Sharma Kamal, Fong Dan K, Craig Ann Marie
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Mol Cell Neurosci. 2006 Apr;31(4):702-12. doi: 10.1016/j.mcn.2006.01.010. Epub 2006 Feb 28.
Reorganization of molecular components represents a cellular mechanism for synaptic plasticity. Dendritic spines, major sites for glutamatergic synapses, compartmentalize dynamic changes in molecular composition. Here, we use fluorescence recovery after photobleaching (FRAP) in cultured hippocampal neurons to show that spine proteins undergo continual exchange with extra-spine pools. Each spine component has a distinctive mobility: calcium/calmodulin activated protein kinase CaMKIIalpha > GluR1 AMPA glutamate receptor > PSD-95 scaffolding protein > NR1 NMDA glutamate receptor. Stimulation of synaptic NMDA receptors by a protocol that induces chemical LTP resulted in a long-lasting reduction in the mobility of spine CaMKIIalpha and an increased mobile fraction but slower kinetics for spine GluR1. Stimulation also increased the resistance of postsynaptic CaMKIIalpha to detergent extraction. These results suggest long-lasting changes in affinity of protein-protein interactions and/or ongoing alterations in exo/endocytosis. Such lasting changes in protein mobility may contribute to maintaining alterations in synaptic efficacy.
分子成分的重组代表了一种突触可塑性的细胞机制。树突棘是谷氨酸能突触的主要部位，它将分子组成的动态变化分隔开来。在这里，我们利用光漂白后荧光恢复（FRAP）技术在培养的海马神经元中进行研究，结果表明树突棘蛋白会与树突棘外的蛋白池持续进行交换。每个树突棘成分都有独特的流动性：钙/钙调蛋白激活蛋白激酶CaMKIIα＞谷氨酸受体1（GluR1）＞突触后致密物-95（PSD-95）支架蛋白＞N-甲基-D-天冬氨酸受体1（NR1）。通过诱导化学性长时程增强（LTP）的方案刺激突触N-甲基-D-天冬氨酸受体，导致树突棘CaMKIIα的流动性长期降低，而树突棘GluR1的可移动部分增加但动力学变慢。刺激还增加了突触后CaMKIIα对去污剂提取的抗性。这些结果表明蛋白质-蛋白质相互作用的亲和力发生了长期变化和/或胞吐/内吞作用持续改变。蛋白质流动性的这种持久变化可能有助于维持突触效能的改变。
