Morioka M, Fukunaga K, Nagahiro S, Kurino M, Ushio Y, Miyamoto E
Department of Neurosurgery, Kumamoto University School of Medicine, Japan.
J Neurochem. 1995 May;64(5):2132-9. doi: 10.1046/j.1471-4159.1995.64052132.x.
The exposure of cultured rat hippocampal neurons to 500 microM glutamate for 20 min induced a 55% decrease in the total Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) activity. The Ca(2+)-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.
将培养的大鼠海马神经元暴露于500微摩尔谷氨酸中20分钟，可使总钙/钙调蛋白依赖性蛋白激酶II（CaM激酶II）活性降低55%。CaM激酶II的非钙依赖性活性和自身磷酸化程度的降低与总CaM激酶II活性的变化程度相同，并且这些活性的降低可通过用N-甲基-D-天冬氨酸（NMDA）型受体拮抗剂MK-801预处理以及去除细胞外钙来阻止，但其他类型谷氨酸受体拮抗剂和蛋白酶抑制剂则不能。同样，CaM激酶II活性的降低是由钙离子载体离子霉素诱导的。用抗CaM激酶II抗体进行的免疫印迹分析显示，可溶性部分中该酶的量显著减少，而不溶性部分则呈相反增加；因此，这种转位可能是在谷氨酸处理细胞的过程中诱导产生的。这些结果表明，脑缺血期间释放的谷氨酸通过刺激NMDA受体诱导海马神经元中CaM激酶II活性丧失，并且该酶的失活可能参与了脑缺血后谷氨酸神经毒性的级联反应。
