Proteinase K resistant material in ARR/VRQ sheep brain affected with classical scrapie is composed mainly of VRQ prion protein

Samenvatting

Classical scrapie is a prion disease in sheep and goats. In sheep, susceptibility to disease is genetically influenced by single amino acid substitutions. Genetic breeding programs aimed at enrichment of arginine-171 (171R) prion protein (PrP), the so called ARR allele, in the sheep population have demonstrated to be effective in reducing the occurrence of classical scrapie in the field. Understanding the molecular basis for this reduced prevalence would serve the assessment of ARR-adaptation. The prion formation mechanism and conversion of PrP from the normal form (PrPC) to scrapie associated form (PrPSc) could play a key-role in this process. Therefore, we investigated whether the ARR allele substantially contributes to scrapie prion formation in naturally infected heterozygous 171Q/R animals. Two methods were applied to brain tissue of 171Q/R heterozygous sheep with natural scrapie to determine the relative amount of the 171R PrP fraction in PrPres, the proteinase K-resistant PrPSc core. An antibody test differentiating between 171Q and 171R PrP fragments showed that PrPres mostly was composed of the 171Q allelotype. Furthermore using a novel tool for prion research, endoproteinase Lys-C digested PrPres yielded substantial amounts of non-glycosylated and mono-glycosylated 114-188 PrP fragment. Following two-dimensional gel electrophoresis only marginal amounts (