Loss of cerebellar glutamate transporters EAAT4 and GLAST differentially affects the spontaneous firing pattern and survival of Purkinje cells.
Loss of cerebellar glutamate transporters EAAT4 and GLAST differentially affects the spontaneous firing pattern and survival of Purkinje cells.
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DOI：
10.1093/hmg/ddy169
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发表时间：
2018-08-01
影响因子：
3.5
通讯作者：
Jackson M
中科院分区：
文献类型：
--
作者：
Perkins EM;Clarkson YL;Suminaite D;Lyndon AR;Tanaka K;Rothstein JD;Skehel PA;Wyllie DJA;Jackson M
兴奋性氨基酸转运体缺失(EAATs)与许多人类疾病有关，包括脊髓小脑性共济失调、阿尔茨海默病和运动神经元病。EAAT4和GLAST/EAAT1是两种主要的EAATs，负责维持细胞外低谷氨酸水平和防止小脑的神经毒性，小脑是运动控制必不可少的大脑区域。在这里，使用转基因小鼠，我们确定了EAAT4和GLAST/EAAT1作为浦肯野细胞(PC)自发放电模式的调节器的新的关键角色。我们表明，通过限制mGluR1信号，高EAAT4水平对于限制Zebrin阳性PC固有的异质性激发是必不可少的。此外，发现mGluR1拮抗剂可以恢复EAAT4基因敲除小鼠正常的自发PC活动和运动行为。相反，GLAST/EAAT1的表达需要通过限制NMDA受体的激活来维持EAAT4低表达(Zebrin阴性)PC的正常自发简单棘波活动。阻断NMDA受体活性可恢复GLAST基因敲除小鼠中Zebrin阴性PC的自发活动，并进一步缓解运动缺陷。此外，这两种转运蛋白对PC的存活有不同的影响，Zebrin阴性的PC更容易丢失GLAST/EAAT1，而Zebrin阳性的PC更容易丢失EAAT4。这些发现表明，通过细胞外谷氨酸升高和突触外受体的异常激活而导致的谷氨酸转运体功能障碍可以通过改变自发的PC放电来扰乱小脑的输出。这扩大了我们对小脑性共济失调疾病机制的理解，并建立了EAAT作为各种神经系统疾病恢复内稳态的靶点，目前认为小脑输出改变在这些疾病的发病机制中起着关键作用。
Loss of excitatory amino acid transporters (EAATs) has been implicated in a number of human diseases including spinocerebellar ataxias, Alzhiemer’s disease and motor neuron disease. EAAT4 and GLAST/EAAT1 are the two predominant EAATs responsible for maintaining low extracellular glutamate levels and preventing neurotoxicity in the cerebellum, the brain region essential for motor control. Here using genetically modified mice we identify new critical roles for EAAT4 and GLAST/EAAT1 as modulators of Purkinje cell (PC) spontaneous firing patterns. We show high EAAT4 levels, by limiting mGluR1 signalling, are essential in constraining inherently heterogeneous firing of zebrin-positive PCs. Moreover mGluR1 antagonists were found to restore regular spontaneous PC activity and motor behaviour in EAAT4 knockout mice. In contrast, GLAST/EAAT1 expression is required to sustain normal spontaneous simple spike activity in low EAAT4 expressing (zebrin-negative) PCs by restricting NMDA receptor activation. Blockade of NMDA receptor activity restores spontaneous activity in zebrin-negative PCs of GLAST knockout mice and furthermore alleviates motor deficits. In addition both transporters have differential effects on PC survival, with zebrin-negative PCs more vulnerable to loss of GLAST/EAAT1 and zebrin-positive PCs more vulnerable to loss of EAAT4. These findings reveal that glutamate transporter dysfunction through elevated extracellular glutamate and the aberrant activation of extrasynaptic receptors can disrupt cerebellar output by altering spontaneous PC firing. This expands our understanding of disease mechanisms in cerebellar ataxias and establishes EAATs as targets for restoring homeostasis in a variety of neurological diseases where altered cerebellar output is now thought to play a key role in pathogenesis.