101
|
Abstract
The proteolytic machinery comprising metalloproteases and γ-secretase, an intramembrane aspartyl protease involved in Alzheimer's disease, cleaves several substrates in addition to the extensively studied amyloid precursor protein. Some of these substrates, such as N-cadherin, are synaptic proteins involved in synapse remodeling and maintenance. Here we show, in rats and mice, that metalloproteases and γ-secretase are physiologic regulators of synapses. Both proteases are synaptic, with γ-secretase tethered at the synapse by δ-catenin, a synaptic scaffolding protein that also binds to N-cadherin and, through scaffolds, to AMPA receptor and a metalloprotease. Activity-dependent proteolysis by metalloproteases and γ-secretase takes place at both sides of the synapse, with the metalloprotease cleavage being NMDA receptor-dependent. This proteolysis decreases levels of synaptic proteins and diminishes synaptic transmission. Our results suggest that activity-dependent substrate cleavage by synaptic metalloproteases and γ-secretase modifies synaptic transmission, providing a novel form of synaptic autoregulation.
Collapse
|
102
|
Schwarz LA, Patrick GN. Ubiquitin-dependent endocytosis, trafficking and turnover of neuronal membrane proteins. Mol Cell Neurosci 2011; 49:387-93. [PMID: 21884797 DOI: 10.1016/j.mcn.2011.08.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 08/15/2011] [Indexed: 02/07/2023] Open
Abstract
Extracellular signaling between cells is often transduced via receptors that reside at the cell membrane. In neurons this receptor-mediated signaling can promote a variety of cellular events such as differentiation, axon outgrowth and guidance, and synaptic development and function. Endocytic membrane trafficking of receptors ensures that the strength and duration of an extracellular signal is properly regulated. The covalent modification of membrane proteins by ubiquitin is a key biological mechanism controlling receptor internalization and endocytic sorting to recycling and degradative pathways in many cell types. In this review we highlight recent findings regarding the ubiquitin-dependent trafficking and turnover of receptors in neurons and the implications for neuronal development and function.
Collapse
Affiliation(s)
- Lindsay A Schwarz
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | | |
Collapse
|
103
|
Todi SV, Paulson HL. Balancing act: deubiquitinating enzymes in the nervous system. Trends Neurosci 2011; 34:370-82. [PMID: 21704388 DOI: 10.1016/j.tins.2011.05.004] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 05/05/2011] [Accepted: 05/09/2011] [Indexed: 01/03/2023]
Abstract
Many pathways important to the nervous system are regulated by the post-translational conjugation of ubiquitin to target proteins. The reversal of ubiquitination, or deubiquitination, is equally critical to neuronal function. By countering protein ubiquitination, deubiquitinating enzymes (DUBs) help control neuronal fate determination, axonal pathfinding and synaptic communication and plasticity. The significance of DUBs to the nervous system is underscored by links to various neurological diseases. Owing to cell type or substrate specificity, certain DUBs might also represent therapeutic targets for neurodegeneration. Here, we review recent findings that have shaped our current understanding of emerging functions for DUBs in the nervous system.
Collapse
Affiliation(s)
- Sokol V Todi
- Wayne State University School of Medicine, Department of Pharmacology and Department of Neurology, 540 E Canfield, Scott Hall Room 6105, Detroit, Michigan 48201, USA
| | | |
Collapse
|
104
|
The deubiquitinating enzyme USP-46 negatively regulates the degradation of glutamate receptors to control their abundance in the ventral nerve cord of Caenorhabditis elegans. J Neurosci 2011; 31:1341-54. [PMID: 21273419 DOI: 10.1523/jneurosci.4765-10.2011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Ubiquitin-mediated endocytosis and post-endocytic trafficking of glutamate receptors control their synaptic abundance and are implicated in modulating synaptic strength. Ubiquitination is a reversible modification, but the identities and specific functions of deubiquitinating enzymes in the nervous system are lacking. Here, we show that the deubiquitinating enzyme ubiquitin-specific protease-46 (USP-46) regulates the abundance of the glutamate receptor GLR-1 in the ventral nerve cord of Caenorhabditis elegans. Mutants lacking usp-46 have decreased GLR-1 in the ventral nerve cord and corresponding defects in GLR-1-dependent behaviors. The amount of ubiquitinated GLR-1 is increased in usp-46 mutants. Mutations that block GLR-1 ubiquitination or receptor degradation in the multi-vesicular body/lysosome prevent the decrease in GLR-1 observed in usp-46 mutants. These data support a model in which USP-46 promotes GLR-1 abundance at synapses by deubiquitinating GLR-1 and preventing its degradation in the lysosome. This work suggests that the balance between the addition and removal of ubiquitin is important for glutamate receptor trafficking.
Collapse
|
105
|
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.
Collapse
Affiliation(s)
- Baris Bingol
- Department of Neuroscience, Genentech, Inc., South San Francisco, CA 94080, USA
| | | |
Collapse
|
106
|
Prasad K, Tarasewicz E, Strickland PAO, O’Neill M, Mitchell SN, Merchant K, Tep S, Hilton K, Datwani A, Buttini M, Mueller-Steiner S, Richfield EK. Biochemical and morphological consequences of human α-synuclein expression in a mouse α-synuclein null background. Eur J Neurosci 2011; 33:642-56. [PMID: 21272100 PMCID: PMC3072281 DOI: 10.1111/j.1460-9568.2010.07558.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A consensus about the functions of human wild-type or mutated α-synuclein (αSYN) is lacking. Both forms of αSYN are implicated in Parkinson's disease, whereas the wild-type form is implicated in substance abuse. Interactions with other cellular proteins and organelles may meditate its functions. We developed a series of congenic mouse lines containing various allele doses or combinations of the human wild-type αSYN (hwαSYN) or a doubly mutated (A30P*A53T) αSYN (hm(2) αSYN) in a C57Bl/6J line spontaneously deleted in mouse αSYN (C57BL/6JOla). Both transgenes had a functional role in the nigrostriatal system, demonstrated by significant elevations in striatal catecholamines, metabolites and the enzyme tyrosine hydroxylase compared with null-mice without a transgene. Consequences occurred when the transgenes were expressed at a fraction of the endogenous level. Hemizygous congenic mice did not exhibit any change in the number or size of dopaminergic neurons in the ventral midbrain at 9 months of age. Human αSYN was predominantly located in neuronal cell bodies, neurites, synapses, and in intraneuronal/intraneuritic aggregates. The hm(2) αSYN transgene resulted in more aggregates and dystrophic neurites than did the hw5 transgene. The hwαSYN transgene resulted in higher expression of two striatal proteins, synaptogamin 7 and UCHL1, compared with the levels of the hm(2) αSYN transgene. These observations suggest that mutations in αSYN may impair specific functional domains, leaving others intact. These lines may be useful for exploring interactions between hαSYN and environmental or genetic risk factors in dopamine-related disorders using a mouse model.
Collapse
Affiliation(s)
- Kavita Prasad
- Department of Pathology and Lab Medicine Robert Wood Johnson Medical School (RWJMS), University of Medicine and Dentistry New Jersey (UMDNJ), Piscataway, NJ 08854
- Environmental and Occupational Health Sciences Institute (EOHSI), Piscataway, NJ 08854
| | - Elizabeth Tarasewicz
- Department of Pathology and Lab Medicine Robert Wood Johnson Medical School (RWJMS), University of Medicine and Dentistry New Jersey (UMDNJ), Piscataway, NJ 08854
- Environmental and Occupational Health Sciences Institute (EOHSI), Piscataway, NJ 08854
| | - Pamela A. Ohman Strickland
- Environmental and Occupational Health Sciences Institute (EOHSI), Piscataway, NJ 08854
- Department of Biostatistics, School of Public Health, University of Medicine and Dentistry New Jersey (UMDNJ), Piscataway, NJ 08854
| | | | | | | | - Samnang Tep
- Elan Pharmaceuticals Inc., South San Francisco, CA 94080
| | - Kathryn Hilton
- Elan Pharmaceuticals Inc., South San Francisco, CA 94080
| | - Akash Datwani
- Elan Pharmaceuticals Inc., South San Francisco, CA 94080
| | - Manuel Buttini
- Elan Pharmaceuticals Inc., South San Francisco, CA 94080
| | | | - Eric K. Richfield
- Department of Pathology and Lab Medicine Robert Wood Johnson Medical School (RWJMS), University of Medicine and Dentistry New Jersey (UMDNJ), Piscataway, NJ 08854
- Environmental and Occupational Health Sciences Institute (EOHSI), Piscataway, NJ 08854
| |
Collapse
|
107
|
Andersson FI, Werrell EF, McMorran L, Crone WJK, Das C, Hsu STD, Jackson SE. The effect of Parkinson's-disease-associated mutations on the deubiquitinating enzyme UCH-L1. J Mol Biol 2011; 407:261-72. [PMID: 21251915 DOI: 10.1016/j.jmb.2010.12.029] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 10/18/2022]
Abstract
The neuronal ubiquitin C-terminal hydrolase (UCH) UCH-L1 has been linked to Parkinson's disease (PD) and other neurodegenerative diseases. Here, we present a study on the structure, stability, unfolding, and dynamics of wild-type and mutant UCH-L1. Fluorescence, far-UV CD, and NMR measurements were used to establish that the unfolding of UCH-L1 is three-state under equilibrium conditions and that an intermediate is populated. S18Y and I93M mutants, which are associated with a decreased risk or an increased risk of PD, respectively, are less stable than wild type. However, while there is minimal structural perturbation in the S18Y mutant, the I93M mutation is more disruptive. In particular, the NMR data suggest that there are local rearrangements around the site of the mutation, which we propose results in the exposure of hydrophobic surface area. This may have two consequences: an increased tendency towards, firstly, aggregation in vivo, and, secondly, aberrant interactions with tubulin and the chaperone-mediated autophagy machinery as observed by other groups, both of which may be involved in neurodegenerative processes.
Collapse
|
108
|
XIE M, CHEN QC, LIAO XM. The Protective Effects of Ubiquitin C-Terminal Hydrolase L1 on Neurons*. PROG BIOCHEM BIOPHYS 2010. [DOI: 10.3724/sp.j.1206.2010.00253] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
109
|
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.
Collapse
Affiliation(s)
- Angela M Mabb
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
| | | |
Collapse
|
110
|
Li A, Choi YS, Dziema H, Cao R, Cho HY, Jung YJ, Obrietan K. Proteomic profiling of the epileptic dentate gyrus. Brain Pathol 2010; 20:1077-89. [PMID: 20608933 DOI: 10.1111/j.1750-3639.2010.00414.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The development of epilepsy is often associated with marked changes in central nervous system cell structure and function. Along these lines, reactive gliosis and granule cell axonal sprouting within the dentate gyrus of the hippocampus are commonly observed in individuals with temporal lobe epilepsy (TLE). Here we used the pilocarpine model of TLE in mice to screen the proteome and phosphoproteome of the dentate gyrus to identify molecular events that are altered as part of the pathogenic process. Using a two-dimensional gel electrophoresis-based approach, followed by liquid chromatography-tandem mass spectrometry, 24 differentially expressed proteins, including 9 phosphoproteins, were identified. Functionally, these proteins were organized into several classes, including synaptic physiology, cell structure, cell stress, metabolism and energetics. The altered expression of three proteins involved in synaptic physiology, actin, profilin 1 and α-synuclein was validated by secondary methods. Interestingly, marked changes in protein expression were detected in the supragranular cell region, an area where robust mossy fibers sprouting occurs. Together, these data provide new molecular insights into the altered protein profile of the epileptogenic dentate gyrus and point to potential pathophysiologic mechanisms underlying epileptogenesis.
Collapse
Affiliation(s)
- Aiqing Li
- Key Lab. for Organ Failure Research, Education Ministry of P.R. China, Southern Medical University, Guangzhou, China
| | | | | | | | | | | | | |
Collapse
|
111
|
Ubiquitin carboxyl-terminal hydrolase L1 is required for maintaining the structure and function of the neuromuscular junction. Proc Natl Acad Sci U S A 2010; 107:1636-41. [PMID: 20080621 DOI: 10.1073/pnas.0911516107] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The enzyme ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is one of the most abundant proteins in the mammalian nervous system. In humans, UCH-L1 is also found in the ubiquitinated inclusion bodies that characterize neurodegenerative diseases in the brain, suggesting its involvement in neurodegeneration. The physiologic role of UCH-L1 in neurons, however, remains to be further elucidated. For example, previous studies have provided evidence both for and against the role of UCH-L1 in synaptic function in the brain. Here, we have characterized a line of knockout mice deficient in the UCH-L1 gene. We found that, in the absence of UCH-L1, synaptic transmission at the neuromuscular junctions (NMJs) is markedly impaired. Both spontaneous and evoked synaptic activity are reduced; paired pulse-facilitation is impaired, and synaptic transmission fails to respond to high-frequency, repetitive stimulation at the NMJs of UCH-L1 knockout mice. Morphologic analyses of the NMJs further revealed profound structural defects-loss of synaptic vesicles and accumulation of tubulovesicular structures at the presynaptic nerve terminals, and denervation of the muscles in UCH-L1 knockout mice. These findings demonstrate that UCH-L1 is required for the maintenance of the structure and function of the NMJ and that the loss of normal UCH-L1 activity may result in neurodegeneration in the peripheral nervous system.
Collapse
|
112
|
Manadas B, Santos AR, Szabadfi K, Gomes JR, Garbis SD, Fountoulakis M, Duarte CB. BDNF-Induced Changes in the Expression of the Translation Machinery in Hippocampal Neurons: Protein Levels and Dendritic mRNA. J Proteome Res 2009; 8:4536-52. [DOI: 10.1021/pr900366x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Bruno Manadas
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| | - Ana Rita Santos
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| | - Krisztina Szabadfi
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| | - João R. Gomes
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| | - Spiros D. Garbis
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| | - Michael Fountoulakis
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| | - Carlos B. Duarte
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal, and Foundation for Biomedical Research of the Academy of Athens, Athens, Greece
| |
Collapse
|