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。这种残疾对个人、其家庭以及社会带来毁灭性的精神、情感和经济后果。残疾的一个子集的分子基础涉及各种离子通道家族中的致病突变，包括NMDA受体（NMDAR）。由两个甘氨酸结合GluN 1亚基和两个谷氨酸结合GluN 2亚基组装而成的阳离子选择性NMDAR通道介导兴奋性突触电流的缓慢的、Ca 2+可渗透的组分，其可以触发突触强度的变化，这是学习的细胞相关物。NMDAR在正常的大脑发育中也起着重要作用。在过去的三年中，已经报道了大量的突变（>140），导致这些突变存在于神经系统疾病患者的子集中，特别是早期发作的难治性癫痫发作。令人惊讶的是，在存在神经问题的儿科患者中发现的NMDAR突变的发生率为5.7%，与Na+、K+、Ca 2+通道和GABA受体的发生率相似或更高。NMDAR亚基的突变已在具有广泛神经发育问题的儿童中被鉴定，包括注意缺陷多动障碍（ADHD）、自闭症谱系障碍、发育迟缓、精神发育迟滞、精神分裂症、智力残疾和顽固性癫痫发作。不幸的是，几乎没有这些突变的功能分析存在，使得它不可能在临床表型的背景下评估突变的影响。 我们提出了4条实验路线，以解决神经系统疾病的分子机制，这些疾病被认为是由NMDAR亚基突变引起的。我们将研究跨膜结构域（TM），接头和配体结合结构域（LBD）突变的功能效应，并测试FDA批准的药物纠正突变诱导的功能获得的能力。所有实验将利用含有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。 目标1. TM-接头区中的人NMDAR突变如何影响功能？我们将分析跨膜结构域或相关接头中的26个突变。我们将合作努力获得开放通道配置的晶体。 目标2.配体结合域中的人NMDAR突变如何影响功能？我们将评估配体结合域中36个突变的功能效应，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？我们将在转染突变NMDAR亚基的切片培养物中分析NMDAR介导的突触电流的性质。 目标4。NMDAR通道病可以治疗吗？我们将评估FDA批准的NMDAR拮抗剂在功能获得性NMDAR突变下的效力（IC 50），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.