mTOR regulation of aberrant neuronal integration and epileptogenesis in epilepsy

 描述（由申请人提供）：目前没有有效的治疗方法来预防高危患者的癫痫。然而，哺乳动物雷帕霉素靶点（mTOR）已成为开发疾病修饰疗法的有前途的分子靶点。mTOR通过信号复合物mTORC 1和mTORC 2调节广泛的细胞过程。mTORC 1信号在癫痫的化学、损伤诱导和遗传模型中增强，这意味着该途径可能参与许多不同形式的疾病。用mTOR拮抗剂雷帕霉素阻断mTOR信号传导似乎具有抗癫痫作用。相反，通过删除上游抑制剂来基因增强mTOR信号传导会导致小鼠自发性癫痫发作。我们实验室最近的工作进一步证明，mTOR抑制剂PTEN的缺失只需要发生在新生海马齿状颗粒细胞（DGC）的一个子集中，就可以产生这种疾病。PTEN基因敲除的DGC发展成癫痫脑的标志性病理学，包括轴突发芽、异位细胞迁移和异常树突形成。由病理性DGC形成的复发性兴奋性连接被认为使海马回路不稳定，促进过度兴奋和癫痫发作。尽管有明确的证据表明，mTOR通路的失调可以导致动物模型中的癫痫和人类中的少数遗传性癫痫病症，但是，mTOR介导获得性癫痫综合征中癫痫发生的证据完全基于相关证据和药物雷帕霉素及其类似物的研究。雷帕霉素被推测通过作用于mTORC 1来抑制癫痫发生，并且作用部位被推测为神经元;但是这些假设尚未被实验证实。 我们假设在颞叶癫痫中，新生DGC中mTORC 1过度激活导致这些神经元异常整合，并且这些异常细胞促进癫痫发生。我们还提出了另一种假设，即成熟的海马和皮质神经元驱动癫痫发生。为了评估mTOR激活在不同神经元群体中的作用，我们将使用条件性、诱导性转基因小鼠策略从新生颗粒细胞或前脑神经元中删除mTOR。为了测试不同mTOR通路成员的作用，我们将分别删除mTORC 1和mTORC 2衔接蛋白raptor和rictor。最后，为了确定这些发现是否可以推广，将在三种不同的癫痫模型中进行研究。总之，这些研究将揭示关键的神经元群体，并确定抗癫痫治疗发展的药物靶点。

 DESCRIPTION (provided by applicant): There are currently no effective therapies for preventing epilepsy in at-risk patients. The mammalian target of rapamycin (mTOR), however, has emerged as a promising molecular target for the development of disease-modifying therapies. mTOR regulates a wide range of cellular processes through the signaling complexes mTORC1 and mTORC2. mTORC1 signaling is enhanced in chemical, injury-induced and genetic models of epilepsy, implying that the pathway could be involved in many different forms of the disease. Blocking mTOR signaling with the mTOR antagonist rapamycin appears to have anti-epileptogenic effects. Conversely, genetically enhancing mTOR signaling by deletion of upstream inhibitors produces spontaneous seizures in mice. Recent work from our lab further demonstrates that deletion of the mTOR inhibitor PTEN need only occur in a subset of newborn hippocampal dentate granule cells (DGCs) to produce the disease. PTEN knockout DGC developed the hallmark pathologies of the epileptic brain, including axon sprouting, ectopic cell migration and aberrant dendrite formation. The recurrent excitatory connections formed by pathological DGC are believed to destabilize the hippocampal circuit, promoting hyperexcitability and seizures. Despite clear evidence that dysregulation of the mTOR pathway can cause epilepsy in animals models and a small number of genetic epilepsy conditions in humans, however, the evidence that mTOR mediates epileptogenesis in acquired epilepsy syndromes is based entirely on correlational evidence and studies with the drug rapamycin and its analogs. Rapamycin is presumed to inhibit epileptogenesis by acting on mTORC1, and the site of action is presumed to be neurons; but these assumptions have not yet been experimentally proven. We hypothesize that in temporal lobe epilepsy, mTORC1 hyperactivation among newborn DGCs causes these neurons to integrate abnormally, and that these abnormal cells promote epileptogenesis. We also propose the alternate hypothesis, that mature hippocampal and cortical neurons drive epileptogenesis. To assess the role of mTOR activation in different neuronal populations, we will use conditional, inducible transgenic mouse strategies to delete mTOR from newborn granule cells or forebrain neurons. To test the role of different mTOR pathway members, we will delete the mTORC1 and mTORC2 adaptor proteins raptor and rictor, respectively. Finally, to determine whether the findings can be generalized, studies will be conducted in three different models of epilepsy. Together, these studies will reveal critical neuronal populations and identify druggable targets for the development of anti-epileptogenic therapies.