Proliferation of amyloid-β42 aggregates occurs through a secondary nucleation mechanism
Edited by William A. Eaton, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, and approved April 12, 2013 (received for review October 22, 2012)
Abstract
The generation of toxic oligomers during the aggregation of the amyloid-β (Aβ) peptide Aβ42 into amyloid fibrils and plaques has emerged as a central feature of the onset and progression of Alzheimer’s disease, but the molecular pathways that control pathological aggregation have proved challenging to identify. Here, we use a combination of kinetic studies, selective radiolabeling experiments, and cell viability assays to detect directly the rates of formation of both fibrils and oligomers and the resulting cytotoxic effects. Our results show that once a small but critical concentration of amyloid fibrils has accumulated, the toxic oligomeric species are predominantly formed from monomeric peptide molecules through a fibril-catalyzed secondary nucleation reaction, rather than through a classical mechanism of homogeneous primary nucleation. This catalytic mechanism couples together the growth of insoluble amyloid fibrils and the generation of diffusible oligomeric aggregates that are implicated as neurotoxic agents in Alzheimer’s disease. These results reveal that the aggregation of Aβ42 is promoted by a positive feedback loop that originates from the interactions between the monomeric and fibrillar forms of this peptide. Our findings bring together the main molecular species implicated in the Aβ aggregation cascade and suggest that perturbation of the secondary nucleation pathway identified in this study could be an effective strategy to control the proliferation of neurotoxic Aβ42 oligomers.
Acknowledgments
We thank Dale Schenk, Daan Frenkel, and David Chandler for useful discussions. We acknowledge financial support from the Newman Foundation (T.P.J.K.), the Schiff Foundation (S.I.A.C.), the Kennedy Memorial Trust (S.I.A.C.), the Swedish Research Council (S.L.) and its Linneaus Centre Organizing Molecular Matter (S.L. and E.H.), the Crafoord Foundation (S.L.), the Royal Physiographic Society (E.H.), the Nanometer Structure Consortium at Lund University (S.L.), Alzheimerfonden (S.L.), Danish Research Foundation (D.E.O.), and the Wellcome Trust (M.V., C.M.D., and T.P.J.K.).
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Published online: May 23, 2013
Published in issue: June 11, 2013
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Acknowledgments
We thank Dale Schenk, Daan Frenkel, and David Chandler for useful discussions. We acknowledge financial support from the Newman Foundation (T.P.J.K.), the Schiff Foundation (S.I.A.C.), the Kennedy Memorial Trust (S.I.A.C.), the Swedish Research Council (S.L.) and its Linneaus Centre Organizing Molecular Matter (S.L. and E.H.), the Crafoord Foundation (S.L.), the Royal Physiographic Society (E.H.), the Nanometer Structure Consortium at Lund University (S.L.), Alzheimerfonden (S.L.), Danish Research Foundation (D.E.O.), and the Wellcome Trust (M.V., C.M.D., and T.P.J.K.).
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*This Direct Submission article had a prearranged editor.
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The authors declare no conflict of interest.
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Proliferation of amyloid-β42 aggregates occurs through a secondary nucleation mechanism, Proc. Natl. Acad. Sci. U.S.A.
110 (24) 9758-9763,
https://doi.org/10.1073/pnas.1218402110
(2013).
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