Intracellular protein aggregation is the hallmark of several neurodegenerative diseases. Aggregates formed by polyglutamine (polyQ)-expanded proteins, such as Huntingtin, adopt amyloid-like structures that are resistant to denaturation. We used a novel purification strategy to isolate aggregates formed by human Huntingtin N-terminal fragments with expanded polyQ tracts from both yeast and mammalian (PC-12) cells. Using mass spectrometry we identified the protein species that are trapped within these polyQ aggregates. We found that proteins with very long intrinsically-disordered (ID) domains (≥ 100 amino acids) and RNA-binding proteins were disproportionately recruited into aggregates. The removal of the ID domains from selected proteins was sufficient to eliminate their recruitment into polyQ aggregates. We also observed that several neurodegenerative disease-linked proteins were reproducibly trapped within the polyQ aggregates purified from mammalian cells. Many of these proteins have large ID domains and are found in neuronal inclusions in their respective diseases. Our study indicates that neurodegenerative disease-associated proteins are particularly vulnerable to recruitment into polyQ aggregates via their ID domains. Also, the high frequency of ID domains in RNA-binding proteins may explain why RNA-binding proteins are frequently found in pathological inclusions in various neurodegenerative diseases.
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Adv Sci (Weinh)
January 2025
Department of Biomaterials & Biomedical Technology (BBT), University Medical Centre Groningen (UMCG), Antonius Deusinglaan 1, Groningen, 9713 AV, The Netherlands.
Free radicals are believed to play a secondary role in the cell death cascade associated with various diseases. In Huntington's disease (HD), the aggregation of polyglutamine (PolyQ) not only contributes to the disease but also elevates free radical levels. However, measuring free radicals is difficult due to their short lifespan and limited diffusion range.
View Article and Find Full Text PDFAntioxidants (Basel)
December 2024
Department of Nutrition, Chung Shan Medical University, Taichung 402, Taiwan.
Spinocerebellar ataxia type 3 (SCA3), caused by the abnormal expansion of polyglutamine (polyQ) in the ataxin-3 protein, is one of the inherited polyQ neurodegenerative diseases that share similar genetic and molecular features. Mutant polyQ-expanded ataxin-3 protein is prone to aggregation in affected neurons and is predominantly degraded by autophagy, which is beneficial for neurodegenerative disease treatment. Not only does mutant polyQ-expanded ataxin-3 increase susceptibility to oxidative cytotoxicity, but it also hampers antioxidant potency in neuronal cells.
View Article and Find Full Text PDFEClinicalMedicine
December 2024
Department of Neurology, Brain Research Institute, Niigata University, Niigata, Japan.
Background: Therapeutic advancements for the polyglutamine diseases, particularly spinocerebellar degeneration, are eagerly awaited. We evaluated the safety, tolerability, and therapeutic effects of L-arginine, which inhibits the conformational change and aggregation of polyglutamine proteins, in patients with spinocerebellar ataxia type 6 (SCA6).
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Nat Cell Biol
January 2025
Department of Biochemistry and Molecular Biology, the Institute for Medical Research Israel-Canada, the Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel.
The protein homeostasis (proteostasis) network encompasses a myriad of mechanisms that maintain the integrity of the proteome by controlling various biological functions, including protein folding and degradation. Alas, ageing-associated decline in the efficiency of this network enables protein aggregation and consequently the development of late-onset neurodegenerative disorders, such as Alzheimer's disease. Accordingly, the maintenance of proteostasis through late stages of life bears the promise to delay the emergence of these devastating diseases.
View Article and Find Full Text PDFNat Commun
December 2024
Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany.
Neurodegeneration in Huntington's disease (HD) is accompanied by the aggregation of fragments of the mutant huntingtin protein, a biomarker of disease progression. A particular pathogenic role has been attributed to the aggregation-prone huntingtin exon 1 (HTTex1), generated by aberrant splicing or proteolysis, and containing the expanded polyglutamine (polyQ) segment. Unlike amyloid fibrils from Parkinson's and Alzheimer's diseases, the atomic-level structure of HTTex1 fibrils has remained unknown, limiting diagnostic and treatment efforts.
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