Prions prevent neuronal cell-line death

Prion diseases, such as scrapie and bovine spongiform encephalopathy (BSE) in animals and Creutzfeldt-Jakob disease (CJD) in humans, are neurodegenerative conditions characterized by the accumulation of a post-transcriptionally modified, pathological form of a host-encoded glycoprotein, designated PrPSc. The physiological function of the normal cellular isoform, PrPC, is unknown, although studies of mice devoid of PrPC have indicated that it may be involved in normal synaptic function and survival of Purkinje cells, but findings have been inconsistent1,2,3,4,5,6. We find that serum removal from the cell culture causes apoptosis in Prnp−/− cells (in which a disrupted form of the prion protein is produced) but not in Prnp+/+ (wild-type) cells. Transduction of PrP or the Bcl-2 gene suppressed apoptosis of Prnp−/− cells under serum-free conditions. We also found that Prnp−/− cells extended shorter neurites than Prnp+/+ cells, but expression of PrPC increased their length. These findings support the idea that the loss of function of PrPC may partly underlie the pathogenesis of prion diseases.