Dataset Information

Self-Assembly of A?40, A?42 and A?43 Peptides in Aqueous Mixtures of Fluorinated Alcohols.

ABSTRACT: Fluorinated alcohols such as hexafluoroisopropanol (HFIP) and trifluoroethanol (TFE) have the ability to promote ?-helix and ?-hairpin structure in proteins and peptides. HFIP has been used extensively to dissolve various amyloidogenic proteins and peptides including A?, in order to ensure their monomeric status. In this paper, we have investigated the self-assembly of A?40, A?42, and A?43 in aqueous mixtures of fluorinated alcohols from freshly dissolved stock solutions in HFIP. We have observed that formation of fibrillar and non-fibrillar structures are dependent on the solvent composition. Peptides form fibrils with ease when reconstituted in deionized water from freshly dissolved HFIP stocks. In aqueous mixtures of fluorinated alcohols, either predominant fibrillar structures or clustered aggregates were observed. Aqueous mixtures of 20% HFIP are more favourable for A? fibril formation as compared to 20% TFE. When A?40, A?42, and A?43 stocks in HFIP are diluted in 50% aqueous mixtures in phosphate buffer or deionized water followed by slow evaporation of HFIP, A? peptides form fibrils in phosphate buffer and deionized water. The clustered structures could be off-pathway aggregates. A?40, A?42, and A?43 showed significant ?-helical content in freshly dissolved HFIP stocks. The ?-helical conformational intermediate in A?40, A?42, and A?43 could favour the formation of both fibrillar and non-fibrillar aggregates depending on solvent conditions and rate of ?-helical to ?-sheet transition.

SUBMITTER: Pachahara SK

PROVIDER: S-EPMC4550328 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Self-Assembly of Aβ40, Aβ42 and Aβ43 Peptides in Aqueous Mixtures of Fluorinated Alcohols.

Pachahara Sanjai Kumar SK Adicherla Harikrishna H Nagaraj Ramakrishnan R

PloS one 20150826 8

Fluorinated alcohols such as hexafluoroisopropanol (HFIP) and trifluoroethanol (TFE) have the ability to promote α-helix and β-hairpin structure in proteins and peptides. HFIP has been used extensively to dissolve various amyloidogenic proteins and peptides including Aβ, in order to ensure their monomeric status. In this paper, we have investigated the self-assembly of Aβ40, Aβ42, and Aβ43 in aqueous mixtures of fluorinated alcohols from freshly dissolved stock solutions in HFIP. We have observe ...[more]

PMID: 26308214

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Project description:BackgroundCathepsin D (CatD) is a lysosomal protease that degrades both the amyloid β-protein (Aβ) and the microtubule-associated protein, tau, and has been genetically linked to late-onset Alzheimer disease (AD). Here, we sought to examine the consequences of genetic deletion of CatD on Aβ proteostasis in vivo and to more completely characterize the degradation of Aβ42 and Aβ40 by CatD.MethodsWe quantified Aβ degradation rates and levels of endogenous Aβ42 and Aβ40 in the brains of CatD-null (CatD-KO), heterozygous null (CatD-HET), and wild-type (WT) control mice. CatD-KO mice die by ~ 4 weeks of age, so tissues from younger mice, as well as embryonic neuronal cultures, were investigated. Enzymological assays and surface plasmon resonance were employed to quantify the kinetic parameters (KM, kcat) of CatD-mediated degradation of monomeric human Aβ42 vs. Aβ40, and the degradation of aggregated Aβ42 species was also characterized. Competitive inhibition assays were used to interrogate the relative inhibition of full-length human and mouse Aβ42 and Aβ40, as well as corresponding p3 fragments.ResultsGenetic deletion of CatD resulted in 3- to 4-fold increases in insoluble, endogenous cerebral Aβ42 and Aβ40, exceeding the increases produced by deletion of an insulin-degrading enzyme, neprilysin or both, together with readily detectable intralysosomal deposits of endogenous Aβ42-all by 3 weeks of age. Quite significantly, CatD-KO mice exhibited ~ 30% increases in Aβ42/40 ratios, comparable to those induced by presenilin mutations. Mechanistically, the perturbed Aβ42/40 ratios were attributable to pronounced differences in the kinetics of degradation of Aβ42 vis-à-vis Aβ40. Specifically, Aβ42 shows a low-nanomolar affinity for CatD, along with an exceptionally slow turnover rate that, together, renders Aβ42 a highly potent competitive inhibitor of CatD. Notably, the marked differences in the processing of Aβ42 vs. Aβ40 also extend to p3 fragments ending at positions 42 vs. 40.ConclusionsOur findings identify CatD as the principal intracellular Aβ-degrading protease identified to date, one that regulates Aβ42/40 ratios via differential degradation of Aβ42 vs. Aβ40. The finding that Aβ42 is a potent competitive inhibitor of CatD suggests a possible mechanistic link between elevations in Aβ42 and downstream pathological sequelae in AD.

Dataset Information

Self-Assembly of A?40, A?42 and A?43 Peptides in Aqueous Mixtures of Fluorinated Alcohols.

Publications

Self-Assembly of Aβ40, Aβ42 and Aβ43 Peptides in Aqueous Mixtures of Fluorinated Alcohols.

Similar Datasets

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