Effect of Membrane Cholesterol Levels and Allelic Variation on Prion Conversion

Abstract

Chronic Wasting Disease (CWD) is caused by an accumulation of misfolded prion proteins (PrPsc) and subsequent plaque formation in the central nervous system. CWD is horizontally transferable; misfolded prions from one animal can enter another and cause normal prion proteins (PrPc) to misfold. This misfolding process is termed prion conversion. In natural deer populations an allelic variation in the prion gene is thought to confer resistance to CWD. Wild type mule deer are serine (S) homozygotes at codon 225. Mule deer that are Serine/ Phenyalanine (S/F) heterozygotes exhibit resistance to prion infection. In this study the F encoding allele was cloned into a bacterial vector. From this stage a recombinant virus can be made and used to determine the biochemical mechanisms responsible for disease resistance. A further area of study focused on membrane microdomains or cholesterol rafts. Prion proteins are concentrated to these lipid raft regions. This may affect the conversion process. Using insect cells cultured in cholesterol depleted medium, lipid raft reduction occurred. Conversion assays can now be performed on cholesterol depleted cells to determine if lipid raft reduction influences prion conversion.