Understanding the temporal regulation of inhibitory synapse depression and elimination in the context of cerebral ischemia

项目摘要/摘要 抑制性突触对于维持正确的神经元兴奋性至关重要，而兴奋性对于高效 电路和正常的大脑功能。神经元兴奋性的改变与多种神经系统疾病有关。 紊乱，包括缺血。基于细胞类型的特定脆弱性，氧气和葡萄糖的缺乏 在包括海马体在内的不同大脑区域观察到的(OGD)导致可能改变的不同效应 神经元的长期功能。海马体是一个特别脆弱的大脑区域， 要么是CA1区延迟性细胞死亡，要么是对延迟性细胞死亡和长期兴奋性转变的抵抗 在CA3区。神经元群体的细胞类型特异性突触改变可能有助于这些 缺血引起的改变。尽管兴奋性突触的变化已经被很好地定义，但我们对 抑制性突触的变化仍然难以捉摸。 抑制性GABAA受体(GABAARs)介导了大脑中大部分的快速突触抑制。这个 突触后GABAAR的数量影响抑制强度；因此，GABAAR往返运输 突触部位或神经元表面是整体抑制性突触强度的重要调节因素。在.期间 在海马神经元中，OGD、GABAARs从神经元表面下调。此外，GABAAR 磷酸化状态影响突触分离或从神经元表面移除受体 在OGD期间，在海马神经元中。然而，调节这些差异的机制在两种突触中 脑缺血损伤后不同易感性脑区的聚集或表面GABAAR表达 仍然没有定义。 在这个项目中，我提出GABAAR去簇化和内吞作用的机制是不同的调节 OGD期间不同神经元群体中基于区域特异性的GABAAR下调的影响 脆弱性。此外，我假设这些细胞类型的特定机制驱动增加的神经元 OGD时突触脱落增加和细胞表面表达减少所致的兴奋性 脆弱神经元群体中的GABAARs。基于此，我计划研究(I)突触的机制 OGD(II)探针对海马锥体神经元GABAAR的去聚集和表面下调作用 时间规则，以确定促进GABAAR损失的事件的顺序流和(Iii)使用In 脑缺血活体模型比较CA1和CA3海马区细胞类型特异性机制 可能根据神经元对OGD的敏感性而进行差异调节。具体地说，我计划调查 磷酸酶在调节GABAAR磷酸化状态促进GABAAR去簇集中的作用 在两个易受伤害的神经元群体中，OGD期间的内吞作用。该项目的成果将确立 在OGD期间，针对GABAAR下调脆弱人群的特定机制，提供了新的 未来治疗干预的目标。

PROJECT SUMMARY/ABSTRACT Inhibitory synapses are crucial for maintaining correct neuronal excitability, which is important for efficient circuitry and proper brain function. Shifts in neuronal excitability have been implicated in a variety of neurological disorders, including ischemia. Based on cell-type specific vulnerabilities, the oxygen and glucose deprivation (OGD) observed in various brain regions including the hippocampus leads to differential effects that may alter neuronal long-term function. The hippocampus is particularly a vulnerable brain region that experiences either delayed cell-death in the CA1 region or resistance to delayed-cell death and shifts in long-term excitability in the CA3 region. Cell-type specific synaptic alterations to neuronal populations may contribute to these ischemic-induced changes. Even though alterations at excitatory synapses are well defined, our knowledge of alterations at the inhibitory synapse remain elusive. Inhibitory GABAA receptors (GABAARs) mediate the majority of fast synaptic inhibition in the brain. The number of postsynaptic GABAARs influences inhibitory strength; therefore, GABAAR trafficking to and from synaptic sites or the neuronal surface is an important regulator of overall inhibitory synaptic strength. During OGD, GABAARs are downregulated from the neuronal surface in hippocampal neurons. Moreover, GABAAR phosphorylation status influences the synaptic declustering or removal of receptors from the neuronal surface during OGD in hippocampal neurons. However, mechanisms that regulate these differences in either synaptic clustering or surface GABAAR expression following an ischemic insult in brain regions with varying susceptibilities remain undefined. In this project, I propose that GABAAR declustering and endocytosis mechanisms are differentially regulated in distinct neuronal populations during OGD to influence GABAAR downregulation based on region-specific vulnerability. Moreover, I hypothesize that these cell-type specific mechanisms drive increased neuronal excitability during OGD due to increase synaptic declustering and decreased surface expression of GABAARs in vulnerable neuronal populations. Based on this, I plan to investigate (i) mechanisms of synaptic GABAAR declustering and surface downregulation in hippocampal pyramidal neurons following OGD (ii) probe the temporal regulation to determine the sequential flow of events promoting GABAAR loss and (iii) use an in vivo model of cerebral ischemia to compare cell-type specific mechanisms in CA1 and CA3 hippocampus that may be differentially regulated based on neuronal susceptibility to OGD. Specifically, I plan to investigate the role of phosphatases in regulating GABAAR phosphorylation state to promote GABAAR declustering and endocytosis during OGD in both vulnerable neuronal populations. The results of this project will establish mechanisms that are specific to GABAAR downregulation in vulnerable populations during OGD, providing novel targets for future therapeutic intervention.