Prion peptide 106-126 as a model for prion replication and neurotoxicity

Abstract

Prion diseases or transmissible spongiform encephalopathies are neurodegenerative disorders that are genetic, sporadic, or infectious. The pathogenetic event common to all prion disorders is a change in conformation of the cellular prion protein (PrPC) to the scrapie isoform (PrPSc), which, unlike PrPC, aggregates easily and is partially resistant to protease digestion. Although PrPSc is believed to be essential for the pathogenesis and transmission of prion disorders, the mechanism by which PrPSc deposits cause neurodegeneration is unclear. It has been proposed that in some cases of prion disorders, a transmembrane form of PrP, termed CtmPrP may be the mediator of neurodegenerative changes rather than PrPSc per se. In order to understand the underlying cellular processes by which PrPSc mediates neurodegeneration, we have investigated the mechanism of neurotoxicity by a beta-sheet rich peptide of PrP in a cell model. We show that exposure of human neuronal cell lines NT-2 and M17 to the prion peptide 106-126 (PrP106-126) catalyzes the aggregation of endogenous cellular prion protein (PrPC) to an amyloidogenic form that shares several characteristics with PrPSc. Intracellular accumulation of these PrPSc-like forms upregulates the synthesis of CtmPrP, which is proteolytically cleaved in the endoplasmic reticulum and the truncated C-terminal fragment is transported to the cell surface. In addition, we have isolated mutant NT-2 and neuroblastoma cells that are resistant to toxicity by PrP106-126 to facilitate further characterization of the biochemical pathways of PrP106-126 neurotoxicity. The PrP106-126-resistant phenotype of these cells could result from aberrant binding or internalization of the peptide, or due to an abnormality in the downstream pathway(s) of neuronal toxicity. Thus, our data suggest that PrPSc aggregation occurs by a process of 'nucleation' on a pre-existing 'seed' of PrP. Furthermore, the PrP106-126-resistant cells reported here will provide a unique opportunity for identifying the cellular and biochemical pathways that mediate neurotoxicity by PrPSc.

Kosmotropic Anions Promote Conversion of Recombinant Prion Protein into a PrPSc-Like Misfolded Form

“…The citotoxic activity occurred at very low concentrations of recPrP res comparable to those produced by PrP27-30 purified from the brain of prion infected animals. These concentrations are 1000-times lower than those used with small PrP fragments polymerized into amyloid fibrils [37], [38]. As expected, soluble recPrP and the dialysis buffer gave a near-to-zero toxicity (Fig.…”

Connecting the dots: trafficking of neurotrophins, lectins and diverse pathogens by binding to the neurotrophin receptor p75NTR

“…P75 binds prion peptides and prion peptides damage cells through the binding and activation of the p75 receptor (Della‐Bianca et al ., 2001; Perini et al ., 2002b). Prion proteins are internalized and enter an endocytotic route in neuronal cell lines (Singh et al ., 2002). Moreover, cellular forms of prion protein as well as p75 receptors are both present in caveolar rafts of the plasma membrane (Bilderback et al ., 1999; Martins et al ., 2002).…”

PrP(106–126) activates neuronal intracellular kinases and Egr1 synthesis through activation of NADPH‐oxidase independently of PrPc

“…Several kinases, along with the generation of reactive oxygen species (ROS), are involved in this process in a number of cell types [7,8]. However, the relevance of PrP(106-126) as a model of prioninduced cell effects and the role of PrPc expression in PrPsc and PrP(106-126)-induced effects have both been subject to debate [5,[9][10][11][12][13]. Thus, in this study we examined intracellular signalling cascades, the participation of PrPc and the relevance of ROS production in the neurotoxic effects induced by exposure to PrP(106-126) in cortical cultures with normal PrPc levels and in Prnp À/À cells.…”