Genetic analysis to determine the functional role of GRID1

遗传分析以确定 GRID1 的功能作用

• 批准号: 10217304
• 负责人: Stephen F Traynelis
• 金额: $ 15.6万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-05 至 2022-04-04
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10217304
• 关键词: AMPA Receptors; Affect; Agonist; Binding; Binding Sites; Brain; Cations; Cell Surface Receptors; Communication; Disease; Distal; Electrophysiology (science); Extracellular Domain; Family member; Frequencies; Gene Family; General Population; Genes; Glutamate Receptor; Glutamates; Glycine; Health; Human; Individual; Ion Channel; Ions; Kainic Acid Receptors; Ligands; Mediating; Modality; Molecular Conformation; Mutation; N-Methyl-D-Aspartate Receptors; N-Methylaspartate; NMDA receptor A1; Neuraxis; Neurologic; Neurons; Patients; Physiological; Play; Population; Population Genetics; Process; Property; Proteins; Regulation; Role; Serine; Signal Transduction; Site; Synaptic Receptors; Synaptic Transmission; System; Testing; Variant; constitutive active receptor; delta receptors; design; dimer; experimental study; extracellular; falls; genetic analysis; insight; kainate; mutant; nervous system disorder; neuropathology; presynaptic; receptor; receptor binding; response; scaffold; synaptogenesis; web site

Summary The glutamate receptor gene family encodes AMPA, kainate, and NMDA receptors, which mediate excitatory synaptic transmission in the central nervous system. Two additional gene family members, GRID1 and GRID2, encode the enigmatic delta receptor GluD1 and GluD2 subunits, which can bind D-serine but do not appear to activate conventional signaling systems. There are four functional effects known for delta receptors: (1) Both delta receptors (GluD1 and GluD2) are activated when certain mutations occur in the transmembrane helices, which convert a non-gating receptor into a channel that is constitutively open, producing a tonic inward current. In addition, chimeric receptors in which the glutamate binding domain from a kainate or AMPA receptor replaces the analogous D-serine binding domain for GluD1 and GluD2 can be activated by glutamate, suggesting that the highly specialized machinery needed to convert agonist binding into pore opening is conserved in delta GluD1 receptors. (2) The binding of D-serine to GluD1 receptors harboring a TM3 mutation that renders them constitutively active can close the channel, raising that possibility that D-serine binding produces meaningful conformational changes with unknown physiological roles in WT receptors. (3) Ca2+ binding to a site at the dimer interface between two adjacent D-serine binding domains potentiates constitutive current in mutant receptors, suggesting Ca2+ could regulate GluD1 conformation and function. (4) The distal extracellular domain serves as a ligand for presynaptic Cbln2 and neurexin, which can alter synapse formation. Whereas Cbln2 and neurexin binding to GluD1 appears to be critical, it remains unclear whether channel gating, D-serine binding, or Ca2+ regulation of GluD1 play important roles in brain. A unique power of population genetics is that it can identify key functions of a protein in an unbiased manner. GRID1 is one of the least tolerant genes in the body, falling in the top 2 percentile for lacking variation, suggesting it plays essential roles. Consistent with this idea, patients with neurological conditions have been identified with missense variants in GRID1 that are absent in the general population. We will evaluate the effects of disease-associated variants in addition to well-tolerated variants commonly observed in the healthy population on three modalities associated with GRID1 function—constitutive activation, D-serine binding, Ca2+ binding. If any of these functional attributes are important, then we expect to find disease- associated variants that perturb them, while variants present in the standing population should be without effect. Three electrophysiological experiments will answer the following questions: Aim 1: Can missense variants produce active ion channels that are involved in neuropathology? Aim 2: Do missense variants alter the actions of D-serine and Ca2+ on constitutively active channels? Aim 3: Do missense variants alter the actions of glutamate on GluD1-GluK2 chimeric receptors?

概括 谷氨酸受体基因家族编码 AMPA、红藻氨酸和 NMDA 受体，介导 中枢神经系统的兴奋性突触传递。另外两个基因家族成员 GRID1 和 GRID2，编码神秘的 δ 受体 GluD1 和 GluD2 亚基，它们可以结合 D-丝氨酸，但不结合 似乎不会激活传统的信号系统。 Delta 有四种已知的功能效应 受体：(1) 当基因发生某些突变时，两种 δ 受体（GluD1 和 GluD2）都会被激活。 跨膜螺旋，将非门控受体转化为组成性开放的通道， 产生补强的内向电流。此外，其中谷氨酸结合结构域的嵌合受体 来自红藻氨酸或 AMPA 受体的替代 GluD1 和 GluD2 的类似 D-丝氨酸结合域可以 被谷氨酸激活，表明转换激动剂结合所需的高度专业化的机制 进入孔洞的通道在 delta GluD1 受体中是保守的。 (2) D-丝氨酸与GluD1受体的结合 含有使它们持续活跃的 TM3 突变可以关闭通道，从而提高了这种可能性 D-丝氨酸结合产生有意义的构象变化，在 WT 中具有未知的生理作用 受体。 (3) Ca2+ 与两个相邻 D-丝氨酸结合域之间的二聚体界面处的位点结合 增强突变受体的组成电流，表明 Ca2+ 可以调节 GluD1 构象 功能。 (4)远端胞外结构域作为突触前Cbln2和神经素的配体，可以 改变突触的形成。尽管 Cbln2 和神经毒素与 GluD1 的结合似乎至关重要，但它仍然存在 目前尚不清楚 GluD1 的通道门控、D-丝氨酸结合或 Ca2+ 调节是否在大脑中发挥重要作用。 群体遗传学的独特之处在于，它可以公正地识别蛋白质的关键功能。 方式。 GRID1 是体内耐受性最差的基因之一，因缺乏而落在前 2 个百分点。 变异，表明它起着重要作用。与这个想法一致的是，患有神经系统疾病的患者 已鉴定出 GRID1 中存在一般人群中不存在的错义变异。我们将 除了常见的耐受性良好的变异之外，还评估与疾病相关的变异的影响 健康人群与 GRID1 功能相关的三种模式——组成型激活、D-丝氨酸 结合，Ca2+ 结合。如果这些功能属性中的任何一个很重要，那么我们期望发现疾病- 扰乱它们的相关变体，而常住群体中存在的变体应该没有 影响。三个电生理学实验将回答以下问题： 目标 1：错义变体能否产生参与神经病理学的活性离子通道？ 目标 2：错义变体是否会改变 D-丝氨酸和 Ca2+ 在组成型活性通道上的作用？ 目标 3：错义变体是否会改变谷氨酸对 GluD1-GluK2 嵌合受体的作用？