Genetics of New Synaptic Components and Their Functions

描述（由申请人提供）：该提案侧重于突触形态学的两种类型的变化：突触后膜的扩张和突触前终扣的形成。解剖学上的特化是突触的一个标志。在突触后方面，解剖学上的特化包括树突棘和膜褶皱。在突触前侧，神经突的扩大形成圆形的突触前终扣或顺便肿胀几乎是突触的普遍特征。本提案的目的1测试了一个特定的假设，活动如何可以调节在果蝇神经肌肉接头和哺乳动物树突棘突触后的解剖学变化。特别是，它试图阐明拉尔的作用， 活动依赖性解剖可塑性的中介。我们已经发现了一种新的突触可塑性的途径，其中小GTdR α 1，通过激活外囊复合物，在将谷氨酸受体的Ca 2+内流转换为增强的膜向突触后区域的转运中起核心作用。因此，在果蝇神经肌肉接头（NMJ）的突触后专业化的膜面积扩大的活动依赖性的方式。这个提议询问了什么样的突触活动模式是募集外囊所必需的，以及Ral是如何被定位到突触后膜的。它继续研究Ral对于哺乳动物中枢神经系统中树枝状棘形成的重要性。目的2使用果蝇作为模型系统，揭示了允许突触终扣形成的机制。突触前终末从生长锥到突触终扣的成熟是突触发生中的一个关键的晚期步骤，但人们对此知之甚少。无论是细胞骨架元素的形状变化和信号分子触发它是已知的。在先前的果蝇突变体筛选中，我们发现2-3中的突变在初始突触形成后阻止突触发生，并阻止果蝇NMJ处突触终扣的形成。我们建议通过生物化学和遗传学方法的结合来更详细地研究扣状突起形成的过程，以揭示突触解剖学这一鲜为人知的方面的形成中的其他参与者。因此，在目标2A中，我们将使用生物化学方法来鉴定2-3的结合配偶体，并确定它们是否是终扣形成所需的。在目标2B中，我们将通过果蝇基因组在胚胎NMJ的突变筛选，发现更多的参与者。

DESCRIPTION (provided by applicant): This proposal focuses on two types of change in synapse morphology: expansion of postsynaptic membranes and formation of presynaptic boutons. Anatomical specializations are a hallmark of synapses. On the postsynaptic side, anatomical specializations include dendritic spines and membrane folds. On the presynaptic side, an enlargement of the neurite to form a rounded presynaptic bouton or en passant swelling is a nearly universal feature of synapses. Aim 1 of this proposal tests a specific hypothesis for how activity can regulate anatomical changes at the postsynapse in the fly neuromuscular junction and in mammalian dendritic spines. In particular, it seeks to elucidate the role of Ral as a mediator of activity-dependent anatomical plasticity. We have uncovered a novel pathway for synaptic plasticity in which the small GTPase Ral, by activating the exocyst complex, serves a central role in transducing Ca2+ influx from glutamate receptors into enhanced transport of membrane to the postsynaptic region. In consequence, the membrane area of the postsynaptic specialization at the fly neuromuscular junction (NMJ) expands in an activity-dependent manner. This proposal asks what patterns of synaptic activity are necessary to recruit the exocyst and how Ral comes to be localized to postsynaptic membranes. It goes on to investigate the significance of Ral for the formation of dendritic spines in the mammalian CNS. Aim 2 uses Drosophila as a model system in which to uncover the machinery that allows synaptic boutons to form. The maturation of presynaptic terminals from growth cones to synaptic boutons is a critical late step in synaptogenesis but poorly understood. Neither the cytoskeletal elements that underlie the shape change nor signaling molecules that trigger it are known. In a previous mutant screen in Drosophila we discovered that mutations in 2-3 arrest synaptogenesis after initial synapse formation and prevent the formation of synaptic boutons at the fly NMJ. We propose to pursue the process of bouton formation in greater detail by a combination of biochemical and genetic approaches to uncover additional players in the formation of this poorly understood aspect of synaptic anatomy. Therefore, in Aim 2A we will use biochemical methods to identify binding partners for 2-3 and determine if they are required for bouton formation. In Aim 2B we will uncover additional players in bouton formation through a mutant screen of the Drosophila genome at the embryonic NMJ.