CaM-kinaseII-dependent commitment to microcystin-induced apoptosis is coupled to cell budding, but not to shrinkage or chromatin hypercondensation.
The protein phosphatase inhibitor microcystin-LR (MC) induced hepatocyte apoptosis mediated by the calcium-calmodulin-dependent multifunctional protein kinase II (CaMKII). CaMKII antagonists were added at various times after MC to define for how long the cells depended on CaMKII activity to be committed to execute the various parameters of death. Shrinkage and nonpolarized budding were reversible and not coupled to commitment. A critical commitment step was observed 15-20 min after MC (0.5 microM) addition. After this, CaMKII inhibitors no longer protected against polarized budding, DNA fragmentation, lost protein synthesis capability, and cell disruption. Commitment to chromatin hypercondensation occurred 40 min after MC addition. In conclusion, irreversible death commitment was coupled to polarized budding, but not to shrinkage or chromatin condensation. Antioxidant prevented chromatin condensation when given after the CaMKII-dependent commitment point, suggesting that CaMKII had mediated the accumulation of a second messenger of reactive oxygen species nature.
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Cell Biology Research Group, Section of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway.
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Fladmark
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D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D044950:Flavanones / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D008297:Male; D052998:Microcystins; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D002843:Chromatin; D044950:Flavanones; D052998:Microcystins; D010456:Peptides, Cyclic; C476093:z-Val-Ala-Asp(Ome)-fluoromethylketone; C078588:microcystin; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020169:Caspases; C005274:naringin