Normal prion protein trafficking in cultured human erythroblasts

Normal prion protein (PrPc), an essential substrate for development of prion disease, is widely distributed in hemopoietic cells. Recent evidence that variant Creutzfeldt-Jakob disease can be transmitted by transfusion of red cell preparations has highlighted the need for a greater understanding of the biology of PrPc in blood and blood forming tissues. Here we show that in contrast to another glycosylphosphoinositol-anchored protein CD59, PrPc at the cell surface of cultured human erythroblasts is rapidly internalised through the endosomal pathway where it colocalises with the tetraspanin CD63. In the plasma membrane PrPc colocalises with the tetraspanin CD81. Cross-linking with anti- PrPc or anti-CD81 causes clustering of PrPc and CD81 suggesting they can share the same microdomain. These data are consistent with a role for tetraspanin-enriched microdomains in trafficking of PrPc. These results, when taken together with recent evidence that exosomes released from cells as a result of endosomal-mediated recycling to the plasma membrane contain prion infectivity, provide a pathway for the propagation of prion diseases.