| 1. |
- Kurzawa-Akanbi, M., et al.
(author)
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Altered ceramide metabolism is a feature in the extracellular vesicle-mediated spread of alpha-synuclein in Lewy body disorders
- 2021
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In: Acta Neuropathologica. - : Springer Science and Business Media LLC. - 0001-6322 .- 1432-0533. ; 142, s. 961-984
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Journal article (peer-reviewed)abstract
- Mutations in glucocerebrosidase (GBA) are the most prevalent genetic risk factor for Lewy body disorders (LBD)-collectively Parkinson's disease, Parkinson's disease dementia and dementia with Lewy bodies. Despite this genetic association, it remains unclear how GBA mutations increase susceptibility to develop LBD. We investigated relationships between LBD-specific glucocerebrosidase deficits, GBA-related pathways, and alpha-synuclein levels in brain tissue from LBD and controls, with and without GBA mutations. We show that LBD is characterised by altered sphingolipid metabolism with prominent elevation of ceramide species, regardless of GBA mutations. Since extracellular vesicles (EV) could be involved in LBD pathogenesis by spreading disease-linked lipids and proteins, we investigated EV derived from post-mortem cerebrospinal fluid (CSF) and brain tissue from GBA mutation carriers and non-carriers. EV purified from LBD CSF and frontal cortex were heavily loaded with ceramides and neurodegeneration-linked proteins including alpha-synuclein and tau. Our in vitro studies demonstrate that LBD EV constitute a "pathological package" capable of inducing aggregation of wild-type alpha-synuclein, mediated through a combination of alpha-synuclein-ceramide interaction and the presence of pathological forms of alpha-synuclein. Together, our findings indicate that abnormalities in ceramide metabolism are a feature of LBD, constituting a promising source of biomarkers, and that GBA mutations likely accelerate the pathological process occurring in sporadic LBD through endolysosomal deficiency.
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| 2. |
- Burmann, Björn Marcus, 1979, et al.
(author)
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Regulation of alpha-synuclein by chaperones in mammalian cells
- 2020
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 577:7788, s. 127-32
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Journal article (peer-reviewed)abstract
- Neurodegeneration in patients with Parkinson's disease is correlated with the occurrence of Lewy bodies-intracellular inclusions that contain aggregates of the intrinsically disordered protein alpha-synuclein(1). The aggregation propensity of alpha-synuclein in cells is modulated by specific factors that include post-translational modifications(2,3), Abelson-kinase-mediated phosphorylation(4,5) and interactions with intracellular machineries such as molecular chaperones, although the underlying mechanisms are unclear(6-8). Here we systematically characterize the interaction of molecular chaperones with alpha-synuclein in vitro as well as in cells at the atomic level. We find that six highly divergent molecular chaperones commonly recognize a canonical motif in alpha-synuclein, consisting of the N terminus and a segment around Tyr39, and hinder the aggregation of alpha-synuclein. NMR experiments(9) in cells show that the same transient interaction pattern is preserved inside living mammalian cells. Specific inhibition of the interactions between alpha-synuclein and the chaperone HSC70 and members of the HSP90 family, including HSP90 beta, results in transient membrane binding and triggers a remarkable re-localization of alpha-synuclein to the mitochondria and concomitant formation of aggregates. Phosphorylation of alpha-synuclein at Tyr39 directly impairs the interaction of alpha-synuclein with chaperones, thus providing a functional explanation for the role of Abelson kinase in Parkinson's disease. Our results establish a master regulatory mechanism of alpha-synuclein function and aggregation in mammalian cells, extending the functional repertoire of molecular chaperones and highlighting new perspectives for therapeutic interventions for Parkinson's disease.
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| 3. |
- Lesovoy, D. M., et al.
(author)
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Unambiguous Tracking of Protein Phosphorylation by Fast High-Resolution FOSY NMR**
- 2021
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In: Angewandte Chemie-International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 60:44, s. 23540-23544
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Journal article (peer-reviewed)abstract
- Dysregulation of post-translational modifications (PTMs) like phosphorylation is often involved in disease. NMR may elucidate exact loci and time courses of PTMs at atomic resolution and near-physiological conditions but requires signal assignment to individual atoms. Conventional NMR methods for this base on tedious global signal assignment that may often fail, as for large intrinsically disordered proteins (IDPs). We present a sensitive, robust alternative to rapidly obtain only the local assignment near affected signals, based on FOcused SpectroscopY (FOSY) experiments using selective polarisation transfer (SPT). We prove its efficiency by identifying two phosphorylation sites of glycogen synthase kinase 3 beta (GSK3 beta) in human Tau40, an IDP of 441 residues, where the extreme spectral dispersion in FOSY revealed unprimed phosphorylation also of Ser409. FOSY may broadly benefit NMR studies of PTMs and other hotspots in IDPs, including sites involved in molecular interactions.
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| 4. |
- Holdbrook, D. A., et al.
(author)
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A Spring-Loaded Mechanism Governs the Clamp-like Dynamics of the Skp Chaperone
- 2017
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In: Structure. - : Elsevier BV. - 0969-2126. ; 25:7
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Journal article (peer-reviewed)abstract
- The trimeric periplasmic holdase chaperone Skp binds and stabilizes unfolded outer membrane proteins (OMPs) as part of bacterial OMP biogenesis. Skp binds client proteins in its central cavity, thereby reducing its backbone dynamics, but the molecular mechanisms that govern Skp dynamics and adaptation to differently sized clients remains unknown. Here, we employ a combination of microsecond time-scale molecular dynamics simulation, small-angle X-ray scattering, and nuclear magnetic resonance spectroscopy to reveal that Skp is remarkably flexible, and features a molecular spring-loaded mechanism in its "tentacle'' arms that enables switching between two distinct conformations on sub-millisecond timescales. The conformational switch is executed around a conserved pivot element within the coiled-coil structures of the tentacles, allowing expansion of the cavity and thus accommodation of differently sized clients. The spring-loaded mechanism shows how a chaperone can efficiently modulate its structure and function in an ATP-independent manner.
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| 5. |
- Horvath, Istvan, 1979, et al.
(author)
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Interaction between Copper Chaperone Atox1 and Parkinson's Disease Protein α-Synuclein Includes Metal-Binding Sites and Occurs in Living Cells
- 2019
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In: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 10:11, s. 4659-4668
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Journal article (peer-reviewed)abstract
- Alterations in copper ion homeostasis appear coupled to neurodegenerative disorders, but mechanisms are unknown. The cytoplasmic copper chaperone Atox1 was recently found to inhibit amyloid formation in vitro of α-synuclein, the amyloidogenic protein in Parkinson's disease. As α-synuclein may have copper-dependent functions, and free copper ions promote α-synuclein amyloid formation, it is important to characterize the Atox1 interaction with α-synuclein on a molecular level. Here we applied solution-state nuclear magnetic resonance spectroscopy, with isotopically labeled α-synuclein and Atox1, to define interaction regions in both proteins. The α-synuclein interaction interface includes the whole N-terminal part up to Gln24; in Atox1, residues around the copper-binding cysteines (positions 11-16) are mostly perturbed, but additional effects are also found for residues elsewhere in both proteins. Because α-synuclein is N-terminally acetylated in vivo, we established that Atox1 also inhibits amyloid formation of this variant in vitro, and proximity ligation in human cell lines demonstrated α-synuclein-Atox1 interactions in situ. Thus, this interaction may provide the direct link between copper homeostasis and amyloid formation in vivo.
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| 6. |
- Lindström, Michelle, et al.
(author)
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Lsm7 phase-separated condensates trigger stress granule formation
- 2022
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Journal article (peer-reviewed)abstract
- Stress granules are non-membranous organelles connected to stress responses and age-related disease. Here, the authors identify a conserved yeast protein, Lsm7, that facilitates stress granule formation through dynamic liquid-liquid phase separation condensates upon 2-deoxy-D-glucose-induced stress. Stress granules (SGs) are non-membranous organelles facilitating stress responses and linking the pathology of age-related diseases. In a genome-wide imaging-based phenomic screen, we identify Pab1 co-localizing proteins under 2-deoxy-D-glucose (2-DG) induced stress in Saccharomyces cerevisiae. We find that deletion of one of the Pab1 co-localizing proteins, Lsm7, leads to a significant decrease in SG formation. Under 2-DG stress, Lsm7 rapidly forms foci that assist in SG formation. The Lsm7 foci form via liquid-liquid phase separation, and the intrinsically disordered region and the hydrophobic clusters within the Lsm7 sequence are the internal driving forces in promoting Lsm7 phase separation. The dynamic Lsm7 phase-separated condensates appear to work as seeding scaffolds, promoting Pab1 demixing and subsequent SG initiation, seemingly mediated by RNA interactions. The SG initiation mechanism, via Lsm7 phase separation, identified in this work provides valuable clues for understanding the mechanisms underlying SG formation and SG-associated human diseases.
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