Reversal of temperature-induced conformational changes in the amyloid-beta peptide, Aß40, by the ß-sheet breaker peptides 16-23 and 17-24

Abstract

Background and purpose: Aggregates of the protein amyloid-beta (Aß) play a crucial role in the pathogenesis of Alzheimer's disease (AD). Most therapeutic approaches to AD do not target Aß, so determination of the factor(s) that facilitate aggregation and discovering agents that prevent aggregation have great potential therapeutic value. Experimental approach: We investigated ex vivo the temperature-sensitive regions of Aß1-40 (Aß40) and their interactions with octapeptides derived from sequences within Aß40 - ß-sheet breaker peptides (ßSBP) - using enzyme-linked immunosorbent assay, and dot blot and far-UV circular dichroism (CD) spectroscopy. We measured changes within the physiological limits of temperature, using antibodies targeting epitopes 1-7, 5-10, 9-14 and 17-21 within Aß40. Key results: Temperature-dependent conformational changes were observed in Aß40 at epitopes 9-14 and 17-21 at 36-38 and 36-40°C respectively. The ßSBPs 16-23 and 17-24, but not 15-22 and 18-25, could inhibit the changes. Moreover, ßSBPs 16-23 and 17-24 increased digestion of Aß40 by protease K, indicating a decreased aggregation of Aß40, whereas ßSBPs 15-22 and 18-25 did not increase this digestion. CD spectra revealed that ß-sheet formation in Aß40 at 38°C was reduced with ßSBPs 16-23 and 17-24. Conclusions and implications: The epitopes 9-14 and 17-21 are the temperature-sensitive regions within Aß40. The ßSBPs, Aß16-23 and 17-24 reversed temperature-induced ß-sheet formation, and decreased Aß40 aggregation. The results suggest that the 17-23 epitope of Aß40 is crucially involved in preventing Aß40 aggregation and consequent deposition of Aß40 in AD brain. © 2009 The British Pharmacological Society.