PrPSc incorporation to cells requires endogenous glycosaminoglycan expression

Many lines of evidence suggest an interaction between glycosaminoglycans (GAGs) and the PrP proteins as well as a possible role for GAGs in prion disease pathogenesis. In this work, we sought to determine whether the PrP-GAG interaction affects the incorporation of PrPSc (the scrapie isoform of PrP) to normal cells. This may be the first step in prion disease pathogenesis. To this effect, we incubated proteinase K-digested hamster scrapie brain homogenates with several lines of Chinese hamster ovary (CHO) cells in the presence or absence of heparin. Our results show that over a large range of PrPSc concentrations the binding of PrPSc to wild type CHO cells, which do not express detectable PrP, was equivalent to the binding of PrPSc to CHO cells overexpressing PrP. A significant part of PrPSc binding to both lines could be inhibited by heparin. Additional evidence that PrPSc binding to cells was dependent on the presence of GAGs could be concluded from the fact that the binding of PrPSc to CHO cells missing GAGs on the cell surface was significantly reduced. Interestingly, preincubation of scrapie brain homogenate with heparin before intraperitoneal inoculation into normal hamsters resulted in a significant delay in prion disease manifestation.