cis-γ-Amino-L-proline peptides as chemical probes of amyloidogenic processing in neurons and APP/PS1 mice

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ) peptides, which are a key factor in its pathogenesis. In this study, we present the design and evaluation of cis-γ-amino-L-proline peptides as metabolically stable, cell-penetrating molecules that can modulate amyloidogenic processing. We screened a library of γ-peptides in primary neuronal cultures to determine their effects on endogenous Aβ1-42 production, cytotoxicity, and β-secretase (BACE1)-associated activity. Comparative analysis of structurally related analogues enabled the identification of molecular features associated with Aβ-lowering activity, establishing a qualitative structure-activity relationship. Peptide 33 (P33) emerged as a lead candidate, selectively reducing BACE1-associated activity without significantly inhibiting the associated activity of the homologous enzyme, BACE2. In vitro blood-brain barrier (BBB) assays revealed that P33 exhibits favorable transendothelial permeability. Intraperitoneal administration of P33 in APP/PS1 mice decreased Aβ levels, reduced amyloid plaque burden, and improved performance in a behavioral recognition task without inducing cytotoxicity, and with no overt histopathological or selected neuroinflammatory changes. These results define cis-γ-amino-L-proline peptides as a bioorganically distinct and modular scaffold for the development of intracellular modulators of Aβ production.