Ca2+/calmodulin kinase II translocates in a hippocampal slice model of ischemia

Rat hippocampal slices were exposed to conditions that simulate an ischemic insult, and the subcellular distribution and the enzymatic activity of Ca2+/calmodulin-dependent protein kinase II (CaM kinase) were monitored. Semiquantitative western blots using a monoclonal antibody to the 50-kDa alpha subunit showed that there was a significant redistribution of the enzyme from a supernatant to a pellet fraction after 10 min of an anoxic/aglycemic insult. No significant change in the total amount of CaM kinase enzyme was detected in the homogenates for up to 20 min of exposure to the insult. Ca2+/CaM-dependent enzyme activity did not significantly change in the pellet during the 20-min insult. Supernatant activity decreased throughout the insult. The persistence of Ca2+/CaM-dependent CaM kinase activity in the pellet fraction and the detected movement of enzyme from the supernatant to the pellet indicate that redistribution may be an important mechanism in regulating the cellular location of CaM kinase activity.