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Gao R, Chakraborty A, Geater C, Pradhan S, Gordon KL, Snowden J, Yuan S, Dickey AS, Choudhary S, Ashizawa T, Ellerby LM, La Spada AR, Thompson LM, Hazra TK, Sarkar PS. Mutant huntingtin impairs PNKP and ATXN3, disrupting DNA repair and transcription. eLife 2019; 8:42988. [PMID: 30994454 PMCID: PMC6529219 DOI: 10.7554/elife.42988] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 04/16/2019] [Indexed: 11/13/2022] Open
Abstract
How huntingtin (HTT) triggers neurotoxicity in Huntington's disease (HD) remains unclear. We report that HTT forms a transcription-coupled DNA repair (TCR) complex with RNA polymerase II subunit A (POLR2A), ataxin-3, the DNA repair enzyme polynucleotide-kinase-3'-phosphatase (PNKP), and cyclic AMP-response element-binding (CREB) protein (CBP). This complex senses and facilitates DNA damage repair during transcriptional elongation, but its functional integrity is impaired by mutant HTT. Abrogated PNKP activity results in persistent DNA break accumulation, preferentially in actively transcribed genes, and aberrant activation of DNA damage-response ataxia telangiectasia-mutated (ATM) signaling in HD transgenic mouse and cell models. A concomitant decrease in Ataxin-3 activity facilitates CBP ubiquitination and degradation, adversely impacting transcription and DNA repair. Increasing PNKP activity in mutant cells improves genome integrity and cell survival. These findings suggest a potential molecular mechanism of how mutant HTT activates DNA damage-response pro-degenerative pathways and impairs transcription, triggering neurotoxicity and functional decline in HD.
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Affiliation(s)
- Rui Gao
- Department of Neurology, University of Texas Medical Branch, Galveston, United States
| | - Anirban Chakraborty
- Department of Internal Medicine, University of Texas Medical Branch, Galveston, United States
| | - Charlene Geater
- Department of Psychiatry and Human Behavior and the Sue and Bill Gross Stem Cell Center, University of California, Irvine, Irvine, United States
| | - Subrata Pradhan
- Department of Neurology, University of Texas Medical Branch, Galveston, United States
| | - Kara L Gordon
- Department of Neurology, Duke University School of Medicine, Durham, United States
| | - Jeffrey Snowden
- Department of Neurology, University of Texas Medical Branch, Galveston, United States
| | - Subo Yuan
- Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, United States
| | - Audrey S Dickey
- Department of Neurology, Duke University School of Medicine, Durham, United States
| | - Sanjeev Choudhary
- Department of Biochemistry, Cell Biology and Genetics, Sam Houston State University, Huntsville, United States
| | - Tetsuo Ashizawa
- Department of Neurology, Houston Methodist Research Institute, Houston, United States
| | - Lisa M Ellerby
- Buck Institute for Research on Aging, Novato, United States
| | - Albert R La Spada
- Department of Neurology, Duke University School of Medicine, Durham, United States
| | - Leslie M Thompson
- Department of Psychiatry and Human Behavior and the Sue and Bill Gross Stem Cell Center, University of California, Irvine, Irvine, United States.,Department of Neurobiology and Behavior, University of California, Irvine, Institute for Memory Impairments and Neurological Disorders, Irvine, United States
| | - Tapas K Hazra
- Department of Internal Medicine, University of Texas Medical Branch, Galveston, United States
| | - Partha S Sarkar
- Department of Neurology, University of Texas Medical Branch, Galveston, United States.,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, United States
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Dickey AS, Sanchez DN, Arreola M, Sampat KR, Fan W, Arbez N, Akimov S, Van Kanegan MJ, Ohnishi K, Gilmore-Hall SK, Flores AL, Nguyen JM, Lomas N, Hsu CL, Lo DC, Ross CA, Masliah E, Evans RM, La Spada AR. PPARδ activation by bexarotene promotes neuroprotection by restoring bioenergetic and quality control homeostasis. Sci Transl Med 2018; 9:9/419/eaal2332. [PMID: 29212711 DOI: 10.1126/scitranslmed.aal2332] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Accepted: 08/09/2017] [Indexed: 01/02/2023]
Abstract
Neurons must maintain protein and mitochondrial quality control for optimal function, an energetically expensive process. The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that promote mitochondrial biogenesis and oxidative metabolism. We recently determined that transcriptional dysregulation of PPARδ contributes to Huntington's disease (HD), a progressive neurodegenerative disorder resulting from a CAG-polyglutamine repeat expansion in the huntingtin gene. We documented that the PPARδ agonist KD3010 is an effective therapy for HD in a mouse model. PPARδ forms a heterodimer with the retinoid X receptor (RXR), and RXR agonists are capable of promoting PPARδ activation. One compound with potent RXR agonist activity is the U.S. Food and Drug Administration-approved drug bexarotene. We tested the therapeutic potential of bexarotene in HD and found that bexarotene was neuroprotective in cellular models of HD, including medium spiny-like neurons generated from induced pluripotent stem cells (iPSCs) derived from patients with HD. To evaluate bexarotene as a treatment for HD, we treated the N171-82Q mouse model with the drug and found that bexarotene improved motor function, reduced neurodegeneration, and increased survival. To determine the basis for PPARδ neuroprotection, we evaluated metabolic function and noted markedly impaired oxidative metabolism in HD neurons, which was rescued by bexarotene or KD3010. We examined mitochondrial and protein quality control in cellular models of HD and observed that treatment with a PPARδ agonist promoted cellular quality control. By boosting cellular activities that are dysfunctional in HD, PPARδ activation may have therapeutic applications in HD and potentially other neurodegenerative diseases.
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Affiliation(s)
- Audrey S Dickey
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Dafne N Sanchez
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Martin Arreola
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Kunal R Sampat
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Weiwei Fan
- Gene Expression Laboratory, Salk Institute for Biological Studies, San Diego, CA 92037, USA
| | - Nicolas Arbez
- Departments of Psychiatry, Neurology, and Pharmacology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Sergey Akimov
- Departments of Psychiatry, Neurology, and Pharmacology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Michael J Van Kanegan
- Center for Drug Discovery and Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Kohta Ohnishi
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | | | - April L Flores
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Janice M Nguyen
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nicole Lomas
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Cynthia L Hsu
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Donald C Lo
- Center for Drug Discovery and Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Christopher A Ross
- Departments of Psychiatry, Neurology, and Pharmacology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Eliezer Masliah
- Department of Pathology, University of California, San Diego, La Jolla, CA 92093, USA.,Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ronald M Evans
- Gene Expression Laboratory, Salk Institute for Biological Studies, San Diego, CA 92037, USA.,Howard Hughes Medical Institute, Salk Institute for Biological Studies, San Diego, CA 92037, USA
| | - Albert R La Spada
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA. .,Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA.,Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA.,Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.,Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA.,Sanford Consortium for Regenerative Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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Dickey AS, La Spada AR. Therapy development in Huntington disease: From current strategies to emerging opportunities. Am J Med Genet A 2017; 176:842-861. [PMID: 29218782 DOI: 10.1002/ajmg.a.38494] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 09/08/2017] [Indexed: 12/13/2022]
Abstract
Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder in which patients typically present with uncontrolled involuntary movements and subsequent cognitive decline. In 1993, a CAG trinucleotide repeat expansion in the coding region of the huntingtin (HTT) gene was identified as the cause of this disorder. This extended CAG repeat results in production of HTT protein with an expanded polyglutamine tract, leading to pathogenic HTT protein conformers that are resistant to protein turnover, culminating in cellular toxicity and neurodegeneration. Research into the mechanistic basis of HD has highlighted a role for bioenergetics abnormalities stemming from mitochondrial dysfunction, and for synaptic defects, including impaired neurotransmission and excitotoxicity. Interference with transcription regulation may underlie the mitochondrial dysfunction. Current therapies for HD are directed at treating symptoms, as there are no disease-modifying therapies. Commonly prescribed drugs for involuntary movement control include tetrabenazine, a potent and selective inhibitor of vesicular monoamine transporter 2 that depletes synaptic monoamines, and olanzapine, an atypical neuroleptic that blocks the dopamine D2 receptor. Various drugs are used to treat non-motor features. The HD therapeutic pipeline is robust, as numerous efforts are underway to identify disease-modifying treatments, with some small compounds and biological agents moving into clinical trials. Especially encouraging are dosage reduction strategies, including antisense oligonucleotides, and molecules directed at transcription dysregulation. Given the depth and breadth of current HD drug development efforts, there is reason to believe that disease-modifying therapies for HD will emerge, and this achievement will have profound implications for the entire neurotherapeutics field.
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Affiliation(s)
- Audrey S Dickey
- Departments of Neurology, Neurobiology, and Cell Biology, Duke Center for Neurodegeneration & Neurotherapeutics, Duke University Medical Center, Durham, North Carolina
| | - Albert R La Spada
- Departments of Neurology, Neurobiology, and Cell Biology, Duke Center for Neurodegeneration & Neurotherapeutics, Duke University Medical Center, Durham, North Carolina
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