Article

# Amyloid-β protein oligomerization and the importance of tetramers and dodecamers in the aetiology of Alzheimer's disease.

[more]
Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106-9510, USA.
(Impact Factor: 23.3). 07/2009; 1(4):326-31. DOI: 10.1038/nchem.247
Source: PubMed

ABSTRACT In recent years, small protein oligomers have been implicated in the aetiology of a number of important amyloid diseases, such as type 2 diabetes, Parkinson's disease and Alzheimer's disease. As a consequence, research efforts are being directed away from traditional targets, such as amyloid plaques, and towards characterization of early oligomer states. Here we present a new analysis method, ion mobility coupled with mass spectrometry, for this challenging problem, which allows determination of in vitro oligomer distributions and the qualitative structure of each of the aggregates. We applied these methods to a number of the amyloid-β protein isoforms of Aβ40 and Aβ42 and showed that their oligomer-size distributions are very different. Our results are consistent with previous observations that Aβ40 and Aβ42 self-assemble via different pathways and provide a candidate in the Aβ42 dodecamer for the primary toxic species in Alzheimer's disease.

### Full-text

Available from: Joan Shea, Jun 30, 2015
0 Followers
·
149 Views
• Source
##### Article: Separation of glycosidic catiomers by TWIM-MS using CO2 as a drift gas
[Hide abstract]
ABSTRACT: Traveling wave ion mobility mass spectrometry (TWIM-MS) is shown to be able to separate and characterize several isomeric forms of diterpene glycosides stevioside (Stv) and rebaudioside A (RebA) that are cationized by Na(+) and K(+) at different sites. Determination and characterization of these coexisting isomeric species, herein termed catiomers, arising from cationization at different and highly competitive coordinating sites, is particularly challenging for glycosides. To achieve this goal, the advantage of using CO2 as a more massive and polarizable drift gas, over N2 , was demonstrated. Post-TWIM-MS/MS experiments were used to confirm the separation. Optimization of the possible geometries and cross-sectional calculations for mobility peak assignments were also performed. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
Journal of Mass Spectrometry 02/2015; 50(2). DOI:10.1002/jms.3532 · 2.71 Impact Factor
• Source
##### Article: Crucial role of non-specific interactions in amyloid nucleation
[Hide abstract]
ABSTRACT: Protein oligomers have been implicated as toxic agents in a wide range of amyloid-related diseases. Yet it has remained unsolved whether the oligomers are a necessary step in the formation of amyloid fibrils, or just a dangerous by-product. Analogously, it has not been resolved if the amyloid nucleation process is a classical one-step nucleation process, or a two-step process involving pre-nucleation clusters. We use coarse-grained computer simulations to study the effect of non-specific attractions between peptides on the primary nucleation process underlying amyloid fibrillization. We find that for peptides that do not attract, the classical one-step nucleation mechanism is possible, but only at non-physiologically high peptide concentrations. At low peptide concentrations, which mimic the physiologically relevant regime, attractive inter-peptide interactions are essential for fibril formation. Nucleation then inevitably takes place through a two-step mechanism involving prefibrillar oligomers. We show that oligomers not only help peptides meet each other, but create an environment that facilitates the conversion of monomers into the $\beta$-sheet rich form characteristic of fibrils. Nucleation typically does not proceed via the most prevalent oligomers, but via an oligomer size that is only observed in rare fluctuations, which is why such aggregates might be hard to capture experimentally. Finally, we find that the nucleation of amyloid fibrils cannot be described by classical nucleation theory: in the two-step mechanism the critical nucleus size increases both with an increase in concentration and in the inter-peptide interactions, in direct contrast with predictions from classical nucleation theory.
Proceedings of the National Academy of Sciences 12/2014; 111(50). DOI:10.1073/pnas.1410159111 · 9.81 Impact Factor
• Source
##### Article: Protein Misfolded Oligomers: Experimental Approaches, Mechanism of Formation, and Structure-Toxicity Relationships
[Hide abstract]
ABSTRACT: The conversion of proteins from their native state to misfolded oligomers is associated with, and thought to be the cause of, a number of human diseases, including Alzheimer's disease, Parkinson's disease, and systemic amyloidoses. The study of the structure, mechanism of formation, and biological activity of protein misfolded oligomers has been challenged by the metastability, transient formation, and structural heterogeneity of such species. In spite of these difficulties, in the past few years, many experimental approaches have emerged that enable the detection and the detailed molecular study of misfolded oligomers. In this review, we describe the basic and generic knowledge achieved on protein oligomers, describing the mechanisms of oligomer formation, the methodologies used thus far for their structural determination, and the structural elements responsible for their toxicity.
Chemistry & biology 03/2012; 19(3):315-27. DOI:10.1016/j.chembiol.2012.02.003 · 6.59 Impact Factor