Molecular Determinants of Mossy Fiber Presynaptic Channelopathies in Epilepsy

描述（由申请人提供）：癫痫是一组不同的阵发性疾病，与遗传性或获得性离子通道和/或神经递质受体功能障碍有关，即所谓的“通道病”。海马苔藓纤维发生分子和结构重排在人类和实验的内侧颞叶癫痫（MTLE）。最近的数据显示，癫痫大鼠苔藓纤维中II组代谢性谷氨酸受体（mGluR II）和大电导Ca2+激活钾通道（BK通道）都有明显的下调。在正常大脑中，突触前自身受体mGluR II的“反馈”激活与其他离子通道（即BK通道）一起减弱过度的兴奋性传递。因此，mGluR II和BK通道的突触前缺陷可能在癫痫发生中起主要作用。本项目的具体目的是：(1)验证癫痫大鼠苔藓纤维中mGluR II和BK通道下调与颗粒细胞中类似mRNA转录缺陷和剪接变异体异常表达相关的假设；(2)在实验性MTLE中验证癫痫诱导的mGluR II和BK通道下调影响突触前功能并加剧苔藓纤维- ca3锥体细胞突触兴奋性传递的假设；(3)确定mGluR II和BK通道是否可以减弱MTLE大鼠模型中新“复发”的苔藓纤维颗粒细胞突触的过度兴奋传递。现代技术的结合将用于研究突触前机制的控制与慢性癫痫大鼠。这些方法将包括组织和癫痫监测、单细胞定量实时PCR、颗粒细胞的可视化膜片钳记录以及通过荧光苯乙烯染料FM1-43直接可视化突触前功能。长期目标是破译决定“获得性突触前通道病变”的分子机制，并研究这种突触前功能障碍在MTLE发病机制中的后果。这一建议的数据可能为癫痫的新型治疗干预提供基础。

DESCRIPTION (provided by applicant): Epilepsies are a diverse group of paroxysmal disorders that have been linked to genetic or acquired ion channel and/or neurotransmitter receptor dysfunctions, the so-called "channelopathies." The hippocampal mossy fibers undergo molecular and structural rearrangement in human and experimental mesial temporal lobe epilepsy (MTLE). Recent data revealed a robust down-regulation of both group II metabotropic glutamate receptors (mGluR II) and the large conductance Ca2+activated potassium channel (BK channels) in mossy fibers of epileptic rats. In the normal brain, "feedback" activation of presynaptic autoreceptor mGluR II in concert with other ion channels (i.e., BK channels) attenuates excessive excitatory transmission. Hence, presynaptic deficit in mGluR II and BK channels may play a major role in epileptogenesis. The specific aims of this project are: (1) to test the hypothesis that down-regulation of mGluR II and BK channels in mossy fiber of epileptic rats correlates with similar deficit in mRNA transcripts and abnormal expression of splice variants in granule cells; (2) to test the hypothesis that seizure-induced down-regulation of mGluR II and BK channels affects presynaptic function and exacerbates excitatory transmission at mossy fiber-CA3 pyramidal cell synapses in an experimental MTLE; and (3) to determine whether mGluR II and BK channels can attenuate excessive excitatory transmission at newly "recurrent" mossy fiber-granule cell synapses in a rat model of MTLE. A combination of modern techniques will be used to study presynaptic mechanisms in control versus chronically epileptic rats. Such approaches will include tissue and seizure monitoring, single-cell quantitative real-time PCR, visualized patch-clamp recordings from granule cells and direct visualization of the presynaptic function via the fluorescent styryl dye FM1-43. The long-term goal is to decipher the molecular mechanisms determining "acquired presynaptic channelopathies" and to investigate the consequences of such presynaptic dysfunction in the pathogenesis of MTLE. Data from this proposal may provide the foundation for novel therapeutic interventions for epilepsy.