GABA transporter type 1 (GAT1) function in epilepsy

GABA 转运蛋白 1 型 (GAT1) 在癫痫中的功能

• 批准号: 8243464
• 负责人: Christopher Bruce Ransom
• 金额: --
• 依托单位: VA PUGET SOUND HEALTHCARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8243464
• 关键词: 3-aminobutyric acid; Acute; Affect; Afghanistan; Aging; American; Animals; Anions; Anticonvulsants; Antiepileptic Agents; Biological Assay; Brain; Caring; Cell physiology; Characteristics; Chemicals; Conflict (Psychology); Connexins; Data; Disease; Dose; Down-Regulation; Drug effect disorder; Electric Stimulation; Electroconvulsive Shock; Epilepsy; Extracellular Space; Failure; Frequencies; GABA Transporter 1; GABA transporter; Genetic; High Pressure Liquid Chromatography; Hippocampus (Brain); Iraq; Kainic Acid; Knock-out; Measurement; Mediating; Membrane Transport Proteins; Mentorship; Modeling; Molecular; Mus; Neurons; Neurotransmitters; Patients; Pentylenetetrazole; Pharmaceutical Preparations; Process; Publishing; Recurrence; Refractory; Research; Research Personnel; Residual state; Seizures; Severities; Signal Transduction; Slice; Status Epilepticus; Stroke; Surface; Synapses; Synaptic Vesicles; Testing; Therapeutic; Traumatic Brain Injury; Veratridine; Veterans; Vigabatrin; base; design; extracellular; gabapentin; gamma-Aminobutyric Acid; improved; in vivo; neuronal excitability; postsynaptic; receptor; relating to nervous system; research study; response; skills; synaptic inhibition; tiagabine; uptake

DESCRIPTION (provided by applicant): Epilepsy affects nearly 3 million Americans and approximately 30% of these patients continue to have seizures despite treatment with multiple antiepileptic drugs. Improved understanding of the cellular and molecular changes underlying seizures, and antiepileptic drug action, is essential to advance the care of veterans suffering from medically refractory epilepsy. Among the changes seen in epilepsy is a reduction of neuronal membrane transporters for the inhibitory neurotransmitter 3-aminobutyric acid (GABA) [GABA transporter type 1 (GAT1)] (During et al., 1995; Patrylo et al., 2001). Classically, GABA transporters were thought to function by removing GABA from the extracellular space, thereby terminating GABA actions. It is now clear that GABA transporters can also operate in the reverse direction to release GABA into the extracellular space, a process termed nonvesicular release. Nonvesicular GABA release is augmented by neuronal depolarization and alterations of ionic gradients, conditions that exist during epileptic seizures. Nonvesicular GABA release may be particularly important during prolonged seizures when vesicular GABA release at synapses is compromised by reductions in extracellular [Ca2+], GABA packaging into synaptic vesicles is limited by energy failure, and GABA synthesis is stimulated by low [ATP], causing an increase in cytoplasmic [GABA] that favors nonvesicular release (Erecinska et al., 1984; Hablitz and Heinemann, 1987; Allen et al., 2004). This proposal will test the hypothesis that nonvesicular GABA release has an important antiepileptic action and GAT1 downregulation in epilepsy is maladaptive. Specifically, it is hypothesized that the loss of nonvesicular GABA release mediated by GAT1 will exacerbate seizures despite elevated basal concentrations of ambient GABA. Consistent with this, studies on animals with genetic deletion of GABA transporter type 1 [GAT1 knockout (GAT1 KO)] have identified a heightened sensitivity to chemoconvulsants (Chiu et al., 2005). GAT1 function in epilepsy will be evaluated by three specific aims: Specific Aim 1 will test the hypothesis that nonvesicular GABA release in brain slices from GAT1 KO animals is reduced compared to wild type littermates. Specific Aim 2 will test the hypothesis that AEDs that increase GABA concentration or GAT1 surface expression will enhance nonvesicular release from wild type but not GAT1 KO neurons. Specific Aim 3 will test the hypothesis that nonvesicular release mediated by GAT1 affects seizure threshold in vivo and limits seizure frequency/severity in epileptic mice. Identification of changes in nonvesicular release in GAT1 knockout neurons and determination of AED effects on nonvesicular release in Specific Aims 1-2 will provide a basis for interpretation of in vivo data.

描述（由申请人提供）： 癫痫会影响近300万美国人，尽管使用了多种抗癫痫药治疗，但大约30％的患者仍会继续癫痫发作。对癫痫发作的细胞和分子变化以及抗癫痫药物作用的了解，对促进患有医学性难治性癫痫患者的退伍军人至关重要。在癫痫中看到的变化包括抑制性神经递质3-氨基丁酸（GABA）的神经元膜转运蛋白[GABA Transporter 1型（GAT1）]（期间，1995年； Patrylo Lolo等，2001年）。从经典上讲，GABA转运蛋白被认为通过从细胞外空间中去除GABA来起作用，从而终止了GABA作用。现在很明显，GABA转运蛋白也可以在相反的方向上运行，以将GABA释放到细胞外空间中，该过程称为无抗释放的过程。神经元去极化和离子梯度的变化，即癫痫发作期间存在的疾病的改变，无抗GABA的释放得到了增强。在长时间的癫痫发作期间，当囊泡GABA在突触下释放时，非挥发性GABA的释放可能尤其重要等人，1984年； Hablitz和Heinemann，1987；该提案将检验以下假设：非抗性GABA释放具有重要的抗癫痫作用，而癫痫中GAT1下调是不良适应性的。具体而言，假设，尽管基础GABA的基础浓度升高，但由GAT1介导的非抗性GABA释放的损失仍会加剧癫痫发作。与此相一致，对1型GABA转运蛋白遗传缺失的动物[GAT1敲除（GAT1 KO）]已经确定了对化学弹跳剂的敏感性提高（Chiu等，2005）。癫痫中的GAT1功能将通过三个特定目的评估：特定的目标1将检验以下假设：与野生型同窝仔相比，与GAT1 KO动物的脑切片中的无抗GABA释放减少。具体目标2将检验以下假设：增加GABA浓度或GAT1表面表达的AED会增强野生型而非GAT1 KO神经元的非抗氧化释放。特定的目标3将检验以下假设：GAT1介导的非抗性释放会影响体内的癫痫发作阈值，并限制癫痫小鼠的癫痫发作频率/严重程度。鉴定GAT1基因敲除神经元中非逆释放的变化，并确定特定目的1-2中对非抗性释放的AED效应将为解释体内数据提供基础。