Reversal of temperature-induced conformational changes in the amyloid-beta peptide, Abeta40, by the beta-sheet breaker peptides 16-23 and 17-24.
OBJECTIVE
Aggregates of the protein amyloid-beta (Abeta) play a crucial role in the pathogenesis of Alzheimer's disease (AD). Most therapeutic approaches to AD do not target Abeta, so determination of the factor(s) that facilitate aggregation and discovering agents that prevent aggregation have great potential therapeutic value.


METHODS
We investigated ex vivo the temperature-sensitive regions of Abeta1-40 (Abeta40) and their interactions with octapeptides derived from sequences within Abeta40 -beta-sheet breaker peptides (betaSBP) - 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 Abeta40.


RESULTS
Temperature-dependent conformational changes were observed in Abeta40 at epitopes 9-14 and 17-21 at 36-38 and 36-40 degrees C respectively. The betaSBPs 16-23 and 17-24, but not 15-22 and 18-25, could inhibit the changes. Moreover, betaSBPs 16-23 and 17-24 increased digestion of Abeta40 by protease K, indicating a decreased aggregation of Abeta40, whereas betaSBPs 15-22 and 18-25 did not increase this digestion. CD spectra revealed that beta-sheet formation in Abeta40 at 38 degrees C was reduced with betaSBPs 16-23 and 17-24.


CONCLUSIONS
The epitopes 9-14 and 17-21 are the temperature-sensitive regions within Abeta40. The betaSBPs, Abeta16-23 and 17-24 reversed temperature-induced beta-sheet formation, and decreased Abeta40 aggregation. The results suggest that the 17-23 epitope of Abeta40 is crucially involved in preventing Abeta40 aggregation and consequent deposition of Abeta40 in AD brain.
Department of Pharmacology, Division of Internal Medicine, Faculty of Medicine, Pamukkale University, Kinikli Campus, Denizli, Turkey.
Funda F Bölükbaşi
FF
Hatip
Midori
M
Suenaga
Tatsuo
T
Yamada
Yoichi
Y
Matsunaga
D000544:Alzheimer Disease / Q000378:metabolism; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D019286:Endopeptidase K / Q000378:metabolism; D000939:Epitopes / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation / Q000528:radiation effects*; D017433:Protein Structure, Secondary; D013696:Temperature; D013997:Time Factors
D016229:Amyloid beta-Peptides; D000939:Epitopes; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); D019286:Endopeptidase K