Pathology - Research Publications
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ItemAlpha-synuclein oligomers and fibrils originate in two distinct conformer pools: a small angle X-ray scattering and ensemble optimisation modelling study(ROYAL SOC CHEMISTRY, 2015-01)The 140 residue intrinsically disordered protein α-synuclein (α-syn) self-associates to form fibrils that are the major constituent of the Lewy body intracellular protein inclusions, and neurotoxic oligomers. Both of these macromolecular structures are associated with a number of neurodegenerative diseases, including Parkinson's disease and dementia with Lewy bodies. Using ensemble optimisation modelling (EOM) and small angle X-ray scattering (SAXS) on a size-exclusion column equipped beamline, we studied how the distribution of structural conformers in α-syn may be influenced by the presence of the familial early-onset mutations A30P, E45K and A53T, by substituting the four methionine residues with alanines and by reaction with copper (Cu2+) or an anti-fibril organic platinum (Pt) complex. We found that the WT had two major conformer groups, representing ensembles of compact and extended structures. The population of the extended group was increased in the more rapidly fibril-forming E45K and A53T mutants, while the compact group was enlarged in the oligomer-forming A30P mutant. Addition of Cu2+ resulted in the formation of an ensemble of compact conformers, while the anti-fibril agent and alanine substitution substantially reduced the population of extended conformers. Since our observations with the mutants suggest that fibrils may be drawn from the extended conformer ensemble, we propose that the compact and extended ensembles represent the beginning of oligomer and fibril formation pathways respectively, both of which have been reported to lead to a toxic gain of function. Manipulating these pathways and monitoring the results by EOM and SAXS may be useful in the development of anti-Parkinson's disease therapies.
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ItemUtility of an improved model of amyloid-beta (Aβ1-42) toxicity in Caenorhabditis elegans for drug screening for Alzheimer's disease(BMC, 2012-11-21)BACKGROUND: The definitive indicator of Alzheimer's disease (AD) pathology is the profuse accumulation of amyloid-ß (Aß) within the brain. Various in vitro and cell-based models have been proposed for high throughput drug screening for potential therapeutic benefit in diseases of protein misfolding. Caenorhabditis elegans offers a convenient in vivo system for examination of Aß accumulation and toxicity in a complex multicellular organism. Ease of culturing and a short life cycle make this animal model well suited to rapid screening of candidate compounds. RESULTS: We have generated a new transgenic strain of C. elegans that expresses full length Aß₁₋₄₂. This strain differs from existing Aß models that predominantly express amino-truncated Aß₃₋₄₂. The Aß₁₋₄₂ is expressed in body wall muscle cells, where it oligomerizes, aggregates and results in severe, and fully penetrant, age progressive-paralysis. The in vivo accumulation of Aß₁₋₄₂ also stains positive for amyloid dyes, consistent with in vivo fibril formation. The utility of this model for identification of potential protective compounds was examined using the investigational Alzheimer's therapeutic PBT2, shown to be neuroprotective in mouse models of AD and significantly improve cognition in AD patients. We observed that treatment with PBT2 provided rapid and significant protection against the Aß-induced toxicity in C. elegans. CONCLUSION: This C. elegans model of full length Aß₁₋₄₂ expression can now be adopted for use in screens to rapidly identify and assist in development of potential therapeutics and to study underlying toxic mechanism(s) of Aß.
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ItemBACE inhibitors as potential therapeutics for Alzheimer's disease.(Bentham Science Publishers Ltd., 2007-11)Accumulation of Abeta peptide in the brain results in the formation of amyloid plaques characteristic of Alzheimer's disease (AD) pathology. Abeta soluble oligomers and protofibrils are neurotoxic and these are believed to be a major cause of neurodegeneration in AD. Abeta is derived from a precursor protein by two sequential cleavage steps involving beta- and gamma-secretases, two proteolytic enzymes that represent rational drug targets. beta-secretase was identified as the membrane-anchored aspartyl protease BACE (or BACE1) and found to be elevated in brain cortex of patients with sporadic Alzheimer's disease. In this review, we summarize current approaches towards the development of BACE inhibitors with focus on bioactive compounds and related patents. Recent reports have described drugs that are effective at inhibiting Abeta production in the brain of transgenic mouse models. The beginning of Phase I clinical trials has been approved for one of them and we can expect that in the near future BACE inhibitors will provide novel effective therapeutics to treat AD.