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Clearance of yeast prions by misfolded multi-transmembrane proteins

Chie Arai1, Hiroshi Kurahashi, Masao Ishiwata

  • 1Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Tokyo 108-8639, Japan.

Biochimie
|February 7, 2013
PubMed

Insights

Overproducing mutant multi-transmembrane proteins triggers the heat shock response (HSR) and clears yeast prions. The GET pathway is crucial for this process, trapping misfolded proteins in the ER.

Area of Science:

  • Cellular biology
  • Protein quality control
  • Molecular mechanisms

Background:

  • Misfolded proteins in the endoplasmic reticulum (ER) trigger cellular stress responses like the unfolded protein response (UPR) and heat shock response (HSR).
  • These responses, along with ER-associated degradation, aim to mitigate protein toxicity.
  • Yeast prions, such as [PSI(+)] and [URE3], are protein-based genetic elements susceptible to cellular quality control mechanisms.

Purpose of the Study:

  • To investigate the cellular response to overproduced C-terminally truncated multi-transmembrane (MTM) mutant proteins.
  • To determine the role of the GET (Guided Entry of Tail-anchored) pathway in the handling of these MTM mutants.
  • To elucidate the mechanism by which MTM mutants affect yeast prion clearance.

Main Methods:

  • Overproduction of C-terminally truncated MTM mutant proteins in yeast.
  • Induction of heat shock response (HSR) and unfolded protein response (UPR) assays.
  • Fluorescence microscopy to track protein localization (Dip5ΔC-v82).
  • Genetic analysis of mutants defective in the GET pathway.

Main Results:

  • Overproduction of MTM mutants induced HSR but not UPR.
  • The MTM mutant Dip5ΔC-v82 accumulated abnormally in the ER.
  • Defects in the GET pathway prevented Dip5ΔC-v82 translocation to the ER and abolished Dip5ΔC-v82-mediated prion clearance.
  • MTM mutant-induced prion clearance was observed.

Conclusions:

  • The GET pathway is essential for the quality assurance of MTM proteins.
  • Misfolded MTM proteins are entrapped in ER compartments via the GET pathway.
  • This entrapment leads to the loss of yeast prions through an uncharacterized mechanism.

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