Inhibition of toxicity and protofibril formation in the amyloid-beta peptide beta(25-35) using N-methylated derivatives.
Beta (25-35) is a fragment of beta-amyloid that retains its wild-type properties. N-methylated derivatives of beta(25-35) can block hydrogen bonding on the outer edge of the assembling amyloid, so preventing the aggregation and inhibiting the toxicity of the wild-type peptide. The effects are assayed by Congo Red and thioflavin T binding, electron microscopy and an MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] toxicity assay. N-methyl-Gly-25 has similar properties to the wild- type, while five other methylation sites have varying effects on prefolded fibrils and fibril assembly. In particular, N-methyl-Gly-33 is able to completely prevent fibril assembly and reduces the toxicity of prefolded amyloid. With N-methyl-Leu-34 the fibril morphology is altered and toxicity reduced. A preliminary study of beta(25-35) structure in aqueous solution was made by small-angle neutron scattering (SANS). The protofibrillar aggregates are best described as a disc of radius 140 A and height 53 A (1 A = 0.1 nm), though the possibility of polydisperse aggregates cannot be ruled out. No aggregates form in the presence of N-methyl-Gly-33. 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 and that SANS is an important technique for the direct observation of protofibril formation and destruction in solution.
Doig
A J
AJ
Department of Biomolecular Sciences, UMIST, P.O. Box 88, Manchester M60 1QD, UK. Andrew.Doig@umist.ac.uk
Hughes
E
E
Burke
R M
RM
Su
T J
TJ
Heenan
R K
RK
Lu
J
J
D000544:Alzheimer Disease / Q000188:drug therapy*; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000633:toxicity*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D008745:Methylation; D016716:PC12 Cells; D010446:Peptide Fragments / Q000037:antagonists & inhibitors* / Q000627:therapeutic use* / Q000633:toxicity*; D051381:Rats
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C074636:amyloid beta-protein (25-35)