Signaling Pathways Regulating Synaptic Vesicle Dynamics

神经元之间的交流主要是通过分泌化学神经递质来影响邻近细胞的电或生化活动。这些神经递质储存在被称为突触囊泡的小细胞器中，这些小细胞器位于突触前神经末梢。为了分泌神经递质，突触囊泡必须与神经末梢的表面膜融合，从而使神经递质扩散到附近的目标神经元。这种受到严格调控的融合过程是神经元间通讯的基本事件。最近的研究表明，囊泡融合是一种低概率事件，与突触囊泡与活跃区对接的数量有关，活跃区是发生融合的地方。具有融合能力的囊泡和大部分保留的囊泡之间存在动态平衡；这种平衡是以依赖于aCa2+的方式调节的。大脑中这些Ca2+依赖性变化的分子基础尚不完全清楚，部分原因是数十亿的显微神经末梢分布在整个大脑中，这使得在完整的制备中同步神经末梢的活动变得困难或不可能。turner博士提出的工作旨在研究使用突触体调节突触囊泡动力学的信号通路，突触体是相对均匀组成的孤立神经末梢的制备。特纳博士的实验室将使用突触体来测量与调节突触囊泡成熟有关的特定信号通路活动的生化变化，包括Ca2+调节的激酶和氨基gtp结合称为Ral。同时，这些信号通路的相关性将通过测量在一个更完整的准备中突触传递的强度来评估，从小脑获得的急性脑切片。在这种制备中发现的与浦肯野细胞突触平行的纤维是一种具有良好特征的兴奋性突触，它应该是在大脑所有部位发现的兴奋性突触的代表。同时测量神经递质释放和伴随的细胞质信号通路的变化将促进对Ca2+依赖性突触强度变化的机制的更详细的理解，这对大脑中神经元间信号传导很重要。这项工作的影响将广泛扩展到整个神经科学，因为突触传递在大脑信息处理中的基本重要性，包括感觉接收、运动控制、注意力和决策、学习和记忆。此外，这个项目将有助于启动一个年轻的研究者的独立职业生涯。

Neurons communicate with one and other primarily by secreting chemicalneurotransmitters that influence the electrical or biochemical activities ofneighboring cells. These neurotransmitters are stored in small organellescalled synaptic vesicles that are localized to presynaptic nerve endings. Inorder for neurotransmitter to be secreted, a synaptic vesicle must fuse with thesurface membrane at the nerve terminal, which allows neurotransmitter to diffuseto the nearby target neurons. This tightly regulated fusion process is thefundamental event in interneuronal communication. Recent work has revealed thatvesicle fusion is a low probability event related to the number of synapticvesicles docked with the active zone, the site at which fusion occurs. A dynamicequilibrium exists between vesicles that are fusion-competent and the majorityof vesicles that are held in reserve; this equilibrium is regulated in aCa2+-dependent manner. The molecular basis for these Ca2+-dependent changes inthe brain is incompletely understood, in part because billions of microscopicnerve terminals are distributed throughout the brain, making it difficult ofimpossible to synchronize the activity of the nerve terminals in an intactpreparation. Work proposed by Dr. turner is designed to study thesignaling pathways that regulate synaptic vesicle dynamics using synaptosomes, apreparation of isolated nerve terminals that is relatively uniform incomposition. Dr. Turner's laboratory will use synaptosomes to measure biochemical changes inthe activities of specific signaling pathways that have been implicated inregulating synaptic vesicle maturation, including Ca2+-regulated kinases and amonomeric GTP-binding known as Ral. In parallel, the relevanceof these signaling pathways will be evaluatued by measuring the strength of synaptic transmission in a more intact preparation, the acute brain slice obtained from cerebellum.The parallel fiber to Purkinje cell synapse found in this preparation is a well-characterized excitatory synapse that should be representative ofexcitatory synapses found in all parts of the brain. Simultaneous measurementsof neurotransmitter release and the attendant changes in cytoplasmic signalingpathways will advance a more detailed understanding of the mechanisms that underlie Ca2+-dependent changes in synaptic strength important to interneuronal signaling in the brain. The impact of this work will extend broadly throughout neuroscience because of the fundamental importance of synaptic transmission in information processing by the brain, for features including sensory reception, motor control, attention and decision, and learning and memory. In addition, this project will help launch the independent career of a young investigator.