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Control of Synapse Structure and Function by Actin and Its Regulators. Cells 2022; 11:cells11040603. [PMID: 35203254 PMCID: PMC8869895 DOI: 10.3390/cells11040603] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 01/30/2022] [Accepted: 02/06/2022] [Indexed: 02/07/2023] Open
Abstract
Neurons transmit and receive information at specialized junctions called synapses. Excitatory synapses form at the junction between a presynaptic axon terminal and a postsynaptic dendritic spine. Supporting the shape and function of these junctions is a complex network of actin filaments and its regulators. Advances in microscopic techniques have enabled studies of the organization of actin at synapses and its dynamic regulation. In addition to highlighting recent advances in the field, we will provide a brief historical perspective of the understanding of synaptic actin at the synapse. We will also highlight key neuronal functions regulated by actin, including organization of proteins in the pre- and post- synaptic compartments and endocytosis of ion channels. We review the evidence that synapses contain distinct actin pools that differ in their localization and dynamic behaviors and discuss key functions for these actin pools. Finally, whole exome sequencing of humans with neurodevelopmental and psychiatric disorders has identified synaptic actin regulators as key disease risk genes. We briefly summarize how genetic variants in these genes impact neurotransmission via their impact on synaptic actin.
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Chen J, Liu C, Xu M, Zhu J, Xia Z. Upregulation of miR-19b-3p exacerbates chronic stress-induced changes in synaptic plasticity and cognition by targeting Drebrin. Neuropharmacology 2022; 207:108951. [PMID: 35041806 DOI: 10.1016/j.neuropharm.2022.108951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 12/09/2021] [Accepted: 01/12/2022] [Indexed: 11/20/2022]
Abstract
Chronic stress is associate with impairment of synapse plasticity in hippocampus and cognitive dysfunction in rodent and human. Notably, corticosterone (CORT) is believed to take responsible for dendritic atrophy and reduction of spine number induced by chronic stress in hippocampus. But little is known about the molecular mechanisms underlying CORT induced abnormal synapse plasticity and cognitive dysfunction. Drebrin is an F-actin binding protein that modulates memory formation and maintenance by controlling the genesis and morphology of dendritic spines. In addition, miRNAs have been reported to participate in the negative regulation of protein-coding genes. In this study, five miRNAs capable of targeting Drebrin were selected by searching miRNA databases. One of these miRNAs, miR-19b-3p, was found to be upregulated in the hippocampal neurons of mice with chronic restraint stress (CRS). Luciferase reporter assay and Fluorescence in situ hybridization (FISH) were employed to identified the interaction between miR-19b-3p and Drebrin. In addition, silencing miR-19b-3p expression in vivo using an antagomir or in vitro using an inhibitor increased Drebrin expression, ameliorated the abnormal dendritic structure and upregulated the spine density in hippocampal CA1 pyramidal neurons of CRS mice and primary hippocampal neurons cultured under CORT stimulation, respectively. Electrophysiological analysis revealed that inhibition of miR-19b-3p rescued the limited synaptic transmission and synaptic plasticity in hippocampal neurons. Moreover, blocking miR-19b-3p drastically protected against cognitive deficits in CRS mice. These in vivo and in vitro findings indicate that the upregulation of miR-19b-3p exacerbates CRS-induced abnormal synaptic plasticity and cognitive impairment by targeting Drebrin.
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Affiliation(s)
- Jingli Chen
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, 430060, Hubei, China; Department of Anesthesiology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China
| | - Chang Liu
- Department of Anesthesiology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China; Key Laboratory for Molecular Diagnosis of Hubei Province, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China
| | - Mu Xu
- Department of Anesthesiology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China; Key Laboratory for Molecular Diagnosis of Hubei Province, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China
| | - Jiaxi Zhu
- Department of Anesthesiology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China; Key Laboratory for Molecular Diagnosis of Hubei Province, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430014, Hubei, China
| | - Zhongyuan Xia
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, 430060, Hubei, China.
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Alvarez-Suarez P, Nowak N, Protasiuk-Filipunas A, Yamazaki H, Prószyński TJ, Gawor M. Drebrin Regulates Acetylcholine Receptor Clustering and Organization of Microtubules at the Postsynaptic Machinery. Int J Mol Sci 2021; 22:9387. [PMID: 34502296 PMCID: PMC8430516 DOI: 10.3390/ijms22179387] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/20/2021] [Accepted: 08/24/2021] [Indexed: 01/07/2023] Open
Abstract
Proper muscle function depends on the neuromuscular junctions (NMJs), which mature postnatally to complex "pretzel-like" structures, allowing for effective synaptic transmission. Postsynaptic acetylcholine receptors (AChRs) at NMJs are anchored in the actin cytoskeleton and clustered by the scaffold protein rapsyn, recruiting various actin-organizing proteins. Mechanisms driving the maturation of the postsynaptic machinery and regulating rapsyn interactions with the cytoskeleton are still poorly understood. Drebrin is an actin and microtubule cross-linker essential for the functioning of the synapses in the brain, but its role at NMJs remains elusive. We used immunohistochemistry, RNA interference, drebrin inhibitor 3,5-bis-trifluoromethyl pyrazole (BTP2) and co-immunopreciptation to explore the role of this protein at the postsynaptic machinery. We identify drebrin as a postsynaptic protein colocalizing with the AChRs both in vitro and in vivo. We also show that drebrin is enriched at synaptic podosomes. Downregulation of drebrin or blocking its interaction with actin in cultured myotubes impairs the organization of AChR clusters and the cluster-associated microtubule network. Finally, we demonstrate that drebrin interacts with rapsyn and a drebrin interactor, plus-end-tracking protein EB3. Our results reveal an interplay between drebrin and cluster-stabilizing machinery involving rapsyn, actin cytoskeleton, and microtubules.
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Affiliation(s)
- Paloma Alvarez-Suarez
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland; (P.A.-S.); (N.N.); (A.P.-F.); (T.J.P.)
| | - Natalia Nowak
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland; (P.A.-S.); (N.N.); (A.P.-F.); (T.J.P.)
| | - Anna Protasiuk-Filipunas
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland; (P.A.-S.); (N.N.); (A.P.-F.); (T.J.P.)
| | - Hiroyuki Yamazaki
- Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan;
| | - Tomasz J. Prószyński
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland; (P.A.-S.); (N.N.); (A.P.-F.); (T.J.P.)
| | - Marta Gawor
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, 02-093 Warsaw, Poland; (P.A.-S.); (N.N.); (A.P.-F.); (T.J.P.)
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4
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Yamazaki H, Sasagawa Y, Yamamoto H, Bito H, Shirao T. CaMKIIβ is localized in dendritic spines as both drebrin-dependent and drebrin-independent pools. J Neurochem 2018; 146:145-159. [PMID: 29675826 PMCID: PMC6099455 DOI: 10.1111/jnc.14449] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 03/14/2018] [Accepted: 04/04/2018] [Indexed: 12/21/2022]
Abstract
Drebrin is a major F-actin binding protein in dendritic spines that is critically involved in the regulation of dendritic spine morphogenesis, pathology, and plasticity. In this study, we aimed to identify a novel drebrin-binding protein involved in spine morphogenesis and synaptic plasticity. We confirmed the beta subunit of Ca2+ /calmodulin-dependent protein kinase II (CaMKIIβ) as a drebrin-binding protein using a yeast two-hybrid system, and investigated the drebrin-CaMKIIβ relationship in dendritic spines using rat hippocampal neurons. Drebrin knockdown resulted in diffuse localization of CaMKIIβ in dendrites during the resting state, suggesting that drebrin is involved in the accumulation of CaMKIIβ in dendritic spines. Fluorescence recovery after photobleaching analysis showed that drebrin knockdown increased the stable fraction of CaMKIIβ, indicating the presence of drebrin-independent, more stable CaMKIIβ. NMDA receptor activation also increased the stable fraction in parallel with drebrin exodus from dendritic spines. These findings suggest that CaMKIIβ can be classified into distinct pools: CaMKIIβ associated with drebrin, CaMKIIβ associated with post-synaptic density (PSD), and CaMKIIβ free from PSD and drebrin. CaMKIIβ appears to be anchored to a protein complex composed of drebrin-binding F-actin during the resting state. NMDA receptor activation releases CaMKIIβ from drebrin resulting in CaMKIIβ association with PSD.
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Affiliation(s)
- Hiroyuki Yamazaki
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Yoshio Sasagawa
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
| | - Hideyuki Yamamoto
- Department of Biochemistry, Graduate School of Medicine, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Haruhiko Bito
- Department of Neurochemistry, The University of Tokyo Graduate School of Medicine, Tokyo, Japan
| | - Tomoaki Shirao
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
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Willmes CG, Mack TGA, Ledderose J, Schmitz D, Wozny C, Eickholt BJ. Investigation of hippocampal synaptic transmission and plasticity in mice deficient in the actin-binding protein Drebrin. Sci Rep 2017; 7:42652. [PMID: 28198431 PMCID: PMC5309812 DOI: 10.1038/srep42652] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 01/11/2017] [Indexed: 12/22/2022] Open
Abstract
The dynamic regulation of the actin cytoskeleton plays a key role in controlling the structure and function of synapses. It is vital for activity-dependent modulation of synaptic transmission and long-term changes in synaptic morphology associated with memory consolidation. Several regulators of actin dynamics at the synapse have been identified, of which a salient one is the postsynaptic actin stabilising protein Drebrin (DBN). It has been suggested that DBN modulates neurotransmission and changes in dendritic spine morphology associated with synaptic plasticity. Given that a decrease in DBN levels is correlated with cognitive deficits associated with ageing and dementia, it was hypothesised that DBN protein abundance instructs the integrity and function of synapses. We created a novel DBN deficient mouse line. Analysis of gross brain and neuronal morphology revealed no phenotype in the absence of DBN. Electrophysiological recordings in acute hippocampal slices and primary hippocampal neuronal cultures showed that basal synaptic transmission, and both long-term and homeostatic synaptic plasticity were unchanged, suggesting that loss of DBN is not sufficient in inducing synapse dysfunction. We propose that the overall lack of changes in synaptic function and plasticity in DBN deficient mice may indicate robust compensatory mechanisms that safeguard cytoskeleton dynamics at the synapse.
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Affiliation(s)
- Claudia G Willmes
- Institute of Biochemistry, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,NeuroCure - Cluster of Excellence, Charité - Universitätsmedizin Berlin, Germany
| | - Till G A Mack
- Institute of Biochemistry, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Julia Ledderose
- Institute of Biochemistry, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany
| | - Dietmar Schmitz
- NeuroCure - Cluster of Excellence, Charité - Universitätsmedizin Berlin, Germany.,Neuroscience Research Center (NWFZ), Charité Universitätsmedizin, 10117 Berlin, Germany
| | - Christian Wozny
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow, G4 0RE, UK
| | - Britta J Eickholt
- Institute of Biochemistry, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.,NeuroCure - Cluster of Excellence, Charité - Universitätsmedizin Berlin, Germany
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Koganezawa N, Hanamura K, Sekino Y, Shirao T. The role of drebrin in dendritic spines. Mol Cell Neurosci 2017; 84:85-92. [PMID: 28161364 DOI: 10.1016/j.mcn.2017.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 12/06/2016] [Accepted: 01/18/2017] [Indexed: 11/17/2022] Open
Abstract
Dendritic spines form typical excitatory synapses in the brain and their shapes vary depending on synaptic inputs. It has been suggested that the morphological changes of dendritic spines play an important role in synaptic plasticity. Dendritic spines contain a high concentration of actin, which has a central role in supporting cell motility, and polymerization of actin filaments (F-actin) is most likely involved in spine shape changes. Drebrin is an actin-binding protein that forms stable F-actin and is highly accumulated within dendritic spines. Drebrin has two isoforms, embryonic-type drebrin E and adult-type drebrin A, that change during development from E to A. Inhibition of drebrin A expression results in a delay of synapse formation and inhibition of postsynaptic protein accumulation, suggesting that drebrin A has an important role in spine maturation. In mature synapses, glutamate stimulation induces rapid spine-head enlargement during long-term potentiation (LTP) formation. LTP stimulation induces Ca2+ entry through N-methyl-d-aspartate (NMDA) receptors, which causes drebrin exodus from dendritic spines. Once drebrin exits from dendritic spine heads, the dynamic actin pool increases in spine heads to facilitate F-actin polymerization. To maintain enlarged spine heads, drebrin-decorated F-actin is thought to reform within the spine heads. Thus, drebrin plays a pivotal role in spine plasticity through regulation of F-actin.
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Affiliation(s)
- Noriko Koganezawa
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
| | - Kenji Hanamura
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
| | - Yuko Sekino
- Division of Pharmacology, National Institute of Health Sciences, Tokyo 158-8501, Japan
| | - Tomoaki Shirao
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan.
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Homer, Spikar, and Other Drebrin-Binding Proteins in the Brain. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1006:249-268. [PMID: 28865024 DOI: 10.1007/978-4-431-56550-5_14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Drebrin is a major F-actin-binding protein in the brain. In the past two decades, many drebrin-binding proteins in addition to F-actin have been identified in several research fields including neuroscience, oncology, and immunology. Among the drebrin-binding proteins, there are various kinds of proteins including scaffold proteins, nuclear proteins, phosphatases, microtubule-binding proteins, G-actin-binding proteins, gap junction proteins, chemokine receptors, and cell-adhesion-related proteins. The interaction between drebrin and its binding partners seems to play important roles in higher brain functions, because drebrin is involved in the pathogenesis of some neurological diseases with cognitive defects. In this chapter, we will first review the interaction of Homer and spikar with drebrin, particularly focusing on spine morphogenesis and synaptic function. Homer contributes to spine morphogenesis by cooperating with shank and activated Cdc42 small GTPase, suggesting a novel signaling pathway comprising Homer, drebrin, shank, and Cdc42 for spine morphogenesis. Drebrin sequesters spikar in the cytoplasm and stabilizes it in dendritic spines, leading to spine formation. Finally, we will introduce some other drebrin-binding proteins including end-binding protein 3 (EB3), profilin, progranulin, and phosphatase and tensin homologue (PTEN). These proteins are involved in Alzheimer's disease and cancer. Therefore, further studies on drebrin and its binding proteins will be of great importance to elucidate the pathologies of various diseases and may contribute to their medical treatment and diagnostics development.
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Aoki C, Sherpa AD. Making of a Synapse: Recurrent Roles of Drebrin A at Excitatory Synapses Throughout Life. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1006:119-139. [DOI: 10.1007/978-4-431-56550-5_8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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10
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Sekino Y, Koganezawa N, Mizui T, Shirao T. Role of Drebrin in Synaptic Plasticity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1006:183-201. [DOI: 10.1007/978-4-431-56550-5_11] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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11
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12
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Differential Activation of Calpain-1 and Calpain-2 following Kainate-Induced Seizure Activity in Rats and Mice. eNeuro 2016; 3:eN-NWR-0088-15. [PMID: 27622212 PMCID: PMC5011686 DOI: 10.1523/eneuro.0088-15.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 07/30/2016] [Accepted: 08/02/2016] [Indexed: 11/30/2022] Open
Abstract
Systemic injection of kainate produces repetitive seizure activity in both rats and mice. It also results in short-term synaptic modifications as well as delayed neurodegeneration. The signaling cascades involved in both short-term and delayed responses are not clearly defined. The calcium-dependent protease calpain is activated in various brain structures following systemic kainate injection, although the precise involvement of the two major brain calpain isoforms, calpain-1 and calpain-2, remains to be defined. It has recently been reported that calpain-1 and calpain-2 play opposite roles in NMDA receptor-mediated neuroprotection or neurodegeneration, with calpain-1 being neuroprotective and calpain-2 being neurodegenerative. In the present study, we determined the activation pattern of calpain-1 and calpain-2 by analyzing changes in levels of different calpain substrates, including spectrin, drebrin, and PTEN (phosphatase and tensin homolog; a specific calpain-2 substrate) in both rats, and wild-type and calpain-1 knock-out mice. The results indicate that, while calpain-2 is rapidly activated in pyramidal cells throughout CA1 and CA3, rapid calpain-1 activation is restricted to parvalbumin-positive and to a lesser extent CCK-positive, but not somatostatin-positive, interneurons. In addition, calpain-1 knock-out mice exhibit increased long-term neurodegeneration in CA1, reinforcing the notion that calpain-1 activation is neuroprotective.
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Jedlicka P, Deller T. Understanding the role of synaptopodin and the spine apparatus in Hebbian synaptic plasticity - New perspectives and the need for computational modeling. Neurobiol Learn Mem 2016; 138:21-30. [PMID: 27470091 DOI: 10.1016/j.nlm.2016.07.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 07/15/2016] [Accepted: 07/23/2016] [Indexed: 12/17/2022]
Abstract
Synaptopodin (SP) is a proline-rich actin-associated protein essential for the formation of a spine apparatus (SA) in dendritic spines. The SA consists of stacks of smooth endoplasmic reticulum (sER) contiguous with the meshwork of somatodendritic ER. Spines of SP-deficient mice contain sER but no SA, demonstrating that SP is necessary for the assembly of ER cisterns into the more complex SA organelle. Although the SA was described decades ago, its function was difficult to investigate and remained elusive, in part because reliable markers for the SA were missing. After SP was identified as an essential component and a reliable marker of the SA, a role of SP/SA in hippocampal synaptic plasticity could be firmly established using loss-of-function approaches. Further studies revealed that SP/SA participate in the regulation of Ca2+-dependent spine-specific Hebbian plasticity and in activity-dependent changes in the spine actin cytoskeleton. In this review we are summarizing recent progress made on SP/SA in Hebbian plasticity and discuss open questions such as causality, spatiotemporal dynamics and complementarity of SP/SA-dependent mechanisms. We are proposing that computational modeling of spine Ca2+-signaling and actin remodeling pathways could address some of these issues and could indicate future research directions. Moreover, reaction-diffusion simulations could help to identify key feedforward and feedback regulatory motifs regulating the switch between an LTP and an LTD signaling module in SP/SA-containing spines, thus helping to find a unified view of SP/SA action in Hebbian plasticity.
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Affiliation(s)
- Peter Jedlicka
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, D-60590 Frankfurt/Main, Germany.
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, D-60590 Frankfurt/Main, Germany.
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14
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Jung G, Kim EJ, Cicvaric A, Sase S, Gröger M, Höger H, Sialana FJ, Berger J, Monje FJ, Lubec G. Drebrin depletion alters neurotransmitter receptor levels in protein complexes, dendritic spine morphogenesis and memory-related synaptic plasticity in the mouse hippocampus. J Neurochem 2015; 134:327-39. [DOI: 10.1111/jnc.13119] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 03/16/2015] [Accepted: 03/27/2015] [Indexed: 12/19/2022]
Affiliation(s)
- Gangsoo Jung
- Department of Pediatrics; Medical University of Vienna; Vienna Austria
| | - Eun-Jung Kim
- Department of Pediatrics; Medical University of Vienna; Vienna Austria
| | - Ana Cicvaric
- Department of Neurophysiology and Neuropharmacology; Center for Physiology and Pharmacology; Medical University of Vienna; Vienna Austria
| | - Sunetra Sase
- Department of Pediatrics; Medical University of Vienna; Vienna Austria
| | - Marion Gröger
- Core Facility Imaging; Medical University of Vienna; Vienna Austria
| | - Harald Höger
- Core Unit of Biomedical Research; Division of Laboratory Animal Science and Genetics; Medical University of Vienna; Himberg Austria
| | | | - Johannes Berger
- Department of Pathobiology of the Nervous System; Center for Brain Research; Medical University of Vienna; Vienna Austria
| | - Francisco J. Monje
- Department of Neurophysiology and Neuropharmacology; Center for Physiology and Pharmacology; Medical University of Vienna; Vienna Austria
| | - Gert Lubec
- Department of Pediatrics; Medical University of Vienna; Vienna Austria
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15
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Abstract
The ability to induce and study neuronal plasticity in single dendritic spines has greatly advanced our understanding of the signaling mechanisms that mediate long-term potentiation. It is now clear that in addition to compartmentalization by the individual spine, subcompartmentalization of biochemical signals occurs at specialized microdomains within the spine. The spatiotemporal coordination of these complex cascades allows for the concomitant remodeling of the postsynaptic density and actin spinoskeleton and for the regulation of membrane traffic to express functional and structural plasticity. Here, we highlight recent findings in the signaling cascades at spine microdomains as well as the challenges and approaches to studying plasticity at the spine level.
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Affiliation(s)
- Lesley A Colgan
- Neuronal Signal Transduction, Max Planck Florida Institute for Neuroscience, Jupiter, Florida 33458; ,
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16
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Baudry M, Bi X. Learning and memory: an emergent property of cell motility. Neurobiol Learn Mem 2013; 104:64-72. [PMID: 23707799 DOI: 10.1016/j.nlm.2013.04.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 01/24/2023]
Abstract
In this review, we develop the argument that the molecular/cellular mechanisms underlying learning and memory are an adaptation of the mechanisms used by all cells to regulate cell motility. Neuronal plasticity and more specifically synaptic plasticity are widely recognized as the processes by which information is stored in neuronal networks engaged during the acquisition of information. Evidence accumulated over the last 25 years regarding the molecular events underlying synaptic plasticity at excitatory synapses has shown the remarkable convergence between those events and those taking place in cells undergoing migration in response to extracellular signals. We further develop the thesis that the calcium-dependent protease, calpain, which we postulated over 25 years ago to play a critical role in learning and memory, plays a central role in the regulation of both cell motility and synaptic plasticity. The findings discussed in this review illustrate the general principle that fundamental cell biological processes are used for a wide range of functions at the level of organisms.
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Affiliation(s)
- Michel Baudry
- Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA.
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Rácz B, Weinberg RJ. Microdomains in forebrain spines: an ultrastructural perspective. Mol Neurobiol 2013; 47:77-89. [PMID: 22983912 PMCID: PMC3538892 DOI: 10.1007/s12035-012-8345-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Accepted: 08/27/2012] [Indexed: 12/21/2022]
Abstract
Glutamatergic axons in the mammalian forebrain terminate predominantly onto dendritic spines. Long-term changes in the efficacy of these excitatory synapses are tightly coupled to changes in spine morphology. The reorganization of the actin cytoskeleton underlying this spine "morphing" involves numerous proteins that provide the machinery needed for adaptive cytoskeletal remodeling. Here, we review recent literature addressing the chemical architecture of the spine, focusing mainly on actin-binding proteins (ABPs). Accumulating evidence suggests that ABPs are organized into functionally distinct microdomains within the spine cytoplasm. This functional compartmentalization provides a structural basis for regulation of the spinoskeleton, offering a novel window into mechanisms underlying synaptic plasticity.
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Affiliation(s)
- Bence Rácz
- Department of Anatomy and Histology, Faculty of Veterinary Science, Szent István University, 1078, Budapest, Hungary.
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Lee D, Aoki C. Presenilin conditional double knockout mice exhibit decreases in drebrin a at hippocampal CA1 synapses. Synapse 2012; 66:870-9. [PMID: 22715045 DOI: 10.1002/syn.21578] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Accepted: 06/08/2012] [Indexed: 01/09/2023]
Abstract
Presenilin conditional double knockout (PScDKO) mice have been used as animal models to study the development of Alzheimer's disease (AD) phenotypes. Studies to date indicate that these animals exhibit memory dysfunction and decreased synaptic plasticity before the onset of neurodegeneration. Therefore, the current study sought to examine how the loss of presenilin expression leads to these defects. Drebrin A, a neuron-specific actin-binding protein, has been shown to play an important role in the activity-dependent redistribution of the NMDA type of glutamate receptors at the synapse which, in turn, is a critical step for enabling synaptic plasticity. It is hypothesized that defects in the activity dependent redistribution of NMDA receptors in PScDKO mice may be due to loss of drebrin A. In this study, electron microscopic immunocytochemistry (EM-ICC) was used to quantify and locate drebrin A in the CA1 field of the hippocampus of PScDKO mice. The high resolution of EM-ICC allowed for differentiation between drebrin A at the synapse and at nonsynaptic sites, the latter of which would reflect the protein's role in regulating the reserve or degradative pool of NMDA receptors. The results here demonstrate that loss of function of presenilin in mice leads to a decrease in immunoreactivity for drebrin A at both synaptic (54% decrease, P < 0.01) and nonsynaptic areas (40% decrease, P < 0.01) and overall (44% decrease, P < 0.01). The reduction of drebrin A in both synaptic and nonsynaptic locations of the spine may implicate impairment in glutamate receptor trafficking to and from the postsynaptic plasma membrane. In addition, because of reduced drebrin A at nonsynaptic sites, the regulation of the reserve and degradative pools of glutamate receptors may also be impaired, leading to further synaptic dysfunction. Therefore, this study provides evidence to the theory that drebrin A has a causal role in compromising activity-dependent glutamate receptor trafficking in PScDKO mice.
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Affiliation(s)
- David Lee
- Center for Neural Science, New York University, New York 10003, USA
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19
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Harris KM, Weinberg RJ. Ultrastructure of synapses in the mammalian brain. Cold Spring Harb Perspect Biol 2012; 4:cshperspect.a005587. [PMID: 22357909 DOI: 10.1101/cshperspect.a005587] [Citation(s) in RCA: 277] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The morphology and molecular composition of synapses provide the structural basis for synaptic function. This article reviews the electron microscopy of excitatory synapses on dendritic spines, using data from rodent hippocampus, cerebral cortex, and cerebellar cortex. Excitatory synapses have a prominent postsynaptic density, in contrast with inhibitory synapses, which have less dense presynaptic or postsynaptic specializations and are usually found on the cell body or proximal dendritic shaft. Immunogold labeling shows that the presynaptic active zone provides a scaffold for key molecules involved in the release of neurotransmitter, whereas the postsynaptic density contains ligand-gated ionic channels, other receptors, and a complex network of signaling molecules. Delineating the structure and molecular organization of these axospinous synapses represents a crucial step toward understanding the mechanisms that underlie synaptic transmission and the dynamic modulation of neurotransmission associated with short- and long-term synaptic plasticity.
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Affiliation(s)
- Kristen M Harris
- Center for Learning and Memory, Neurobiology Section, University of Texas, Austin, 78712, USA.
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20
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Nwabuisi-Heath E, LaDu MJ, Yu C. Simultaneous analysis of dendritic spine density, morphology and excitatory glutamate receptors during neuron maturation in vitro by quantitative immunocytochemistry. J Neurosci Methods 2012; 207:137-47. [PMID: 22521963 DOI: 10.1016/j.jneumeth.2012.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 03/29/2012] [Accepted: 04/02/2012] [Indexed: 01/20/2023]
Abstract
Alterations in the density and morphology of dendritic spines are characteristic of multiple cognitive disorders. Elucidating the molecular mechanisms underlying spine alterations are facilitated by the use of experimental and analytical methods that permit concurrent evaluation of changes in spine density, morphology and composition. Here, an automated and quantitative immunocytochemical method for the simultaneous analysis of changes in the density and morphology of spines and excitatory glutamate receptors was established to analyze neuron maturation, in vitro. In neurons of long-term neuron-glia co-cultures, spine density as measured by drebrin cluster fluorescence, increased from DIV (days in vitro)10 to DIV18 (formation phase), remained stable from DIV18 to DIV21 (maintenance phase), and decreased from DIV21 to DIV26 (loss phase). The densities of spine-localized NMDAR and AMPAR clusters followed a similar trend. Spine head sizes as measured by the fluorescence intensities of drebrin clusters increased from DIV10 to DIV21 and decreased from DIV21 to DIV26. Changes in the densities of NR1-only, GluR2-only, and NR1+GluR2 spines were measured by the colocalizations of NR1 and GluR2 clusters with drebrin clusters. The densities of NR1-only spines remained stable from the maintenance to the loss phases, while GluR2-only and NR1+GluR2 spines decreased during the loss phase, thus suggesting GluR2 loss as a proximal molecular event that may underlie spine alterations during neuron maturation. This study demonstrates a sensitive and quantitative immunocytochemical method for the concurrent analysis of changes in spine density, morphology and composition, a valuable tool for determining molecular events involved in dendritic spine alterations.
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Affiliation(s)
- Evelyn Nwabuisi-Heath
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL 60612, USA.
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21
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Fortin DA, Srivastava T, Soderling TR. Structural modulation of dendritic spines during synaptic plasticity. Neuroscientist 2011; 18:326-41. [PMID: 21670426 DOI: 10.1177/1073858411407206] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The majority of excitatory synaptic input in the brain is received by small bulbous actin-rich protrusions residing on the dendrites of glutamatergic neurons. These dendritic spines are the major sites of information processing in the brain. This conclusion is reinforced by the observation that many higher cognitive disorders, such as mental retardation, Rett syndrome, and autism, are associated with aberrant spine morphology. Mechanisms that regulate the maturation and plasticity of dendritic spines are therefore fundamental to understanding higher brain functions including learning and memory. It is well known that activity-driven changes in synaptic efficacy modulate spine morphology due to alterations in the underlying actin cytoskeleton. Recent studies have elucidated numerous molecular regulators that directly alter actin dynamics within dendritic spines. This review will emphasize activity-dependent changes in spine morphology and highlight likely roles of these actin-binding proteins.
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Affiliation(s)
- Dale A Fortin
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239, USA.
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22
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Lin YC, Koleske AJ. Mechanisms of synapse and dendrite maintenance and their disruption in psychiatric and neurodegenerative disorders. Annu Rev Neurosci 2011; 33:349-78. [PMID: 20367247 DOI: 10.1146/annurev-neuro-060909-153204] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Emerging evidence indicates that once established, synapses and dendrites can be maintained for long periods, if not for the organism's entire lifetime. In contrast to the wealth of knowledge regarding axon, dendrite, and synapse development, we understand comparatively little about the cellular and molecular mechanisms that enable long-term synapse and dendrite maintenance. Here, we review how the actin cytoskeleton and its regulators, adhesion receptors, and scaffolding proteins mediate synapse and dendrite maintenance. We examine how these mechanisms are reinforced by trophic signals passed between the pre- and postsynaptic compartments. We also discuss how synapse and dendrite maintenance mechanisms are compromised in psychiatric and neurodegenerative disorders.
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Affiliation(s)
- Yu-Chih Lin
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8024, USA.
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Garcia O, Torres M, Helguera P, Coskun P, Busciglio J. A role for thrombospondin-1 deficits in astrocyte-mediated spine and synaptic pathology in Down's syndrome. PLoS One 2010; 5:e14200. [PMID: 21152035 PMCID: PMC2996288 DOI: 10.1371/journal.pone.0014200] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 11/15/2010] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Down's syndrome (DS) is the most common genetic cause of mental retardation. Reduced number and aberrant architecture of dendritic spines are common features of DS neuropathology. However, the mechanisms involved in DS spine alterations are not known. In addition to a relevant role in synapse formation and maintenance, astrocytes can regulate spine dynamics by releasing soluble factors or by physical contact with neurons. We have previously shown impaired mitochondrial function in DS astrocytes leading to metabolic alterations in protein processing and secretion. In this study, we investigated whether deficits in astrocyte function contribute to DS spine pathology. METHODOLOGY/PRINCIPAL FINDINGS Using a human astrocyte/rat hippocampal neuron coculture, we found that DS astrocytes are directly involved in the development of spine malformations and reduced synaptic density. We also show that thrombospondin 1 (TSP-1), an astrocyte-secreted protein, possesses a potent modulatory effect on spine number and morphology, and that both DS brains and DS astrocytes exhibit marked deficits in TSP-1 protein expression. Depletion of TSP-1 from normal astrocytes resulted in dramatic changes in spine morphology, while restoration of TSP-1 levels prevented DS astrocyte-mediated spine and synaptic alterations. Astrocyte cultures derived from TSP-1 KO mice exhibited similar deficits to support spine formation and structure than DS astrocytes. CONCLUSIONS/SIGNIFICANCE These results indicate that human astrocytes promote spine and synapse formation, identify astrocyte dysfunction as a significant factor of spine and synaptic pathology in the DS brain, and provide a mechanistic rationale for the exploration of TSP-1-based therapies to treat spine and synaptic pathology in DS and other neurological conditions.
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Affiliation(s)
- Octavio Garcia
- Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders (iMIND), Center for the Neurobiology of Learning and Memory (CNLM), University of California Irvine, Irvine, California, United States of America
| | - Maria Torres
- Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders (iMIND), Center for the Neurobiology of Learning and Memory (CNLM), University of California Irvine, Irvine, California, United States of America
| | - Pablo Helguera
- Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders (iMIND), Center for the Neurobiology of Learning and Memory (CNLM), University of California Irvine, Irvine, California, United States of America
| | - Pinar Coskun
- Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders (iMIND), Center for the Neurobiology of Learning and Memory (CNLM), University of California Irvine, Irvine, California, United States of America
| | - Jorge Busciglio
- Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders (iMIND), Center for the Neurobiology of Learning and Memory (CNLM), University of California Irvine, Irvine, California, United States of America
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Hanamura K, Mizui T, Kakizaki T, Roppongi R, Yamazaki H, Yanagawa Y, Shirao T. Low accumulation of drebrin at glutamatergic postsynaptic sites on GABAergic neurons. Neuroscience 2010; 169:1489-500. [DOI: 10.1016/j.neuroscience.2010.06.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 06/08/2010] [Accepted: 06/16/2010] [Indexed: 12/20/2022]
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Schulz-Schaeffer WJ. The synaptic pathology of alpha-synuclein aggregation in dementia with Lewy bodies, Parkinson's disease and Parkinson's disease dementia. Acta Neuropathol 2010; 120:131-43. [PMID: 20563819 PMCID: PMC2892607 DOI: 10.1007/s00401-010-0711-0] [Citation(s) in RCA: 411] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2010] [Revised: 05/31/2010] [Accepted: 06/11/2010] [Indexed: 12/16/2022]
Abstract
Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are usually associated with loss of dopaminergic neurons. Loss of substantia nigra neurons and presence of Lewy body inclusions in some of the remaining neurons are the hallmark pathology seen in the final stages of the disease. Attempts to correlate Lewy body pathology to either cell death or severity of clinical symptoms, however, have not been successful. While the pathophysiology of the neurodegenerative process can hardly be explained by Lewy bodies, the clinical symptoms do indicate a degenerative process located at the presynapse resulting in a neurotransmitter deficiency. Recently it was shown that 90% or even more of alpha-synuclein aggregates in DLB cases were located at the presynapses in the form of very small deposits. In parallel, dendritic spines are retracted, whereas the presynapses are relatively preserved, suggesting a neurotransmitter deprivation. The same alpha-synuclein pathology can be demonstrated for PD. These findings give rise to the notion that not cell death but rather alpha-synuclein aggregate-related synaptic dysfunction causes the neurodegeneration. This opens new perspectives for understanding PD and DLB. If presynaptic alpha-synuclein aggregation, not neuronal loss, is the key issue of the neurodegenerative process, then PD and DLB may eventually be treatable in the future. The disease may progress via trans-synaptical spread, suggesting that stem cell transplants are of limited use. Future therapies may focus on the regeneration of synapses.
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Affiliation(s)
- Walter J Schulz-Schaeffer
- Department of Neuropathology, University Medical Center Göttingen, Robert-Koch-Str. 40, Göttingen, Germany.
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26
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Ampuero E, Rubio FJ, Falcon R, Sandoval M, Diaz-Veliz G, Gonzalez RE, Earle N, Dagnino-Subiabre A, Aboitiz F, Orrego F, Wyneken U. Chronic fluoxetine treatment induces structural plasticity and selective changes in glutamate receptor subunits in the rat cerebral cortex. Neuroscience 2010; 169:98-108. [PMID: 20417256 DOI: 10.1016/j.neuroscience.2010.04.035] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 04/14/2010] [Accepted: 04/16/2010] [Indexed: 12/16/2022]
Abstract
It has been postulated that chronic administration of antidepressant drugs induces delayed structural and molecular adaptations at glutamatergic forebrain synapses that might underlie mood improvement. To gain further insight into these changes in the cerebral cortex, rats were treated with fluoxetine (flx) for 4 weeks. These animals showed decreased anxiety and learned helplessness. N-methyl-d-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor subunit levels (NR1, NR2A, NR2B, GluR1 and GluR2) were analysed in the forebrain by both western blot of homogenates and immunohistochemistry. Both methods demonstrated an upregulation of NR2A, GluR1 and GluR2 that was especially significant in the retrosplenial granular b cortex (RSGb). However, when analysing subunit content in postsynaptic densities and synaptic membranes, we found increases of NR2A and GluR2 but not GluR1. Instead, GluR1 was augmented in a microsomal fraction containing intracellular membranes. NR1 and GluR2 were co-immunoprecipitated from postsynaptic densities and synaptic membranes. In the immunoprecipitates, NR2A was increased while GluR1 was decreased supporting a change in receptor stoichiometry. The changes of subunit levels were associated with an upregulation of dendritic spine density and of large, mushroom-type spines. These molecular and structural adaptations might be involved in neuronal network stabilization following long-term flx treatment.
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Affiliation(s)
- E Ampuero
- Laboratorio de Neurociencias, Universidad de los Andes, Santiago, Chile
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27
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Aoki C, Lee J, Nedelescu H, Ahmed T, Ho A, Shen J. Increased levels of NMDA receptor NR2A subunits at pre- and postsynaptic sites of the hippocampal CA1: an early response to conditional double knockout of presenilin 1 and 2. J Comp Neurol 2009; 517:512-23. [PMID: 19795494 DOI: 10.1002/cne.22151] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Greater than 90% of familial Alzheimer's disease (AD) is linked to mutations of presenilin (PS), and the loss of PS function altogether within mouse brains by conditional double knockout of the PS 1 and 2 genes (PS-cDKO) leads to age-dependent emergence of AD phenotypes, including neurodegeneration and reduced synaptic plasticity in the hippocampal CA1. The goal of our study was to identify the ultrastructural and molecular changes at synapses in the hippocampal CA1 of this PS-cDKO mouse model of AD. We examined the asymmetric (excitatory) synapses formed on apical dendrites of CA1 pyramidal neurons at 2 months postnatal, an age when AD-like symptoms emerge but brain morphology, as assessed by light microscopy, is still normal. Our quantitative electron microscopic analyses confirm that PS-cDKO hippocampi at 2 months postnatal do not yet exhibit synapse losses or spine size alterations. However, immunocytochemistry reveals that the same region exhibits a 28% increase in the proportion of spines labeled for the NR2A subunits of NMDA receptors (NMDAR), with a 31% increase specifically at postsynaptic densities and a concomitant reduction of these subunits at nonsynaptic sites within spine heads. In contrast, no change in levels or the distribution pattern of NR2B subunit levels were detected within spine heads. Presynaptically, NR2A levels are elevated at axo-spinous junctions and these may contribute to the timing-dependent, long-term depression. These observations point to an early-onset trapping of NMDAR at synapses that are subtle but may underlie the reduced synaptic plasticity at 2 months of age and excitotoxicity at later stages.
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Affiliation(s)
- Chiye Aoki
- Center for Neural Science, New York University, New York, NY 10003, USA.
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28
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Aoki C, Kojima N, Sabaliauskas N, Shah L, Ahmed TH, Oakford J, Ahmed T, Yamazaki H, Hanamura K, Shirao T. Drebrin a knockout eliminates the rapid form of homeostatic synaptic plasticity at excitatory synapses of intact adult cerebral cortex. J Comp Neurol 2009; 517:105-21. [PMID: 19711416 DOI: 10.1002/cne.22137] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Homeostatic synaptic plasticity (HSP) is important for maintaining neurons' excitability within the dynamic range and for protecting neurons from unconstrained long-term potentiation that can cause breakdown of synapse specificity (Turrigiano [2008] Cell 135:422-435). Knowledge of the molecular mechanism underlying this phenomenon remains incomplete, especially for the rapid form of HSP. To test whether HSP in adulthood depends on an F-actin binding protein, drebrin A, mice deleted of the adult isoform of drebrin (DAKO) but retaining the embryonic isoform (drebrin E) were generated. HSP was assayed by determining whether the NR2A subunit of N-methyl-D-aspartate receptors (NMDARs) can rise rapidly within spines following the application of an NMDAR antagonist, D-APV, onto the cortical surface. Electron microscopic immunocytochemistry revealed that, as expected, the D-APV treatment of wild-type (WT) mouse cortex increased the proportion of NR2A-immunolabeled spines within 30 minutes relative to basal levels in hemispheres treated with an inactive enantiomer, L-APV. This difference was significant at the postsynaptic membrane and postsynaptic density (i.e., synaptic junction) as well as at nonsynaptic sites within spines and was not accompanied by spine size changes. In contrast, the D-APV treatment of DAKO brains did not augment NR2A labeling within the spine cytoplasm or at the synaptic junction, even though basal levels of NR2A were not significantly different from those of WT cortices. These findings indicate that drebrin A is required for the rapid (<30 minutes) form of HSP at excitatory synapses of adult cortices, whereas drebrin E is sufficient for maintaining basal NR2A levels within spines.
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Affiliation(s)
- Chiye Aoki
- Center for Neural Science, New York University, New York, New York 10003, USA.
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29
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Pontrello CG, Ethell IM. Accelerators, Brakes, and Gears of Actin Dynamics in Dendritic Spines. ACTA ACUST UNITED AC 2009; 3:67-86. [PMID: 20463852 DOI: 10.2174/1874082000903020067] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dendritic spines are actin-rich structures that accommodate the postsynaptic sites of most excitatory synapses in the brain. Although dendritic spines form and mature as synaptic connections develop, they remain plastic even in the adult brain, where they can rapidly grow, change, or collapse in response to normal physiological changes in synaptic activity that underlie learning and memory. Pathological stimuli can adversely affect dendritic spine shape and number, and this is seen in neurodegenerative disorders and some forms of mental retardation and autism as well. Many of the molecular signals that control these changes in dendritic spines act through the regulation of filamentous actin (F-actin), some through direct interaction with actin, and others via downstream effectors. For example, cortactin, cofilin, and gelsolin are actin-binding proteins that directly regulate actin dynamics in dendritic spines. Activities of these proteins are precisely regulated by intracellular signaling events that control their phosphorylation state and localization. In this review, we discuss how actin-regulating proteins maintain the balance between F-actin assembly and disassembly that is needed to stabilize mature dendritic spines, and how changes in their activities may lead to rapid remodeling of dendritic spines.
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Affiliation(s)
- Crystal G Pontrello
- Biomedical Sciences Division and Neuroscience program, University of California Riverside, USA
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Takahashi H, Yamazaki H, Hanamura K, Sekino Y, Shirao T. Activity of the AMPA receptor regulates drebrin stabilization in dendritic spine morphogenesis. J Cell Sci 2009; 122:1211-9. [DOI: 10.1242/jcs.043729] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Spine morphogenesis mainly occurs during development as a morphological shift from filopodia-like thin protrusions to bulbous ones. We have previously reported that synaptic clustering of the actin-binding protein drebrin in dendritic filopodia governs spine morphogenesis and synaptic PSD-95 clustering. Here, we report the activity-dependent cellular mechanisms for spine morphogenesis, in which the activity of AMPA receptors (AMPARs) regulates drebrin clustering in spines by promoting drebrin stabilization. In cultured developing hippocampal neurons, pharmacological blockade of AMPARs, but not of other glutamate receptors, suppressed postsynaptic drebrin clustering without affecting presynaptic clustering of synapsin I (synapsin-1). Conversely, the enhancement of the action of AMPARs promoted drebrin clustering in spines. When we explored drebrin dynamics by photobleaching individual spines, we found that AMPAR activity increased the fraction of stable drebrin without affecting the time constant of drebrin turnover. An increase in the fraction of stable drebrin corresponded with increased drebrin clustering. AMPAR blockade also suppressed normal morphological maturation of spines and synaptic PSD-95 clustering in spines. Together, these data suggest that AMPAR-mediated stabilization of drebrin in spines is an activity-dependent cellular mechanism for spine morphogenesis.
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Affiliation(s)
- Hideto Takahashi
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
- ERCGSM, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Hiroyuki Yamazaki
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Kenji Hanamura
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Yuko Sekino
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
- CREST, JST, Kawaguchi, Saitama, 332-0012, Japan
- Division of Neuronal Network, Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, Tokyo, 1108-8639, Japan
| | - Tomoaki Shirao
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
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31
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Lin WH, Webb DJ. Actin and Actin-Binding Proteins: Masters of Dendritic Spine Formation, Morphology, and Function. THE OPEN NEUROSCIENCE JOURNAL 2009; 3:54-66. [PMID: 20717495 PMCID: PMC2921857 DOI: 10.2174/1874082000903020054] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Dendritic spines are actin-rich protrusions that comprise the postsynaptic sites of synapses and receive the majority of excitatory synaptic inputs in the central nervous system. These structures are central to cognitive processes, and alterations in their number, size, and morphology are associated with many neurological disorders. Although the actin cytoskeleton is thought to govern spine formation, morphology, and synaptic functions, we are only beginning to understand how modulation of actin reorganization by actin-binding proteins (ABPs) contributes to the function of dendritic spines and synapses. In this review, we discuss what is currently known about the role of ABPs in regulating the formation, morphology, motility, and plasticity of dendritic spines and synapses.
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Affiliation(s)
- Wan-Hsin Lin
- Department of Biological Sciences and Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Donna J. Webb
- Department of Biological Sciences and Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, Tennessee 37235, USA
- Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee 37235, USA
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32
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Julien C, Tremblay C, Bendjelloul F, Phivilay A, Coulombe MA, Emond V, Calon F. Decreased drebrin mRNA expression in Alzheimer disease: correlation with tau pathology. J Neurosci Res 2008; 86:2292-302. [PMID: 18338803 DOI: 10.1002/jnr.21667] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
To investigate the mRNA expression of the dendritic spine protein drebrin in Alzheimer's disease (AD), we performed post-mortem in situ hybridization studies in brain sections from 20 AD patients and 21 controls. AD diagnosis was confirmed by decreased drebrin protein and increased Abeta(40) (+464%; P < 0.05), Abeta(42) (+369%; P < 0.0001), Abeta(42/40) ratio (+226%; P < 0.01), total tau (+2,725%; P < 0.0001), and paired helical filament tau (PHFtau; +867%; P < 0.001) compared with controls. We found significant decreases in drebrin mRNA in the parietal cortex (-27%; P < 0.01), the temporal cortex (-22%; P < 0.05), and the hippocampus (-25%; P < 0.05) of AD patients compared with controls. Cortical levels of drebrin mRNA correlated positively with soluble total tau (r(2) = +0.244) but negatively with duration of symptoms (r(2) = -0.357) and PHFtau (r(2) = -0.248). Drebrin mRNA levels were correlated to a lesser degree with the drebrin protein content (r(2) = +0.136) and with sim2 (r(2) = +0.176), a potential modulator of drebrin transcription. Our results suggest that the down-regulation of drebrin mRNA expression plays an important role in AD and is closely related to the progression of the disease.
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Affiliation(s)
- Carl Julien
- Molecular Endocrinology and Oncology Research Center, Centre Hospitalier de l'Universitè, Laval Research Center, Quebec, Quebec, Canada
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33
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Goddard M, Zheng Y, Darlington CL, Smith PF. Synaptic protein expression in the medial temporal lobe and frontal cortex following chronic bilateral vestibular loss. Hippocampus 2008; 18:440-4. [DOI: 10.1002/hipo.20416] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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34
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Aoki C, Mahadomrongkul V, Fujisawa S, Habersat R, Shirao T. Chemical and morphological alterations of spines within the hippocampus and entorhinal cortex precede the onset of Alzheimer's disease pathology in double knock-in mice. J Comp Neurol 2007; 505:352-62. [PMID: 17912741 PMCID: PMC2844449 DOI: 10.1002/cne.21485] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Mice with knock-in of two mutations that affect beta amyloid processing and levels (2xKI) exhibit impaired spatial memory by 9-12 months of age, together with synaptic plasticity dysfunction in the hippocampus. The goal of this study was to identify changes in the molecular and structural characteristics of synapses that precede and thus could exert constraints upon cellular mechanisms underlying synaptic plasticity. Drebrin A is one protein reported to modulate spine sizes and trafficking of proteins to and from excitatory synapses. Thus, we examined levels of drebrin A within postsynaptic spines in the hippocampus and entorhinal cortex. Our electron microscopic immunocytochemical analyses reveal that, by 6 months, the proportion of hippocampal spines containing drebrin A is reduced and this change is accompanied by an increase in the mean size of spines and decreased density of spines. In the entorhinal cortex of 2xKI brains, we detected no decrement in the proportion of spines labeled for drebrin A and no significant change in spine density at 6 months, but rather a highly significant reduction in the level of drebrin A immunoreactivity within each spine. These changes are unlike those observed for the somatosensory cortex of 2xKI mice, in which synapse density and drebrin A immunoreactivity levels remain unchanged at 6 months and older. These results indicate that brains of 2xKI mice, like those of humans, exhibit regional differences of vulnerability, with the hippocampus exhibiting the first signatures of structural changes that, in turn, may underlie the emergent inability to update spatial memory in later months.
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Affiliation(s)
- Chiye Aoki
- Center for Neural Science, New York University, New York, NY 10003, USA.
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Hanamura K, Shirao T. [Actin cytoskeleton in dendritic spine]. Nihon Yakurigaku Zasshi 2007; 130:352-7. [PMID: 18000347 DOI: 10.1254/fpj.130.352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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