AMPAR Function in Synaptic and Extrasynaptic Membranes

AMPAR 在突触和突触外膜中的功能

• 批准号: 10018120
• 负责人: Jacques Wadiche
• 金额: $ 42.31万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10018120
• 关键词: AMPA Receptors; Address; Adult; Affect; Affinity; Agonist; Behavior; Binding; Biological Models; Biophysics; Brain; Brain Diseases; Calcium; Cell membrane; Cells; Cerebellum; Characteristics; Data; Dependence; Development; Disease; Exhibits; Fiber; Frequencies; Fright; Genetic Transcription; Glutamate Receptor; Glutamates; Goals; Image; Interneurons; Knowledge; Ligand Binding; Literature; Location; Mediating; Membrane; Modeling; Neuraxis; Neurons; Pathology; Pattern; Permeability; Pharmacology; Phenotype; Physiology; Polyamines; Property; Proteins; Proxy; Regulation; Resolution; Role; Signal Transduction; Site; Slice; Source; Spermine; Stress; Structure; Structure of molecular layer of cerebellar cortex; Synapses; Synaptic Transmission; System; Testing; Toxin; base; biophysical properties; channel blockers; experience; genetic manipulation; indexing; insight; novel; postsynaptic; presynaptic; prevent; receptor; receptor binding; receptor function; simulation; trafficking; two photon microscopy; two-photon; voltage

AMPA receptors (AMPARs) mediate the majority of excitatory glutamatergic synaptic transmission in the central nervous system. Most AMPARs, once bound to glutamate, allow Na+ and K+ flux across the cell membrane, causing neurons to depolarize. However, AMPARs that lack the GluR2 subunit are also permeable to Ca2+. These Ca2-permeable (CP) AMPARs are highly expressed during development when they are essential for activity-dependent plasticity, and this function persists at some synapses throughout adulthood. A biophysical characteristic known as rectification is commonly used to differentiate CP-AMPARs from Ca2+-impermeable (CI) AMPARs. Whereas CP-AMPARs exhibit strong inward rectification, CI-AMPA receptors display linear current-voltage relationships. Inward rectification of CP-AMPARs results from intracellular polyamines that act as open channel blockers to prevent outward current flux. Thus, inward rectification and sensitivity to antagonists that bind at the polyamine site provide biophysical signatures of AMPAR subunit composition and hence Ca2+ permeability, and these characteristics have been widely used to establish rules of AMPAR subunit plasticity. Molecular layer interneurons of the cerebellum provide a well-established model system for understanding AMPAR localization and trafficking because repetitive synaptic stimulation or a single experience of fear triggers a form of plasticity called subunit-switching wherein CP-AMPARs at synapses are replaced by CI-AMPARs from a pool of extrasynaptic AMPARs. Although rectification index and sensitivity to polyamine site toxins are widely used to distinguish between GluR2-containing and -lacking AMPARs, there are many examples from the literature that show these biophysical properties do not exclusively reflect subunit composition. A separate literature has converged on gating models of AMPARs that include multiple conductance states, but the functional implications are unclear. Now, our preliminary data show that CP-AMPAR rectification and pharmacology are sensitive to factors that regulate AMPAR conductance states, potentially complicating the interpretation of results using these biophysical properties as sole proxies of subunit composition. We propose to understand how the multiple sub-conductance states of AMPARs contribute to the hallmark biophysical properties CP-AMPARs. We will use high resolution Ca2+ imaging, heterologous expression systems and genetic manipulation to understand regulation of CP-AMPAR biophysical properties and use that understanding to critically evaluate CP-AMPAR localization and plasticity in cerebellar molecular layer interneurons. AMPAR subunit composition has important functional consequences, ranging from regulating the ability of postsynaptic cells to precisely follow high-frequency synaptic activity and mediating Ca2+ influx that can trigger plasticity or pathology. Successful completion of the proposed studies will reveal novel properties of AMPARs that are essential for understanding their function within synapses and intact circuits in the normal and diseased brain.

AMPA受体（AMPAR）介导了大多数兴奋性谷氨酸能突触传播 中枢神经系统。大多数AMPAR曾经绑定到谷氨酸，允许跨细胞的Na+和K+通量 膜，导致神经元去极化。但是，缺乏GlUR2亚基的AMPAR也可以渗透 到Ca2+。这些CA2可渗透（CP）AMPAR在开发过程中高度表达 对于活动依赖性的可塑性必不可少，并且该功能在整个成年期都存在一些突触。一个 被称为矫正的生物物理特征通常用于将CP-Ampars与Ca2+可耐受性（CI）AMPAR区分开。 CP-Ampars表现出强大的内向整流，而CI-AMPA受体 显示线性电流 - 电压关系。 CP-AMPAR的内向矫正是由细胞内导致的 充当开放通道阻滞剂的多胺可防止向外电流通量。因此，向内纠正和 对在多胺位点结合的拮抗剂的敏感性提供AMPAR亚基的生物物理特征 成分，因此Ca2+渗透性，这些特征已被广泛用于建立规则 AMPAR亚基可塑性。小脑的分子层中间神经元提供了一个完善的模型 理解AMPAR定位和贩运的系统，因为重复的突触刺激或单个 恐惧的经验触发了一种称为亚基 - 开关的可塑性形式，其中CP-Ampars在突触时为 由来自一系列外部AMPAR的Ci-Ampars取代。虽然纠正指数和对 多胺位点毒素被广泛用于区分含GlUR2的AMPAR， 是文献中显示这些生物物理特性的许多例子并不仅仅反映亚基 作品。单独的文献已汇聚在包括多个的AMPAR的门控模型上 电导状态，但功能含义尚不清楚。现在，我们的初步数据表明，CP-AMPAR的整流和药理学对调节AMPAR电导状态的因素敏感，即 使用这些生物物理特性作为唯一代理，使结果的解释有可能使结果复杂化。 亚基组成。我们建议了解AMPAR的多个亚电导状态如何 有助于Hallmark Biophysical特性CP-Ampars。我们将使用高分辨率Ca2+成像， 异源表达系统和基因操纵以了解CP-Ampar的调节 生物物理特性，并使用该理解来批判性地评估CP-Ampar定位和可塑性 小脑分子层中间神经元。 AMPAR亚基组成具有重要的功能后果， 从调节突触后细胞精确遵循高频突触活动的能力和 介导Ca2+流入，可以触发可塑性或病理。成功完成拟议的研究将 揭示AMPAR的新型特性，这些特性对于理解突触中的功能至关重要 正常和患病的大脑中完整的电路。