Acetylcholinesterase (ACNE), a senile plaque component, promotes amyloid-beta-protein (A beta) fibril formation in vitro. The presence of prion protein (PrP) in Alzheimer's disease (AD) senile plaques prompted us to assess if ACNE could trigger the PrP peptides aggregation as well. Consequently, the efficacy of ACNE on the PrP peptide spanning-residues 106-126 aggregation containing a coumarin fluorescence probe (coumarin-PrP 106-126) was studied. Kinetics of coumarin-PrP 106-126 aggregation showed a significant increase of maximum size of aggregates (MSA), which was dependent on ACNE concentration. ACNE-PrP 106-126 aggregates showed the tinctorial and optical amyloid properties as determined by polarized light and electronic microscopy analysis. A remarkable inhibition of MSA was obtained with propidium iodide, suggesting that ACNE triggers PrP 106-126 and A beta aggregation through a similar mechanism. Huprines (ACNE inhibitors) also significantly decreased MSA induced by ACNE as well, unveiling the potential interest for some ACNE inhibitors as a novel class of potential anti-prion drugs. (c) 2006 Elsevier Inc. All rights reserved.