Inhibition of toxicity in the beta-amyloid peptide fragment beta -(25-35) using N-methylated derivatives: a general strategy to prevent amyloid formation.
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.
Hughes
E
E
Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, United Kingdom.
Burke
R M
RM
Doig
A J
AJ
D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D000818:Animals; D052160:Benzothiazoles; D016923:Cell Death / Q000187:drug effects; D004396:Coloring Agents / Q000494:pharmacology; D003224:Congo Red / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes / Q000494:pharmacology; D008745:Methylation; D008854:Microscopy, Electron; D016716:PC12 Cells; D010452:Peptide Biosynthesis; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation / Q000187:drug effects; D017510:Protein Folding; D017433:Protein Structure, Secondary / Q000187:drug effects; D051381:Rats; D013053:Spectrophotometry; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D004396:Coloring Agents; D005456:Fluorescent Dyes; D010446:Peptide Fragments; D013778:Tetrazolium Salts; D013844:Thiazoles; C074636:amyloid beta-protein (25-35); C009462:thioflavin T; D003224:Congo Red; C022616:thiazolyl blue