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J Biol Chem. 2014 Nov 7;289(45):31066-76. doi: 10.1074/jbc.M114.595124. Epub 2014 Sep 12.

Interaction of the molecular chaperone DNAJB6 with growing amyloid-beta 42 (Aβ42) aggregates leads to sub-stoichiometric inhibition of amyloid formation.

Author information

1
From the Department of Biochemistry & Structural Biology, Center for Molecular Protein Science, Lund University, PO box 124, 221 00 Lund, Sweden.
2
Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, Cambridge, United Kingdom.
3
Department of Cell Biology, UMCG and RuG, Groningen, The Netherlands, Department of Biochemistry, Faculty of Pharmacy, Beni-Suef University, Salah Salem Street, 62511 Beni-Suef, Egypt, and.
4
Department of Cell Biology, UMCG and RuG, Groningen, The Netherlands.
5
Department of Biochemistry, Faculty of Pharmacy, Beni-Suef University, Salah Salem Street, 62511 Beni-Suef, Egypt, and.
6
Department of Biomolecular Chemistry, Radboud University Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
7
From the Department of Biochemistry & Structural Biology, Center for Molecular Protein Science, Lund University, PO box 124, 221 00 Lund, Sweden, cecilia.emanuelsson@biochemistry.lu.se.

Abstract

The human molecular chaperone protein DNAJB6 was recently found to inhibit the formation of amyloid fibrils from polyglutamine peptides associated with neurodegenerative disorders such as Huntington disease. We show in the present study that DNAJB6 also inhibits amyloid formation by an even more aggregation-prone peptide (the amyloid-beta peptide, Aβ42, implicated in Alzheimer disease) in a highly efficient manner. By monitoring fibril formation using Thioflavin T fluorescence and far-UV CD spectroscopy, we have found that the aggregation of Aβ42 is retarded by DNAJB6 in a concentration-dependent manner, extending to very low sub-stoichiometric molar ratios of chaperone to peptide. Quantitative kinetic analysis and immunochemistry studies suggest that the high inhibitory efficiency is due to the interactions of the chaperone with aggregated forms of Aβ42 rather than the monomeric form of the peptide. This interaction prevents the growth of such species to longer fibrils and inhibits the formation of new amyloid fibrils through both primary and secondary nucleation. A low dissociation rate of DNAJB6 from Aβ42 aggregates leads to its incorporation into growing fibrils and hence to its gradual depletion from solution with time. When DNAJB6 is eventually depleted, fibril proliferation takes place, but the inhibitory activity can be prolonged by introducing DNAJB6 at regular intervals during the aggregation reaction. These results reveal the highly efficacious mode of action of this molecular chaperone against protein aggregation, and demonstrate that the role of molecular chaperones can involve interactions with multiple aggregated species leading to the inhibition of both principal nucleation pathways through which aggregates are able to form.

KEYWORDS:

Aggregation Kinetics; Alzheimer Disease; Amyloid Fibril Formation; Amyloid-beta (Aβ); Chaperone DnaJ (DnaJ); Hsp40; Inhibition Mechanism; Neurodegenerative Disease; Protein Aggregation

PMID:
25217638
PMCID:
PMC4223311
DOI:
10.1074/jbc.M114.595124
[Indexed for MEDLINE]
Free PMC Article

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