Department of Biology, University of Southern California, Los Angeles, California 90089, USA.
J Neurosci. 2013 Sep 4;33(36):14579-90. doi: 10.1523/JNEUROSCI.2108-13.2013.
In response to NMDA receptor stimulation, CaMKIIα moves rapidly from a diffuse distribution within the shafts of neuronal dendrites to a clustered postsynaptic distribution. However, less is known about CaMKIIα localization and trafficking within neuronal somata. Here we use a novel recombinant probe capable of labeling endogenous CaMKIIα in living rat neurons to examine its localization and trafficking within the somata of cortical neurons. This probe, which was generated using an mRNA display selection, binds to endogenous CaMKIIα at high affinity and specificity following expression in rat cortical neurons in culture. In ∼45% of quiescent cortical neurons, labeled clusters of CaMKIIα 1-4 μm in diameter were present. Upon exposure to glutamate and glycine, CaMKIIα clusters disappeared in a Ca(2+)-dependent manner within seconds. Moreover, minutes after the removal of glutamate and glycine, the clusters returned to their original configuration. The clusters, which also appear in cortical neurons in sections taken from mouse brains, contain actin and disperse upon exposure to cytochalasin D, an actin depolymerizer. In conclusion, within the soma, CaMKII localizes and traffics in a manner that is distinct from its localization and trafficking within the dendrites.
在 NMDA 受体刺激下，CaMKIIα 迅速从神经元树突轴突中的弥散分布转变为簇状突触后分布。然而，关于 CaMKIIα 在神经元胞体中的定位和运输知之甚少。在这里，我们使用一种新型的重组探针，能够标记活鼠神经元中的内源性 CaMKIIα，以研究其在皮质神经元胞体中的定位和运输。该探针是使用 mRNA 显示选择生成的，在大鼠皮质神经元培养物中表达后，能够以高亲和力和特异性与内源性 CaMKIIα 结合。在约 45%的静止皮质神经元中，存在直径为 1-4μm 的标记 CaMKIIα 簇。在暴露于谷氨酸和甘氨酸后，CaMKIIα 簇在几秒钟内以 Ca(2+)依赖性方式消失。此外，在谷氨酸和甘氨酸去除后几分钟，簇恢复到其原始构象。这些簇在取自小鼠大脑的切片中的皮质神经元中也存在，包含肌动蛋白，并在肌动蛋白解聚剂细胞松弛素 D 暴露时分散。总之，在胞体中，CaMKII 的定位和运输方式与其在树突中的定位和运输方式明显不同。
