Astroglial Glutamate Transporters, Energetics, and Mitochondria

星形胶质细胞谷氨酸转运蛋白、能量学和线粒体

• 批准号: 8401743
• 负责人: Michael Byrne Robinson
• 金额: $ 36.64万
• 依托单位: CHILDREN'S HOSP OF PHILADELPHIA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8401743
• 关键词: ATP phosphohydrolase; Adult; Amino Acids; Anatomy; Astrocytes; Brain; Brain Injuries; Buffers; Cell Death; Cell membrane; Cells; Co-Immunoprecipitations; Complex; Cytoplasm; Data; Disease; Electron Transport Complex III; Environment; Enzymes; Excitatory Amino Acid Transporter 2; Failure; Functional disorder; GLAST Protein; Glucose; Glutamate Metabolism Pathway; Glutamate Receptor; Glutamate Transporter; Glutamates; Glutamine; Glycolysis; Goals; Hippocampus (Brain); Image; Immunoprecipitation; Individual; Link; Mass Spectrum Analysis; Measures; Metabolism; Mitochondria; Mitochondrial Proteins; Modeling; Molecular; Morphology; Na(+)-K(+)-Exchanging ATPase; Nerve; Nervous system structure; Neuraxis; Neurodegenerative Disorders; Neurodevelopmental Disorder; Neurons; Neurotransmitters; Outer Mitochondrial Membrane; Pathway interactions; Process; Production; Proteins; Publications; Ranvier' s Nodes; Receptor Cell; Recruitment Activity; Recycling; Regulation; Research; Role; Scaffolding Protein; Signal Transduction; Slice; Stroke; Synapses; System; Tertiary Protein Structure; Testing; Vertebral column; base; domain mapping; extracellular; hexokinase; in vivo; nervous system disorder; novel; oxidation; presynaptic; prevent; relating to nervous system; response; scaffold; spatial relationship; stable isotope; tool; transmission process; uptake

DESCRIPTION (provided by applicant): Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system. An extracellular accumulation of glutamate causes excessive activation of glutamate receptors and cell death through excitotoxic mechanisms. Unlike other classical neurotransmitters, that are recycled directly into the presynaptic nerve terminal, most glutamate is cleared by two astroglial glutamate transporters, called GLAST and GLT-1 (or EAAT1 and EAAT2). These transporters maintain very low synaptic concentrations of glutamate, estimated at ~25 nM, in an environment that contains millimolar concentrations of glutamate. These transporters are enriched on the fine processes of astrocytes that sheath synapses. We recently developed physical evidence (co-immunoprecipitation, mass spectrometry, reverse immunoprecipitations) and anatomic evidence (co-localization in individual astrocytes in organotypic slice cultures) that these transporters exst in a complex with the Na+/K+ ATPase, most of the enzymes in glycolysis, and mitochondria. This complex is observed in fine processes of astroglia. In the first aim, we will identify specifi domains of GLT-1 and GLAST that support the interactions/co- compartmentalization. We wish to identify potential scaffolding proteins that may form a linkage between the transporters and mitochondria. As has been observed with mitochondria at synapses or at nodes of Ranvier, we propose that neural activity recruits mitochondria to regions where transporters are enriched. In the second aim, we will study the effects of neuronal activity on this co-compartmentalization and define the mechanisms involved. Finally, we will test the hypothesis that formation of these complexes is required for glutamate-dependent changes in glycolysis and a shift in glutamate metabolism (from conversion to glutamine to glutamate oxidation). Compartmentalization of the astroglial glutamate transporters with these proteins and mitochondria provides an opportunity to spatially match energy production and buffering capacity. It also has implications for disposition of the glutamate. Therefore, our proposed research will impact our understanding of fundamental aspects of glutamate handling and metabolism. They will also define a novel molecular mechanism that matches astroglial energetic demands to changes in neuronal activity. PUBLIC HEALTH RELEVANCE: For approximately two decades, it has been clear that failure to clear glutamate contributes to the brain damage observed in stroke, neurodevelopmental disorders, and neurodegenerative diseases. This failure to clear glutamate occurs, at least in part, because of impaired energy mobilization. Our long-term goal is to understand how extracellular glutamate is controlled so that it will be possible to intervene and prevent the debilitating effects of these disorders.

描述(申请人提供)：谷氨酸是哺乳动物中枢神经系统中主要的兴奋性神经递质。细胞外谷氨酸的蓄积通过兴奋性毒性机制导致谷氨酸受体的过度激活和细胞死亡。与其他经典的神经递质直接循环进入突触前神经末梢不同，大多数谷氨酸是由两种星形胶质谷氨酸转运体GLAST和GLT-1(或EAAT1和EAAT2)清除的。这些转运蛋白在含有毫米级谷氨酸的环境中维持非常低的突触谷氨酸浓度，估计为~25 nM。这些转运蛋白丰富地存在于覆盖突触的星形胶质细胞的精细突起中。我们最近发展了物理证据(免疫共沉淀、质谱学、反向免疫沉淀)和解剖学证据(在器官型切片培养中单个星形胶质细胞的共同定位)，证明这些转运蛋白与Na+/K+ATPase和线粒体存在一个复合体。这种复合体见于星形胶质细胞的细小突起。在第一个目标中，我们将识别支持相互作用/共划分的GLT-1和GLAST的特定结构域。我们希望确定潜在的支架蛋白，这些蛋白可能在转运蛋白和线粒体之间形成联系。正如已经观察到的突触或Ranvier结节上的线粒体，我们认为神经活动将线粒体招募到转运蛋白丰富的区域。在第二个目标中，我们将研究神经元活动对这种共同区划的影响，并确定涉及的机制。最后，我们将验证这样一个假设，即这些复合体的形成是糖酵解中依赖谷氨酸的变化和谷氨酸代谢转变(从转化为谷氨酰胺到谷氨酸氧化)所必需的。星形胶质细胞谷氨酸转运体与这些蛋白质和线粒体的分隔提供了一个在空间上匹配能量产生和缓冲能力的机会。它对谷氨酸的处理也有影响。因此，我们提出的研究将影响我们对谷氨酸处理和代谢的基本方面的理解。他们还将定义一种新的分子机制，使星形胶质细胞的能量需求与神经元活动的变化相匹配。 公共卫生相关性：近20年来，很明显，未能清除谷氨酸会导致中风、神经发育障碍和神经退行性疾病的脑损伤。这种无法清除谷氨酸的现象，至少部分是因为能量动员受损。我们的长期目标是了解细胞外谷氨酸是如何被控制的，以便有可能干预和预防这些疾病的衰弱效应。