The potent natural toxins microcystin, nodularin, and okadaic acid act rapidly to induce
apoptotic cell death. Here we show that the apoptosis correlates with protein
phosphorylation events and can be blocked by protein kinase inhibitors directed against the
multifunctional Ca 2+/calmodulin-dependent protein kinase II (CaMKII). The inhibitors used
comprised a battery of cell-permeable protein kinase antagonists and CaMKII-directed
peptide inhibitors introduced by microinjection or enforced expression. Furthermore …