Direct observation of Abeta amyloid fibril growth and inhibition.
Amyloid fibril formation is a phenomenon common to many proteins and peptides, including amyloid beta (Abeta) peptide associated with Alzheimer's disease. To clarify the mechanism of fibril formation and to create inhibitors, real-time monitoring of fibril growth is essential. Here, seed-dependent amyloid fibril growth of Abeta(1-40) was visualized in real-time at the single fibril level using total internal reflection fluorescence microscopy (TIRFM) combined with the binding of thioflavin T, an amyloid-specific fluorescence dye. The clear image and remarkable length of the fibrils enabled an exact analysis of the rate of growth of individual fibrils, indicating that the fibril growth was a highly cooperative process extending the fibril ends at a constant rate. It has been known that Abeta amyloid formation is a stereospecific reaction and the stability is affected by l/d-amino acid replacement. Focusing on these aspects, we designed several analogues of Abeta(25-35), a cytotoxic fragment of Abeta(1-40), consisting of l and d-amino acid residues, and examined their inhibitory effects by TIRFM. Some chimeric Abeta(25-35) peptides inhibited the fibril growth of Abeta(25-35) strongly, although they could not inhibit the growth of Abeta(1-40). The results suggest that a more rational design of stereospecific inhibitors, combined with real-time monitoring of fibril growth, will be useful to invent a potent inhibitor preventing the amyloid fibril growth of Abeta(1-40) and other proteins.
Ban
Tadato
T
Institute for Protein Research, Osaka University and CREST, Japan Science and Technology Agency, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
Hoshino
Masaru
M
Takahashi
Satoshi
S
Hamada
Daizo
D
Hasegawa
Kazuhiro
K
Naiki
Hironobu
H
Goto
Yuji
Y
D002942:Circular Dichroism; D007700:Kinetics; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D017510:Protein Folding; D000685:Serum Amyloid A Protein / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000648:ultrastructure
D000685:Serum Amyloid A Protein