NMDAR Mutations & Neurodevelopmental Disorder: from Mechanism to Targeted Therapy

描述（由申请人提供）：神经发育障碍与影响儿童行为、记忆或学习能力的脑功能障碍有关。这些残疾给个人、家庭和社会带来毁灭性的精神、情感和经济后果。残疾子集的分子基础涉及各种离子通道家族的致病突变，包括NMDA受体（NMDARs）。由两个甘氨酸结合GluN1亚基和两个谷氨酸结合GluN2亚基组装而成的阳离子选择性NMDAR通道介导了兴奋性突触电流中缓慢的Ca2+渗透成分，可以触发突触强度的变化，这是学习的细胞相关。NMDARs在正常的大脑发育中也起着重要作用。仅在过去三年中就报道了大量的突变（bbb140），导致人们认为这些突变存在于神经系统疾病患者的一个子集中，特别是早发性难治性癫痫。令人惊讶的是，在出现神经系统问题的儿科患者中发现的NMDAR突变发生率为5.7%，与Na+， K+， Ca2+通道和GABA受体相似或更高。NMDAR亚基突变已在患有多种神经发育问题的儿童中被发现，包括注意缺陷多动障碍（ADHD）、自闭症谱系障碍、发育迟缓、智力低下、精神分裂症、智力残疾和顽固性癫痫。不幸的是，几乎没有这些突变的功能分析存在，使得不可能评估突变在临床表型背景下的影响。我们提出了4条实验线，以解决NMDAR亚基突变引起的神经系统疾病的分子机制。我们将研究跨膜结构域（TM）、连接体和配体结合结构域（LBD）突变的功能影响，并测试fda批准的药物纠正突变诱导的功能获得的能力。所有实验都将使用含有0、1或2个突变NMDAR亚基的受体，从而能够评估杂合患者的功能。目的1。人类NMDAR在TM-连接区域的突变如何影响功能？我们将分析跨膜结构域或相关连接体中的26个突变。我们将共同努力获得明渠结构的晶体。目标2。人类NMDAR在配体结合域的突变如何影响其功能？我们将评估36个配体结合域突变的功能影响，并合作获得晶体学数据。目标3。人类NMDAR突变如何影响神经元运输和功能？我们将分析转染突变型NMDAR亚基的切片培养中NMDAR介导的突触电流的特性。目标4。NMDAR通道病变可以治疗吗？我们将评估fda批准的NMDAR拮抗剂在NMDAR功能获得突变时的效价（IC50），并评估NMDAR突变的神经毒性潜力。

DESCRIPTION (provided by applicant): Neurodevelopmental disorders are associated with disabilities in brain function that affect a child's behavior, memory or ability to learn. Such disabilities carry devastating mental, emotional, and economic consequences for the individuals, their families, as well as society. The molecular bases for a subset of disabilities involve disease-causing mutations in various ion channel families, including NMDA receptors (NMDARs). The cation-selective NMDAR channels formed from assembly of two glycine-binding GluN1 subunits and two glutamate-binding GluN2 subunits mediate a slow, Ca2+-permeable component of excitatory synaptic currents that can trigger changes in synaptic strength, a cellular correlate of learning. NMDARs also play an important role in normal brain development. A large number of mutations (>140) have been reported in just the last three years, leading to the view that these mutations are present in a subset of patients with neurological disorders, particularly early onset intractable seizures. Surprisingly, the incidence of NMDAR mutations found in pediatric patients presenting with neurological problems is 5.7%, similar to or higher than that for Na+, K+ , Ca2+ channels and GABA receptors. Mutations in NMDAR subunits have been identified in children with a broad range of neurodevelopmental problems, including attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, developmental delay, mental retardation, schizophrenia, intellectual disability, and intractable seizures. Unfortunately, virtually no functional analysis of these mutations exists, making it impossible to evaluate effects of mutations in the context of clinical phenotype. We proposed 4 lines of experimentation addressing the molecular mechanism underlying neurological diseases suggested to arise from mutations in NMDAR subunits. We will study the functional effects of mutations in the transmembrane domain (TM), linkers, and ligand binding domains (LBD) and test the ability of FDA-approved drugs to rectify the mutation-induced gain-of-function. All experiments will utilize receptors that contain 0, 1, or 2 mutant NMDAR subunits, enabling an assessment of function in heterozygous patients. Aim 1. How do human NMDAR mutations in the TM- linker regions impact function? We will analyze 26 mutations in the transmembrane domain or associated linkers. We will collaborate on efforts to obtain crystals of the open channel configuration. Aim 2. How do human NMDAR mutations in the ligand binding domains impact function? We will evaluate the functional effects of 36 mutations in the ligand binding domain, and collaborate to obtain crystallographic data. Aim 3. How do human NMDAR mutations influence neuronal trafficking and function? We will analyze the properties of NMDAR-mediated synaptic current in slice cultures transfected with mutant NMDAR subunits. Aim 4. Are NMDAR channelopathies treatable? We will evaluate the potency (IC50) of FDA-approved NMDAR antagonists at gain-of-function NMDAR mutations and evaluate the neurotoxic potential of NMDAR mutations.