title: Characterization of detergent-insoluble complexes containing the cellular prion protein and its scrapie isoform.
abstract: Cells infected with prions contain both prion protein isoforms cellular prion protein (PrPC) and scrapie prion protein (PrPSc). PrPSc is formed posttranslationally through the pathological refolding of PrPC. In scrapie-infected ScN2a cells, the metabolism of both PrP isoforms involves cholesterol-dependent pathways. We show here that both PrPC and PrPSc are attached to Triton X-100-insoluble, low-density complexes or "rafts." These complexes are sensitive to saponin and thus probably contain cholesterol. This finding suggests that the transformation PrPC --> PrPSc occurs within rafts. It also reveals the existence of rafts in late compartments of the endocytic pathway, where most PrPSc resides. When Triton X-100 lysates of cells were incubated at 37 degrees C prior to density analysis, PrPC was still found in buoyant complexes, although it now failed to sediment at high speed. This property was shared by another glycophosphatidyl inositol protein, Thy-1, and also by the raft resident GM1. In one ScN2a clone and in the brain of a Syrian hamster with scrapie, Triton X-100 extraction at 37 degrees C permitted resolution of PrPC and PrPSc into two distinct peaks of different densities. This suggests that there are two populations of PrP-containing rafts and may permit isolation of PrPC-specific rafts from those containing PrPSc. Our findings reinforce the contention that rafts are involved in various aspects of PrP metabolism and in the "life cycle" of prions.
authors.affiliation: Department of Molecular Biology, the Hebrew University-Hadassah Medical School, P. O. Box 12272, Jerusalem 91120, Israel.
authors.forename: N
authors.initials: N
authors.lastname: Naslavsky
authors.forename: R
authors.initials: R
authors.lastname: Stein
authors.forename: A
authors.initials: A
authors.lastname: Yanai
authors.forename: G
authors.initials: G
authors.lastname: Friedlander
authors.forename: A
authors.initials: A
authors.lastname: Taraboulos
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000737:chemistry; D006224:Cricetinae; D003902:Detergents; D005677:G(M1) Ganglioside / Q000737:chemistry; D017261:Glycosylphosphatidylinositols; D008647:Mesocricetus; D051379:Mice; D011328:Prions / Q000737:chemistry*; D012503:Saponins / Q000737:chemistry; D012608:Scrapie; D012995:Solubility; D018800:Thy-1 Antigens / Q000737:chemistry
chemical_list: D003902:Detergents; D017261:Glycosylphosphatidylinositols; D011328:Prions; D012503:Saponins; D018800:Thy-1 Antigens; D005677:G(M1) Ganglioside; D002784:Cholesterol