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Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations
10:26

Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations

Published on: November 7, 2019

Sensitivity of mammalian cells expressing mutant ubiquitin to protein-damaging agents

M Tsirigotis1, M Zhang, R K Chiu

  • 1Ottawa Regional Cancer Centre, Ottawa, Ontario K1H 1C4, Canada.

The Journal of Biological Chemistry
|October 13, 2001
PubMed

Insights

The ubiquitin-proteasome system degrades damaged proteins. Impairing this pathway in mammalian cells increases sensitivity to toxins, suggesting its crucial cytoprotective role.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Neuroscience

Background:

  • The ubiquitin/proteasome pathway is essential for degrading misfolded or damaged proteins in yeast.
  • Comparable studies in mammalian cells are challenging due to technical limitations.
  • The cytoprotective role of this pathway in mammalian cells remains to be fully elucidated.

Purpose of the Study:

  • To investigate the cytoprotective function of the ubiquitin/proteasome pathway in mammalian cells.
  • To determine if defects in this pathway predispose cells to toxic insults.

Main Methods:

  • Introduction of epitope-tagged wild-type ubiquitin and dominant-negative ubiquitin mutants into mouse HT4 neuroblastoma cells.
  • Exposure of cells to cadmium (oxidative damage inducer) and canavanine (misfolded protein inducer).
  • Analysis of cell sensitivity and proteasome substrate accumulation.

Main Results:

  • Cells expressing mutant ubiquitin showed increased sensitivity to cadmium and canavanine.
  • The greatest sensitivity to canavanine was observed in cells with ubiquitin mutants deficient in Lys(48) linkage formation.
  • Accumulation of proteasome substrates indicated a general deficit in proteolysis.

Conclusions:

  • The ubiquitin-mediated proteolytic system is crucial for protecting mammalian cells against toxic insults.
  • Defects in this system render cells vulnerable to the damaging effects of abnormal proteins.

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