Synapse Maturation by Activity-Dependent Ectodomain Shedding of SIRP

SIRP 活性依赖性胞外域脱落导致突触成熟

• 批准号: 8026981
• 负责人: Hisashi Umemori
• 金额: $ 19.27万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8026981
• 关键词: Alzheimer' s Disease; Autistic Disorder; Axon; Biochemical; Biological; Biological Assay; Brain; COS Cells; Cell Adhesion Molecules; Cleaved cell; Coculture Techniques; Defect; Dendrites; Development; Disease; Etiology; Extracellular Domain; Fragile X Syndrome; Functional disorder; Future; Hippocampus (Brain); Image; Immunoglobulins; Knockout Mice; Learning; Length; Mediating; Memory; Mental Retardation; Modeling; Molecular; Neurons; PTPNS1 gene; Play; Presynaptic Terminals; Resistance; Role; SHPS-1 protein; Schizophrenia; Shapes; Signal Transduction; Site; Structure; Synapses; Synaptic Vesicles; System; Testing; Time; Vertebral column; base; density; design; in vivo; insight; long term memory; mutant; nervous system disorder; neural circuit; neuromuscular; neurotransmitter release; novel; overexpression; postsynaptic; presynaptic; prevent; receptor; relating to nervous system; response; synaptic function; synaptogenesis

DESCRIPTION (provided by applicant): Formation of functional synaptic connections is critical for proper functioning of the brain. After initial synaptic differentiation, synapses are maturated and stabilized by neural activity to establish appropriate synaptic connections. During maturation presynaptic boutons enlarge, more synaptic vesicles accumulate to the presynaptic terminal, the number of active zones and postsynaptic densities increases, and the shape of spines changes in response to synaptic activity. However, the molecular mechanisms underlying activity- dependent synapse maturation remain to be elucidated. Using the ability to cluster synaptic vesicles in cultured neurons as a bioassay, we have purified molecules that can organize presynaptic terminals from developing brains. This purification revealed two peaks of activity that induced synaptic vesicle clustering. One peak contains FGF22, and we have shown that FGFs promote differentiation of cerebellar, neuromuscular and hippocampal synapses1-3. The other peak, on which we focus here, contains the extracellular domain of signal regulatory protein 1 (SIRP1), a transmembrane immunoglobulin superfamily member4. SIRP1 is highly expressed in the hippocampus around the time of synapse maturation. It is localized in dendrites and concentrated at synapses. Interestingly, the extracellular domain of SIRP1 is cleaved and shed in response to cellular activation. The application of the extracellular domain of SIRP1 to cultured hippocampal neurons promotes synaptic vesicle clustering. Conditional SIRP1 knockout mice show defects in presynaptic maturation. From these preliminary results, we propose the following model for activity-dependent maturation of hippocampal synapses: After initial synapse formation by axon-dendrite contacts, neurotransmitter release from the presynaptic terminal induces the cleavage of postsynaptic SIRP1, and the shed ectodomain of SIRP1 in turn promotes the maturation of the presynaptic terminal. To test this hypothesis, we propose to: 7 Aim 1: Determine whether ectodomain shedding is required for the presynaptic effect of SIRP1 7 Aim 2: Investigate the role of neural activity for SIRP1-dependent presynaptic maturation 7 Aim 3: Examine the importance of ectodomain shedding of SIRP1 for presynaptic maturation in vivo We will use molecular and cellular biological, biochemical, imaging and electrophysiological approaches. Through these studies we should understand the molecular mechanisms underlying functional synapse establishment in the hippocampus by neural activity. Many forms of neurological disorders including autism, schizophrenia, and Alzheimer's disease are associated with abnormal alterations of synapses in the hippocampus. Furthermore, a SIRP1 receptor, CD475 is implicated in learning, memory, Alzheimer's disease and schizophrenia6-9. Thus, our studies will also help design strategies to prevent and treat such neurological disorders. In future studies, we will use conditional SIRP1 knockout mice to investigate the in vivo role of SIRP1 and its ectodomain shedding in learning, memory formation and neurological disorders. PUBLIC HEALTH RELEVANCE: To establish appropriate synaptic connections in the brain, synapses must be maturated by neural activity during development. However, the molecular mechanisms underlying activity-dependent synapse maturation are not known. Here, we will determine the role of activity-dependent cleavage of SIRP1, a synaptic cell adhesion molecule, in synapse maturation in the hippocampus, the structure known to be critical for long-term memory formation. Because defects in SIRP1 signaling are implicated in Alzheimer's disease and schizophrenia, our studies should yield novel insights into the pathophysiology and treatment of such devastating neurological disorders.

描述（由申请人提供）：功能突触连接的形成对于大脑正确功能至关重要。初始突触分化后，突触被神经活动成熟并稳定，以建立适当的突触连接。在成熟前胸子扩大期间，更多的突触囊泡积聚在突触前末端，活性区域和突触后密度的数量增加，刺的形状在反应突触活动时变化。然而，依赖性突触成熟的分子机制仍有待阐明。利用能够将突触囊泡聚集在培养的神经元中的生物测定的能力，我们具有纯化的分子，可以从发育中的大脑中组织突触前末端。这种纯化揭示了两个活性峰，这些峰会诱导突触囊泡聚类。一个峰包含FGF22，我们已经表明FGF促进了小脑，神经肌肉和海马突触的分化1-3。我们在此关注的另一个峰包含信号调节蛋白1（SIRP1）的细胞外结构域，跨膜免疫球蛋白超家族成员4。 SIRP1在突触成熟时在海马中高度表达。它位于树突中，集中在突触中。有趣的是，SIRP1的细胞外域被裂解并响应细胞激活而脱落。 SIRP1的细胞外域在培养的海马神经元中的应用促进了突触囊泡聚类。有条件的SIRP1敲除小鼠在突触前成熟中显示缺陷。 From these preliminary results, we propose the following model for activity-dependent maturation of hippocampal synapses: After initial synapse formation by axon-dendrite contacts, neurotransmitter release from the presynaptic terminal induces the cleavage of postsynaptic SIRP1, and the shed ectodomain of SIRP1 in turn promotes the maturation of the presynaptic terminal. To test this hypothesis, we propose to: 7 Aim 1: Determine whether ectodomain shedding is required for the presynaptic effect of SIRP1 7 Aim 2: Investigate the role of neural activity for SIRP1-dependent presynaptic maturation 7 Aim 3: Examine the importance of ectodomain shedding of SIRP1 for presynaptic maturation in vivo We will use molecular and cellular biological, biochemical,成像和电生理方法。通过这些研究，我们应该了解通过神经活性在海马中实现功能突触建立的分子机制。许多形式的神经系统疾病，包括自闭症，精神分裂症和阿尔茨海默氏病，与海马突触异常改变有关。此外，SIRP1受体CD475与学习，记忆，阿尔茨海默氏病和精神分裂症6-9有关。因此，我们的研究还将帮助设计策略来预防和治疗此类神经系统疾病。在未来的研究中，我们将使用条件SIRP1敲除小鼠研究SIRP1及其外部域在学习，记忆形成和神经系统疾病中的体内作用。 公共卫生相关性：为了在大脑中建立适当的突触连接，在发育过程中的神经活动中必须成熟突触。但是，尚不清楚活性依赖性突触成熟的分子机制。在这里，我们将确定SIRP1的活性依赖性裂解（一种突触细胞粘附分子）在海马中突触成熟中的作用，这种结构已知对于长期记忆形成至关重要。由于SIRP1信号的缺陷与阿尔茨海默氏病和精神分裂症有关，因此我们的研究应产生对这种毁灭性神经系统疾病的病理生理学和治疗的新见解。