Defects of subcellular glutamate transporter localization in schizophrenia

描述（由申请人提供）：虽然抗精神病药物治疗精神分裂症彻底改变了这种疾病的临床管理，但尽管进行了多次抗精神病药物试验，仍有约三分之一的精神分裂症患者存在持续的阳性症状。最近，出现了治疗精神分裂症的新策略，包括谷氨酸受体的调节，这是一种部分基于死后、成像和临床前研究中谷氨酸传递改变的证据积累而开发的方法。虽然精神分裂症最初的谷氨酸假说集中在NMDA受体功能障碍上，但这一假说已扩展到包括其他谷氨酸受体、转运蛋白和参与谷氨酸传递的酶。精神分裂症中谷氨酸能分子表达变化的尸检结果可能被概念化为重塑谷氨酸突触的功能改变，继发于慢性严重精神疾病的潜在病理生理学和精神药物治疗的终身。我们发现神经胶质谷氨酸转运体在精神分裂症患者中的表达减少，这表明谷氨酸突触的谷氨酸缓冲和再摄取能力发生了改变。谷氨酸转运体通过限制谷氨酸溢出到相邻突触来促进兴奋性神经传递，我们假设兴奋性氨基酸转运体（EAAT）的定位在精神分裂症的皮质丘脑回路中发生改变，从而导致这种疾病的精神病理学。具体来说，我们假设EAAT的细胞特异性定位在精神分裂症中改变。我们还推测，有缺陷的运输和亚细胞定位的EAAT在这种疾病。为了评估这些假设，我们将评估本地化EAAT异构体使用免疫荧光，亚细胞分级，和Western印迹分析在尸检组织中精神分裂症和对照组的主题。我们的研究将集中在丘脑背内侧核和前扣带皮层，这些区域具有密集的相互神经支配，与这种疾病的病理生理学有关。我们还计划评估慢性典型和非典型抗精神病药物治疗对大鼠脑中谷氨酸转运体定位的影响。这些啮齿类动物研究将提供新的数据慢性抗精神病药物治疗对兴奋性突触的组成的影响，并补充我们的尸检结果的解释，因为这些受试者中的大多数都用抗精神病药物治疗。在这组实验的结论，我们将测试的假设，谷氨酸转运蛋白的细胞和亚细胞定位改变精神分裂症，这表明减少突触周围缓冲和谷氨酸的再摄取和增加谷氨酸溢出。这些研究将扩展精神分裂症的谷氨酸假说超越NMDA受体，并为诊断和治疗这种通常具有破坏性的疾病提供新的底物。

DESCRIPTION (provided by applicant): While the treatment of schizophrenia with antipsychotic medications revolutionized the clinical management of this illness, approximately one-third of patients with schizophrenia have persistent positive symptoms despite multiple trials of antipsychotic medicines. Recently, new strategies for the treatment of schizophrenia have emerged, including modulation of glutamate receptors, an approach which was developed, in part, based on an accumulating body of evidence of alterations in glutamate transmission from postmortem, imaging, and preclinical studies. While the initial glutamate hypothesis of schizophrenia was focused on NMDA receptor dysfunction, this hypothesis has been extended to include other glutamate receptors, transporters, and enzymes involved in glutamate transmission. Postmortem findings of changes in the expression of glutamatergic molecules in schizophrenia may be conceptualized as functional alterations of remodeled glutamate synapses, secondary to the underlying pathophysiology of chronic severe mental illness and a lifetime of treatment with psychotropic medications. We have found decreased expression of glial glutamate transporters in subjects with schizophrenia, suggesting that glutamate synapses have alterations in glutamate buffering and reuptake capacity. Glutamate transporters facilitate excitatory neurotransmission by limiting glutamate spillover to adjacent synapses, and we postulate that the localization of excitatory amino acid transporters (EAATs) is altered in corticothalamic circuits in schizophrenia, contributing to the psychopathology of this disease. Specifically, we hypothesize that cell-specific localization of EAATs is altered in schizophrenia. We also hypothesize that there are defects of trafficking and subcellular localization of EAATs in this illness. To evaluate these hypotheses, we will assess the localization of EAAT isoforms using immunofluorescence, subcellular fractionization, and Western blot analysis in postmortem tissue from subjects with schizophrenia and a comparison group. Our studies will focus on the dorsomedial nucleus of the thalamus and the anterior cingulate cortex, regions with dense reciprocal innervation that are implicated in the pathophysiology of this illness. We also plan to assess the effects of chronic typical and atypical antipsychotic treatment on localization of glutamate transporters in the rat brain. These rodent studies will provide novel data on the effects of chronic antipsychotic treatment on the composition of excitatory synapses, and compliment the interpretation of our postmortem findings, since most of these subjects were treated with antipsychotics. At the conclusion of this set of experiments, we will have tested the hypothesis that cellular and subcellular localization of glutamate transporters is altered in schizophrenia, suggesting decreased perisynaptic buffering and reuptake of glutamate and increased glutamate spillover. These studies will extend the glutamate hypothesis of schizophrenia beyond the NMDA receptor and provide new substrates for diagnosis and treatment of this often devastating illness.