Takei N, Numakawa T, Kozaki S, Sakai N, Endo Y, Takahashi M, Hatanaka H
Department of Applied Biology, Kyoto Institute of Technology, Sakyo, Kyoto 606, Japan.
J Biol Chem. 1998 Oct 16;273(42):27620-4. doi: 10.1074/jbc.273.42.27620.
There is increasing interest in the involvement of neurotrophins in neural transmission and plasticity. Thus, we investigated the effects of brain-derived neurotrophic factor (BDNF) on glutamate release from cortical neurons. Treatment of cultured cortical neurons with BDNF induced rapid and transient release of glutamate. This effect was suggested to be mediated by TrkB activation because K252a inhibited the release of glutamate and BDNF phosphorylated TrkB within 30 s. BDNF-induced glutamate release was observed even when using Ca2+-free assay buffer but was inhibited by BAPTA-AM, a cell-permeable Ca2+ chelator. Therefore, BDNF-induced glutamate release was independent of extracelluar Ca2+ but dependent on intracellular Ca2+. Because normal neurotransmitter release is exocytotic, the involvement of the exocytotic pathway in BDNF-induced glutamate release was examined. As botulinum toxin is known to cleave exocytosis-associated proteins, thereby inhibiting exocytosis, it was applied to neurons prior to the release assay. Although botulinum toxin B cleaved VAMP2 and inhibited Ca2+-triggered glutamate release, it did not inhibit the BDNF-induced release of glutamate. These results strongly suggested that BDNF induces rapid and transient release of glutamate from cortical neurons through a non-exocytotic pathway.
神经营养因子在神经传递和可塑性中的作用越来越受到关注。因此，我们研究了脑源性神经营养因子（BDNF）对皮质神经元谷氨酸释放的影响。用BDNF处理培养的皮质神经元可诱导谷氨酸快速短暂释放。这种效应被认为是由TrkB激活介导的，因为K252a抑制了谷氨酸的释放，且BDNF在30秒内使TrkB磷酸化。即使使用无钙测定缓冲液，也观察到BDNF诱导的谷氨酸释放，但被细胞可渗透的钙螯合剂BAPTA-AM抑制。因此，BDNF诱导的谷氨酸释放不依赖于细胞外钙，但依赖于细胞内钙。由于正常的神经递质释放是通过胞吐作用进行的，因此研究了胞吐途径在BDNF诱导的谷氨酸释放中的作用。由于已知肉毒杆菌毒素可切割与胞吐作用相关的蛋白质，从而抑制胞吐作用，因此在释放测定前将其应用于神经元。虽然肉毒杆菌毒素B切割了VAMP2并抑制了钙触发的谷氨酸释放，但它并没有抑制BDNF诱导的谷氨酸释放。这些结果强烈表明，BDNF通过非胞吐途径诱导皮质神经元快速短暂释放谷氨酸。
