Influence of Residue 22 on the Folding, Aggregation Profile, and Toxicity of the Alzheimer's Amyloid β Peptide |
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Authors: | Alex Perálvarez-Marín Laura Mateos Shalini Singh Neus Visa Astrid Gräslund |
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Affiliation: | † Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden ‡ Department of Molecular Biology and Functional Genomics, Stockholm University, Stockholm, Sweden § Department of Neurobiology, Care Sciences and Society, Karolinska Institutet-Alzheimer's Disease Research Center, Novum, Stockholm, Sweden ¶ Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden |
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Abstract: | Several biophysical techniques have been used to determine differences in the aggregation profile (i.e., the secondary structure, aggregation propensity, dynamics, and morphology of amyloid structures) and the effects on cell viability of three variants of the amyloid β peptide involved in Alzheimer's disease. We focused our study on the Glu22 residue, comparing the effects of freshly prepared samples and samples aged for at least 20 days. In the aged samples, a high propensity for aggregation and β-sheet secondary structure appears when residue 22 is capable of establishing polar (Glu22 in wild-type) or hydrophobic (Val22 in E22V) interactions. The Arctic variant (E22G) presents a mixture of mostly disordered and α-helix structures (with low β-sheet contribution). Analysis of transmission electron micrographs and atomic force microscopy images of the peptide variants after aging showed significant quantitative and qualitative differences in the morphology of the formed aggregates. The effect on human neuroblastoma cells of these Aβ12-28 variants does not correlate with the amount of β-sheet of the aggregates. In samples allowed to age, the native sequence was found to have an insignificant effect on cell viability, whereas the Arctic variant (E22G), the E22V variant, and the slightly-aggregating control (F19G-F20G) had more prominent effects. |
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Keywords: | AFM atomic force microscopy AD Alzheimer's disease Aβ amyloid β peptide CD circular dichroism FAD familial Alzheimer's disease FTIR Fourier transform infrared MTSSL (1-oxyl-2 2 5 5-tetramethyl-pyrroline-3-methyl) methanethiosulfonate spin label MTT (3-(4 5-dimethylthiazol-2-yl)-2 5-diphenyltetrazolium bromide) ppII polyproline II SDSL-EPR site-directed spin-labeled electron paramagnetic resonance TEM transmission electron microscopy WT wild-type |
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