Abnormal properties of prion protein with insertional mutations in different cell types

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Inherited Creutzfeldt-Jakob disease (CJD) is linked to mutations in the prion protein (PrP) gene.
• Normal PrP (PrP-sen) has five octapeptide repeat regions; familial CJD is associated with six or more repeats.
• Mutations may promote the formation of abnormal, protease-resistant PrP (PrP-res), the hallmark of transmissible spongiform encephalopathies (TSEs).

Purpose of the Study:

• To investigate the impact of varying octapeptide repeat numbers in hamster PrP-sen on aggregation and protease resistance.
• To determine if altered PrP-sen properties correlate with TSE pathogenesis.

Main Methods:

• Generated and expressed hamster PrP-sen with 5, 7, 9, or 11 octapeptide repeats in mouse fibroblast and neuroblastoma cells.
• Assessed cell surface expression, aggregation, and protease resistance of the expressed PrP-sen variants.

Main Results:

• In fibroblast cells, PrP-sen with 7, 9, or 11 repeats showed altered surface expression, with all variants exhibiting abnormal aggregation and protease resistance.
• In neuroblastoma cells, PrP-sen with 9 or 11 repeats displayed abnormal aggregation and protease resistance, while surface expression remained normal.
• Regardless of cell type, PrP-sen with >7 repeats were more aggregated and protease-resistant than those with ≤7 repeats.

Conclusions:

• Increased octapeptide repeats in PrP-sen lead to abnormal aggregation and enhanced protease resistance, irrespective of cell type.
• These altered properties are more pronounced with more than seven repeats.
• However, the induced PrP-sen abnormalities are significantly less protease-resistant than genuine PrP-res and do not readily form PrP-res in vitro.