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| 2. |
- Ng, Janice S.W., et al.
(author)
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Using Tetracysteine-Tagged TDP-43 with a Biarsenical Dye to Monitor Real-Time Trafficking in a Cell Model of Amyotrophic Lateral Sclerosis
- 2019
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In: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 58:39, s. 4086-4095
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Journal article (peer-reviewed)abstract
- TAR DNA-binding protein 43 (TDP-43) has been identified as the major constituent of the proteinaceous inclusions that are characteristic of most forms of amyotrophic lateral sclerosis (ALS) and ubiquitin positive frontotemporal lobar degeneration (FTLD). Wild type TDP-43 inclusions are a pathological hallmark of >95% of patients with sporadic ALS and of the majority of familial ALS cases, and they are also found in a significant proportion of FTLD cases. ALS is the most common form of motor neuron disease, characterized by progressive weakness and muscular wasting, and typically leads to death within a few years of diagnosis. To determine how the translocation and misfolding of TDP-43 contribute to ALS pathogenicity, it is crucial to define the dynamic behavior of this protein within the cellular environment. It is therefore necessary to develop cell models that allow the location of the protein to be defined. We report the use of TDP-43 with a tetracysteine tag for visualization using fluorogenic biarsenical compounds and show that this model displays features of ALS observed in other cell models. We also demonstrate that this labeling procedure enables live-cell imaging of the translocation of the protein from the nucleus into the cytosol.
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| 3. |
- Scheidt, Tom, et al.
(author)
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Secondary nucleation and elongation occur at different sites on Alzheimer's amyloid-b aggregates
- 2019
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In: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:4
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Journal article (peer-reviewed)abstract
- The aggregates of the Ab peptide associated with Alzheimer's disease are able to both grow in size aswell as generate, through secondary nucleation, new small oligomeric species, that are major cytotoxins associated with neuronal death. Despite the importance of these amyloid fibril-dependent processes, their structural and molecular underpinnings have remained challenging to elucidate. Here, we consider two molecular chaperones: The Brichos domain, which suppresses specifically secondary nucleation processes, and clusterin which our results show is capable of inhibiting, specifically, the elongation of Ab fibrils at remarkably low substoichiometric ratios. Microfluidic diffusional sizing measurements demonstrate that this inhibition originates from interactions of clusterin with fibril ends with high affinity. Kinetic experiments in the presence of both molecular chaperones reveal that their inhibitory effects are additive and noncooperative, thereby indicating that the reactive sites associated with the formation of new aggregates and the growth of existing aggregates are distinct.
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| 4. |
- Habchi, Johnny, et al.
(author)
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Cholesterol catalyses Aβ42 aggregation through a heterogeneous nucleation pathway in the presence of lipid membranes
- 2018
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In: Nature Chemistry. - : Springer Science and Business Media LLC. - 1755-4330 .- 1755-4349. ; 10:6, s. 673-683
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Journal article (peer-reviewed)abstract
- Alzheimer’s disease is a neurodegenerative disorder associated with the aberrant aggregation of the amyloid-β peptide. Although increasing evidence implicates cholesterol in the pathogenesis of Alzheimer’s disease, the detailed mechanistic link between this lipid molecule and the disease process remains to be fully established. To address this problem, we adopt a kinetics-based strategy that reveals a specific catalytic role of cholesterol in the aggregation of Aβ42 (the 42-residue form of the amyloid-β peptide). More specifically, we demonstrate that lipid membranes containing cholesterol promote Aβ42 aggregation by enhancing its primary nucleation rate by up to 20-fold through a heterogeneous nucleation pathway. We further show that this process occurs as a result of cooperativity in the interaction of multiple cholesterol molecules with Aβ42. These results identify a specific microscopic pathway by which cholesterol dramatically enhances the onset of Aβ42 aggregation, thereby helping rationalize the link between Alzheimer’s disease and the impairment of cholesterol homeostasis.
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| 5. |
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| 6. |
- Aran Terol, P., et al.
(author)
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Solvent exposure of Tyr10 as a probe of structural differences between monomeric and aggregated forms of the amyloid-β peptide
- 2015
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In: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 468:4, s. 696-701
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Journal article (peer-reviewed)abstract
- Aggregation of amyloid-β (Aβ) peptides is a characteristic pathological feature of Alzheimer's disease. We have exploited the relationship between solvent exposure and intrinsic fluorescence of a single tyrosine residue, Tyr10, in the Aβ sequence to probe structural features of the monomeric, oligomeric and fibrillar forms of the 42-residue Aβ1-42. By monitoring the quenching of Tyr10 fluorescence upon addition of water-soluble acrylamide, we show that in Aβ1-42 oligomers this residue is solvent-exposed to a similar extent to that found in the unfolded monomer. By contrast, Tyr10 is significantly shielded from acrylamide quenching in Aβ1-42 fibrils, consistent with its proximity to the fibrillar cross-β core. Furthermore, circular dichroism measurements reveal that Aβ1-42 oligomers have a considerably lower β-sheet content than the Aβ1-42 fibrils, indicative of a less ordered molecular arrangement in the former. Taken together these findings suggest significant differences in the structural assembly of oligomers and fibrils that are consistent with differences in their biological effects.
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| 7. |
- Cataldi, Rodrigo, et al.
(author)
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A dopamine metabolite stabilizes neurotoxic amyloid-β oligomers
- 2021
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 4:1
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Journal article (peer-reviewed)abstract
- Aberrant soluble oligomers formed by the amyloid-β peptide (Aβ) are major pathogenic agents in the onset and progression of Alzheimer’s disease. A variety of biomolecules can influence the formation of these oligomers in the brain, although their mechanisms of action are still largely unknown. Here, we studied the effects on Aβ aggregation of DOPAL, a reactive catecholaldehyde intermediate of dopamine metabolism. We found that DOPAL is able to stabilize Aβ oligomeric species, including dimers and trimers, that exert toxic effects on human neuroblastoma cells, in particular increasing cytosolic calcium levels and promoting the generation of reactive oxygen species. These results reveal an interplay between Aβ aggregation and key biochemical processes regulating cellular homeostasis in the brain.
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| 8. |
- Habchi, Johnny, et al.
(author)
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Systematic development of small molecules to inhibit specific microscopic steps of Aβ42 aggregation in Alzheimer's disease
- 2017
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 114:2, s. 200-208
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Journal article (peer-reviewed)abstract
- The aggregation of the 42-residue form of the amyloid-β peptide (Aβ42) is a pivotal event in Alzheimer's disease (AD). The use of chemical kinetics has recently enabled highly accurate quantifications of the effects of small molecules on specific microscopic steps in Aβ42 aggregation. Here, we exploit this approach to develop a rational drug discovery strategy against Aβ42 aggregation that uses as a readout the changes in the nucleation and elongation rate constants caused by candidate small molecules. We thus identify a pool of compounds that target specific microscopic steps in Aβ42 aggregation. We then test further these small molecules in human cerebrospinal fluid and in a Caenorhabditis elegans model of AD. Our results show that this strategy represents a powerful approach to identify systematically small molecule lead compounds, thus offering an appealing opportunity to reduce the attrition problem in drug discovery.
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| 9. |
- Limbocker, Ryan, et al.
(author)
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Trodusquemine enhances Aβ42 aggregation but suppresses its toxicity by displacing oligomers from cell membranes
- 2019
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
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Journal article (peer-reviewed)abstract
- Transient oligomeric species formed during the aggregation process of the 42-residue form of the amyloid-β peptide (Aβ42) are key pathogenic agents in Alzheimer’s disease (AD). To investigate the relationship between Aβ42 aggregation and its cytotoxicity and the influence of a potential drug on both phenomena, we have studied the effects of trodusquemine. This aminosterol enhances the rate of aggregation by promoting monomer-dependent secondary nucleation, but significantly reduces the toxicity of the resulting oligomers to neuroblastoma cells by inhibiting their binding to the cellular membranes. When administered to a C. elegans model of AD, we again observe an increase in aggregate formation alongside the suppression of Aβ42-induced toxicity. In addition to oligomer displacement, the reduced toxicity could also point towards an increased rate of conversion of oligomers to less toxic fibrils. The ability of a small molecule to reduce the toxicity of oligomeric species represents a potential therapeutic strategy against AD.
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