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: 8306730
• 负责人: Hisashi Umemori
• 金额: $ 11.58万
• 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 2013-12-15
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8306730
• 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.

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功能至关重要。在最初的突触分化之后，突触通过神经活动而成熟和稳定，以建立适当的突触连接。在成熟过程中，突触前终扣增大，更多的突触囊泡聚集到突触前末端，活动区和突触后密度的数量增加，并且棘的形状响应于突触活动而改变。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囊泡的能力作为生物测定，我们已经从发育中的大脑中纯化了可以组织突触前末梢的分子。该纯化揭示了诱导突触囊泡聚集的两个活性峰。一个峰含有FGF 22，并且我们已经表明FGF促进小脑、神经肌肉和海马突触的分化1 -3。另一个峰，我们在这里集中，包含信号调节蛋白1（SIRP 1），跨膜免疫球蛋白超家族成员4的胞外结构域。SIRP 1在突触成熟时在海马中高度表达。它位于树突中并集中在突触处。有趣的是，SIRP 1的细胞外结构域被切割并响应于细胞活化而脱落。SIRP 1胞外区对培养的海马神经元的应用促进了突触小泡聚集。条件性SIRP 1基因敲除小鼠表现出突触前成熟缺陷。从这些初步的结果，我们提出了以下模型的活性依赖性成熟的海马突触：最初的突触形成后，轴突树突接触，神经递质的释放从突触前终端诱导分裂的突触后SIRP 1，和脱落的SIRP 1的胞外域反过来促进突触前终端的成熟。为了验证这一假设，我们提出：7目的1：确定SIRP 1的突触前效应是否需要胞外域脱落7目的2：研究神经活动对SIRP 1依赖的突触前成熟的作用7目的3：检查SIRP 1胞外区脱落对体内突触前成熟的重要性我们将使用分子和细胞生物学，生物化学，成像和电生理方法。通过这些研究，我们应该了解海马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，都与海马体中突触的异常改变有关。此外，SIRP 1受体CD 475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SIRP 1基因敲除小鼠来研究SIRP 1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。