Prion diseases, also known as transmissible spongiform encephalopathies, are infectious fatal neurodegenerative diseases of humans and animals. A major feature of prion diseases is the refolding and aggregation of a normal host protein, prion protein (PrP) into a disease-associated form which may contribute to brain damage. In uninfected individuals normal PrP is anchored to the outer cell membrane by a sugar-phosphate-lipid linker molecule, known as GPI. In FY10 we showed that prion infection of mice expressing PrP lacking the GPI anchor resulted in a new type of fatal highly transmissible amyloid neurodegenerative disease. This disease displayed mechanisms of damage to brain cells and brain blood vessels found in Alzheimers disease and in familial amyloid brain diseases. In contrast, the typical sponge-like brain damage seen in prion diseases was not observed. These results suggested that presence or absence of PrP membrane anchoring could influence the type of neurodegeneration seen after prion infection. We are currently studying the role of PrP anchoring on susceptibility to prion infection by different routes of inoculation, including sciatic nerve, tongue, eye, intravenous and intraperitoneal. The preliminary results suggest that lack of PrP anchoring alters neuroinvasion by many of these routes. In other experiments in FY10 we continued to study the roles of cytokine and chemkine expression in brain on prion brain diseases. We are currently determining the kinetics of cytokine expression relative to brain damage in mice with either anchored PrP or anchorless PrP, in order to determine whether the cytokines precede or follow damage. This result should help determinee the role of cytokines in the disease process. We are also investigating the role of expression of normal prion protein on function of glutamate transporters in astrocytes in vitro. Primary undifferentiated astrocytes are being compared to astrocytes differentiated in vitro with either cAMP or neuron-conditioned medium, or co-cultivated with live neurons.
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