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Glutamate-Induced Loss of Ca2+/Calmodulin-Dependent Protein Kinase II Activity in Cultured Rat Hippocampal Neurons
Authors:Motohiro Morioka,&dagger   Kohji Fukunaga,Shinji Nagahiro,&dagger  Masahito Kurino,Yukitaka Ushio, &dagger  Eishichi Miyamoto
Affiliation:Departments of Neurosurgery and; Pharmacology, Kumamoto University School of Medicine, Kumamoto, Japan
Abstract:
Abstract: The exposure of cultured rat hippocampal neurons to 500 µ M glutamate for 20 min induced a 55% decrease in the total Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) activity. The Ca2+-independent activity and autophosphorylation of CaM kinase II decreased to the same extent as the changes observed in total CaM kinase II activity, and these decreases in activities were prevented by pretreatment with MK-801, an N -methyl- d -aspartate (NMDA)-type receptor antagonist, and the removal of extracellular calcium but not by antagonists against other types of glutamate receptors and protease inhibitors. Similarly, the decrease in the CaM kinase II activity was induced by a Ca2+ ionophore, ionomycin. Immunoblot analysis with the anti-CaM kinase II antibody revealed a significant decrease in the amount of the enzyme in the soluble fraction, in contrast with the inverse increase in the insoluble fraction; thus, the translocation was probably induced during treatment of the cells with glutamate. These results suggest that glutamate released during brain ischemia induces a loss of CaM kinase II activity in hippocampal neurons, by stimulation of the NMDA receptor, and that inactivation of the enzyme may possibly be involved in the cascade of the glutamate neurotoxicity following brain ischemia.
Keywords:Ca2+/calmodulin-dependent protein kinase II    Glutamate neurotoxicity    Brain ischemia    NMDA receptor    Hippocampus
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