Alkylating Antitumor Drug Mechlorethamine Conceals A Structured PrP Domain and Inhibits in Vitro Prion Amplification

Abstract

Prion diseases are a group of incurable transmissible neurodegenerative disorders. The key molecular event in the pathogenesis of prion diseases is the conversion of the cellular prion protein (PrP^C) into its pathological isoform (PrP^Sc), accompanied by a conformational transition of α-helix into β-sheet structure involving the structured α-helix 1 domain from residues 144–154 of the protein (PrP144-154). Blocking the accessibility of PrP144-152 with anti-PrP antibody 6H4 was found to prevent PrP conversion and even to cure prion infection in cell models (Enari et al. 2001). Previously, Yuan et al. (2005) demonstrated that the reduction and alkylation of PrP induced concealment of the 6H4 epitope. This study examined the ability of mechlorethamine (MCT), an alkylating antitumor drug, to conceal the 6H4 epitope and block PrP conversion in the presence of a reducing reagent. Mechlorethamine treatment significantly decreased in vitro amplification of PrP^Sc in the highly efficient protein misfolding cyclic amplification system. Our findings suggest that MCT may serve as a potential therapeutic agent for prion diseases.

Acknowledgments

The authors are grateful to Dr. Witold Surewicz for providing recombinant human PrP and Dr. Claudio Soto for help in learning PMCA technology in his laboratory. This study was supported by grants (to W.Q.Z.) from the National Institutes of Health (NIH) R01 NS062787, the CJD Foundation, Alliance BioSecure, and the University Center on Aging and Health with the support of the McGregor Foundation and the President's Discretionary Fund (Case Western Reserve University).

Notes

Xiaochen Zhou, Hao Bi, and Justin Wong contributed equally to this work.