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Downregulation of IRS-1 protein in thapsigargin-treated human prostate epithelial cells

Hong Zhang1, Henry Hoff, Christian Sell

  • 1Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.

Experimental Cell Research
|September 23, 2003
PubMed

Insights

Thapsigargin induces apoptosis by increasing intracellular calcium and activating calpain, leading to decreased Insulin Receptor Substrate-1 (IRS-1) protein levels. Calpain inhibition prevents IRS-1 degradation and apoptosis.

Area of Science:

  • Cellular Biology
  • Biochemistry
  • Molecular Medicine

Background:

  • Thapsigargin treatment increases intracellular calcium, activating calpain and potentially inducing apoptosis.
  • Insulin Receptor Substrate-1 (IRS-1) is a key signaling protein in insulin and IGF-I pathways.
  • Prostate epithelial cells undergo apoptosis upon thapsigargin exposure.

Purpose of the Study:

  • To investigate the role of calpain in thapsigargin-induced apoptosis.
  • To determine the effect of thapsigargin on IRS-1 protein levels during apoptosis.
  • To elucidate the mechanism of IRS-1 regulation in this cellular model.

Main Methods:

  • Utilized a human prostate epithelial cell line.
  • Applied thapsigargin to induce apoptosis.
  • Employed calpain, caspase, and proteasome inhibitors.
  • Assessed protein levels of IRS-1 and other signaling molecules (IGF-I receptor, Akt, Erk, Shc).
  • Performed co-immunoprecipitation to detect protein complexes.

Main Results:

  • Thapsigargin treatment decreased IRS-1 protein levels during apoptosis.
  • Calpain inhibition prevented IRS-1 degradation and apoptosis.
  • Caspase and proteasome inhibitors did not maintain IRS-1 levels.
  • IRS-1 degradation was specific, as other IGF-I pathway proteins remained unaffected.
  • IRS-1 and calpain were found in associated protein complexes.

Conclusions:

  • Calpain activation is a critical mediator of thapsigargin-induced apoptosis in prostate epithelial cells.
  • IRS-1 protein is a direct or indirect substrate for calpain during this apoptotic process.
  • Targeting calpain may offer a therapeutic strategy to prevent apoptosis in relevant cellular contexts.

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