Neurotoxic Effect of the Complex of the Ovine Prion Protein (OvPrP ^C) and RNA on the Cultured Rat Cortical Neurons

Prion diseases are conformational diseases, many factors are involved in altering the conformation of prion, such as RNA, DNA, pH, and copper etc. However the neurotoxic mechanism of prion diseases is not clear yet. The aim of this study is to investigate the effect of the nucleoprotein complex of RNA and recombinant ovine prion protein (OvPrP ^C) on the cultured rat cortical neurons in vitro. Our previous study revealed that the nucleoprotein complex (OvPrP ^C-RNA) is characterized with high b sheet conformation and proteinase K resistance. Here we found that the OvPrP ^C-RNA induced marked neuronal cell death by the MTT (3-(4,5-dimethyl-thiazole -2-yl)-2,5-diphenyl -tetrazolium bromide) and TUNEL (TdT mediated biotindUTP nicked-end labeling) assay, and the neurotoxic effects were confirmed by testing the content of Bcl-2 Associated X protein (Bax) in the immunoprecipitation assay and Western blot assay. Compared to the control group, there is no significant difference of active Bax ortotal Bax after RNA alone treatment or OvPrP ^C alone treatment, but the OvPrP ^C-RNA induced significant increases of active Bax level, while the contents of total Bax had no obvious changes after OvPrP ^C-RNA treatment. The results suggested that OvPrP ^C-RNA is neurotoxic in vitro, which added further evidence to the current understanding of mechanism of cellular injury by RNA molecules for transformation of the PrPC to PrP ^Sc.