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The binding of apolipoprotein E to oligomers and fibrils of amyloid-? alters the kinetics of amyloid aggregation.

ABSTRACT: Deposition of amyloid-? (A?) in Alzheimer's disease (AD) is strongly correlated with the APOE genotype. However, the role of apolipoprotein E (apoE) in A? aggregation has remained unclear. Here we have used different apoE preparations, such as recombinant protein or protein isolated from cultured astrocytes, to examine the effect of apoE on the aggregation of both A?1-40 and A?1-42. The kinetics of aggregation, measured by the loss of fluorescence of tetramethylrhodamine-labeled A?, is shown to be dramatically slowed by the presence of substoichiometric concentrations of apoE. Using these concentrations, we conclude that apoE binds primarily to and affects the growth of oligomers that lead to the nuclei required for fibril growth. At higher apoE concentrations, the protein also binds to A? fibrils, resulting in fibril stabilization and a slower rate of fibril growth. The aggregation of A?1-40 is dependent on the apoE isoform, being the most dramatic for apoE4 and less so for apoE3 and apoE2. Our results indicate that the detrimental role of apoE4 in AD could be related to apoE-induced stabilization of the soluble but cytotoxic oligomeric forms and intermediates of A?, as well as fibril stabilization.

SUBMITTER: Garai K

PROVIDER: S-EPMC4196732 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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The binding of apolipoprotein E to oligomers and fibrils of amyloid-β alters the kinetics of amyloid aggregation.

Garai Kanchan K Verghese Philip B PB Baban Berevan B Holtzman David M DM Frieden Carl C

Biochemistry 20140925 40

Deposition of amyloid-β (Aβ) in Alzheimer's disease (AD) is strongly correlated with the APOE genotype. However, the role of apolipoprotein E (apoE) in Aβ aggregation has remained unclear. Here we have used different apoE preparations, such as recombinant protein or protein isolated from cultured astrocytes, to examine the effect of apoE on the aggregation of both Aβ1-40 and Aβ1-42. The kinetics of aggregation, measured by the loss of fluorescence of tetramethylrhodamine-labeled Aβ, is shown to ...[more]

PMID: 25207746

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Project description:The misfolding and aggregation of amyloid-β (Aβ) 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 Aβ1-42 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 Aβ-induced cell toxicity. Comparative MD simulation results reveal a general tanshinone binding mode to prevent Aβ peptide association, showing that both TS1 and TS2 preferentially bind to a hydrophobic β-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-Aβ and TS2-Aβ systems also interpret different inhibitory effects on Aβ 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 Aβ inhibitors to prevent and disaggregate amyloid formation.

Dataset Information

The binding of apolipoprotein E to oligomers and fibrils of amyloid-? alters the kinetics of amyloid aggregation.

Publications

The binding of apolipoprotein E to oligomers and fibrils of amyloid-β alters the kinetics of amyloid aggregation.

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