Systematic Identification of Antiprion Drugs by High-Throughput Screening Based on Scanning for Intensely Fluorescent Targets

Abstract

ABSTRACT Conformational changes and aggregation of specific proteins are hallmarks of a number of diseases, like Alzheimer's disease, Parkinson's disease, and prion diseases. In the case of prion diseases, the prion protein (PrP), a neuronal glycoprotein, undergoes a conformational change from the normal, mainly alpha-helical conformation to a disease-associated, mainly beta-sheeted scrapie isoform (PrP Sc ), which forms amyloid aggregates. This conversion, which is crucial for disease progression, depends on direct PrP C /PrP Sc interaction. We developed a high-throughput assay based on scanning for intensely fluorescent targets (SIFT) for the identification of drugs which interfere with this interaction at the molecular level. Screening of a library of 10,000 drug-like compounds yielded 256 primary hits, 80 of which were confirmed by dose response curves with half-maximal inhibitory effects ranging from 0.3 to 60 μM. Among these, six compounds displayed an inhibitory effect on PrP Sc propagation in scrapie-infected N2a cells. Four of these candidate drugs share an N ′-benzylidene-benzohydrazide core structure. Thus, the combination of high-throughput in vitro assay with the established cell culture system provides a rapid and efficient method to identify new antiprion drugs, which corroborates that interaction of PrP C and PrP Sc is a crucial molecular step in the propagation of prions. Moreover, SIFT-based screening may facilitate the search for drugs against other diseases linked to protein aggregation.