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Mixed lineage kinase 3 negatively regulates IKK activity and enhances etoposide-induced cell death

Eric T Cole1, Yu Zhan, Widian F Abi Saab

  • 1Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA.

Biochimica Et Biophysica Acta
|September 29, 2009
PubMed

Insights

Mixed lineage kinase 3 (MLK3) limits IKK activity. Silencing MLK3 protects cells from etoposide-induced death by activating IKK-dependent signaling, revealing a novel role for MLK3 in apoptosis and inflammation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Mixed lineage kinase 3 (MLK3) is a MAP3K regulating MAPK pathways.
  • Nuclear factor kappa B (NF-kappaB) is crucial for inflammation, immunity, and cell survival.

Purpose of the Study:

  • To investigate the role of MLK3 in regulating NF-kappaB signaling and cellular response to apoptotic stimuli.
  • To elucidate the mechanism by which MLK3 influences cell survival and death pathways.

Main Methods:

  • RNA interference (RNAi) and short hairpin RNA (shRNA) were used to silence MLK3 expression in human ovarian cancer and murine fibroblast cells.
  • Inhibition of kappa B kinase (IKK) activity and NF-kappaB-dependent gene transcription were assessed.
  • Apoptotic cell death was induced by etoposide, and cell death markers like PARP cleavage were analyzed.

Main Results:

  • MLK3 silencing reduced IkappaBalpha levels and enhanced basal IKK activity and NF-kappaB transcription.
  • MLK3 depletion conferred resistance to etoposide-induced apoptosis.
  • Overexpression of MLK3 (wild-type or kinase-dead) promoted apoptosis and PARP cleavage.

Conclusions:

  • MLK3 functions to limit IKK activity.
  • Depleting MLK3 protects cells from etoposide-induced death via activation of IKK-dependent signaling.
  • MLK3 plays a significant role in regulating apoptosis and potentially cancer cell survival.

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