Mammalian Prion protein expression in yeast; a model for transmembrane insertion

Area of Science:

• * Molecular Biology
• * Cell Biology
• * Neuroscience

Background:

• * The prion protein (PrP) is a glycoprotein involved in neurological diseases.
• * Mammalian microsomes show inefficient PrP secretion, with significant amounts existing as transmembrane (TM) proteins.
• * The TM1 segment's hydrophobicity and orientation (Ntm vs. Ctm) are critical for PrP's membrane insertion and trafficking.

Purpose of the Study:

• * To investigate the role of TM1 hydrophobicity and electrostatic interactions in PrP membrane insertion and orientation.
• * To evaluate the utility of a yeast expression system as a model for studying PrP trafficking and the effects of mutations.
• * To explore the correlation between CtmPrP insertion and neuropathology.

Main Methods:

• * In vitro studies using mammalian microsomes and yeast expression systems.
• * Analysis of PrP mutations affecting TM1 hydrophobicity and charge.
• * Assessment of PrP insertion orientation (Ntm/Ctm) and secretion levels.
• * Correlation analysis between CtmPrP levels and neuropathology in transgenic mice.

Main Results:

• * Increased TM1 hydrophobicity in PrP mutations leads to higher Ctm insertion, both in vitro and in mouse brains.
• * A strong correlation exists between CtmPrP insertion and neuropathology in transgenic mice.
• * The yeast model effectively mimics the effects of PrP mutations on TM insertion, despite differences in trafficking machinery.
• * Electrostatic charge differences across TM1 significantly influence PrP insertion orientation, with specific charge alterations promoting secretion over Ctm insertion.

Conclusions:

• * TM1 hydrophobicity and electrostatic interactions are key determinants of PrP membrane insertion and orientation.
• * The yeast model is a valuable tool for studying PrP trafficking and the impact of mutations.
• * CtmPrP insertion is linked to PrP-associated neuropathology, suggesting a potential pathogenic mechanism.
• * Understanding PrP membrane insertion provides insights into prion disease mechanisms and potential therapeutic targets.