Inhibition of toxicity in the beta-amyloid peptide fragment beta -(25-35) using N-methylated derivatives: a general strategy to prevent amyloid formation

• Published in: The Journal of biological chemistry 2000-08, Vol.275 (33), p.25109-25115
• Main Authors: Hughes, E, Burke, R M, Doig, A J
• Format: Article
• Language: English
• Subjects: Amyloid beta-Peptides - antagonists & inhibitors; Amyloid beta-Peptides - chemistry; Amyloid beta-Peptides - pharmacology; Amyloid beta-Peptides - toxicity; Animals; Benzothiazoles; Cell Death - drug effects; Coloring Agents - pharmacology; Congo Red - pharmacology; Dose-Response Relationship, Drug; Fluorescent Dyes - pharmacology; Methylation; Microscopy, Electron; PC12 Cells; Peptide Biosynthesis; Peptide Fragments - chemistry; Peptide Fragments - pharmacology; Peptide Fragments - toxicity; Protein Binding - drug effects; Protein Conformation - drug effects; Protein Folding; Protein Structure, Secondary - drug effects; Rats; Spectrophotometry; Tetrazolium Salts - pharmacology; Thiazoles - pharmacology
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M003554200

beta-(25-35) is a synthetic derivative of beta-amyloid, the peptide that is believed to cause Alzheimer's disease. As it is highly toxic and forms fibrillar aggregates typical of beta-amyloid, it is suitable as a model for testing inhibitors of aggregation and toxicity. We demonstrate that N-methylated derivatives of beta-(25-35), which in isolation are soluble and non-toxic, can prevent the aggregation and inhibit the resulting toxicity of the wild type peptide. N-Methylation can block hydrogen bonding on the outer edge of the assembling amyloid. The peptides are assayed by Congo red and thioflavin T binding, electron microscopy, and a 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) toxicity assay on PC12 cells. One peptide (Gly(25) N-methylated) has properties similar to the wild type, whereas five have varying effects on prefolded fibrils and fibril assembly. In particular, beta-(25-35) with Gly(33) N-methylated is able to completely prevent fibril assembly and to reduce the toxicity of prefolded amyloid. With Leu(34) N-methylated, the fibril morphology is altered and the toxicity reduced. We suggest that the use of N-methylated derivatives of amyloidogenic peptides and proteins could provide a general solution to the problem of amyloid deposition and toxicity.