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Tada H, Okano HJ, Takagi H, Shibata S, Yao I, Matsumoto M, Saiga T, Nakayama KI, Kashima H, Takahashi T, Setou M, Okano H. Fbxo45, a novel ubiquitin ligase, regulates synaptic activity. J Biol Chem 2009; 285:3840-3849. [PMID: 19996097 DOI: 10.1074/jbc.m109.046284] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurons communicate with each other through synapses. To establish the precise yet flexible connections that make up neural networks in the brain, continuous synaptic modulation is required. The ubiquitin-proteasome system of protein degradation is one of the critical mechanisms that underlie this process, playing crucial roles in the regulation of synaptic structure and function. We identified a novel ubiquitin ligase, Fbxo45, that functions at synapses. Fbxo45 is evolutionarily conserved and selectively expressed in the nervous system. We demonstrated that the knockdown of Fbxo45 in primary cultured hippocampal neurons resulted in a greater frequency of miniature excitatory postsynaptic currents. We also found that Fbxo45 induces the degradation of a synaptic vesicle-priming factor, Munc13-1. We propose that Fbxo45 plays an important role in the regulation of neurotransmission by modulating Munc13-1 at the synapse.
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Affiliation(s)
- Hirobumi Tada
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582; the Department of Physiology, Yokohama City University School of Medicine, Kanagawa 236-0004; the Bridgestone Laboratory of Developmental and Regenerative Neurobiology, Keio University School of Medicine, Tokyo 160-8582
| | - Hirotaka James Okano
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582; SORST (Solution Oriented Research for Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012.
| | - Hiroshi Takagi
- the Laboratory for Molecular Gerontology, Mitsubishi Kagaku Institute of Life Sciences Setou Group, Tokyo 194-8511
| | - Shinsuke Shibata
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582
| | - Ikuko Yao
- the Laboratory for Molecular Gerontology, Mitsubishi Kagaku Institute of Life Sciences Setou Group, Tokyo 194-8511
| | - Masaki Matsumoto
- the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; CREST (Core Research for Evolutional Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012
| | - Toru Saiga
- the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; CREST (Core Research for Evolutional Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012
| | - Keiichi I Nakayama
- the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; CREST (Core Research for Evolutional Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012
| | - Haruo Kashima
- the Department of Neuropsychiatry, Keio University School of Medicine, Tokyo 160-8582
| | - Takuya Takahashi
- the Department of Physiology, Yokohama City University School of Medicine, Kanagawa 236-0004
| | - Mitsutoshi Setou
- the Laboratory for Molecular Gerontology, Mitsubishi Kagaku Institute of Life Sciences Setou Group, Tokyo 194-8511; the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; the Department of Molecular Anatomy, Hamamatsu University School of Medicine, Shizuoka 431-3192, Japan.
| | - Hideyuki Okano
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582; the Bridgestone Laboratory of Developmental and Regenerative Neurobiology, Keio University School of Medicine, Tokyo 160-8582; SORST (Solution Oriented Research for Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012.
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Fbxo45 forms a novel ubiquitin ligase complex and is required for neuronal development. Mol Cell Biol 2009; 29:3529-43. [PMID: 19398581 DOI: 10.1128/mcb.00364-09] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fbxo45 is an F-box protein that is restricted to the nervous system. Unlike other F-box proteins, Fbxo45 was found not to form an SCF complex as a result of an amino acid substitution in the consensus sequence for Cul1 binding. Proteomics analysis revealed that Fbxo45 specifically associates with PAM (protein associated with Myc), a RING finger-type ubiquitin ligase. Mice deficient in Fbxo45 were generated and found to die soon after birth as a result of respiratory distress. Fbxo45(-)(/)(-) embryos show abnormal innervation of the diaphragm, impaired synapse formation at neuromuscular junctions, and aberrant development of axon fiber tracts in the brain. Similar defects are also observed in mice lacking Phr1 (mouse ortholog of PAM), suggesting that Fbxo45 and Phr1 function in the same pathway. In addition, neuronal migration was impaired in Fbxo45(-)(/)(-) mice. These results suggest that Fbxo45 forms a novel Fbxo45-PAM ubiquitin ligase complex that plays an important role in neural development.
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Think locally: control of ubiquitin-dependent protein degradation in neurons. EMBO Rep 2008; 10:44-50. [PMID: 19079132 DOI: 10.1038/embor.2008.229] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 11/13/2008] [Indexed: 11/08/2022] Open
Abstract
The nervous system coordinates many aspects of body function such as learning, memory, behaviour and locomotion. Therefore, it must develop and maintain an intricate network of differentiated neuronal cells, which communicate efficiently with each other and with non-neuronal target cells. Unlike most somatic cells, differentiated neurons are post-mitotic and characterized by a highly polarized morphology that determines the flow of information. Among other post-translational modifications, the ubiquitination of specific protein substrates was recently shown to have a crucial role in the regulation of neuronal development and differentiation. Here, we review recent findings that illustrate the mechanisms that mediate the temporal and spatial control of neuronal protein turnover by the ubiquitin-proteasome system (UPS), which is crucial for the development and function of the nervous system.
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Abstract
Information processing in the nervous system relies on properly localized and organized synaptic structures at the correct locations. The formation of synapses is a long and intricate process involving multiple interrelated steps. Decades of research have identified a large number of molecular components of the presynaptic compartment. In addition to neurotransmitter-containing synaptic vesicles, presynaptic terminals are defined by cytoskeletal and membrane specializations that allow highly regulated exo- and endocytosis of synaptic vesicles and that maintain precise registration with postsynaptic targets. Functional studies at multiple levels have revealed complex interactions between the transport of vesicular intermediates, the presynaptic cytoskeleton, growth cone navigation, and synaptic targets. With the advent of finer anatomical, physiological, and molecular tools, great insights have been gained toward the mechanistic dissection of functionally redundant processes controlling the specificity and dynamics of synapses. This review highlights the recent findings pertaining to the cellular and molecular regulation of presynaptic differentiation.
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Affiliation(s)
- Yishi Jin
- Division of Biological Sciences, Section of Neurobiology, Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California 92093, USA.
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56
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Ding M, Shen K. The role of the ubiquitin proteasome system in synapse remodeling and neurodegenerative diseases. Bioessays 2008; 30:1075-83. [PMID: 18937340 DOI: 10.1002/bies.20843] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The ubiquitin proteasome system is a potent regulatory mechanism used to control protein stability in numerous cellular processes, including neural development. Many neurodegenerative diseases are featured by the accumulation of UPS-associated proteins, suggesting the UPS dysfunction may be crucial for pathogenesis. Recent experiments have highlighted the UPS as a key player during synaptic development. Here we summarize recent discoveries centered on the role of the UPS in synapse remodeling and draw attention to the potential link between the synaptic UPS dysfunction and the pathology of neurodegenerative diseases.
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Affiliation(s)
- Mei Ding
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
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A mechanism distinct from highwire for the Drosophila ubiquitin conjugase bendless in synaptic growth and maturation. J Neurosci 2008; 28:8615-23. [PMID: 18716220 DOI: 10.1523/jneurosci.2990-08.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The signaling mechanisms that allow the conversion of a growth cone into a mature and stable synapse are yet to be completely understood. Ubiquitination plays key regulatory roles in synaptic development and may be involved in this process. Previous studies identified the Drosophila ubiquitin conjugase bendless (ben) to be important for central synapse formation, but the precise role it plays has not been elucidated. Our studies indicate that Ben plays a pivotal role in synaptic growth and maturation. We have determined that an incipient synapse is present with a high penetrance in ben mutants, suggesting that Ben is required for a developmental step after target recognition. We used cell-autonomous rescue experiments to show that Ben has a presynaptic role in synapse growth. We then harnessed the TARGET system to transiently express UAS (upstream activating sequence)-ben in a ben mutant background and identified a well defined critical period for Ben function in establishing a full-grown, mature synaptic terminal. We demonstrate that the protein must be present at a time point before but not during the actual growth process. We also provide phenotypic evidence demonstrating that Ben is not a part of the signal transduction pathway involving the well characterized ubiquitin ligase highwire. We conclude that Bendless functions as a novel developmental switch that permits the transition from axonal growth and incipient synapse formation to synaptic growth and maturation in the CNS.
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Hadjebi O, Casas-Terradellas E, Garcia-Gonzalo FR, Rosa JL. The RCC1 superfamily: From genes, to function, to disease. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1467-79. [DOI: 10.1016/j.bbamcr.2008.03.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Revised: 03/19/2008] [Accepted: 03/20/2008] [Indexed: 02/07/2023]
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Abstract
The formation of the nervous system during embryonic development is controlled by a complex network of signaling pathways which ensure proper migration and targeting of neuronal projections. Likewise, the function of the adult nervous system relies on complex dynamic interactions between the presynaptic and postsynaptic terminals. Here, we review recent advances in understanding the molecular pathways underlying these seemingly distinct processes. These studies reveal that the conserved E3 ubiquitin ligase PHR (PAM, highwire Rpm-1) controls a regulatory protein degradation pathway essential both for axonal targeting during embryonic development as well as for the proper formation and function of neuron muscular junctions (NMJ).
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Affiliation(s)
- Tudor A Fulga
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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Abrams B, Grill B, Huang X, Jin Y. Cellular and molecular determinants targeting the Caenorhabditis elegans PHR protein RPM-1 to perisynaptic regions. Dev Dyn 2008; 237:630-9. [PMID: 18224716 PMCID: PMC2657606 DOI: 10.1002/dvdy.21446] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Caenorhabditis elegans RPM-1 is a member of a conserved protein family, the PHR proteins, that includes human Pam, mouse Phr1, zebrafish Esrom, and Drosophila Highwire. PHR proteins play important roles in the development of the nervous system. In particular, mutations in rpm-1 cause a disruption of synaptic architecture, affecting the distribution of synaptic vesicles and the number of presynaptic densities. Using antibodies against RPM-1, we determined the localization of the endogenous RPM-1 protein in wild-type and in several mutants that affect synaptic development. Our analyses show that, in mature neurons, RPM-1 resides in a distinct region that is close to, but does not overlap with, the synaptic exo- and endocytosis domains. The localization of RPM-1 occurs independently of several proteins that function in the transport or assembly of synapse components, and its abundance is partially dependent on its binding partner the F-box protein FSN-1. RPM-1 has been shown to target the MAPKKK DLK-1 for degradation. We show that activated DLK-1 may be preferentially targeted for degradation. Furthermore, using transgene analysis, we identified a critical role of the conserved PHR domain of RPM-1 in its subcellular localization.
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Affiliation(s)
- Benjamin Abrams
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Laboratories, University of California Santa Cruz, CA 95064, USA
| | - Brock Grill
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Laboratories, University of California Santa Cruz, CA 95064, USA
| | - Xun Huang
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Laboratories, University of California Santa Cruz, CA 95064, USA
| | - Yishi Jin
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Laboratories, University of California Santa Cruz, CA 95064, USA
- Howard Hughes Medical Institute, University of California San Diego, CA 92093, USA
- Division of Biological Sciences, Section of Neurobiology, University of California San Diego, CA 92093, USA
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Fly neurobiology: development and function of the brain. Meeting on the Neurobiology of Drosophila. EMBO Rep 2008; 9:239-42. [PMID: 18259217 DOI: 10.1038/embor.2008.13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Accepted: 01/16/2008] [Indexed: 11/09/2022] Open
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Haas KF, Broadie K. Roles of ubiquitination at the synapse. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1779:495-506. [PMID: 18222124 DOI: 10.1016/j.bbagrm.2007.12.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 12/19/2007] [Accepted: 12/27/2007] [Indexed: 12/13/2022]
Abstract
The ubiquitin proteasome system (UPS) was first described as a mechanism for protein degradation more than three decades ago, but the critical roles of the UPS in regulating neuronal synapses have only recently begun to be revealed. Targeted ubiquitination of synaptic proteins affects multiple facets of the synapse throughout its life cycle; from synaptogenesis and synapse elimination to activity-dependent synaptic plasticity and remodeling. The recent identification of specific UPS molecular pathways that act locally at the synapse illustrates the exquisite specificity of ubiquitination in regulating synaptic protein trafficking and degradation events. Synaptic activity has also been shown to determine the subcellular distribution and composition of the proteasome, providing additional mechanisms for locally regulating synaptic protein degradation. Together these advances reveal that tight control of protein turnover plays a conserved, central role in establishing and modulating synapses in neural circuits.
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Affiliation(s)
- Kevin F Haas
- Department of Neurology, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235-1634, USA
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