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Skeens A, Siriwardhana C, Massinople SE, Wunder MM, Ellis ZL, Keith KM, Girman T, Frey SL, Legleiter J. The polyglutamine domain is the primary driver of seeding in huntingtin aggregation. PLoS One 2024; 19:e0298323. [PMID: 38483973 PMCID: PMC10939245 DOI: 10.1371/journal.pone.0298323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 01/22/2024] [Indexed: 03/17/2024] Open
Abstract
Huntington's Disease (HD) is a fatal, neurodegenerative disease caused by aggregation of the huntingtin protein (htt) with an expanded polyglutamine (polyQ) domain into amyloid fibrils. Htt aggregation is modified by flanking sequences surrounding the polyQ domain as well as the binding of htt to lipid membranes. Upon fibrillization, htt fibrils are able to template the aggregation of monomers into fibrils in a phenomenon known as seeding, and this process appears to play a critical role in cell-to-cell spread of HD. Here, exposure of C. elegans expressing a nonpathogenic N-terminal htt fragment (15-repeat glutamine residues) to preformed htt-exon1 fibrils induced inclusion formation and resulted in decreased viability in a dose dependent manner, demonstrating that seeding can induce toxic aggregation of nonpathogenic forms of htt. To better understand this seeding process, the impact of flanking sequences adjacent to the polyQ stretch, polyQ length, and the presence of model lipid membranes on htt seeding was investigated. Htt seeding readily occurred across polyQ lengths and was independent of flanking sequence, suggesting that the structured polyQ domain within fibrils is the key contributor to the seeding phenomenon. However, the addition of lipid vesicles modified seeding efficiency in a manner suggesting that seeding primarily occurs in bulk solution and not at the membrane interface. In addition, fibrils formed in the presence of lipid membranes displayed similar seeding efficiencies. Collectively, this suggests that the polyQ domain that forms the amyloid fibril core is the main driver of seeding in htt aggregation.
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Affiliation(s)
- Adam Skeens
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Chathuranga Siriwardhana
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Sophia E. Massinople
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Michelle M. Wunder
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Zachary L. Ellis
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Kaitlyn M. Keith
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Tyler Girman
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
| | - Shelli L. Frey
- The Department of Chemistry, Gettysburg College, Gettysburg, Pennsylvania, United States of America
| | - Justin Legleiter
- The C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, United States of America
- Rockefeller Neurosciences Institutes, West Virginia University, Morgantown, West Virginia, United States of America
- Department of Neuroscience, West Virginia University, Morgantown, West Virginia, United States of America
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Liu CF, Younes L, Tong XJ, Hinkle JT, Wang M, Phatak S, Xu X, Bu X, Looi V, Bang J, Tabrizi SJ, Scahill RI, Paulsen JS, Georgiou-Karistianis N, Faria AV, Miller MI, Ratnanather JT, Ross CA. Longitudinal imaging highlights preferential basal ganglia circuit atrophy in Huntington's disease. Brain Commun 2023; 5:fcad214. [PMID: 37744022 PMCID: PMC10516592 DOI: 10.1093/braincomms/fcad214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 05/09/2023] [Accepted: 08/17/2023] [Indexed: 09/26/2023] Open
Abstract
Huntington's disease is caused by a CAG repeat expansion in the Huntingtin gene (HTT), coding for polyglutamine in the Huntingtin protein, with longer CAG repeats causing earlier age of onset. The variable 'Age' × ('CAG'-L), where 'Age' is the current age of the individual, 'CAG' is the repeat length and L is a constant (reflecting an approximation of the threshold), termed the 'CAG Age Product' (CAP) enables the consideration of many individuals with different CAG repeat expansions at the same time for analysis of any variable and graphing using the CAG Age Product score as the X axis. Structural MRI studies have showed that progressive striatal atrophy begins many years prior to the onset of diagnosable motor Huntington's disease, confirmed by longitudinal multicentre studies on three continents, including PREDICT-HD, TRACK-HD and IMAGE-HD. However, previous studies have not clarified the relationship between striatal atrophy, atrophy of other basal ganglia structures, and atrophy of other brain regions. The present study has analysed all three longitudinal datasets together using a single image segmentation algorithm and combining data from a large number of subjects across a range of CAG Age Product score. In addition, we have used a strategy of normalizing regional atrophy to atrophy of the whole brain, in order to determine which regions may undergo preferential degeneration. This made possible the detailed characterization of regional brain atrophy in relation to CAG Age Product score. There is dramatic selective atrophy of regions involved in the basal ganglia circuit-caudate, putamen, nucleus accumbens, globus pallidus and substantia nigra. Most other regions of the brain appear to have slower but steady degeneration. These results support (but certainly do not prove) the hypothesis of circuit-based spread of pathology in Huntington's disease, possibly due to spread of mutant Htt protein, though other connection-based mechanisms are possible. Therapeutic targets related to prion-like spread of pathology or other mechanisms may be suggested. In addition, they have implications for current neurosurgical therapeutic approaches, since delivery of therapeutic agents solely to the caudate and putamen may miss other structures affected early, such as nucleus accumbens and output nuclei of the striatum, the substantia nigra and the globus pallidus.
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Affiliation(s)
- Chin-Fu Liu
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Laurent Younes
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Applied Mathematics and Statistics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Xiao J Tong
- Division of Neurobiology, Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore MD 21287, USA
| | - Jared T Hinkle
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
- Medical Scientist Training Program, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Maggie Wang
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Sanika Phatak
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Xin Xu
- Division of Magnetic Resonance, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Xuan Bu
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
- Huaxi MR Research Center, Department of Radiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Vivian Looi
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jee Bang
- Division of Neurobiology, Department of Psychiatry, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Sarah J Tabrizi
- HD Research Centre, University College London Queen Square Institute of Neurology, UCL, London, UK
| | - Rachael I Scahill
- HD Research Centre, University College London Queen Square Institute of Neurology, UCL, London, UK
| | - Jane S Paulsen
- Department of Neurology, University of Wisconsin, Madison, WI 53705, USA
| | - Nellie Georgiou-Karistianis
- School of Psychological Sciences and The Turner Institute for Brain and Mental Health, Monash University, Melbourne, Victoria 3800, Australia
| | - Andreia V Faria
- Division of Magnetic Resonance, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Michael I Miller
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - J Tilak Ratnanather
- Center for Imaging Science, Johns Hopkins University, Baltimore, MD 21218, USA
- Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Christopher A Ross
- Division of Neurobiology, Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore MD 21287, USA
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
- Division of Neurobiology, Department of Psychiatry, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Department of Pharmacology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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Donnelly KM, Coleman CM, Fuller ML, Reed VL, Smerina D, Tomlinson DS, Pearce MMP. Hunting for the cause: Evidence for prion-like mechanisms in Huntington’s disease. Front Neurosci 2022; 16:946822. [PMID: 36090278 PMCID: PMC9448931 DOI: 10.3389/fnins.2022.946822] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/28/2022] [Indexed: 11/23/2022] Open
Abstract
The hypothesis that pathogenic protein aggregates associated with neurodegenerative diseases spread from cell-to-cell in the brain in a manner akin to infectious prions has gained substantial momentum due to an explosion of research in the past 10–15 years. Here, we review current evidence supporting the existence of prion-like mechanisms in Huntington’s disease (HD), an autosomal dominant neurodegenerative disease caused by expansion of a CAG repeat tract in exon 1 of the huntingtin (HTT) gene. We summarize information gained from human studies and in vivo and in vitro models of HD that strongly support prion-like features of the mutant HTT (mHTT) protein, including potential involvement of molecular features of mHTT seeds, synaptic structures and connectivity, endocytic and exocytic mechanisms, tunneling nanotubes, and nonneuronal cells in mHTT propagation in the brain. We discuss mechanisms by which mHTT aggregate spreading and neurotoxicity could be causally linked and the potential benefits of targeting prion-like mechanisms in the search for new disease-modifying therapies for HD and other fatal neurodegenerative diseases.
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Affiliation(s)
- Kirby M. Donnelly
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - Cevannah M. Coleman
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - Madison L. Fuller
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - Victoria L. Reed
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - Dayna Smerina
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - David S. Tomlinson
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - Margaret M. Panning Pearce
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
- Department of Biology, Saint Joseph’s University, Philadelphia, PA, United States
- *Correspondence: Margaret M. Panning Pearce,
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Subramaniam S. Striatal Induction and Spread of the Huntington’s Disease Protein: A Novel Rhes Route. J Huntingtons Dis 2022; 11:281-290. [PMID: 35871361 PMCID: PMC9484121 DOI: 10.3233/jhd-220548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The CAG/CAA expansion encoding polyQ huntingtin (mutant huntingtin [mHTT]) causes Huntington’s disease (HD), which is characterized by atrophy and loss of striatal medium spiny neurons (MSNs), which are preceded by neuropathological alterations in the cortex. Previous studies have shown that mHTT can spread in the brain, but the mechanisms involved in the stereotyped degeneration and dysfunction of the neurons from the striatum to the cortex remain unclear. In this study, we found that the mHTT expression initially restricted in the striatum later spread to the cortical regions in mouse brains. Such transmission was diminished in mice that lacked the striatal-enriched protein Ras-homolog enriched in the striatum (Rhes). Rhes restricted to MSNs was also found in the cortical layers of the brain, indicating a new transmission route for the Rhes protein to the brain. Mechanistically, Rhes promotes such transmission via a direct cell-to-cell contact mediated by tunneling nanotubes (TNTs), the membranous protrusions that enable the transfer of mHTT, Rhes, and other vesicular cargoes. These transmission patterns suggest that Rhes and mHTT are likely co-transported in the brain using TNT-like cell-to-cell contacts. On the basis of these new results, a perspective is presented in this review: Rhes may ignite the mHTT transmission from the striatum that may coincide with HD onset and disease progression through an anatomically connected striato-cortical retrograde route.
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Coysh T, Mead S. The Future of Seed Amplification Assays and Clinical Trials. Front Aging Neurosci 2022; 14:872629. [PMID: 35813946 PMCID: PMC9257179 DOI: 10.3389/fnagi.2022.872629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 04/22/2022] [Indexed: 11/13/2022] Open
Abstract
Prion-like seeded misfolding of host proteins is the leading hypothesised cause of neurodegenerative diseases. The exploitation of the mechanism in the protein misfolding cyclic amplification (PMCA) and real-time quaking-induced conversion (RT-QuIC) assays have transformed prion disease research and diagnosis and have steadily become more widely used for research into other neurodegenerative disorders. Clinical trials in adult neurodegenerative diseases have been expensive, slow, and disappointing in terms of clinical benefits. There are various possible factors contributing to the failure to identify disease-modifying treatments for adult neurodegenerative diseases, some of which include: limited accuracy of antemortem clinical diagnosis resulting in the inclusion of patients with the “incorrect” pathology for the therapeutic; the role of co-pathologies in neurodegeneration rendering treatments targeting one pathology alone ineffective; treatment of the primary neurodegenerative process too late, after irreversible secondary processes of neurodegeneration have become established or neuronal loss is already extensive; and preclinical models used to develop treatments not accurately representing human disease. The use of seed amplification assays in clinical trials offers an opportunity to tackle these problems by sensitively detecting in vivo the proteopathic seeds thought to be central to the biology of neurodegenerative diseases, enabling improved diagnostic accuracy of the main pathology and co-pathologies, and very early intervention, particularly in patients at risk of monogenic forms of neurodegeneration. The possibility of quantifying proteopathic seed load, and its reduction by treatments, is an attractive pharmacodynamic biomarker in the preclinical and early clinical stages of drug development. Here we review some potential applications of seed amplification assays in clinical trials.
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Affiliation(s)
- Thomas Coysh
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, London, United Kingdom
- National Prion Clinic, National Hospital for Neurology and Neurosurgery, University College London Hospitals NHS Foundation Trust, London, United Kingdom
| | - Simon Mead
- MRC Prion Unit at UCL, UCL Institute of Prion Diseases, London, United Kingdom
- National Prion Clinic, National Hospital for Neurology and Neurosurgery, University College London Hospitals NHS Foundation Trust, London, United Kingdom
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6
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Roy M, Nath AK, Pal I, Dey SG. Second Sphere Interactions in Amyloidogenic Diseases. Chem Rev 2022; 122:12132-12206. [PMID: 35471949 DOI: 10.1021/acs.chemrev.1c00941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amyloids are protein aggregates bearing a highly ordered cross β structural motif, which may be functional but are mostly pathogenic. Their formation, deposition in tissues and consequent organ dysfunction is the central event in amyloidogenic diseases. Such protein aggregation may be brought about by conformational changes, and much attention has been directed toward factors like metal binding, post-translational modifications, mutations of protein etc., which eventually affect the reactivity and cytotoxicity of the associated proteins. Over the past decade, a global effort from different groups working on these misfolded/unfolded proteins/peptides has revealed that the amino acid residues in the second coordination sphere of the active sites of amyloidogenic proteins/peptides cause changes in H-bonding pattern or protein-protein interactions, which dramatically alter the structure and reactivity of these proteins/peptides. These second sphere effects not only determine the binding of transition metals and cofactors, which define the pathology of some of these diseases, but also change the mechanism of redox reactions catalyzed by these proteins/peptides and form the basis of oxidative damage associated with these amyloidogenic diseases. The present review seeks to discuss such second sphere modifications and their ramifications in the etiopathology of some representative amyloidogenic diseases like Alzheimer's disease (AD), type 2 diabetes mellitus (T2Dm), Parkinson's disease (PD), Huntington's disease (HD), and prion diseases.
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Affiliation(s)
- Madhuparna Roy
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Arnab Kumar Nath
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Ishita Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Somdatta Ghosh Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
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7
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Alpaugh M, Denis HL, Cicchetti F. Prion-like properties of the mutant huntingtin protein in living organisms: the evidence and the relevance. Mol Psychiatry 2022; 27:269-280. [PMID: 34711942 DOI: 10.1038/s41380-021-01350-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
If theories postulating that pathological proteins associated with neurodegenerative disorders behave similarly to prions were initially viewed with reluctance, it is now well-accepted that this occurs in several disease contexts. Notably, it has been reported that protein misfolding and subsequent prion-like properties can actively participate in neurodegenerative disorders. While this has been demonstrated in multiple cellular and animal model systems related to Alzheimer's and Parkinson's diseases, the prion-like properties of the mutant huntingtin protein (mHTT), associated with Huntington's disease (HD), have only recently been considered to play a role in this pathology, a concept our research group has contributed to extensively. In this review, we summarize the last few years of in vivo research in the field and speculate on the relationship between prion-like events and human HD. By interpreting observations primarily collected in in vivo models, our discussion will aim to discriminate which experimental factors contribute to the most efficient types of prion-like activities of mHTT and which routes of propagation may be more relevant to the human condition. A look back at nearly a decade of experimentation will inform future research and whether therapeutic strategies may emerge from this new knowledge.
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Affiliation(s)
- Melanie Alpaugh
- Centre de Recherche du CHU de Québec - Université Laval, Axe Neurosciences, Québec, QC, G1V 4G2, Canada.,Département de Psychiatrie & Neurosciences, Université Laval, Québec, QC, G1V 0A6, Canada
| | - Hélèna L Denis
- Centre de Recherche du CHU de Québec - Université Laval, Axe Neurosciences, Québec, QC, G1V 4G2, Canada.,Département de Psychiatrie & Neurosciences, Université Laval, Québec, QC, G1V 0A6, Canada
| | - Francesca Cicchetti
- Centre de Recherche du CHU de Québec - Université Laval, Axe Neurosciences, Québec, QC, G1V 4G2, Canada. .,Département de Psychiatrie & Neurosciences, Université Laval, Québec, QC, G1V 0A6, Canada.
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8
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Kim C, Yousefian-Jazi A, Choi SH, Chang I, Lee J, Ryu H. Non-Cell Autonomous and Epigenetic Mechanisms of Huntington's Disease. Int J Mol Sci 2021; 22:12499. [PMID: 34830381 PMCID: PMC8617801 DOI: 10.3390/ijms222212499] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 11/10/2021] [Accepted: 11/15/2021] [Indexed: 02/06/2023] Open
Abstract
Huntington's disease (HD) is a rare neurodegenerative disorder caused by an expansion of CAG trinucleotide repeat located in the exon 1 of Huntingtin (HTT) gene in human chromosome 4. The HTT protein is ubiquitously expressed in the brain. Specifically, mutant HTT (mHTT) protein-mediated toxicity leads to a dramatic degeneration of the striatum among many regions of the brain. HD symptoms exhibit a major involuntary movement followed by cognitive and psychiatric dysfunctions. In this review, we address the conventional role of wild type HTT (wtHTT) and how mHTT protein disrupts the function of medium spiny neurons (MSNs). We also discuss how mHTT modulates epigenetic modifications and transcriptional pathways in MSNs. In addition, we define how non-cell autonomous pathways lead to damage and death of MSNs under HD pathological conditions. Lastly, we overview therapeutic approaches for HD. Together, understanding of precise neuropathological mechanisms of HD may improve therapeutic approaches to treat the onset and progression of HD.
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Affiliation(s)
- Chaebin Kim
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Korea; (C.K.); (A.Y.-J.); (S.-H.C.)
| | - Ali Yousefian-Jazi
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Korea; (C.K.); (A.Y.-J.); (S.-H.C.)
| | - Seung-Hye Choi
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Korea; (C.K.); (A.Y.-J.); (S.-H.C.)
| | - Inyoung Chang
- Department of Biology, Boston University, Boston, MA 02215, USA;
| | - Junghee Lee
- Boston University Alzheimer’s Disease Research Center, Boston University, Boston, MA 02118, USA
- Department of Neurology, Boston University School of Medicine, Boston, MA 02118, USA
- VA Boston Healthcare System, Boston, MA 02130, USA
| | - Hoon Ryu
- Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Korea; (C.K.); (A.Y.-J.); (S.-H.C.)
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Chongtham A, Isas JM, Pandey NK, Rawat A, Yoo JH, Mastro T, Kennedy MB, Langen R, Khoshnan A. Amplification of neurotoxic HTTex1 assemblies in human neurons. Neurobiol Dis 2021; 159:105517. [PMID: 34563643 DOI: 10.1016/j.nbd.2021.105517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/24/2021] [Accepted: 09/21/2021] [Indexed: 11/25/2022] Open
Abstract
Huntington's disease (HD) is a genetically inherited neurodegenerative disorder caused by expansion of a polyglutamine (polyQ) repeat in the exon-1 of huntingtin protein (HTT). The expanded polyQ enhances the amyloidogenic propensity of HTT exon 1 (HTTex1), which forms a heterogeneous mixture of assemblies with a broad neurotoxicity spectrum. While predominantly intracellular, monomeric and aggregated mutant HTT species are also present in the cerebrospinal fluids of HD patients, however, their biological properties are not well understood. To explore the role of extracellular mutant HTT in aggregation and toxicity, we investigated the uptake and amplification of recombinant HTTex1 assemblies in cell culture models. We find that small HTTex1 fibrils preferentially enter human neurons and trigger the amplification of neurotoxic assemblies; astrocytes or epithelial cells are not permissive. The amplification of HTTex1 in neurons depletes endogenous HTT protein with non-pathogenic polyQ repeat, activates apoptotic caspase-3 pathway and induces nuclear fragmentation. Using a panel of novel monoclonal antibodies and genetic mutation, we identified epitopes within the N-terminal 17 amino acids and proline-rich domain of HTTex1 to be critical in neural uptake and amplification. Synaptosome preparations from the brain homogenates of HD mice also contain mutant HTT species, which enter neurons and behave similar to small recombinant HTTex1 fibrils. These studies suggest that amyloidogenic extracellular mutant HTTex1 assemblies may preferentially enter neurons, propagate and promote neurodegeneration.
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Affiliation(s)
| | - J Mario Isas
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Nitin K Pandey
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Anoop Rawat
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Jung Hyun Yoo
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Tara Mastro
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Mary B Kennedy
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA
| | - Ralf Langen
- Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, CA 90089, USA
| | - Ali Khoshnan
- Biology and Bioengineering, Caltech, Pasadena, CA 91125, USA.
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