Interaction of the cellular prion protein with raft-like lipid membranes

Abstract

AbstractConversion of the cellular isoform of the prion protein (PrPC) into the disease-associated isoform (PrPSc) plays a key role in the development of prion diseases. Within its cellular pathway, PrPCundergoes several posttranslational modifications, i.e., the attachment of two N-linked glycans and a glycosyl phosphatidyl inositol (GPI) anchor, by which it is linked to the plasma membrane on the exterior cell surface. To study the interaction of PrPCwith model membranes, we purified posttranslationally modified PrPCfrom transgenic Chinese hamster ovary (CHO) cells. The mono-, di- and oligomeric states of PrPCfree in solution were analyzed by analytical ultracentrifugation. The interaction of PrPCwith model membranes was studied using both lipid vesicles in solution and lipid bilayers bound to a chip surface. The equilibrium and mechanism of PrPCassociation with the model membranes were analyzed by surface plasmon resonance. Depending on the degree of saturation of binding sites, the concentration of PrPCreleased from the membrane into aqueous solution was estimated at between 10-9and 10-7 M. This corresponds to a free energy of the insertion reaction of -48 kJ/mol. Consequences for the conversion of PrPCto PrPScare discussed.