Ischemia-elicited Oxidative Modulation of Ca2+/Calmodulin-dependent Protein Kinase II

Abstract

Ca 2؉ /calmodulin (CaM)-dependent protein kinase II (CaMKII) plays a critical role in neuronal signal transduction and synaptic plasticity. Here, we showed that this kinase was very susceptible to oxidative modulation. Treatment of mouse brain synaptosomes with H 2 O 2 , diamide, and sodium nitroprusside caused aggregation of CaMKII through formation of disulfide and non-disulfide linkages, and partial inhibition of the kinase activity. These CaMKII aggregates were found to associate with the post synaptic density. However, treatment of purified CaMKII with these oxidants did not replicate those effects observed in the synaptosomes. Using two previously identified potential mediators of oxidants in the brain, glutathione disulfide S-monoxide (GS-DSMO) and glutathione disulfide S-dioxide (GS-DSDO), we showed that they oxidized and inhibited CaMKII in a manner partly related to those of the oxidanttreated synaptosomes as well as the ischemia-elicited oxidative stress in the acutely prepared hippocampal slices. Interestingly, the autophosphorylated and activated CaMKII was relatively refractory to GS-DSMO-and GS-DSDO-mediated aggregation. Short term ischemia (10 min) caused a depression of basal synaptic response of the hippocampal slices, and re-oxygenation (after 10 min) reversed the depression. However, oxidation of CaMKII remained at above the pre-ischemic level throughout the treatment. Oxidation of CaMKII also prevented full recovery of CaMKII autophosphorylation after re-oxygenation. Subsequently, the high frequency stimulation-mediated synaptic potentiation in the hippocampal CA1 region was significantly reduced compared with the control without ischemia. Thus, ischemia-evoked oxidation of CaMKII, probably via the action of glutathione disulfide S-oxides or their analogues, may be involved in the suppression of synaptic plasticity.Ca 2ϩ /calmodulin (CaM) 2 -dependent protein kinase II (CaMKII) is one of the major Ca 2ϩ -sensing enzymes important in transducing neuronal, hormonal, and electrical signals in brain, heart, and other tissues. In the central nervous system, CaMKII plays a pivotal role in the facilitation of synaptic plasticity, learning, and memory and in activity-dependent developmental processes (1). CaMKII holoenzyme is a dodecamer composed of two stacked hexameric rings, in which each catalytic/regulatory domain from the upper ring interacts with the equivalent catalytic/regulatory domain in the lower ring by an antiparallel coiled-coil, which resides in regulatory domains (2). Binding of Ca 2ϩ /CaM to the regulatory domain separates the dimer pair and causes the exposure of Thr-286 or Thr-287 (within ␣ or ␤ subunit) for phosphorylation by another catalytic domain in the same ring. This inter-subunit phosphorylation of Thr-286/287 converts the kinase into a high affinity binding protein for Ca 2ϩ /CaM, and the kinase becomes an activatorindependent autonomous enzyme (3). The autophosphorylation also leads to increased affinity of the kinase for several proteins near the sites of elevated Ca 2...

Age-related regulation of excitation–contraction coupling in rat heart

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Interplay Between Calcium and Reactive Oxygen/Nitrogen Species: An Essential Paradigm for Vascular Smooth Muscle Signaling

“…In rat pituitary tumour GH3 cells, nNOS-dependent increases in NO resulted in the S-nitrosylation of cysteine residues on CaMKIIa suppressing CaMKIIa's activity and function (158). A study done with mouse synaptosomes revealed that CaMKII is oxidized under ischemic conditions and that this oxidation attenuated CaMKII activity by inducing disulfide-and nondisulfide-dependent aggregations (153). Taken together, these reports indicate that CaMKII is susceptible to direct oxidation that has both positive and negative consequences.…”

Influence of Viral Vector–Mediated Delivery of Superoxide Dismutase and Catalase to the Hippocampus on Spatial Learning and Memory During Aging

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