Autism-linked endosomal mechanisms in neuronal arborization and connectivity

神经元树枝化和连接中与自闭症相关的内体机制

• 批准号: 8887441
• 负责人: Eric M Morrow
• 金额: $ 40.63万
• 依托单位: BROWN UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8887441
• 关键词: Amantadine; Area; Attenuated; Autistic Disorder; Autopsy; Biology; Brain; Brain-Derived Neurotrophic Factor; Cell physiology; Cellular biology; Chloroquine; Clinical Research; Cytoplasmic Tail; Data; Defect; Degradation Pathway; Development; Disease; Down-Regulation; Early Endosome; Endosome Proton; Endosomes; FDA approved; Family; Functional disorder; Gene Expression; Genes; Hippocampus (Brain); Human; In Vitro; Integral Membrane Protein; Intervention; Investigation; Knockout Mice; Lead; Link; Lysosomes; Mediating; Medicine; Mental disorders; Mission; Molecular Target; Mus; Mutation; Neuronal Differentiation; Neurons; Neurotrophic Tyrosine Kinase Receptor Type 2; Outcome; Pathway interactions; Patients; Phenotype; Play; Process; Proteins; Protons; Public Health; Publications; Recycling; Regulation; Relative (related person); Reporting; Research; Research Proposals; Resources; Role; Signal Transduction; Societies; Strategic Planning; Synapses; Testing; Therapeutic Agents; Translations; United States National Institutes of Health; base; clinical phenotype; cost; endosome lumen; improved; in vivo; induced pluripotent stem cell; innovation; late endosome; mutant; neuronal circuitry; neuropsychiatry; novel; protein transport; public health relevance; trafficking; translational approach; translational neuroscience; treatment strategy

 DESCRIPTION (provided by applicant): No effective therapeutic agents currently exist to improve outcomes in severe autism. We recently identified a new cellular mechanism in autism involving endosomal Na+/H+ exchanger 6 (NHE6). Studies of NHE6 offer a valuable opportunity for rapid development of innovative treatment strategies in severe autism and related dis- orders. Human mutations in endosomal NHE6 constitute a newly recognized, monogenic, autism-related disorder. Also, down-regulation of NHE6 gene expression is evident in postmortem brains in approximately 30% of patients with idiopathic autism. NHE6 is an integral membrane protein that regulates proton efflux out of endosomes. We have reported that loss of NHE6 in neurons leads to over-acidification of the endosome lumen, and diminished neuronal arborization and synapse development. We also have exciting, new data demonstrating that intra-endosomal pH in the mutant is normalized in vitro by FDA-approved medicines known to alka- linize endosomes. The objective for this research proposal is to elucidate the mechanisms by which NHE6 mu- tations lead to defects in circuit development, and to test the ability of alkalinizing agents to normalize these mutant phenotypes in mouse in vitro and in vivo. Our data support the following central hypothesis: Loss of NHE6 function leads to over-acidification of early endosomes, which enhances degradation of cargo. We also hypothesize that over-acidification of early endosomes drives trafficking to the degradative pathway (i.e., to late endosomes and lysosomes), and decreases endosome recycling and endosome signaling. Our data indicate that TrkB is cargo in NHE6-associated endosomes. We find attenuated TrkB signaling in NHE6 mutant neu- rons. The BDNF/TrkB pathway is well-known to govern circuit development via endosomal signaling, and has broad significance in neuropsychiatry. Our Aims include: 1) Determine the functional domains of NHE6 protein through study of patient mutations; 2) Determine the role of NHE6 and intra-endosomal pH regulation in TrkB trafficking and endosomal signaling; and 3) Determine the reversibility of defects in neuronal arborization and synapse development in NHE6 mutant neurons using alkalinizing medicines. These studies on the role of intra-endosomal proton concentration are innovative because they represent: 1) a new level of cellular analysis in endosome trafficking and neuronal differentiation; and 2) a novel, druggable cellular mechanism in autism and related disorders. This research is significant because it will lead to 1) elucidation of fundamental and disease- relevant mechanisms in endosome biology and circuit development; and 2) development of specific avenues for mechanism-based treatments for severe autism. This project is also a part of an integrated translational ap- proach in our research group that is coordinated with ongoing studies in patient-derived induced pluripotent stem cells (iPSCs) and with clinical studies in patients with NHE6 mutations. Finally, this application is strongly in line with the NIH Interagency Autism Coordinating Committee (IACC) Strategic Plan that calls for the identification of molecular targets amenable to interventions.

 描述（由申请人提供）：目前没有有效的治疗药物可以改善严重自闭症的结局。我们最近发现了一个新的自闭症细胞机制，涉及内体Na+/H+交换器6（NHE 6）。对NHE 6的研究为快速开发严重自闭症和相关疾病的创新治疗策略提供了宝贵的机会。人类内体NHE 6突变构成了一种新认识的单基因自闭症相关疾病。此外，在大约30%的特发性自闭症患者的死后大脑中，NHE 6基因表达的下调是明显的。NHE 6是一种整合的膜蛋白，调节质子流出核内体。我们已经报道了神经元中NHE 6的缺失导致内体腔的过度酸化，并减少神经元分支和突触发育。我们还获得了令人兴奋的新数据，证明突变体中的内体内pH通过FDA批准的已知使内体碱化的药物在体外正常化。本研究计划的目的是阐明NHE 6突变导致回路发育缺陷的机制，并测试碱化剂在体外和体内小鼠中使这些突变表型正常化的能力。我们的数据支持以下中心假设：NHE 6功能的丧失导致早期内体的过度酸化，这增强了货物的降解。我们还假设早期内体的过度酸化驱动运输到降解途径（即，到晚期内体和溶酶体），并减少内体再循环和内体信号传导。我们的数据表明TrkB是NHE 6相关内体中的货物。我们在NHE 6突变神经元中发现TrkB信号减弱。众所周知，BDNF/TrkB通路通过内体信号传导来控制回路发育，并且在神经精神病学中具有广泛的意义。我们的目标包括：1）通过研究患者突变确定NHE 6蛋白的功能结构域; 2）确定NHE 6和内体pH调节在TrkB运输和内体信号传导中的作用;和3）使用碱化药物确定NHE 6突变神经元中神经元树枝化和突触发育缺陷的可逆性。这些关于内体质子浓度作用的研究是创新性的，因为它们代表了：1）内体运输和神经元分化中的新水平的细胞分析;和2）自闭症和相关疾病中的新的、可药物化的细胞机制。这项研究意义重大，因为它将导致1）阐明内体生物学和电路发展中的基本和疾病相关机制; 2）开发基于机制的严重自闭症治疗的具体途径。该项目也是我们研究小组综合翻译方法的一部分，该方法与正在进行的患者源性诱导多能干细胞（iPSC）研究和NHE 6突变患者的临床研究相协调。最后，该应用程序与NIH机构间自闭症协调委员会（IACC）战略计划非常一致，该计划要求确定适合干预的分子靶点。