N-Methylated Peptide Inhibitors of β-Amyloid Aggregation and Toxicity. Optimization of the Inhibitor Structure

Abstract

The key pathogenic event in the onset of Alzheimer's disease (AD) is believed to be the aggregation of the beta-amyloid (Abeta) peptide into toxic oligomers. Molecules that interfere with this process may therefore act as therapeutic agents for the treatment of AD. N-Methylated peptides (meptides) are a general class of peptide aggregation inhibitors that act by binding to one face of the aggregating peptide but are unable to hydrogen bond on the other face, because of the N-methyl group replacing a backbone NH group. Here, we optimize the structure of meptide inhibitors of Abeta aggregation, starting with the KLVFF sequence that is known to bind to Abeta. We varied the meptide length, N-methylation sites, acetylation, and amidation of the N and C termini, side-chain identity, and chirality, via five compound libraries. Inhibitor activity was tested by thioflavin T binding, affinity chromatography, electron microscopy, and an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide toxicity assay. We found that inhibitors should have all d chirality, have a free N terminus but an amidated C terminus, and have large, branched hydrophobic side chains at positions 1-4, while the side chain at position 5 was less important. A single N-methyl group was necessary and sufficient. The most active compound, d-[(chGly)-(Tyr)-(chGly)-(chGly)-(mLeu)]-NH(2), was more active than all previously reported peptide inhibitors. Its related non-N-methylated analogues were insoluble and toxic.

Aβ(1-42) Assembly in the Presence of scyllo-Inositol Derivatives: Identification of an Oxime Linkage as Important for the Development of Assembly Inhibitors

“…1,4,28 We identified compounds 5,6,8,11,16, and 17 as potential compounds for further development; we therefore examined the compound and the compound Aβ(1-42)-induced toxicity of SH-SY5Y cells in culture (Figure 7). Of the aminelinked derivatives, only 1-deoxy-1-azide-scyllo-inositol (16) rescued Aβ(1-42)-induced toxicity ( Figure 7A), whereas derivative 17 alone induced as much toxicity as Aβ alone ( Figure 7B). Of the oxime-linked derivatives, only the phenyloxime (5) derivative rescued Aβ(1-42)-induced toxicity ( Figure 7C) while the remaining compounds had no effect on toxicity.…”

Targeting the cyclin-binding groove site to inhibit the catalytic activity of CDK2/cyclin A complex using p27KIP1-derived peptidomimetic inhibitors

“…Nmethylation has increased the flexibility of the peptide to interact with the binding site [31,10]. The N-methylation of hydrophobic amino acid residue decreases the bulkiness of peptides and improves the cell permeability to cross over the lipophilic cell membranes [22,49]. Halogenation improves the penetration ability of the aromatic substituent [16].…”

Small molecule inhibitors of Aβ‐aggregation and neurotoxicity

“…Peptide N-methylation has also emerged as a powerful tool for inhibition of Ab and a mechanism to improve peptide half life in vivo [Bodles et al, 2004;Gordon and Meredith, 2003;Gordon et al, 2001;Hughes et al, 2000;Kapurniotu et al, 2002;Kokkoni et al, 2006;Yan et al, 2006]. N-methylation is known to lock the residues into a b conformation [Manavalan and Momany, 1980], generating soluble monomeric b-sheet peptides [Doig et al, 1997].…”