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. Transgenic mice carrying the PrP substitution threonine for asparagine 180 (G1) or threonine for asparagine 196 (G2) or both mutations combined (G3), which eliminate the first, second, and both glycosylation sites, respectively, have been generated by double replacement gene targeting. An in vivo analysis of altered PrP has been carried out in transgenic mouse brains, and our data show that the lack of glycans does not influence PrP maturation and stability. The presence of one chain of sugar is sufficient for the trafficking to the cell membrane, whereas the unglycosylated PrP localization is mainly intracellular. However, this altered cellular localization of PrP does not lead to any overt phenotype in the G3 transgenic mice. Most importantly, we found that, in vivo, unglycosylated PrP does not acquire the characteristics of the aberrant pathogenic form (PrPSc), as was previously reported using in vitro models

Host PrP Glycosylation: A Major Factor Determining the Outcome of Prion Infection

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177The 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. Moreover we have shown that brain material from mice infected with TSE that have only unglycosylated PrPSc is capable of transmitting infection to wild-type mice, demonstrating that glycosylation of PrP is not essential for establishing infection within a host or for transmitting TSE infectivity to a new host. We have further dissected the requirement of each glycosylation site and have shown that different TSE strains have dramatically different requirements for each of the glycosylation sites of host PrP, and moreover, we have shown that the host PrP has a major role in determining the glycosylation state of de novo generated PrPSc.https://doi.org/10.1371/journal.pbio.00601006pubpub

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

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177Item not available from this repository.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. Two unique lines of transgenic mice, in which 108F and 189V have been targeted separately into the endogenous murine Prnp a gene, have been produced. TSE inoculation of inbred lines of mice expressing all allelic combinations at codons 108 and 189 has revealed a complex relationship between PrP allele and incubation time. It has been established that both codons 108 and 189 control TSE incubation time, and that each polymorphism plays a distinct role in the disease process. Comparison of ME7 incubation times in mouse lines that are heterozygous at both codons has also identified a previously unrecognized intramolecular interaction between PrP codons 108 and 189.https://doi.org/10.1099/vir.0.80525-086pubpub

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. Moreover we have shown that brain material from mice infected with TSE that have only unglycosylated PrP(Sc) is capable of transmitting infection to wild-type mice, demonstrating that glycosylation of PrP is not essential for establishing infection within a host or for transmitting TSE infectivity to a new host. We have further dissected the requirement of each glycosylation site and have shown that different TSE strains have dramatically different requirements for each of the glycosylation sites of host PrP, and moreover, we have shown that the host PrP has a major role in determining the glycosylation state of de novo generated PrP(Sc)

The role of host PrP in control of incubation time

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177Item is not available from this repository.PrP is central to TSE disease and has been hypothesised to be the infectious agent. Polymorphisms in the PrP gene are associated with different incubation times of disease following exposure to an infectious agent and mutations in the human PrP gene can apparently lead to spontaneous genetic disease. Strains of TSE agent are proposed to be generated and maintained through differences in glycosylation or conformation of PrP and the barrier to infection between species is thought to be due to the differences in the sequence of PrP between different species. To test these hypotheses, we have introduced specific modifications into the endogenous mouse Prnp gene by gene targeting. The mutated PrP gene is in the correct location under the control of the endogenous Prnp regulatory sequences and thus expressed in the same tissues and amounts as the wild type Prnp gene. By altering the murine PrP coding region to that of another species we have established that increasing overall identity between host and donor PrP can lead to either an increase or a decrease in incubation time of disease in a strain dependent manner. We have introduced a point mutation (101L) into the N-terminus of the host PrP and shown that it dramatically changes the susceptibility of the host to infection from different species. We have in addition demonstrated that polymorphisms in the N terminus (L108T) and C-terminus (F189V) of host PrP both alter the incubation time of disease. We have in addition introduced mutations into the Prnp gene which prevent glycosylation at each or both of the two N-linked glycosylation sites of PrP. Inoculation of these mice with infectivity has established that glycosylation of host PrP can influence incubation time of disease, vacuolar pathology and strain determination.https://doi.org/10.1007/4-431-29402-3_