Expression of the cellular prion protein (PrPC) from the PRNP gene is crucial for the development of a group of fatal neurodegenerative disorders called prion diseases. During prion infection a misfolded protein homologue of PrPC, PrPSc causes further misfolding on interaction with native PrPC molecules. PrPSc is highly resistant to proteinase K and aggregation of this protein is considered a hallmark of infection. Sheep are considered a model of natural infection and susceptibility to scrapie in sheep is defined by polymorphisms in the PRNP gene. It is still not fully understood how these polymorphisms regulate the conversion process or which other co-factors are involved. One such factor may be the truncation of PrPC via proteolytic processing in the form of two main cleavage events, known as α- and β-cleavage. In sheep α-cleavage cuts at amino acid 115, creating two truncated proteins C1 and N1 and represents the main cleavage event in healthy brain. β-Cleavage creates a longer C-terminal fragment, C2 and corresponding N-terminal fragment N2, cutting around amino acid 92 in sheep. Truncated forms of PrPC have been shown to represent around 50 % of total residual PrP in brain and may be an important determinant of disease through both decreasing the amount of full length PrPC available for conversion and through functions associated with the truncated fragments. The research presented has shown that increased production of an α-cleavage fragment C1 in brain is associated with TSE resistant genotype ARR/ARR, while the presence of C2 fragment is affiliated with scrapie susceptible PRNP genotypes in brain. There was no difference in the levels of full length PrPC in these genotypes suggesting that PrP expression does not directly correlate to susceptibility in this model. To assess if PrPC fragments could affect the conversion during disease in-vitro fibrillisation assays were performed using novel truncated recombinant proteins. These truncated proteins, although not thought to convert to PK resistant PrPSc during disease, can form amyloid fibrils. However, these fibrils appear to be less neurotoxic when compared to fibrils produced by full length PrPC. Only the truncated fragments derived from the ARR allele inhibit in-vitro fibrillisation of other allelic PrPC variants. Furthermore, treatment of infected cells in culture with recombinant C1ARR led to a decrease in the formation of disease associated PrPSc. In conclusion, genetic variations in levels of PrP truncated fragments may add to the complexity of genetic determinants of prion disease. In parallel with polymorphism-dependant conversion abilities, varying α-cleavage of ovine PrPC may help to explain genetic resistance in sheep. The inhibitory effects of C1, illustrated in-vitro may represent a therapeutic avenue in the treatment of prion disease.

Transmissible spongiform encephalopathies (TSEs) are rare, uniformly fatal neurodegenerative disorders that can affect many mammalian species, including humans. A hallmark of these diseases is the conversion of cellular prion protein (PrPC) into an abnormally folded form. This misfolded PrPC is infectious, since it can provide a template for pathogenic conversion of PrPC in a new host. In addition to any toxicity of the misfolded protein, loss of normal PrPC function could be involved in the neurodegenerative processes. However, the physiological role of PrPC is still poorly understood and this project has aimed to address that lack of knowledge. Out of the many putative functions ascribed to PrPC, the most commonly proposed is that it protects cells from stress. In contrast, I have found that stable transfection of the prion protein gene into SH-SY5Y neuroblastoma cells increases cell death in response to serum removal from the culture medium. Following treatment with several chemical toxins, two out of four stably transfected clones did, generally, display greater viability than untransfected cells that do not express detectable levels of PrPC. However, knockdown of PrPC expression by RNA interference had no effect on this stress resistance, indicating that it may not have been mediated directly by PrPC. Given the lack of robust stress protection afforded by PrPC transfection, proteomic analyses of the cells were carried out to identify alternative processes that were perturbed as a result of PrPC expression. The results obtained suggested roles for PrPC in cytoskeletal organisation and cell cycle regulation. Various proteins involved in cytoskeletal organisation were confirmed by western blotting to be differentially expressed in some or all of the stably transfected clones. Additionally, the expression changes to proteins involved in cell cycle regulation resulted in slower proliferation of the clones compared with untransfected cells, a difference that was reduced following RNA interference-mediated knockdown of PrPC. Taken together, these data suggested that specific growth factor-activated pathways were differentially regulated in the stably transfected clones. One candidate pathway was nerve growth factor (NGF) signalling, which promotes neuronal survival and differentiation as well as regulating various processes outside of the nervous system. PrPC-transfection resulted in altered expression of receptors for NGF, suggesting that the stably transfected clones were, indeed, responding differently to NGF stimulation. However, the molecular mechanism responsible for these expression changes remains to be determined, since co-immunoprecipitation experiments did not identify any physical interactions between PrPC and the NGF receptors. Nonetheless, a role for PrPC in modulating NGF signalling has the potential to explain many of the diverse phenotypic observations in PrPC-null mice and might indicate that loss of PrPC function is an important part of TSE pathogenesis.

La maladie sporadique de Creutzfeldt-Jakob (sCJD) est une encéphalopathie spongiforme transmissible mortelle caractérisée par une large gamme de manifestations cliniques et pathologiques. Les caractéristiques pathologiques de la SDMC dépendent en grande partie de la présence d'une forme mal repliée de protéine prion cellulaire (PrPC); Connu sous le nom de PrPSC et polymorphisme (méthionine et valine) au codon 129 du gène PRNP qui code pour PrPC. Les facteurs étiologiques exacts de la MCSJ sont encore inconnus. Le génotype Codon 129 du gène PRNP et le type de PrPSC (type 1 ou type 2) influent sur l'hétérogénéité de la maladie telle que définie par des caractéristiques pathologiques spécifiques de la région qui peuvent réguler les voies moléculaires qui conduisent au développement de phénotypes pathogènes dépendants des sous-types. Dans cette étude, nous avons étudié l'ensemble de la réglementation protéomique dans la région cerebrale du cerveau des deux sous-types les plus répandus (MM1 et VV2) des patients atteints de SDMC utilisant une électrophorèse sur gel bidimensionnelle (2DE) et une spectrométrie de masse. L'analyse de toutes les taches de protéines sur les gels 2DE avec le logiciel DECODON Delta2D a révélé vingt-cinq taches de protéines différenciées et l'identification de ces taches avec MALDI-TOF MS / MS a révélé quatre-vingts trois protéines différentiellement réglementées dans les deux sous-types dans la région du cervebelle du cerveau par les patients atteints de sCJD. Quarante protéines dans le sous-type MM1 et quarante-trois protéines dans le sous-type VV2 ont été classées. Douze protéines étaient communément réglementées dans les deux sous-types, dont cinq d'entre elles présentaient une régulation expresnelle inverse et le repos sept avait une régulation expresnelle similaire dans les deux sous-types. Les trois principaux mécanismes moléculaires cellulaires réglementés dans les deux sous-types comprennent: i) le cycle cellulaire; L'expression des gènes et la mort cellulaire, ii) - la réponse au stress cellulaire / le stress oxydatif et iii) - la transduction du signal et les fonctions synaptiques La plupart des protéines sous la classification des réponses au stress cellulaire étaient associées aux fonctions moléculaires cellulaires liées au stress oxydatif. DJ-1 qui est un capteur bien connu de stress oxydatif, a également été jugé réglementé dans la catégorie des réponses au stress cellulaire. Le DJ-1 protège les cellules contre le stress oxydatif directement en translocant au noyau pour l'activation de gènes antioxydants et indirectement en activant la voie Nrf2 / ARE. Nos résultats expérimentaux ont démontré l'activation de la voie Nrf2 / ARE dans les sous-types MM1 et VV2 de sCJD. Le DJ-1 a également montré une régulation positive significative dans son expression de l'ARNm dans les sous-types MM1 et VV2 mais l'expression des protéines uniquement dans le sous-type VV2 dans le cervelet du cerveau des patients atteints de sCJD. En outre, l'expression de la protéine DJ-1 a également été augmentée au cours des stades pré-symptomatiques et symptomatiques dans le cervelet du cerveau des modèles de souris de sCJD (MM1 et VV2) et pendant le stade clinique dans les échantillons de CSF des patients atteints de SDMC. Ces résultats suggèrent l'implication du stress oxydatif lors de la pathophysiologie de la SDMC et l'utilisation de DJ-1 comme capteur potentiel de stress oxydatif pendant la phase clinique de la sCJD.

Cellular prion protein (PrPc) is a GPI–anchored protein, of unknown function, found in a number of cells throughout the body. It is now widely believed that a mis-folded, protease resistant form of this protein is responsible for a group of fatal neurodegenerative diseases called transmissible spongiform encephalopathies (TSE), including Creutzfeldt-Jakob disease (CJD) and kuru in humans, scrapie in sheep, chronic wasting disease (CWD) in deer and elk and bovine spongiform encephalopathy (BSE) in cattle. Although the exact function of PrPc is unknown it has been implicated in copper binding, signal transduction and cell adhesion. The pathogenesis of prion diseases is poorly understood, however it is known that PrPc must be present in order for the disease to progress. Platelets have been shown to be the largest reservoir of PrPc in peripheral blood cells and previous studies in animal models have suggested platelets may also be involved in TSE infectivity. In this study, we determine the exact location of PrPc within human platelets, examine the mobilization and release of PrPc from activated platelets on both microvesicles and exosomes and suggest a possible role for platelets in prion infectivity. In addition we examine the role of PrPc within normal platelet functions including aggregation, signal transduction and adhesion. / May 2005

No description available.

Cellular prion protein (PrPc) is a GPI–anchored protein, of unknown function, found in a number of cells throughout the body. It is now widely believed that a mis-folded, protease resistant form of this protein is responsible for a group of fatal neurodegenerative diseases called transmissible spongiform encephalopathies (TSE), including Creutzfeldt-Jakob disease (CJD) and kuru in humans, scrapie in sheep, chronic wasting disease (CWD) in deer and elk and bovine spongiform encephalopathy (BSE) in cattle. Although the exact function of PrPc is unknown it has been implicated in copper binding, signal transduction and cell adhesion. The pathogenesis of prion diseases is poorly understood, however it is known that PrPc must be present in order for the disease to progress. Platelets have been shown to be the largest reservoir of PrPc in peripheral blood cells and previous studies in animal models have suggested platelets may also be involved in TSE infectivity. In this study, we determine the exact location of PrPc within human platelets, examine the mobilization and release of PrPc from activated platelets on both microvesicles and exosomes and suggest a possible role for platelets in prion infectivity. In addition we examine the role of PrPc within normal platelet functions including aggregation, signal transduction and adhesion.

Cellular prion protein (PrPc) is a GPI–anchored protein, of unknown function, found in a number of cells throughout the body. It is now widely believed that a mis-folded, protease resistant form of this protein is responsible for a group of fatal neurodegenerative diseases called transmissible spongiform encephalopathies (TSE), including Creutzfeldt-Jakob disease (CJD) and kuru in humans, scrapie in sheep, chronic wasting disease (CWD) in deer and elk and bovine spongiform encephalopathy (BSE) in cattle. Although the exact function of PrPc is unknown it has been implicated in copper binding, signal transduction and cell adhesion. The pathogenesis of prion diseases is poorly understood, however it is known that PrPc must be present in order for the disease to progress. Platelets have been shown to be the largest reservoir of PrPc in peripheral blood cells and previous studies in animal models have suggested platelets may also be involved in TSE infectivity. In this study, we determine the exact location of PrPc within human platelets, examine the mobilization and release of PrPc from activated platelets on both microvesicles and exosomes and suggest a possible role for platelets in prion infectivity. In addition we examine the role of PrPc within normal platelet functions including aggregation, signal transduction and adhesion.

Orientador: Profa. Dra. Giselle Cerchiaro / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2014. / A proteina prion celular (PrPC) e expressa em varios tipos celulares, especialmente no tecido nervoso. Sua funcao fisiologica completa ainda nao e bem conhecida, no entanto,sua influencia no desenvolvimento de doencas neurodegenerativas foi bem descrito. Essas doencas, mais tarde denominadas encefalopatias espongiformes, resultam de uma mudanca conformacional da PrPC (rica em ¿¿ helices) para a forma Scrapie (PrPSC, rica em folhas ¿À). Diversos estudos mostraram a associacao da PrPC, o metabolismo do cobre e a atividade antioxidante da superoxido dismutase (SOD). Contudo, mecanismos de atuacao da PrPC, neste contexto, permanecem indefinidos. Considerando o papel protetor da PrPC amplamente reportado na literatura, foram comparados os comportamentos de celulas de astrocitos de camundongo do tipo selvagem (WWT), e nocaute para a PrPC (WKO), sob condicoes de estresse oxidativo induzido por peroxido de hidrogenio. A ativacao de caspases 3 e 8 foi avaliada, observando-se que a linhagem WKO sofre apoptose de maneira mais lenta que a linhagem WWT; e que a ativacao da apoptose na linhagem nocaute ocorre pela via extrinseca, enquanto que na linhagem selvagem ocorre pela via intrinseca. Os niveis de atividade e expressao da enzima SOD1 tambem foram acompanhados, mostrando que a PrPC modula a ativacao de SOD1 a curto prazo, mas tambem induz o aumento da expressao a medio prazo. No caso da WKO, os niveis de atividade e expressao de SOD1 se mantiveram constantes. Testes de viabilidade celular confirmaram que a linhagem WKO morre mais lentamente, e os parametros bioquimicos de oxidacao (TBARS e carbonilacao de proteinas) elevados mostraram que o delay observado e potencialmente prejudicial a cultura. Os niveis de expressao de APP bem como de GFAP foram monitorados, mostrando que a linhagem selvagem possui menor pre-disposicao a formacao de agregados proteicos e maior capacidade de recuperacao pos-estresse. / The cellular prion protein (PrPC) is expressed in many cell types, especially in nervous tissue. Its physiological function is still unclear, however, his influence on the development of neurodegenerative diseases has been well described. These diseases, later called spongiform encephalopathies, are the result of a conformational change of PrPC (rich in á-helix) to the scrapie form (PrPSC rich in â-sheet). Several studies have demonstrated the association between PrPC, copper metabolism and antioxidant activity of Cu,Zn-Superoxide Dismutase (SOD1). However, action mechanisms of PrPC in this context remain undefined. Considering the protective role of the PrPC widely reported in the literature, the behavior of mouse astrocytes cells were compared to wild type (WWT), and knockout to PrPC (WKO), under conditions of oxidative stress induced by hydrogen peroxide. The activation of caspase 3 and 8 and has been evaluated, and it was observed that the knockout strain undergoes apoptosis more slowly than the wild type strain. The activation of apoptosis in the knockout strain occurs by the extrinsic route, whereas the wild type strain occurs by the intrinsic pathway. Activity levels and expression of SOD1 were also followed, showing that PrPC modulates short-term activation SOD1, and also induces increased expression in the medium term. The WKO cell type, keep activity levels and SOD1 expression constant. Cell viability tests confirmed that the strain WKO die more slowly, and biochemical parameters oxidation (TBARS and protein carbonylation) showed that the higher observed delay is potentially harmful to the cell culture. APP and GFAP expression levels were monitored, showing that the wild type has a lower predisposition to the formation of protein aggregates and higher capacity to post-stress recovery.

The conformational conversion of the cellular prion protein (PrPc) to the misfolded isoform (PrPsc) is the central pathogenic event in the transmissible neurodegenerative prion diseases. The recently shown transmissibility of variant Creutzfeldt-Jakob disease by blood transfusion emphasizes the need for better understanding of the PrPc in blood. In the current thesis, we focused on blood platelet PrPc, which has not been very well described so far. In the first part of the thesis, platelet PrPc was characterized as glycosylphosphatidylinositol- anchored glycoprotein with dominant diglycosylated form. Platelet PrPc was shown to be sensitive to cleavage with proteinase K, which is a feature discriminating between cellular and pathological prion protein. We have confirmed that platelet PrPc binds copper ions by its N- terminal octapeptide repeat region. Regarding quantity of PrPc molecules expressed on blood elements we have proved that both platelets and red blood cells express considerable amount of PrPc and thus can not be neglected in the problematic of prions transmission by blood transfusion. The detailed study regarding PrPc localization in blood platelets is presented in the second part of the thesis. PrPc was shown to be expressed in -granules as well as on the cytoplasmic membrane of...

The conformational conversion of the cellular prion protein (PrPc) to the misfolded isoform (PrPsc) is the central pathogenic event in the transmissible neurodegenerative prion diseases. The recently shown transmissibility of variant Creutzfeldt-Jakob disease by blood transfusion emphasizes the need for better understanding of the PrPc in blood. In the current thesis, we focused on blood platelet PrPc, which has not been very well described so far. In the first part of the thesis, platelet PrPc was characterized as glycosylphosphatidylinositol- anchored glycoprotein with dominant diglycosylated form. Platelet PrPc was shown to be sensitive to cleavage with proteinase K, which is a feature discriminating between cellular and pathological prion protein. We have confirmed that platelet PrPc binds copper ions by its N- terminal octapeptide repeat region. Regarding quantity of PrPc molecules expressed on blood elements we have proved that both platelets and red blood cells express considerable amount of PrPc and thus can not be neglected in the problematic of prions transmission by blood transfusion. The detailed study regarding PrPc localization in blood platelets is presented in the second part of the thesis. PrPc was shown to be expressed in -granules as well as on the cytoplasmic membrane of...