The prion protein preference of sporadic Creutzfeldt-Jakob disease subtypes

PHB2 Alleviates Neurotoxicity of Prion Peptide PrP106-126 via PINK1/Parkin-Dependent Mitophagy

Prion diseases are a group of neurodegenerative diseases characterized by mitochondrial dysfunction and neuronal death. Mitophagy is a selective form of macroautophagy that clears injured mitochondria. Prohibitin 2 (PHB2) has been identified as a novel inner membrane mitophagy receptor that mediates mitophagy. However, the role of PHB2 in prion diseases remains unclear. In this study, we isolated primary cortical neurons from rats and used the neurotoxic prion peptide PrP106-126 as a cell model for prion diseases. We examined the role of PHB2 in PrP106-126-induced mitophagy using Western blotting and immunofluorescence microscopy and assessed the function of PHB2 in PrP106-126-induced neuronal death using the cell viability assay and the TUNEL assay. The results showed that PrP106-126 induced mitochondrial morphological abnormalities and mitophagy in primary cortical neurons. PHB2 was found to be indispensable for PrP106-126-induced mitophagy and was involved in the accumulation of PINK1 and recruitment of Parkin to mitochondria in primary neurons. Additionally, PHB2 depletion exacerbated neuronal cell death induced by PrP106-126, whereas the overexpression of PHB2 alleviated PrP106-126 neuronal toxicity. Taken together, this study demonstrated that PHB2 is indispensable for PINK1/Parkin-mediated mitophagy in PrP106-126-treated neurons and protects neurons against the neurotoxicity of the prion peptide.

Organoids for modeling prion diseases

Human cerebral organoids are an exciting and novel model system emerging in the field of neurobiology. Cerebral organoids are spheres of self-organizing, neuronal lineage tissue that can be differentiated from human pluripotent stem cells and that present the possibility of on-demand human neuronal cultures that can be used for non-invasively investigating diseases affecting the brain. Compared with existing humanized cell models, they provide a more comprehensive replication of the human cerebral environment. The potential of the human cerebral organoid model is only just beginning to be elucidated, but initial studies have indicated that they could prove to be a valuable model for neurodegenerative diseases such as prion disease. The application of the cerebral organoid model to prion disease, what has been learned so far and the future potential of this model are discussed in this review.

The Three Glycotypes in the London Classification System of Sporadic Creutzfeldt-Jakob Disease Differ in Disease Duration

Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common form of CJD and is believed to be caused by the misfolding and aggregation of endogenous prion protein. Several classification systems have been developed to correlate the molecular characteristics of these misfolded prions (PrP^Sc) to the heterogeneous clinical presentations of sCJD. A central component of these systems is glycotyping, which involves the interpretation of the results of western immunoblotting of the protease-resistant fragment of the misfolded prion protein (PrP^res). The two main classification systems differ in their recognition of a unique banding pattern on electrophoretic gels correlating to a putative clinical subtype. The perpetuation of both classification systems within scientific literature is, in part, due to a paucity of high-level evidence that conclusively addresses the merit of recognising each unique banding pattern. Here, 110 post-mortem confirmed cases of sCJD collected at the Australian Creutzfeldt-Jakob Disease Registry (ANCJDR) between 1993 and 2018 were analysed and classified as per the London classification system. The data presented here demonstrated that sCJD cases with 'type 1' and 'type 2' PrP^Sc as defined by the London classification system differ in their disease duration. No other differences in clinical phenotype or biological characteristics were found to be statistically significant. These findings highlight the importance of sample size and replicability in analyses of this rare disease process. Recognising these glycotypes as phenotypically distinct may represent 'best practice' in the collection and processing of sCJD samples within international registries for research purposes.

In vitro Modeling of Prion Strain Tropism

Prions are atypical infectious agents lacking genetic material. Yet, various strains have been isolated from animals and humans using experimental models. They are distinguished by the resulting pattern of disease, including the localization of PrPsc deposits and the spongiform changes they induce in the brain of affected individuals. In this paper, we discuss the emerging use of cellular and acellular models to decipher the mechanisms involved in the strain-specific targeting of distinct brain regions. Recent studies suggest that neuronal cultures, protein misfolding cyclic amplification, and combination of both approaches may be useful to explore this under-investigated but central domain of the prion field.

Prion Diseases

Prion diseases are a group of invariably fatal and transmissible neurodegenerative disorders that are associated with the misfolding of the normal cellular prion protein, with the misfolded conformers constituting an infectious unit referred to as a "prion". Prions can spread within an affected organism by directly propagating this misfolding within and between cells and can transmit disease between animals of the same and different species. Prion diseases have a range of clinical phenotypes in humans and animals, with a principle determinant of this attributed to different conformations of the misfolded protein, referred to as prion strains. This chapter will describe the different clinical manifestations of prion diseases, the evidence that these diseases can be transmitted by an infectious protein and how the misfolding of this protein causes disease.

Glycosaminoglycan sulfation determines the biochemical properties of prion protein aggregates

Prion diseases are transmissible neurodegenerative disorders associated with the conversion of the cellular prion protein, PrP(C), to a misfolded isoform called PrP(Sc). Although PrP(Sc) is a necessary component of the infectious prion, additional factors, or cofactors, have been shown to contribute to the efficient formation of transmissible PrP(Sc). Glycosaminoglycans (GAGs) are attractive cofactor candidates as they can be found associated with PrP(Sc) deposits, have been shown to enhance PrP misfolding in vitro, are found in the same cellular compartments as PrP(C) and have been shown to be disease modifying in vivo. Here we investigated the effects of the sulfated GAGs, heparin and heparan sulfate (HS), on disease associated misfolding of full-length recombinant PrP. More specifically, the degree of sulfation of these molecules was investigated for its role in modulating the disease-associated characteristics of PrP. Both heparin and HS induced a β-sheet conformation in recombinant PrP that was associated with the formation of aggregated species; however, the biochemical properties of the aggregates formed in the presence of heparin or HS varied in solubility and protease resistance. Furthermore, these properties could be modified by changes in GAG sulfation, indicating that subtle changes in the properties of prion disease cofactors could initiate disease associated misfolding.

Epidemiological genetics and meta-analysis of a polymorphism at codon 129 of the PRNP gene in Alzheimer's disease in Brazil

The polymorphism at codon 129 of the prion protein gene (PRNP) is a major risk factor for Creutzfeldt-Jakob disease (CJD). Several authors reported neuropathological and clinical overlapping between CJD and Alzheimer's disease (AD), with a few association studies generating conflicting results. To investigate the distribution of this polymorphism in AD, we selected 58 patients with probable AD and 73 controls from a Brazilian population. There was no association between the PRNP polymorphism at codon 129 and AD. Our meta-analysis (performed using Alzgene; http://www.alzgene.org) along with previous studies conducted in Brazil demonstrated a negative association.

Molecular dynamics studies on 3D structures of the hydrophobic region PrP(109-136)

Prion diseases, traditionally referred to as transmissible spongiform encephalopathies, are invariably fatal and highly infectious neurodegenerative diseases that affect a wide variety of mammalian species, manifesting as scrapie in sheep, bovine spongiform encephalopathy (or 'mad-cow' disease) in cattle, and Creutzfeldt-Jakob disease, Gerstmann-Strussler-Scheinker syndrome, fatal familial insomnia (FFI), and Kulu in humans, etc. These neurodegenerative diseases are caused by the conversion from a soluble normal cellular prion protein (PrP(C)) into insoluble abnormally folded infectious prions (PrP(Sc)). The hydrophobic region PrP(109-136) controls the formation of diseased prions: the normal PrP(113-120) AGAAAAGA palindrome is an inhibitor/blocker of prion diseases and the highly conserved glycine-xxx-glycine motif PrP(119-131) can inhibit the formation of infectious prion proteins in cells. This article gives detailed reviews on the PrP(109-136) region and presents the studies of its three-dimensional structures and structural dynamics.