| 1. |
- Carra, Serena, et al.
(författare)
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The growing world of small heat shock proteins : from structure to functions
- 2017
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Ingår i: Cell Stress and Chaperones. - : Springer Science and Business Media LLC. - 1355-8145 .- 1466-1268. ; 22:4, s. 601-611
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Tidskriftsartikel (refereegranskat)abstract
- Small heat shock proteins (sHSPs) are present in all kingdoms of life and play fundamental roles in cell biology. sHSPs are key components of the cellular protein quality control system, acting as the first line of defense against conditions that affect protein homeostasis and proteome stability, from bacteria to plants to humans. sHSPs have the ability to bind to a large subset of substrates and to maintain them in a state competent for refolding or clearance with the assistance of the HSP70 machinery. sHSPs participate in a number of biological processes, from the cell cycle, to cell differentiation, from adaptation to stressful conditions, to apoptosis, and, even, to the transformation of a cell into a malignant state. As a consequence, sHSP malfunction has been implicated in abnormal placental development and preterm deliveries, in the prognosis of several types of cancer, and in the development of neurological diseases. Moreover, mutations in the genes encoding several mammalian sHSPs result in neurological, muscular, or cardiac age-related diseases in humans. Loss of protein homeostasis due to protein aggregation is typical of many age-related neurodegenerative and neuromuscular diseases. In light of the role of sHSPs in the clearance of un/misfolded aggregation-prone substrates, pharmacological modulation of sHSP expression or function and rescue of defective sHSPs represent possible routes to alleviate or cure protein conformation diseases. Here, we report the latest news and views on sHSPs discussed by many of the world’s experts in the sHSP field during a dedicated workshop organized in Italy (Bertinoro, CEUB, October 12–15, 2016).
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| 2. |
- Kakkar, Vaishali, et al.
(författare)
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The S/T-Rich Motif in the DNAJB6 Chaperone Delays Polyglutamine Aggregation and the Onset of Disease in a Mouse Model
- 2016
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765. ; 62:2, s. 272-283
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Tidskriftsartikel (refereegranskat)abstract
- Expanded CAG repeats lead to debilitating neurodegenerative disorders characterized by aggregation of proteins with expanded polyglutamine (polyQ) tracts. The mechanism of aggregation involves primary and secondary nucleation steps. We show how a noncanonical member of the DNAJ-chaperone family, DNAJB6, inhibits the conversion of soluble polyQ peptides into amyloid fibrils, in particular by suppressing primary nucleation. This inhibition is mediated by a serine/threonine-rich region that provides an array of surface-exposed hydroxyl groups that bind to polyQ peptides and may disrupt the formation of the H bonds essential for the stability of amyloid fibrils. Early prevention of polyQ aggregation by DNAJB6 occurs also in cells and leads to delayed neurite retraction even before aggregates are visible. In a mouse model, brain-specific coexpression of DNAJB6 delays polyQ aggregation, relieves symptoms, and prolongs lifespan, pointing to DNAJB6 as a potential target for disease therapy and tool for unraveling early events in the onset of polyQ diseases. Kakkar et al. show that DNAJB6 is a chaperone that inhibits early steps in the formation of polyQ amyloid fibrils. An S/T-rich region in DNAJB6 is crucial for this function. In a polyQ mouse model, the inhibitory effects of DNAJB6 delay disease onset and increase lifespan.
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| 3. |
- Månsson, Cecilia, et al.
(författare)
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Interaction of the molecular chaperone DNAJB6 with growing amyloid-beta 42 (Aβ42) aggregates leads to sub-stoichiometric inhibition of amyloid formation.
- 2014
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 289:45, s. 31066-31076
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Tidskriftsartikel (refereegranskat)abstract
- The human molecular chaperone protein DNAJB6 was recently found to inhibit the formation of amyloid fibrils from polyglutamine peptides associated with neurodegenerative disorders such as Huntington's disease. We show in the present study that DNAJB6 also inhibits amyloid formation by an even more aggregation-prone peptide (the amyloid-beta peptide, (Aβ42)(2), implicated in Alzheimer's disease)in a highly efficient manner. By monitoring fibril formation using Thioflavin T fluorescence and far-UV CD spectroscopy, we have found that the aggregation of Aβ42 is retarded by DNAJB6 in a concentration dependent manner, extending to very low sub-stoichiometric molar ratios of chaperone to peptide. Quantitative kinetic analysis and immunochemistry studies suggest that the high inhibitory efficiency is due to the interactions of the chaperone with aggregated forms of Aβ42 rather than the monomeric form of the peptide. This interaction prevents the growth of such species to longer fibrils and inhibits the formation of new amyloid fibrils through both primary and secondary nucleation. A low dissociation rate of DNAJB6 from Aβ42 aggregates leads to its incorporation into growing fibrils and hence to its gradual depletion from solution with time. When DNAJB6 is eventually depleted, fibril proliferation takes place, but the inhibitory activity can be prolonged by introducing DNAJB6 at regular intervals during the aggregation reaction. These results reveal the highly efficacious mode of action of this molecular chaperone against protein aggregation, and demonstrate that the role of molecular chaperones can involve interactions with multiple aggregated species leading to the inhibition of both principal nucleation pathways through which aggregates are able to form.
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| 4. |
- Arosio, Paolo, et al.
(författare)
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Kinetic analysis reveals the diversity of microscopic mechanisms through which molecular chaperones suppress amyloid formation
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- It is increasingly recognized that molecular chaperones play a key role in modulating the formation of amyloid fibrils, a process associated with a wide range of human disorders. Understanding the detailed mechanisms by which they perform this function, however, has been challenging because of the great complexity of the protein aggregation process itself. In this work, we build on a previous kinetic approach and develop a model that considers pairwise interactions between molecular chaperones and different protein species to identify the protein components targeted by the chaperones and the corresponding microscopic reaction steps that are inhibited. We show that these interactions conserve the topology of the unperturbed reaction network but modify the connectivity weights between the different microscopic steps. Moreover, by analysing several protein-molecular chaperone systems, we reveal the striking diversity in the microscopic mechanisms by which molecular chaperones act to suppress amyloid formation.
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| 5. |
- Everberg, Henrik, et al.
(författare)
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Protein pre-fractionation in detergent-polymer aqueous two-phase systems for facilitated proteomic studies of membrane proteins
- 2004
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1029:1-2, s. 113-124
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Tidskriftsartikel (refereegranskat)abstract
- Pre-fractionation of a complex mixture of proteins increases the resolution in analytical separations of proteins from cells, tissues or organisms. Here we demonstrate a novel method for pre-fractionation of membrane proteins by a detergent-based aqueous two-phase system. Membrane proteins are strongly under-represented in proteomic studies based on two-dimensional electrophoresis (2-DE). As a model system, we have isolated mitochondria from the yeast Saccharomyces cerevisiae. Mitochondrial proteins were fractionated in an aqueous two-phase system consisting of the polymer poly(ethylene glycol) and either of two commonly used non-ionic detergents, Triton X-114 or dodecyl maltoside (DDM). Soluble proteins partitioned mainly to the polymer phase while membrane proteins were enriched in the detergent phase, as identified from one-dimensional electrophoresis (I-DE) and/or 2-DE followed by mass spectrometric analysis. Pre-fractionation was further enhanced by addition of an anionic detergent, sodium dodecyl sulfate, or a chaotropic salt, NaClO4, and by raising the pH in the system. The two-phase system pre-fractionation was furthermore combined with an alternative two-dimensional high-resolution separation method, namely ion-exchange chromatography and 1-DE. By this approach a larger number of membrane proteins could be identified compared to separation with conventional 2-DE. Thus, pre-fractionation of complex protein mixtures using the aqueous two-phase systems developed here will help to disclose larger proportions of membrane proteins in different proteomes. (C) 2004 Elsevier B.V. All rights reserved.
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| 6. |
- Flagmeier, Patrick, et al.
(författare)
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Direct measurement of lipid membrane disruption connects kinetics and toxicity of Aβ42 aggregation
- 2020
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Ingår i: Nature Structural and Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 27:10, s. 886-891
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Tidskriftsartikel (refereegranskat)abstract
- The formation of amyloid deposits in human tissues is a defining feature of more than 50 medical disorders, including Alzheimer’s disease. Strong genetic and histological evidence links these conditions to the process of protein aggregation, yet it has remained challenging to identify a definitive connection between aggregation and pathogenicity. Using time-resolved fluorescence microscopy of individual synthetic vesicles, we show for the Aβ42 peptide implicated in Alzheimer’s disease that the disruption of lipid bilayers correlates linearly with the time course of the levels of transient oligomers generated through secondary nucleation. These findings indicate a specific role of oligomers generated through the catalytic action of fibrillar species during the protein aggregation process in driving deleterious biological function and establish a direct causative connection between amyloid formation and its pathological effects.
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