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Nowak B, Kozlowska E, Pawlik W, Fiszer A. Atrophin-1 Function and Dysfunction in Dentatorubral-Pallidoluysian Atrophy. Mov Disord 2023; 38:526-536. [PMID: 36809552 DOI: 10.1002/mds.29355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 01/19/2023] [Accepted: 01/31/2023] [Indexed: 02/23/2023] Open
Abstract
Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare, incurable genetic disease that belongs to the group of polyglutamine (polyQ) diseases. DRPLA is the most common in the Japanese population; however, its global prevalence is also increasing due to better clinical recognition. It is characterized by cerebellar ataxia, myoclonus, epilepsy, dementia, and chorea. DRPLA is caused by dynamic mutation of CAG repeat expansion in ATN1 gene encoding the atrophin-1 protein. In the cascade of molecular disturbances, the pathological form of atrophin-1 is the initial factor, which has not been precisely characterized so far. Reports indicate that DRPLA is associated with disrupted protein-protein interactions (in which an expanded polyQ tract plays a crucial role), as well as gene expression deregulation. There is a great need to design efficient therapy that would address the underlying neurodegenerative process and thus prevent or alleviate DRPLA symptoms. An in-depth understanding of the normal atrophin-1 function and mutant atrophin-1 dysfunction is crucial for this purpose. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Bartosz Nowak
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Emilia Kozlowska
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Weronika Pawlik
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Agnieszka Fiszer
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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2
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Handler HP, Duvick L, Mitchell JS, Cvetanovic M, Reighard M, Soles A, Mather KB, Rainwater O, Serres S, Nichols-Meade T, Coffin SL, You Y, Ruis BL, O'Callaghan B, Henzler C, Zoghbi HY, Orr HT. Decreasing mutant ATXN1 nuclear localization improves a spectrum of SCA1-like phenotypes and brain region transcriptomic profiles. Neuron 2023; 111:493-507.e6. [PMID: 36577403 PMCID: PMC9957934 DOI: 10.1016/j.neuron.2022.11.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 09/28/2022] [Accepted: 11/23/2022] [Indexed: 12/28/2022]
Abstract
Spinocerebellar ataxia type 1 (SCA1) is a dominant trinucleotide repeat neurodegenerative disease characterized by motor dysfunction, cognitive impairment, and premature death. Degeneration of cerebellar Purkinje cells is a frequent and prominent pathological feature of SCA1. We previously showed that transport of ATXN1 to Purkinje cell nuclei is required for pathology, where mutant ATXN1 alters transcription. To examine the role of ATXN1 nuclear localization broadly in SCA1-like disease pathogenesis, CRISPR-Cas9 was used to develop a mouse with an amino acid alteration (K772T) in the nuclear localization sequence of the expanded ATXN1 protein. Characterization of these mice indicates that proper nuclear localization of mutant ATXN1 contributes to many disease-like phenotypes including motor dysfunction, cognitive deficits, and premature lethality. RNA sequencing analysis of genes with expression corrected to WT levels in Atxn1175QK772T/2Q mice indicates that transcriptomic aspects of SCA1 pathogenesis differ between the cerebellum, brainstem, cerebral cortex, hippocampus, and striatum.
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Affiliation(s)
- Hillary P Handler
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Lisa Duvick
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jason S Mitchell
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Marija Cvetanovic
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Molly Reighard
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alyssa Soles
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kathleen B Mather
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Orion Rainwater
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Shannah Serres
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Tessa Nichols-Meade
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Stephanie L Coffin
- Program in Genetics & Genomics and Department of Molecular and Human Genetics, Baylor College of Medicine, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX 77030, USA
| | - Yun You
- Mouse Genetics Laboratory, University of Minnesota, Minneapolis, MN 55455, USA
| | - Brian L Ruis
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Brennon O'Callaghan
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Christine Henzler
- RISS Bioinformatics, Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455, USA
| | - Huda Y Zoghbi
- Departments of Molecular and Human Genetics, Pediatrics, and Howard Hughes Medical Institute, Baylor College of Medicine, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX 77030, USA
| | - Harry T Orr
- Institute of Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA; Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA.
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3
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Incebacak Eltemur RD, Nguyen HP, Weber JJ. Calpain-mediated proteolysis as driver and modulator of polyglutamine toxicity. Front Mol Neurosci 2022; 15:1020104. [PMID: 36385755 PMCID: PMC9648470 DOI: 10.3389/fnmol.2022.1020104] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 09/26/2022] [Indexed: 09/22/2023] Open
Abstract
Among posttranslational modifications, directed proteolytic processes have the strongest impact on protein integrity. They are executed by a variety of cellular machineries and lead to a wide range of molecular consequences. Compared to other forms of proteolytic enzymes, the class of calcium-activated calpains is considered as modulator proteases due to their limited proteolytic activity, which changes the structure and function of their target substrates. In the context of neurodegeneration and - in particular - polyglutamine disorders, proteolytic events have been linked to modulatory effects on the molecular pathogenesis by generating harmful breakdown products of disease proteins. These findings led to the formulation of the toxic fragment hypothesis, and calpains appeared to be one of the key players and auspicious therapeutic targets in Huntington disease and Machado Joseph disease. This review provides a current survey of the role of calpains in proteolytic processes found in polyglutamine disorders. Together with insights into general concepts behind toxic fragments and findings in polyglutamine disorders, this work aims to inspire researchers to broaden and deepen the knowledge in this field, which will help to evaluate calpain-mediated proteolysis as a unifying and therapeutically targetable posttranslational mechanism in neurodegeneration.
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Affiliation(s)
- Rana Dilara Incebacak Eltemur
- Department of Human Genetics, Ruhr University Bochum, Bochum, Germany
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Huu Phuc Nguyen
- Department of Human Genetics, Ruhr University Bochum, Bochum, Germany
| | - Jonasz Jeremiasz Weber
- Department of Human Genetics, Ruhr University Bochum, Bochum, Germany
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
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4
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Johnson SL, Tsou WL, Prifti MV, Harris AL, Todi SV. A survey of protein interactions and posttranslational modifications that influence the polyglutamine diseases. Front Mol Neurosci 2022; 15:974167. [PMID: 36187346 PMCID: PMC9515312 DOI: 10.3389/fnmol.2022.974167] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 07/27/2022] [Indexed: 01/20/2023] Open
Abstract
The presence and aggregation of misfolded proteins has deleterious effects in the nervous system. Among the various diseases caused by misfolded proteins is the family of the polyglutamine (polyQ) disorders. This family comprises nine members, all stemming from the same mutation—the abnormal elongation of a polyQ repeat in nine different proteins—which causes protein misfolding and aggregation, cellular dysfunction and disease. While it is the same type of mutation that causes them, each disease is distinct: it is influenced by regions and domains that surround the polyQ repeat; by proteins with which they interact; and by posttranslational modifications they receive. Here, we overview the role of non-polyQ regions that control the pathogenicity of the expanded polyQ repeat. We begin by introducing each polyQ disease, the genes affected, and the symptoms experienced by patients. Subsequently, we provide a survey of protein-protein interactions and posttranslational modifications that regulate polyQ toxicity. We conclude by discussing shared processes and pathways that bring some of the polyQ diseases together and may serve as common therapeutic entry points for this family of incurable disorders.
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Affiliation(s)
- Sean L. Johnson
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Wei-Ling Tsou
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Matthew V. Prifti
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
| | - Autumn L. Harris
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
- Maximizing Access to Research Careers (MARC) Program, Wayne State University, Detroit, MI, United States
| | - Sokol V. Todi
- Department of Pharmacology, Wayne State University, Detroit, MI, United States
- Maximizing Access to Research Careers (MARC) Program, Wayne State University, Detroit, MI, United States
- Department of Neurology, Wayne State University, Detroit, MI, United States
- *Correspondence: Sokol V. Todi,
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5
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A PolyQ Membrane Protein of Vibrio cholerae Acts as the Receptor for Phage Infection. J Virol 2021; 95:JVI.02245-20. [PMID: 33408174 DOI: 10.1128/jvi.02245-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 12/21/2020] [Indexed: 11/20/2022] Open
Abstract
Bacteriophage VP1 is a typing phage used for the phage subtyping of Vibrio cholerae O1 biotype El Tor, but the molecular mechanisms of its receptor recognition and the resistance of its host to infection are mostly unknown. In this study, we aimed to identify the host receptor and its role in resistance in natural VP1-resistant strains. Generating spontaneous resistance mutations and genome sequencing mutant strains found the polyQ protein VcpQ, which carries 46 glutamine residues in its Q-rich region, to be responsible for infection by VP1. VcpQ is a membrane protein and possibly forms homotrimers. VP1 adsorbed to V. cholerae through VcpQ. Sequence comparisons showed that 72% of natural VP1-resistant strains have fewer glutamines in the VcpQ Q-rich stretch than VP1-sensitive strains. This difference did not affect the membrane location and oligomer of VcpQ but abrogated VP1 adsorption. These mutant VcpQs did not recover VP1 infection sensitivity in a V. cholerae strain with vcpQ deleted. Our study revealed that the polyQ protein VcpQ is responsible for the binding of VP1 during its infection of V. cholerae and that glutamine residue reduction in VcpQ affects VP1 adsorption to likely be the main cause of VP1 resistance in natural resistant strains. The physiological functions of this polyQ protein in bacteria need further clarification; however, mutations in the polyQ stretch may endow V. cholerae with phage resistance and enhance survival against VP1 or related phages.IMPORTANCE Receptor recognition and binding by bacteriophage are the first step for its infection of bacterial cells. In this study, we found the Vibrio cholerae subtyping phage VP1 uses a polyQ protein named VcpQ (V. cholerae polyQ protein) as the receptor for VP1 infection. Our study reveals the receptor's recognition of phage VP1 during its adsorption and the VP1 resistance mechanism of the wild resistant V. cholerae strains bearing the mutagenesis in the receptor VcpQ. These mutations may confer the survival advantage on these resistant strains in the environment containing VP1 or its similar phages.
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La Rosa P, Petrillo S, Bertini ES, Piemonte F. Oxidative Stress in DNA Repeat Expansion Disorders: A Focus on NRF2 Signaling Involvement. Biomolecules 2020; 10:biom10050702. [PMID: 32369911 PMCID: PMC7277112 DOI: 10.3390/biom10050702] [Citation(s) in RCA: 15] [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: 04/10/2020] [Revised: 04/24/2020] [Accepted: 04/27/2020] [Indexed: 12/13/2022] Open
Abstract
DNA repeat expansion disorders are a group of neuromuscular and neurodegenerative diseases that arise from the inheritance of long tracts of nucleotide repetitions, located in the regulatory region, introns, or inside the coding sequence of a gene. Although loss of protein expression and/or the gain of function of its transcribed mRNA or translated product represent the major pathogenic effect of these pathologies, mitochondrial dysfunction and imbalance in redox homeostasis are reported as common features in these disorders, deeply affecting their severity and progression. In this review, we examine the role that the redox imbalance plays in the pathological mechanisms of DNA expansion disorders and the recent advances on antioxidant treatments, particularly focusing on the expression and the activity of the transcription factor NRF2, the main cellular regulator of the antioxidant response.
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7
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Hou X, Gong X, Zhang L, Li T, Yuan H, Xie Y, Peng Y, Qiu R, Xia K, Tang B, Jiang H. Identification of a potential exosomal biomarker in spinocerebellar ataxia Type 3/Machado-Joseph disease. Epigenomics 2019; 11:1037-1056. [PMID: 31144508 DOI: 10.2217/epi-2019-0081] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Aim: To identify spinocerebellar ataxia Type 3 (SCA3)-related exosomal biomarkers and the underlying mechanisms. Materials & methods: Exosomal RNAs from plasma and cerebrospinal fluid (CSF) were extracted from 24 SCA3 patients and 22 controls, respectively. Small RNA sequencing and quantitative PCR verification were performed. Gene ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the results were carried out. Results: One novel miRNA is notably downregulated in plasma-derived exosomes, while upregulated in CSF-derived exosomes of SCA3 patients. Besides, it is successively upregulated in CSF-derived exosomes from Type 1, Type 2 and Type 3 groups. The downstream target genes were enriched in protein processing in endoplasmic reticulum and axon guidance. Conclusion: One exosomal biomarker was identified in SCA3, and this is the first time to report an exosomal miRNA as a biomarker in SCA3 internationally.
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Affiliation(s)
- Xiaocan Hou
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Xuan Gong
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Longbo Zhang
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Tianjiao Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Hongyu Yuan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Yue Xie
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Yun Peng
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Rong Qiu
- School of Information Science & Engineering, Central South University, Changsha, Hunan 410008, PR China
| | - Kun Xia
- Laboratory of Medical Genetics, Central South University, Changsha, Hunan 410008, PR China
| | - Beisha Tang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China.,Laboratory of Medical Genetics, Central South University, Changsha, Hunan 410008, PR China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, PR China.,National Clinical Research Center for Geriatrics Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
| | - Hong Jiang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China.,Laboratory of Medical Genetics, Central South University, Changsha, Hunan 410008, PR China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, PR China.,National Clinical Research Center for Geriatrics Disorders, Xiangya Hospital, Central South University, Changsha, Hunan 410008, PR China
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8
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Palmer EE, Hong S, Al Zahrani F, Hashem MO, Aleisa FA, Ahmed HMJ, Kandula T, Macintosh R, Minoche AE, Puttick C, Gayevskiy V, Drew AP, Cowley MJ, Dinger M, Rosenfeld JA, Xiao R, Cho MT, Yakubu SF, Henderson LB, Guillen Sacoto MJ, Begtrup A, Hamad M, Shinawi M, Andrews MV, Jones MC, Lindstrom K, Bristol RE, Kayani S, Snyder M, Villanueva MM, Schteinschnaider A, Faivre L, Thauvin C, Vitobello A, Roscioli T, Kirk EP, Bye A, Merzaban J, Jaremko Ł, Jaremko M, Sachdev RK, Alkuraya FS, Arold ST. De Novo Variants Disrupting the HX Repeat Motif of ATN1 Cause a Recognizable Non-Progressive Neurocognitive Syndrome. Am J Hum Genet 2019; 104:542-552. [PMID: 30827498 DOI: 10.1016/j.ajhg.2019.01.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 01/23/2019] [Indexed: 01/15/2023] Open
Abstract
Polyglutamine expansions in the transcriptional co-repressor Atrophin-1, encoded by ATN1, cause the neurodegenerative condition dentatorubral-pallidoluysian atrophy (DRPLA) via a proposed novel toxic gain of function. We present detailed phenotypic information on eight unrelated individuals who have de novo missense and insertion variants within a conserved 16-amino-acid "HX repeat" motif of ATN1. Each of the affected individuals has severe cognitive impairment and hypotonia, a recognizable facial gestalt, and variable congenital anomalies. However, they lack the progressive symptoms typical of DRPLA neurodegeneration. To distinguish this subset of affected individuals from the DRPLA diagnosis, we suggest using the term CHEDDA (congenital hypotonia, epilepsy, developmental delay, digit abnormalities) to classify the condition. CHEDDA-related variants alter the particular structural features of the HX repeat motif, suggesting that CHEDDA results from perturbation of the structural and functional integrity of the HX repeat. We found several non-homologous human genes containing similar motifs of eight to 10 HX repeat sequences, including RERE, where disruptive variants in this motif have also been linked to a separate condition that causes neurocognitive and congenital anomalies. These findings suggest that perturbation of the HX motif might explain other Mendelian human conditions.
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9
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Karyopherin α-3 is a key protein in the pathogenesis of spinocerebellar ataxia type 3 controlling the nuclear localization of ataxin-3. Proc Natl Acad Sci U S A 2018; 115:E2624-E2633. [PMID: 29476013 DOI: 10.1073/pnas.1716071115] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spinocerebellar ataxia type 3 (SCA3) is a neurodegenerative disorder caused by a CAG expansion in the ATXN3 gene leading to a polyglutamine expansion in the ataxin-3 protein. The nuclear presence and aggregation of expanded ataxin-3 are critical steps in disease pathogenesis. To identify novel therapeutic targets, we investigated the nucleocytoplasmic transport system by screening a collection of importins and exportins that potentially modulate this nuclear localization. Using cell, Drosophila, and mouse models, we focused on three transport proteins, namely, CRM1, IPO13, KPNA3, and their respective Drosophila orthologs Emb, Cdm, and Kap-α3. While overexpression of CRM1/Emb demonstrated positive effects in Drosophila, KPNA3/Kap-α3 emerged as the most promising target, as knockdown via multiple RNAi lines demonstrated its ability to shuttle both truncated and full-length expanded ataxin-3, rescue neurodegeneration, restore photoreceptor formation, and reduce aggregation. Furthermore, KPNA3 knockout in SCA3 mice resulted in an amelioration of molecular and behavioral disturbances such as total activity, anxiety, and gait. Since KPNA3 is known to function as an import protein and recognize nuclear localization signals (NLSs), this work unites ataxin-3 structure to the nuclear pore machinery and provides a link between karyopherins, NLS signals, and polyglutamine disease, as well as demonstrates that KPNA3 is a key player in the pathogenesis of SCA3.
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10
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Du X, Gomez CM. Spinocerebellar [corrected] Ataxia Type 6: Molecular Mechanisms and Calcium Channel Genetics. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1049:147-173. [PMID: 29427102 DOI: 10.1007/978-3-319-71779-1_7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Spinocerebellar ataxia (SCA) type 6 is an autosomal dominant disease affecting cerebellar degeneration. Clinically, it is characterized by pure cerebellar dysfunction, slowly progressive unsteadiness of gait and stance, slurred speech, and abnormal eye movements with late onset. Pathological findings of SCA6 include a diffuse loss of Purkinje cells, predominantly in the cerebellar vermis. Genetically, SCA6 is caused by expansion of a trinucleotide CAG repeat in the last exon of longest isoform CACNA1A gene on chromosome 19p13.1-p13.2. Normal alleles have 4-18 repeats, while alleles causing disease contain 19-33 repeats. Due to presence of a novel internal ribosomal entry site (IRES) with the mRNA, CACNA1A encodes two structurally unrelated proteins with distinct functions within an overlapping open reading frame (ORF) of the same mRNA: (1) α1A subunit of P/Q-type voltage gated calcium channel; (2) α1ACT, a newly recognized transcription factor, with polyglutamine repeat at C-terminal end. Understanding the function of α1ACT in physiological and pathological conditions may elucidate the pathogenesis of SCA6. More importantly, the IRES, as the translational control element of α1ACT, provides a potential therapeutic target for the treatment of SCA6.
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Affiliation(s)
- Xiaofei Du
- Department of Neurology, The University of Chicago, Chicago, 60637, IL, USA
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11
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Deregulation of RNA Metabolism in Microsatellite Expansion Diseases. ADVANCES IN NEUROBIOLOGY 2018; 20:213-238. [PMID: 29916021 DOI: 10.1007/978-3-319-89689-2_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RNA metabolism impacts different steps of mRNA life cycle including splicing, polyadenylation, nucleo-cytoplasmic export, translation, and decay. Growing evidence indicates that defects in any of these steps lead to devastating diseases in humans. This chapter reviews the various RNA metabolic mechanisms that are disrupted in Myotonic Dystrophy-a trinucleotide repeat expansion disease-due to dysregulation of RNA-Binding Proteins. We also compare Myotonic Dystrophy to other microsatellite expansion disorders and describe how some of these mechanisms commonly exert direct versus indirect effects toward disease pathologies.
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12
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The CAG-polyglutamine repeat diseases: a clinical, molecular, genetic, and pathophysiologic nosology. HANDBOOK OF CLINICAL NEUROLOGY 2018; 147:143-170. [PMID: 29325609 DOI: 10.1016/b978-0-444-63233-3.00011-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Throughout the genome, unstable tandem nucleotide repeats can expand to cause a variety of neurologic disorders. Expansion of a CAG triplet repeat within a coding exon gives rise to an elongated polyglutamine (polyQ) tract in the resultant protein product, and accounts for a unique category of neurodegenerative disorders, known as the CAG-polyglutamine repeat diseases. The nine members of the CAG-polyglutamine disease family include spinal and bulbar muscular atrophy (SBMA), Huntington disease, dentatorubral pallidoluysian atrophy, and six spinocerebellar ataxias (SCA 1, 2, 3, 6, 7, and 17). All CAG-polyglutamine diseases are dominantly inherited, with the exception of SBMA, which is X-linked, and many CAG-polyglutamine diseases display anticipation, which is defined as increasing disease severity in successive generations of an affected kindred. Despite widespread expression of the different polyQ-expanded disease proteins throughout the body, each CAG-polyglutamine disease strikes a particular subset of neurons, although the mechanism for this cell-type selectivity remains poorly understood. While the different genes implicated in these disorders display amino acid homology only in the repeat tract domain, certain pathologic molecular processes have been implicated in almost all of the CAG-polyglutamine repeat diseases, including protein aggregation, proteolytic cleavage, transcription dysregulation, autophagy impairment, and mitochondrial dysfunction. Here we highlight the clinical and molecular genetic features of each distinct disorder, and then discuss common themes in CAG-polyglutamine disease pathogenesis, closing with emerging advances in therapy development.
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13
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Modulation of Molecular Chaperones in Huntington’s Disease and Other Polyglutamine Disorders. Mol Neurobiol 2016; 54:5829-5854. [DOI: 10.1007/s12035-016-0120-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 09/12/2016] [Indexed: 12/20/2022]
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14
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Krench M, Cho RW, Littleton JT. A Drosophila model of Huntington disease-like 2 exhibits nuclear toxicity and distinct pathogenic mechanisms from Huntington disease. Hum Mol Genet 2016; 25:3164-3177. [PMID: 27288455 DOI: 10.1093/hmg/ddw166] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 04/22/2016] [Accepted: 05/20/2016] [Indexed: 12/23/2022] Open
Abstract
Huntington disease-like 2 (HDL2) and Huntington disease (HD) are adult-onset neurodegenerative diseases characterized by movement disorders, psychiatric disturbances and cognitive decline. Brain tissue from HD and HDL2 patients shows degeneration of the striatum and ubiquitinated inclusions immunoreactive for polyglutamine (polyQ) antibodies. Despite these similarities, the diseases result from different genetic mutations. HD is caused by a CAG repeat expansion in the huntingtin (HTT) gene, while HDL2 results from an expansion at the junctophilin 3 (JPH3) locus. Recent evidence indicates that the HDL2 expansion may give rise to a toxic polyQ protein translated from an antisense mRNA derived from the JPH3 locus. To investigate this hypothesis, we generated and characterized a Drosophila HDL2 model and compared it with a previously established HD model. We find that neuronal expression of HDL2-Q15 is not toxic, while the expression of an expanded HDL2-Q138 protein is lethal. HDL2-Q138 forms large nuclear aggregates, with only smaller puncta observed in the cytoplasm. This is in contrast to what is observed in a Drosophila model of HD, where polyQ aggregates localize exclusively to the cytoplasm. Altering localization of HLD2 with the addition of a nuclear localization or nuclear export sequence demonstrates that nuclear accumulation is required for toxicity in the Drosophila HDL2 model. Directing HDL2-Q138 to the nucleus exacerbates toxicity in multiple tissue types, while confining HDL2-Q138 to the cytoplasm restores viability to control levels. We conclude that while HD and HDL2 have similar clinical profiles, distinct pathogenic mechanisms are likely to drive toxicity in Drosophila models of these disorders.
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Affiliation(s)
- Megan Krench
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences
| | - Richard W Cho
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences .,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Fan HC, Ho LI, Chi CS, Chen SJ, Peng GS, Chan TM, Lin SZ, Harn HJ. Polyglutamine (PolyQ) diseases: genetics to treatments. Cell Transplant 2015; 23:441-58. [PMID: 24816443 DOI: 10.3727/096368914x678454] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The polyglutamine (polyQ) diseases are a group of neurodegenerative disorders caused by expanded cytosine-adenine-guanine (CAG) repeats encoding a long polyQ tract in the respective proteins. To date, a total of nine polyQ disorders have been described: six spinocerebellar ataxias (SCA) types 1, 2, 6, 7, 17; Machado-Joseph disease (MJD/SCA3); Huntington's disease (HD); dentatorubral pallidoluysian atrophy (DRPLA); and spinal and bulbar muscular atrophy, X-linked 1 (SMAX1/SBMA). PolyQ diseases are characterized by the pathological expansion of CAG trinucleotide repeat in the translated region of unrelated genes. The translated polyQ is aggregated in the degenerated neurons leading to the dysfunction and degeneration of specific neuronal subpopulations. Although animal models of polyQ disease for understanding human pathology and accessing disease-modifying therapies in neurodegenerative diseases are available, there is neither a cure nor prevention for these diseases, and only symptomatic treatments for polyQ diseases currently exist. Long-term pharmacological treatment is so far disappointing, probably due to unwanted complications and decreasing drug efficacy. Cellular transplantation of stem cells may provide promising therapeutic avenues for restoration of the functions of degenerative and/or damaged neurons in polyQ diseases.
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Affiliation(s)
- Hueng-Chuen Fan
- Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
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16
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Truant R, Raymond LA, Xia J, Pinchev D, Burtnik A, Atwal RS. Canadian Association of Neurosciences Review: Polyglutamine Expansion Neurodegenerative Diseases. Can J Neurol Sci 2014; 33:278-91. [PMID: 17001815 DOI: 10.1017/s031716710000514x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
ABSTRACT:Since the early 1990s, DNA triplet repeat expansions have been found to be the cause in an ever increasing number of genetic neurologic diseases. A subset of this large family of genetic diseases has the expansion of a CAG DNA triplet in the open reading frame of a coding exon. The result of this DNA expansion is the expression of expanded glutamine amino acid repeat tracts in the affected proteins, leading to the term, Polyglutamine Diseases, which is applied to this sub-family of diseases. To date, nine distinct genes are known to be linked to polyglutamine diseases, including Huntington's disease, Machado-Joseph Disease and spinobulbar muscular atrophy or Kennedy's disease. Most of the polyglutamine diseases are characterized clinically as spinocerebellar ataxias. Here we discuss recent successes and advancements in polyglutamine disease research, comparing these different diseases with a common genetic flaw at the level of molecular biology and early drug design for a family of diseases where many new research tools for these genetic disorders have been developed. Polyglutamine disease research has successfully used interdisciplinary collaborative efforts, informative multiple mouse genetic models and advanced tools of pharmaceutical industry research to potentially serve as the prototype model of therapeutic research and development for rare neurodegenerative diseases.
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Affiliation(s)
- Ray Truant
- Department of Biochemistry and Biomedical Sciences McMaster University, Hamilton, ON, Canada
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17
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Abstract
The capacity to polymerize into amyloid fibrils is common to many proteins. While some proteins naturally form these fibrils to serve functional roles, amyloid is usually associated with pathogenic processes in which specific proteins aberrantly aggregate within cells or tissues. Though the contribution of amyloid fibrils to actual disease pathogenesis is not always clear, one possibility is that the titration of essential proteins from solution into aggregates contributes to the cellular degeneration common to many amyloid diseases. Using mammalian and yeast model systems, we recently showed that the common biophysical properties of amyloid aggregates--including strong resistance to dissolution--enable stringent purification and identification of both amyloid-forming and amyloid-associated proteins directly from cells. Strikingly, many proteins that were previously implicated in formation or clearance of intracellular aggregates, including several stress granule components, were found to co-aggregate with amyloid formed by a polyglutamine-expanded huntingtin fragment. This direct evaluation of proteins within aggregates can help identify new amyloid-forming proteins, as well as proteins that can indirectly contribute to disease mechanisms.
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Affiliation(s)
- Dmitry Kryndushkin
- Department of Pharmacology; Uniformed Services University of the Health Sciences; Bethesda, MD USA
| | - Maggie P Wear
- Department of Pharmacology; Uniformed Services University of the Health Sciences; Bethesda, MD USA
| | - Frank Shewmaker
- Department of Pharmacology; Uniformed Services University of the Health Sciences; Bethesda, MD USA
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Kryndushkin D, Pripuzova N, Burnett BG, Shewmaker F. Non-targeted identification of prions and amyloid-forming proteins from yeast and mammalian cells. J Biol Chem 2013; 288:27100-27111. [PMID: 23926098 DOI: 10.1074/jbc.m113.485359] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The formation of amyloid aggregates is implicated both as a primary cause of cellular degeneration in multiple human diseases and as a functional mechanism for providing extraordinary strength to large protein assemblies. The recent identification and characterization of several amyloid proteins from diverse organisms argues that the amyloid phenomenon is widespread in nature. Yet identifying new amyloid-forming proteins usually requires a priori knowledge of specific candidates. Amyloid fibers can resist heat, pressure, proteolysis, and denaturation by reagents such as urea or sodium dodecyl sulfate. Here we show that these properties can be exploited to identify naturally occurring amyloid-forming proteins directly from cell lysates. This proteomic-based approach utilizes a novel purification of amyloid aggregates followed by identification by mass spectrometry without the requirement for special genetic tools. We have validated this technique by blind identification of three amyloid-based yeast prions from laboratory and wild strains and disease-related polyglutamine proteins expressed in both yeast and mammalian cells. Furthermore, we found that polyglutamine aggregates specifically recruit some stress granule components, revealing a possible mechanism of toxicity. Therefore, core amyloid-forming proteins as well as strongly associated proteins can be identified directly from cells of diverse origin.
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Affiliation(s)
| | - Natalia Pripuzova
- Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892
| | - Barrington G Burnett
- Department of Anatomy, Physiology, and Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814
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Camero S, Benítez MJ, Jiménez JS. Anomalous Protein–DNA Interactions Behind Neurological Disorders. PROTEIN-NUCLEIC ACIDS INTERACTIONS 2013; 91:37-63. [DOI: 10.1016/b978-0-12-411637-5.00002-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Abstract
The autosomal dominant spinocerebellar ataxias (SCA) are a genetically heterogeneous group of neurodegenerative disorders characterized by progressive motor incoordination, in some cases with ataxia alone and in others in association with additional progressive neurological deficits. Spinocerebellar ataxia type 6 (SCA6) is the prototype of a pure cerebellar ataxia, associated with a severe form of progressive ataxia and cerebellar dysfunction. SCA6, originally classified as such by Zhuchenko et al. (1997), is caused by a CAG repeat expansion in the CACNA1A gene which encodes the α1A subunit of the P/Q-type voltage-gated calcium channel. SCA6 is one of ten polyglutamine-encoding CAG nucleotide repeat expansion disorders comprising other neurodegenerative disorders such as Huntington's disease. The present review describes clinical, genetic, and pathological manifestations associated with this illness. Currently, there is no treatment for this neurodegenerative disease. Successful therapeutic strategies must target a valid pathological mechanism; thus, understanding the underlying mechanisms of disease is crucial to finding a proper treatment. Hence, this chapter will discuss as well the molecular mechanisms possibly associated with SCA6 pathology and their implication for the development of future treatment.
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Affiliation(s)
- Ana Solodkin
- Department of Neurology, University of Chicago Medical Center, Chicago, IL 606337, USA.
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22
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Unstable Repeat Expansion in Neurodegenerative Dementias: Mechanisms of Disease. Dement Neurocogn Disord 2012. [DOI: 10.12779/dnd.2012.11.1.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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23
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Hinz J, Lehnhardt L, Zakrzewski S, Zhang G, Ignatova Z. Polyglutamine expansion alters the dynamics and molecular architecture of aggregates in dentatorubropallidoluysian atrophy. J Biol Chem 2011; 287:2068-78. [PMID: 22134925 DOI: 10.1074/jbc.m111.318915] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Preferential accumulation of mutant proteins in the nucleus has been suggested to be the molecular culprit that confers cellular toxicity in the neurodegenerative disorders caused by polyglutamine (polyQ) expansion. Here, we use dynamic imaging approaches, orthogonal cross-seeding, and composition analysis to examine the dynamics and structure of nuclear and cytoplasmic inclusions of atrophin-1, implicated in dentatorubropallidoluysian atrophy, a polyQ-based disease with complex clinical features. Our results reveal a large heterogeneity in the dynamics of the nuclear inclusions compared with the compact and immobile cytoplasmic aggregates. At least two types of inclusions of expanded atrophin-1 with different mobility of the molecular species and ability to exchange with the surrounding monomer pool coexist in the nucleus. Intriguingly, the enrichment of nuclear inclusions with slow dynamics parallels changes in the aggregate core architecture that are dominated by the polyQ stretch. We propose that the observed complexity in the dynamics of the nuclear inclusions provides a molecular explanation for the enhanced cellular toxicity of the nuclear aggregates in polyQ-based neurodegeneration.
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Affiliation(s)
- Justyna Hinz
- Institute of Biochemistry and Biology, University of Potsdam, 14467 Potsdam, Germany
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24
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Giacomello M, Hudec R, Lopreiato R. Huntington's disease, calcium, and mitochondria. Biofactors 2011; 37:206-18. [PMID: 21674644 DOI: 10.1002/biof.162] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 03/23/2011] [Indexed: 01/13/2023]
Abstract
Huntington's disease (HD) is caused by a mutation that increases the number of CAG repeats in the gene encoding for the protein Huntingtin (Htt). The mutation results in the pathological expansion of the polyQ stretch that is normally present within the N-terminal region of Htt. Even if Htt is ubiquitously expressed in tissues, the changes in the protein finally result in the clinical manifestation of motor and cognitive impairments observed in HD patients. The molecular ethiology of the disease is obscure: a number of cellular and animal models are used as essential tools in experimental approaches aimed at understanding it. Biochemical changes have been described that correlate with the malfunction of HD neurons (primarily in the striatum): consensus is gradually emerging that the dyshomeostasis of Ca(2+) and/or mitochondria stress are important factors in the linkage of the Htt mutation to the onset and progression of the disease. Here, we present a succint overview of the changes of Htt, of its possible effect on the transcription of critical genes and of its causative role in the disturbance of the neuronal Ca(2+) homeostasis. Particular emphasis will be placed on the role of mitochondria as key player in the molecular pathogenesis of the disease.
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25
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Chan WM, Tsoi H, Wu CC, Wong CH, Cheng TC, Li HY, Lau KF, Shaw PC, Perrimon N, Chan HYE. Expanded polyglutamine domain possesses nuclear export activity which modulates subcellular localization and toxicity of polyQ disease protein via exportin-1. Hum Mol Genet 2011; 20:1738-50. [PMID: 21300695 DOI: 10.1093/hmg/ddr049] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Polyglutamine (polyQ) diseases are a group of late-onset, progressive neurodegenerative disorders caused by CAG trinucleotide repeat expansion in the coding region of disease genes. The cell nucleus is an important site of pathology in polyQ diseases, and transcriptional dysregulation is one of the pathologic hallmarks observed. In this study, we showed that exportin-1 (Xpo1) regulates the nucleocytoplasmic distribution of expanded polyQ protein. We found that expanded polyQ protein, but not its unexpanded form, possesses nuclear export activity and interacts with Xpo1. Genetic manipulation of Xpo1 expression levels in transgenic Drosophila models of polyQ disease confirmed the specific nuclear export role of Xpo1 on expanded polyQ protein. Upon Xpo1 knockdown, the expanded polyQ protein was retained in the nucleus. The nuclear disease protein enhanced polyQ toxicity by binding to heat shock protein (hsp) gene promoter and abolished hsp gene induction. Further, we uncovered a developmental decline of Xpo1 protein levels in vivo that contributes to the accumulation of expanded polyQ protein in the nucleus of symptomatic polyQ transgenic mice. Taken together, we first showed that Xpo1 is a nuclear export receptor for expanded polyQ domain, and our findings establish a direct link between protein nuclear export and the progressive nature of polyQ neurodegeneration.
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Affiliation(s)
- Wing Man Chan
- Laboratory of Drosophila Research, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
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26
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Suzuki Y, Nakayama K, Hashimoto N, Yazawa I. Proteolytic processing regulates pathological accumulation in dentatorubral-pallidoluysian atrophy. FEBS J 2010; 277:4873-87. [PMID: 20977674 DOI: 10.1111/j.1742-4658.2010.07893.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Dentatorubral-pallidoluysian atrophy is caused by polyglutamine (polyQ) expansion in atrophin-1 (ATN1). Recent studies have shown that nuclear accumulation of ATN1 and cleaved fragments with expanded polyQ is the pathological process underlying neurodegeneration in dentatorubral-pallidoluysian atrophy. However, the mechanism underlying the proteolytic processing of ATN1 remains unclear. In the present study, we examined the proteolytic processing of ATN1 aiming to understand the mechanisms of ATN1 accumulation with polyQ expansion. Using COS-7 and Neuro2a cells that express the ATN1 gene, in which ATN1 was accumulated by increasing the number of polyQs, we identified a novel C-terminal fragment containing a polyQ tract. The mutant C-terminal fragment with expanded polyQ selectively accumulated in the cells, and this was also demonstrated in the brain tissues of patients with dentatorubral-pallidoluysian atrophy. Immunocytochemical and biochemical studies revealed that full-length ATN1 and C-terminal fragments displayed individual localization. The mutant C-terminal fragment was preferentially found in the cytoplasmic membrane/organelle and insoluble fractions. Accordingly, it is assumed that the proteolytic processing of ATN1 regulates the localization of C-terminal fragments. Accumulation of the C-terminal fragment was enhanced by inhibition of caspases in the cytoplasm of COS-7 cells. Collectively, these results suggest that the C-terminal fragment plays a principal role in the pathological accumulation of ATN1 in dentatorubral-pallidoluysian atrophy.
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Affiliation(s)
- Yasuyo Suzuki
- Laboratory of Research Resources, Research Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, Aichi, Japan
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27
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Zuccato C, Valenza M, Cattaneo E. Molecular Mechanisms and Potential Therapeutical Targets in Huntington's Disease. Physiol Rev 2010; 90:905-81. [DOI: 10.1152/physrev.00041.2009] [Citation(s) in RCA: 626] [Impact Index Per Article: 44.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the gene encoding for huntingtin protein. A lot has been learned about this disease since its first description in 1872 and the identification of its causative gene and mutation in 1993. We now know that the disease is characterized by several molecular and cellular abnormalities whose precise timing and relative roles in pathogenesis have yet to be understood. HD is triggered by the mutant protein, and both gain-of-function (of the mutant protein) and loss-of-function (of the normal protein) mechanisms are involved. Here we review the data that describe the emergence of the ancient huntingtin gene and of the polyglutamine trait during the last 800 million years of evolution. We focus on the known functions of wild-type huntingtin that are fundamental for the survival and functioning of the brain neurons that predominantly degenerate in HD. We summarize data indicating how the loss of these beneficial activities reduces the ability of these neurons to survive. We also review the different mechanisms by which the mutation in huntingtin causes toxicity. This may arise both from cell-autonomous processes and dysfunction of neuronal circuitries. We then focus on novel therapeutical targets and pathways and on the attractive option to counteract HD at its primary source, i.e., by blocking the production of the mutant protein. Strategies and technologies used to screen for candidate HD biomarkers and their potential application are presented. Furthermore, we discuss the opportunities offered by intracerebral cell transplantation and the likely need for these multiple routes into therapies to converge at some point as, ideally, one would wish to stop the disease process and, at the same time, possibly replace the damaged neurons.
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Affiliation(s)
- Chiara Zuccato
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milan, Italy
| | - Marta Valenza
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milan, Italy
| | - Elena Cattaneo
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milan, Italy
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28
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Nisoli I, Chauvin JP, Napoletano F, Calamita P, Zanin V, Fanto M, Charroux B. Neurodegeneration by polyglutamine Atrophin is not rescued by induction of autophagy. Cell Death Differ 2010; 17:1577-87. [DOI: 10.1038/cdd.2010.31] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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29
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Yu J, Ying M, Zhuang Y, Xu T, Han M, Wu X, Xu R. C-terminal deletion of the atrophin-1 protein results in growth retardation but not neurodegeneration in mice. Dev Dyn 2010; 238:2471-8. [PMID: 19681162 DOI: 10.1002/dvdy.22063] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dentatorubral-pallidoluysian atrophy (DRPLA) is a dominant hereditary neurodegenerative disorder caused by the expansion of a poly-glutamine (poly-Q) repeat in Atrophin-1 protein. Ectopic expression of a poly-Q expanded human Atrophin-1 is sufficient to induce DRPLA phenotypes in mice. However, it is still unclear whether the dominant effect of poly-Q expansion is due to the functional interference with wild-type Atrophin-1 proteins, which exist in both patients and transgenic mice. Here we report the generation and analysis of an Atrophin-1 targeting allele that expresses a truncated protein lacking both the poly-Q repeat and following C-terminal peptides. Homozygous mutants exhibit growth retardation and progressive male infertility, but no obvious signs of neurodegeneration. Moreover, the mutant allele neither blocked nor enhanced the neurodegenerative phenotypes caused by a poly-Q expanded transgene. These results support the model that poly-Q expanded Atrophin-1 proteins cause DRPLA in a manner independent of any functional interaction with wild-type Atrophin-1 proteins.
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Affiliation(s)
- Juehua Yu
- Institute of Developmental Biology and Molecular Medicine, School of Life Sciences, Fudan University, Shanghai, China
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30
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Antony PMA, Mäntele S, Mollenkopf P, Boy J, Kehlenbach RH, Riess O, Schmidt T. Identification and functional dissection of localization signals within ataxin-3. Neurobiol Dis 2009; 36:280-92. [DOI: 10.1016/j.nbd.2009.07.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 07/22/2009] [Accepted: 07/27/2009] [Indexed: 10/20/2022] Open
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31
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Reina CP, Zhong X, Pittman RN. Proteotoxic stress increases nuclear localization of ataxin-3. Hum Mol Genet 2009; 19:235-49. [PMID: 19843543 DOI: 10.1093/hmg/ddp482] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Spinocerebellar ataxia type 3 (SCA3)/Machado Joseph disease results from expansion of the polyglutamine domain in ataxin-3 (Atx3). Atx3 is a transcriptional co-repressor, as well as a deubiquitinating enzyme that appears to function in cellular pathways involved in protein homeostasis. In this study, we show that interactions of Atx3 with valosin-containing protein and hHR23B are dynamic and modulated by proteotoxic stresses. Heat shock, a general proteotoxic stress, also induced wild-type and pathogenic Atx3 to accumulate in the nucleus. Mapping studies showed that two regions of Atx3, the Josephin domain and the C-terminus, regulated heat shock-induced nuclear localization. Heat shock-induced nuclear localization of Atx3 was not affected by a casein kinase-2 inhibitor or by mutating a predicted nuclear localization signal. However, serine-111 of Atx3 was required for nuclear localization of the Josephin domain and regulated nuclear localization of full-length Atx3. Atx3 null cells were more sensitive to toxic effects of heat shock suggesting that Atx3 had a protective function in the cellular response to heat shock. Importantly, we found that oxidative stress also induced nuclear localization of Atx3; both wild-type and pathogenic Atx3 accumulated in the nucleus of SCA3 patient fibroblasts following oxidative stress. Heat shock and oxidative stress are the first processes identified that increase nuclear localization of Atx3. Observations in this study provide new and important insights for understanding SCA3 pathology as the nucleus is likely a key site for early pathogenesis.
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Affiliation(s)
- Christopher P Reina
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
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Bauer PO, Nukina N. The pathogenic mechanisms of polyglutamine diseases and current therapeutic strategies. J Neurochem 2009; 110:1737-65. [PMID: 19650870 DOI: 10.1111/j.1471-4159.2009.06302.x] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Expansion of CAG trinucleotide repeat within the coding region of several genes results in the production of proteins with expanded polyglutamine (PolyQ) stretch. The expression of these pathogenic proteins leads to PolyQ diseases, such as Huntington's disease or several types of spinocerebellar ataxias. This family of neurodegenerative disorders is characterized by constant progression of the symptoms and molecularly, by the accumulation of mutant proteins inside neurons causing their dysfunction and eventually death. So far, no effective therapy actually preventing the physical and/or mental decline has been developed. Experimental therapeutic strategies either target the levels or processing of mutant proteins in an attempt to prevent cellular deterioration, or they are aimed at the downstream pathologic effects to reverse or ameliorate the caused damages. Certain pathomechanistic aspects of PolyQ disorders are discussed here. Relevance of disease models and recent knowledge of therapeutic possibilities is reviewed and updated.
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Affiliation(s)
- Peter O Bauer
- Laboratory for Structural Neuropathology, RIKEN Brain Science Institute, Saitama, Japan
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33
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Havel LS, Li S, Li XJ. Nuclear accumulation of polyglutamine disease proteins and neuropathology. Mol Brain 2009; 2:21. [PMID: 19575804 PMCID: PMC2714308 DOI: 10.1186/1756-6606-2-21] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 07/03/2009] [Indexed: 11/10/2022] Open
Abstract
There are nine inherited neurodegenerative disorders caused by polyglutamine (polyQ) expansion in various disease proteins. Although these polyglutamine proteins have different functions and are localized in different subcellular regions, all the polyQ diseases share a common pathological feature: the nuclear accumulation of polyQ disease proteins and the formation of inclusions. The nuclear accumulation of polyQ proteins in turn leads to gene transcriptional dysregulation and neuropathology. Here we will discuss potential mechanisms behind the nuclear accumulation of mutant polyQ proteins, since an understanding of how polyQ proteins accumulate in the nucleus could help elucidate the pathogenesis of these diseases and develop their treatment.
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Affiliation(s)
- Lauren S Havel
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Sato T, Miura M, Yamada M, Yoshida T, Wood JD, Yazawa I, Masuda M, Suzuki T, Shin RM, Yau HJ, Liu FC, Shimohata T, Onodera O, Ross CA, Katsuki M, Takahashi H, Kano M, Aosaki T, Tsuji S. Severe neurological phenotypes of Q129 DRPLA transgenic mice serendipitously created by en masse expansion of CAG repeats in Q76 DRPLA mice. Hum Mol Genet 2008; 18:723-36. [PMID: 19039037 PMCID: PMC2638829 DOI: 10.1093/hmg/ddn403] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
We herein provide a thorough description of new transgenic mouse models for dentatorubral–pallidoluysian atrophy (DRPLA) harboring a single copy of the full-length human mutant DRPLA gene with 76 and 129 CAG repeats. The Q129 mouse line was unexpectedly obtained by en masse expansion based on the somatic instability of 76 CAG repeats in vivo. The mRNA expression levels of both Q76 and Q129 transgenes were each 80% of that of the endogenous mouse gene, whereas only the Q129 mice exhibited devastating progressive neurological phenotypes similar to those of juvenile-onset DRPLA patients. Electrophysiological studies of the Q129 mice demonstrated age-dependent and region-specific presynaptic dysfunction in the globus pallidus and cerebellum. Progressive shrinkage of distal dendrites of Purkinje cells and decreased currents through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and γ-aminobutyrate type A receptors in CA1 neurons were also observed. Neuropathological studies of the Q129 mice revealed progressive brain atrophy, but no obvious neuronal loss, associated with massive neuronal intranuclear accumulation (NIA) of mutant proteins with expanded polyglutamine stretches starting on postnatal day 4, whereas NIA in the Q76 mice appeared later with regional specificity to the vulnerable regions of DRPLA. Expression profile analyses demonstrated age-dependent down-regulation of genes, including those relevant to synaptic functions and CREB-dependent genes. These results suggest that neuronal dysfunction without neuronal death is the essential pathophysiologic process and that the age-dependent NIA is associated with nuclear dysfunction including transcriptional dysregulations. Thus, our Q129 mice should be highly valuable for investigating the mechanisms of disease pathogenesis and therapeutic interventions.
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Affiliation(s)
- Toshiya Sato
- Department of Comparative and Experimental Medicine, Brain Research Institute, Niigata University, Niigata, Japan
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35
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Wang L, Tsai CC. Atrophin proteins: an overview of a new class of nuclear receptor corepressors. NUCLEAR RECEPTOR SIGNALING 2008; 6:e009. [PMID: 19043594 PMCID: PMC2586093 DOI: 10.1621/nrs.06009] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Accepted: 09/22/2008] [Indexed: 12/12/2022]
Abstract
The normal development and physiological functions of multicellular organisms are regulated by complex gene transcriptional networks that include myriad transcription factors, their associating coregulators, and multiple chromatin-modifying factors. Aberrant gene transcriptional regulation resulting from mutations among these elements often leads to developmental defects and diseases. This review article concentrates on the Atrophin family proteins, including vertebrate Atrophin-1 (ATN1), vertebrate arginine-glutamic acid dipeptide repeats protein (RERE), and Drosophila Atrophin (Atro), which we recently identified as nuclear receptor corepressors. Disruption of Atrophin-mediated pathways causes multiple developmental defects in mouse, zebrafish, and Drosophila, while an aberrant form of ATN1 and altered expression levels of RERE are associated with neurodegenerative disease and cancer in humans, respectively. We here provide an overview of current knowledge about these Atrophin proteins. We hope that this information on Atrophin proteins may help stimulate fresh ideas about how this newly identified class of nuclear receptor corepressors aids specific nuclear receptors and other transcriptional factors in regulating gene transcription, manifesting physiological effects, and causing diseases.
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Affiliation(s)
- Lei Wang
- Department of Physiology and Biophysics, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey, USA
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Hull E, Spoja C, Cordova M, Cohlberg JA. Neurofilament protein aggregation in a cell line model system. Biochem Biophys Res Commun 2008; 366:73-9. [DOI: 10.1016/j.bbrc.2007.11.105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Accepted: 11/15/2007] [Indexed: 10/22/2022]
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Truant R, Atwal RS, Burtnik A. Nucleocytoplasmic trafficking and transcription effects of huntingtin in Huntington's disease. Prog Neurobiol 2007; 83:211-27. [PMID: 17240517 DOI: 10.1016/j.pneurobio.2006.11.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Revised: 11/29/2006] [Accepted: 11/30/2006] [Indexed: 01/08/2023]
Abstract
There are nine genetic neurodegenerative diseases caused by a similar genetic defect, a CAG DNA triplet-repeat expansion in the disease gene's open reading frame resulting in a polyglutamine expansion in the disease proteins. Despite the commonality of polyglutamine expansion, each of the polyglutamine diseases manifest as unique diseases, with some similarities, but important differences. These differences suggest that the context of the polyglutamine expansion is important to the mechanism of pathology of the disease proteins. Therefore, it is becoming increasingly paramount to understand the normal functions of these polyglutamine disease proteins, which include huntingtin, the polyglutamine-expanded protein in Huntington's disease (HD). Transcriptional dysregulation is seen in HD. Here we discuss the role of normal huntingtin in transcriptional regulation and misregulation in Huntington's disease in relation to potentially analogous model systems, and to other polyglutamine disease proteins. Huntingtin has functional roles in both the cytoplasm and the nucleus. One commonality of activity of polyglutamine disease proteins is at the level of protein dynamics and ability to import and export to and from the nucleus. Knowing the temporal location of huntingtin protein in response to signaling and neuronal communication could lead to valuable insights into an important trigger of HD pathology.
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Affiliation(s)
- Ray Truant
- McMaster University, Department of Biochemistry and Biomedical Sciences, HSC4H24A, 1200 Main Street West, Hamilton, Ontario, Canada L8N3Z5.
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38
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Abstract
The discovery that expansion of unstable repeats can cause a variety of neurological disorders has changed the landscape of disease-oriented research for several forms of mental retardation, Huntington disease, inherited ataxias, and muscular dystrophy. The dynamic nature of these mutations provided an explanation for the variable phenotype expressivity within a family. Beyond diagnosis and genetic counseling, the benefits from studying these disorders have been noted in both neurobiology and cell biology. Examples include insight about the role of translational control in synaptic plasticity, the role of RNA processing in the integrity of muscle and neuronal function, the importance of Fe-S-containing enzymes for cellular energy, and the dramatic effects of altering protein conformations on neuronal function and survival. It is exciting that within a span of 15 years, pathogenesis studies of this class of disorders are beginning to reveal pathways that are potential therapeutic targets.
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Affiliation(s)
- Harry T Orr
- Institute of Human Genetics, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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39
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Ng H, Pulst SM, Huynh DP. Ataxin-2 mediated cell death is dependent on domains downstream of the polyQ repeat. Exp Neurol 2007; 208:207-15. [PMID: 17949716 DOI: 10.1016/j.expneurol.2007.07.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 07/04/2007] [Accepted: 07/21/2007] [Indexed: 11/29/2022]
Abstract
Spinocerebellar ataxia 2 (SCA2) belongs to the group of neurodegenerative diseases caused by expansion of a polyglutamine (polyQ) domain. Overexpression of mutant ataxin-2 causes cell death and Golgi dispersion in cell culture as well as morphologic and functional changes in mouse models. To further define the mechanism of ataxin-2 induced cell death, we compared the cytotoxic effects of different domains of normal and mutant ataxin-2. N-terminal truncated ataxin-2(N) with expanded polyQ repeats did not form intranuclear inclusion and was less cytotoxic than the corresponding full-length ataxin-2. Ataxin-2(del42)[Q22], which lacks 42 amino acids (aa) within the Lsm-associated domain (LsmAD) necessary for Golgi localization, showed a diffuse cytoplasmic localization and was more toxic than wild type ataxin-2[Q22]. Mutant ataxin-2(del42)[Q108] displayed the same toxicity as ataxin-2[Q108], but did not disperse the Golgi apparatus to the extent seen with full-length mutant proteins. These observations confirm that ataxin-2 cytotoxicity increases with increasing polyQ expansion and Golgi dispersion and indicate that, in contrast to other polyQ diseases, N-terminal fragments containing the polyQ repeat are less toxic than full-length ataxin-2. Deletion of 42 aa in the Lsm-AD in ataxin-2 results in cytotoxicity without significant abnormalities in the Golgi apparatus. These findings suggest that the C-terminal domains are important for ataxin-2 cytotoxicity and that Golgi abnormalities may not be primary in the pathogenic process.
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Affiliation(s)
- Hiushan Ng
- Rose Moss Laboratory for Parkinson and Neurodegenerative Diseases, Burns and Allen Research Institute, and Division of Neurology, Cedars-Sinai Medical Center, USA
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40
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Young JE, Gouw L, Propp S, Sopher BL, Taylor J, Lin A, Hermel E, Logvinova A, Chen SF, Chen S, Bredesen DE, Truant R, Ptacek LJ, La Spada AR, Ellerby LM. Proteolytic cleavage of ataxin-7 by caspase-7 modulates cellular toxicity and transcriptional dysregulation. J Biol Chem 2007; 282:30150-60. [PMID: 17646170 DOI: 10.1074/jbc.m705265200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinocerebellar ataxia type 7 (SCA7) is a polyglutamine (polyQ) disorder characterized by specific degeneration of cerebellar, brainstem, and retinal neurons. Although they share little sequence homology, proteins implicated in polyQ disorders have common properties beyond their characteristic polyQ tract. These include the production of proteolytic fragments, nuclear accumulation, and processing by caspases. Here we report that ataxin-7 is cleaved by caspase-7, and we map two putative caspase-7 cleavage sites to Asp residues at positions 266 and 344 of the ataxin-7 protein. Site-directed mutagenesis of these two caspase-7 cleavage sites in the polyQ-expanded form of ataxin-7 produces an ataxin-7 D266N/D344N protein that is resistant to caspase cleavage. Although ataxin-7 displays toxicity, forms nuclear aggregates, and represses transcription in human embryonic kidney 293T cells in a polyQ length-dependent manner, expression of the non-cleavable D266N/D344N form of polyQ-expanded ataxin-7 attenuated cell death, aggregate formation, and transcriptional interference. Expression of the caspase-7 truncation product of ataxin-7-69Q or -92Q, which removes the putative nuclear export signal and nuclear localization signals of ataxin-7, showed increased cellular toxicity. We also detected N-terminal polyQ-expanded ataxin-7 cleavage products in SCA7 transgenic mice similar in size to those generated by caspase-7 cleavage. In a SCA7 transgenic mouse model, recruitment of caspase-7 into the nucleus by polyQ-expanded ataxin-7 correlated with its activation. Our results, thus, suggest that proteolytic processing of ataxin-7 by caspase-7 may contribute to SCA7 disease pathogenesis.
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Affiliation(s)
- Jessica E Young
- Buck Institute for Age Research, Novato, California, 94945, USA
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41
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Abstract
Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disorder caused by abnormal expansions of a trinucleotide CAG repeat in exon 47 of the CACNA1A gene, which encodes the alpha1A subunit of the P/Q-type voltage-gated calcium channel. The CAG repeat expansion is translated into an elongated polyglutamine tract in the carboxyl terminus of the alpha1A subunit. The alpha1A subunit is the main pore-forming subunit of the P/Q-type calcium channel. Patients with SCA6 suffer from a severe form of progressive ataxia and cerebellar dysfunction. Design of treatments for this disorder will depend on better definition of the mechanism of disease. As a disease arising from a mutation in an ion channel gene, SCA6 may behave as an ion channelopathy, and may respond to attempts to modulate or correct ion channel function. Alternatively, as a disease in which the mutant protein contains an expanded polyglutamine tract, SCA6 may respond to the targets of drug therapies developed for Huntington's disease and other polyglutamine disorders. In this review we will compare SCA6 to other polyglutamine diseases and channelopathies, and we will highlight recent advances in our understanding of alpha1A subunits and SCA6 pathology. We also propose a mechanism for how two seemingly divergent hypotheses can be combined into a cohesive model for disease progression.
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Affiliation(s)
- Holly B Kordasiewicz
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California 92093, USA
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42
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Halbleib JM, Nelson WJ. Cadherins in development: cell adhesion, sorting, and tissue morphogenesis. Genes Dev 2007; 20:3199-214. [PMID: 17158740 DOI: 10.1101/gad.1486806] [Citation(s) in RCA: 738] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tissue morphogenesis during development is dependent on activities of the cadherin family of cell-cell adhesion proteins that includes classical cadherins, protocadherins, and atypical cadherins (Fat, Dachsous, and Flamingo). The extracellular domain of cadherins contains characteristic repeats that regulate homophilic and heterophilic interactions during adhesion and cell sorting. Although cadherins may have originated to facilitate mechanical cell-cell adhesion, they have evolved to function in many other aspects of morphogenesis. These additional roles rely on cadherin interactions with a wide range of binding partners that modify their expression and adhesion activity by local regulation of the actin cytoskeleton and diverse signaling pathways. Here we examine how different members of the cadherin family act in different developmental contexts, and discuss the mechanisms involved.
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Affiliation(s)
- Jennifer M Halbleib
- Department of Biological Sciences, Stanford University, Stanford, California 94305, USA
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43
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Riley BE, Orr HT. Polyglutamine neurodegenerative diseases and regulation of transcription: assembling the puzzle. Genes Dev 2006; 20:2183-92. [PMID: 16912271 DOI: 10.1101/gad.1436506] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The polyglutamine disorders are a class of nine neuro-degenerative disorders that are inherited gain-of-function diseases caused by expansion of a translated CAG repeat. Even though the disease-causing proteins are widely expressed, specific collections of neurons are more susceptible in each disease, resulting in characteristic patterns of pathology and clinical symptoms. One hypothesis poses that altered protein function is fundamental to pathogenesis, with protein context of the expanded polyglutamine having key roles in disease-specific processes. This review will focus on the role of the disease-causing polyglutamine proteins in gene transcription and the extent to which the mutant proteins induce disruption of transcription.
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Affiliation(s)
- Brigit E Riley
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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44
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Kordasiewicz HB, Thompson RM, Clark HB, Gomez CM. C-termini of P/Q-type Ca2+ channel alpha1A subunits translocate to nuclei and promote polyglutamine-mediated toxicity. Hum Mol Genet 2006; 15:1587-99. [PMID: 16595610 DOI: 10.1093/hmg/ddl080] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
P/Q-type voltage-gated calcium channels are regulated, in part, through the cytoplasmic C-terminus of their alpha1A subunit. Genetic absence or alteration of the C-terminus leads to abnormal channel function and neurological disease. Here, we show that the terminal 60-75 kDa of the endogenous alpha1A C-terminus is cleaved from the full-length protein and is present in cell nuclei. Antiserum to the C-terminus (CT-2) labels both wild-type mouse and human Purkinje cell nuclei, but not leaner mouse cerebellum. Human embryonic kidney cells stably expressing beta3 and alpha2delta subunits and transiently transfected with full-length human alpha1A contain a 75 kDa CT-2 reactive peptide in their nuclear fraction. Primary granule cells transfected with C-terminally Green fluorescent protein (GFP)-tagged alpha1A exhibit GFP nuclear labeling. Nuclear translocation depends partly on the presence of three nuclear localization signals within the C-terminus. The C-terminal fragment bears a polyglutamine tract which, when expanded (Q33) as in spinocerebellar ataxia type 6 (SCA6), is toxic to cells. Moreover, polyglutamine-mediated toxicity is dependent on nuclear localization. Finally, in the absence of flanking sequence, the Q33 expansion alone does not kill cells. These results suggest a novel processing of the P/Q-type calcium channel and a potential mechanism for the pathogenesis of SCA6.
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Affiliation(s)
- Holly B Kordasiewicz
- Department of Neuroscience, Unviersity of Minnesota, 420 Delaware Street SE, Minneapolis, 55455, USA
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45
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Wang HL, Yeh TH, Chou AH, Kuo YL, Luo LJ, He CY, Huang PC, Li AH. Polyglutamine-expanded ataxin-7 activates mitochondrial apoptotic pathway of cerebellar neurons by upregulating Bax and downregulating Bcl-xL. Cell Signal 2006; 18:541-52. [PMID: 15964171 DOI: 10.1016/j.cellsig.2005.05.024] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Revised: 05/26/2005] [Accepted: 05/27/2005] [Indexed: 10/25/2022]
Abstract
Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder caused by polyglutamine-expanded ataxin-7. In the present investigation, we expressed disease-causing mutant ataxin-7-Q75 in the primary neuronal culture of cerebellum with the aid of recombinant adenoviruses. Subsequently, this in vitro cellular model of SCA7 was used to study the molecular mechanism by which mutant ataxin-7-Q75 induces neuronal death. TUNEL staining studies indicated that polyglutamine-expanded ataxin-7-Q75 caused apoptotic cell death of cultured cerebellar neurons. Mutant ataxin-7-Q75 induced the formation of active caspase-3 and caspase-9 without activating caspase-8. Polyglutamine-expanded ataxin-7-Q75 promoted the release of apoptogenic cytochrome-c and Smac from mitochondria, which was preceded by the downregulation of Bcl-x(L) protein and upregulation of Bax protein expression in cultured cerebellar neurons. Further real-time TaqMan RT-PCR assays showed that mutant ataxin-7-Q75 upregulated Bax mRNA level and downregulated Bcl-x(L) mRNA expression in the primary neuronal culture of cerebellum. The present study provides the evidence that polyglutamine-expanded ataxin-7-Q75 activates mitochondria-mediated apoptotic cascade and induces neuronal death by upregulating Bax expression and downregulating Bcl-x(L) expression of cerebellar neurons.
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Affiliation(s)
- Hung-Li Wang
- Department of Physiology, Chang Gung University School of Medicine, Kwei-San, Tao-Yuan, Taiwan, ROC.
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46
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Ignatova Z, Gierasch LM. Extended polyglutamine tracts cause aggregation and structural perturbation of an adjacent beta barrel protein. J Biol Chem 2006; 281:12959-67. [PMID: 16524881 DOI: 10.1074/jbc.m511523200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Formation of fibrillar intranuclear inclusions and related neuropathologies of the CAG-repeat disorders are linked to the expansion of a polyglutamine tract. Despite considerable effort, the etiology of these devastating diseases remains unclear. Although polypeptides with glutamine tracts recapitulate many of the observed characteristics of the gene products with CAG repeats, such as in vitro and in vivo aggregation and toxicity in model organisms, extended polyglutamine segments have also been reported to structurally perturb proteins into which they are inserted. Additionally, the sequence context of a polyglutamine tract has recently been shown to modulate its propensity to aggregate. These findings raise the possibility that indirect influences of the repeat tract on adjacent protein domains are contributory to pathologies. Destabilization of an adjacent domain may lead to loss of function, as well as favoring non-native structures in the neighboring domain causing them to be prone to intermolecular association and consequent aggregation. To explore these phenomena, we have used chimeras of a well studied globular protein and exon 1 of huntingtin. We find that expansion of the polyglutamine segment beyond the pathological threshold (>35 glutamines) results in structural perturbation of the neighboring protein whether the huntingtin exon is N- or C-terminal. Elongation of the polyglutamine region also substantially increases the propensity of the chimera to aggregate, both in vitro and in vivo, and in vitro aggregation kinetics of a chimera with a 53-glutamine repeat follow a nucleation polymerization mechanism with a monomeric nucleus.
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Affiliation(s)
- Zoya Ignatova
- Department of Biochemistry & Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
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47
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Taylor J, Grote SK, Xia J, Vandelft M, Graczyk J, Ellerby LM, La Spada AR, Truant R. Ataxin-7 can export from the nucleus via a conserved exportin-dependent signal. J Biol Chem 2006; 281:2730-9. [PMID: 16314424 DOI: 10.1074/jbc.m506751200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinocerebellar ataxia type 7 is a progressive neurodegenerative disorder caused by a CAG DNA triplet repeat expansion leading to an expanded polyglutamine tract in the ataxin-7 protein. Ataxin-7 appears to be a transcription factor and a component of the STAGA transcription coactivator complex. Here, using live cell imaging and inverted fluorescence recovery after photobleaching, we demonstrate that ataxin-7 has the ability to export from the nucleus via the CRM-1/exportin pathway and that ataxin-7 contains a classic leucine-type nuclear export signal (NES). We have precisely defined the location of this NES in ataxin-7 and found it to be fully conserved in all vertebrate species. Polyglutamine expansion was seen to reduce the nuclear export rate of mutant ataxin-7 relative to wild-type ataxin-7. Subtle point mutation of the NES in polyglutamine expanded ataxin-7 increased toxicity in primary cerebellar neurons in a polyglutamine length-dependent manner in the context of full-length ataxin-7. Our results add ataxin-7 to a growing list of polyglutamine disease proteins that are capable of nuclear shuttling, and we define an activity of ataxin-7 in the STAGA complex of trafficking between the nucleus and cytoplasm.
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Affiliation(s)
- Jillian Taylor
- Department of Biochemistry and Biomedical Sciences, McMaster University, HSC4H45 Hamilton, Ontario L8N3Z5 Canada
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48
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Chou AH, Yeh TH, Kuo YL, Kao YC, Jou MJ, Hsu CY, Tsai SR, Kakizuka A, Wang HL. Polyglutamine-expanded ataxin-3 activates mitochondrial apoptotic pathway by upregulating Bax and downregulating Bcl-xL. Neurobiol Dis 2006; 21:333-45. [PMID: 16112867 DOI: 10.1016/j.nbd.2005.07.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Revised: 07/27/2005] [Accepted: 07/27/2005] [Indexed: 11/17/2022] Open
Abstract
Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant neurodegenerative disease caused by polyglutamine-expanded ataxin-3. In the present study, we expressed disease-causing mutant ataxin-3-Q79 in neuronal cultures of cerebellum, striatum and substantia nigra by using recombinant adenoviruses. Subsequently, SCA3 cellular model was used to investigate the molecular mechanism by which ataxin-3-Q79 causes neuronal death. TUNEL staining studies showed that ataxin-3-Q79 induced apoptotic death of cerebellar, striatal or substantia nigra neurons. Ataxin-3-Q79 activated caspase-3 and caspase-9 without inducing the formation of active caspase-8. Ataxin-3-Q79 promoted mitochondrial release of cytochrome c and Smac, which was preceded by the upregulation of Bax protein and downregulation of Bcl-x(L) protein expression. Real-time TaqMan RT-PCR assays demonstrated that ataxin-3-Q79 upregulated Bax mRNA level and downregulated Bcl-xL mRNA expression in striatal, cerebellar and substantia nigra neurons. Our results suggest that polyglutamine-expanded ataxin-3-Q79 activates mitochondrial apoptotic pathway and induces neuronal death by upregulating Bax expression and downregulating Bcl-xL expression.
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Affiliation(s)
- An-Hsun Chou
- Department of Anesthesiology, Chang Gung Memorial Hospital, Taiwan, ROC
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49
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Charroux B, Freeman M, Kerridge S, Baonza A. Atrophin contributes to the negative regulation of epidermal growth factor receptor signaling in Drosophila. Dev Biol 2006; 291:278-90. [PMID: 16445904 DOI: 10.1016/j.ydbio.2005.12.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Revised: 11/21/2005] [Accepted: 12/06/2005] [Indexed: 11/18/2022]
Abstract
Dentato-rubral and pallido-luysian atrophy (DRPLA) is a dominant, progressive neurodegenerative disease caused by the expansion of polyglutamine repeats within the human Atrophin-1 protein. Drosophila Atrophin and its human orthologue are thought to function as transcriptional co-repressors. Here, we report that Drosophila Atrophin participates in the negative regulation of Epidermal Growth Factor Receptor (EGFR) signaling both in the wing and the eye imaginal discs. In the wing pouch, Atrophin loss of function clones induces cell autonomous expression of the EGFR target gene Delta, and the formation of extra vein tissue, while overexpression of Atrophin inhibits EGFR-dependent vein formation. In the eye, Atrophin cooperates with other negative regulators of the EGFR signaling to prevent the differentiation of surplus photoreceptor cells and to repress Delta expression. Overexpression of Atrophin in the eye reduces the EGFR-dependent recruitment of cone cells. In both the eye and wing, epistasis tests show that Atrophin acts downstream or in parallel to the MAP kinase rolled to modulate EGFR signaling outputs. We show that Atrophin genetically cooperates with the nuclear repressor Yan to inhibit the EGFR signaling activity. Finally, we have found that expression of pathogenic or normal forms of human Atrophin-1 in the wing promotes wing vein differentiation and acts as dominant negative proteins inhibiting endogenous fly Atrophin activity.
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Affiliation(s)
- Bernard Charroux
- Laboratoire de Génétique et Physiologie du Développement, UMR 6545 CNRS-Université, IBDM-CNRS-Université de la Méditerranée, Marseille Cedex 09 13288, France
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50
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Abstract
Huntington's disease (HD) is a progressive neurodegenerative disorder that generally begins in middle age with abnormalities of movement, cognition, personality, and mood. Neuronal loss is most marked among the medium-sized projection neurons of the dorsal striatum. HD is an autosomal dominant genetic disorder caused by a CAG expansion in exon 1 of the HD gene, encoding an expanded polyglutamine (polyQ) tract near the N-terminus of the protein huntingtin. Despite identification of the gene mutation more than a decade ago, the normal function of this ubiquitously expressed protein is still under investigation and the mechanisms underlying selective neurodegeneration in HD remain poorly understood. Detailed postmortem analyses of brains of HD patients have provided important clues, and HD transgenic and knock-in mouse models have facilitated investigations into potential pathogenic mechanisms. Subcellular fractionation and immunolocalization studies suggest a role for huntingtin in organelle transport, protein trafficking, and regulation of energy metabolism. Consistent with this, evidence from vertebrate and invertebrate models of HD indicates that expression of the polyQ-expanded form of huntingtin results in early impairment of axonal transport and mitochondrial function. As well, alteration in activity of the N-methyl-d-aspartate (NMDA) type glutamate receptor, which has been implicated as a main mediator of excitotoxic neuronal death, especially in the striatum, is an early effect of mutant huntingtin. Proteolysis and nuclear localization of huntingtin also occur relatively early, while formation of ubiquitinated aggregates of huntingtin and transcriptional dysregulation occur as late effects of the gene mutation. Although each of these processes may contribute to neuronal loss in HD, here we review the data to support a strong role for NMDA receptor (NMDAR)-mediated excitotoxicity and mitochondrial dysfunction in conferring selective neuronal vulnerability in HD.
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Affiliation(s)
- Catherine M Cowan
- Department of Psychiatry, Division of Neuroscience, Brain Research Centre University of British Columbia, Vancouver, British Columbia V6T 1Z3
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