Interactions between normal, protease-sensitive prion protein (PrP-sen or PrPc) and its protease-resistant isoform (PrP-res or PrPsc) are critical in transmissible spongiform encephalopathy (TSE) diseases. To investigate the propagation of PrP-res between cells we tested whether PrP-res in scrapie brain microsomes can induce the conversion of PrP-sen to PrP-res if the PrP-sen is bound to uninfected raft membranes. Surprisingly, no conversion was observed unless the microsomal and raft membranes were fused or PrP-sen was released from raft membranes. These results suggest that the propagation of infection between cells requires transfer of PrP-res into the membranes of the recipient cell. To assess potential cofactors in PrP conversion, we used cell-free PrP conversion assays to show that heparan sulphate can stimulate PrP-res formation, supporting the idea that endogenous sulphated glycosaminoglycans can act as important cofactors or modulators of PrP-res formation in vivo. In an effort to develop therapeutics, the antimalarial drug quinacrine was identified as an inhibitor of PrP-res formation in scrapie-infected cell cultures. Confirmation of the latter result by others has led to the initiation of human clinical trials as a treatment for Creutzfeldt-Jakob disease. PrP-res formation can also be inhibited using a variety of other types of small molecule, specific synthetic PrP peptides, and an antiserum directed at the C-terminus of PrP-sen. The latter results help to localize the sites of interaction between PrP-sen and PrP-res. Disruption of those interactions with antibodies or peptidomimetic drugs may be an attractive therapeutic strategy. The likelihood that PrP-res inhibitors can rid TSE-infected tissues of PrP-res would presumably be enhanced if PrP-res formation were reversible. However, our attempts to measure dissociation of PrP-sen from PrP-res have failed under non-denaturing conditions. Finally, we have attempted to induce the spontaneous conversion of PrP-sen into PrP-res using low concentrations of detergents. A conformational conversion from α-helical monomers into high-β-sheet aggregates and fibrils was induced by low concentrations of the detergent sarkosyl; however, the aggregates had neither infectivity nor the characteristic protease-resistance of PrP-res.
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Conference Article|
August 01 2002
Factors affecting interactions between prion protein isoforms
B. Caughey;
B. Caughey
1
1National Institutes of Health, NIAID, Rocky Mountain Labs, Hamilton, MT 59840, U.S.A.
1To whom correspondence should be addressed (e-mail bcaughey@nih.gov)
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G. S. Baron
G. S. Baron
1National Institutes of Health, NIAID, Rocky Mountain Labs, Hamilton, MT 59840, U.S.A.
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Publisher: Portland Press Ltd
Received:
March 11 2002
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2002 Biochemical Society
2002
Biochem Soc Trans (2002) 30 (4): 565–569.
Article history
Received:
March 11 2002
Citation
B. Caughey, G. S. Baron; Factors affecting interactions between prion protein isoforms. Biochem Soc Trans 1 August 2002; 30 (4): 565–569. doi: https://doi.org/10.1042/bst0300565
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