Synaptic Plasticity and the Dynamic Interactions Between Calcium and Presynaptic

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突触前G蛋白偶联受体（GPCR）控制，但这些受体调节释放的方式存在争议。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。抑制性突触前GPCR通过许多机制改变突触功能。可以利用G？G蛋白亚基修饰突触前离子通道，然后突触分泌，或修饰囊泡融合的机制，SNARE复合物。或者，这些信号传导系统可以通过其他第二信使间接起作用。我们已经专注于直接的机制，其中G？？抑制递质释放，并已证明，G？？可以通过与融合机制-SNARE复合物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的后期，在引发后，在形成SNARE复合物的囊泡中。我们假设G？结合到三元SNARE复合物上，与Ca 2+依赖性突触结合蛋白竞争结合。在这种情况下，G？可能被认为是干扰神经分泌最终开关的手段。我们建议，这一行动的G？？也赋予了Ca 2+依赖G？？- 介导的突触前抑制，因为高突触前Ca 2+浓度允许突触结合蛋白更有效地与囊泡融合的机制竞争。最后的结果是G？与突触结合蛋白的竞争允许对分泌进行微调控制。G？？导致胞吐囊泡的“吻了就跑”融合这降低了神经递质的突触峰值浓度，为GPCR改变突触功能的方法增加了复杂的扭曲。我们建议调查之间的竞争开关，激活突触-钙-synaptotagmin -和抑制剂，这一进程- G？？。我们假设G？和突触结合蛋白在SNARE复合物上共享一个相互作用位点。为了证明这一点，我们将调查G？竞争与synaptotagmin在SNARE复合物，并比较这种竞争的影响Ca 2+在一个简单的重组模型中的融合和在七鳃鳗巨大的轴突原位类似的操作。然后，我们将修改在原位陷阱复杂的蛋白质细胞内应用肉毒杆菌毒素比较类似的截断在体外。我们还将使用荧光测量外源应用G？？模型系统的蛋白质成分的囊泡融合，以确定是否Ca 2+引起类似的影响，结合和神经递质释放原位。这些实验范例，然后将再现与动态波动的Ca 2+浓度，以模仿中枢突触的真实的世界活动。这些实验将提供一个简单的蛋白质-蛋白质相互作用的动态调制可能的洞察和解释一些突触前GPCR介导的突触前调制的复杂性和它们在神经病理学中的作用。 公共卫生相关性：在中枢神经系统中，G蛋白偶联受体是普遍存在的，并且与这种广泛分布的受体组的功能障碍相关的病理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，在神经系统通信的基本单位-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修改化学通讯使用这样的受体，5-HT 1B受体，作为一个简单的脊椎动物突触的模型。我们将确定这种受体如何作用，以及它如何调节整个大脑的化学通讯。

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.