Structural characterization of a soluble amyloid beta-peptide oligomer.
ABSTRACT Alzheimer's disease (AD) is a neurodegenerative disorder that is linked to the presence of amyloid beta-peptides that can form insoluble fibrils or soluble oligomeric assemblies. Soluble forms are present in the brains and tissues of Alzheimer's patients, and their presence correlates with disease progression. Long-lived soluble forms can be generated in vitro by using small amounts of aliphatic hydrocarbon chains of detergents or fatty acids in preparations of amyloid beta-peptides. Using NMR, we have characterized soluble oligomers of Abeta preglobulomer and globulomer that are stable and alter synaptic activity. The NMR data indicate that these soluble forms have a mixed parallel and antiparallel beta-sheet structure that is different from fibrils which contain only parallel beta-sheets. Using the structural data, we engineered a disulfide bond into the soluble Abeta globulomer to give a "new" soluble antigen that is stable, homogeneous, and binds with the same affinity to selective antibodies as the parent wt globulomer.
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ABSTRACT: Amyloid refers to insoluble protein aggregates that are responsible for amyloid diseases but are also implicated in important physiological functions (functional amyloids). The widespread presence of protein aggregates but also, in most of the cases, their deleterious effects explain worldwide efforts made to understand their formation, structure and biological functions. We emphasized the role of FTIR and especially ATR-FTIR techniques in amyloid protein and/or peptide studies. The multiple advantages provided by ATR-FTIR allow an almost continuous structural view of protein/peptide conversion during the aggregation process. Moreover, it is now well-established that infrared can differentiate oligomers from fibrils simply on their spectral features. ATR-FTIR is certainly the fastest and easiest method to obtain this information. ATR-FTIR occupies a key position in the analysis and comprehension of the complex aggregation mechanism(s) at the oligomer and/or fibril level. These mechanism(s) seem to present strong similarities between different amyloid proteins and might therefore be extremely important to understand for both disease-associated and functional amyloid proteins. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.Biochimica et Biophysica Acta 06/2013; · 4.66 Impact Factor
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ABSTRACT: Amyloid β (Aβ) peptides and metal ions have been associated with the pathogenesis of Alzheimer's disease. The conformational space of Aβ fragments of different length with and without binding of metal ions has been extensively investigated by replica-exchange molecular dynamics (REMD) simulation. However, only trajectories extracted at relatively low temperatures have been used for this analysis. The capability of REMD simulations to characterize the internal dynamics of such intrinsically disordered proteins (IDPs) as Aβ has been overlooked. In this work, we use an approach recently developed by Xue and Skrynnikov (J Am Chem Soc 133:14614-14628, 2011) to calculate NMR observables, including (15)N relaxation rates and (15)N-(1)H nuclear Overhauser enhancement (NOE), from the high-temperature trajectory of REMD simulations for zinc-bound Aβ peptides. The time axis of the trajectory was rescaled to correct for the effect of the high temperature (408 K) compared with the experimental temperature (278 K). Near-quantitative agreement between simulated values and experimental results was obtained. When the structural properties and free-energy surfaces of zinc-bound Aβ(1-40) and Aβ(1-42) were compared at the physiological temperature 310 K it was found that zinc-bound Aβ(1-42) was more rigid than Aβ(1-40) at the C terminus, and its conformational transitions were also more preferred. The self-consistent results derived from trajectories at high and low temperatures demonstrate the capability of REMD simulations to capture the internal dynamics of IDPs.Biophysics of Structure and Mechanism 05/2013; · 2.44 Impact Factor
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ABSTRACT: This work builds upon our findings that proteins secreted by hESCs exhibit pro-regenerative activity, and determines that hESC-conditioned medium robustly enhances the proliferation of both muscle and neural progenitor cells. Importantly, this work establishes that it is the proteins that bind heparin which are responsible for the pro-myogenic effects of hESC-conditioned medium, and indicates that this strategy is suitable for enriching the potentially therapeutic factors. Additionally, this work shows that hESC-secreted proteins act independently of the mitogen FGF-2, and suggests that FGF-2 is unlikely to be a pro-aging molecule in the physiological decline of old muscle repair. Moreover, hESC-secreted factors improve the viability of human cortical neurons in an Alzheimer's disease (AD) model, suggesting that these factors can enhance the maintenance and regeneration of multiple tissues in the aging body.Aging 05/2013; 5(5):357-72. · 4.70 Impact Factor