Nakano Midori, Takagi Norio, Takagi Keiko, Funakoshi Hiroshi, Matsumoto Kunio, Nakamura Toshikazu, Takeo Satoshi
Department of Molecular and Cellular Pharmacology, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan.
Exp Neurol. 2007 Oct;207(2):195-202. doi: 10.1016/j.expneurol.2007.06.007. Epub 2007 Jun 26.
Hepatocyte growth factor (HGF) and its receptor are expressed in various regions of the brain and have protective effects against excitotoxic injuries. However, their effects on synapse formation remain to be elucidated. To determine whether HGF has the ability to alter synaptic function during development, we investigated changes in the number of synapse detected by double immunostaining for NMDA receptor subunits and a presynaptic marker in cultured young hippocampal neurons. Whereas application of HGF increased the number of cluster of synapsin, a presynaptic protein, the clusters of NMDA receptor subunits NR1 and NR2B were not altered. Interestingly, colocalization of PSD-95, a scaffolding protein of the receptor, with synapsin was increased by HGF treatment without a change in the total amount of it. In addition, we investigated the expression of surface NMDA receptor, neuroligin, and neurexin, which were assessed by use of a cell-surface biotinylation assay. The application of HGF did not change the surface expression of these proteins. Furthermore, we determined the release of glutamate in response to depolarization. Treatment with HGF promoted depolarization-evoked release of glutamate. These results suggest that HGF modulates the expression of the scaffolding protein of the NMDA receptor at the synapse and promotes maturation of excitatory synapses in young hippocampal neurons.
肝细胞生长因子（HGF）及其受体在大脑的各个区域表达，并对兴奋性毒性损伤具有保护作用。然而，它们对突触形成的影响仍有待阐明。为了确定HGF在发育过程中是否具有改变突触功能的能力，我们通过对培养的年轻海马神经元中的NMDA受体亚基和突触前标记物进行双重免疫染色，研究了检测到的突触数量的变化。虽然应用HGF增加了突触前蛋白突触素的簇数量，但NMDA受体亚基NR1和NR2B的簇数量没有改变。有趣的是，受体的支架蛋白PSD-95与突触素的共定位通过HGF处理而增加，但其总量没有变化。此外，我们研究了通过细胞表面生物素化测定评估的表面NMDA受体、神经连接蛋白和神经突触素的表达。HGF的应用没有改变这些蛋白的表面表达。此外，我们确定了去极化时谷氨酸的释放。HGF处理促进了去极化诱发的谷氨酸释放。这些结果表明，HGF调节突触处NMDA受体支架蛋白的表达，并促进年轻海马神经元中兴奋性突触的成熟。
