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?

总结 谷氨酸受体基因家族编码AMPA、红藻氨酸和NMDA受体，其介导 中枢神经系统中的兴奋性突触传递。另外两个基因家族成员，GRID 1 和GRID 2，编码神秘的δ受体GluD 1和GluD 2亚基，其可以结合D-丝氨酸，但不 似乎不会激活传统的信号系统。已知delta有四种功能效应 受体：（1）当特定的突变发生时，两种δ受体（GluD 1和GluD 2）都被激活。 跨膜螺旋，其将非门控受体转化为组成性开放的通道， 产生一种紧张性内向电流此外，其中谷氨酸结合结构域 来自红藻氨酸或AMPA受体的取代GluD 1和GluD 2的类似D-丝氨酸结合结构域， 被谷氨酸激活，这表明高度专业化的机器需要转换激动剂结合， 在δ GluD 1受体中是保守的。(2)D-丝氨酸与GluD 1受体的结合 携带一个TM 3突变，使它们组成性活跃，可以关闭通道，提高这种可能性， 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)Ca 2+结合到两个相邻D-丝氨酸结合结构域之间的二聚体界面处的位点 增强突变型受体的组成性电流，表明Ca 2+可以调节GluD 1构象， 功能(4)远端细胞外结构域作为突触前Cbln 2和neurexin的配体， 改变突触的形成尽管Cbln 2和neurexin与GluD 1的结合似乎是关键的，但它仍然存在。 尚不清楚通道门控、D-丝氨酸结合或GluD 1的Ca 2+调节是否在脑中发挥重要作用。 群体遗传学的一个独特的力量是，它可以在一个无偏见的情况下识别蛋白质的关键功能。 方式GRID 1是人体内耐受性最差的基因之一，在缺乏免疫原性的基因中排在前2%。 变化，这表明它起着重要的作用。与这一观点相一致的是，患有神经系统疾病的患者 已被鉴定为GRID 1中的错义变体，而这些错义变体在一般人群中不存在。我们将 评估疾病相关变异的影响，以及在临床中常见的耐受良好的变异。 健康人群对与GRID 1功能组成性激活、D-丝氨酸 结合，Ca 2+结合。如果这些功能属性中的任何一个是重要的，那么我们期望找到疾病- 相关的变异，扰乱他们，而变异存在于常设人口应该没有 效果三个电生理实验将回答以下问题： 目的1：错义变异体能否产生参与神经病理学的活性离子通道？ 目的2：错义变体是否改变D-丝氨酸和Ca 2+对组成性激活通道的作用？ 目的3：错义变体是否改变谷氨酸对GluD 1-GluK 2嵌合受体的作用？