Copper(II)-induced conformational changes and protease resistance in recombinant and cellular PrP - Effect of protein age and deamidation

While PrPC rearranges in the area of codons 104-113 to form PrPSc during pr ion infections, the events that initiate sporadic Creutzfeldt-Jakob disease are undefined. AS Cu(II) is a putative ligand for PrPC and has been implic ated in the pathogenesis of Creutzfeldt-Jakob disease and other neurodegene rative diseases, we investigated the structural effects of binding. Incubat ion of brain microsomes with Cu(II) generated similar to 30-kDa proteinase K-resistant PrP. Cu(II) had little effect on fresh recombinant PrP23-231, b ut aged protein characterized by conversion of Asn-107 to Asp decreased cu- helical content by similar to 30%, increased beta-sheet content 100%, forme d aggregates, and acquired proteinase K resistance in the presence of Cu(II ), These transitions took place without need for acid pH, organic solvents, denaturants, or reducing agents. Since conversion of Asn to Asp proceeds b y a spontaneous pathway involving deamidation, our data suggest that covale nt variants of PrPC arising in this manner may, in concert with Cu(II), gen erate PrPSc-like species capable of initiating sporadic prion disease.