Domain-Specific Activation of Death-Associated Intracellular Signalling Cascades by the Cellular Prion Protein in Neuroblastoma Cells

Abstract

The biological functions of the cellular prion protein remain poorly understood. In fact, numerous studies have aimed to determine specific functions for the different protein domains. Studies of cellular prion protein (PrP(C)) domains through in vivo expression of molecules carrying internal deletions in a mouse Prnp null background have provided helpful data on the implication of the protein in signalling cascades in affected neurons. Nevertheless, understanding of the mechanisms underlying the neurotoxicity induced by these PrP(C) deleted forms is far from complete. To better define the neurotoxic or neuroprotective potential of PrP(C) N-terminal domains, and to overcome the heterogeneity of results due to the lack of a standardized model, we used neuroblastoma cells to analyse the effects of overexpressing PrP(C) deleted forms. Results indicate that PrP(C) N-terminal deleted forms were properly processed through the secretory pathway. However, PrPΔF35 and PrPΔCD mutants led to death by different mechanisms sharing loss of alpha-cleavage and activation of caspase-3. Our data suggest that both gain-of-function and loss-of-function pathogenic mechanisms may be associated with N-terminal domains and may therefore contribute to neurotoxicity in prion disease. Dissecting the molecular response induced by PrPΔF35 may be the key to unravelling the physiological and pathological functions of the prion protein.

Role of cellular prion protein in interneuronal amyloid transmission

“…Increased caspase 3 activation after PrP C overexpression has also been reported in other studies (Nicolas et al, 2007;Vilches et al, 2016). Thus, it is reasonable to consider that PrP C may be maintained at a physiological level, since increase or reduction may strongly interfere with other cellular processes that might induce cell death (Llorens et al, 2013b;Vergara et al, 2015).…”

“…Other studies have shown that aggregation of PrP C in cell membrane in vitro (Mouillet-Richard et al, 2000) and in vivo (Solforosi et al, 2004) triggers cell death which is associated with increased production of reactive oxygen species (ROS), and activation of the proto-oncogene tyrosine-protein (Fyn) kinase and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. However, overexpression of PrP C alone does not increase ROS production (Vilches et al, 2016), thus reinforcing the opinion that PrP C -mediated p53 activation is not associated with Fyn activation (Paitel et al, 2003;Paitel et al, 2004).To sum up, PrP C -mediated sensitization and aggregation may regulate cell death by different mechanisms.…”

Reelin Expression in Creutzfeldt-Jakob Disease and Experimental Models of Transmissible Spongiform Encephalopathies

“…2c, d), reinforcing the notion that the presence of reelin is not mandatory in the increased p-Dab1 levels mediated by PrP . Increased kinase activity and high levels of ROS have been described after prion infection [33,66,[68][69][70] and in sCJD patients [33]. Thus, we aimed to explore whether ROS generation in treated cultures participates in the observed changes in Reelin expression.…”

“…Cell death was assessed using a propidium iodide (PI, Sigma-Aldrich) [57]. Briefly, shortly after treatments in 24-well plates, 30 μM PI was added to each well.…”

Functions of the cellular prion protein, the end of Moore's law, and Ockham's razor theory

“…Cell survival and cellular prion protein PrP C increase cell proliferation and survival 1 PrP C absence increases proliferation of hippocampal precursors 26 PrPC mediate cell cycle on neuroblastoma cells 2 Cell survival by acting on PIK3 kinase 87 Cell survival promoting glucose uptake in cancer cells 88 Cell survival after genotoxic stress 89 Yeast prion promote drug resistance and cell survival 90 Neurotoxicity induced by the cellular prion protein or its domains in vitro and in vivo A syntethic peptide of PrP C is neurotoxic 79,82 Description of the neurotoxicity of the putative transmembrane domain of PrP C . 91 Description of the neurotoxic potential of the cytoplasmic domain of PrP C 92 Peptides mimicking the central domain of PrP C triggers cell-death pathways 93 PrP C aggregating antibodies induced cell death 9 Membrane tethered PrP C triggers cell death in mice 59 The flexible tail of PrP C mediates cell-death induced by PrP antibodies 73 PrP C -directed antibodies do not trigger apoptosis 81 Distinct domains of PrP C triggers different intracellular cell-death signals 94 Cellular prion protein and Alzheimer´s disease (Aβ) . PrP C –derived peptides bind to amyloid precursor protein (APP) 95 PrP C regulates BACE1 activity 34 and APP processing 84 PrP C mediates impairment of synaptic plasticity mediated by Aβ 96,97 PrP C mediates the toxicity of Aβ oligomers 98,99 PrP C is not involved in Aβ-mediated toxicity and synaptic plasticity 42 PrP C expression is needed for memory impairment in mouse models of Alzheimer disease 100 PrP C immunotargeting in vivo prevents Aβ-mediated LTP inhibition 101 The N-terminal domain of PrP C binds to Aβ oligomers 102 PrP C modulate Aβ production and deposition in mouse models 103 Metabotropic glutamate receptor 5 is a coreceptor of Aβ oligomers and PrP C 104 Blocking Aβ binding to PrP C as terapeuthic strategy for Alzheimer´s disease.…”