Caputi A, Gardoni F, Cimino M, Pastorino L, Cattabeni F, Di Luca M
Institute of Pharmacological Sciences, University of Milano, Italy.
Eur J Neurosci. 1999 Jan;11(1):141-8. doi: 10.1046/j.1460-9568.1999.00414.x.
The calcium-calmodulin-dependent protein kinase II (CaMKII) subserves activity-dependent plasticity in central neurons. To examine in vivo the implication of CaMKII activity in synaptic plasticity, we used an animal model characterized by developmentally induced targeted neuronal ablation within the cortex and the hippocampus, and showing, at presynaptic level, molecular alterations leading to facilitation of glutamate release in hippocampal synapses (methylazoxymethanol-treated rats, MAM-rats). We report here that at the postsynaptic side, the activity of CaMKII is markedly decreased in MAM-rats when compared to controls, although the concentration of the enzyme in Post Synaptic Density (PSD) is not altered. This effect is confined to PSD-associated CaMKII, as enzyme activity tested in the soluble fraction is unchanged in MAM-rats. In addition, the decreased activity is not due to inhibition by autophosphorylation in specific sites within the calmodulin-binding domain, as preincubation with purified phosphatases 1 and 2A failed to restore CaMKII activity in PSD of MAM-rats. The CaMKII-dependent phosphorylation of NR2A/B subunits of NMDA receptor is lower in MAM-rats when compared to controls (51.77 +/- 7.39% of controls level), as revealed in back-phosphorylation experiments. In addition, a treatment able to restore long-term potentiation (LTP) in hippocampal slices from MAM-rats, e.g. exposure to D-serine, is able to restore CaMKII activity to the control value.
钙/钙调蛋白依赖性蛋白激酶II（CaMKII）在中枢神经元中参与活动依赖性可塑性。为了在体内研究CaMKII活性在突触可塑性中的作用，我们使用了一种动物模型，其特征是在发育过程中诱导皮质和海马内的靶向神经元消融，并在突触前水平显示出导致海马突触中谷氨酸释放促进的分子改变（甲基偶氮甲醇处理的大鼠，MAM大鼠）。我们在此报告，在突触后方面，与对照组相比，MAM大鼠中CaMKII的活性显著降低，尽管突触后致密物（PSD）中该酶的浓度没有改变。这种效应仅限于与PSD相关的CaMKII，因为在MAM大鼠的可溶性部分中测试的酶活性没有变化。此外，活性降低不是由于钙调蛋白结合域内特定位点的自磷酸化抑制，因为用纯化的磷酸酶1和2A预孵育未能恢复MAM大鼠PSD中的CaMKII活性。如反向磷酸化实验所示，与对照组相比，MAM大鼠中NMDA受体NR2A/B亚基的CaMKII依赖性磷酸化较低（为对照组水平的51.77 +/- 7.39%）。此外，一种能够恢复MAM大鼠海马切片中长时程增强（LTP）的处理方法，例如暴露于D-丝氨酸，能够将CaMKII活性恢复到对照值。
