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Nodularin exposure induces SOD1 phosphorylation and disrupts SOD1 co-localization with actin filaments

Linda V Hjørnevik1, Lise Fismen, Fiona M Young

  • 1Department of Molecular Biology, University of Bergen, Bergen N-5020, Norway. linda.hjornevik@mbi.uib.no

Toxins
|December 18, 2012
PubMed

Insights

Cyanobacterial toxin nodularin triggers rapid apoptosis in hepatocytes, involving reactive oxygen species (ROS). Researchers found nodularin modifies antioxidant enzyme SOD1, impacting its cellular location during apoptosis.

Area of Science:

  • Cell Biology
  • Toxicology
  • Biochemistry

Background:

  • Cyanobacterial toxin nodularin induces rapid apoptosis in primary hepatocytes.
  • Apoptosis involves reactive oxygen species (ROS) and can be modulated by Ca2+/calmodulin protein kinase II inhibitors.
  • This synchronized cell death model allows identification of low-abundance phosphoproteins in apoptosis signaling.

Purpose of the Study:

  • To investigate the post-translational modifications of Cu,Zn superoxide dismutase (SOD1) during nodularin-induced apoptosis.
  • To explore the role of Ca2+/calmodulin protein kinase II in regulating SOD1 modifications.
  • To examine the subcellular localization of SOD1 and its relationship with the actin cytoskeleton during apoptosis.

Main Methods:

  • Primary hepatocytes were exposed to nodularin.
  • Reactive oxygen species (ROS) production was monitored.
  • The Ca2+/calmodulin protein kinase II inhibitor KN93 was used.
  • Phosphorylation and cysteine oxidation of SOD1 were analyzed.
  • Immunofluorescence microscopy was employed to study SOD1 and actin cytoskeleton localization.

Main Results:

  • Nodularin induced phosphorylation and cysteine oxidation of SOD1, without affecting its enzymatic activity.
  • These modifications may be regulated by Ca2+/calmodulin protein kinase II.
  • SOD1, initially co-localized with actin cytoskeleton near the membrane, redistributed to apoptotic buds.
  • Nodularin caused actin cytoskeleton reorganization, leading to a loss of co-localization between SOD1 and actin filaments during budding.

Conclusions:

  • Nodularin-induced apoptosis involves specific post-translational modifications of the antioxidant enzyme SOD1.
  • Ca2+/calmodulin protein kinase II is a potential regulator of these SOD1 modifications.
  • SOD1 dynamics and its interaction with the actin cytoskeleton change significantly during nodularin-induced hepatocyte apoptosis.

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