, a photoreactive AMPA receptor antagonist, is an important biological probe used to irreversibly inactivate AMPA receptors. Here, using X-ray crystallography and mass spectroscopy, we report that ANQX forms two major products in the presence of the GluR2 AMPAR ligand-binding core (S1S2J). Upon photostimulation, ANQX reacts intramolecularly to form FQX or intermolecularly to form a covalent adduct with Glu705.
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Affiliation(s)
| | | | | | | | | | | | | | - Pamela M. England
- To whom correspondence should be addressed. Phone: (415) 502-6606. Fax: (415) 514-4070.
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181
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Li Q, Burrell BD. CNQX and AMPA inhibit electrical synaptic transmission: a potential interaction between electrical and glutamatergic synapses. Brain Res 2008; 1228:43-57. [PMID: 18601913 PMCID: PMC2612578 DOI: 10.1016/j.brainres.2008.06.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 06/02/2008] [Accepted: 06/11/2008] [Indexed: 02/07/2023]
Abstract
Electrical synapses play an important role in signaling between neurons and the synaptic connections between many neurons possess both electrical and chemical components. Although modulation of electrical synapses is frequently observed, the cellular processes that mediate such changes have not been studied as thoroughly as plasticity in chemical synapses. In the leech (Hirudo sp), the competitive AMPA receptor antagonist CNQX inhibited transmission at the rectifying electrical synapse of a mixed glutamatergic/electrical synaptic connection. This CNQX-mediated inhibition of the electrical synapse was blocked by concanavalin A (Con A) and dynamin inhibitory peptide (DIP), both of which are known to inhibit endocytosis of neurotransmitter receptors. CNQX-mediated inhibition was also blocked by pep2-SVKI (SVKI), a synthetic peptide that prevents internalization of AMPA-type glutamate receptor. AMPA itself also inhibited electrical synaptic transmission and this AMPA-mediated inhibition was partially blocked by Con A, DIP and SVKI. Low frequency stimulation induced long-term depression (LTD) in both the electrical and glutamatergic components of these synapses and this LTD was blocked by SVKI. GYKI 52466, a selective non-competitive antagonist of AMPA receptors, did not affect the electrical EPSP, although it did block the glutamatergic component of these synapses. CNQX did not affect non-rectifying electrical synapses in two different pairs of neurons. These results suggest an interaction between AMPA-type glutamate receptors and the gap junction proteins that mediate electrical synaptic transmission. This putative interaction between glutamate receptors and gap junction proteins represents a novel mechanism for regulating the strength of synaptic transmission.
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Affiliation(s)
- Qin Li
- Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
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182
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Abstract
BACKGROUND Palonosetron is a 5-HT(3)-receptor antagonist (5-HT(3)-RA) that has been shown to be superior to other 5-HT(3)-RAs in phase III clinical trials for the prevention of acute, delayed, and overall chemotherapy-induced nausea and vomiting. The improved clinical efficacy of palonosetron may be due, in part, to its more potent binding and longer half-life. However, these attributes alone are not sufficient to explain the results with palonosetron. We sought to elucidate additional differences among 5-HT(3)-RAs that could help explain the observations in the clinic. METHODS Receptor site saturation binding experiments were performed with [3H] palonosetron, [3H] granisetron, and [3H] ondansetron to obtain the corresponding Scatchard analyses and Hill coefficients. Diagnostic equilibrium binding experiments and kinetic dissociation experiments were conducted to examine competitive versus potential allosteric interactions between ondansetron, granisetron and palonosetron and the 5-HT(3) receptor. Finally, the long-term effect of the three antagonists on receptor function as measured by Ca2+ influx in HEK 293 cells expressing the 5-HT(3)-receptor was compared. RESULTS Analyses of binding isotherms using both Scatchard and Hill plots suggested positive cooperativity for palonosetron and simple bimolecular binding for both granisetron and ondansetron. Equilibrium diagnostic tests discriminated differential effects of palonosetron on [3H] ligand binding indicating that palonosetron was an allosteric antagonist whereas granisetron and ondansetron were competitive antagonists. Using dissociation rate strategies, palonosetron was shown to be an allosteric modifier that accelerated the rate of dissociation from the receptor of both granisetron and ondansetron. Differences in the binding mode of palonosetron to the 5-HT(3) receptor were shown to have an impact on receptor function. In these experiments, cells were incubated with each antagonist, followed by infinite dilutions and dissociation for 2.5 h; cells previously incubated with either granisetron or ondansetron showed calcium-ion influx similar to control cells that had not been exposed to a 5-HT(3) receptor antagonist. In contrast, substantial inhibition of calcium-ion influx was observed in cells that had been incubated with palonosetron. CONCLUSIONS Palonosetron exhibited allosteric binding and positive cooperativity when binding to the 5-HT(3) receptor. Palonosetron also triggered functional effects that persisted beyond its binding to the 5-HT(3) receptor at the cell surface. Differences in binding and effects on receptor function may be relevant to the unique beneficial actions of palonosetron. To our knowledge, this is the first report showing palonosetron's interaction with the 5-HT(3) receptor at the molecular level, clearly differentiating it from other 5-HT(3)-RAs.
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183
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The Rab5 guanylate exchange factor Rin1 regulates endocytosis of the EphA4 receptor in mature excitatory neurons. Proc Natl Acad Sci U S A 2008; 105:12539-44. [PMID: 18723684 DOI: 10.1073/pnas.0801174105] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ephrin signaling through Eph receptor tyrosine kinases regulates important morphogenetic events during development and synaptic plasticity in the adult brain. Although Eph-ephrin endocytosis is required for repulsive axon guidance, its role in postnatal brain and synaptic plasticity is unknown. Here, we show that Rin1, a postnatal brain-specific Rab5-GEF, is coexpressed with EphA4 in excitatory neurons and interacts with EphA4 in synaptosomal fractions. The interaction of Rin1 and EphA4 requires Rin1's SH2 domain, consistent with the view that Rin1 targets tyrosine phosphorylated receptors to Rab5 compartments. We find that Rin1 mediates EphA4 endocytosis in postnatal amygdala neurons after engagement of EphA4 with its cognate ligand ephrinB3. Rin1 was shown to suppress synaptic plasticity in the amygdala, a forebrain structure important for fear learning, possibly by internalizing synaptic receptors. We find that the EphA4 receptor is required for synaptic plasticity in the amygdala, raising the possibility that an underlying mechanism of Rin1 function in amygdala is to down-regulate EphA4 signaling by promoting its endocytosis.
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184
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Lu Y, Zhang M, Lim IA, Hall DD, Allen M, Medvedeva Y, McKnight GS, Usachev YM, Hell JW. AKAP150-anchored PKA activity is important for LTD during its induction phase. J Physiol 2008; 586:4155-64. [PMID: 18617570 DOI: 10.1113/jphysiol.2008.151662] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Protein kinase A (PKA) is thought to tonically maintain an enhanced level of postsynaptic AMPA receptor responses. Injection of PKA inhibitory peptides leads to a run-down of AMPA receptor responses and prevents long-term depression (LTD). This run-down of AMPA receptor activity was proposed to occlude a further reduction that would otherwise constitute LTD. PKA is recruited to postsynaptic sites by the A kinase anchor protein AKAP150. We found that LTD was strongly impaired in acute hippocampal slices from 2-week-old mice in which the PKA binding site on AKAP150 had been genetically deleted (D36 mice). However, basal postsynaptic AMPA and NMDA receptor activity was indistinguishable between D36 and WT mice. During extracellular recordings of field EPSPs and during intracellular recording of EPSCs from hippocampal slices from WT mice, H-89 and KT5720, two structurally different PKA inhibitors, inhibited LTD by more than 70% without affecting basal synaptic transmission or basal phosphorylation of serine 845 on GluR1. Collectively our data indicate that AKAP150-anchored PKA activity is required to induce LTD and not merely to maintain a tonically heightened activity level of AMPA receptors as proposed earlier.
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Affiliation(s)
- Yuan Lu
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, IA 52242-1109, USA
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185
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Waung MW, Pfeiffer BE, Nosyreva ED, Ronesi JA, Huber KM. Rapid translation of Arc/Arg3.1 selectively mediates mGluR-dependent LTD through persistent increases in AMPAR endocytosis rate. Neuron 2008; 59:84-97. [PMID: 18614031 PMCID: PMC2580055 DOI: 10.1016/j.neuron.2008.05.014] [Citation(s) in RCA: 392] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 04/04/2008] [Accepted: 05/15/2008] [Indexed: 10/21/2022]
Abstract
Salient stimuli that modify behavior induce transcription of activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) and transport Arc mRNA into dendrites, suggesting that local Arc translation mediates synaptic plasticity that encodes such stimuli. Here, we demonstrate that long-term synaptic depression (LTD) in hippocampal neurons induced by group 1 metabotropic glutamate receptors (mGluRs) relies on rapid translation of Arc. mGluR-LTD induction causes long-term increases in AMPA receptor endocytosis rate and dendritic synthesis of Arc, a component of the AMPAR endocytosis machinery. Knockdown of Arc prevents mGluRs from triggering AMPAR endocytosis or LTD, and acute blockade of new Arc synthesis with antisense oligonucleotides blocks mGluR-LTD and AMPAR trafficking. In contrast, LTD induced by NMDA receptors does not persistently alter AMPAR endocytosis rate, induce Arc synthesis, or require Arc protein. These data demonstrate a role for local Arc synthesis specifically in mGluR-LTD and suggest that mGluR-LTD may be one consequence of Arc mRNA induction during experience.
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Affiliation(s)
- Maggie W Waung
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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186
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Yu SY, Wu DC, Liu L, Ge Y, Wang YT. Role of AMPA receptor trafficking in NMDA receptor-dependent synaptic plasticity in the rat lateral amygdala. J Neurochem 2008; 106:889-99. [DOI: 10.1111/j.1471-4159.2008.05461.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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187
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Cingolani LA, Thalhammer A, Yu LMY, Catalano M, Ramos T, Colicos MA, Goda Y. Activity-dependent regulation of synaptic AMPA receptor composition and abundance by beta3 integrins. Neuron 2008; 58:749-62. [PMID: 18549786 PMCID: PMC2446609 DOI: 10.1016/j.neuron.2008.04.011] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 01/15/2008] [Accepted: 04/09/2008] [Indexed: 11/21/2022]
Abstract
At synapses, cell adhesion molecules (CAMs) provide the molecular framework for coordinating signaling events across the synaptic cleft. Among synaptic CAMs, the integrins, receptors for extracellular matrix proteins and counterreceptors on adjacent cells, are implicated in synapse maturation and plasticity and memory formation. However, little is known about the molecular mechanisms of integrin action at central synapses. Here, we report that postsynaptic beta3 integrins control synaptic strength by regulating AMPA receptors (AMPARs) in a subunit-specific manner. Pharmacological perturbation targeting beta3 integrins promotes endocytosis of GluR2-containing AMPARs via Rap1 signaling, and expression of beta3 integrins produces robust changes in the abundance and composition of synaptic AMPARs without affecting dendritic spine structure. Importantly, homeostatic synaptic scaling induced by activity deprivation elevates surface expression of beta3 integrins, and in turn, beta3 integrins are required for synaptic scaling. Our findings demonstrate a key role for integrins in the feedback regulation of excitatory synaptic strength.
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Affiliation(s)
- Lorenzo A. Cingolani
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, UCL, Gower Street, London, WC1E 6BT, UK
| | | | - Lily M. Y. Yu
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, UCL, Gower Street, London, WC1E 6BT, UK
- Department of Neuroscience, Physiology & Pharmacology, UCL, Gower Street, London, WC1E 6BT, UK
| | - Myriam Catalano
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, UCL, Gower Street, London, WC1E 6BT, UK
| | - Timothy Ramos
- Department of Physiology & Biophysics, Hotchkiss Brain Institute, University of Calgary, Alberta T2N 4N1, Canada
| | - Michael A. Colicos
- Department of Physiology & Biophysics, Hotchkiss Brain Institute, University of Calgary, Alberta T2N 4N1, Canada
| | - Yukiko Goda
- MRC Laboratory for Molecular Cell Biology and Cell Biology Unit, UCL, Gower Street, London, WC1E 6BT, UK
- Department of Neuroscience, Physiology & Pharmacology, UCL, Gower Street, London, WC1E 6BT, UK
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188
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States BA, Khatri L, Ziff EB. Stable synaptic retention of serine-880-phosphorylated GluR2 in hippocampal neurons. Mol Cell Neurosci 2008; 38:189-202. [PMID: 18417360 PMCID: PMC2653623 DOI: 10.1016/j.mcn.2008.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 12/19/2007] [Accepted: 02/14/2008] [Indexed: 01/22/2023] Open
Abstract
Phosphorylation of S880 within the GluR2 C-terminus has been reported to promote endocytosis of AMPA receptors (AMPARs) by preventing GluR2 interaction with the putative synaptic anchoring proteins GRIP and ABP. It is not yet established however, whether S880 phosphorylation induces removal of AMPARs from synaptic sites, and the trafficking of phosphorylated GluR2 subunits with surface and endocytosed GluR2 has not been directly compared within the same intact neurons. Here we show that phosphorylation of GluR2 subunits by PKC activated with phorbol esters is compartmentally restricted to receptors located at the cell surface. Endogenous AMPARs containing S880-phosphorylated GluR2 remained highly synaptic and colocalized with postsynaptic markers to the same extent as AMPARs which did not contain S880-phosphorylated GluR2. Moreover, following S880 phosphorylation, exogenous GluR2 homomers were found specifically at the cell surface and did not co-traffic with the internalized endosomal GluR2 population. We also show that GluR2 is endogenously phosphorylated by a constitutively active kinase pharmacologically related to PKC, and this phosphorylation is opposed by the protein phosphatase PP1. Our results demonstrate a population of hippocampal AMPARs which do not require interaction with GRIP/ABP for synaptic anchorage.
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189
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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: 283] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [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.
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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
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190
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Chun DK, McEwen JM, Burbea M, Kaplan JM. UNC-108/Rab2 regulates postendocytic trafficking in Caenorhabditis elegans. Mol Biol Cell 2008; 19:2682-95. [PMID: 18434599 DOI: 10.1091/mbc.e07-11-1120] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
After endocytosis, membrane proteins are often sorted between two alternative pathways: a recycling pathway and a degradation pathway. Relatively little is known about how trafficking through these alternative pathways is differentially regulated. Here, we identify UNC-108/Rab2 as a regulator of postendocytic trafficking in both neurons and coelomocytes. Mutations in the Caenorhabditis elegans Rab2 gene unc-108, caused the green fluorescent protein (GFP)-tagged glutamate receptor GLR-1 (GLR-1::GFP) to accumulate in the ventral cord and in neuronal cell bodies. In neuronal cell bodies of unc-108/Rab2 mutants, GLR-1::GFP was found in tubulovesicular structures that colocalized with markers for early and recycling endosomes, including Syntaxin-13 and Rab8. GFP-tagged Syntaxin-13 also accumulated in the ventral cord of unc-108/Rab2 mutants. UNC-108/Rab2 was not required for ubiquitin-mediated sorting of GLR-1::GFP into the multivesicular body (MVB) degradation pathway. Mutations disrupting the MVB pathway and unc-108/Rab2 mutations had additive effects on GLR-1::GFP levels in the ventral cord. In coelomocytes, postendocytic trafficking of the marker Texas Red-bovine serum albumin was delayed. These results demonstrate that UNC-108/Rab2 regulates postendocytic trafficking, most likely at the level of early or recycling endosomes, and that UNC-108/Rab2 and the MVB pathway define alternative postendocytic trafficking mechanisms that operate in parallel. These results define a new function for Rab2 in protein trafficking.
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Affiliation(s)
- Denise K Chun
- Department of Molecular Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston MA 02114, USA
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191
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Earnshaw BA, Bressloff PC. Modeling the role of lateral membrane diffusion in AMPA receptor trafficking along a spiny dendrite. J Comput Neurosci 2008; 25:366-89. [PMID: 18320299 DOI: 10.1007/s10827-008-0084-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 01/02/2008] [Accepted: 02/01/2008] [Indexed: 11/28/2022]
Abstract
AMPA receptor trafficking in dendritic spines is emerging as a major postsynaptic mechanism for the expression of plasticity at glutamatergic synapses. AMPA receptors within a spine are in a continuous state of flux, being exchanged with local intracellular pools via exo/endocytosis and with the surrounding dendrite via lateral membrane diffusion. This suggests that one cannot treat a single spine in isolation. Here we present a model of AMPA receptor trafficking between multiple dendritic spines distributed along the surface of a dendrite. Receptors undergo lateral diffusion within the dendritic membrane, with each spine acting as a spatially localized trap where receptors can bind to scaffolding proteins or be internalized through endocytosis. Exocytosis of receptors occurs either at the soma or at sites local to dendritic spines via constitutive recycling from intracellular pools. We derive a reaction-diffusion equation for receptor trafficking that takes into account these various processes. Solutions of this equation allow us to calculate the distribution of synaptic receptor numbers across the population of spines, and hence determine how lateral diffusion contributes to the strength of a synapse. A number of specific results follow from our modeling and analysis. (1) Lateral membrane diffusion alone is insufficient as a mechanism for delivering AMPA receptors from the soma to distal dendrites. (2) A source of surface receptors at the soma tends to generate an exponential-like distribution of receptors along the dendrite, which has implications for synaptic democracy. (3) Diffusion mediates a heterosynaptic interaction between spines so that local changes in the constitutive recycling of AMPA receptors induce nonlocal changes in synaptic strength. On the other hand, structural changes in a spine following long term potentiation or depression have a purely local effect on synaptic strength. (4) A global change in the rates of AMPA receptor exo/endocytosis is unlikely to be the sole mechanism for homeostatic synaptic scaling. (5) The dynamics of AMPA receptor trafficking occurs on multiple timescales and varies according to spatial location along the dendrite. Understanding such dynamics is important when interpreting data from inactivation experiments that are used to infer the rate of relaxation to steady-state.
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Affiliation(s)
- B A Earnshaw
- Department of Mathematics, University of Utah, Salt Lake City, UT 84112, USA
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192
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Sierra-Paredes G, Sierra-Marcuño G. Ascomycin and FK506: Pharmacology and Therapeutic Potential as Anticonvulsants and Neuroprotectants. CNS Neurosci Ther 2008. [DOI: 10.1111/j.1755-5949.2008.00036.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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193
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Fernández de Sevilla D, Núñez A, Borde M, Malinow R, Buño W. Cholinergic-mediated IP3-receptor activation induces long-lasting synaptic enhancement in CA1 pyramidal neurons. J Neurosci 2008; 28:1469-78. [PMID: 18256268 PMCID: PMC6671582 DOI: 10.1523/jneurosci.2723-07.2008] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Revised: 12/11/2007] [Accepted: 12/21/2007] [Indexed: 11/21/2022] Open
Abstract
Cholinergic-glutamatergic interactions influence forms of synaptic plasticity that are thought to mediate memory and learning. We tested in vitro the induction of long-lasting synaptic enhancement at Schaffer collaterals by acetylcholine (ACh) at the apical dendrite of CA1 pyramidal neurons and in vivo by stimulation of cholinergic afferents. In vitro ACh induced a Ca2+ wave and synaptic enhancement mediated by insertion of AMPA receptors in spines. Activation of muscarinic ACh receptors (mAChRs) and Ca2+ release from inositol 1,4,5-trisphosphate (IP3)-sensitive stores were required for this synaptic enhancement that was insensitive to blockade of NMDA receptors and also triggered by IP3 uncaging. Activation of cholinergic afferents in vivo induced an analogous atropine-sensitive synaptic enhancement. We describe a novel form of synaptic enhancement (LTP(IP3)) that is induced in vitro and in vivo by activation of mAChRs. We conclude that Ca2+ released from postsynaptic endoplasmic reticulum stores is the critical event in the induction of this unique form of long-lasting synaptic enhancement.
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194
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Popov VI, Medvedev NI, Kraev IV, Gabbott PL, Davies HA, Lynch M, Cowley TR, Berezin V, Bock E, Stewart MG. A cell adhesion molecule mimetic, FGL peptide, induces alterations in synapse and dendritic spine structure in the dentate gyrus of aged rats: a three-dimensional ultrastructural study. Eur J Neurosci 2008; 27:301-14. [DOI: 10.1111/j.1460-9568.2007.06004.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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195
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Abstract
Experiences, whether they be learning in a classroom, a stressful event, or ingestion of a psychoactive substance, impact the brain by modifying the activity and organization of specific neural circuitry. A major mechanism by which the neural activity generated by an experience modifies brain function is via modifications of synaptic transmission; that is, synaptic plasticity. Here, we review current understanding of the mechanisms of the major forms of synaptic plasticity at excitatory synapses in the mammalian brain. We also provide examples of the possible developmental and behavioral functions of synaptic plasticity and how maladaptive synaptic plasticity may contribute to neuropsychiatric disorders.
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Affiliation(s)
- Ami Citri
- Department of Psychiatry and Behavioral Sciences, Nancy Pritzker Laboratory, Stanford University School of Medicine, Palo Alto, CA 94304-5485, USA
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196
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Sierra-Paredes G, Sierra-Marcuño G. Ascomycin and FK506: pharmacology and therapeutic potential as anticonvulsants and neuroprotectants. CNS Neurosci Ther 2008; 14:36-46. [PMID: 18482098 PMCID: PMC6494028 DOI: 10.1111/j.1527-3458.2008.00036.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Ascomycin and FK506 are powerful calcium-dependent serine/threonine protein phosphatase (calcineurin [CaN], protein phosphatase 2B) inhibitors. Their mechanism of action involves the formation of a molecular complex with the intracellular FK506-binding protein-12 (FKBP12), thereby acquiring the ability to interact with CaN and to interfere with the dephosphorylation of various substrates. Pharmacological studies of ascomycin, FK506, and derivatives have mainly been focused on their action as immunosuppressants and therapeutic use in inflammatory skin diseases, both in animal studies and in humans. CaN inhibitors have been also proposed for the treatment of inflammatory and degenerative brain diseases. Preclinical studies suggest, however, that ascomycin and its derivatives exhibit additional pharmacological activities. Ascomycin has been shown to have anticonvulsant activity when perfused into the rat hippocampus via microdialysis probes, and ascomycin derivatives may be useful in preventing ischemic brain damage and neuronal death. Their pharmacological action in the brain may involve CaN-mediated regulation of gamma aminobutyric acid (GABA) and glutamate receptor channels, neuronal cytoskeleton and dendritic spine morphology, as well as of the inflammatory responses in glial cells. FK506 and ascomycin inhibit signaling pathways in astrocytes and change the pattern of cytokine and neurotrophin gene expression. However, brain-specific mechanisms of action other than CaN inhibition cannot be excluded. CaN is a likely potential target molecule in the treatment of central nervous system (CNS) diseases, so that the therapeutic potential of ascomycin, FK506, and nonimmunosuppressant ascomycin derivatives as CNS drugs should be further explored.
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Affiliation(s)
- Germán Sierra-Paredes
- Neuroscience Division, Department of Biochemistry and Molecular Biology, School of Medicine, University of Santiago, San Francisco 1, Santiago de Compostela, Spain.
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197
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Abstract
The cellular processes that govern neuronal function are highly complex, with many basic cell biological pathways uniquely adapted to perform the elaborate information processing achieved by the brain. This is particularly evident in the trafficking and regulation of membrane proteins to and from synapses, which can be a long distance away from the cell body and number in the thousands. The regulation of neurotransmitter receptors, such as the AMPA-type glutamate receptors (AMPARs), the major excitatory neurotransmitter receptors in the brain, is a crucial mechanism for the modulation of synaptic transmission. The levels of AMPARs at synapses are very dynamic, and it is these plastic changes in synaptic function that are thought to underlie information storage in the brain. Thus, understanding the cellular machinery that controls AMPAR trafficking will be critical for understanding the cellular basis of behavior as well as many neurological diseases. Here we describe the life cycle of AMPARs, from their biogenesis, through their journey to the synapse, and ultimately through their demise, and discuss how the modulation of this process is essential for brain function.
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Affiliation(s)
- Jason D Shepherd
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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198
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Independent expression of synaptic and morphological plasticity associated with long-term depression. J Neurosci 2007; 27:12419-29. [PMID: 17989307 DOI: 10.1523/jneurosci.2015-07.2007] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Physiological and morphological alterations occur with long-term synaptic modifications, such as long-term potentiation (LTP) and long-term depression (LTD), but whether these two processes are independent or interactive is unclear. It is also unknown whether or how morphological modifications, like spine remodeling, may contribute to physiological modifications, such as trafficking of glutamate receptors which underlies, at least partially, the expression of LTP and LTD. In this study, we monitored spine size and synaptic responses simultaneously using combined two photon time-lapse imaging with patch-clamp recording in acute hippocampal slices. We show that spine shrinkage and LTD can occur independently of each other. We further show that changes in spine size are unrelated to trafficking of AMPA receptors (AMPARs) under various conditions: constitutive trafficking of AMPARs, insulin-induced internalization of AMPARs, or lateral movement of AMPARs to extrasynaptic sites. Induction of LTD of NMDA receptor-mediated responses (NMDAR-LTD) is associated with spine shrinkage. Nonetheless, NMDAR-LTD and spine shrinkage diverge in the downstream signaling events, and can occur independently of each other. Thus, spine shrinkage is not caused by or required for trafficking of glutamate receptors. In a broader sense, there is a clear dissociation between physiological and morphological expression of LTD. However, inhibition of actin depolymerization blocked the expression of LTD, suggesting that morphologically silent actin remodeling may be involved in the physiological expression of LTD and different subpopulations of actin filaments undergo changes during LTD.
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199
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Wang YT. Probing the role of AMPAR endocytosis and long-term depression in behavioural sensitization: relevance to treatment of brain disorders, including drug addiction. Br J Pharmacol 2007; 153 Suppl 1:S389-95. [PMID: 18059315 DOI: 10.1038/sj.bjp.0707616] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Modifying the function of postsynaptic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid subtype glutamate receptors (AMPARs) is one of the most important mechanisms by which the efficacy of synaptic transmission at excitatory glutamatergic synapses in the mammalian brain is regulated. Traditionally these types of modifications have been thought to be achieved mainly by altering the channel gating properties or conductance of the receptors. A large body of evidence accumulated from recent studies strongly suggests that AMPARs, like most integral plasma membrane proteins, are continuously recycled between the plasma membrane and the intracellular compartments via vesicle-mediated plasma membrane insertion and clathrin-dependent endocytosis. Regulation of either receptor insertion or endocytosis results in a rapid change in the number of these receptors expressed on the plasma membrane surface and in the receptor-mediated responses, thereby playing an important role in mediating certain forms of synaptic plasticity, such as long-term potentiation (LTP) and depression (LTD). These studies have significantly advanced our understanding of the molecular mechanisms underlying LTP and LTD, and their potential contributions to learning and memory-related behaviours. Here I provide a brief summary of the current state of knowledge concerning clathrin-mediated AMPAR endocytosis and its relationship to the expression of certain forms of LTD in several brain areas. The potential impact of recent advancements on our efforts to probe the roles of synaptic plasticity in learning and memory-related behaviours, and their relevance to some brain disorders, particularly drug addiction, are also discussed.
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Affiliation(s)
- Y T Wang
- Department of Medicine and Brain Research Centre, University of British Columbia, Vancouver, BC, Canada.
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200
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Yudowski GA, Puthenveedu MA, Leonoudakis D, Panicker S, Thorn KS, Beattie EC, von Zastrow M. Real-time imaging of discrete exocytic events mediating surface delivery of AMPA receptors. J Neurosci 2007; 27:11112-21. [PMID: 17928453 PMCID: PMC3249441 DOI: 10.1523/jneurosci.2465-07.2007] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 08/23/2007] [Accepted: 08/26/2007] [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.
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Affiliation(s)
| | | | - Dmitri Leonoudakis
- California Pacific Medical Center Research Institute, San Francisco, California 94107
| | | | - Kurt S. Thorn
- Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94158, and
| | - Eric C. Beattie
- California Pacific Medical Center Research Institute, San Francisco, California 94107
| | - Mark von Zastrow
- Departments of Psychiatry
- Cellular and Molecular Pharmacology, and
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