Glycosylation of PrPC determines timing of neuroinvasion and targeting in the brain following transmissible spongiform encephalopathy infection by a peripheral route.

Transmissible spongiform encephalopathy (TSE) infectivity naturally spreads from site of entry in the periphery to the central nervous system where pathological lesions are formed. Several routes and cells within the host have been identified as important for facilitating the infectious process. Expression of the glycoprotein cellular PrP (PrP(C)) is considered a key factor for replication of infectivity in the central nervous system (CNS) and its transport to the brain, and it has been suggested that the infectious agent propagates from cell to cell via a domino-like effect.

Dramatic reduction of PrP C level and glycosylation in peripheral nerves following PrP knock-out from Schwann cells does not prevent transmissible spongiform encephalopathy neuroinvasion.

Expression of the prion protein (PrP(C)) is a requirement for host susceptibility to the transmissible spongiform encephalopathies (TSEs) and thought to be necessary for the replication and transport of the infectious agent. The mechanism of TSE neuroinvasion is not fully understood, although the routing of infection has been mapped through the peripheral nervous system (PNS) and Schwann cells have been implicated as a potential conduit for transport of the TSE infectious agent. To address whether Schwann cells are a requirement for spread of the TSE agent from the site of infection to the CNS, PrP(C) expression was selectively removed from Schwann cells in vivo.

Host PrP glycosylation: a major factor determining the outcome of prion infection.

The expression of the prion protein (PrP) is essential for transmissible spongiform encephalopathy (TSE) or prion diseases to occur, but the underlying mechanism of infection remains unresolved. To address the hypothesis that glycosylation of host PrP is a major factor influencing TSE infection, we have inoculated gene-targeted transgenic mice that have restricted N-linked glycosylation of PrP with three TSE strains. We have uniquely demonstrated that mice expressing only unglycosylated PrP can sustain a TSE infection, despite altered cellular location of the host PrP.

Altered glycosylated PrP proteins can have different neuronal trafficking in brain but do not acquire scrapie-like properties.

N-Linked glycans have been shown to have an important role in the cell biology of a variety of cell surface glycoproteins, including PrP protein. It has been suggested that glycosylation of PrP can influence the susceptibility to transmissible spongiform encephalopathy and determine the characteristics of the many different strains observed in this particular type of disease. To understand the role of carbohydrates in influencing the PrP maturation, stability, and cell biology, we have produced and analyzed gene-targeted murine models expressing differentially glycosylated PrP.

Polymorphisms at codons 108 and 189 in murine PrP play distinct roles in the control of scrapie incubation time.

Susceptibility to transmissible spongiform encephalopathies (TSEs) is associated strongly with PrP polymorphisms in humans, sheep and rodents. In mice, scrapie incubation time is controlled by polymorphisms at PrP codons 108 (leucine or phenylalanine) and 189 (threonine or valine), but the precise role of each polymorphism in the control of disease is unknown. The L108F and T189V polymorphisms are present in distinct structural regions of PrP and thus provide an excellent model with which to investigate the role of PrP structure and gene variation in TSEs.

Cre-loxP mediated control of PrP to study transmissible spongiform encephalopathy diseases.

Expression of the PrP glycoprotein is essential for the development of the transmissible spongiform encephalopathy (TSE) or prion diseases. Although PrP is widely expressed in the mouse, the precise relevance of different PrP-expressing cell types to disease remains unclear. To address this, we generated two lines of floxed PrP gene-targeted transgenic mice using the Cre recombinase-loxP system.

Expression of doppel in the CNS of mice does not modulate transmissible spongiform encephalopathy disease.

Late onset ataxia reported in three independently derived PrP null lines of mice has been attributed to the overexpression of the doppel protein in the CNS of these mice rather than to the loss of PrP. The central role of PrP in the transmissible spongiform encephalopathies (TSEs), the proximity of the gene which encodes doppel (Prnd) to the PrP gene (Prnp) and the structural similarity shared by PrP and doppel have led to the proposition that ataxia which develops during TSE disease could, in part, be due to doppel. In order to address this hypothesis, we have crossed our two inbred lines of PrP null mice, which either express (RCM) or do not express (NPU) the Prnd gene in the CNS, with mice expressing two Prnp(a[108F189V]) alleles of the PrP gene.