A Novel System to Study Postsynaptic Molecules that Affect Presynaptic Function

描述（由申请人提供）：神经递质释放的活动依赖性调节，称为短期可塑性，涉及几种形式的行为和学习与记忆。虽然它是由突触前机制介导的，但短期可塑性已被证明在许多突触中是靶细胞特异性的。因此，来自相同细胞类型的轴突与不同类型的靶神经元形成的突触可以表现出明显不同的短期可塑性。这意味着存在从突触后神经元到突触前细胞的逆行信号，其根据突触后靶神经元的身份改变突触前末梢的结构和/或功能。虽然30多年来人们已经知道突触前功能是靶细胞特异性的，但这种逆行信使的身份仍然未知。这个项目的长期目标是确定负责靶细胞特异性短期可塑性的突触后分子。突触细胞粘附分子neuroligin 1和SynCAM最近已被证明在共培养的非神经元细胞中表达时诱导神经元的突触前分化。这表明，神经连接素1和SynCAM足以触发突触前分化，即使在突触后末端的其他正常成分的情况下。虽然神经连接蛋白1和SynCAM均已显示足以诱导在基本水平上起作用的神经元（在此称为半突触）中突触前末梢的形成，但尚不知道它们是否足以使半突触的突触前末梢具有神经元-神经元突触所具有的相同复杂的突触前性质。特别是，以前没有显示它们是否能够诱发神经递质释放，如果是这样，它们是否有类似的释放概率和机制的短期可塑性神经元-神经元突触。在这个提议中，我们将开发半突触制备和测量诱发的神经递质释放和短期可塑性，以检验触发突触形成的细胞粘附分子也参与调节突触前末梢功能特性的逆行信号传导的假设，但不足以诱导具有神经元-神经元突触的所有相同性质的突触前末梢的形成。该系统将提供一个简单但功能强大的检测，为未来的实验研究特定的细胞粘附分子，细胞外基质蛋白，神经营养因子，分泌因子和突触后密度成分对突触前末梢的形成和功能的影响。这些实验解决了突触前功能、突触特化和发育的基本问题，这些问题对我们理解大脑回路至关重要，并将对学习和记忆以及导致智力迟钝的神经退行性疾病和发育障碍产生影响。这些实验解决了突触前功能、突触特化和发育的基本问题，这些问题对我们理解大脑回路至关重要，并将对学习和记忆以及导致智力迟钝的神经退行性疾病和发育障碍产生影响。

DESCRIPTION (provided by applicant): Activity dependent modulation of neurotransmitter release, called short-term plasticity, has been implicated in several forms of behavior and learning and memory. Although it is mediated by presynaptic mechanisms, short-term plasticity has been shown at many synapses to be target-cell specific. Thus synapses made by axons from the same cell type onto target neurons of different types can exhibit markedly different properties of short-term plasticity. This implies the existence of a retrograde signal from the postsynaptic neuron to the presynaptic cell which alters the structure and/or function of the presynaptic terminal depending on the identity of the postsynaptic target neuron. While it has been known for over 30 years that presynaptic function is target cell specific, the identity of this retrograde messenger(s) is still not known. The long term goal of this project is to determine the postsynaptic molecules that are responsible for target-cell specific short-term plasticity. The synaptic cell adhesion molecules neuroligin 1 and SynCAM have recently been shown to induce presynaptic differentiation in neurons when expressed in non-neuronal cells in co-culture. This shows that neuroligin 1 and SynCAM are sufficient to trigger presynaptic differentiation, even in the absence of other normal components of the postsynaptic terminal. While neuroligin 1 and SynCAM have each been shown to be sufficient to induce formation of presynaptic terminals in neurons (referred to here as hemisynapses) that are functional at a basic level, it is not known whether they are sufficient to enable presynaptic terminals of hemisynapses to have the same complex presynaptic properties that neuron-neuron synapses possess. In particular, has not previously been shown whether they are capable of evoked neurotransmitter release, and if so, whether they have a similar release probability and mechanisms of short-term plasticity as neuron-neuron synapses. In this proposal, we will develop the hemisynapse preparation and measure evoked neurotransmitter release and short-term plasticity, in order to test the hypothesis that the cell adhesion molecules that trigger synapse formation are also involved in the retrograde signaling that modulates the functional properties of presynaptic terminals, yet are not sufficient to induce formation of presynaptic terminals with all of the same properties of neuron- neuron synapses. This system will provide a simple but powerful assay for a large range of future experiments investigating the influences of specific cell adhesion molecules, extracellular matrix proteins, neurotrophins, secreted factors, and postsynaptic density components on the formation and function of presynaptic terminals. These experiments address fundamental questions of presynaptic function, synaptic specialization and development that are important to our understanding of circuits in the brain, and which will have implications for learning and memory as well as neurodegenerative diseases and developmental disorders that cause mental retardation. These experiments address fundamental questions of presynaptic function, synaptic specialization and development that are important to our understanding of circuits in the brain, and which will have implications for learning and memory as well as neurodegenerative diseases and developmental disorders that cause mental retardation.