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Assessment of Mitochondrial Functions and Cell Viability in Renal Cells Overexpressing Protein Kinase C Isozymes
15:43

Assessment of Mitochondrial Functions and Cell Viability in Renal Cells Overexpressing Protein Kinase C Isozymes

Published on: January 7, 2013

Protein kinase C inhibits singlet oxygen-induced apoptosis by decreasing caspase-8 activation

S Zhuang1, J T Demirs, I E Kochevar

  • 1Wellman Laboratories of Photomedicine, Massachusetts General Hospital, 55 Fruit St., Boston, MA 02114, USA.

Oncogene
|December 26, 2001
PubMed

Insights

Protein kinase C (PKC) activation inhibits singlet oxygen-induced apoptosis by blocking caspase-8 activation, preventing downstream signaling events. This research clarifies the mechanism by which PKC modulates cell death pathways.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Protein kinase C (PKC) activation is known to inhibit apoptosis induced by various stimuli, including singlet oxygen.
  • The precise step at which PKC interferes with apoptotic signaling pathways remains incompletely understood.
  • Previous studies identified caspase-8 and p38 as mediators of singlet oxygen-induced apoptosis in HL-60 cells.

Purpose of the Study:

  • To investigate the influence of PKC activation on the regulation of caspase and p38 pathways initiated by singlet oxygen.
  • To elucidate the specific mechanism by which PKC inhibits singlet oxygen-induced apoptosis.

Main Methods:

  • HL-60 cells were treated with singlet oxygen and/or the PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA).
  • Fas clustering, recruitment of FADD and caspase-8, and caspase-8 binding to aggregated Fas were analyzed.
  • Downstream signaling events, including Bid and caspase-3 cleavage, mitochondrial transmembrane potential, and cytochrome c release, were assessed.
  • The effects of PKC inhibitors (GF109203, H7) and p38 phosphorylation were also evaluated.

Main Results:

  • Singlet oxygen induced Fas clustering and subsequent recruitment of FADD and caspase-8.
  • PKC activation by TPA did not affect caspase-8 binding to aggregated Fas.
  • PKC activation effectively prevented singlet oxygen-induced caspase-8 activation and subsequent downstream signaling, including Bid cleavage, caspase-3 activation, mitochondrial depolarization, and cytochrome c release.
  • Inhibition of PKC reversed the TPA-mediated effects on caspase-3 and caspase-8 cleavage.
  • PKC modulation did not influence p38 phosphorylation.

Conclusions:

  • PKC inhibits singlet oxygen-induced apoptosis primarily by blocking the activation of caspase-8.
  • The inhibitory effect of PKC occurs downstream of Fas aggregation and caspase-8 recruitment but upstream of caspase-8 activation.
  • PKC does not appear to regulate the p38-mediated apoptotic pathway in response to singlet oxygen.

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