title: Nodularin exposure induces SOD1 phosphorylation and disrupts SOD1 co-localization with actin filaments.
abstract: Apoptotic cell death is induced in primary hepatocytes by the Ser/Thr protein phosphatase inhibiting cyanobacterial toxin nodularin after only minutes of exposure. Nodularin-induced apoptosis involves a rapid development of reactive oxygen species (ROS), which can be delayed by the Ca2+/calmodulin protein kinase II inhibitor KN93. This apoptosis model provides us with a unique population of highly synchronized dying cells, making it possible to identify low abundant phosphoproteins participating in apoptosis signaling. Here, we show that nodularin induces phosphorylation and possibly also cysteine oxidation of the antioxidant Cu,Zn superoxide dismutase (SOD1), without altering enzymatic SOD1 activity. The observed post-translational modifications of SOD1 could be regulated by Ca2+/calmodulin protein kinase II. In untreated hepatocytes, a high concentration of SOD1 was found in the sub-membranous area, co-localized with the cortical actin cytoskeleton. In the early phase of nodularin exposure, SOD1 was found in high concentration in evenly distributed apoptotic buds. Nodularin induced a rapid reorganization of the actin cytoskeleton and, at the time of polarized budding, SOD1 and actin filaments no longer co-localized.
authors.affiliation: Department of Molecular Biology, University of Bergen, Bergen N-5020, Norway. linda.hjornevik@mbi.uib.no
authors.forename: Linda V
authors.initials: LV
authors.lastname: Hjørnevik
authors.forename: Lise
authors.initials: L
authors.lastname: Fismen
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Young
authors.forename: Therese
authors.initials: T
authors.lastname: Solstad
authors.forename: Kari E
authors.initials: KE
authors.lastname: Fladmark
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001596:Benzylamines / Q000494:pharmacology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010084:Oxidation-Reduction; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D000096926:Benzenesulfonamides
chemical_list: D001596:Benzylamines; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D010456:Peptides, Cyclic; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D013449:Sulfonamides; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C063998:nodularin; C072105:KN 93; D000096926:Benzenesulfonamides; C000606292:Sod1 protein, rat