Inhibition of beta-amyloid(40) fibrillogenesis and disassembly of beta-amyloid(40) fibrils by short beta-amyloid congeners containing N-methyl amino acids at alternate residues.
A potential goal in the prevention or therapy of Alzheimer's disease is to decrease or eliminate neuritic plaques composed of fibrillar beta-amyloid (Abeta). In this paper we describe N-methyl amino acid containing congeners of the hydrophobic "core domain" of Abeta that inhibit the fibrillogenesis of full-length Abeta. These peptides also disassemble preformed fibrils of full-length Abeta. A key feature of the inhibitor peptides is that they contain N-methyl amino acids in alternating positions of the sequence. The most potent of these inhibitors, termed Abeta16-22m, has the sequence NH(2)-K(Me-L)V(Me-F)F(Me-A)E-CONH(2). In contrast, a peptide, NH(2)-KL(Me-V)(Me-F)(Me-F)(Me-A)-E-CONH(2), with N-methyl amino acids in consecutive order, is not a fibrillogenesis inhibitor. Another peptide containing alternating N-methyl amino acids but based on the sequence of a different fibril-forming protein, the human prion protein, is also not an inhibitor of Abeta40 fibrillogenesis. The nonmethylated version of the inhibitor peptide, NH(2)-KLVFFAE-CONH(2) (Abeta16-22), is a weak fibrillogenesis inhibitor. Perhaps contrary to expectations, the Abeta16-22m peptide is highly soluble in aqueous media, and concentrations in excess of 40 mg/mL can be obtained in buffers of physiological pH and ionic strength, compared to only 2 mg/mL for Abeta16-22. Analytical ultracentrifugation demonstrates that Abeta16-22m is monomeric in buffer solution. Whereas Abeta16-22 is susceptible to cleavage by chymotrypsin, the methylated inhibitor peptide Abeta16-22m is completely resistant to this protease. Circular dichroic spectroscopy of Abeta16-22m indicates that this peptide is a beta-strand, albeit with an unusual minimum at 226 nm. In summary, the inhibitor motif is that of alternating N-methyl and nonmethylated amino acids in a sequence critical for Abeta40 fibrillogenesis. These inhibitors appear to act by binding to growth sites of Abeta nuclei and/or fibrils and preventing the propagation of the network of hydrogen bonds that is essential for the formation of an extended beta-sheet fibril.
Gordon
D J
DJ
Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
Sciarretta
K L
KL
Meredith
S C
SC
D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000138:chemical synthesis / Q000378:metabolism* / Q000648:ultrastructure; D052160:Benzothiazoles; D002918:Chymotrypsin / Q000378:metabolism; D004351:Drug Resistance; D006801:Humans; D008745:Methylation; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000037:antagonists & inhibitors* / Q000138:chemical synthesis / Q000378:metabolism* / Q000648:ultrastructure; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013844:Thiazoles / Q000378:metabolism; D014461:Ultracentrifugation
D000596:Amino Acids; D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D010446:Peptide Fragments; D013844:Thiazoles; C078592:amyloid beta-protein (1-40); C009462:thioflavin T; D002918:Chymotrypsin