| 1. |
- Brorsson, Ann-Christin, et al.
(author)
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Intrinsic determinants of neurotoxic aggregate formation by the amyloid beta peptide
- 2010
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In: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 98:8, s. 1677-84
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Journal article (peer-reviewed)abstract
- The extent to which proteins aggregate into distinct structures ranging from prefibrillar oligomers to amyloid fibrils is key to the pathogenesis of many age-related degenerative diseases. We describe here for the Alzheimer's disease-related amyloid beta peptide (Abeta) an investigation of the sequence-based determinants of the balance between the formation of prefibrillar aggregates and amyloid fibrils. We show that by introducing single-point mutations, it is possible to convert the normally harmless Abeta40 peptide into a pathogenic species by increasing its relative propensity to form prefibrillar but not fibrillar aggregates, and, conversely, to abolish the pathogenicity of the highly neurotoxic E22G Abeta42 peptide by reducing its relative propensity to form prefibrillar species rather than mature fibrillar ones. This observation can be rationalized by the demonstration that whereas regions of the sequence of high aggregation propensity dominate the overall tendency to aggregate, regions with low intrinsic aggregation propensities exert significant control over the balance of the prefibrillar and fibrillar species formed, and therefore play a major role in determining the neurotoxicity of the Abeta peptide.
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| 2. |
- Brorsson, Ann-Christin, et al.
(author)
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Methods and models in neurodegenerative and systemic protein aggregation diseases
- 2010
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In: Frontiers in bioscience : a journal and virtual library. - : Frontiers in Bioscience Publications. - 1093-4715. ; 15, s. 373-396
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Research review (peer-reviewed)abstract
- Protein misfolding and aggregation are implicated in a wide range of increasingly prevalent human diseases ranging from dementia to diabetes. In this review we discuss the current experimental strategies that are being employed in the investigation of the pathogenesis of three important protein misfolding disorders. The first, Alzheimers disease (AD), is the most prevalent neurodegenerative disease and is thought to be initiated by the aggregation of a natively unstructured peptide called amyloid beta (Abeta). We discuss methods for the characterization of the aggregation properties of Abeta in vitro and how the results of such experiments can be correlated with data from animal models of disease. We then consider another form of amyloidosis, where a systemic distribution of amyloid deposit is caused by aggregation and deposition of mutational variants of lysozyme. We describe how experiments in vitro, and more recently in vivo, have provided insights into the origins of this disease. Finally we outline the varied paradigms that have been employed in the study of the serpinopathies, and in particular, a dementia caused by neuroserpin polymerization.
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| 3. |
- Luheshi, Leila M., et al.
(author)
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Sequestration of the A beta Peptide Prevents Toxicity and Promotes Degradation In Vivo
- 2010
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In: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 8:3, s. e1000334-
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Journal article (peer-reviewed)abstract
- Protein aggregation, arising from the failure of the cell to regulate the synthesis or degradation of aggregation-prone proteins, underlies many neurodegenerative disorders. However, the balance between the synthesis, clearance, and assembly of misfolded proteins into neurotoxic aggregates remains poorly understood. Here we study the effects of modulating this balance for the amyloid-beta (A beta) peptide by using a small engineered binding protein (Z(A beta 3)) that binds with nanomolar affinity to A beta, completely sequestering the aggregation-prone regions of the peptide and preventing its aggregation. Co-expression of Z(A beta 3) in the brains of Drosophila melanogaster expressing either A beta(42) or the aggressive familial Alzheimer's disease (AD) associated E22G variant of A beta(42) abolishes their neurotoxic effects. Biochemical analysis indicates that monomer A beta binding results in degradation of the peptide in vivo. Complementary biophysical studies emphasize the dynamic nature of A beta aggregation and reveal that Z(A beta 3) not only inhibits the initial association of A beta monomers into oligomers or fibrils, but also dissociates pre-formed oligomeric aggregates and, although very slowly, amyloid fibrils. Toxic effects of peptide aggregation in vivo can therefore be eliminated by sequestration of hydrophobic regions in monomeric peptides, even when these are extremely aggregation prone. Our studies also underline how a combination of in vivo and in vitro experiments provide mechanistic insight with regard to the relationship between protein aggregation and clearance and show that engineered binding proteins may provide powerful tools with which to address the physiological and pathological consequences of protein aggregation.
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| 4. |
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| 5. |
- Sandberg, Anders, et al.
(author)
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Stabilization of neurotoxic Alzheimer amyloid-beta oligomers by protein engineering
- 2010
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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 .- 1091-6490. ; 107:35, s. 15595-15600
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Journal article (peer-reviewed)abstract
- Soluble oligomeric aggregates of the amyloid-beta peptide (Abeta) have been implicated in the pathogenesis of Alzheimer's disease (AD). Although the conformation adopted by Abeta within these aggregates is not known, a beta-hairpin conformation is known to be accessible to monomeric Abeta. Here we show that this beta-hairpin is a building block of toxic Abeta oligomers by engineering a double-cysteine mutant (called Abetacc) in which the beta-hairpin is stabilized by an intramolecular disulfide bond. Abeta(40)cc and Abeta(42)cc both spontaneously form stable oligomeric species with distinct molecular weights and secondary-structure content, but both are unable to convert into amyloid fibrils. Biochemical and biophysical experiments and assays with conformation-specific antibodies used to detect Abeta aggregates in vivo indicate that the wild-type oligomer structure is preserved and stabilized in Abetacc oligomers. Stable oligomers are expected to become highly toxic and, accordingly, we find that beta-sheet-containing Abeta(42)cc oligomers or protofibrillar species formed by these oligomers are 50 times more potent inducers of neuronal apoptosis than amyloid fibrils or samples of monomeric wild-type Abeta(42), in which toxic aggregates are only transiently formed. The possibility of obtaining completely stable and physiologically relevant neurotoxic Abeta oligomer preparations will facilitate studies of their structure and role in the pathogenesis of AD. For example, here we show how kinetic partitioning into different aggregation pathways can explain why Abeta(42) is more toxic than the shorter Abeta(40), and why certain inherited mutations are linked to protofibril formation and early-onset AD.
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