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Intrinsic structural heterogeneity and long-term maturation of amyloid ? peptide fibrils.

ABSTRACT: Amyloid ? peptides form fibrils that are commonly assumed to have a dry, homogeneous, and static internal structure. To examine these assumptions, fibrils under various conditions and different ages have been examined with multidimensional infrared spectroscopy. Each peptide in the fibril had a ¹³C?¹?O label in the backbone of one residue to disinguish the amide I' absorption due to that residue from the amide I' absorption of other residues. Fibrils examined soon after they formed, and reexamined after 1 year in the dry state, exhibited spectral changes confirming that structurally significant water molecules were present in the freshly formed fibrils. Results from fibrils incubated in solution for 4 years indicate that water molecules remained trapped within fibrils and mobile over the 4 year time span. These water molecules are structurally significant because they perturb the parallel ?-sheet hydrogen bonding pattern at frequent intervals and at multiple points within individual fibrils, creating structural heterogeneity along the length of a fibril. These results show that the interface between ?-sheets in an amyloid fibril is not a "dry zipper", and that the internal structure of a fibril evolves while it remains in a fibrillar state. These features, water trapping, structural heterogeneity, and structural evolution within a fibril over time, must be accommodated in models of amyloid fibril structure and formation.

SUBMITTER: Ma J

PROVIDER: S-EPMC3750686 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Intrinsic structural heterogeneity and long-term maturation of amyloid β peptide fibrils.

Ma Jianqiang J Komatsu Hiroaki H Kim Yung Sam YS Liu Liu L Hochstrasser Robin M RM Axelsen Paul H PH

ACS chemical neuroscience 20130612 8

Amyloid β peptides form fibrils that are commonly assumed to have a dry, homogeneous, and static internal structure. To examine these assumptions, fibrils under various conditions and different ages have been examined with multidimensional infrared spectroscopy. Each peptide in the fibril had a ¹³C═¹⁸O label in the backbone of one residue to disinguish the amide I' absorption due to that residue from the amide I' absorption of other residues. Fibrils examined soon after they formed, and reexamin ...[more]

PMID: 23701594

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Project description:The misfolding and aggregation of amyloid-? (A?) peptides into amyloid fibrils is regarded as one of the causative events in the pathogenesis of Alzheimer's disease (AD). Tanshinones extracted from Chinese herb Danshen (Salvia Miltiorrhiza Bunge) were traditionally used as anti-inflammation and cerebrovascular drugs due to their antioxidation and antiacetylcholinesterase effects. A number of studies have suggested that tanshinones could protect neuronal cells. In this work, we examine the inhibitory activity of tanshinone I (TS1) and tanshinone IIA (TS2), the two major components in the Danshen herb, on the aggregation and toxicity of A?1-42 using atomic force microscopy (AFM), thioflavin-T (ThT) fluorescence assay, cell viability assay, and molecular dynamics (MD) simulations. AFM and ThT results show that both TS1 and TS2 exhibit different inhibitory abilities to prevent unseeded amyloid fibril formation and to disaggregate preformed amyloid fibrils, in which TS1 shows better inhibitory potency than TS2. Live/dead assay further confirms that introduction of a very small amount of tanshinones enables protection of cultured SH-SY5Y cells against A?-induced cell toxicity. Comparative MD simulation results reveal a general tanshinone binding mode to prevent A? peptide association, showing that both TS1 and TS2 preferentially bind to a hydrophobic ?-sheet groove formed by the C-terminal residues of I31-M35 and M35-V39 and several aromatic residues. Meanwhile, the differences in binding distribution, residues, sites, population, and affinity between TS1-A? and TS2-A? systems also interpret different inhibitory effects on A? aggregation as observed by in vitro experiments. More importantly, due to nonspecific binding mode of tanshinones, it is expected that tanshinones would have a general inhibitory efficacy of a wide range of amyloid peptides. These findings suggest that tanshinones, particularly TS1 compound, offer promising lead compounds with dual protective role in anti-inflammation and antiaggregation for further development of A? inhibitors to prevent and disaggregate amyloid formation.

Dataset Information

Intrinsic structural heterogeneity and long-term maturation of amyloid ? peptide fibrils.

Publications

Intrinsic structural heterogeneity and long-term maturation of amyloid β peptide fibrils.

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