101
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Ni CL, Seth D, Fonseca FV, Wang L, Xiao TS, Gruber P, Sy MS, Stamler JS, Tartakoff AM. Polyglutamine Tract Expansion Increases S-Nitrosylation of Huntingtin and Ataxin-1. PLoS One 2016; 11:e0163359. [PMID: 27658206 PMCID: PMC5033456 DOI: 10.1371/journal.pone.0163359] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 09/07/2016] [Indexed: 11/19/2022] Open
Abstract
Expansion of the polyglutamine (polyQ) tract in the huntingtin (Htt) protein causes Huntington’s disease (HD), a fatal inherited movement disorder linked to neurodegeneration in the striatum and cortex. S-nitrosylation and S-acylation of cysteine residues regulate many functions of cytosolic proteins. We therefore used a resin-assisted capture approach to identify these modifications in Htt. In contrast to many proteins that have only a single S-nitrosylation or S-acylation site, we identified sites along much of the length of Htt. Moreover, analysis of cells expressing full-length Htt or a large N-terminal fragment of Htt shows that polyQ expansion strongly increases Htt S-nitrosylation. This effect appears to be general since it is also observed in Ataxin-1, which causes spinocerebellar ataxia type 1 (SCA1) when its polyQ tract is expanded. Overexpression of nitric oxide synthase increases the S-nitrosylation of normal Htt and the frequency of conspicuous juxtanuclear inclusions of Htt N-terminal fragments in transfected cells. Taken together with the evidence that S-nitrosylation of Htt is widespread and parallels polyQ expansion, these subcellular changes show that S-nitrosylation affects the biology of this protein in vivo.
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Affiliation(s)
- Chun-Lun Ni
- Cell Biology Program, Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Divya Seth
- Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Fabio Vasconcelos Fonseca
- Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Liwen Wang
- Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Tsan Sam Xiao
- Department of Pathology, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Phillip Gruber
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Man-Sun Sy
- Department of Pathology, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Jonathan S. Stamler
- Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, 44106, United States of America
| | - Alan M. Tartakoff
- Cell Biology Program, Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH, 44106, United States of America
- Department of Pathology, Case Western Reserve University, Cleveland, OH, 44106, United States of America
- * E-mail:
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102
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Lin L, Jin Z, Tan H, Xu Q, Peng T, Li H. Atypical ubiquitination by E3 ligase WWP1 inhibits the proteasome-mediated degradation of mutant huntingtin. Brain Res 2016; 1643:103-12. [PMID: 27107943 DOI: 10.1016/j.brainres.2016.03.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/10/2016] [Accepted: 03/18/2016] [Indexed: 11/19/2022]
Abstract
Huntington's disease (HD) is caused by the expansion of CAG trinucleotide repeats in exon 1 of HD gene encoding huntingtin (Htt), which is characterized by aggregation and formation of mutant Htt containing expanded polyglutamine (polyQ) repeats. Dysfunction of the ubiquitin-proteasome system (UPS) plays a critical role in the pathogenesis of HD. As the linkage mediator between ubiquitin and specific target proteins, E3 ubiquitin ligases have been suggested to be involved in mHtt degradation and HD pathology. However, the potential involvement of the E3 ligase WWP1 in HD has not been explored. The present study determined whether WWP1 is involved in the development of HD in both in vivo and in vitro models. The results showed that in contrast to several other E3 ligases, expression of WWP1 is enhanced in mice and N2a cells expressing mutant Htt (160Q) and co-localized with mHtt protein aggregates. In addition, expression of WWP1 positively regulates mutan Htt levels, aggregate formation, and cell toxicity. Further analysis revealed that WWP1 ubiquitinated mHtt at an atypical position of Lys-63, which may have inhibited degradation of mutant Htt through the ubiquitin-proteasome pathway. In conclusion, these results suggested that the E3 ligase WWP1 is involved in the pathogenesis of HD; therefore, it may be a novel target for therapeutic intervention.
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Affiliation(s)
- Li Lin
- Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Zhenzhen Jin
- Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Huiping Tan
- Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Qiaoqiao Xu
- Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Ting Peng
- Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China; (b)Key Laboratory for Neurological Disorders of Education Ministry,Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China; (c)Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China.
| | - He Li
- Division of Histology and Embryology, Department of Anatomy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China; (b)Key Laboratory for Neurological Disorders of Education Ministry,Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China; (c)Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China.
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103
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Arndt JR, Chaibva M, Legleiter J. The emerging role of the first 17 amino acids of huntingtin in Huntington's disease. Biomol Concepts 2016; 6:33-46. [PMID: 25741791 DOI: 10.1515/bmc-2015-0001] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 02/09/2015] [Indexed: 01/01/2023] Open
Abstract
Huntington's disease (HD) is caused by a polyglutamine (polyQ) domain that is expanded beyond a critical threshold near the N-terminus of the huntingtin (htt) protein, directly leading to htt aggregation. While full-length htt is a large (on the order of ∼350 kDa) protein, it is proteolyzed into a variety of N-terminal fragments that accumulate in oligomers, fibrils, and larger aggregates. It is clear that polyQ length is a key determinant of htt aggregation and toxicity. However, the flanking sequences around the polyQ domain, such as the first 17 amino acids on the N terminus (Nt17), influence aggregation, aggregate stability, influence other important biochemical properties of the protein and ultimately its role in pathogenesis. Here, we review the impact of Nt17 on htt aggregation mechanisms and kinetics, structural properties of Nt17 in both monomeric and aggregate forms, the potential role of posttranslational modifications (PTMs) that occur in Nt17 in HD, and the function of Nt17 as a membrane targeting domain.
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104
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Chondrogianni N, Voutetakis K, Kapetanou M, Delitsikou V, Papaevgeniou N, Sakellari M, Lefaki M, Filippopoulou K, Gonos ES. Proteasome activation: An innovative promising approach for delaying aging and retarding age-related diseases. Ageing Res Rev 2015; 23:37-55. [PMID: 25540941 DOI: 10.1016/j.arr.2014.12.003] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/09/2014] [Accepted: 12/15/2014] [Indexed: 11/16/2022]
Abstract
Aging is a natural process accompanied by a progressive accumulation of damage in all constituent macromolecules (nucleic acids, lipids and proteins). Accumulation of damage in proteins leads to failure of proteostasis (or vice versa) due to increased levels of unfolded, misfolded or aggregated proteins and, in turn, to aging and/or age-related diseases. The major cellular proteolytic machineries, namely the proteasome and the lysosome, have been shown to dysfunction during aging and age-related diseases. Regarding the proteasome, it is well established that it can be activated either through genetic manipulation or through treatment with natural or chemical compounds that eventually result to extension of lifespan or deceleration of the progression of age-related diseases. This review article focuses on proteasome activation studies in several species and cellular models and their effects on aging and longevity. Moreover, it summarizes findings regarding proteasome activation in the major age-related diseases as well as in progeroid syndromes.
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Affiliation(s)
- Niki Chondrogianni
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece.
| | - Konstantinos Voutetakis
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Marianna Kapetanou
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Vasiliki Delitsikou
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Nikoletta Papaevgeniou
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Marianthi Sakellari
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece; Örebro University, Medical School, Örebro, Sweden
| | - Maria Lefaki
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Konstantina Filippopoulou
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece
| | - Efstathios S Gonos
- National Hellenic Research Foundation, Institute of Biology, Medicinal Chemistry and Biotechnology, 48 Vas. Constantinou Ave., 116 35 Athens, Greece; Örebro University, Medical School, Örebro, Sweden.
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105
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Abstract
Autophagy is a major degradation system which processes substrates through the steps of autophagosome formation, autophagosome-lysosome fusion, and substrate degradation. Aberrant autophagic flux is present in many pathological conditions including neurodegeneration and tumors. CHIP/STUB1, an E3 ligase, plays an important role in neurodegeneration. In this study, we identified the regulation of autophagic flux by CHIP (carboxy-terminus of Hsc70-interacting protein). Knockdown of CHIP induced autophagosome formation through increasing the PTEN protein level and decreasing the AKT/mTOR activity as well as decreasing phosphorylation of ULK1 on Ser757. However, degradation of the autophagic substrate p62 was disturbed by knockdown of CHIP, suggesting an abnormality of autophagic flux. Furthermore, knockdown of CHIP increased the susceptibility of cells to autophagic cell death induced by bafilomycin A1. Thus, our data suggest that CHIP plays roles in the regulation of autophagic flux.
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106
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Li X, Liu H, Fischhaber PL, Tang TS. Toward therapeutic targets for SCA3: Insight into the role of Machado-Joseph disease protein ataxin-3 in misfolded proteins clearance. Prog Neurobiol 2015; 132:34-58. [PMID: 26123252 DOI: 10.1016/j.pneurobio.2015.06.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 05/30/2015] [Accepted: 06/16/2015] [Indexed: 01/09/2023]
Abstract
Machado-Joseph disease (MJD, also known as spinocerebellar ataxia type 3, SCA3), an autosomal dominant neurological disorder, is caused by an abnormal expanded polyglutamine (polyQ) repeat in the ataxin-3 protein. The length of the expanded polyQ stretch correlates positively with the severity of the disease and inversely with the age at onset. To date, we cannot fully explain the mechanism underlying neurobiological abnormalities of this disease. Yet, accumulating reports have demonstrated the functions of ataxin-3 protein in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, all of which suggest a role of ataxin-3 in the clearance of misfolded proteins. Notably, the SCA3 pathogenic form of ataxin-3 (ataxin-3(exp)) impairs the misfolded protein clearance via mechanisms that are either dependent or independent of its deubiquitinase (DUB) activity, resulting in the accumulation of misfolded proteins and the progressive loss of neurons in SCA3. Some drugs, which have been used as activators/inducers in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, have been demonstrated to be efficacious in the relief of neurodegeneration diseases like Huntington's disease (HD), Parkinson's (PD), Alzheimer's (AD) as well as SCA3 in animal models and clinical trials, putting misfolded protein clearance on the list of potential therapeutic targets. Here, we undertake a comprehensive review of the progress in understanding the physiological functions of ataxin-3 in misfolded protein clearance and how the polyQ expansion impairs misfolded protein clearance. We then detail the preclinical studies targeting the elimination of misfolded proteins for SCA3 treatment. We close with future considerations for translating these pre-clinical results into therapies for SCA3 patients.
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Affiliation(s)
- Xiaoling Li
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Hongmei Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
| | - Paula L Fischhaber
- Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330-8262, USA.
| | - Tie-Shan Tang
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China.
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107
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Almeida B, Abreu IA, Matos CA, Fraga JS, Fernandes S, Macedo MG, Gutiérrez-Gallego R, Pereira PJB, Carvalho AL, Macedo-Ribeiro S. SUMOylation of the brain-predominant Ataxin-3 isoform modulates its interaction with p97. Biochim Biophys Acta Mol Basis Dis 2015; 1852:1950-9. [PMID: 26073430 DOI: 10.1016/j.bbadis.2015.06.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 05/12/2015] [Accepted: 06/08/2015] [Indexed: 11/18/2022]
Abstract
BACKGROUND Machado-Joseph Disease (MJD), a form of dominantly inherited ataxia belonging to the group of polyQ expansion neurodegenerative disorders, occurs when a threshold value for the number of glutamines in Ataxin-3 (Atx3) polyglutamine region is exceeded. As a result of its modular multidomain architecture, Atx3 is known to engage in multiple macromolecular interactions, which might be unbalanced when the polyQ tract is expanded, culminating in the aggregation and formation of intracellular inclusions, a unifying fingerprint of this group of neurodegenerative disorders. Since aggregation is specific to certain brain regions, localization-dependent posttranslational modifications that differentially affect Atx3 might also contribute for MJD. METHODS We combined in vitro and cellular approaches to address SUMOylation in the brain-predominant Atx3 isoform and assessed the impact of this posttranslational modification on Atx3 self-assembly and interaction with its native partner, p97. RESULTS We demonstrate that Atx3 is SUMOylated at K356 both in vitro and in cells, which contributes for decreased formation of amyloid fibrils and for increased affinity towards p97. CONCLUSIONS AND GENERAL SIGNIFICANCE These findings highlight the role of SUMOylation as a regulator of Atx3 function, with implications on Atx3 protein interaction network and self-assembly, with potential impact for further understanding the molecular mechanisms underlying MJD pathogenesis.
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Affiliation(s)
- Bruno Almeida
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Isabel A Abreu
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Carlos A Matos
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Joana S Fraga
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Sara Fernandes
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Maria G Macedo
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Ricardo Gutiérrez-Gallego
- Bioanalysis Group, Neurosciences Research Program, Hospital del Mar Medical Research Institute (IMIM)-Parque de Salud Mar, 08003 Barcelona, Spain; Department of Experimental and Health Sciences, Pompeu Fabra University, 08003 Barcelona, Spain
| | - Pedro José Barbosa Pereira
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal
| | - Ana Luísa Carvalho
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Sandra Macedo-Ribeiro
- IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4150-180 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Portugal.
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108
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Hearst SM, Shao Q, Lopez M, Raucher D, Vig PJS. Focused cerebellar laser light induced hyperthermia improves symptoms and pathology of polyglutamine disease SCA1 in a mouse model. THE CEREBELLUM 2015; 13:596-606. [PMID: 24930030 DOI: 10.1007/s12311-014-0576-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Spinocerebellar ataxia 1 (SCA1) results from pathologic glutamine expansion in the ataxin-1 protein (ATXN1). This misfolded ATXN1 causes severe Purkinje cell (PC) loss and cerebellar ataxia in both humans and mice with the SCA1 disease. The molecular chaperone heat-shock proteins (HSPs) are known to modulate polyglutamine protein aggregation and are neuroprotective. Since HSPs are induced under stress, we explored the effects of focused laser light induced hyperthermia (HT) on HSP-mediated protection against ATXN1 toxicity. We first tested the effects of HT in a cell culture model and found that HT induced Hsp70 and increased its localization to nuclear inclusions in HeLa cells expressing GFP-ATXN1[82Q]. HT treatment decreased ATXN1 aggregation by making GFP-ATXN1[82Q] inclusions smaller and more numerous compared to non-treated cells. Further, we tested our HT approach in vivo using a transgenic (Tg) mouse model of SCA1. We found that our laser method increased cerebellar temperature from 38 to 40 °C without causing any neuronal damage or inflammatory response. Interestingly, mild cerebellar HT stimulated the production of Hsp70 to a significant level. Furthermore, multiple exposure of focused cerebellar laser light induced HT to heterozygous SCA1 transgenic (Tg) mice significantly suppressed the SCA1 phenotype as compared to sham-treated control animals. Moreover, in treated SCA1 Tg mice, the levels of PC calcium signaling/buffering protein calbindin-D28k markedly increased followed by a reduction in PC neurodegenerative morphology. Taken together, our data suggest that laser light induced HT is a novel non-invasive approach to treat SCA1 and maybe other polyglutamine disorders.
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Affiliation(s)
- Scoty M Hearst
- Department of Neurology, University of Mississippi Medical Center, 2500 N State St, Jackson, MS, 39216, USA
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109
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Duncan EJ, Cheetham ME, Chapple JP, van der Spuy J. The role of HSP70 and its co-chaperones in protein misfolding, aggregation and disease. Subcell Biochem 2015; 78:243-73. [PMID: 25487025 DOI: 10.1007/978-3-319-11731-7_12] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Molecular chaperones and their associated co-chaperones are essential in health and disease as they are key facilitators of protein folding, quality control and function. In particular, the HSP70 molecular chaperone networks have been associated with neurodegenerative diseases caused by aberrant protein folding. The pathogenesis of these disorders usually includes the formation of deposits of misfolded, aggregated protein. HSP70 and its co-chaperones have been recognised as potent modulators of inclusion formation and cell survival in cellular and animal models of neurodegenerative disease. In has become evident that the HSP70 chaperone machine functions not only in folding, but also in proteasome mediated degradation of neurodegenerative disease proteins. Thus, there has been a great deal of interest in the potential manipulation of molecular chaperones as a therapeutic approach for many neurodegenerations. Furthermore, mutations in several HSP70 co-chaperones and putative co-chaperones have been identified as causing inherited neurodegenerative and cardiac disorders, directly linking the HSP70 chaperone system to human disease.
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Affiliation(s)
- Emma J Duncan
- Molecular Endocrinology Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charter House Square, EC1M 6BQ, London, UK,
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110
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Faggiano S, Menon RP, Kelly GP, Todi SV, Scaglione KM, Konarev PV, Svergun DI, Paulson HL, Pastore A. Allosteric regulation of deubiquitylase activity through ubiquitination. Front Mol Biosci 2015; 2:2. [PMID: 25988170 PMCID: PMC4428445 DOI: 10.3389/fmolb.2015.00002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 01/07/2015] [Indexed: 12/28/2022] Open
Abstract
Ataxin-3, the protein responsible for spinocerebellar ataxia type-3, is a cysteine protease that specifically cleaves poly-ubiquitin chains and participates in the ubiquitin proteasome pathway. The enzymatic activity resides in the N-terminal Josephin domain. An unusual feature of ataxin-3 is its low enzymatic activity especially for mono-ubiquitinated substrates and short ubiquitin chains. However, specific ubiquitination at lysine 117 in the Josephin domain activates ataxin-3 through an unknown mechanism. Here, we investigate the effects of K117 ubiquitination on the structure and enzymatic activity of the protein. We show that covalently linked ubiquitin rests on the Josephin domain, forming a compact globular moiety and occupying a ubiquitin binding site previously thought to be essential for substrate recognition. In doing so, ubiquitination enhances enzymatic activity by locking the enzyme in an activated state. Our results indicate that ubiquitin functions both as a substrate and as an allosteric regulatory factor. We provide a novel example in which a conformational switch controls the activity of an enzyme that mediates deubiquitination.
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Affiliation(s)
- Serena Faggiano
- National Institute for Medical Research, Medical Research Council London, UK
| | - Rajesh P Menon
- National Institute for Medical Research, Medical Research Council London, UK
| | - Geoff P Kelly
- Medical Research Council Biomedical NMR Centre, National Institute for Medical Research, Medical Research Council London, UK
| | - Sokol V Todi
- Department of Pharmacology and Department of Neurology, Wayne State University School of Medicine Detroit, MI, USA
| | - K Matthew Scaglione
- Department of Biochemistry and The Neuroscience Research Center, Medical College of Wisconsin Milwaukee, WI, USA
| | - Petr V Konarev
- European Molecular Biology Laboratory Hamburg, Germany ; Laboratory of Reflectometry and Small-Angle Scattering, Institute of Crystallography Russian Academy of Sciences Moscow, Russia
| | | | - Henry L Paulson
- Department of Neurology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Annalisa Pastore
- Department of Clinical Neuroscience, King's College London London, UK
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111
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Juenemann K, Wiemhoefer A, Reits EA. Detection of ubiquitinated huntingtin species in intracellular aggregates. Front Mol Neurosci 2015; 8:1. [PMID: 25674046 PMCID: PMC4309157 DOI: 10.3389/fnmol.2015.00001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 01/05/2015] [Indexed: 01/08/2023] Open
Abstract
Protein conformation diseases, including polyglutamine (polyQ) diseases, result from the accumulation and aggregation of misfolded proteins. Huntington’s disease (HD) is one of nine diseases caused by an expanded polyQ repeat within the affected protein and is hallmarked by intracellular inclusion bodies composed of aggregated N-terminal huntingtin (Htt) fragments and other sequestered proteins. Fluorescence microscopy and filter trap assay are conventional methods to study protein aggregates, but cannot be used to analyze the presence and levels of post-translational modifications of aggregated Htt such as ubiquitination. Ubiquitination of proteins can be a signal for degradation and intracellular localization, but also affects protein activity and protein-protein interactions. The function of ubiquitination relies on its mono- and polymeric isoforms attached to protein substrates. Studying the ubiquitination pattern of aggregated Htt fragments offers an important possibility to understand Htt degradation and aggregation processes within the cell. For the identification of aggregated Htt and its ubiquitinated species, solubilization of the cellular aggregates is mandatory. Here we describe methods to identify post-translational modifications such as ubiquitination of aggregated mutant Htt. This approach is specifically described for use with mammalian cell culture and is suitable to study other disease-related proteins prone to aggregate.
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Affiliation(s)
- Katrin Juenemann
- Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Anne Wiemhoefer
- Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Eric A Reits
- Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
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112
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Abstract
SIGNIFICANCE Impairment of the ubiquitin-proteasome system (UPS) has been implicated in the pathogenesis of a wide variety of neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's diseases. The most significant risk factor for the development of these disorders is aging, which is associated with a progressive decline in UPS activity and the accumulation of oxidatively modified proteins. To date, no therapies have been developed that can specifically up-regulate this system. RECENT ADVANCES In the neurodegenerative brain, dysfunction of the UPS has been associated with the deposition of ubiquitinated protein aggregates and widespread disruption of the proteostasis network. Recent research has identified further evidence of impairment in substrate ubiquitination and proteasomal degradation, which could contribute to the loss of cellular proteostasis in neurodegenerative disease. Novel strategies for activation of the UPS by genetic manipulation and treatment with synthetic compounds have also recently been identified. CRITICAL ISSUES Here, we discuss the specific roles of the UPS in the healthy central nervous system and establish how dysfunctional components can contribute to neurotoxicity in the context of disease. FUTURE DIRECTIONS Knowledge of the UPS components that are specifically or preferentially involved in neurodegenerative disease will be critical in the development of targeted therapies which aim at limiting the accumulation of misfolded proteins without gross disturbance of this major proteolytic pathway.
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Affiliation(s)
- Chris McKinnon
- Department of Neurodegenerative Disease, University College London Institute of Neurology , London, United Kingdom
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113
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Paul I, Ghosh MK. A CHIPotle in physiology and disease. Int J Biochem Cell Biol 2014; 58:37-52. [PMID: 25448416 DOI: 10.1016/j.biocel.2014.10.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 09/21/2014] [Accepted: 10/25/2014] [Indexed: 01/06/2023]
Abstract
The carboxy-terminus of Hsc70 interacting protein (CHIP) is known to function as a chaperone associated E3 ligase for several proteins and regulates a variety of physiological processes. Being a connecting link between molecular chaperones and 26S proteasomes, it is widely regarded as the central player in the cellular protein quality control system. Recent analyses have provided new insights on the biochemical and functional dynamics of CHIP. In this review article, we give a comprehensive account of our current knowledge on the biology of CHIP, which apart from shedding light on fundamental biological questions promises to provide a potential target for therapeutic intervention.
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Affiliation(s)
- Indranil Paul
- Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research - Indian Institute of Chemical Biology (CSIR-IICB), 4, Raja S.C. Mullick Road, Kolkata 700032, India
| | - Mrinal K Ghosh
- Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research - Indian Institute of Chemical Biology (CSIR-IICB), 4, Raja S.C. Mullick Road, Kolkata 700032, India.
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Ronnebaum SM, Patterson C, Schisler JC. Emerging evidence of coding mutations in the ubiquitin-proteasome system associated with cerebellar ataxias. Hum Genome Var 2014; 1:14018. [PMID: 27081508 PMCID: PMC4785523 DOI: 10.1038/hgv.2014.18] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 08/20/2014] [Accepted: 08/28/2014] [Indexed: 12/14/2022] Open
Abstract
Cerebellar ataxia (CA) is a disorder associated with impairments in balance, coordination, and gait caused by degeneration of the cerebellum. The mutations associated with CA affect functionally diverse genes; furthermore, the underlying genetic basis of a given CA is unknown in many patients. Exome sequencing has emerged as a cost-effective technology to discover novel genetic mutations, including autosomal recessive CA (ARCA). Five recent studies that describe how exome sequencing performed on a diverse pool of ARCA patients revealed 14 unique mutations in STUB1, a gene that encodes carboxy terminus of Hsp70-interacting protein (CHIP). CHIP mediates protein quality control through chaperone and ubiquitin ligase activities and is implicated in alleviating proteotoxicity in several neurodegenerative diseases. However, these recent studies linking STUB1 mutations to various forms of ataxia are the first indications that CHIP is directly involved in the progression of a human disease. Similar exome-sequencing studies have revealed novel mutations in ubiquitin-related proteins associated with CA and other neurological disorders. This review provides an overview of CA, describes the benefits and limitations of exome sequencing, outlines newly discovered STUB1 mutations, and theorizes on how CHIP and other ubiquitin-related proteins function to prevent neurological deterioration.
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Affiliation(s)
- Sarah M Ronnebaum
- McAllister Heart Institute, The University of North Carolina at Chapel Hill , Chapel Hill, NC, USA
| | - Cam Patterson
- Presbyterian Hospital/Weill-Cornell Medical Center , New York, NY, USA
| | - Jonathan C Schisler
- McAllister Heart Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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115
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Zeng L, Tallaksen-Greene SJ, Wang B, Albin RL, Paulson HL. The de-ubiquitinating enzyme ataxin-3 does not modulate disease progression in a knock-in mouse model of Huntington disease. J Huntingtons Dis 2014; 2:201-15. [PMID: 24683430 DOI: 10.3233/jhd-130058] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Ataxin-3 is a deubiquitinating enzyme (DUB) that participates in ubiquitin-dependent protein quality control pathways and, based on studies in model systems, may be neuroprotective against toxic polyglutamine proteins such as the Huntington's disease (HD) protein, huntingtin (htt). HD is one of at least nine polyglutamine neurodegenerative diseases in which disease-causing proteins accumulate in ubiquitin-positive inclusions within neurons. In studies crossing mice null for ataxin-3 to an established HD knock-in mouse model (HdhQ200), we tested whether loss of ataxin-3 alters disease progression, perhaps by impairing the clearance of mutant htt or the ubiquitination of inclusions. While loss of ataxin-3 mildly exacerbated age-dependent motor deficits, it did not alter inclusion formation, ubiquitination of inclusions or levels of mutant or normal htt. Ataxin-3, itself a polyglutamine-containing protein with multiple ubiquitin binding domains, was not observed to localize to htt inclusions. Changes in neurotransmitter receptor binding known to occur in HD knock-in mice also were not altered by the loss of ataxin-3, although we unexpectedly observed increased GABAA receptor binding in the striatum of HdhQ200 mice, which has not previously been noted. Finally, we confirmed that CNS levels of hsp70 are decreased in HD mice as has been reported in other HD mouse models, regardless of the presence or absence of ataxin-3. We conclude that while ataxin-3 may participate in protein quality control pathways, it does not critically regulate the handling of mutant htt or contribute to major features of disease pathogenesis in HD.
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Affiliation(s)
- Li Zeng
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | | | - Bo Wang
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Roger L Albin
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA ; Geriatrics Research, Education, and Clinical Center, VAAAHS, Ann Arbor, MI, USA
| | - Henry L Paulson
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
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Heimdal K, Sanchez-Guixé M, Aukrust I, Bollerslev J, Bruland O, Jablonski GE, Erichsen AK, Gude E, Koht JA, Erdal S, Fiskerstrand T, Haukanes BI, Boman H, Bjørkhaug L, Tallaksen CME, Knappskog PM, Johansson S. STUB1 mutations in autosomal recessive ataxias - evidence for mutation-specific clinical heterogeneity. Orphanet J Rare Dis 2014; 9:146. [PMID: 25258038 PMCID: PMC4181732 DOI: 10.1186/s13023-014-0146-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 09/08/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A subset of hereditary cerebellar ataxias is inherited as autosomal recessive traits (ARCAs). Classification of recessive ataxias due to phenotypic differences in the cerebellum and cerebellar structures is constantly evolving due to new identified disease genes. Recently, reports have linked mutations in genes involved in ubiquitination (RNF216, OTUD4, STUB1) to ARCA with hypogonadism. METHODS AND RESULTS With a combination of homozygozity mapping and exome sequencing, we identified three mutations in STUB1 in two families with ARCA and cognitive impairment; a homozygous missense variant (c.194A > G, p.Asn65Ser) that segregated in three affected siblings, and a missense change (c.82G > A, p.Glu28Lys) which was inherited in trans with a nonsense mutation (c.430A > T, p.Lys144Ter) in another patient. STUB1 encodes CHIP (C-terminus of Heat shock protein 70 - Interacting Protein), a dual function protein with a role in ubiquitination as a co-chaperone with heat shock proteins, and as an E3 ligase. We show that the p.Asn65Ser substitution impairs CHIP's ability to ubiquitinate HSC70 in vitro, despite being able to self-ubiquitinate. These results are consistent with previous studies highlighting this as a critical residue for the interaction between CHIP and its co-chaperones. Furthermore, we show that the levels of CHIP are strongly reduced in vivo in patients' fibroblasts compared to controls. CONCLUSIONS These results suggest that STUB1 mutations might cause disease by impacting not only the E3 ligase function, but also its protein interaction properties and protein amount. Whether the clinical heterogeneity seen in STUB1 ARCA can be related to the location of the mutations remains to be understood, but interestingly, all siblings with the p.Asn65Ser substitution showed a marked appearance of accelerated aging not previously described in STUB1 related ARCA, none display hormonal aberrations/clinical hypogonadism while some affected family members had diabetes, alopecia, uveitis and ulcerative colitis, further refining the spectrum of STUB1 related disease.
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Pratt WB, Gestwicki JE, Osawa Y, Lieberman AP. Targeting Hsp90/Hsp70-based protein quality control for treatment of adult onset neurodegenerative diseases. Annu Rev Pharmacol Toxicol 2014; 55:353-71. [PMID: 25292434 PMCID: PMC4372135 DOI: 10.1146/annurev-pharmtox-010814-124332] [Citation(s) in RCA: 169] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Currently available therapies for adult onset neurodegenerative diseases provide symptomatic relief but do not modify disease progression. Here we explore a new neuroprotective approach based on drugs targeting chaperone-directed protein quality control. Critical target proteins that unfold and aggregate in these diseases, such as the polyglutamine androgen receptor in spinal and bulbar muscular atrophy, huntingtin in Huntington's disease, α-synuclein in Parkinson's disease, and tau in Alzheimer's disease, are client proteins of heat shock protein 90 (Hsp90), and their turnover is regulated by the protein quality control function of the Hsp90/Hsp70-based chaperone machinery. Hsp90 and Hsp70 have opposing effects on client protein stability in protein quality control; Hsp90 stabilizes the clients and inhibits their ubiquitination, whereas Hsp70 promotes ubiquitination dependent on CHIP (C terminus of Hsc70-interacting protein) and proteasomal degradation. We discuss how drugs that modulate proteostasis by inhibiting Hsp90 function or promoting Hsp70 function enhance the degradation of the critical aggregating proteins and ameliorate toxic symptoms in cell and animal disease models.
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Affiliation(s)
- William B. Pratt
- Departments of Pharmacology, The University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Jason E. Gestwicki
- Department of Pharmaceutical Chemistry and Institute for Neurodegenerative Disease, The University of California at San Franscisco, San Francisco, CA 94158
| | - Yoichi Osawa
- Departments of Pharmacology, The University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Andrew P. Lieberman
- Departments of Pathology, The University of Michigan Medical School, Ann Arbor, Michigan 48109
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From pathways to targets: understanding the mechanisms behind polyglutamine disease. BIOMED RESEARCH INTERNATIONAL 2014; 2014:701758. [PMID: 25309920 PMCID: PMC4189765 DOI: 10.1155/2014/701758] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 09/03/2014] [Indexed: 12/27/2022]
Abstract
The history of polyglutamine diseases dates back approximately 20 years to the discovery of a polyglutamine repeat in the androgen receptor of SBMA followed by the identification of similar expansion mutations in Huntington's disease, SCA1, DRPLA, and the other spinocerebellar ataxias. This common molecular feature of polyglutamine diseases suggests shared mechanisms in disease pathology and neurodegeneration of disease specific brain regions. In this review, we discuss the main pathogenic pathways including proteolytic processing, nuclear shuttling and aggregation, mitochondrial dysfunction, and clearance of misfolded polyglutamine proteins and point out possible targets for treatment.
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119
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Mahogunin ring finger 1 suppresses misfolded polyglutamine aggregation and cytotoxicity. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1472-84. [DOI: 10.1016/j.bbadis.2014.04.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 04/04/2014] [Accepted: 04/13/2014] [Indexed: 12/31/2022]
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Ubiquitin-binding site 2 of ataxin-3 prevents its proteasomal degradation by interacting with Rad23. Nat Commun 2014; 5:4638. [PMID: 25144244 PMCID: PMC4237202 DOI: 10.1038/ncomms5638] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 07/08/2014] [Indexed: 12/31/2022] Open
Abstract
Polyglutamine repeat expansion in ataxin-3 causes neurodegeneration in the most common dominant ataxia, Spinocerebellar Ataxia Type 3 (SCA3). Since reducing levels of disease proteins improves pathology in animals, we investigated how ataxin-3 is degraded. Here we show that, unlike most proteins, ataxin-3 turnover does not require its ubiquitination, but is regulated by Ubiquitin-Binding Site 2 (UbS2) on its N terminus. Mutating UbS2 decreases ataxin-3 protein levels in cultured mammalian cells and in Drosophila melanogaster by increasing its proteasomal turnover. Ataxin-3 interacts with the proteasome-associated proteins Rad23A/B through UbS2. Knockdown of Rad23 in cultured cells and in Drosophila results in lower levels of ataxin-3 protein. Importantly, reducing Rad23 suppresses ataxin-3-dependent degeneration in flies. We present a mechanism for ubiquitination-independent degradation that is impeded by protein interactions with proteasome-associated factors. We conclude that UbS2 is a potential target through which to enhance ataxin-3 degradation for SCA3 therapy.
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121
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Che XQ, Tang BS, Wang HF, Yan XX, Jiang H, Shen L, Xu Q, Wang GH, Zhang HN, Wang CY, Guo JF. The BAG2 and BAG5 proteins inhibit the ubiquitination of pathogenic ataxin3-80Q. Int J Neurosci 2014; 125:390-4. [DOI: 10.3109/00207454.2014.940585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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122
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Spontaneous self-assembly of pathogenic huntingtin exon 1 protein into amyloid structures. Essays Biochem 2014; 56:167-80. [DOI: 10.1042/bse0560167] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PolyQ (polyglutamine) diseases such as HD (Huntington's disease) or SCA1 (spinocerebellar ataxia type 1) are neurodegenerative disorders caused by abnormally elongated polyQ tracts in human proteins. PolyQ expansions promote misfolding and aggregation of disease-causing proteins, leading to the appearance of nuclear and cytoplasmic inclusion bodies in patient neurons. Several lines of experimental evidence indicate that this process is critical for disease pathogenesis. However, the molecular mechanisms underlying spontaneous polyQ-containing aggregate formation and the perturbation of neuronal processes are still largely unclear. The present chapter reviews the current literature regarding misfolding and aggregation of polyQ-containing disease proteins. We specifically focus on studies that have investigated the amyloidogenesis of polyQ-containing HTTex1 (huntingtin exon 1) fragments. These protein fragments are disease-relevant and play a critical role in HD pathogenesis. We outline potential mechanisms behind mutant HTTex1 aggregation and toxicity, as well as proteins and small molecules that can modify HTTex1 amyloidogenesis in vitro and in vivo. The potential implications of such studies for the development of novel therapeutic strategies are discussed.
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123
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Margulis J, Finkbeiner S. Proteostasis in striatal cells and selective neurodegeneration in Huntington's disease. Front Cell Neurosci 2014; 8:218. [PMID: 25147502 PMCID: PMC4124811 DOI: 10.3389/fncel.2014.00218] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 07/17/2014] [Indexed: 12/23/2022] Open
Abstract
Selective neuronal loss is a hallmark of neurodegenerative diseases, including Huntington’s disease (HD). Although mutant huntingtin, the protein responsible for HD, is expressed ubiquitously, a subpopulation of neurons in the striatum is the first to succumb. In this review, we examine evidence that protein quality control pathways, including the ubiquitin proteasome system, autophagy, and chaperones, are significantly altered in striatal neurons. These alterations may increase the susceptibility of striatal neurons to mutant huntingtin-mediated toxicity. This novel view of HD pathogenesis has profound therapeutic implications: protein homeostasis pathways in the striatum may be valuable targets for treating HD and other misfolded protein disorders.
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Affiliation(s)
- Julia Margulis
- Gladstone Institute of Neurological Disease, J. David Gladstone Institutes San Francisco, CA, USA ; Department of Neurology, University of California at San Francisco San Francisco, CA, USA ; Department of Physiology, University of California at San Francisco San Francisco, CA, USA
| | - Steven Finkbeiner
- Gladstone Institute of Neurological Disease, J. David Gladstone Institutes San Francisco, CA, USA ; Department of Neurology, University of California at San Francisco San Francisco, CA, USA ; Department of Physiology, University of California at San Francisco San Francisco, CA, USA ; Taube/Koret Center for Huntington's Disease Research San Francisco, CA, USA
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124
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Maheshwari M, Shekhar S, Singh BK, Jamal I, Vatsa N, Kumar V, Sharma A, Jana NR. Deficiency of Ube3a in Huntington's disease mice brain increases aggregate load and accelerates disease pathology. Hum Mol Genet 2014; 23:6235-45. [PMID: 25027318 DOI: 10.1093/hmg/ddu343] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Huntington's disease (HD) is an inherited neurodegenerative disorder caused by abnormal expansion of CAG repeats in the gene encoding huntingtin. Mutant huntingtin undergoes proteolytic processing and its N-terminal fragment containing polyglutamine repeat accumulates as inclusion not only in nucleus but also in cytoplasm and neuronal processes. Here, we demonstrate that removal of ubiquitin ligase Ube3a selectively from HD mice brain resulted in accelerated disease phenotype and shorter lifespan in comparison with HD mice. The deficiency of Ube3a in HD mice brain also caused significant increase in global aggregates load, and these aggregates were less ubiquitinated when compared with age-matched HD mice. These Ube3a-maternal deficient HD mice also showed drastic reduction of DARPP-32, a dopamine-regulated phoshphoprotein in their striatum. These results emphasize the crucial role of Ube3a in the progression of HD and its immense potential as therapeutic target.
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Affiliation(s)
- Megha Maheshwari
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Shashi Shekhar
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Brijesh Kumar Singh
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Imran Jamal
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Naman Vatsa
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Vipendra Kumar
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Ankit Sharma
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
| | - Nihar Ranjan Jana
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
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Evers MM, Toonen LJA, van Roon-Mom WMC. Ataxin-3 protein and RNA toxicity in spinocerebellar ataxia type 3: current insights and emerging therapeutic strategies. Mol Neurobiol 2014; 49:1513-31. [PMID: 24293103 PMCID: PMC4012159 DOI: 10.1007/s12035-013-8596-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 11/14/2013] [Indexed: 01/10/2023]
Abstract
Ataxin-3 is a ubiquitously expressed deubiqutinating enzyme with important functions in the proteasomal protein degradation pathway and regulation of transcription. The C-terminus of the ataxin-3 protein contains a polyglutamine (PolyQ) region that, when mutationally expanded to over 52 glutamines, causes the neurodegenerative disease spinocerebellar ataxia 3 (SCA3). In spite of extensive research, the molecular mechanisms underlying the cellular toxicity resulting from mutant ataxin-3 remain elusive and no preventive treatment is currently available. It has become clear over the last decade that the hallmark intracellular ataxin-3 aggregates are likely not the main toxic entity in SCA3. Instead, the soluble PolyQ containing fragments arising from proteolytic cleavage of ataxin-3 by caspases and calpains are now regarded to be of greater influence in pathogenesis. In addition, recent evidence suggests potential involvement of a RNA toxicity component in SCA3 and other PolyQ expansion disorders, increasing the pathogenic complexity. Herein, we review the functioning of ataxin-3 and the involvement of known protein and RNA toxicity mechanisms of mutant ataxin-3 that have been discovered, as well as future opportunities for therapeutic intervention.
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Affiliation(s)
- Melvin M. Evers
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands
| | - Lodewijk J. A. Toonen
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands
| | - Willeke M. C. van Roon-Mom
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333ZA Leiden, The Netherlands
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126
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Ubiquitin ligase ITCH recruitment suppresses the aggregation and cellular toxicity of cytoplasmic misfolded proteins. Sci Rep 2014; 4:5077. [PMID: 24865853 PMCID: PMC4035578 DOI: 10.1038/srep05077] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 05/06/2014] [Indexed: 12/13/2022] Open
Abstract
The protein quality control (QC) system protects cells against cellular toxicity induced by misfolded proteins and maintains overall cellular fitness. Inefficient clearance of or failure to degrade damaged proteins causes several diseases, especially age-linked neurodegenerative disorders. Attenuation of misfolded protein degradation under severe stress conditions leads to the rapid over-accumulation of toxic proteinaceous aggregates in the cytoplasmic compartment. However, the precise cytoplasmic quality control degradation mechanism is unknown. In the present study, we demonstrate that the Nedd4-like E3 ubiquitin ligase ITCH specifically interacts with mutant bona fide misfolded proteins and colocalizes with their perinuclear aggregates. In a cell culture model, we demonstrate ITCH recruitment by cytoplasmic inclusions containing polyglutamine-expanded huntingtin or ataxin-3 proteins. Transient overexpression of ITCH dramatically induced the degradation of thermally denatured misfolded luciferase protein. Partial depletion of ITCH increased the rate of aggregate formation and cell death generated by expanded polyglutamine proteins. Finally, we demonstrate that overexpression of ITCH alleviates the cytotoxic potential of expanded polyglutamine proteins and reduces aggregation. These observations indicate that ITCH is involved in the cytosolic quality control pathway and may help to explain how abnormal proteins are targeted by QC ubiquitin-protein ligases.
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Thomas EA. Involvement of HDAC1 and HDAC3 in the Pathology of Polyglutamine Disorders: Therapeutic Implications for Selective HDAC1/HDAC3 Inhibitors. Pharmaceuticals (Basel) 2014; 7:634-61. [PMID: 24865773 PMCID: PMC4078513 DOI: 10.3390/ph7060634] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 05/08/2014] [Accepted: 05/12/2014] [Indexed: 12/28/2022] Open
Abstract
Histone deacetylases (HDACs) enzymes, which affect the acetylation status of histones and other important cellular proteins, have been recognized as potentially useful therapeutic targets for a broad range of human disorders. Emerging studies have demonstrated that different types of HDAC inhibitors show beneficial effects in various experimental models of neurological disorders. HDAC enzymes comprise a large family of proteins, with18 HDAC enzymes currently identified in humans. Hence, an important question for HDAC inhibitor therapeutics is which HDAC enzyme(s) is/are important for the amelioration of disease phenotypes, as it has become clear that individual HDAC enzymes play different biological roles in the brain. This review will discuss evidence supporting the involvement of HDAC1 and HDAC3 in polyglutamine disorders, including Huntington's disease, and the use of HDAC1- and HDAC3-selective HDAC inhibitors as therapeutic intervention for these disorders. Further, while HDAC inhibitors are known alter chromatin structure resulting in changes in gene transcription, understanding the exact mechanisms responsible for the preclinical efficacy of these compounds remains a challenge. The potential chromatin-related and non-chromatin-related mechanisms of action of selective HDAC inhibitors will also be discussed.
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Affiliation(s)
- Elizabeth A Thomas
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, SP2030 10550 N. Torrey Pines Rd, La Jolla, CA 92037, USA.
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128
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The E3 ligase CHIP: insights into its structure and regulation. BIOMED RESEARCH INTERNATIONAL 2014; 2014:918183. [PMID: 24868554 PMCID: PMC4017836 DOI: 10.1155/2014/918183] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 04/07/2014] [Indexed: 12/21/2022]
Abstract
The carboxy-terminus of Hsc70 interacting protein (CHIP) is a cochaperone E3 ligase containing three tandem repeats of tetratricopeptide (TPR) motifs and a C-terminal U-box domain separated by a charged coiled-coil region. CHIP is known to function as a central quality control E3 ligase and regulates several proteins involved in a myriad of physiological and pathological processes. Recent studies have highlighted varied regulatory mechanisms operating on the activity of CHIP which is crucial for cellular homeostasis. In this review article, we give a concise account of our current knowledge on the biochemistry and regulation of CHIP.
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129
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Synofzik M, Schüle R, Schulze M, Gburek-Augustat J, Schweizer R, Schirmacher A, Krägeloh-Mann I, Gonzalez M, Young P, Züchner S, Schöls L, Bauer P. Phenotype and frequency of STUB1 mutations: next-generation screenings in Caucasian ataxia and spastic paraplegia cohorts. Orphanet J Rare Dis 2014; 9:57. [PMID: 24742043 PMCID: PMC4021831 DOI: 10.1186/1750-1172-9-57] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 04/11/2014] [Indexed: 02/02/2023] Open
Abstract
Background Mutations in the gene STUB1, encoding the protein CHIP (C-terminus of HSC70-interacting protein), have recently been suggested as a cause of recessive ataxia based on the findings in few Chinese families. Here we aimed to investigate the phenotypic and genotypic spectrum of STUB1 mutations, and to assess their frequency in different Caucasian disease cohorts. Methods 300 subjects with degenerative ataxia (n = 167) or spastic paraplegia (n = 133) were screened for STUB1 variants by whole-exome-sequencing (n = 204) or shotgun-fragment-library-sequencing (n = 96). To control for the specificity of STUB1 variants, we screened an additional 1707 exomes from 891 index families with other neurological diseases. Results We identified 3 ataxia patients (3/167 = 1.8%) with 4 novel missense mutations in STUB1, including 3 mutations in its tetratricopeptide-repeat domain. All patients showed evidence of pyramidal tract damage. Cognitive impairment was present only in one and hypogonadism in none of them. Ataxia did not start before age 48 years in one subject. No recessive STUB1 variants were identified in families with other neurological diseases, demonstrating that STUB1 variants are not simply rare polymorphisms ubiquitous in neurodegenerative disease. Conclusions STUB1-disease occurs also in Caucasian ataxia populations (1.8%). Our results expand the genotypic spectrum of STUB1-disease, showing that pathogenic mutations affect also the tetratricopeptide-repeat domain, thus providing clinical evidence for the functional importance of this domain. Moreover, they further delineate the phenotypic core features of STUB1-ataxia. Pyramidal tract damage is a common accompanying feature and can include lower limb spasticity, thus adding STUB1-ataxia to the differential diagnosis of “spastic ataxias”. However, STUB1 is rare in subjects with predominant spastic paraplegia (0/133). In contrast to previous reports, STUB1-ataxia can start even above age 40 years, and neither hypogonadism nor prominent cognitive impairment are obligatory features.
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Affiliation(s)
- Matthis Synofzik
- Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research, University of Tübingen, Hoppe-Seyler-Str, 3, 72076 Tübingen, Germany.
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Sensitive detection of proteasomal activation using the Deg-On mammalian synthetic gene circuit. Nat Commun 2014; 5:3612. [DOI: 10.1038/ncomms4612] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 03/10/2014] [Indexed: 01/08/2023] Open
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131
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Yamanaka T, Wong HK, Tosaki A, Bauer PO, Wada K, Kurosawa M, Shimogori T, Hattori N, Nukina N. Large-scale RNA interference screening in mammalian cells identifies novel regulators of mutant huntingtin aggregation. PLoS One 2014; 9:e93891. [PMID: 24705917 PMCID: PMC3976342 DOI: 10.1371/journal.pone.0093891] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 03/10/2014] [Indexed: 01/04/2023] Open
Abstract
In polyglutamine (polyQ) diseases including Huntington's disease (HD), mutant proteins containing expanded polyQ stretch form aggregates in neurons. Genetic or RNAi screenings in yeast, C. elegans or Drosophila have identified multiple genes modifying polyQ aggregation, a few of which are confirmed effective in mammals. However, the overall molecular mechanism underlying polyQ protein aggregation in mammalian cells still remains obscure. We here perform RNAi screening in mouse neuro2a cells to identify mammalian modifiers for aggregation of mutant huntingtin, a causative protein of HD. By systematic cell transfection and automated cell image analysis, we screen ∼12000 shRNA clones and identify 111 shRNAs that either suppress or enhance mutant huntingtin aggregation, without altering its gene expression. Classification of the shRNA-targets suggests that genes with various cellular functions such as gene transcription and protein phosphorylation are involved in modifying the aggregation. Subsequent analysis suggests that, in addition to the aggregation-modifiers sensitive to proteasome inhibition, some of them, such as a transcription factor Tcf20, and kinases Csnk1d and Pik3c2a, are insensitive to it. As for Tcf20, which contains polyQ stretches at N-terminus, its binding to mutant huntingtin aggregates is observed in neuro2a cells and in HD model mouse neurons. Notably, except Pik3c2a, the rest of the modifiers identified here are novel. Thus, our first large-scale RNAi screening in mammalian system identifies previously undescribed genetic players that regulate mutant huntingtin aggregation by several, possibly mammalian-specific mechanisms.
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Affiliation(s)
- Tomoyuki Yamanaka
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
- Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan
- CREST (Core Research for Evolutionary Science and Technology), JST, Tokyo, Japan
| | - Hon Kit Wong
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
- Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Harvard Institutes of Medicine, Boston, Massachusetts, United States of America
| | - Asako Tosaki
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
| | - Peter O. Bauer
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
| | - Koji Wada
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
| | - Masaru Kurosawa
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
- Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan
- CREST (Core Research for Evolutionary Science and Technology), JST, Tokyo, Japan
| | - Tomomi Shimogori
- Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan
| | - Nobutaka Hattori
- Department of Neurology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Nobuyuki Nukina
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo, Japan
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
- Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, Saitama, Japan
- CREST (Core Research for Evolutionary Science and Technology), JST, Tokyo, Japan
- * E-mail:
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132
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Differential ubiquitination and degradation of huntingtin fragments modulated by ubiquitin-protein ligase E3A. Proc Natl Acad Sci U S A 2014; 111:5706-11. [PMID: 24706802 DOI: 10.1073/pnas.1402215111] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Ubiquitination of misfolded proteins, a common feature of many neurodegenerative diseases, is mediated by different lysine (K) residues in ubiquitin and alters the levels of toxic proteins. In Huntington disease, polyglutamine expansion causes N-terminal huntingtin (Htt) to misfold, inducing neurodegeneration. Here we report that shorter N-terminal Htt fragments are more stable than longer fragments and find differential ubiquitination via K63 of ubiquitin. Aging decreases proteasome-mediated Htt degradation, at the same time increasing K63-mediated ubiquitination and subsequent Htt aggregation in HD knock-in mice. The association of Htt with the K48-specific E3 ligase, Ube3a, is decreased in aged mouse brain. Overexpression of Ube3a in HD mouse brain reduces K63-mediated ubiquitination and Htt aggregation, enhancing its degradation via the K48 ubiquitin-proteasome system. Our findings suggest that aging-dependent Ube3a levels result in differential ubiquitination and degradation of Htt fragments, thereby contributing to the age-related neurotoxicity of mutant Htt.
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133
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Wei Q, Sha Y, Bhattacharya A, Abdel Fattah E, Bonilla D, Jyothula SSSK, Pandit L, Khurana Hershey GK, Eissa NT. Regulation of IL-4 receptor signaling by STUB1 in lung inflammation. Am J Respir Crit Care Med 2014; 189:16-29. [PMID: 24251647 DOI: 10.1164/rccm.201305-0874oc] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
RATIONALE IL-4Rα, the common receptor component for IL-4 and IL-13, plays a critical role in IL-4- and IL-13-mediated signaling pathways that regulate airway inflammation and remodeling. However, the regulatory mechanisms underlying IL-4Rα turnover and its signal termination remain elusive. OBJECTIVES To evaluate the role of STUB1 (STIP1 homology and U-Box containing protein 1) in regulating IL-4R signaling in airway inflammation. METHODS The roles of STUB1 in IL-4Rα degradation and its signaling were investigated by immunoblot, immunoprecipitation, and flow cytometry. The involvement of STUB1 in airway inflammation was determined in vivo by measuring lung inflammatory cells infiltration, mucus production, serum lgE levels, and alveolar macrophage M2 activation in STUB1(-/-) mice. STUB1 expression was evaluated in airway epithelium of patients with asthma and lung tissues of subjects with chronic obstructive pulmonary disease. MEASUREMENTS AND MAIN RESULTS STUB1 interacted with IL-4Rα and targeted it for ubiquitination-mediated proteasomal degradation, terminating IL-4 or IL-13 signaling. STUB1 knockout cells showed increased levels of IL-4Rα and sustained STAT6 activation, whereas STUB1 overexpression reduced IL-4Rα levels. Mice deficient in STUB1 had spontaneous airway inflammation, alternative M2 activation of alveolar macrophage, and increased serum IgE. STUB1 levels were increased in airways of subjects with asthma or chronic obstructive pulmonary disease, suggesting that up-regulation of STUB1 might be an important feedback mechanism to dampen IL-4R signaling in airway inflammation. CONCLUSIONS Our study identified a previously uncharacterized role for STUB1 in regulating IL-4R signaling, which might provide a new strategy for attenuating airway inflammation.
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Affiliation(s)
- Qin Wei
- 1 Department of Medicine, Baylor College of Medicine, Houston, Texas; and
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134
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Yu S, Liang Y, Palacino J, Difiglia M, Lu B. Drugging unconventional targets: insights from Huntington's disease. Trends Pharmacol Sci 2014; 35:53-62. [PMID: 24388390 DOI: 10.1016/j.tips.2013.12.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 12/03/2013] [Accepted: 12/05/2013] [Indexed: 12/12/2022]
Abstract
Classical targeted drug discovery is based on targeting druggable targets, typically kinases and receptors of which the function can be agonized or antagonized. This strategy meets difficulties in cases such as Huntington's disease (HD) and similar neurodegenerative disorders, where the pathological function of the protein causing the disease is not clear. HD is caused by mutant HTT protein (mHTT) containing an expanded polyglutamine (polyQ) stretch, but the function of mHTT and how mHTT causes HD are unknown, thus preventing efforts to screen for mHTT 'inhibitors'. However, HD is appealing for drug discovery because the genetic mutation is clear, as compared with other major neurodegenerative disorders. Although mHTT is not a conventional 'druggable' target, one approach that appears promising is lowering its level, which might be applicable to other neurodegenerative disorders and proteinopathies linked to aberrant accumulation of proteins. Here we review mHTT lowering strategies that might provide promising avenues for drugging such diseases.
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Affiliation(s)
- Shenliang Yu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - Yijian Liang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
| | - James Palacino
- Developmental Molecular Pathways, Novartis Institutes for Biomedical Research, Cambridge, MA, USA.
| | - Marian Difiglia
- Mass General Institute for Neurodegenerative Disease, Charlestown, MA, USA.
| | - Boxun Lu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China; Mass General Institute for Neurodegenerative Disease, Charlestown, MA, USA.
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135
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Maheshwari M, Bhutani S, Das A, Mukherjee R, Sharma A, Kino Y, Nukina N, Jana NR. Dexamethasone induces heat shock response and slows down disease progression in mouse and fly models of Huntington's disease. Hum Mol Genet 2013; 23:2737-51. [PMID: 24381308 DOI: 10.1093/hmg/ddt667] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Huntington's disease (HD) is an inherited neurodegenerative disorder caused by abnormal expansion of glutamine repeats in the protein huntingtin. In HD brain, mutant huntingtin undergoes proteolytic processing, and its N-terminal fragment containing poly-glutamine repeats accumulate as insoluble aggregates leading to the defect in cellular protein quality control system and heat shock response (HSR). Here we demonstrate that the defective HSR in the brain is due to the down-regulation of heat shock factor 1 (HSF1) in both mice and fly models of HD. Interestingly, treatment of dexamethasone (a synthetic glucocorticoid) to HD mice or flies significantly increased the expression and transactivation of HSF1 and induction of HSR and these effects are mediated through the down-regulation of HSP90. Dexamethasone treatment also significantly decreased the aggregate load and transient recovery of HD-related behavioural phenotypes in both disease models. These results suggest that dexamethasone could be a potential therapeutic molecule for the treatment of HD and related poly-glutamine disorders.
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Affiliation(s)
- Megha Maheshwari
- Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122 050, India
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136
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Shi Y, Wang J, Li JD, Ren H, Guan W, He M, Yan W, Zhou Y, Hu Z, Zhang J, Xiao J, Su Z, Dai M, Wang J, Jiang H, Guo J, Zhou Y, Zhang F, Li N, Du J, Xu Q, Hu Y, Pan Q, Shen L, Wang G, Xia K, Zhang Z, Tang B. Identification of CHIP as a novel causative gene for autosomal recessive cerebellar ataxia. PLoS One 2013; 8:e81884. [PMID: 24312598 PMCID: PMC3846781 DOI: 10.1371/journal.pone.0081884] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 10/02/2013] [Indexed: 12/14/2022] Open
Abstract
Autosomal recessive cerebellar ataxias are a group of neurodegenerative disorders that are characterized by complex clinical and genetic heterogeneity. Although more than 20 disease-causing genes have been identified, many patients are still currently without a molecular diagnosis. In a two-generation autosomal recessive cerebellar ataxia family, we mapped a linkage to a minimal candidate region on chromosome 16p13.3 flanked by single-nucleotide polymorphism markers rs11248850 and rs1218762. By combining the defined linkage region with the whole-exome sequencing results, we identified a homozygous mutation (c.493CT) in CHIP (NM_005861) in this family. Using Sanger sequencing, we also identified two compound heterozygous mutations (c.389AT/c.441GT; c.621C>G/c.707GC) in CHIP gene in two additional kindreds. These mutations co-segregated exactly with the disease in these families and were not observed in 500 control subjects with matched ancestry. CHIP colocalized with NR2A, a subunit of the N-methyl-D-aspartate receptor, in the cerebellum, pons, medulla oblongata, hippocampus and cerebral cortex. Wild-type, but not disease-associated mutant CHIPs promoted the degradation of NR2A, which may underlie the pathogenesis of ataxia. In conclusion, using a combination of whole-exome sequencing and linkage analysis, we identified CHIP, encoding a U-box containing ubiquitin E3 ligase, as a novel causative gene for autosomal recessive cerebellar ataxia.
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Affiliation(s)
- Yuting Shi
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Junling Wang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
- The State Key Laboratory of Medical Genetics, Changsha, China
- The Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China
| | - Jia-Da Li
- The State Key Laboratory of Medical Genetics, Changsha, China
| | - Haigang Ren
- Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Wenjuan Guan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Miao He
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Weiqian Yan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Ying Zhou
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Zhengmao Hu
- The State Key Laboratory of Medical Genetics, Changsha, China
| | - Jianguo Zhang
- BGI-Shenzhen, Shenzhen, China
- T-Life Research Center, Fudan University, Shanghai, China
| | | | | | | | - Jun Wang
- BGI-Shenzhen, Shenzhen, China
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
- King Abdulaziz University, Jeddah, Saudi Arabia
- The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
- Centre for iSequencing, Aarhus University, Aarhus C, Denmark
| | - Hong Jiang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
- The State Key Laboratory of Medical Genetics, Changsha, China
- The Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China
| | - Jifeng Guo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
- The State Key Laboratory of Medical Genetics, Changsha, China
- The Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China
| | - Yafang Zhou
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Fufeng Zhang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Nan Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Juan Du
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Qian Xu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Yacen Hu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Qian Pan
- The State Key Laboratory of Medical Genetics, Changsha, China
| | - Lu Shen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
- The State Key Laboratory of Medical Genetics, Changsha, China
- The Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China
| | - Guanghui Wang
- Department of Pharmacology, College of Pharmaceutical Sciences, Soochow University, Suzhou, China
| | - Kun Xia
- The State Key Laboratory of Medical Genetics, Changsha, China
| | - Zhuohua Zhang
- The State Key Laboratory of Medical Genetics, Changsha, China
| | - Beisha Tang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
- The State Key Laboratory of Medical Genetics, Changsha, China
- The Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China
- * E-mail:
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137
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Chu BW, Kovary KM, Guillaume J, Chen LC, Teruel MN, Wandless TJ. The E3 ubiquitin ligase UBE3C enhances proteasome processivity by ubiquitinating partially proteolyzed substrates. J Biol Chem 2013; 288:34575-87. [PMID: 24158444 DOI: 10.1074/jbc.m113.499350] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
To maintain protein homeostasis, cells must balance protein synthesis with protein degradation. Accumulation of misfolded or partially degraded proteins can lead to the formation of pathological protein aggregates. Here we report the use of destabilizing domains, proteins whose folding state can be reversibly tuned using a high affinity ligand, as model substrates to interrogate cellular protein quality control mechanisms in mammalian cells using a forward genetic screen. Upon knockdown of UBE3C, an E3 ubiquitin ligase, a reporter protein consisting of a destabilizing domain fused to GFP is degraded more slowly and incompletely by the proteasome. Partial proteolysis is also observed when UBE3C is present but cannot ubiquitinate substrates because its active site has been mutated, it is unable to bind to the proteasome, or the substrate lacks lysine residues. UBE3C knockdown also results in less substrate polyubiquitination. Finally, knockdown renders cells more susceptible to the Hsp90 inhibitor 17-AAG, suggesting that UBE3C protects against the harmful accumulation of protein fragments arising from incompletely degraded proteasome substrates.
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Affiliation(s)
- Bernard W Chu
- From the Department of Chemical and Systems Biology, Stanford University, Stanford, California 94305
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138
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Todd TW, Lim J. Aggregation formation in the polyglutamine diseases: protection at a cost? Mol Cells 2013; 36:185-94. [PMID: 23794019 PMCID: PMC3800151 DOI: 10.1007/s10059-013-0167-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 06/02/2013] [Indexed: 12/30/2022] Open
Abstract
Mutant protein aggregation is a hallmark of many neurodegenerative diseases, including the polyglutamine disorders. Although the correlation between aggregation formation and disease pathology originally suggested that the visible inclusions seen in patient tissue might directly contribute to pathology, additional studies failed to confirm this hypothesis. Current opinion in the field of polyglutamine disease research now favors a model in which large inclusions are cytoprotective and smaller oligomers or misfolded monomers underlie pathogenesis. Nonetheless, therapies aimed at reducing or preventing aggregation show promise. This review outlines the debate about the role of aggregation in the polyglutamine diseases as it has unfolded in the literature and concludes with a brief discussion on the manipulation of aggregation formation and clearance mechanisms as a means of therapeutic intervention.
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Affiliation(s)
- Tiffany W. Todd
- Department of Genetics, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
| | - Janghoo Lim
- Department of Genetics, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT 06510, USA
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139
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Comyn SA, Chan GT, Mayor T. False start: cotranslational protein ubiquitination and cytosolic protein quality control. J Proteomics 2013; 100:92-101. [PMID: 23954725 DOI: 10.1016/j.jprot.2013.08.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/02/2013] [Accepted: 08/04/2013] [Indexed: 12/18/2022]
Abstract
UNLABELLED Maintaining proteostasis is crucial to cells given the toxic potential of misfolded proteins and aggregates. To this end, cells rely on a number of quality control pathways that survey proteins both during, as well as after synthesis to prevent protein aggregation, promote protein folding, and to target terminally misfolded proteins for degradation. In eukaryotes, the ubiquitin proteasome system plays a critical role in protein quality control by selectively targeting proteins for degradation. Recent studies have added to our understanding of cytosolic protein quality control, particularly in the area of cotranslational protein ubiquitination, and suggest that overlap exists across co- and post-translational protein quality control networks. Here, we review recent advances made in the area of cytoplasmic protein quality control with an emphasis on the pathways involved in cotranslational degradation of eukaryotic cytosolic proteins. BIOLOGICAL SIGNIFICANCE Protein homeostasis, or proteostasis, encompasses the systems required by the cell for the generation and maintenance of the correct levels, conformational state, distribution, and degradation of its proteome. One of the challenges faced by the cell in maintaining proteostasis is the presence of misfolded proteins. Cells therefore have a number of protein quality control pathways to aid in folding or mediate the degradation of misfolded proteins. The ubiquitin proteasome system in particular plays a critical role in protein quality control by selectively targeting proteins for degradation. Nascent polypeptides can be ubiquitinated cotranslationally, however to what extent and how this is used by the cell as a quality control mechanism has, until recently, remained relatively unclear. The picture now emerging is one of two quality control networks: one that recognizes nascent polypeptides on stalled ribosomes and another that targets actively translating polypeptides that misfold, failing to attain their native conformation. These studies underscore the important balance between cotranslational protein folding and degradation in the maintenance of protein homeostasis. In this review we summarize recent advances made in the area of cytoplasmic protein quality control with an emphasis on pathways involved in cotranslational degradation of eukaryotic cytosolic proteins. This article is part of a Special Issue entitled: Can Proteomics Fill the Gap Between Genomics and Phenotypes?
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Affiliation(s)
- Sophie A Comyn
- Department of Biochemistry and Molecular Biology, Center for High-Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Gerard T Chan
- Department of Biochemistry and Molecular Biology, Center for High-Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Thibault Mayor
- Department of Biochemistry and Molecular Biology, Center for High-Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
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140
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van der Putten H, Lotz GP. Opportunities and challenges for molecular chaperone modulation to treat protein-conformational brain diseases. Neurotherapeutics 2013; 10:416-28. [PMID: 23536253 PMCID: PMC3701765 DOI: 10.1007/s13311-013-0186-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A common pathological hallmark of protein-conformational brain diseases is the formation of disease-specific protein aggregates. In Alzheimer's disease, these are comprised of amyloid-β and Tau as opposed to α-synuclein in Parkinson's disease and N-terminal fragments of mutant huntingtin in Huntington's disease. Most aggregates also sequester molecular chaperones, a protein family that assists in the folding, refolding, stabilization, and processing of client proteins, including misfolded proteins in brain diseases. Molecular chaperone modulation has achieved remarkable therapeutic effects in some cellular and preclinical animal models of protein-conformational diseases. This has raised hope for chaperone-based strategies to combat these diseases. Here, we review briefly the functional diversity and medical significance of molecular chaperones, their therapeutic potential, and common and specific challenges towards clinical application.
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Affiliation(s)
- Herman van der Putten
- Novartis Institutes for BioMedical Research, Novartis Pharma AG, CH-4002 Basel, Switzerland
| | - Gregor P. Lotz
- Novartis Institutes for BioMedical Research, Novartis Pharma AG, CH-4002 Basel, Switzerland
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141
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Rusmini P, Crippa V, Giorgetti E, Boncoraglio A, Cristofani R, Carra S, Poletti A. Clearance of the mutant androgen receptor in motoneuronal models of spinal and bulbar muscular atrophy. Neurobiol Aging 2013; 34:2585-603. [PMID: 23810450 PMCID: PMC3748343 DOI: 10.1016/j.neurobiolaging.2013.05.026] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 04/23/2013] [Accepted: 05/27/2013] [Indexed: 12/13/2022]
Abstract
Spinal and bulbar muscular atrophy (SBMA) is an X-linked motoneuron disease caused by an abnormal expansion of a tandem CAG repeat in exon 1 of the androgen receptor (AR) gene that results in an abnormally long polyglutamine tract (polyQ) in the AR protein. As a result, the mutant AR (ARpolyQ) misfolds, forming cytoplasmic and nuclear aggregates in the affected neurons. Neurotoxicity only appears to be associated with the formation of nuclear aggregates. Thus, improved ARpolyQ cytoplasmic clearance, which indirectly decreases ARpolyQ nuclear accumulation, has beneficial effects on affected motoneurons. In addition, increased ARpolyQ clearance contributes to maintenance of motoneuron proteostasis and viability, preventing the blockage of the proteasome and autophagy pathways that might play a role in the neuropathy in SBMA. The expression of heat shock protein B8 (HspB8), a member of the small heat shock protein family, is highly induced in surviving motoneurons of patients affected by motoneuron diseases, where it seems to participate in the stress response aimed at cell protection. We report here that HspB8 facilitates the autophagic removal of misfolded aggregating species of ARpolyQ. In addition, though HspB8 does not influence p62 and LC3 (two key autophagic molecules) expression, it does prevent p62 bodies formation, and restores the normal autophagic flux in these cells. Interestingly, trehalose, a well-known autophagy stimulator, induces HspB8 expression, suggesting that HspB8 might act as one of the molecular mediators of the proautophagic activity of trehalose. Collectively, these data support the hypothesis that treatments aimed at restoring a normal autophagic flux that result in the more efficient clearance of mutant ARpolyQ might produce beneficial effects in SBMA patients.
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Affiliation(s)
- Paola Rusmini
- Sezione di Biomedicina e Endocrinologia, Dipartimento di Scienze Farmacologiche e Biomolecolari, Centro di Eccellenza sulle Malattie Neurodegenerative, Universita' degli Studi di Milano, Milan, Italy
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142
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Almeida B, Fernandes S, Abreu IA, Macedo-Ribeiro S. Trinucleotide repeats: a structural perspective. Front Neurol 2013; 4:76. [PMID: 23801983 PMCID: PMC3687200 DOI: 10.3389/fneur.2013.00076] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 06/04/2013] [Indexed: 11/29/2022] Open
Abstract
Trinucleotide repeat (TNR) expansions are present in a wide range of genes involved in several neurological disorders, being directly involved in the molecular mechanisms underlying pathogenesis through modulation of gene expression and/or the function of the RNA or protein it encodes. Structural and functional information on the role of TNR sequences in RNA and protein is crucial to understand the effect of TNR expansions in neurodegeneration. Therefore, this review intends to provide to the reader a structural and functional view of TNR and encoded homopeptide expansions, with a particular emphasis on polyQ expansions and its role at inducing the self-assembly, aggregation and functional alterations of the carrier protein, which culminates in neuronal toxicity and cell death. Detail will be given to the Machado-Joseph Disease-causative and polyQ-containing protein, ataxin-3, providing clues for the impact of polyQ expansion and its flanking regions in the modulation of ataxin-3 molecular interactions, function, and aggregation.
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Affiliation(s)
- Bruno Almeida
- Instituto de Biologia Molecular e Celular, Universidade do Porto , Porto , Portugal
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143
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CHIP has a protective role against oxidative stress-induced cell death through specific regulation of endonuclease G. Cell Death Dis 2013; 4:e666. [PMID: 23764847 PMCID: PMC3698548 DOI: 10.1038/cddis.2013.181] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Oxidative stress is implicated in carcinogenesis, aging, and neurodegenerative diseases. The E3 ligase C terminus of Hsc-70 interacting protein (CHIP) has a protective role against various stresses by targeting damaged proteins for proteasomal degradation, and thus maintains protein quality control. However, the detailed mechanism by which CHIP protects cells from oxidative stress has not been demonstrated. Here, we show that depletion of CHIP led to elevated Endonuclease G (EndoG) levels and enhanced cell death upon oxidative stress. In contrast, CHIP overexpression reduced EndoG levels, and resulted in reduced or no oxidative stress-induced cell death in cancer cells and primary rat cortical neurons. Under normal conditions Hsp70 mediated the interaction between EndoG and CHIP, downregulating EndoG levels in a Hsp70/proteasome-dependent manner. However, under oxidative stress Hsp70 no longer interacted with EndoG, and the stabilized EndoG translocated to the nucleus and degraded chromosomal DNA. Our data suggest that regulation of the level of EndoG by CHIP in normal conditions may determine the sensitivity to cell death upon oxidative stress. Indeed, injection of H2O2 into the rat brain markedly increased cell death in aged mice compared with young mice, which correlated with elevated levels of EndoG and concurrent downregulation of CHIP in aged mice. Taken together, our findings demonstrate a novel protective mechanism of CHIP against oxidative stress through regulation of EndoG, and provide an opportunity to modulate oxidative stress-induced cell death in cancer and aging.
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144
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Durcan TM, Fon EA. Ataxin-3 and its e3 partners: implications for machado-joseph disease. Front Neurol 2013; 4:46. [PMID: 23653622 PMCID: PMC3644722 DOI: 10.3389/fneur.2013.00046] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 04/22/2013] [Indexed: 11/13/2022] Open
Abstract
Machado-Joseph disease (MJD) is the most common dominant inherited ataxia worldwide, caused by an unstable CAG trinucleotide expansion mutation within the SCA3 gene resulting in an expanded polyglutamine tract within the ataxin-3 protein. Ataxin-3 functions as a deubiquitinating enzyme (DUB), within the Ub system and whilst many DUBs are known to partner with and deubiquitinate specific E3-Ub ligases, ataxin-3 had no identified E3 partner until recent studies implicated parkin and CHIP, two neuroprotective E3 ligases. MJD often presents with symptoms of Parkinson disease (PD), which led to identification of parkin as a novel E3-Ub ligase whose activity was regulated by ataxin-3-mediated deubiquitination. Findings from these studies also revealed an unexpected convergence upon the E2-Ub-conjugating enzyme in the regulation of an E3/DUBenzyme pair. Moreover, mutant but not wild-type ataxin-3 promotes the clearance of parkin via the autophagy pathway, raising the intriguing possibility that increased turnover of parkin may contribute to the pathogenesis of MJD and help explain some of the Parkinsonian features in MJD. In addition to parkin, the U-box E3 ligase CHIP, a neuroprotective E3 implicated in protein quality control, was identified as a second E3 partner of ataxin-3, with ataxin-3 regulating the ability of CHIP to ubiquitinate itself. Indeed, ataxin-3 not only deubiquitinated CHIP, but also trimmed Ub conjugates on CHIP substrates, thereby regulating the length of Ub chains. Interestingly, when expanded ataxin-3 was present, CHIP levels were also reduced in the brains of MJD transgenic mice, raising the possibility that loss of one or both E3 partners may be a contributing factor in the pathogenesis of SCA3. In this review we discuss the implications from these studies and describe the importance of these findings in helping us understand the molecular processes involved in SCA3 and other neurodegenerative disorders.
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Affiliation(s)
- Thomas M Durcan
- Department of Neurology and Neurosurgery, Centre for Neuronal Survival and McGill Parkinson Program, Montreal Neurological Institute, McGill University Montreal, QC, Canada
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145
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Gillis J, Schipper-Krom S, Juenemann K, Gruber A, Coolen S, van den Nieuwendijk R, van Veen H, Overkleeft H, Goedhart J, Kampinga HH, Reits EA. The DNAJB6 and DNAJB8 protein chaperones prevent intracellular aggregation of polyglutamine peptides. J Biol Chem 2013; 288:17225-37. [PMID: 23612975 DOI: 10.1074/jbc.m112.421685] [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] [Indexed: 12/31/2022] Open
Abstract
Fragments of proteins containing an expanded polyglutamine (polyQ) tract are thought to initiate aggregation and toxicity in at least nine neurodegenerative diseases, including Huntington's disease. Because proteasomes appear unable to digest the polyQ tract, which can initiate intracellular protein aggregation, preventing polyQ peptide aggregation by chaperones should greatly improve polyQ clearance and prevent aggregate formation. Here we expressed polyQ peptides in cells and show that their intracellular aggregation is prevented by DNAJB6 and DNAJB8, members of the DNAJ (Hsp40) chaperone family. In contrast, HSPA/Hsp70 and DNAJB1, also members of the DNAJ chaperone family, did not prevent peptide-initiated aggregation. Intriguingly, DNAJB6 and DNAJB8 also affected the soluble levels of polyQ peptides, indicating that DNAJB6 and DNAJB8 inhibit polyQ peptide aggregation directly. Together with recent data showing that purified DNAJB6 can suppress fibrillation of polyQ peptides far more efficiently than polyQ expanded protein fragments in vitro, we conclude that the mechanism of DNAJB6 and DNAJB8 is suppression of polyQ protein aggregation by directly binding the polyQ tract.
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Affiliation(s)
- Judith Gillis
- Department of Cell Biology and Histology, Academic Medical Center, Amsterdam 1105AZ, The Netherlands
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146
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Lu B, Al-Ramahi I, Valencia A, Wang Q, Berenshteyn F, Yang H, Gallego-Flores T, Ichcho S, Lacoste A, Hild M, Difiglia M, Botas J, Palacino J. Identification of NUB1 as a suppressor of mutant Huntington toxicity via enhanced protein clearance. Nat Neurosci 2013; 16:562-70. [PMID: 23525043 DOI: 10.1038/nn.3367] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 02/26/2013] [Indexed: 02/08/2023]
Abstract
Huntington's disease is caused by expanded CAG repeats in HTT, conferring toxic gain of function on mutant HTT (mHTT) protein. Reducing mHTT amounts is postulated as a strategy for therapeutic intervention. We conducted genome-wide RNA interference screens for genes modifying mHTT abundance and identified 13 hits. We tested 10 in vivo in a Drosophila melanogaster Huntington's disease model, and 6 exhibited activity consistent with the in vitro screening results. Among these, negative regulator of ubiquitin-like protein 1 (NUB1) overexpression lowered mHTT in neuronal models and rescued mHTT-induced death. NUB1 reduces mHTT amounts by enhancing polyubiquitination and proteasomal degradation of mHTT protein. The process requires CUL3 and the ubiquitin-like protein NEDD8 necessary for CUL3 activation. As a potential approach to modulating NUB1 for treatment, interferon-β lowered mHTT and rescued neuronal toxicity through induction of NUB1. Thus, we have identified genes modifying endogenous mHTT using high-throughput screening and demonstrate NUB1 as an exemplar entry point for therapeutic intervention of Huntington's disease.
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Affiliation(s)
- Boxun Lu
- School of Life Sciences, Fudan University, Shanghai, China
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147
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Chhangani D, Mishra A. Protein quality control system in neurodegeneration: a healing company hard to beat but failure is fatal. Mol Neurobiol 2013; 48:141-56. [PMID: 23378031 DOI: 10.1007/s12035-013-8411-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 01/17/2013] [Indexed: 01/10/2023]
Abstract
A common feature in most neurodegenerative diseases and aging is the progressive accumulation of damaged proteins. Proteins are essential for all crucial biological functions. Under some notorious conditions, proteins loss their three dimensional native conformations and are converted into disordered aggregated structures. Such changes rise into pathological conditions and eventually cause serious protein conformation disorders. Protein aggregation and inclusion bodies formation mediated multifactorial proteotoxic stress has been reported in the progression of Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and Prion disease. Ongoing studies have been remarkably informative in providing a systematic outlook for better understanding the concept and fundamentals of protein misfolding and aggregations. However, the precise role of protein quality control system and precursors of this mechanism remains elusive. In this review, we highlight recent insights and discuss emerging cytoprotective strategies of cellular protein quality control system implicated in protein deposition diseases. Our current review provides a clear, understandable framework of protein quality control system that may offer the more suitable therapeutic strategies for protein-associated diseases.
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Affiliation(s)
- Deepak Chhangani
- Cellular and Molecular Neurobiology Laboratory, Indian Institute of Technology, Jodhpur, Rajasthan, 342011, India
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148
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Shimamoto S, Kubota Y, Yamaguchi F, Tokumitsu H, Kobayashi R. Ca2+/S100 proteins act as upstream regulators of the chaperone-associated ubiquitin ligase CHIP (C terminus of Hsc70-interacting protein). J Biol Chem 2013; 288:7158-68. [PMID: 23344957 DOI: 10.1074/jbc.m112.436758] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The U-box E3 ubiquitin ligase CHIP (C terminus of Hsc70-interacting protein) binds Hsp90 and/or Hsp70 via its tetratricopeptide repeat (TPR), facilitating ubiquitination of the chaperone-bound client proteins. Mechanisms that regulate the activity of CHIP are, at present, poorly understood. We previously reported that Ca(2+)/S100 proteins directly associate with the TPR proteins, such as Hsp70/Hsp90-organizing protein (Hop), kinesin light chain, Tom70, FKBP52, CyP40, and protein phosphatase 5 (PP5), leading to the dissociation of the interactions of the TPR proteins with their target proteins. Therefore, we have hypothesized that Ca(2+)/S100 proteins can interact with CHIP and regulate its function. GST pulldown assays indicated that Ca(2+)/S100A2 and S100P bind to the TPR domain and lead to interference with the interactions of CHIP with Hsp70, Hsp90, HSF1, and Smad1. In vitro ubiquitination assays indicated that Ca(2+)/S100A2 and S100P are efficient and specific inhibitors of CHIP-mediated ubiquitination of Hsp70, Hsp90, HSF1, and Smad1. Overexpression of S100A2 and S100P suppressed CHIP-chaperone complex-dependent mutant p53 ubiquitination and degradation in Hep3B cells. The association of the S100 proteins with CHIP provides a Ca(2+)-dependent regulatory mechanism for the ubiquitination and degradation of intracellular proteins by the CHIP-proteasome pathway.
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Affiliation(s)
- Seiko Shimamoto
- Department of Signal Transduction Sciences, Kagawa University Faculty of Medicine, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan
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Carman A, Kishinevsky S, Koren J, Lou W, Chiosis G. Chaperone-dependent Neurodegeneration: A Molecular Perspective on Therapeutic Intervention. ACTA ACUST UNITED AC 2013; 2013. [PMID: 25258700 PMCID: PMC4172285 DOI: 10.4172/2161-0460.s10-007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Maintenance of cellular homeostasis is regulated by the molecular chaperones. Under pathogenic conditions, aberrant proteins are triaged by the chaperone network. These aberrant proteins, known as "clients," have major roles in the pathogenesis of numerous neurological disorders, including tau in Alzheimer's disease, α-synuclein and LRRK2 in Parkinson's disease, SOD-1, TDP-43 and FUS in amyotrophic lateral sclerosis, and polyQ-expanded proteins such as huntingtin in Huntington's disease. Recent work has demonstrated that the use of chemical compounds which inhibit the activity of molecular chaperones subsequently alter the fate of aberrant clients. Inhibition of Hsp90 and Hsc70, two major molecular chaperones, has led to a greater understanding of how chaperone triage decisions are made and how perturbing the chaperone system can promote clearance of these pathogenic clients. Described here are major pathways and components of several prominent neurological disorders. Also discussed is how treatment with chaperone inhibitors, predominately Hsp90 inhibitors which are selective for a diseased state, can relieve the burden of aberrant client signaling in these neurological disorders.
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Affiliation(s)
- Aaron Carman
- Department of Molecular Pharmacology and Chemistry, Memorial Sloan-Kettering Cancer Centre, New York, NY, USA
| | - Sarah Kishinevsky
- Department of Molecular Pharmacology and Chemistry, Memorial Sloan-Kettering Cancer Centre, New York, NY, USA
| | - John Koren
- Department of Molecular Pharmacology and Chemistry, Memorial Sloan-Kettering Cancer Centre, New York, NY, USA
| | - Wenjie Lou
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, NY, USA
| | - Gabriela Chiosis
- Department of Molecular Pharmacology and Chemistry, Memorial Sloan-Kettering Cancer Centre, New York, NY, USA
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150
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Abstract
Poly-glutamine (polyQ) diseases are neurodegenerative disorders characterised by expanded CAG repeats in the causative genes whose proteins form inclusion bodies. Various E3 ubiquitin ligases are implicated in neurodegenerative disorders. We report that dysfunction of the SCF (Skp1-Cul1-F-box protein) complex, one of the most well-characterised ubiquitin ligases, is associated with pathology in polyQ diseases like Huntington's disease (HD) and Machado–Joseph disease (MJD). We found that Cullin1 (Cul1) and Skp1, core components of the SCF complex, are reduced in HD mice brain. A reduction in Cul1 levels was also observed in cellular HD model and fly models of both HD and MJD. We show that Cul1 is able to genetically modify mutant huntingtin aggregates because its silencing results in increased aggregate load in cultured cells. Moreover, we demonstrate that silencing dCul1 and dSkp1 in Drosophila results in increased aggregate load and enhanced polyQ-induced toxicity. Our results imply that reduced levels of SCF complex might contribute to polyQ disease pathology.
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