Wild-Type PrP and a Mutant Associated with Prion Disease are Subject to Retrograde Transport and Proteasome Degradation

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 98; no. 26; pp. 14955 - 14960
• Main Authors: Ma, Jiyan, Lindquist, Susan
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 18.12.2001; National Acad Sciences; The National Academy of Sciences
• Subjects: Antibodies; Base Sequence; Biological Sciences; Cell aggregates; Cell Line; COS cells; Cultured cells; Cysteine Endopeptidases - metabolism; Cysteine Proteinase Inhibitors - pharmacology; Cytoplasm; Disease; DNA Primers; Fluorescent Antibody Technique; Hydrolysis; Multienzyme Complexes - metabolism; Mutagenesis, Site-Directed; Neurons; Prion diseases; Prion Diseases - genetics; Prion Diseases - metabolism; Prions; Proteasome Endopeptidase Complex; Protein Transport; Proteins; PrPSc Proteins - genetics; PrPSc Proteins - metabolism; Transfection
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.011578098

The cytoplasm seems to provide an environment that favors conversion of the prion protein (PrP) to a form with the physical characteristics of the PrPScconformation, which is associated with transmissible spongiform encephalopathies. However, it is not clear whether PrP would ever exist in the cytoplasm under normal circumstances. We report that PrP accumulates in the cytoplasm when proteasome activity is compromised. The accumulated PrP seems to have been subjected to the normal proteolytic cleavage events associated with N- and C-terminal processing in the endoplasmic reticulum, suggesting that it arrives in the cytoplasm through retrograde transport. In the cytoplasm, PrP forms aggregates, often in association with Hsc70. With prolonged incubation, these aggregates accumulate in an "aggresome"-like state, surrounding the centrosome. A mutant (D177N), which is associated with a heritable and transmissible form of the spongiform encephalopathies, is less efficiently trafficked to the surface than wild-type PrP and accumulates in the cytoplasm even without proteasome inhibition. These results demonstrate that PrP can accumulate in the cytoplasm and is likely to enter this compartment through normal protein quality-control pathways. Its potential to accumulate in the cytoplasm has implications for pathogenesis.