Abstract
The transmissible spongiform encephalopathies (TSEs) comprise a group of fatal neurodegenerative diseases that are characterized by the conversion of the normal host cellular prion protein (PrPC), to the abnormal protease-resistant prion protein isoform (PrP-res). It has been proposed, though not proven, that the infectious TSE agent consists solely of PrP-res and that PrP-res-induced conformational conversion of PrPC to additional PrP-res represents agent replication. In this study we demonstrate in situ conversion of protease-sensitive PrPC to PrP-res in TSE-infected brain slices. One step in this process is the binding of soluble PrPC to endogenous PrP-res deposits. The newly formed PrP-res associated with the slices in a pattern that correlated with the pre-existing brain distribution of PrP-res. Punctate in situ PrP conversion was observed in brain regions containing PrP-res amyloid plaques, and a more dispersed conversion product was detected in areas containing diffuse PrP-res deposits. These studies provide direct evidence that PrP-res formation involves the incorporation of soluble PrPC into both nonfibrillar and fibrillar PrP-res deposits in TSE-infected brain. Our findings suggest that the in situ PrP conversion reaction leads to additional polymerization of endogenous PrP-res aggregates and is analogous to the process of PrP-res fibril and subfibril growth in vivo.
Highlights
This paper is dedicated to Richard F
The conversion reaction solution incubating on top of the TME-infected brain slice contained 35S-PrPC that was degraded by proteinase K (PK) and did not contain 35S-protease-resistant PrP (PrP-res)
These results indicate that transmissible spongiform encephalopathies (TSEs) infected slices can induce 35S-PrP conversion and that one step in the conversion is the binding of the 35S-PrP to the TME-infected brain tissue without subsequent release of 35S-PrP-res into the bathing medium
Summary
15227–15231, 1997 Printed in U.S.A. In Situ Formation of Protease-resistant Prion Protein in Transmissible Spongiform Encephalopathy-infected Brain Slices*. The transmissible spongiform encephalopathies (TSEs) comprise a group of fatal neurodegenerative diseases that are characterized by the conversion of the normal host cellular prion protein (PrPC), to the abnormal protease-resistant prion protein isoform (PrP-res). It has been proposed, though not proven, that the infectious TSE agent consists solely of PrP-res and that PrPres-induced conformational conversion of PrPC to additional PrP-res represents agent replication. In this study we investigated PrP-res formation in TSE-infected brain tissue by using intact brain slices instead of purified PrP-res in the cell-free conversion reaction. This in situ PrP conversion assay provides a powerful tool to model PrP-res formation in vivo
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