Fukuchi Mamoru, Kirikoshi Yuya, Mori Atsumi, Eda Reika, Ihara Daisuke, Takasaki Ichiro, Tabuchi Akiko, Tsuda Masaaki
Department of Biological Chemistry, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
Division of Molecular Genetics Research, Life Science Research Center, University of Toyama, Toyama, Japan.
J Neurochem. 2014 Oct;131(2):134-46. doi: 10.1111/jnc.12801. Epub 2014 Jul 18.
Although the excitatory action of GABA has been shown to activate the expression of brain-derived neurotrophic factor (BDNF), its molecular mechanisms remain unclear. Using cultured rat cortical cells, we here demonstrated that GABA induced Bdnf mRNA expression mainly via L-type voltage-dependent Ca(2+) channels (L-VDCC) at the early stage and inhibited it at the late stage of the culture, which corresponded to the excitatory and inhibitory states of cortical cells. The excitatory GABA-induced Bdnf mRNA expression was controlled by multiple Ca(2+) signaling pathways including Ca(2+) /calmodulin-dependent protein kinase (CaMK), mitogen-activated protein kinase (MAPK) and calcineurin (CN). The Bdnf-promoter IV (Bdnf-pIV) was activated by GABA, mainly via cAMP-response element (CRE)/CREB, and this was prevented by the over-expression of a dominant negative CREB. The nuclear translocation of CREB-regulated transcriptional coactivator 1 (CRTC1) was selectively induced by the GABA-induced CN pathway to activate Bdnf-pIV. On the other hand, GABA-induced Gal4-CREB-dependent transcription, which was controlled by multiple Ca(2+) signaling pathways, was prevented when the serine at position 133 of Gal4-CREB was mutated to alanine. Taken together, the excitatory action of GABA transcriptionally activated Bdnf expression through the combination of nuclear-localized CRTC1 and phosphorylated CREB in immature cortical cells, and may be the molecular mechanisms underlying Bdnf expression to control neuronal development. We demonstrated that GABA induced Bdnf expression at the early stage of the culture, in which GABA exerted its excitatory action. The excitatory GABA-induced Bdnf expression was controlled by multiple Ca(2+) signaling pathways evoked via L-VDCC. Both the CREB coactivator, CRTC1 and CREB phosphorylation participated in excitatory GABA-induced Bdnf transcription. Our present study indicates the mechanism underlying the excitatory GABA-induced Bdnf expression in immature neurons and provide new insights into molecular mechanisms underlying Bdnf expression to control neuronal development.
尽管γ-氨基丁酸（GABA）的兴奋性作用已被证明可激活脑源性神经营养因子（BDNF）的表达，但其分子机制仍不清楚。我们利用培养的大鼠皮质细胞证明，在培养早期，GABA主要通过L型电压依赖性钙通道（L-VDCC）诱导Bdnf mRNA表达，而在培养后期则抑制其表达，这与皮质细胞的兴奋和抑制状态相对应。兴奋性GABA诱导的Bdnf mRNA表达受多种钙信号通路调控，包括钙/钙调蛋白依赖性蛋白激酶（CaMK）、丝裂原活化蛋白激酶（MAPK）和钙调神经磷酸酶（CN）。Bdnf启动子IV（Bdnf-pIV）被GABA激活，主要通过环磷酸腺苷反应元件（CRE）/CREB，而显性负性CREB的过表达可阻止这种激活。CREB调节的转录共激活因子1（CRTC1）的核转位由GABA诱导的CN途径选择性诱导，以激活Bdnf-pIV。另一方面，当Gal4-CREB第133位丝氨酸突变为丙氨酸时，GABA诱导的Gal4-CREB依赖性转录被阻止，该转录受多种钙信号通路调控。综上所述，GABA的兴奋性作用通过未成熟皮质细胞中核定位的CRTC1和磷酸化的CREB的组合转录激活Bdnf表达，这可能是Bdnf表达控制神经元发育的分子机制。我们证明，在培养早期，GABA在发挥其兴奋性作用时可诱导Bdnf表达。兴奋性GABA诱导的Bdnf表达受L-VDCC引发的多种钙信号通路调控。CREB共激活因子CRTC1和CREB磷酸化均参与兴奋性GABA诱导的Bdnf转录。我们目前的研究揭示了未成熟神经元中兴奋性GABA诱导Bdnf表达的机制，并为Bdnf表达控制神经元发育的分子机制提供了新的见解。
