Prion Protein Does Not Confer Resistance to Hippocampus-Derived Zpl Cells against the Toxic Effects of Cu2+, Mn2+, Zn2+ and Co2+ Not Supporting a General Protective Role for PrP in Transition Metal Induced Toxicity

Abstract

The interactions of transition metals with the prion protein (PrP) are well-documented and characterized, however, there is no consensus on their role in either the physiology of PrP or PrP-related neurodegenerative disorders. PrP has been reported to protect cells from the toxic stimuli of metals. By employing a cell viability assay, we examined the effects of various concentrations of Cu2+, Zn2+, Mn2+, and Co2+ on Zpl (Prnp -/-) and ZW (Prnp +/+) hippocampus-derived mouse neuronal cells. Prnp -/- Zpl cells were more sensitive to all four metals than PrP-expressing Zw cells. However, when we introduced PrP or only the empty vector into Zpl cells, we could not discern any protective effect associated with the presence of PrP. This observation was further corroborated when assessing the toxic effect of metals by propidium-iodide staining and fluorescence activated cell sorting analysis. Thus, our results on this mouse cell culture model do not seem to support a strong protective role for PrP against transition metal toxicity and also emphasize the necessity of extreme care when comparing cells derived from PrP knock-out and wild type mice.

Physiological Functions of the Cellular Prion Protein

“…For example, it was reported that PrP C -dependent internalisation of Cu 2+ by cells in culture occurred only when the extracellular Cu 2+ concentration exceeded physiologically relevant levels (Rachidi et al, 2003). Furthermore, although some studies have shown that PrP C expression can protect neuronal and non-neuronal cell lines from oxidative stress caused by excessive Cu 2+ (Rachidi et al, 2003; Watt et al, 2007), Cingaram et al (2015) found that transfecting PrP C into the Zpl hippocampal cell line, originally derived from Zurich I PrP C -knockout mice, did not result in protection from Cu 2+ -mediated toxicity.…”

“…Experiments in neuronal cell lines showed that PrP C transfection did not confer protection against the oxidative DNA damage and subsequent cell death caused by treatment with high levels of Mn 2+ , Co 2+ , or Zn 2+ (Watt et al, 2007; Cingaram et al, 2015). However, PrP C expression did protect neuroblastoma cells from the toxic effects of Fe 2+ treatment (Watt et al, 2007).…”

Interrogating the Dimerization Interface of the Prion Protein Via Site-Specific Mutations to p-Benzoyl-L-Phenylalanine

“…While the exact physiological function of the prion protein (PrP) is not fully understood, it seems to be a promiscuous protein being involved in several cellular processes and interacting with a great number of partners [1][2][3][4][5][6][7][8]. Nevertheless, PrP is famous for its involvement in devastating neurodegenerative disorders, especially in transmissible spongiform encephalopathies (TSEs), a group of incurable and lethal diseases [9,10].…”

Redox induces diverse effects on recombinant human wild-type PrP and mutated PrP with inserted or deleted octarepeats

“…Furthermore, saturation of recombinant mouse PrP with Cu 2+ has been reported to efficiently enhance conversion to PK-resistant PrP in protein misfolding cyclic amplification (19). Notably, in a previous study, the biochemical features of oxidized PG5, formed via redox, share similarity with Cu 2+ -and Mn 2+ -treated PrP, even with pathological PrP Sc (20). Therefore, it may be hypothesized that, as the propagating substrate for prions, increased oxidation of PrP C may benefit the conversion from PrP C to PrP Sc .…”