Synaptic Plasticity and the Dynamic Interactions Between Calcium and Presynaptic

突触可塑性以及钙与突触前的动态相互作用

• 批准号: 7780554
• 负责人: SIMON T ALFORD
• 金额: $ 39.91万
• 依托单位: UNIVERSITY OF ILLINOIS AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-12-08 至 2014-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7780554
• 关键词: Acetylcholine; Action Potentials; Address; Aggressive behavior; Axon; Binding; Biological Models; Bite; Botulinum Toxins; Brain; Brain Diseases; Buffers; Calcium; Chemicals; Communication; Complex; Data; Dependency; Depressed mood; Disease; Dopamine; Dyes; Exocytosis; Exocytosis Inhibition; Fluorescence; Functional disorder; G-Protein-Coupled Receptors; GTP-Binding Proteins; Glutamates; In Situ; In Vitro; Intervention; Ion Channel; Label; Lampreys; Lead; Liposomes; Location; Measurement; Measures; Mediating; Membrane; Mental Depression; Methods; Mind; Modeling; Nervous system structure; Neuraxis; Neuromodulator; Neuronal Plasticity; Neurons; Neurosecretion; Neurotransmitters; Outcome; Parkinson Disease; Pathology; Pathway interactions; Physiologic pulse; Physiological; Preparation; Presynaptic Terminals; Probability; Process; Protein Subunits; Proteins; Role; Running; SNAP receptor; Schizophrenia; Second Messenger Systems; Serotonin; Serotonin Receptor 5-HT1B; Signal Transduction; Site; Solutions; Sum; Synapses; Synaptic Transmission; Synaptic Vesicles; Synaptic plasticity; System; Vesicle; aqueous; base; flash photolysis; fluorophore; gamma-Aminobutyric Acid; inhibitor/antagonist; insight; millisecond; neuropathology; neurotransmission; neurotransmitter release; postsynaptic; presynaptic; prevent; protein complex; protein function; protein protein interaction; public health relevance; receptor; receptor function; reconstitution; relating to nervous system; research study; second messenger; synaptic function; synaptotagmin

DESCRIPTION (provided by applicant): Understanding the function of synapses is key to understanding the nervous system, and yet, while synaptic transmission is ubiquitously controlled by presynaptic G protein coupled receptors (GPCRs), the means by which these receptors modify release is contentious. Central nervous diseases, in which GPCR function is treated by pharmacological intervention, cover conditions ranging from aggression, depression and schizophrenia. Inhibitory presynaptic GPCRs alter synaptic function by many mechanisms. These may utilize the G?? G protein subunit to modify presynaptic ion channels and then synaptic secretion, or to modify the very machinery of vesicle fusion, the SNARE complex. Alternatively, these signaling systems may act indirectly through, other second messengers. We have focused on direct mechanisms by which G?? inhibits transmitter release and have demonstrated that G?? can inhibit neurosecretion by an interaction with the fusion machinery - the SNARE complex. This interaction occurs late in the activation of the synapse, after priming, in vesicles whose SNARE complex is formed. We hypothesize that G?? binds to the ternary SNARE complex to compete with Ca2+-dependent synaptotagmin binding. In this way G?? might be thought of as means to interfere with the final switch leading to neurosecretion. We propose that this action of G?? also confers a Ca2+ dependency on G?? -mediated presynaptic inhibition because high presynaptic Ca2+ concentrations allow synaptotagmin to compete more effectively with the machinery of vesicle fusion. The final outcome of this G?? competition with synaptotagmin allows a fine-tuned control of secretion. G?? causes kiss-and-run fusion of the exocytosing vesicle. This reduces the peak synaptic concentration of neurotransmitter, adding a complex twist to the method by which GPCRs alter synaptic function. We propose to investigate competition between the switch that activates synapses - Ca2+-synaptotagmin - and an inhibitor of this process - G??. We hypothesize that G?? and synaptotagmin share an interaction site on the SNARE complex. To demonstrate this, we will investigate G?? competition with synaptotagmin at the SNARE complex and compare effects of Ca2+ on this competition to similar manipulations in a simple reconstituted model for fusion and at the lamprey giant axon in situ. We will then modify in situ SNARE complex proteins using intracellularly applied Botulinum toxins to compare similar truncations in vitro. We will also use fluorescence measurements of exogenously applied G?? model systems of the protein components of vesicle fusion to determine whether Ca2+ evokes similar effects on binding and on neurotransmitter release in situ. These experimental paradigms will then be reproduced with dynamically fluctuating Ca2+ concentrations to mimic a real world activity of central synapses. These experiments will afford insight into the dynamic modulation possible with a simple protein-protein interaction and explain some of the complexities of presynaptic GPCR-mediated presynaptic modulation and their roles in neuropathologies. PUBLIC HEALTH RELEVANCE: In the central nervous system, G protein coupled receptors are ubiquitous and pathologies related to dysfunction of this widely distributed group of receptors lead to devastating illnesses of the mind, including Parkinson's disease, Schizoprenia, depression and compulsive disorders. However, at the basic unit of nervous system communication - the synapse - we understand little of the way G proteins function. We wish to understand how these mechanisms modify chemical communication using one such receptor, the 5-HT1B receptor, as a model in a simple vertebrate synapse. We will determine how this receptor acts and how it modulates chemical communication throughout the brain.

描述（由申请人提供）：了解突触的功能是了解神经系统的关键，然而，虽然突触传递普遍受到突触前 G 蛋白偶联受体 (GPCR) 的控制，但这些受体调节释放的方式仍存在争议。通过药物干预治疗 GPCR 功能的中枢神经疾病包括攻击性、抑郁症和精神分裂症等疾病。抑制性突触前 GPCR 通过多种机制改变突触功能。这些可以利用G?? G 蛋白亚基可以修饰突触前离子通道，然后修饰突触分泌，或者修饰囊泡融合的机制，即 SNARE 复合体。或者，这些信号系统可以通过其他第二信使间接起作用。我们重点关注 G?? 的直接机制。抑制递质释放并已证明 G??可以通过与融合机制 - SNARE 复合体的相互作用来抑制神经分泌。这种相互作用发生在突触激活后期，即启动后，在形成 SNARE 复合体的囊泡中。我们假设G??与三元 SNARE 复合物结合，与 Ca2+ 依赖性突触结合蛋白结合竞争。这样G??可能被认为是干扰导致神经分泌的最终转换的手段。我们建议G??的这一行动还赋予了 G 的 Ca2+ 依赖性？ - 介导的突触前抑制，因为高突触前 Ca2+ 浓度使突触结合蛋白能够更有效地与囊泡融合机制竞争。这G的最终结局？？与突触结合蛋白的竞争可以对分泌进行微调控制。克??导致胞吐囊泡的“吻跑”融合。这降低了神经递质的峰值突触浓度，为 GPCR 改变突触功能的方法增加了复杂的扭曲。我们建议研究激活突触的开关 - Ca2+-突触结合蛋白 - 和该过程的抑制剂 - G?? 之间的竞争。我们假设G??和突触结合蛋白在 SNARE 复合体上共享一个相互作用位点。为了证明这一点，我们将研究 G??与 SNARE 复合体中的突触结合蛋白竞争，并将 Ca2+ 对这种竞争的影响与简单重构融合模型中和原位七鳃鳗巨轴突中的类似操作进行比较。然后，我们将使用细胞内应用的肉毒杆菌毒素原位修饰 SNARE 复合蛋白，以在体外比较类似的截短。我们还将使用外源施加的 G?? 的荧光测量囊泡融合的蛋白质成分的模型系统，以确定 Ca2+ 是否对结合和原位神经递质释放产生类似的影响。然后，这些实验范例将通过动态波动的 Ca2+ 浓度来重现，以模拟真实世界的中央突触活动。这些实验将深入了解简单的蛋白质-蛋白质相互作用可能发生的动态调节，并解释突触前 GPCR 介导的突触前调节的一些复杂性及其在神经病理学中的作用。 公共健康相关性：在中枢神经系统中，G 蛋白偶联受体无处不在，与这组广泛分布的受体功能障碍相关的病理会导致毁灭性的精神疾病，包括帕金森病、精神分裂症、抑郁症和强迫症。然而，对于神经系统通讯的基本单位——突触——我们对 G 蛋白的功能知之甚少。我们希望了解这些机制如何使用这样一种受体（5-HT1B 受体）作为简单脊椎动物突触的模型来改变化学通讯。我们将确定这种受体如何发挥作用以及它如何调节整个大脑的化学通讯。