1
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Sun X, Liu L, Wu C, Li X, Guo J, Zhang J, Guan J, Wang N, Gu L, Yang XW, Li GM. Mutant huntingtin protein induces MLH1 degradation, DNA hyperexcision, and cGAS-STING-dependent apoptosis. Proc Natl Acad Sci U S A 2024; 121:e2313652121. [PMID: 38498709 PMCID: PMC10990133 DOI: 10.1073/pnas.2313652121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 01/27/2024] [Indexed: 03/20/2024] Open
Abstract
Huntington's disease (HD) is an inherited neurodegenerative disorder caused by an expanded CAG repeat in the huntingtin (HTT) gene. The repeat-expanded HTT encodes a mutated HTT (mHTT), which is known to induce DNA double-strand breaks (DSBs), activation of the cGAS-STING pathway, and apoptosis in HD. However, the mechanism by which mHTT triggers these events is unknown. Here, we show that HTT interacts with both exonuclease 1 (Exo1) and MutLα (MLH1-PMS2), a negative regulator of Exo1. While the HTT-Exo1 interaction suppresses the Exo1-catalyzed DNA end resection during DSB repair, the HTT-MutLα interaction functions to stabilize MLH1. However, mHTT displays a significantly reduced interaction with Exo1 or MutLα, thereby losing the ability to regulate Exo1. Thus, cells expressing mHTT exhibit rapid MLH1 degradation and hyperactive DNA excision, which causes severe DNA damage and cytosolic DNA accumulation. This activates the cGAS-STING pathway to mediate apoptosis. Therefore, we have identified unique functions for both HTT and mHTT in modulating DNA repair and the cGAS-STING pathway-mediated apoptosis by interacting with MLH1. Our work elucidates the mechanism by which mHTT causes HD.
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Affiliation(s)
- Xiao Sun
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
- The Ministry of Education Key Laboratory of Reproductive Genetics, Department of Reproductive Endocrinology, Women’s Hospital, Zhejiang University School of Medicine, Hangzhou310006, China
| | - Lu Liu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
| | - Chao Wu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
| | - Xueying Li
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
| | - Jinzhen Guo
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
| | - Junqiu Zhang
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
| | - Junhong Guan
- Cui-ying Experimental Center, Lanzhou University Second Hospital, Lanzhou730030, China
| | - Nan Wang
- Center for Neurobehavioral Genetics, Semel Institute for Neuroscience & Human behavior, University of California, Los Angeles, CA90095
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Liya Gu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
| | - X. Willian Yang
- Center for Neurobehavioral Genetics, Semel Institute for Neuroscience & Human behavior, University of California, Los Angeles, CA90095
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Guo-Min Li
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX75390
- Institute for Cancer Research, Chinese Institutes for Medical Research, Beijing100069, China
- School of Basic Medical Sciences, Capital Medical University, Beijing100069, China
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2
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Erekat NS. Apoptosis and its therapeutic implications in neurodegenerative diseases. Clin Anat 2021; 35:65-78. [PMID: 34558138 DOI: 10.1002/ca.23792] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 09/19/2021] [Accepted: 09/21/2021] [Indexed: 12/18/2022]
Abstract
Neurodegenerative disorders are characterized by progressive loss of particular populations of neurons. Apoptosis has been implicated in the pathogenesis of neurodegenerative diseases, including Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. In this review, we focus on the existing notions relevant to comprehending the apoptotic death process, including the morphological features, mediators and regulators of cellular apoptosis. We also highlight the evidence of neuronal apoptotic death in Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. Additionally, we present evidence of potential therapeutic agents that could modify the apoptotic pathway in the aforementioned neurodegenerative diseases and delay disease progression. Finally, we review the clinical trials that were conducted to evaluate the use of anti-apoptotic drugs in the treatment of the aforementioned neurodegenerative diseases, in order to highlight the essential need for early detection and intervention of neurodegenerative diseases in humans.
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Affiliation(s)
- Nour S Erekat
- Department of Anatomy, Faculty of Medicine, Jordan University of Science and Technology, Irbid, Jordan
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3
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Annesley SJ, Fisher PR. Lymphoblastoid Cell Lines as Models to Study Mitochondrial Function in Neurological Disorders. Int J Mol Sci 2021; 22:4536. [PMID: 33926115 PMCID: PMC8123577 DOI: 10.3390/ijms22094536] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/23/2021] [Accepted: 04/24/2021] [Indexed: 12/12/2022] Open
Abstract
Neurological disorders, including neurodegenerative diseases, are collectively a major cause of death and disability worldwide. Whilst the underlying disease mechanisms remain elusive, altered mitochondrial function has been clearly implicated and is a key area of study in these disorders. Studying mitochondrial function in these disorders is difficult due to the inaccessibility of brain tissue, which is the key tissue affected in these diseases. To overcome this issue, numerous cell models have been used, each providing unique benefits and limitations. Here, we focussed on the use of lymphoblastoid cell lines (LCLs) to study mitochondrial function in neurological disorders. LCLs have long been used as tools for genomic analyses, but here we described their use in functional studies specifically in regard to mitochondrial function. These models have enabled characterisation of the underlying mitochondrial defect, identification of altered signalling pathways and proteins, differences in mitochondrial function between subsets of particular disorders and identification of biomarkers of the disease. The examples provided here suggest that these cells will be useful for development of diagnostic tests (which in most cases do not exist), identification of drug targets and testing of pharmacological agents, and are a worthwhile model for studying mitochondrial function in neurological disorders.
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Affiliation(s)
- Sarah Jane Annesley
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC 3086, Australia;
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4
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Eshraghi M, Karunadharma PP, Blin J, Shahani N, Ricci EP, Michel A, Urban NT, Galli N, Sharma M, Ramírez-Jarquín UN, Florescu K, Hernandez J, Subramaniam S. Mutant Huntingtin stalls ribosomes and represses protein synthesis in a cellular model of Huntington disease. Nat Commun 2021; 12:1461. [PMID: 33674575 PMCID: PMC7935949 DOI: 10.1038/s41467-021-21637-y] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 01/29/2021] [Indexed: 02/08/2023] Open
Abstract
The polyglutamine expansion of huntingtin (mHTT) causes Huntington disease (HD) and neurodegeneration, but the mechanisms remain unclear. Here, we found that mHtt promotes ribosome stalling and suppresses protein synthesis in mouse HD striatal neuronal cells. Depletion of mHtt enhances protein synthesis and increases the speed of ribosomal translocation, while mHtt directly inhibits protein synthesis in vitro. Fmrp, a known regulator of ribosome stalling, is upregulated in HD, but its depletion has no discernible effect on protein synthesis or ribosome stalling in HD cells. We found interactions of ribosomal proteins and translating ribosomes with mHtt. High-resolution global ribosome footprint profiling (Ribo-Seq) and mRNA-Seq indicates a widespread shift in ribosome occupancy toward the 5' and 3' end and unique single-codon pauses on selected mRNA targets in HD cells, compared to controls. Thus, mHtt impedes ribosomal translocation during translation elongation, a mechanistic defect that can be exploited for HD therapeutics.
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Affiliation(s)
- Mehdi Eshraghi
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Pabalu P. Karunadharma
- grid.214007.00000000122199231The Scripps Research Institute, Genomic Core, Jupiter, FL USA
| | - Juliana Blin
- grid.462957.b0000 0004 0598 0706Laboratory of Biology and Cellular Modelling at Ecole Normale Supérieure of Lyon, RNA Metabolism in Immunity and Infection Lab, LBMC, Lyon, France
| | - Neelam Shahani
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Emiliano P. Ricci
- grid.462957.b0000 0004 0598 0706Laboratory of Biology and Cellular Modelling at Ecole Normale Supérieure of Lyon, RNA Metabolism in Immunity and Infection Lab, LBMC, Lyon, France
| | | | | | - Nicole Galli
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Manish Sharma
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Uri Nimrod Ramírez-Jarquín
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Katie Florescu
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Jennifer Hernandez
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
| | - Srinivasa Subramaniam
- grid.214007.00000000122199231The Scripps Research Institute, Department of Neuroscience, Jupiter, FL USA
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5
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A Rationale for Hypoxic and Chemical Conditioning in Huntington's Disease. Int J Mol Sci 2021; 22:ijms22020582. [PMID: 33430140 PMCID: PMC7826574 DOI: 10.3390/ijms22020582] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 12/23/2020] [Accepted: 01/05/2021] [Indexed: 12/17/2022] Open
Abstract
Neurodegenerative diseases are characterized by adverse cellular environments and pathological alterations causing neurodegeneration in distinct brain regions. This development is triggered or facilitated by conditions such as hypoxia, ischemia or inflammation and is associated with disruptions of fundamental cellular functions, including metabolic and ion homeostasis. Targeting intracellular downstream consequences to specifically reverse these pathological changes proved difficult to translate to clinical settings. Here, we discuss the potential of more holistic approaches with the purpose to re-establish a healthy cellular environment and to promote cellular resilience. We review the involvement of important molecular pathways (e.g., the sphingosine, δ-opioid receptor or N-Methyl-D-aspartate (NMDA) receptor pathways) in neuroprotective hypoxic conditioning effects and how these pathways can be targeted for chemical conditioning. Despite the present scarcity of knowledge on the efficacy of such approaches in neurodegeneration, the specific characteristics of Huntington’s disease may make it particularly amenable for such conditioning techniques. Not only do classical features of neurodegenerative diseases like mitochondrial dysfunction, oxidative stress and inflammation support this assumption, but also specific Huntington’s disease characteristics: a relatively young age of neurodegeneration, molecular overlap of related pathologies with hypoxic adaptations and sensitivity to brain hypoxia. The aim of this review is to discuss several molecular pathways in relation to hypoxic adaptations that have potential as drug targets in neurodegenerative diseases. We will extract the relevance for Huntington’s disease from this knowledge base.
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6
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Malankhanova T, Suldina L, Grigor’eva E, Medvedev S, Minina J, Morozova K, Kiseleva E, Zakian S, Malakhova A. A Human Induced Pluripotent Stem Cell-Derived Isogenic Model of Huntington's Disease Based on Neuronal Cells Has Several Relevant Phenotypic Abnormalities. J Pers Med 2020; 10:jpm10040215. [PMID: 33182269 PMCID: PMC7712151 DOI: 10.3390/jpm10040215] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/02/2020] [Accepted: 11/04/2020] [Indexed: 12/30/2022] Open
Abstract
Huntington's disease (HD) is a severe neurodegenerative disorder caused by a CAG triplet expansion in the first exon of the HTT gene. Here we report the introduction of an HD mutation into the genome of healthy human embryonic fibroblasts through CRISPR/Cas9-mediated homologous recombination. We verified the specificity of the created HTT-editing system and confirmed the absence of undesirable genomic modifications at off-target sites. We showed that both mutant and control isogenic induced pluripotent stem cells (iPSCs) derived by reprogramming of the fibroblast clones can be differentiated into striatal medium spiny neurons. We next demonstrated phenotypic abnormalities in the mutant iPSC-derived neural cells, including impaired neural rosette formation and increased sensitivity to growth factor withdrawal. Moreover, using electron microscopic analysis, we detected a series of ultrastructural defects in the mutant neurons, which did not contain huntingtin aggregates, suggesting that these defects appear early in HD development. Thus, our study describes creation of a new isogenic iPSC-based cell system that models HD and recapitulates HD-specific disturbances in the mutant cells, including some ultrastructural features implemented for the first time.
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7
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Di Pardo A, Pepe G, Castaldo S, Marracino F, Capocci L, Amico E, Madonna M, Giova S, Jeong SK, Park BM, Park BD, Maglione V. Stimulation of Sphingosine Kinase 1 (SPHK1) Is Beneficial in a Huntington's Disease Pre-clinical Model. Front Mol Neurosci 2019; 12:100. [PMID: 31068790 PMCID: PMC6491579 DOI: 10.3389/fnmol.2019.00100] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 04/03/2019] [Indexed: 12/19/2022] Open
Abstract
Although several agents have been identified to provide therapeutic benefits in Huntington disease (HD), the number of conventionally used treatments remains limited and only symptomatic. Thus, it is plausible that the need to identify new therapeutic targets for the development of alternative and more effective treatments is becoming increasingly urgent. Recently, the sphingosine-1-phosphate (S1P) axis has been reported to be a valid potential novel molecular target for therapy development in HD. Modulation of aberrant metabolism of S1P in HD has been proved to exert neuroprotective action in vitro settings including human HD iPSC-derived neurons. In this study, we investigated whether promoting S1P production by stimulating Sphingosine Kinase 1 (SPHK1) by the selective activator, K6PC-5, may have therapeutic benefit in vivo in R6/2 HD mouse model. Our findings indicate that chronic administration of 0.05 mg/kg K6PC-5 exerted an overall beneficial effect in R6/2 mice. It significantly slowed down the progressive motor deficit associated with disease progression, modulated S1P metabolism, evoked the activation of pro-survival pathways and markedly reduced the toxic mutant huntingtin (mHtt) aggregation. These results suggest that K6PC-5 may represent a future therapeutic option in HD and may potentially counteract the perturbed brain function induced by deregulated S1P pathways.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Se Kyoo Jeong
- Department of Cosmetic Science, Seowon University, Cheongju, South Korea
| | - Bu-Mahn Park
- NeoPharm USA Inc., Engelwood Cliffs, NJ, United States
| | - Byeong Deog Park
- Dr. Raymond Laboratories, Inc., Englewood Cliffs, NJ, United States
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8
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Di Pardo A, Castaldo S, Amico E, Pepe G, Marracino F, Capocci L, Giovannelli A, Madonna M, van Bergeijk J, Buttari F, van der Kam E, Maglione V. Stimulation of S1PR5 with A-971432, a selective agonist, preserves blood-brain barrier integrity and exerts therapeutic effect in an animal model of Huntington's disease. Hum Mol Genet 2019; 27:2490-2501. [PMID: 29688337 DOI: 10.1093/hmg/ddy153] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 04/19/2018] [Indexed: 12/21/2022] Open
Abstract
Huntington's disease (HD) is the most common neurodegenerative disorder for which no effective cure is yet available. Although several agents have been identified to provide benefits so far, the number of therapeutic options remains limited with only symptomatic treatment available. Over the past few years, we have demonstrated that sphingolipid-based approaches may open the door to new and more targeted treatments for the disease. In this study, we investigated the therapeutic potential of stimulating sphingosine-1-phosphate (S1P) receptor 5 by the new selective agonist A-971432 (provided by AbbVie) in R6/2 mice, a widely used HD animal model. Chronic administration of low-dose (0.1 mg/kg) A-971432 slowed down the progression of the disease and significantly prolonged lifespan in symptomatic R6/2 mice. Such beneficial effects were associated with activation of pro-survival pathways (BDNF, AKT and ERK) and with reduction of mutant huntingtin aggregation. A-971432 also protected blood-brain barrier (BBB) homeostasis in the same mice. Interestingly, when administered early in the disease, before any overt symptoms, A-971432 completely protected HD mice from the classic progressive motor deficit and preserved BBB integrity. Beside representing a promising strategy to take into consideration for the development of alternative therapeutic options for HD, selective stimulation of S1P receptor 5 may be also seen as an effective approach to target brain vasculature defects in the disease.
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Affiliation(s)
- Alba Di Pardo
- IRCCS Neuromed, Localitá Camerelle, Pozzilli (IS), Italy
| | | | - Enrico Amico
- IRCCS Neuromed, Localitá Camerelle, Pozzilli (IS), Italy
| | - Giuseppe Pepe
- IRCCS Neuromed, Localitá Camerelle, Pozzilli (IS), Italy
| | | | - Luca Capocci
- IRCCS Neuromed, Localitá Camerelle, Pozzilli (IS), Italy
| | | | | | | | - Fabio Buttari
- IRCCS Neuromed, Localitá Camerelle, Pozzilli (IS), Italy
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9
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Jamwal S, Kumar P. Insight Into the Emerging Role of Striatal Neurotransmitters in the Pathophysiology of Parkinson's Disease and Huntington's Disease: A Review. Curr Neuropharmacol 2019; 17:165-175. [PMID: 29512464 PMCID: PMC6343208 DOI: 10.2174/1570159x16666180302115032] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 11/06/2017] [Accepted: 02/28/2018] [Indexed: 12/05/2022] Open
Abstract
Alteration in neurotransmitters signaling in basal ganglia has been consistently shown to significantly contribute to the pathophysiological basis of Parkinson's disease and Huntington's disease. Dopamine is an important neurotransmitter which plays a critical role in coordinated body movements. Alteration in the level of brain dopamine and receptor radically contributes to irregular movements, glutamate mediated excitotoxic neuronal death and further leads to imbalance in the levels of other neurotransmitters viz. GABA, adenosine, acetylcholine and endocannabinoids. This review is based upon the data from clinical and preclinical studies to characterize the role of various striatal neurotransmitters in the pathogenesis of Parkinson's disease and Huntington's disease. Further, we have collected data of altered level of various neurotransmitters and their metabolites and receptor density in basal ganglia region. Although the exact mechanisms underlying neuropathology of movement disorders are not fully understood, but several mechanisms related to neurotransmitters alteration, excitotoxic neuronal death, oxidative stress, mitochondrial dysfunction, neuroinflammation are being put forward. Restoring neurotransmitters level and downstream signaling has been considered to be beneficial in the treatment of Parkinson's disease and Huntington's disease. Therefore, there is an urgent need to identify more specific drugs and drug targets that can restore the altered neurotransmitters level in brain and prevent/delay neurodegeneration.
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Affiliation(s)
| | - Puneet Kumar
- Address correspondence to this author at the Department of Pharmaceutical Sciences and Technology, Maharaja Ranjit Singh Punjab Technical University, Bathinda, Panjab, India; E-mail:
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10
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Di Pardo A, Maglione V. Sphingolipid Metabolism: A New Therapeutic Opportunity for Brain Degenerative Disorders. Front Neurosci 2018; 12:249. [PMID: 29719499 PMCID: PMC5913346 DOI: 10.3389/fnins.2018.00249] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Accepted: 03/29/2018] [Indexed: 01/01/2023] Open
Abstract
Neurodegenerative diseases represent a class of fatal brain disorders for which the number of effective therapeutic options remains limited with only symptomatic treatment accessible. Multiple studies show that defects in sphingolipid pathways are shared among different brain disorders including neurodegenerative diseases and may contribute to their complex pathogenesis. In this mini review, we discuss the hypothesis that modulation of sphingolipid metabolism and their related signaling pathways may represent a potential therapeutic approach for those devastating conditions. The plausible “druggability” of sphingolipid pathways is greatly promising and represent a relevant feature that brings real advantage to the development of new therapeutic options for these conditions. Indeed, several molecules that selectively target sphingolipds are already available and many of them currently in clinical trial for human diseases. A deeper understanding of the “sphingolipid scenario” in neurodegenerative disorders would certainly enhance therapeutic perspectives for these conditions, by taking advantage from the already available molecules and by promoting the development of new ones.
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11
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Di Pardo A, Basit A, Armirotti A, Amico E, Castaldo S, Pepe G, Marracino F, Buttari F, Digilio AF, Maglione V. De novo Synthesis of Sphingolipids Is Defective in Experimental Models of Huntington's Disease. Front Neurosci 2017; 11:698. [PMID: 29311779 PMCID: PMC5742211 DOI: 10.3389/fnins.2017.00698] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 11/27/2017] [Indexed: 11/23/2022] Open
Abstract
Alterations of lipid metabolism have been frequently associated with Huntington's disease (HD) over the past years. HD is the most common neurodegenerative disorder, with a complex pathogenic profile, typically characterized by progressive striatal and cortical degeneration and associated motor, cognitive and behavioral disturbances. Previous findings from our group support the idea that disturbed sphingolipid metabolism could represent an additional hallmark of the disease. Although such a defect represents a common biological denominator among multiple disease models ranging from cells to humans through mouse models, more efforts are needed to clearly define its clinical significance and the role it may play in the progression of the disease. In this study, we provided the first evidence of a defective de novo biosynthetic pathway of sphingolipids in multiple HD pre-clinical models. qPCR analysis revealed perturbed gene expression of sphingolipid-metabolizing enzymes in both early and late stage of the disease. In particular, reduction in the levels of sptlc1 and cerS1 mRNA in the brain tissues from manifest HD mice resulted in a significant decrease in the content of dihydroSphingosine, dihydroSphingosine-1-phospahte and dihydroCeramide [C18:0] as assessed by mass spectrometry. Moreover, in vitro studies highlighted the relevant role that aberrant sphingolipid metabolism may have in the HD cellular homeostasis. With this study, we consolidate the evidence of disturbed sphingolipid metabolism in HD and demonstrate for the first time that the de novo biosynthesis pathway is also significantly affected in the disease. This finding further supports the hypothesis that perturbed sphingolipid metabolism may represent a crucial factor accounting for the high susceptibility to disease in HD.
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Affiliation(s)
| | - Abdul Basit
- Department of Drug Discovery and Development, Fondazione Istituto Italiano di Tecnologia, Genova, Italy
| | - Andrea Armirotti
- Department of Drug Discovery and Development, Fondazione Istituto Italiano di Tecnologia, Genova, Italy
| | | | | | | | | | | | - Anna F Digilio
- Institute of Biosciences and Bioresources, National Research Council, Naples, Italy
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12
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Park M, Min B, Jeon K, Cho S, Park JS, Kim J, Jeon J, Song J, Kim S, Jeong S, Seo H, Kang YK. Age-associated chromatin relaxation is enhanced in Huntington's disease mice. Aging (Albany NY) 2017; 9:803-822. [PMID: 28288000 PMCID: PMC5391233 DOI: 10.18632/aging.101193] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 02/26/2017] [Indexed: 12/13/2022]
Abstract
Expansion of polyglutamine stretch in the huntingtin (HTT) protein is a major cause of Huntington's disease (HD). The polyglutamine part in HTT interacts with various proteins implicated in epigenetic regulation of genes, suggesting that mutant HTT may disturb the integrity of the epigenetic system. Here, we used a PCRseq-based method to examine expression profile of 395 exonic segments from 260 “epi-driver” genes in splenic T lymphocytes from aged HD mice. We identified 67 exonic segments differentially expressed between young and aged HD mice, most of them upregulated in the aged. Polycomb-repressive complex (PRC)-regulated genes (PRGs) were markedly upregulated in aged HD mice, consistent with downregulation of PRC genes. Epi-driver gene categories of lysine-methylation, lysine-demethylation, arginine-methylation, and PRG showed differential age-associated changes between HD and control. Analyzing the pattern of change in epi-driver gene expressions hinted at an enhanced shift in HD chromatin to a more accessible state with age, which was experimentally demonstrated by DNase-I-hypersensitivity sequencing showing increased chromatin accessibility in HD cells compared to control. We suggest the global change can potentially relieve chromatin-induced repression of many genes, and the unintended expressions of some detrimental proteins could alter T cell function to a greater degree in aged HD mice.
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Affiliation(s)
- Myungsun Park
- Development and Differentiation Research Center, KRIBB, Yuseong-gu, Daejeon, 305-806, South Korea
| | - Byungkuk Min
- Development and Differentiation Research Center, KRIBB, Yuseong-gu, Daejeon, 305-806, South Korea
| | - Kyuheum Jeon
- Development and Differentiation Research Center, KRIBB, Yuseong-gu, Daejeon, 305-806, South Korea.,Department of Functional Genomics, University of Science and Technology (UST), Yuseong-gu, Daejeon, 305-350, South Korea
| | - Sunwha Cho
- Development and Differentiation Research Center, KRIBB, Yuseong-gu, Daejeon, 305-806, South Korea
| | - Jung Sun Park
- Development and Differentiation Research Center, KRIBB, Yuseong-gu, Daejeon, 305-806, South Korea.,Aging Research Institute, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 305-806, South Korea
| | - Jisun Kim
- Department of Molecular and Life Sciences, Hanyang University, Sangnok-gu, Ansan, Gyeonggi-do, 15588, South Korea
| | - Jeha Jeon
- Department of Molecular and Life Sciences, Hanyang University, Sangnok-gu, Ansan, Gyeonggi-do, 15588, South Korea
| | - Jinhoi Song
- Aging Research Institute, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 305-806, South Korea
| | - Seokho Kim
- Aging Research Institute, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 305-806, South Korea
| | - Sangkyun Jeong
- Mibyeong Research Center, Korea Institute of Oriental Medicine (KIOM), Yuseong-gu, Daejeon, 305-811, South Korea
| | - Hyemyung Seo
- Department of Molecular and Life Sciences, Hanyang University, Sangnok-gu, Ansan, Gyeonggi-do, 15588, South Korea
| | - Yong-Kook Kang
- Development and Differentiation Research Center, KRIBB, Yuseong-gu, Daejeon, 305-806, South Korea.,Aging Research Institute, Korea Research Institute of Bioscience and Biotechnology, Daejeon, 305-806, South Korea.,Department of Functional Genomics, University of Science and Technology (UST), Yuseong-gu, Daejeon, 305-350, South Korea
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13
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Kuiper EFE, de Mattos EP, Jardim LB, Kampinga HH, Bergink S. Chaperones in Polyglutamine Aggregation: Beyond the Q-Stretch. Front Neurosci 2017; 11:145. [PMID: 28386214 PMCID: PMC5362620 DOI: 10.3389/fnins.2017.00145] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Accepted: 03/08/2017] [Indexed: 01/12/2023] Open
Abstract
Expanded polyglutamine (polyQ) stretches in at least nine unrelated proteins lead to inherited neuronal dysfunction and degeneration. The expansion size in all diseases correlates with age at onset (AO) of disease and with polyQ protein aggregation, indicating that the expanded polyQ stretch is the main driving force for the disease onset. Interestingly, there is marked interpatient variability in expansion thresholds for a given disease. Between different polyQ diseases the repeat length vs. AO also indicates the existence of modulatory effects on aggregation of the upstream and downstream amino acid sequences flanking the Q expansion. This can be either due to intrinsic modulation of aggregation by the flanking regions, or due to differential interaction with other proteins, such as the components of the cellular protein quality control network. Indeed, several lines of evidence suggest that molecular chaperones have impact on the handling of different polyQ proteins. Here, we review factors differentially influencing polyQ aggregation: the Q-stretch itself, modulatory flanking sequences, interaction partners, cleavage of polyQ-containing proteins, and post-translational modifications, with a special focus on the role of molecular chaperones. By discussing typical examples of how these factors influence aggregation, we provide more insight on the variability of AO between different diseases as well as within the same polyQ disorder, on the molecular level.
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Affiliation(s)
- E F E Kuiper
- Department of Cell Biology, University Medical Center Groningen, University of Groningen Groningen, Netherlands
| | - Eduardo P de Mattos
- Department of Cell Biology, University Medical Center Groningen, University of GroningenGroningen, Netherlands; Programa de Pós-Graduação em Genética e Biologia Molecular, Department of Genetics, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil; Medical Genetics Service, Hospital de Clínicas de Porto AlegrePorto Alegre, Brazil
| | - Laura B Jardim
- Programa de Pós-Graduação em Genética e Biologia Molecular, Department of Genetics, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil; Medical Genetics Service, Hospital de Clínicas de Porto AlegrePorto Alegre, Brazil; Departamento de Medicina Interna, Universidade Federal do Rio Grande do SulPorto Alegre, Brazil
| | - Harm H Kampinga
- Department of Cell Biology, University Medical Center Groningen, University of Groningen Groningen, Netherlands
| | - Steven Bergink
- Department of Cell Biology, University Medical Center Groningen, University of Groningen Groningen, Netherlands
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Wong BKY, Ehrnhoefer DE, Graham RK, Martin DDO, Ladha S, Uribe V, Stanek LM, Franciosi S, Qiu X, Deng Y, Kovalik V, Zhang W, Pouladi MA, Shihabuddin LS, Hayden MR. Partial rescue of some features of Huntington Disease in the genetic absence of caspase-6 in YAC128 mice. Neurobiol Dis 2015; 76:24-36. [PMID: 25583186 DOI: 10.1016/j.nbd.2014.12.030] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 12/22/2014] [Accepted: 12/31/2014] [Indexed: 12/13/2022] Open
Abstract
Huntington Disease (HD) is a progressive neurodegenerative disease caused by an elongated CAG repeat in the huntingtin (HTT) gene that encodes a polyglutamine tract in the HTT protein. Proteolysis of the mutant HTT protein (mHTT) has been detected in human and murine HD brains and is implicated in the pathogenesis of HD. Of particular importance is the site at amino acid (aa) 586 that contains a caspase-6 (Casp6) recognition motif. Activation of Casp6 occurs presymptomatically in human HD patients and the inhibition of mHTT proteolysis at aa586 in the YAC128 mouse model results in the full rescue of HD-like phenotypes. Surprisingly, Casp6 ablation in two different HD mouse models did not completely prevent the generation of this fragment, and therapeutic benefits were limited, questioning the role of Casp6 in the disease. We have evaluated the impact of the loss of Casp6 in the YAC128 mouse model of HD. Levels of the mHTT-586 fragment are reduced but not absent in the absence of Casp6 and we identify caspase 8 as an alternate enzyme that can generate this fragment. In vivo, the ablation of Casp6 results in a partial rescue of body weight gain, normalized IGF-1 levels, a reversal of the depression-like phenotype and decreased HTT levels. In the YAC128/Casp6-/- striatum there is a concomitant reduction in p62 levels, a marker of autophagic activity, suggesting increased autophagic clearance. These results implicate the HTT-586 fragment as a key contributor to certain features of HD, irrespective of the enzyme involved in its generation.
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Affiliation(s)
- Bibiana K Y Wong
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada; Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Dagmar E Ehrnhoefer
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Rona K Graham
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada; Research Center on Aging, Department of Physiology and Biophysics, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Dale D O Martin
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Safia Ladha
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Valeria Uribe
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Lisa M Stanek
- Genzyme, a Sanofi Company, Framingham, MA 01701, USA
| | - Sonia Franciosi
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Xiaofan Qiu
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Yu Deng
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Vlad Kovalik
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Weining Zhang
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - Mahmoud A Pouladi
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada; Translational Laboratory in Genetic Medicine, Agency for Science, Technology and Research, 138648, Singapore; Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, 138648, Singapore
| | | | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada.
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15
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An in vitro perspective on the molecular mechanisms underlying mutant huntingtin protein toxicity. Cell Death Dis 2012; 3:e382. [PMID: 22932724 PMCID: PMC3434668 DOI: 10.1038/cddis.2012.121] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Huntington's disease (HD) is a devastating neurodegenerative disorder whose main hallmark is brain atrophy. However, several peripheral organs are considerably affected and their symptoms may, in fact, manifest before those resulting from brain pathology. HD is of genetic origin and caused by a mutation in the huntingtin gene. The mutated protein has detrimental effects on cell survival, but whether the mutation leads to a gain of toxic function or a loss of function of the altered protein is still highly controversial. Most currently used in vitro models have been designed, to a large extent, to investigate the effects of the aggregation process in neuronal-like cells. However, as the pathology involves several other organs, new in vitro models are critically needed to take into account the deleterious effects of mutant huntingtin in peripheral tissues, and thus to identify new targets that could lead to more effective clinical interventions in the early course of the disease. This review aims to present current in vitro models of HD pathology and to discuss the knowledge that has been gained from these studies as well as the new in vitro tools that have been developed, which should reflect the more global view that we now have of the disease.
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16
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Jin YN, Hwang WY, Jo C, Johnson GVW. Metabolic state determines sensitivity to cellular stress in Huntington disease: normalization by activation of PPARγ. PLoS One 2012; 7:e30406. [PMID: 22276192 PMCID: PMC3262812 DOI: 10.1371/journal.pone.0030406] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 12/15/2011] [Indexed: 11/17/2022] Open
Abstract
Impairments in mitochondria and transcription are important factors in the pathogenesis of Huntington disease (HD), a neurodegenerative disease caused by a polyglutamine expansion in the huntingtin protein. This study investigated the effect of different metabolic states and peroxisome proliferator-activated receptor γ (PPARγ) activation on sensitivity to cellular stressors such as H(2)O(2) or thapsigargin in HD. Striatal precursor cells expressing wild type (STHdh(Q7)) or mutant huntingtin (STHdh(Q111)) were prepared in different metabolic conditions (glucose vs. pyruvate). Due to the fact that STHdh(Q111) cells exhibit mitochondrial deficits, we expected that in the pyruvate condition, where ATP is generated primarily by the mitochondria, there would be greater differences in cell death between the two cell types compared to the glucose condition. Intriguingly, it was the glucose condition that gave rise to greater differences in cell death. In the glucose condition, thapsigargin treatment resulted in a more rapid loss of mitochondrial membrane potential (ΔΨm), a greater activation of caspases (3, 8, and 9), and a significant increase in superoxide/reactive oxygen species (ROS) in STHdh(Q111) compared to STHdh(Q7), while both cell types showed similar kinetics of ΔΨm-loss and similar levels of superoxide/ROS in the pyruvate condition. This suggests that bioenergetic deficiencies are not the primary contributor to the enhanced sensitivity of STHdh(Q111) cells to stressors compared to the STHdh(Q7) cells. PPARγ activation significantly attenuated thapsigargin-induced cell death, concomitant with an inhibition of caspase activation, a delay in ΔΨm loss, and a reduction of superoxide/ROS generation in STHdh(Q111) cells. Expression of mutant huntingtin in primary neurons induced superoxide/ROS, an effect that was significantly reduced by constitutively active PPARγ. These results provide significant insight into the bioenergetic disturbances in HD with PPARγ being a potential therapeutic target for HD.
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Affiliation(s)
- Youngnam N Jin
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, United States of America
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17
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Squitieri F, Maglione V, Orobello S, Fornai F. Genotype-, aging-dependent abnormal caspase activity in Huntington disease blood cells. J Neural Transm (Vienna) 2011; 118:1599-607. [PMID: 21519949 DOI: 10.1007/s00702-011-0646-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 04/08/2011] [Indexed: 11/30/2022]
Abstract
Huntington's Disease (HD) is caused by trinucleotide CAG repeat expansion >36 in huntingtin (htt), a protein with several documented functions. The elongated polyglutamine (polyQ) stretch in the N-terminal region of htt leads to dysfunctional and degenerative events in neurons and peripheral tissues. In this study, by extending the analysis to several caspase activities (i.e. caspase 2, 3, 6, 8 and 9), we describe genotype- and time- dependent caspase activity abnormalities, decreased cell viability and a large set of alterations in mitochondria morphology, in cultured blood cells from HD patients. Patients homozygous for CAG repeat mutations and heterozygous with high size mutations causing juvenile onset (JHD) presented significantly increased caspase 2, 3, 6, 8 and 9 activities, decreased cell viability and pronounced morphological abnormalities, compared with cells carrying low mutation size and controls. After cyanide treatment, all caspases increased their activities in homozygous and highly expanded heterozygous cells, caspase 8 and 9 increased also in those cells carrying low-size mutations, remarking their key role as 'caspase initiators' in HD. The remarkable ageing-dependent abnormalities in peripheral cells carrying particularly toxic mutations (i.e. homozygotes' and JHD's blood cells) points out the potential dependence of clinical HD development and progression on either mutated htt dosage or missing wild type htt. Peripheral tissues (i.e. blood cells) may theoretically represent an important tool for studying HD mechanisms and searching for new biomarkers, according to the patients' genotype.
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Affiliation(s)
- Ferdinando Squitieri
- Neurogenetics Unit and Rare Diseases Centre, IRCCS Neuromed, Pozzilli (IS), Italy.
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18
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Abstract
It has been more than 17 years since the causative mutation for Huntington's disease was discovered as the expansion of the triplet repeat in the N-terminal portion of the Huntingtin (HTT) gene. In the intervening time, researchers have discovered a great deal about Huntingtin's involvement in a number of cellular processes. However, the role of Huntingtin in the key pathogenic mechanism leading to neurodegeneration in the disease process has yet to be discovered. Here, we review the body of knowledge that has been uncovered since gene discovery and include discussions of the HTT gene, CAG triplet repeat expansion, HTT expression, protein features, posttranslational modifications, and many of its known protein functions and interactions. We also highlight potential pathogenic mechanisms that have come to light in recent years.
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Affiliation(s)
- Karen N McFarland
- Department of Neurology, University of Florida, Gainesville, FL 32610-0236, USA.
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19
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Kumar P, Kalonia H, Kumar A. Huntington's disease: pathogenesis to animal models. Pharmacol Rep 2010; 62:1-14. [PMID: 20360611 DOI: 10.1016/s1734-1140(10)70238-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 02/02/2010] [Indexed: 01/17/2023]
Abstract
Huntington's disease (HD) is an inherited genetic disorder, characterized by cognitive dysfunction and abnormal body movements called chorea. George Huntington, an Ohio physician, described the disease precisely in 1872. HD is a dominantly inherited disorder, characterized by progressive neurodegeneration of the striatum but also involves other regions, primarily the cerebral cortex. The mutation responsible for this fatal disease is an abnormally expanded and unstable CAG repeat within the coding region of the gene encoding the huntingtin protein. Various hypotheses have been put forward to explain the pathogenic mechanisms of mutant huntingtin-induced neuronal dysfunction and cell death. None of these hypotheses, however, offers a clear explanation; thus, it remains a topic of research interest. HD is considered to be an important disease, embodying many of the major themes in modern neuroscience, including molecular genetics, selective neuronal vulnerability, excitotoxicity, mitochondrial dysfunction, apoptosis and transcriptional dysregulation. A number of recent reports have concluded that oxidative stress plays a key role in HD pathogenesis. Although there is no specific treatment available to block disease progression, treatments are available to help in controlling the chorea symptoms. As animal models are the best tools to evaluate any therapeutic agent, there are also different animal models available, mimicking a few or a larger number of symptoms. Each model has its own advantages and limitations. The present review deals with the pathophysiology and various cascades contributing to HD pathogenesis and progression as well as drug targets, such as dopaminergic, gamma-amino butyric acid (GABA)ergic, glutamate adenosine receptor, peptidergic pathways, cannabinoid receptor, and adjuvant therapeutic drug targets such as oxidative stress and mitochondrial dysfunction that can be targeted for future experimental study. The present review also focuses on the animal models (behavioral and genetic) used to unravel pathogenetic mechanisms and the identification of novel drug targets.
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Affiliation(s)
- Puneet Kumar
- Pharmacology Division, University Institute of Pharmaceutical Sciences, UGC Centre of Advanced Study, Panjab University, Chandigarh-160014, India
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20
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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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21
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van der Burg JMM, Björkqvist M, Brundin P. Beyond the brain: widespread pathology in Huntington's disease. Lancet Neurol 2009; 8:765-74. [DOI: 10.1016/s1474-4422(09)70178-4] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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22
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Sassone J, Colciago C, Cislaghi G, Silani V, Ciammola A. Huntington's disease: the current state of research with peripheral tissues. Exp Neurol 2009; 219:385-97. [PMID: 19460373 DOI: 10.1016/j.expneurol.2009.05.012] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 04/30/2009] [Accepted: 05/09/2009] [Indexed: 01/23/2023]
Abstract
Huntington's disease (HD) is a genetically dominant condition caused by expanded CAG repeats. These repeats code for a glutamine tract in the HD gene product huntingtin (htt), which is a protein expressed in almost all tissues. Although most HD symptoms reflect preferential neuronal death in specific brain regions, even before the HD gene was identified numerous reports had described additional abnormalities in the peripheral tissues of HD patients, including weight loss, altered glucose homeostasis, and sub-cellular abnormalities in fibroblasts, lymphocytes and erythrocytes. Several years have elapsed since the HD mutation was discovered, and analyses of peripheral tissues from HD patients have helped to understand the molecular pathogenesis of the disease and revealed that the molecular mechanisms through which mutated htt leads to cell dysfunction are widely shared between central nervous system (CNS) and peripheral tissues. These studies show that in peripheral tissues, mutated htt causes accumulation of intracellular protein aggregates, impairment of energetic metabolism, transcriptional deregulation and hyperactivation of programmed cell-death mechanisms. Here, we review the current knowledge of peripheral tissue alterations in HD patients and in animal models of HD and focus on how this information can be used to identify potential therapeutic possibilities and biomarkers for disease progression.
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Affiliation(s)
- Jenny Sassone
- Department of Neurology and Laboratory of Neuroscience, Dino Ferrari Center, IRCCS Istituto Auxologico Italiano, University of Milan Medical School, via Spagnoletto 3, 20149, Milan, Italy
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23
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Chipping away at diagnostics for neurodegenerative diseases. Neurobiol Dis 2009; 35:148-56. [PMID: 19285134 DOI: 10.1016/j.nbd.2009.02.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Revised: 02/16/2009] [Accepted: 02/19/2009] [Indexed: 12/15/2022] Open
Abstract
Biomarkers are needed to overcome critical roadblocks in the development of disease-modifying therapeutics for neurodegenerative diseases. Evolving genome-wide expression technologies can comprehensively search for molecular biomarkers and allow fascinating insights into the expanding complexity of the human transcriptome. The technology has matured to the point where some applications are deemed reliable enough for use in patient care. In the neurosciences, it has led to the discoveries of osteopontin in multiple sclerosis and SORL1/LR11 in Alzheimer's, and recent studies indicate its potential for identifying neurogenomic biomarkers. Advances in pre-analytical and analytical methods are improving search efficiency and reproducibility and may lead to a pipeline of biomarker candidates suitable for development into future neurologic diagnostics.
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Luo S, Rubinsztein DC. Huntingtin promotes cell survival by preventing Pak2 cleavage. J Cell Sci 2009; 122:875-85. [PMID: 19240112 DOI: 10.1242/jcs.050013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Huntington's disease is caused by a polyglutamine expansion in the huntingtin protein. Wild-type huntingtin, by contrast, appears to protect cells from pro-apoptotic insults. Here we describe a novel anti-apoptotic function for huntingtin. When cells are exposed to Fas-related signals, the ubiquitously expressed p21-activated kinase 2 (Pak2) can be activated via cleavage by caspases to release a constitutively active C-terminal fragment, which mediates cell death. Our data show that huntingtin interacts with Pak2. Overexpression of huntingtin significantly inhibits caspase-3-mediated and caspase-8-mediated cleavage of Pak2 in cells. Moreover, huntingtin prevents Pak2 cleavage by caspase-3 and caspase-8 in vitro. Although huntingtin is cytoprotective in wild-type cells that are exposed to TNFalpha, it has no significant benefit in TNFalpha-treated cells with Pak2 knockdown. Thus, huntingtin exerts anti-apoptotic effects by binding to Pak2, which reduces the abilities of caspase-3 and caspase-8 to cleave Pak2 and convert it into a mediator of cell death.
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Affiliation(s)
- Shouqing Luo
- Department of Medical Genetics, Cambridge Institute for Medical Research, Wellcome/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0XY, UK
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25
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Abstract
Huntington's disease (HD) is a devastating autosomal dominant neurodegenerative disease caused by a CAG trinucleotide repeat expansion encoding an abnormally long polyglutamine tract in the huntingtin protein. Much has been learnt since the mutation was identified in 1993. We review the functions of wild-type huntingtin. Mutant huntingtin may cause toxicity via a range of different mechanisms. The primary consequence of the mutation is to confer a toxic gain of function on the mutant protein and this may be modified by certain normal activities that are impaired by the mutation. It is likely that the toxicity of mutant huntingtin is revealed after a series of cleavage events leading to the production of N-terminal huntingtin fragment(s) containing the expanded polyglutamine tract. Although aggregation of the mutant protein is a hallmark of the disease, the role of aggregation is complex and the arguments for protective roles of inclusions are discussed. Mutant huntingtin may mediate some of its toxicity in the nucleus by perturbing specific transcriptional pathways. HD may also inhibit mitochondrial function and proteasome activity. Importantly, not all of the effects of mutant huntingtin may be cell-autonomous, and it is possible that abnormalities in neighbouring neurons and glia may also have an impact on connected cells. It is likely that there is still much to learn about mutant huntingtin toxicity, and important insights have already come and may still come from chemical and genetic screens. Importantly, basic biological studies in HD have led to numerous potential therapeutic strategies.
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26
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Mormone E, Matarrese P, Tinari A, Cannella M, Maglione V, Farrace MG, Piacentini M, Frati L, Malorni W, Squitieri F. Genotype-dependent priming to self- and xeno-cannibalism in heterozygous and homozygous lymphoblasts from patients with Huntington's disease. J Neurochem 2006; 98:1090-9. [PMID: 16895579 DOI: 10.1111/j.1471-4159.2006.03998.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the present work, we studied the mitochondrial function and cell death pathway(s) in heterozygous and homozygous immortalized cell lines from patients with Huntington's disease (HD). Heterozygosis was characterized by specific alterations in mitochondrial membrane potential, a constitutive hyperpolarization state of mitochondria, and was correlated with an increased susceptibility to apoptosis. Lymphoblasts from homozygous patients, on the other hand, were characterized by a significant percentage of cells displaying autophagic vacuoles. These cells also demonstrated a striking attitude towards significant cannibalistic activity. Considering the pathogenic role of cell death in HD, our study provides new and useful insights into the role of mitochondrial dysfunction, i.e. hyperpolarization, in hijacking HD heterozygous cells towards apoptosis and HD homozygous cells towards a peculiar phenotype characterized by both self- and xeno-cannibalism. These events can, however, be viewed as an ultimate attempt to survive rather than a way to die. The present work underlines the possibility that HD-associated mitochondrial defects could tentatively be by-passed by the cells by activating cellular 'phagic' activities, including so-called 'mitophagy' and 'cannibalism', that only finally lead to cell death.
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Affiliation(s)
- Elisabetta Mormone
- Department of Drug Research and Evaluation, Istituto Superiore di Sanità, Rome, Italy
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