Department of Molecular Cell Biology and Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Korea.
J Neurochem. 2010 Jun;113(6):1565-76. doi: 10.1111/j.1471-4159.2010.06713.x. Epub 2010 Mar 29.
Previously, we reported the phosphorylation of moesin induced by electroconvulsive shock in rat brain and by glutamate in immortalized rat hippocampal cells. However, the function of phosphorylated moesin in differentiated neurons is not well understood. In this study, we observed that glutamate induces phosphorylation of ezrin/radixin/moesin proteins (ERM) in cultured hippocampal cells and that phosphorylated ERM localizes at the newly formed filopodia of neurites. The glutamate-induced phosphorylation of ERM is calcium-dependent, and inhibition of protein kinase C abolishes ERM phosphorylation as well as RhoA activation. The inhibitions of RhoA and RhoA kinase also diminishes the glutamate-induced ERM phosphorylation in cultured hippocampal cells. The knock-down of moesin or the inhibition of ERM phosphorylation results in the reduction of glutamate-induced filopodia protrusion and diminishes the increase in active synaptic boutons induced by glutamate treatment. These results indicate that glutamate-induced phosphorylation of ERM proteins in primary cultured differentiated hippocampal neurons is mediated by calcium-dependent protein kinase C, RhoA and RhoA kinase, and the phosphorylated ERM protein is necessary for the formation of filopodial protrusion and may be involved in pre-synaptic trafficking.
先前，我们报道了电休克刺激诱导大鼠脑中以及谷氨酸诱导永生化大鼠海马细胞中 moesin 的磷酸化。然而，磷酸化 moesin 在分化神经元中的功能尚不清楚。在这项研究中，我们观察到谷氨酸诱导培养的海马细胞中 ezrin/radixin/moesin 蛋白（ERM）的磷酸化，并且磷酸化的 ERM 定位于神经突中新形成的丝状伪足。谷氨酸诱导的 ERM 磷酸化是钙离子依赖性的，蛋白激酶 C 的抑制作用可消除 ERM 磷酸化以及 RhoA 的激活。RhoA 和 RhoA 激酶的抑制作用也可减少培养的海马细胞中谷氨酸诱导的 ERM 磷酸化。moesin 的敲低或 ERM 磷酸化的抑制作用导致谷氨酸诱导的丝状伪足突出减少，并减弱了谷氨酸处理诱导的活性突触末梢增加。这些结果表明，在原代培养的分化海马神经元中，谷氨酸诱导的 ERM 蛋白磷酸化是由钙依赖性蛋白激酶 C、RhoA 和 RhoA 激酶介导的，磷酸化的 ERM 蛋白对于丝状伪足的形成是必需的，并且可能参与突触前运输。
