Amyloid Fibrils of Mammalian Prion Protein Are Highly Toxic to Cultured Cells and Primary Neurons
Journal of Biological Chemistry
A growing body of evidence indicates that small, soluble oligomeric species generated from a variety of proteins and peptides rather than mature amyloid fibrils are inherently highly cytotoxic. Here, we show for the first time that mature amyloid fibrils produced from full-length recombinant mammalian prion protein (rPrP) were highly toxic to cultured cells and primary hippocampal and cerebella neurons. Fibrils induced apoptotic cell death in a time-and dose-dependent manner. The toxic effect
... The toxic effect of fibrils was comparable with that exhibited by soluble small ␤-oligomers generated from the same protein. Fibrils prepared from insulin were not toxic, suggesting that the toxic effect was not solely due to the highly polymeric nature of the fibrillar form. The cell death caused by rPrP fibrils or ␤-oligomers was substantially reduced when expression of endogenous PrP C was down-regulated by small interfering RNAs. In opposition to the ␤-oligomer and amyloid fibrils of rPrP, the monomeric ␣-helical form of rPrP stimulated neurite outgrowth and survival of neurons. These studies illustrated that both soluble ␤-oligomer and amyloid fibrils of the prion protein are intrinsically toxic and confirmed that endogenously expressed PrP C is required for mediating the toxicity of abnormally folded external PrP aggregates. . 5 The abbreviations used are: rPrP, recombinant full-length prion protein; PrP C , cellular isoform of the prion protein; PrP Sc , disease-associated isoform of the prion protein; PLL, polylysine; siRNA, small interfering RNA.