The Quest for Cellular Prion Protein Functions in the Aged and Neurodegenerating Brain

Abstract

Cellular (also termed ‘natural’) prion protein has been extensively studied for many years for its pathogenic role in prionopathies after misfolding. However, neuroprotective properties of the protein have been demonstrated under various scenarios. In this line, the involvement of the cellular prion protein in neurodegenerative diseases other than prionopathies continues to be widely debated by the scientific community. In fact, studies on knock-out mice show a vast range of physiological functions for the protein that can be supported by its ability as a cell surface scaffold protein. In this review, we first summarize the most commonly described roles of cellular prion protein in neuroprotection, including antioxidant and antiapoptotic activities and modulation of glutamate receptors. Second, in light of recently described interaction between cellular prion protein and some amyloid misfolded proteins, we will also discuss the molecular mechanisms potentially involved in protection against neurodegeneration in pathologies such as Alzheimer’s, Parkinson’s, and Huntington’s diseases.

Alzheimer’s disease as a syndrome of overloaded amyloidic synaptic tagging in memory networks

“…PRPC is expressed in neurons and glia, mainly on the cell surface as a glycosylphosphatidylinositol-anchored protein localized to lipid rafts. Though PRPC was, and understandably so, initially viewed as a bête noire, it is becoming clear that it serves many important physiological functions by interacting with extracellular and intracellular partners (Table 3) (Aguzzi et al, 2008;Castle and Gill, 2017;Didonna, 2013;Gavin et al, 2020;Linden, 2017;Miranzadeh Mahabadi and Taghibiglou, 2020;Peggion et al, 2017;Puig et al, 2020;Schneider et al, 2011;Sorgato et al, 2009;Watts et al, 2018;Wulf et al, 2017). Importantly, unlike APP, PRPC does not possess an intracytoplasmic tail and appears to act as a co-receptor serving as a conduit for various extracellular and membrane molecules.…”

Behavioral deficits, learning impairment, and enhanced hippocampal excitability in co-isogenic PrnpZH3/ZH3 mice

“…PrP C has been previously described as neuroprotective, mainly by using loss-offunction approaches [14][15][16], while in other studies, PrP C overexpression was associated with increased susceptibility to neurotoxicity and cell death [15,[17][18][19]. This might mean that Prnp levels should be constrained to a certain level to develop their natural functions [11,15].…”

“…Indeed, this controversy was also strengthened by the absence, until a few years ago, of an appropriate knock-out mouse model with high breeding capability to dissect biological relevance in specific processes (i.e., (del Rio and Gavin, 2016;Onodera et al, 2014;Steele et al, 2007;Watts et al, 2018;Wulf et al, 2017)). PrP C has been described as neuroprotective, mainly by using loss-of-function approaches (Carulla et al, 2015;Chiarini et al, 2002;Gavin et al, 2020;Resenberger et al, 2011;Roucou et al, 2004), while in other studies, PrP C overexpression was associated with increased susceptibility to neurotoxicity and cell death (Gavin et al, 2020;Llorens and Del Rio, 2012;Paitel et al, 2003;Paitel et al, 2004;Rangel et al, 2009). This might mean that Prnp levels should be constrained to a certain level to develop their natural functions (i.e., (del Rio and Gavin, 2016;Gavin et al, 2020;Nicolas et al, 2009)).…”

“…PrP C has been described as neuroprotective, mainly by using loss-of-function approaches (Carulla et al, 2015;Chiarini et al, 2002;Gavin et al, 2020;Resenberger et al, 2011;Roucou et al, 2004), while in other studies, PrP C overexpression was associated with increased susceptibility to neurotoxicity and cell death (Gavin et al, 2020;Llorens and Del Rio, 2012;Paitel et al, 2003;Paitel et al, 2004;Rangel et al, 2009). This might mean that Prnp levels should be constrained to a certain level to develop their natural functions (i.e., (del Rio and Gavin, 2016;Gavin et al, 2020;Nicolas et al, 2009)). This balance is altered in several injuries and neurodegenerative processes presenting changes in mRNA and protein expression (e.g., Alzheimer's disease, dementia with Lewy bodies, some tauopathies (Goetzl et al, 2020;Leng et al, 2020;Lidon et al, 2020;Llorens et al, 2013;Vergara et al, 2015), human prionopathies (i.e., sCJD (Llorens et al, 2013)), and multiple sclerosis (Scalabrino et al, 2015).…”

“…PrP C has been previously described as neuroprotective, mainly by using loss-offunction approaches [14][15][16], while in other studies, PrP C overexpression was associated with increased susceptibility to neurotoxicity and cell death [15,[17][18][19]. This might mean that Prnp levels should be constrained to a certain level to develop their natural functions [11,15]. This balance is altered in several injuries and neurodegenerative processes, presenting changes in mRNA and protein expression, for example, in Alzheimer's disease, dementia with Lewy bodies, some tauopathies [20,21], human prionopathies (e.g., sporadic Creutzfeldt Jakob Disease (sCJD) [22]), and multiple sclerosis [23].…”