Could tuning of the inhibitory tone involve graded changes in neuronal chloride transport?
Could tuning of the inhibitory tone involve graded changes in neuronal chloride transport?
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DOI：
10.1016/j.neuropharm.2015.03.026
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发表时间：
2015-08-01
影响因子：
4.7
通讯作者：
Hormuzdi，Sheriar G.
中科院分区：
文献类型：
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作者：
Titz，Stefan;Sammler，Esther M.;Hormuzdi，Sheriar G.
gabaa和甘氨酸受体的超极化突触抑制依赖于神经元阳离子-氯离子共转运蛋白KCC2的存在。一些转录和转录后机制已被证明可以调节KCC2，从而影响极性和抑制性突触传递的有效性。然而，目前尚不清楚KCC2的调控是否能够使转运体达到不同的活性水平，从而允许神经元调节抑制性突触传递的强度以满足其不断变化的需求。因此，我们研究了磷酸化是否可以使KCC2达到不同水平的[Cl−]iin神经元。我们产生了多种KCC2丙氨酸去磷酸化模拟物，并在培养的海马神经元中使用NH4+诱导的phshifts来量化这些突变体所表现出的KCC2运输活性的速率。为了探索KCC2转运与gaba受体介导的电流振幅之间的关系，我们进行了格拉西啶穿孔贴片记录。egaba和NH4+诱导的phshifshifs之间的相关性使我们能够估计KCC2的激酶/磷酸酶调控可能产生的氯挤出范围。我们的研究结果表明，KCC2转运可以在很大程度上取决于存在于蛋白质上的丙氨酸突变的组合。转运可以增强到足够高的水平，即使在极负静息膜电位和高细胞外K+浓度的神经元中也可能获得超极化gabaresponse。我们的研究结果强调了通过KCC2介导的氯挤压调节抑制音调的重要潜力，并表明细胞信号通路可能联合作用改变KCC2磷酸化/去磷酸化，从而调节突触抑制的强度。
Hyperpolarizing synaptic inhibition through GABAAand glycine receptors depends on the presence of the neuronal cation-chloride-cotransporter protein, KCC2. Several transcriptional and post-transcriptional mechanisms have been shown to regulate KCC2 and thereby influence the polarity and efficacy of inhibitory synaptic transmission. It is unclear however whether regulation of KCC2 enables the transporter to attain different levels of activity thus allowing a neuron to modulate the strength of inhibitory synaptic transmission to its changing requirements. We therefore investigated whether phosphorylation can allow KCC2 to achieve distinct levels of [Cl−]iin neurons. We generated a variety of KCC2 alanine dephosphorylation mimics and used NH4+-induced pHishifts in cultured hippocampal neurons to quantify the rate of KCC2 transport activity exhibited by these mutants. To explore the relationship between KCC2 transport and GABAAreceptor-mediated current amplitudes we performed gramicidine perforated-patch recordings. The correlation between EGABAand NH4+-induced pHishifts enabled an estimate of the range of chloride extrusion possible by kinase/phosphatase regulation of KCC2.Our results demonstrate that KCC2 transport can vary considerably in magnitude depending on the combination of alanine mutations present on the protein. Transport can be enhanced to sufficiently high levels that hyperpolarizing GABAAresponses may be obtained even in neurons with an extremely negative resting membrane potential and at high extracellular K+concentrations. Our findings highlight the significant potential for regulating the inhibitory tone by KCC2-mediated chloride extrusion and suggest that cellular signaling pathways may act combinatorially to alter KCC2 phosphorylation/dephosphorylation and thereby tune the strength of synaptic inhibition.