Stability of the transthyretin molecule as a key factor in the interaction with a-beta peptide--relevance in Alzheimer's disease

PLoS One. 2012;7(9):e45368. doi: 10.1371/journal.pone.0045368. Epub 2012 Sep 17.

Abstract

Transthyretin (TTR) protects against A-Beta toxicity by binding the peptide thus inhibiting its aggregation. Previous work showed different TTR mutations interact differently with A-Beta, with increasing affinities correlating with decreasing amyloidogenecity of the TTR mutant; this did not impact on the levels of inhibition of A-Beta aggregation, as assessed by transmission electron microscopy. Our work aimed at probing differences in binding to A-Beta by WT, T119M and L55P TTR using quantitative assays, and at identifying factors affecting this interaction. We addressed the impact of such factors in TTR ability to degrade A-Beta. Using a dot blot approach with the anti-oligomeric antibody A11, we showed that A-Beta formed oligomers transiently, indicating aggregation and fibril formation, whereas in the presence of WT and T119M TTR the oligomers persisted longer, indicative that these variants avoided further aggregation into fibrils. In contrast, L55PTTR was not able to inhibit oligomerization or to prevent evolution to aggregates and fibrils. Furthermore, apoptosis assessment showed WT and T119M TTR were able to protect against A-Beta toxicity. Because the amyloidogenic potential of TTR is inversely correlated with its stability, the use of drugs able to stabilize TTR tetrameric fold could result in increased TTR/A-Beta binding. Here we showed that iododiflunisal, 3-dinitrophenol, resveratrol, [2-(3,5-dichlorophenyl)amino] (DCPA) and [4-(3,5-difluorophenyl)] (DFPB) were able to increase TTR binding to A-Beta; however only DCPA and DFPB improved TTR proteolytic activity. Thyroxine, a TTR ligand, did not influence TTR/A-Beta interaction and A-Beta degradation by TTR, whereas RBP, another TTR ligand, not only obstructed the interaction but also inhibited TTR proteolytic activity. Our results showed differences between WT and T119M TTR, and L55PTTR mutant regarding their interaction with A-Beta and prompt the stability of TTR as a key factor in this interaction, which may be relevant in AD pathogenesis and for the design of therapeutic TTR-based therapies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / metabolism*
  • Amyloid beta-Protein Precursor / genetics
  • Amyloid beta-Protein Precursor / metabolism*
  • Cell Line, Tumor
  • Diflunisal / analogs & derivatives
  • Diflunisal / pharmacology
  • Dinitrophenols / pharmacology
  • Humans
  • Mutation
  • Phthalic Acids / pharmacology
  • Prealbumin / genetics
  • Prealbumin / metabolism*
  • Protein Binding / drug effects
  • Resveratrol
  • Stilbenes / pharmacology

Substances

  • Amyloid beta-Protein Precursor
  • Dinitrophenols
  • Phthalic Acids
  • Prealbumin
  • Stilbenes
  • iododiflunisal
  • dimethyl 2,3,5,6-tetrachloroterephthalate
  • Diflunisal
  • Resveratrol

Grants and funding

This work is funded by FEDER funds through the Operational Competitiveness Programme COMPETE, by POCI 2010 (Programa Operacional Ciência e Inovação 2010) and by national funds through FCT Fundação para a Ciência e a Tecnologia under the projects FCOMP-01-0124-FEDER-022718 (PEst-C/SAU/LA0002/2011), and PTDC/SAU-NEU/64593/2006. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.