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

基本信息

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
项目类别：
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&apos 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

项目摘要

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）：功能性突触连接的形成对于大脑的正常运作至关重要。在最初的突触分化之后，突触通过神经活动成熟和稳定，以建立适当的突触连接。在成熟过程中，突触前束增大，更多的突触小泡积聚到突触前末端，活动区的数量和突触后密度增加，并且棘的形状响应突触活动而变化。然而，活动依赖性突触成熟的分子机制仍有待阐明。利用在培养的神经元中聚集突触小泡的能力作为生物测定，我们纯化了可以组织发育中大脑的突触前末梢的分子。这种纯化揭示了诱导突触小泡聚集的两个活性峰。一个峰含有 FGF22，我们已经证明 FGF 促进小脑、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)（一种跨膜免疫球蛋白超家族成员）的胞外结构域。 SIRP1 在突触成熟前后在海马中高度表达。它位于树突中并集中在突触处。有趣的是，SIRP1 的胞外结构域响应细胞激活而被切割和脱落。将 SIRP1 的胞外结构域应用于培养的海马神经元可促进突触小泡聚集。条件性 SIRP1 基因敲除小鼠显示突触前成熟缺陷。根据这些初步结果，我们提出了以下海马突触活动依赖性成熟模型：在轴突-树突接触形成初始突触后，突触前末梢释放的神经递质依次诱导突触后 SIRP1 的裂解，以及 SIRP1 脱落的胞外域。促进突触前末梢的成熟。为了检验这一假设，我们建议： 7 目标 1：确定 SIRP1 的突触前效应是否需要胞外域脱落 7 目标 2：研究神经活动对 SIRP1 依赖性突触前成熟的作用 7 目标 3：检查胞外域的重要性体内突触前成熟过程中 SIRP1 的脱落我们将使用分子和细胞生物学、生化、成像和电生理学方法。通过这些研究，我们应该了解海马体通过神经活动建立功能性突触的分子机制。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病，都与海马突触的异常改变有关。此外，CD475 是 SIRP1 受体，与学习、记忆、阿尔茨海默病和精神分裂症有关6-9。因此，我们的研究也将有助于设计预防和治疗此类神经系统疾病的策略。在未来的研究中，我们将使用条件性SIRP1基因敲除小鼠来研究SIRP1及其胞外域脱落在学习、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，突触必须在发育过程中通过神经活动而成熟。然而，活动依赖性突触成熟的分子机制尚不清楚。在这里，我们将确定 SIRP1（一种突触细胞粘附分子）的活性依赖性裂解在海马突触成熟中的作用，已知该结构对长期记忆形成至关重要。由于 SIRP1 信号传导缺陷与阿尔茨海默病和精神分裂症有关，因此我们的研究应该对此类破坏性神经系统疾病的病理生理学和治疗产生新的见解。