Discovery of Novel Anti-prion Compounds Using In Silico and In Vitro Approaches (original) (raw)

Prion diseases are associated with the conformational conversion of the physiological form of cellular prion protein (PrP C) to the pathogenic form, PrP Sc. Compounds that inhibit this process by blocking conversion to the PrP Sc could provide useful anti-prion therapies. However, no suitable drugs have been identified to date. To identify novel anti-prion compounds, we developed a combined structureand ligand-based virtual screening system in silico. Virtual screening of a 700,000-compound database, followed by cluster analysis, identified 37 compounds with strong interactions with essential hotspot PrP residues identified in a previous study of PrP C interaction with a known antiprion compound (GN8). These compounds were tested in vitro using a multimer detection system, cell-based assays, and surface plasmon resonance. Some compounds effectively reduced PrP Sc levels and one of these compounds also showed a high binding affinity for PrP C. These results provide a promising starting point for the development of anti-prion compounds. Prion diseases are a group of lethal neurodegenerative diseases of humans and animals, including human Creutzfeldt-Jakob disease; bovine spongiform encephalopathy; scrapie in sheep, hamsters, and mice; and chronic wasting diseases in deer 1,2. There are three causes of prion disease: hereditary, sporadic, and acquired by infection. All of these disease types are known to share the same pathogenic mechanism 2,3. The central event in prion disease pathogenesis is the conversion of the α-helix-rich cellular form of prion protein (PrP C) to a misfolded, β-sheet-rich, pathogenic, and infectious conformational isoform (PrP Sc), although the detailed structure of PrP Sc is still not fully characterised 1,4,5. This conversion initiates a chain replication reaction, where each newly converted PrP Sc molecule interacts with more PrP C molecules, fueling the formation of additional PrP Sc6,7. After this post-translational conversion, PrP Sc aggregates and becomes the detergent-insoluble, partially protease-resistant protein fraction that serves as the marker for prion diseases 8,9. Therefore, stabilization of the native PrP C conformation, without blocking the normal functions of PrP C , could reduce the rate of conversion to PrP Sc or even prevent prion disease. To date, screening has led to the identification of many anti-prion compounds 10. Several large molecules (pentosanpolysulfate 5 , suramin 11 , amphotericin B 12 , congo red 13 , and dendritic polyamines 14) and small molecules (bis-acridine 15 , polyphenol, phenothiazine, anti-histamine, statin, and some anti-malarial agents including quinacrine 16) have been reported to inhibit PrP Sc formation or to reduce the level of PrP C. The tyrosine kinase inhibitor, STI571 (Gleevec), cured scrapie-infected cells in a concentration-and