Transmission of prions

Transmissible spongiform encephalopathies (TSE) are fatal neuro-degenerative diseases of humans and animals. The underlying infectious agent, the prion, accumulates not only in the central ner-vous system (CNS) but also in secondary lymphoid organs. I will revisit the role of the immune system in peripheral prion pathogen-esis, while focusing on the mechanisms by which extraneural and extralymphatic prion infectivity develops.

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During pathogenesis of transmissible spongiform encephalopathies (TSEs) an abnormal form (PrP Sc ) of the host encoded prion protein (PrP C ) accu-mulates in insoluble fibrils and plaques. The two forms of PrP appear to have identical covalent structures, but differ in secondary and tertiary structure.

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Prion diseases are fatal neurodegenerative disorders caused by proteina-ceous infectious pathogens termed prions (PrP Sc ). To date, there is no pro-phylaxis or therapy available for these transmissible encephalopathies. Passive immunization with monclonal antibodies recognizing the normal host-encoded prion protein (PrP C ) has been reported to abolish PrP Sc infec-tivity and to delay onset of disease.

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The prion protein (PrP) is the key protein implicated in transmissible spongiform encephalopathies. It is a metalloprotein that binds manganese and copper. The latter is involved in the physiological function of the pro-tein. We have previously found that PrP expression inPichia pastorisaffects intracellular metal ion concentrations and that formation of protease-resistant PrP is induced by additional copper and⁄or manganese.

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Transmissible spongiform encephalopathies are fatal neurodegenerative dis-eases that are caused by unconventional pathogens and affect the central nervous system of animals and humans. Several different forms of these dis-eases result from natural infection (i.e. exposure to transmissible spongiform encephalopathy agents or prions, present in the natural environment of the respective host).

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The discovery of prion disease transmission in mammals, as well as a non-Mendelian type of inheritance in yeast, has led to the establishment of a new concept in biology, the prion hypothesis. The prion hypothesis postu-lates that an abnormal protein conformation propagates itself in an auto-catalytic manner using the normal isoform of the same protein as a substrate and thereby acts either as a transmissible agent of disease (in mammals),

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1The epidemic of bovine spongiform encephalopathy (BSE), or ‘mad cow disease’, and the subsequent emer-gence of a new variant of Creutzfeldt–Jakob disease (vCJD) in humans, has directed great political and sci-entific attention to a family of related neurodegenera-tive protein-misfolding diseases, collectively known as transmissible spongiform encephalopathies (TSEs) or prion diseases.

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As limited structural information is available on prion protein (PrP) mis-folding and aggregation, a causative link between the specific (supra)mole-cular structure of PrP and transmissible spongiform encephalopathies remains to be elucidated.

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Transmissible spongiform encephalopathies (TSEs), or prion diseases, are fatal neurodegenerative disorders caused by an infectious agent termed a prion, which can convert normal cellular prion protein (PrP C ) into a patho-logically misfolded isoform (PrP Sc ). Taking advantage of protein misfolding cyclic amplification (PMCA), a series of experiments was conducted to investigate the possible influences of pyridine nucleotides on the propaga-

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Abnormal forms of prion protein (PrP Sc ) accumulate via structural conver-sion of normal PrP (PrP C ) in the progression of transmissible spongiform encephalopathy. Under cell-free conditions, the process can be efficiently replicated usingin vitro PrP Sc amplification methods, including protein mis-folding cyclic amplification.

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The conformational conversion of prion protein (PrP) from a native con-formation to the amyloid form is a hallmark of transmissible spongiform encephalopathies. Conversion is usually monitored by fluorescent dyes, which bind generic amyloids and are less suited for living cell imaging.

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Prions are infectious proteins, in which self-propagating amyloid conforma-tions of proteins are transmitted. The budding yeast Saccharomyces cerevi-siae, one of the best-studied model eukaryotes, also has prions, and thus provides a tractable model system with which to understand the mechanisms of prion phenomena.

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The risk of acquiring variant Creutzfeldt–Jakob disease is closely related to polymorphism at codon 129 of the human prion gene, because almost all variant Creutzfeldt–Jakob disease patients are Met⁄Met homozygotes. Although animal transmission experiments corroborated this seeding dis-crimination, the origin of the differential seeding efficiency of the bovine prion seed for human codon 129 polymorphism remained elusive.

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Studies of mammalian prion diseases such as bovine spongiform encephalopathy have suggested that different strains consist of prion proteins with different conformations. Two recent studies of yeast prions have now formally demonstrated that multiple stable protein conformations are the basis of strain variation. deposited research Transmissible spongiform encephalopathies (TSEs) are a group of closely related neurodegenerative conditions of animals

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