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Assessment of Mitochondrial Functions and Cell Viability in Renal Cells Overexpressing Protein Kinase C Isozymes
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Tyrosine phosphorylation of protein kinase Cdelta is essential for its apoptotic effect in response to etoposide

Michal Blass1, Ilana Kronfeld, Gila Kazimirsky

  • 1Gonda (Goldschmied) Medical Diagnosis Research Center, Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel.

Molecular and Cellular Biology
|December 12, 2001
PubMed

Insights

Protein kinase Cdelta (PKCdelta) promotes etoposide-induced apoptosis in C6 glioma cells. Tyrosine phosphorylation of PKCdelta, particularly at tyrosine 64 and 187, is crucial for this cell death pathway.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Protein kinase Cdelta (PKCdelta) plays a role in cellular apoptosis.
  • C6 glioma cells are a model for brain tumors.
  • Etoposide is a chemotherapy drug that induces DNA damage and apoptosis.

Purpose of the Study:

  • To investigate the role of PKCdelta in etoposide-induced apoptosis of C6 glioma cells.
  • To identify the specific mechanisms by which PKCdelta mediates apoptosis.
  • To explore the significance of PKCdelta tyrosine phosphorylation in this process.

Main Methods:

  • Overexpression of PKCdelta and its mutants in C6 glioma cells.
  • Treatment with etoposide and selective PKCdelta inhibitors (rottlerin).
  • Cell cycle analysis, Western blotting for apoptosis markers and protein cleavage, and use of PKC chimeras and mutants.

Main Results:

  • Etoposide induced apoptosis and G(1)/S cell cycle arrest in C6 cells.
  • PKCdelta overexpression enhanced etoposide-induced apoptosis; rottlerin and dominant-negative PKCdelta reduced it.
  • Etoposide triggered PKCdelta nuclear translocation, caspase-dependent cleavage, and required both regulatory and catalytic domains for apoptosis. Tyrosine phosphorylation, especially at Tyr64 and Tyr187, was critical, as mutating these sites reduced apoptosis and caspase activation.

Conclusions:

  • PKCdelta is a key mediator of etoposide-induced apoptosis in C6 glioma cells.
  • Tyrosine phosphorylation of PKCdelta, particularly at Tyr64 and Tyr187, is essential for its pro-apoptotic function.
  • These findings highlight PKCdelta signaling as a potential therapeutic target in glioma treatment.

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