The cellular prion protein colocalizes with the dystroglycan compiler in the brain

The function of PrPC, the cellular prion protein (PrP), is still unknown. L ike other glycophosphatidylinositol-anchored proteins, PrP resides on Trito n-insoluble, cholesterol-rich membranous microdomains, termed rafts. We hav e recently shown that the activity and subcellular localization of the neur onal isoform of nitric oxide synthase (nNOS) are impaired in adult PrP0/0 m ice as well as in scrapie-infected mice. In this study, we sought to determ ine whether PrP and nNOS are part of the same functional complex and, if so , to identify additional components of such a complex. To this aim, we look ed for proteins that coimmunoprecipitated with PrP in the presence of deter gents either that completely dissociate rafts, to identify stronger interac tions, or that preserve the raft structure, to identify weaker interactions . Using this detergent-dependent immunoprecipitation protocol we found that PrP interacts strongly with dystroglycan, a transmembrane protein that is the core of the dystrophin-glycoprotein complex (DGC). Additional results s uggest that PrP also interacts with additional members of the DGC, includin g nNOS. PrP coprecipitated only with established presynaptic proteins, cons istent with recent findings suggesting that PrP is a presynaptic protein.