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Proteasome pathway operates for the degradation of ornithine decarboxylase in intact cells

Y Murakami1, N Tanahashi, K Tanaka

  • 1Department of Biochemistry, Jikei University School of Medicine, Tokyo, Japan.

The Biochemical Journal
|July 1, 1996
PubMed

Insights

The 26 S proteasome degrades ornithine decarboxylase (ODC) in living cells. This proteasome-mediated ODC degradation is linked to cellular responses to osmotic changes.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Background:

  • Ornithine decarboxylase (ODC) is a key enzyme in polyamine synthesis.
  • ODC degradation is regulated by antizyme, an inhibitor induced by polyamines.
  • In vitro studies show ODC degradation by the 26 S proteasome is ATP-dependent.

Purpose of the Study:

  • To investigate if the proteasome mediates ODC degradation in living mammalian cells.
  • To explore the role of the proteasome in osmoregulated ODC degradation.

Main Methods:

  • Using lactacystin, a selective proteasome inhibitor, in hepatoma tissue-culture (HTC) cells.
  • Inducing ODC degradation via refeeding, hypotonic shock, and hypertonic shock.
  • Analyzing ODC-antizyme complex formation using cycloheximide.

Main Results:

  • Lactacystin significantly inhibited ODC degradation induced by refeeding and hypotonic shock.
  • Hypertonic shock increased the ratio of ODC-antizyme complex to total ODC.
  • Cycloheximide partially inhibited ODC degradation and ODC-antizyme complex formation during hypertonic shock.

Conclusions:

  • The antizyme-dependent, 26 S proteasome-catalyzed pathway degrades ODC in intact mammalian cells.
  • This pathway is involved in the osmoregulation of ODC degradation.

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