51
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Atkin G, Paulson H. Ubiquitin pathways in neurodegenerative disease. Front Mol Neurosci 2014; 7:63. [PMID: 25071440 PMCID: PMC4085722 DOI: 10.3389/fnmol.2014.00063] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 06/19/2014] [Indexed: 12/11/2022] Open
Abstract
Control of proper protein synthesis, function, and turnover is essential for the health of all cells. In neurons these demands take on the additional importance of supporting and regulating the highly dynamic connections between neurons that are necessary for cognitive function, learning, and memory. Regulating multiple unique synaptic protein environments within a single neuron while maintaining cell health requires the highly regulated processes of ubiquitination and degradation of ubiquitinated proteins through the proteasome. In this review, we examine the effects of dysregulated ubiquitination and protein clearance on the handling of disease-associated proteins and neuronal health in the most common neurodegenerative diseases.
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Affiliation(s)
- Graham Atkin
- Department of Neurology, University of Michigan Ann Arbor, MI, USA
| | - Henry Paulson
- Department of Neurology, University of Michigan Ann Arbor, MI, USA
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Tong J, Yang H, Im YJ. Crystallization and preliminary X-ray crystallographic analysis of the C-terminal domain of guanylate kinase-associated protein from Rattus norvegicus. Acta Crystallogr F Struct Biol Commun 2014; 70:949-54. [PMID: 25005096 PMCID: PMC4089539 DOI: 10.1107/s2053230x1401187x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 05/22/2014] [Indexed: 11/11/2022] Open
Abstract
Guanylate kinase-associated protein (GKAP) is a scaffolding protein that plays a role in protein-protein interactions at the synaptic junction such as linking the NMDA receptor-PSD-95 complex to the Shank-Homer complex. In this study, the C-terminal helical domain of GKAP from Rattus norvegicus was purified and crystallized by the vapour-diffusion method. To improve the diffraction quality of the GKAP crystals, a flexible loop in GKAP was truncated and an MBP (maltose-binding protein)-GKAP fusion was constructed in which the last C-terminal helix of MBP is fused to the N-terminus of the GKAP domain. The MBP-GKAP crystals diffracted to 2.0 Å resolution using synchrotron radiation. The crystal was orthorhombic, belonging to space group P2₁2₁2, with unit-cell parameters a=99.1, b=158.7, c=65.5 Å. The Matthews coefficient was determined to be 2.44 Å3 Da(-1) (solvent content 49.5%) with two molecules in the asymmetric unit. Initial attempts to solve the structure by molecular replacement using the MBP structure were successful.
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Affiliation(s)
- Junsen Tong
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
| | - Huiseon Yang
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
| | - Young Jun Im
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
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Winkle CC, McClain LM, Valtschanoff JG, Park CS, Maglione C, Gupton SL. A novel Netrin-1-sensitive mechanism promotes local SNARE-mediated exocytosis during axon branching. ACTA ACUST UNITED AC 2014; 205:217-32. [PMID: 24778312 PMCID: PMC4003241 DOI: 10.1083/jcb.201311003] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Localized plasma membrane expansion during axon branching mediated by Netrin-1 occurs via TRIM9-dependent regulation of SNARE-mediated vesicle fusion. Developmental axon branching dramatically increases synaptic capacity and neuronal surface area. Netrin-1 promotes branching and synaptogenesis, but the mechanism by which Netrin-1 stimulates plasma membrane expansion is unknown. We demonstrate that SNARE-mediated exocytosis is a prerequisite for axon branching and identify the E3 ubiquitin ligase TRIM9 as a critical catalytic link between Netrin-1 and exocytic SNARE machinery in murine cortical neurons. TRIM9 ligase activity promotes SNARE-mediated vesicle fusion and axon branching in a Netrin-dependent manner. We identified a direct interaction between TRIM9 and the Netrin-1 receptor DCC as well as a Netrin-1–sensitive interaction between TRIM9 and the SNARE component SNAP25. The interaction with SNAP25 negatively regulates SNARE-mediated exocytosis and axon branching in the absence of Netrin-1. Deletion of TRIM9 elevated exocytosis in vitro and increased axon branching in vitro and in vivo. Our data provide a novel model for the spatial regulation of axon branching by Netrin-1, in which localized plasma membrane expansion occurs via TRIM9-dependent regulation of SNARE-mediated vesicle fusion.
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Affiliation(s)
- Cortney C Winkle
- Neuroscience Center and Curriculum in Neurobiology, 2 Department of Cell Biology and Physiology, and 3 Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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54
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The ability of TRIM3 to induce growth arrest depends on RING-dependent E3 ligase activity. Biochem J 2014; 458:537-45. [PMID: 24393003 DOI: 10.1042/bj20131288] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mutation of the TRIM (tripartite motif)-NHL family members brat and mei-P26 perturb the differentiation of transit-amplifying progenitor cells resulting in tumour-like phenotypes. The NHL (named after the NCL1, HT2A and LIN41 repeat) domain is essential for their growth suppressive activity, and they can induce cell-cycle exit in a RING-independent manner. TRIM3 is the only bona fide tumour suppressor in the mammalian TRIM-NHL subfamily and similar to the other members of this family, its ability to inhibit cell proliferation depends on the NHL domain. However, whether the RING domain was required for TRIM3-dependent cell-cycle exit had not been investigated. In the present study, we establish that the RING domain is required for TRIM3-induced growth suppression. Furthermore, we show that this domain is necessary to promote ubiquitination of p21 in a reconstituted in vitro system where UbcH5a is the preferred E2. Thus the ability of TRIM3 to suppress growth is associated with its ability to ubiquitinate proteins.
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55
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O'Connor EC, Bariselli S, Bellone C. Synaptic basis of social dysfunction: a focus on postsynaptic proteins linking group-I mGluRs with AMPARs and NMDARs. Eur J Neurosci 2014; 39:1114-29. [DOI: 10.1111/ejn.12510] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 01/06/2014] [Accepted: 01/10/2014] [Indexed: 12/21/2022]
Affiliation(s)
- Eoin C. O'Connor
- Department of Basic Neurosciences; Medical Faculty; University of Geneva; 1 Rue Michel Servet CH-1211 Geneva Switzerland
| | - Sebastiano Bariselli
- Department of Basic Neurosciences; Medical Faculty; University of Geneva; 1 Rue Michel Servet CH-1211 Geneva Switzerland
| | - Camilla Bellone
- Department of Basic Neurosciences; Medical Faculty; University of Geneva; 1 Rue Michel Servet CH-1211 Geneva Switzerland
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56
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Thein S, Tao-Cheng JH, Li Y, Bayer KU, Reese TS, Dosemeci A. CaMKII mediates recruitment and activation of the deubiquitinase CYLD at the postsynaptic density. PLoS One 2014; 9:e91312. [PMID: 24614225 PMCID: PMC3948843 DOI: 10.1371/journal.pone.0091312] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 02/10/2014] [Indexed: 11/18/2022] Open
Abstract
NMDA treatment of cultured hippocampal neurons causes recruitment of CYLD, as well as CaMKII, to the postsynaptic density (PSD), as shown by immunoelectron microscopy. Recruitment of CYLD, a deubiquitinase specific for K63-linked polyubiquitins, is blocked by pre-treatment with tatCN21, a CaMKII inhibitor, at a concentration that inhibits the translocation of CaMKII to the PSD. Furthermore, CaMKII co-immunoprecipitates with CYLD from solubilized PSD fractions, indicating an association between the proteins. Purified CaMKII phosphorylates CYLD on at least three residues (S-362, S-418, and S-772 on the human CYLD protein Q9NQC7-1) and promotes its deubiquitinase activity. Activation of CaMKII in isolated PSDs promotes phosphorylation of CYLD on the same residues and also enhances endogenous deubiquitinase activity specific for K63-linked polyubiquitins. Since K63-linked polyubiquitin conjugation to proteins inhibits their interaction with proteasomes, CaMKII-mediated recruitment and upregulation of CYLD is expected to remove K63-linked polyubiquitins and facilitate proteasomal degradation at the PSD.
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Affiliation(s)
- Soe Thein
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (ST); (AD)
| | - Jung-Hwa Tao-Cheng
- EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Yan Li
- Protein/Peptide Sequencing Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - K. Ulrich Bayer
- Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, Colorado, United States of America
| | - Thomas S. Reese
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (ST); (AD)
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57
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Vitureira N, Goda Y. Cell biology in neuroscience: the interplay between Hebbian and homeostatic synaptic plasticity. ACTA ACUST UNITED AC 2013; 203:175-86. [PMID: 24165934 PMCID: PMC3812972 DOI: 10.1083/jcb.201306030] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Synaptic plasticity, a change in the efficacy of synaptic signaling, is a key property of synaptic communication that is vital to many brain functions. Hebbian forms of long-lasting synaptic plasticity-long-term potentiation (LTP) and long-term depression (LTD)-have been well studied and are considered to be the cellular basis for particular types of memory. Recently, homeostatic synaptic plasticity, a compensatory form of synaptic strength change, has attracted attention as a cellular mechanism that counteracts changes brought about by LTP and LTD to help stabilize neuronal network activity. New findings on the cellular mechanisms and molecular players of the two forms of plasticity are uncovering the interplay between them in individual neurons.
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Affiliation(s)
- Nathalia Vitureira
- Departmento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo 11100, Uruguay
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58
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Caldeira MV, Salazar IL, Curcio M, Canzoniero LMT, Duarte CB. Role of the ubiquitin-proteasome system in brain ischemia: friend or foe? Prog Neurobiol 2013; 112:50-69. [PMID: 24157661 DOI: 10.1016/j.pneurobio.2013.10.003] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 10/08/2013] [Accepted: 10/15/2013] [Indexed: 11/26/2022]
Abstract
The ubiquitin-proteasome system (UPS) is a catalytic machinery that targets numerous cellular proteins for degradation, thus being essential to control a wide range of basic cellular processes and cell survival. Degradation of intracellular proteins via the UPS is a tightly regulated process initiated by tagging a target protein with a specific ubiquitin chain. Neurons are particularly vulnerable to any change in protein composition, and therefore the UPS is a key regulator of neuronal physiology. Alterations in UPS activity may induce pathological responses, ultimately leading to neuronal cell death. Brain ischemia triggers a complex series of biochemical and molecular mechanisms, such as an inflammatory response, an exacerbated production of misfolded and oxidized proteins, due to oxidative stress, and the breakdown of cellular integrity mainly mediated by excitotoxic glutamatergic signaling. Brain ischemia also damages protein degradation pathways which, together with the overproduction of damaged proteins and consequent upregulation of ubiquitin-conjugated proteins, contribute to the accumulation of ubiquitin-containing proteinaceous deposits. Despite recent advances, the factors leading to deposition of such aggregates after cerebral ischemic injury remain poorly understood. This review discusses the current knowledge on the role of the UPS in brain function and the molecular mechanisms contributing to UPS dysfunction in brain ischemia with consequent accumulation of ubiquitin-containing proteins. Chemical inhibitors of the proteasome and small molecule inhibitors of deubiquitinating enzymes, which promote the degradation of proteins by the proteasome, were both shown to provide neuroprotection in brain ischemia, and this apparent contradiction is also discussed in this review.
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Affiliation(s)
- Margarida V Caldeira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Ivan L Salazar
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal; Doctoral Programme in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra (IIIUC), Portugal
| | - Michele Curcio
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal; Department of Science and Technology, University of Sannio, Benevento, Italy
| | | | - Carlos B Duarte
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Largo Marquês de Pombal, 3004-517 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal.
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59
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Wang X, Bey AL, Chung L, Krystal AD, Jiang YH. Therapeutic approaches for shankopathies. Dev Neurobiol 2013; 74:123-35. [PMID: 23536326 DOI: 10.1002/dneu.22084] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 03/21/2013] [Indexed: 12/13/2022]
Abstract
Despite recent advances in understanding the molecular mechanisms of autism spectrum disorders (ASD), the current treatments for these disorders are mostly focused on behavioral and educational approaches. The considerable clinical and molecular heterogeneity of ASD present a significant challenge to the development of an effective treatment targeting underlying molecular defects. Deficiency of SHANK family genes causing ASD represent an exciting opportunity for developing molecular therapies because of strong genetic evidence for SHANK as causative genes in ASD and the availability of a panel of Shank mutant mouse models. In this article, we review the literature suggesting the potential for developing therapies based on molecular characteristics and discuss several exciting themes that are emerging from studying Shank mutant mice at the molecular level and in terms of synaptic function.
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Affiliation(s)
- Xiaoming Wang
- Department of Pediatrics, Duke University School of Medicine Durham, North Carolina, 27710
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60
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Labonté D, Thies E, Pechmann Y, Groffen AJ, Verhage M, Smit AB, van Kesteren RE, Kneussel M. TRIM3 regulates the motility of the kinesin motor protein KIF21B. PLoS One 2013; 8:e75603. [PMID: 24086586 PMCID: PMC3782429 DOI: 10.1371/journal.pone.0075603] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 08/15/2013] [Indexed: 01/01/2023] Open
Abstract
Kinesin superfamily proteins (KIFs) are molecular motors that transport cellular cargo along the microtubule cytoskeleton. KIF21B is a neuronal kinesin that is highly enriched in dendrites. The regulation and specificity of microtubule transport involves the binding of motors to individual cargo adapters and accessory proteins. Moreover, posttranslational modifications of either the motor protein, their cargos or tubulin regulate motility, cargo recognition and the binding or unloading of cargos. Here we show that the ubiquitin E3 ligase TRIM3, also known as BERP, interacts with KIF21B via its RBCC domain. TRIM3 is found at intracellular and Golgi-derived vesicles and co-localizes with the KIF21B motor in neurons. Trim3 gene deletion in mice and TRIM3 overexpression in cultured neurons both suggested that the E3-ligase function of TRIM3 is not involved in KIF21B degradation, however TRIM3 depletion reduces the motility of the motor. Together, our data suggest that TRIM3 is a regulator in the modulation of KIF21B motor function.
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Affiliation(s)
- Dorthe Labonté
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Edda Thies
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Yvonne Pechmann
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Alexander J. Groffen
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Ronald E. van Kesteren
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, Netherlands
| | - Matthias Kneussel
- Department of Molecular Neurogenetics, Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- * E-mail:
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61
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Abstract
Shank family proteins (Shank1, Shank2, and Shank3) are synaptic scaffolding proteins that organize an extensive protein complex at the postsynaptic density (PSD) of excitatory glutamatergic synapses. Recent human genetic studies indicate that SHANK family genes (SHANK1, SHANK2, and SHANK3) are causative genes for idiopathic autism spectrum disorders (ASD). Neurobiological studies of Shank mutations in mice support a general hypothesis of synaptic dysfunction in the pathophysiology of ASD. However, the molecular diversity of SHANK family gene products, as well as the heterogeneity in human and mouse phenotypes, pose challenges to modeling human SHANK mutations. Here, we review the molecular genetics of SHANK mutations in human ASD and discuss recent findings where such mutations have been modeled in mice. Conserved features of synaptic dysfunction and corresponding behaviors in Shank mouse mutants may help dissect the pathophysiology of ASD, but also highlight divergent phenotypes that arise from different mutations in the same gene.
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Affiliation(s)
- Yong-hui Jiang
- Departments of Pediatrics and Neurobiology, Duke University School of Medicine, Durham NC 27710, USA
| | - Michael D. Ehlers
- Pfizer Worldwide Research and Development, Neuroscience Research Unit, Cambridge, MA 02129, USA
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62
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Lee PCW, Dodart JC, Aron L, Finley LW, Bronson RT, Haigis MC, Yankner BA, Harper JW. Altered social behavior and neuronal development in mice lacking the Uba6-Use1 ubiquitin transfer system. Mol Cell 2013; 50:172-84. [PMID: 23499007 DOI: 10.1016/j.molcel.2013.02.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 12/04/2012] [Accepted: 02/11/2013] [Indexed: 01/01/2023]
Abstract
The Uba6 (E1)-Use1 (E2) ubiquitin transfer cascade is a poorly understood alternative arm of the ubiquitin proteasome system (UPS) and is required for mouse embryonic development, independent of the canonical Uba1-E2-E3 pathway. Loss of neuronal Uba6 during embryonic development results in altered patterning of neurons in the hippocampus and the amygdala, decreased dendritic spine density, and numerous behavioral disorders. The levels of the E3 ubiquitin ligase Ube3a (E6-AP) and Shank3, both linked with dendritic spine function, are elevated in the amygdala of Uba6-deficient mice, while levels of the Ube3a substrate Arc are reduced. Uba6 and Use1 promote proteasomal turnover of Ube3a in mouse embryo fibroblasts (MEFs) and catalyze Ube3a ubiquitylation in vitro. These activities occur in parallel with an independent pathway involving Uba1-UbcH7, but in a spatially distinct manner in MEFs. These data reveal an unanticipated role for Uba6 in neuronal development, spine architecture, mouse behavior, and turnover of Ube3a.
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Affiliation(s)
- Peter C W Lee
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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63
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Myosin motors at neuronal synapses: drivers of membrane transport and actin dynamics. Nat Rev Neurosci 2013; 14:233-47. [DOI: 10.1038/nrn3445] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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64
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Activity-dependent neuronal signalling and autism spectrum disorder. Nature 2013; 493:327-37. [PMID: 23325215 DOI: 10.1038/nature11860] [Citation(s) in RCA: 455] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 11/08/2012] [Indexed: 02/06/2023]
Abstract
Neuronal activity induces the post-translational modification of synaptic molecules, promotes localized protein synthesis within dendrites and activates gene transcription, thereby regulating synaptic function and allowing neuronal circuits to respond dynamically to experience. Evidence indicates that many of the genes that are mutated in autism spectrum disorder are crucial components of the activity-dependent signalling networks that regulate synapse development and plasticity. Dysregulation of activity-dependent signalling pathways in neurons may, therefore, have a key role in the aetiology of autism spectrum disorder.
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65
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Breaking it down: the ubiquitin proteasome system in neuronal morphogenesis. Neural Plast 2013; 2013:196848. [PMID: 23476809 PMCID: PMC3586504 DOI: 10.1155/2013/196848] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 12/31/2012] [Indexed: 01/20/2023] Open
Abstract
The ubiquitin-proteasome system (UPS) is most widely known for its role in intracellular protein degradation; however, in the decades since its discovery, ubiquitination has been associated with the regulation of a wide variety of cellular processes. The addition of ubiquitin tags, either as single moieties or as polyubiquitin chains, has been shown not only to mediate degradation by the proteasome and the lysosome, but also to modulate protein function, localization, and endocytosis. The UPS plays a particularly important role in neurons, where local synthesis and degradation work to balance synaptic protein levels at synapses distant from the cell body. In recent years, the UPS has come under increasing scrutiny in neurons, as elements of the UPS have been found to regulate such diverse neuronal functions as synaptic strength, homeostatic plasticity, axon guidance, and neurite outgrowth. Here we focus on recent advances detailing the roles of the UPS in regulating the morphogenesis of axons, dendrites, and dendritic spines, with an emphasis on E3 ubiquitin ligases and their identified regulatory targets.
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66
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In vivo quantitative proteomics of somatosensory cortical synapses shows which protein levels are modulated by sensory deprivation. Proc Natl Acad Sci U S A 2013; 110:E726-35. [PMID: 23382246 DOI: 10.1073/pnas.1300424110] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Postnatal bilateral whisker trimming was used as a model system to test how synaptic proteomes are altered in barrel cortex by sensory deprivation during synaptogenesis. Using quantitative mass spectrometry, we quantified more than 7,000 synaptic proteins and identified 89 significantly reduced and 161 significantly elevated proteins in sensory-deprived synapses, 22 of which were validated by immunoblotting. More than 95% of quantified proteins, including abundant synaptic proteins such as PSD-95 and gephyrin, exhibited no significant difference under high- and low-activity rearing conditions, suggesting no tissue-wide changes in excitatory or inhibitory synaptic density. In contrast, several proteins that promote mature spine morphology and synaptic strength, such as excitatory glutamate receptors and known accessory factors, were reduced significantly in deprived synapses. Immunohistochemistry revealed that the reduction in SynGAP1, a postsynaptic scaffolding protein, was restricted largely to layer I of barrel cortex in sensory-deprived rats. In addition, protein-degradation machinery such as proteasome subunits, E2 ligases, and E3 ligases, accumulated significantly in deprived synapses, suggesting targeted synaptic protein degradation under sensory deprivation. Importantly, this screen identified synaptic proteins whose levels were affected by sensory deprivation but whose synaptic roles have not yet been characterized in mammalian neurons. These data demonstrate the feasibility of defining synaptic proteomes under different sensory rearing conditions and could be applied to elucidate further molecular mechanisms of sensory development.
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67
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Ubiquitination of neurotransmitter receptors and postsynaptic scaffolding proteins. Neural Plast 2013; 2013:432057. [PMID: 23431475 PMCID: PMC3574743 DOI: 10.1155/2013/432057] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 12/26/2012] [Indexed: 12/19/2022] Open
Abstract
The human brain is made up of an extensive network of neurons that communicate by forming specialized connections called synapses. The amount, location, and dynamic turnover of synaptic proteins, including neurotransmitter receptors and synaptic scaffolding molecules, are under complex regulation and play a crucial role in synaptic connectivity and plasticity, as well as in higher brain functions. An increasing number of studies have established ubiquitination and proteasome-mediated degradation as universal mechanisms in the control of synaptic protein homeostasis. In this paper, we focus on the role of the ubiquitin-proteasome system (UPS) in the turnover of major neurotransmitter receptors, including glutamatergic and nonglutamatergic receptors, as well as postsynaptic receptor-interacting proteins.
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68
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Pick JE, Malumbres M, Klann E. The E3 ligase APC/C-Cdh1 is required for associative fear memory and long-term potentiation in the amygdala of adult mice. Learn Mem 2012; 20:11-20. [PMID: 23242419 DOI: 10.1101/lm.027383.112] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The anaphase promoting complex/cyclosome (APC/C) is an E3 ligase regulated by Cdh1. Beyond its role in controlling cell cycle progression, APC/C-Cdh1 has been detected in neurons and plays a role in long-lasting synaptic plasticity and long-term memory. Herein, we further examined the role of Cdh1 in synaptic plasticity and memory by generating knockout mice where Cdh1 was conditionally eliminated from the forebrain post-developmentally. Although spatial learning and memory in the Morris water maze (MWM) was normal, the Cdh1 conditional knockout (cKO) mice displayed enhanced reversal learning in the MWM and in a water-based Y maze. In addition, we found that the Cdh1 cKO mice had impaired associative fear memory and exhibited impaired long-term potentiation (LTP) in amygdala slices. Finally, we observed increased expression of Shank1 and NR2A expression in amygdalar slices from the Cdh1 cKO mice following the induction of LTP, suggesting a possible molecular mechanism underlying the behavioral and synaptic plasticity impairments displayed in these mice. Our findings are consistent with a role for the APC/C-Cdh1 in fear memory and synaptic plasticity in the amygdala.
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Affiliation(s)
- Joseph E Pick
- Center for Neural Science, New York University, New York, New York 10003, USA
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69
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Shin SM, Zhang N, Hansen J, Gerges NZ, Pak DTS, Sheng M, Lee SH. GKAP orchestrates activity-dependent postsynaptic protein remodeling and homeostatic scaling. Nat Neurosci 2012; 15:1655-66. [PMID: 23143515 PMCID: PMC3804128 DOI: 10.1038/nn.3259] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 10/11/2012] [Indexed: 02/07/2023]
Abstract
How does chronic activity modulation lead to global remodeling of proteins at synapses and synaptic scaling? Here we report a role of guanylate-kinase-associated-protein (GKAP; also known as SAPAP), a scaffolding molecule linking NMDA receptor-PSD-95 to Shank-Homer complexes, in these processes. Over-excitation removes GKAP from synapses via ubiquitin-proteasome system, while inactivity induces synaptic accumulation of GKAP in rat hippocampal neurons. The bi-directional changes of synaptic GKAP levels are controlled by specific CaMKII isoforms coupled to different Ca2+ channels. α-CaMKII activated by NMDA receptor phosphorylates Serine-54 of GKAP to induce poly-ubiquitination of GKAP. In contrast, β-CaMKII activation via L-type voltage-dependent calcium channel promotes GKAP recruitment by phosphorylating Serine-340 and Serine-384 residues, which uncouples GKAP from MyoVa motor complex. Remarkably, overexpressing GKAP turnover mutants not only hampers activity-dependent remodeling of PSD-95 and Shank but also blocks bi-directional synaptic scaling. Therefore, activity-dependent turnover of PSD proteins orchestrated by GKAP is critical for homeostatic plasticity.
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Affiliation(s)
- Seung Min Shin
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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70
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Dosemeci A, Thein S, Yang Y, Reese TS, Tao-Cheng JH. CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, accumulates at the postsynaptic density in an activity-dependent manner. Biochem Biophys Res Commun 2012; 430:245-9. [PMID: 23146630 DOI: 10.1016/j.bbrc.2012.10.131] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 10/30/2012] [Indexed: 11/16/2022]
Abstract
Polyubiquitin chains on proteins flag them for distinct fates depending on the type of polyubiquitin linkage. While lysine48-linked polyubiquitination directs proteins to proteasomal degradation, lysine63-linked polyubiquitination promotes different protein trafficking and is involved in autophagy. Here we show that postsynaptic density (PSD) fractions from adult rat brain contain deubiquitinase activity that targets both lysine48 and lysine63-linked polyubiquitins. Comparison of PSD fractions with parent subcellular fractions by Western immunoblotting reveals that CYLD, a deubiquitinase specific for lysine63-linked polyubiquitins, is highly enriched in the PSD fraction. Electron microscopic examination of hippocampal neurons in culture under basal conditions shows immunogold label for CYLD at the PSD complex in approximately one in four synapses. Following depolarization by exposure to high K+, the proportion of CYLD-labeled PSDs as well as the labeling intensity of CYLD at the PSD increased by more than eighty percent, indicating that neuronal activity promotes accumulation of CYLD at the PSD. An increase in postsynaptic CYLD following activity would promote removal of lysine63-polyubiquitins from PSD proteins and thus could regulate their trafficking and prevent their autophagic degradation.
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Affiliation(s)
- Ayse Dosemeci
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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71
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Irmler M, Gentier RJG, Dennissen FJA, Schulz H, Bolle I, Hölter SM, Kallnik M, Cheng JJ, Klingenspor M, Rozman J, Ehrhardt N, Hermes DJHP, Gailus-Durner V, Fuchs H, Hrabě de Angelis M, Meyer HE, Hopkins DA, Van Leeuwen FW, Beckers J. Long-term proteasomal inhibition in transgenic mice by UBB(+1) expression results in dysfunction of central respiration control reminiscent of brainstem neuropathology in Alzheimer patients. Acta Neuropathol 2012; 124:187-97. [PMID: 22730000 PMCID: PMC3400757 DOI: 10.1007/s00401-012-1003-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 06/08/2012] [Accepted: 06/11/2012] [Indexed: 12/29/2022]
Abstract
Aging and neurodegeneration are often accompanied by a functionally impaired ubiquitin–proteasome system (UPS). In tauopathies and polyglutamine diseases, a mutant form of ubiquitin B (UBB+1) accumulates in disease-specific aggregates. UBB+1 mRNA is generated at low levels in vivo during transcription from the ubiquitin B locus by molecular misreading. The resulting mutant protein has been shown to inhibit proteasome function. To elucidate causative effects and neuropathological consequences of UBB+1 accumulation, we used a UBB+1 expressing transgenic mouse line that models UPS inhibition in neurons and exhibits behavioral phenotypes reminiscent of Alzheimer’s disease (AD). In order to reveal affected organs and functions, young and aged UBB+1 transgenic mice were comprehensively phenotyped for more than 240 parameters. This revealed unexpected changes in spontaneous breathing patterns and an altered response to hypoxic conditions. Our findings point to a central dysfunction of respiratory regulation in transgenic mice in comparison to wild-type littermate mice. Accordingly, UBB+1 was strongly expressed in brainstem regions of transgenic mice controlling respiration. These regions included, e.g., the medial part of the nucleus of the tractus solitarius and the lateral subdivisions of the parabrachial nucleus. In addition, UBB+1 was also strongly expressed in these anatomical structures of AD patients (Braak stage #6) and was not expressed in non-demented controls. We conclude that long-term UPS inhibition due to UBB+1 expression causes central breathing dysfunction in a transgenic mouse model of AD. The UBB+1 expression pattern in humans is consistent with the contribution of bronchopneumonia as a cause of death in AD patients.
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Affiliation(s)
- Martin Irmler
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Romina J. G. Gentier
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Frank J. A. Dennissen
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Holger Schulz
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Epidemiology I, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Ines Bolle
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Lung Biology and Disease, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Sabine M. Hölter
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Developmental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Magdalena Kallnik
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Developmental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Jing Jun Cheng
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Martin Klingenspor
- Technische Universität München, ZIEL—Research Center for Nutrition and Food Sciences, Molecular Nutritional Medicine, Gregor-Mendel-Straße 2, 85350 Freising-Weihenstephan, Germany
| | - Jan Rozman
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
- Technische Universität München, ZIEL—Research Center for Nutrition and Food Sciences, Molecular Nutritional Medicine, Gregor-Mendel-Straße 2, 85350 Freising-Weihenstephan, Germany
| | - Nicole Ehrhardt
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Denise J. H. P. Hermes
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Valérie Gailus-Durner
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Helmut Fuchs
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
| | - Martin Hrabě de Angelis
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
- Technische Universität München, WZW—Center of Life and Food Science Weihenstephan, Chair of Experimental Genetics, 85350 Freising-Weihenstephan, Germany
| | - Helmut E. Meyer
- Medical Proteome Center, Ruhr University Bochum, Bochum, Germany
| | - David A. Hopkins
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Fred W. Van Leeuwen
- Department of Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands
| | - Johannes Beckers
- Helmholtz Zentrum München, National Research Center for Environment and Health, GmbH, Institute of Experimental Genetics, Ingolstaedter Landstr. 1, 85764 Neuherberg, Germany
- Technische Universität München, WZW—Center of Life and Food Science Weihenstephan, Chair of Experimental Genetics, 85350 Freising-Weihenstephan, Germany
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72
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Baptista MS, Duarte CB, Maciel P. Role of the ubiquitin-proteasome system in nervous system function and disease: using C. elegans as a dissecting tool. Cell Mol Life Sci 2012; 69:2691-715. [PMID: 22382927 PMCID: PMC11115168 DOI: 10.1007/s00018-012-0946-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Revised: 02/13/2012] [Accepted: 02/15/2012] [Indexed: 01/12/2023]
Abstract
In addition to its central roles in protein quality control, regulation of cell cycle, intracellular signaling, DNA damage response and transcription regulation, the ubiquitin-proteasome system (UPS) plays specific roles in the nervous system, where it contributes to precise connectivity through development, and later assures functionality by regulating a wide spectrum of neuron-specific cellular processes. Aberrations in this system have been implicated in the etiology of neurodevelopmental and neurodegenerative diseases. In this review, we provide an updated view on the UPS and highlight recent findings concerning its role in normal and diseased nervous systems. We discuss the advantages of the model organism Caenorhabditis elegans as a tool to unravel the major unsolved questions concerning this biochemical pathway and its involvement in nervous system function and dysfunction, and expose the new possibilities, using state-of-the-art techniques, to assess UPS function using this model system.
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Affiliation(s)
- Márcio S Baptista
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
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73
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Zhang X, Zhao H, Chen Y, Liu C, Meng K, Yang P, Wang Y, Wang G, Yao B. Characterization and biological function analysis of the trim3a gene from zebrafish (Danio rerio). FISH & SHELLFISH IMMUNOLOGY 2012; 32:621-628. [PMID: 22300786 DOI: 10.1016/j.fsi.2011.12.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 12/12/2011] [Accepted: 12/12/2011] [Indexed: 05/31/2023]
Abstract
The biological significance of tripartite motif (TRIM) proteins is increasingly being appreciated due to their roles in a broad range of biological processes that associated with innate immunity. In this study, we have described the structural and functional analysis of TRIM3a from zebrafish. Annotation of domain architectures found that the TRIM3a fulfills the TRIM-NHL rule of domain composition with a Filamin/ABP280 domain and NHL repeats at its C-terminal region. In addition, the mRNA expression level of TRIM3a was the highest in brain, and with a relatively higher level in spleen, liver, and gill. A strong expression starting at 36 h post fertilization (hpf) was observed by real-time PCR and could be detected in brain by in situ hybridization, suggesting that TRIM3a protein might play an important role in brain development in zebrafish. Considering that TRIM3a has a RING finger domain, we expressed and purified the TRIM3a protein and performed ubiquitylation assays, our results showed that TRIM3a underwent self-polyubiquitylation in combination with E1, UbcH5c, biotin-ubiquitin in vitro. Meanwhile, TRIM3a-R without the RING domain was expressed and purified as well, in vitro ubiquitylation assays showed that the self-ubiquitylation of TRIM3a was dependent on its RING domain, suggesting that TRIM3a might function as a RING finger E3 ubiquitin ligase.
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Affiliation(s)
- Xinshang Zhang
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, PR China
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74
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Ting JT, Peça J, Feng G. Functional consequences of mutations in postsynaptic scaffolding proteins and relevance to psychiatric disorders. Annu Rev Neurosci 2012; 35:49-71. [PMID: 22540979 DOI: 10.1146/annurev-neuro-062111-150442] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Functional studies on postsynaptic scaffolding proteins at excitatory synapses have revealed a plethora of important roles for synaptic structure and function. In addition, a convergence of recent in vivo functional evidence together with human genetics data strongly suggest that mutations in a variety of these postsynaptic scaffolding proteins may contribute to the etiology of diverse human psychiatric disorders such as schizophrenia, autism spectrum disorders, and obsessive-compulsive spectrum disorders. Here we review the most recent evidence for several key postsynaptic scaffolding protein families and explore how mouse genetics and human genetics have intersected to advance our knowledge concerning the contributions of these important players to complex brain function and dysfunction.
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Affiliation(s)
- Jonathan T Ting
- McGovern Institute for Brain Research and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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75
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Synaptic protein degradation in memory reorganization. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:221-40. [PMID: 22351058 DOI: 10.1007/978-3-7091-0932-8_10] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The ubiquitin-proteasome system (UPS) is a ubiquitous, major pathway of protein degradation that is involved in most cellular processes by regulating the abundance of certain proteins. Accumulating evidence indicates a role for the UPS in specific functions of neurons. In this chapter, we first introduce the role of the UPS in neuronal function and the mechanism of UPS regulation following synaptic activity. Then, we focus on the recently revealed, distinct role of the UPS in the destabilization of a reactivated memory. Finally, we discuss the physiological role of this destabilization process. The reactivated memory may undergo modification from the initial memory depending on the context in which the memory is reactivated, which we will term memory reorganization. We will introduce the role of the protein degradation-dependent destabilization process for memory reorganization and suggest a hypothetical model combining the recent findings.
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76
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Scaffold proteins at the postsynaptic density. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:29-61. [PMID: 22351050 DOI: 10.1007/978-3-7091-0932-8_2] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Scaffold proteins are abundant and essential components of the postsynaptic density (PSD). They play a major role in many synaptic functions including the trafficking, anchoring, and clustering of glutamate receptors and adhesion molecules. Moreover, they link postsynaptic receptors with their downstream signaling proteins and regulate the dynamics of cytoskeletal structures. By definition, PSD scaffold proteins do not have intrinsic enzymatic activities but are formed by modular and specific domains deputed to form large protein networks. Here, we will discuss the latest findings regarding the structure and functions of major PSD scaffold proteins. Given that scaffold proteins are central components of PSD architecture, it is not surprising that deletion or mutations in their human genes cause severe neuropsychiatric disorders including autism, mental retardation, and schizophrenia. Thus, their dynamic organization and regulation are directly correlated with the essential structure of the PSD and the normal physiology of neuronal synapses.
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77
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Sheng M, Kim E. The postsynaptic organization of synapses. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a005678. [PMID: 22046028 DOI: 10.1101/cshperspect.a005678] [Citation(s) in RCA: 390] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The postsynaptic side of the synapse is specialized to receive the neurotransmitter signal released from the presynaptic terminal and transduce it into electrical and biochemical changes in the postsynaptic cell. The cardinal functional components of the postsynaptic specialization of excitatory and inhibitory synapses are the ionotropic receptors (ligand-gated channels) for glutamate and γ-aminobutyric acid (GABA), respectively. These receptor channels are concentrated at the postsynaptic membrane and embedded in a dense and rich protein network comprised of anchoring and scaffolding molecules, signaling enzymes, cytoskeletal components, as well as other membrane proteins. Excitatory and inhibitory postsynaptic specializations are quite different in molecular organization. The postsynaptic density of excitatory synapses is especially complex and dynamic in composition and regulation; it contains hundreds of different proteins, many of which are required for cognitive function and implicated in psychiatric illness.
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Affiliation(s)
- Morgan Sheng
- The Department of Neuroscience, Genentech Incorporated, San Francisco, California 94080, USA
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78
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Roselli F, Livrea P, Almeida OFX. CDK5 is essential for soluble amyloid β-induced degradation of GKAP and remodeling of the synaptic actin cytoskeleton. PLoS One 2011; 6:e23097. [PMID: 21829588 PMCID: PMC3146526 DOI: 10.1371/journal.pone.0023097] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 07/11/2011] [Indexed: 01/01/2023] Open
Abstract
The early stages of Alzheimer's disease are marked by synaptic dysfunction and loss. This process results from the disassembly and degradation of synaptic components, in particular of scaffolding proteins that compose the post-synaptic density (PSD), namely PSD95, Homer and Shank. Here we investigated in rat frontal cortex dissociated culture the mechanisms involved in the downregulation of GKAP (SAPAP1), which links the PSD95 complex to the Shank complex and cytoskeletal structures within the PSD. We show that Aβ causes the rapid loss of GKAP from synapses through a pathway that critically requires cdk5 activity, and is set in motion by NMDAR activity and Ca(2+) influx. We show that GKAP is a direct substrate of cdk5 and that its phosphorylation results in polyubiquitination and proteasomal degradation of GKAP and remodeling (collapse) of the synaptic actin cytoskeleton; the latter effect is abolished in neurons expressing GKAP mutants that are resistant to phosphorylation by cdk5. Given that cdk5 also regulates degradation of PSD95, these results underscore the central position of cdk5 in mediating Aβ-induced PSD disassembly and synapse loss.
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Affiliation(s)
- Francesco Roselli
- Neuroadaptation Group, Max Planck Institute of Psychiatry, Munich, Germany
- Department of Neurological and Psychiatric Sciences, University of Bari, Bari, Italy
- * E-mail: (FR); (OFXA)
| | - Paolo Livrea
- Department of Neurological and Psychiatric Sciences, University of Bari, Bari, Italy
| | - Osborne F. X. Almeida
- Neuroadaptation Group, Max Planck Institute of Psychiatry, Munich, Germany
- * E-mail: (FR); (OFXA)
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79
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Wang X, McCoy PA, Rodriguiz RM, Pan Y, Je HS, Roberts AC, Kim CJ, Berrios J, Colvin JS, Bousquet-Moore D, Lorenzo I, Wu G, Weinberg RJ, Ehlers MD, Philpot BD, Beaudet AL, Wetsel WC, Jiang YH. Synaptic dysfunction and abnormal behaviors in mice lacking major isoforms of Shank3. Hum Mol Genet 2011; 20:3093-108. [PMID: 21558424 DOI: 10.1093/hmg/ddr212] [Citation(s) in RCA: 413] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
SHANK3 is a synaptic scaffolding protein enriched in the postsynaptic density (PSD) of excitatory synapses. Small microdeletions and point mutations in SHANK3 have been identified in a small subgroup of individuals with autism spectrum disorder (ASD) and intellectual disability. SHANK3 also plays a key role in the chromosome 22q13.3 microdeletion syndrome (Phelan-McDermid syndrome), which includes ASD and cognitive dysfunction as major clinical features. To evaluate the role of Shank3 in vivo, we disrupted major isoforms of the gene in mice by deleting exons 4-9. Isoform-specific Shank3(e4-9) homozygous mutant mice display abnormal social behaviors, communication patterns, repetitive behaviors and learning and memory. Shank3(e4-9) male mice display more severe impairments than females in motor coordination. Shank3(e4-9) mice have reduced levels of Homer1b/c, GKAP and GluA1 at the PSD, and show attenuated activity-dependent redistribution of GluA1-containing AMPA receptors. Subtle morphological alterations in dendritic spines are also observed. Although synaptic transmission is normal in CA1 hippocampus, long-term potentiation is deficient in Shank3(e4-9) mice. We conclude that loss of major Shank3 species produces biochemical, cellular and morphological changes, leading to behavioral abnormalities in mice that bear similarities to human ASD patients with SHANK3 mutations.
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Affiliation(s)
- Xiaoming Wang
- Department of Pediatrics, Duke University School of Medicine, Durham, NC 27710, USA
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80
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Bingol B, Sheng M. Deconstruction for reconstruction: the role of proteolysis in neural plasticity and disease. Neuron 2011; 69:22-32. [PMID: 21220096 DOI: 10.1016/j.neuron.2010.11.006] [Citation(s) in RCA: 225] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2010] [Indexed: 12/17/2022]
Abstract
The brain changes in response to experience and altered environment. This neural plasticity is largely mediated by morphological and functional modification of synapses, a process that depends on both synthesis and degradation of proteins. It is now clear that regulated proteolysis plays a critical role in the remodeling of synapses, learning and memory, and neurodevelopment. Here, we highlight the mechanisms and functions of proteolysis in synaptic plasticity and discuss its alteration in disease states.
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Affiliation(s)
- Baris Bingol
- Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA
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81
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Kaang BK, Choi JH. Protein Degradation during Reconsolidation as a Mechanism for Memory Reorganization. Front Behav Neurosci 2011; 5:2. [PMID: 21344006 PMCID: PMC3034226 DOI: 10.3389/fnbeh.2011.00002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 01/17/2011] [Indexed: 11/13/2022] Open
Abstract
Memory is a reference formed from a past experience that is used to respond to present situations. However, the world is dynamic and situations change, so it is important to update the memory with new information each time it is reactivated in order to adjust the response in the future. Recent researches indicate that memory may undergo a dynamic process that could work as an updating mechanism. This process which is called reconsolidation involves destabilization of the memory after it is reactivated, followed by restabilization. Recently, it has been demonstrated that the initial destabilization process of reconsolidation requires protein degradation. Using protein degradation inhibition as a method to block reconsolidation, recent researches suggest that reconsolidation, especially the protein degradation-dependent destabilization process is necessary for memory reorganization.
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Affiliation(s)
- Bong-Kiun Kaang
- National Creative Research Initiative Center for Memory, Department of Biological Sciences, College of Natural Sciences, Seoul National University Seoul, South Korea
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82
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Marland JRK, Pan D, Buttery PC. Rac GTPase-activating protein (Rac GAP) α1-Chimaerin undergoes proteasomal degradation and is stabilized by diacylglycerol signaling in neurons. J Biol Chem 2010; 286:199-207. [PMID: 21056981 DOI: 10.1074/jbc.m110.166728] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α1-Chimaerin is a neuron-specific member of the Rho GTPase-activating protein family that selectively inactivates the small GTPase Rac. It is known to regulate the structure of dendrites and dendritic spines. We describe here that under basal conditions α1-chimaerin becomes polyubiquitinated and undergoes rapid proteasomal degradation. This degradation is partly dependent on the N-terminal region that is unique to this isoform. Mimicking diacylglycerol (DAG) signaling with a phorbol ester stabilizes endogenous α1-chimaerin against degradation and causes accumulation of the protein. The stabilization requires phorbol ester binding via the C1 domain of the protein and is independent of PKC activity. In addition, overexpression of a constitutively active Rac1 mutant is sufficient to cause an accumulation of α1-chimaerin through a phospholipase C-dependent mechanism, showing that endogenous DAG signaling can also stabilize the protein. These results suggest that signaling via DAG may regulate the abundance of α1-chimaerin under physiological conditions, providing a new model for understanding how its activity could be controlled.
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Affiliation(s)
- Jamie R K Marland
- Centre for Brain Repair, University of Cambridge, Cambridge CB2 0PY, United Kingdom
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83
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Abstract
Neurons are highly specialized cells whose connectivity at synapses subserves rapid information transfer in the brain. Proper information processing, learning, and memory storage in the brain requires continuous remodeling of synaptic networks. Such remodeling includes synapse formation, elimination, synaptic protein turnover, and changes in synaptic transmission. An emergent mechanism for regulating synapse function is posttranslational modification through the ubiquitin pathway at the postsynaptic membrane. Here, we discuss recent findings implicating ubiquitination and protein degradation in postsynaptic function and plasticity. We describe postsynaptic ubiquitination pathways and their role in brain development, neuronal physiology, and brain disorders.
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Affiliation(s)
- Angela M Mabb
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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84
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Jakawich SK, Neely RM, Djakovic SN, Patrick GN, Sutton MA. An essential postsynaptic role for the ubiquitin proteasome system in slow homeostatic synaptic plasticity in cultured hippocampal neurons. Neuroscience 2010; 171:1016-31. [PMID: 20888892 DOI: 10.1016/j.neuroscience.2010.09.061] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 09/25/2010] [Accepted: 09/28/2010] [Indexed: 01/29/2023]
Abstract
Chronic increases or decreases in neuronal activity initiates compensatory changes in synaptic strength that emerge slowly over a 12-24 h period, but the mechanisms underlying this slow homeostatic response remain poorly understood. Here, we show an essential role for the ubiquitin proteasome system (UPS) in slow homeostatic plasticity induced by chronic changes in network activity. In cultured hippocampal neurons, UPS inhibitors drive a slow increase in miniature excitatory postsynaptic current (mEPSC) amplitude and synaptic AMPA receptor subunit GluA1 and GluA2 expression that both mirrors and occludes the changes produced by chronic suppression of network activity with tetrodotoxin (TTX). These non-additive effects were similarly observed under conditions of chronic hyperactivation of network activity with bicuculline--the increase in mEPSC amplitude and GluA1/2 expression with chronic UPS inhibition persists during network hyperactivation, which scales synaptic strength and AMPA receptor expression in the opposite direction when UPS activity is intact. Finally, cell-autonomous UPS inhibition (via expression of the ubiquitin chain elongation mutant, UbK48R) enhances mEPSC amplitude in a manner that mimics and occludes changes in network activity, demonstrating a postsynaptic role for the UPS in slow homeostatic plasticity. Taken together, our results suggest that the UPS acts as an integration point for translating sustained changes in network activity into appropriate incremental compensatory changes at synapses.
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Affiliation(s)
- S K Jakawich
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
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Sociability and motor functions in Shank1 mutant mice. Brain Res 2010; 1380:120-37. [PMID: 20868654 DOI: 10.1016/j.brainres.2010.09.026] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 09/03/2010] [Accepted: 09/03/2010] [Indexed: 02/07/2023]
Abstract
Autism is a neurodevelopmental disorder characterized by aberrant reciprocal social interactions, impaired communication, and repetitive behaviors. While the etiology remains unclear, strong evidence exists for a genetic component, and several synaptic genes have been implicated. SHANK genes encode a family of synaptic scaffolding proteins located postsynaptically on excitatory synapses. Mutations in SHANK genes have been detected in several autistic individuals. To understand the consequences of SHANK mutations relevant to the diagnostic and associated symptoms of autism, comprehensive behavioral phenotyping on a line of Shank1 mutant mice was conducted on multiple measures of social interactions, social olfaction, repetitive behaviors, anxiety-related behaviors, motor functions, and a series of control measures for physical abilities. Results from our comprehensive behavioral phenotyping battery indicated that adult Shank1 null mutant mice were similar to their wildtype and heterozygous littermates on standardized measures of general health, neurological reflexes and sensory skills. Motor functions were reduced in the null mutants on open field activity, rotarod, and wire hang, replicating and extending previous findings (Hung et al., 2008). A partial anxiety-like phenotype was detected in the null mutants in some components of the light ↔ dark task, as previously reported (Hung et al., 2008) but not in the elevated plus-maze. Juvenile reciprocal social interactions did not differ across genotypes. Interpretation of adult social approach was confounded by a lack of normal sociability in wildtype and heterozygous littermates. All genotypes were able to discriminate social odors on an olfactory habituation/dishabituation task. All genotypes displayed relatively high levels of repetitive self-grooming. Our findings support the interpretation that Shank1 null mice do not demonstrate autism-relevant social interaction deficits, but confirm and extend a role for Shank1 in motor functions.
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