High glutamate permeability and distal localization of Best1 channel in CA1 hippocampal astrocyte.
High glutamate permeability and distal localization of Best1 channel in CA1 hippocampal astrocyte.
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DOI：
10.1186/1756-6606-6-54
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发表时间：
2013-12-09
期刊：
影响因子：
3.6
通讯作者：
Lee CJ
中科院分区：
文献类型：
--
作者：
Park H;Han KS;Oh SJ;Jo S;Woo J;Yoon BE;Lee CJ
谷氨酸是主要的神经递质，在大脑中介导兴奋性突触传递的主要形式。从神经元的突触前末端，谷氨酸通过谷氨酸包装囊泡的胞吐释放出来。近年来，星形胶质细胞也通过多种途径释放谷氨酸来调节突触传递。特别是，我们已经表征了一个谷氨酸可渗透的Ca2+激活阴离子通道，该通道由Bestrophin 1基因（Best1）编码，负责Ca2+依赖性，通道介导的星形胶质细胞中谷氨酸释放。Best1通道含有一个大孔，可以很容易地渗透到谷氨酸和GABA等大分子中。在这些研究中，我们获得了HEK293T细胞中异种表达的小鼠Best1和培养的星形胶质细胞中内源性表达的小鼠Best1中谷氨酸对Cl-的通透率。然而，到目前为止，体内原生Best1通道的谷氨酸通透性尚未见报道。在CA1海马星形胶质细胞的全细胞记录中，我们发现gq偶联GPCR激活后Best1通道打开，蛋白酶激活受体1 （PAR1）通过Ca2+增加产生谷氨酸携带的阴离子电流。这种Ca2+引起的谷氨酸介导的阴离子电流不受预处理的抑制剂的缝隙连接半通道或Ca2+激活的K+电导的影响。这种由谷氨酸携带的星形胶质细胞阴离子传导是由CA1海马星形胶质细胞中Best1通道的表达介导的，这是因为shRNA表达敲低Best1可通过PAR-1激活消除星形胶质细胞中的谷氨酸传导。然而，我们发现这些星形胶质细胞的best1介导电流的逆转电位与预测值存在偏差。通过双贴片记录，我们得出逆转电位偏离的原因是由于膜极度泄漏（输入电阻范围为1-3 MΩ），星形细胞过程的长度常数非常低，以及Best1通道定位在突触附近的远端微域。根据离子取代对逆转电位的相对位移，我们估计谷氨酸和Cl-的通透率（Pglutamate/PCl）为0.53。我们的研究表明，Best1位于突触连接附近的微结构域，在体内对谷氨酸具有显著的高通透性，是星形胶质细胞中突出的谷氨酸释放通道，介导脑内各种胶质递质的释放，在调节突触传递中发挥重要作用。
Glutamate is the major neurotransmitter that mediates a principal form of excitatory synaptic transmission in the brain. From the presynaptic terminals of neurons, glutamate is released upon exocytosis of the glutamate-packaged vesicles. In recent years, astrocytes are also known to release glutamate via various routes to modulate synaptic transmission. In particular, we have characterized a glutamate-permeable Ca2+-activated anion channel encoded by Bestrophin 1 gene (Best1) that is responsible for Ca2+-dependent, channel-mediated glutamate release in astrocyte. Best1 channel contains a large pore that is readily permeable to large molecules such as glutamate and GABA. In those studies we obtained permeability ratio of glutamate to Cl- in heterologously expressed mouse Best1 in HEK293T cells and in endogenously expressed mouse Best1 in cultured astrocytes. However, up to now, glutamate permeability of the native Best1 channel in vivo has not been reported. In whole-cell recordings of CA1 hippocampal astrocytes, we found that opening of Best1 channel upon activation of a Gq-coupled GPCR, protease-activated receptor 1 (PAR1) generated the anion current carried by glutamate via Ca2+ increase. This Ca2+-evoked glutamate-mediated anion current was unaffected by pretreatment of the inhibitors for a gap junction hemi-channel or Ca2+-activated K+ conductance. This astrocytic anion conductance carried by glutamate was mediated by Best1 channel expression in CA1 hippocampal astrocytes, because Best1 knock-down by shRNA expression eliminated astrocytic glutamate conductance by PAR-1 activation. However, we found that these astrocytes showed a deviation in reversal potential of Best1-mediated current from the predicted value. By performing dual patch recording, we concluded that the deviation of reversal potential is due to incomplete space clamping arising from extremely leaky membrane (input resistance ranging 1–3 MΩ), very low length constant of astrocytic processes, and the localization of Best1 channel in distal microdomains near synapses. Based on the relative shift of reversal potentials by ion substitutions, we estimated the permeability ratio of glutamate and Cl- (Pglutamate/PCl) as 0.53. Our study shows that Best1, located at the microdomains near the synaptic junctions, has a significantly high permeability to glutamate in vivo, serving as the prominent glutamate-releasing channel in astrocytes, mediating the release of various gliotransmitters in the brain, and playing an important role in modulating synaptic transmission.
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DOI：
10.1523/jneurosci.3193-09.2009
发表时间：
2009-10-14
期刊：
The Journal of neuroscience : the official journal of the Society for Neuroscience
影响因子：
--
作者：
Park H;Oh SJ;Han KS;Woo DH;Park H;Mannaioni G;Traynelis SF;Lee CJ
通讯作者：
Lee CJ
DOI：
10.1073/pnas.0506382102
发表时间：
2005-11-08
影响因子：
11.1
作者：
Takano, T;Kang, J;Nedergaard, M
通讯作者：
Nedergaard, M
影响因子：
2.5
作者：
Bar-Yehuda, Dan;Korngreen, Alon
通讯作者：
Korngreen, Alon
影响因子：
64.5
作者：
Woo, Dong Ho;Han, Kyung-Seok;Lee, C. Justin
通讯作者：
Lee, C. Justin
影响因子：
2.5
作者：
WHITE, JA;SEKAR, NS;KAY, AR
通讯作者：
KAY, AR