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Pathogenic Isoform (pathogenic + isoform)
Selected AbstractsPost-transcriptional suppression of pathogenic prion protein expression in Drosophila neuronsJOURNAL OF NEUROCHEMISTRY, Issue 6 2003Nathan R. Deleault Abstract A wealth of evidence supports the view that conformational change of the prion protein, PrPC, into a pathogenic isoform, PrPSc, is the hallmark of sporadic, infectious, and inherited forms of prion disease. Although the central role played by PrPSc in the pathogenesis of prion disease is appreciated, the cellular mechanisms that recognize PrPSc and modulate its production, clearance, and neural toxicity have not been elucidated. To address these questions, we used a tissue-specific expression system to express wild-type and disease-associated PrP molecules heterologously in Drosophila melanogaster. Our results indicate that Drosophila brain possesses a specific and saturable mechanism that suppresses the accumulation of PG14, a disease-associated insertional PrP mutant. We also found that wild-type PrP molecules are maintained in a detergent-soluble conformation throughout life in Drosophila brain neurons, whereas they become detergent-insoluble in retinal cells as flies age. PG14 protein expression in Drosophila eye did not cause retinal pathology. Our work reveals the presence of mechanisms in neurons that specifically counterbalance the production of misfolded PrP conformations, and provides an opportunity to study these processes in a model organism amenable to genetic analysis. [source] Packaging of prions into exosomes is associated with a novel pathway of PrP processing,THE JOURNAL OF PATHOLOGY, Issue 5 2007LJ Vella Abstract Prion diseases are fatal, transmissible neurodegenerative disorders associated with conversion of the host-encoded prion protein (PrPC) into an abnormal pathogenic isoform (PrPSc). Following exposure to the infectious agent (PrPSc) in acquired disease, infection is propagated in lymphoid tissues prior to neuroinvasion and spread within the central nervous system. The mechanism of prion dissemination is perplexing due to the lack of plausible PrPSc -containing mobile cells that could account for prion spread between infected and uninfected tissues. Evidence exists to demonstrate that the culture media of prion-infected neuronal cells contain PrPSc and infectivity but the nature of the infectivity remains unknown. In this study we have identified PrPC and PrPSc in association with endogenously expressing PrP neuronal cell-derived exosomes. The exosomes from our prion-infected neuronal cell line were efficient initiators of prion propagation in uninfected recipient cells and to non-neuronal cells. Moreover, our neuronal cell line was susceptible to infection by non-neuronal cell-derived exosome PrPSc. Importantly, these exosomes produced prion disease when inoculated into mice. Exosome-associated PrP is packaged via a novel processing pathway that involves the N-terminal modification of PrP and selection of distinct PrP glycoforms for incorporation into these vesicles. These data extend our understanding of the relationship between PrP and exosomes by showing that exosomes can establish infection in both neighbouring and distant cell types and highlight the potential contribution of differentially processed forms of PrP in disease distribution. These data suggest that exosomes represent a potent pool of prion infectivity and provide a mechanism for studying prion spread and PrP processing in cells endogenously expressing PrP. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Engineering the prion protein using chemical synthesisCHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2001H.L. Ball Abstract: In recent years, the technology of solid-phase peptide synthesis (SPPS) has improved to the extent that chemical synthesis of small proteins may be a viable complementary strategy to recombinant expression. We have prepared several modified and wild-type prion protein (PrP) polypeptides, of up to 112 residues, that demonstrate the flexibility of a chemical approach to protein synthesis. The principal event in prion disease is the conformational change of the normal, ,-helical cellular protein (PrPC) into a ,-sheet-rich pathogenic isoform (PrPSc). The ability to form PrPSc in transgenic mice is retained by a 106 residue ,mini-prion' (PrP106), with the deletions 23,88 and 141,176. Synthetic PrP106 (sPrP106) and a His-tagged analog (sPrP106HT) have been prepared successfully using a highly optimized Fmoc chemical methodology involving DCC/HOBt activation and an efficient capping procedure with N -(2-chlorobenzyloxycarbonyloxy) succinimide. A single reversed-phase purification step gave homogeneous protein, in excellent yield. With respect to its conformational and aggregational properties and its response to proteinase digestion, sPrP106 was indistinguishable from its recombinant analog (rPrP106). Certain sequences that proved to be more difficult to synthesize using the Fmoc approach, such as bovine (Bo) PrP(90,200), were successfully prepared using a combination of the highly activated coupling reagent HATU and t -Boc chemistry. To mimic the glycosylphosphatidyl inositol (GPI) anchor and target sPrP to cholesterol-rich domains on the cell surface, where the conversion of PrPC is believed to occur, a lipophilic group or biotin, was added to an orthogonally side-chain-protected Lys residue at the C-terminus of sPrP sequences. These groups enabled sPrP to be immobilized on either the cell surface or a streptavidin-coated ELISA plate, respectively, in an orientation analogous to that of membrane-bound, GPI-anchored PrPC. The chemical manipulation of such biologically relevant forms of PrP by the introduction of point mutations or groups that mimic post-translational modifications should enhance our understanding of the processes that cause prion diseases and may lead to the chemical synthesis of an infectious agent. [source] Manganese chelation therapy extends survival in a mouse model of M1000 prion diseaseJOURNAL OF NEUROCHEMISTRY, Issue 2 2010Marcus W. Brazier J. Neurochem. (2010) 114, 440,451. Abstract Previous in vitro and in vivo investigations have suggested manganese (Mn2+) may play a role in pathogenesis through facilitating refolding of the normal cellular form of the prion protein into protease resistant, pathogenic isoforms (PrPSc), as well as the subsequent promotion of higher order aggregation of these abnormal conformers. To further explore the role of Mn2+ in pathogenesis, we undertook a number of studies, including an assessment of the disease modifying effects of chelation therapy in a well-characterized mouse model of prion disease. The di-sodium, calcium derivative of the chelator, cyclohexanediaminetetraacetic acid (Na2CaCDTA), was administered intraperitoneally to mice inoculated intra-cerebrally with either high or low-dose inocula, with treatment beginning early (shortly after inoculation) or late (at the usual mid-survival point of untreated mice). Analyses by inductively coupled plasma-mass spectrometry demonstrated brain Mn2+ levels were selectively reduced by up to 50% in treated mice compared with untreated controls, with copper, iron, zinc and cobalt levels unchanged. In mice administered high-dose inocula, none of the treatment groups displayed an increase in survival although western blot analyses of early intensively treated mice showed reduced brain PrPSc levels; mice infected using low-dose inocula however, showed a significant prolongation of survival (p = 0.002). Although our findings support a role for Mn2+ in prion disease, further studies are required to more precisely delineate the extent of pathogenic involvement. [source] | ||||||||||