Polarity determinants in synaptic stability and plasticity

 描述(申请人提供)：突触的稳定性和可塑性对认知功能都很重要。可塑性对于学习是必要的，而稳定形成的突触被认为编码了长期记忆。然而，尚不清楚神经元如何维持这种微妙的平衡，并在相距仅几微米的突触中实现稳定和可塑性。显然，需要高度的区隔，这使得极性蛋白质成为发挥这一功能的理想候选者，因为它们起到分离和维持不同膜结构域的作用。事实上，我们之前已经证明了一类被称为PAR(分割缺陷)蛋白的极性蛋白在树突棘的形态发生中起着关键作用，其中Par1、Par3和Par6对这一过程起着重要的作用。有趣的是，我们的初步研究表明，成熟神经元中的大部分脊椎由Par3和Par6主导，而一小部分脊椎由Par1主导。这种分布模式类似于PAR蛋白在发育中的受精卵和上皮细胞中的分布模式，其中Par1和Par3/6复合体表现出相反的定位，相互排除在各自的结构域中。此外，我们先前的研究表明，Par3和Par6与非典型PKC(APKC)形成复合体，促进脊柱的稳定和成熟，而我们的初步结果表明，Par1促进脊柱的可塑性。这些数据提出了令人兴奋的可能性，即Par3/6复合体和Par1调节脊柱稳定性和可塑性之间的平衡，其中Par3/6占优势的脊柱更稳定，Par1占优势的脊柱更具可塑性。我们计划通过两个目标来检验这一最重要的假设。在AIM 1中，我们将测试Par1促进突触可塑性的假设，以及通过增加PSD支架的动力学和排除Par3/6复合体来维持可塑性的假设。在目标2中，我们将检验这样的假设，即Par3/Par6/aPKC复合体促进突触稳定，并且稳定的部分维持是通过从脊髓中排除Par1来实现的。我们将利用先进的分子成像技术，包括FRET、FRAP、荧光诱导蛋白(FLOPS)和双光子谷氨酸去化。此外，我们将在活体小鼠身上使用双光子成像来直接测试我们的假设 表现得像动物一样。我们将把这些成像方法与生化分析和电生理学结合起来。这种跨学科的方法将使我们能够从根本上深入了解突触稳定和可塑性的细胞和分子机制。此外，多条证据表明PAR极性蛋白在包括精神分裂症、自闭症、严重抑郁障碍和双相情感障碍在内的神经精神障碍中发挥着重要作用。因此，我们的研究将为突触的可塑性和稳定性提供机械性的见解，并可能揭示影响人脑的几种破坏性异常。

 DESCRIPTION (provided by applicant): The stability and plasticity of synapses are both important for cognitive functions. Plasticity is necessary for learning, while stably formed synapses are believed to encode for long term memory. Yet it is unclear how neurons can maintain this delicate balance and achieve both stability and plasticity in synapses just a few microns apart. Clearly, a high level of compartmentalization is required, which makes polarity proteins ideal candidates to function in this capacity, as they serve to separate and maintain distinct membrane domains. Indeed, we previously showed that a class of polarity proteins called Par (partitioning defective) proteins plays a key role in dendritic spine morphogenesis, with Par1, Par3 and Par6 important for this process. Interestingly, our preliminary studies show that most of the spines in mature neurons are dominated by Par3 and Par6, whereas a smaller fraction of spines are dominated by Par1. This distribution pattern resembles that of Par proteins in developing zygotes and epithelial cells, where Par1 and the Par3/6 complex show opposite localization by mutually excluding each other from their respective domains. Furthermore, our previous studies suggest that Par3 and Par6, which form a complex with atypical PKC (aPKC), promote spine stability and maturation, whereas our preliminary results suggest that Par1 promotes spine plasticity. These data raise the exciting possibility that the Par3/6 complex and Par1 regulate the balance between stability and plasticity of spines, with Par3/6-dominant spines being more stable and Par1-dominant spines being more plastic. We plan to test this overarching hypothesis through two aims. In aim1, we will test the hypothesis that Par1 promotes synaptic plasticity and that plasticity is maintained by increasing the dynamics of the PSD scaffold and by excluding the Par3/6 complex. In aim 2, we will test the hypothesis that the Par3/Par6/aPKC complex promotes synaptic stability and that stability is maintained in part by excluding Par1 from the spines. We will utilize advanced molecular imaging techniques, including FRET, FRAP, fluorescent light-inducible proteins (FLIPs) and 2-photon glutamate uncaging. In addition, we will use 2-photon imaging in live mice to directly test our hypothesis in behaving animals. We will combine these imaging approaches with biochemical analysis as well as electrophysiology. This interdisciplinary approach will allow us to gain fundamental insight into the cellular and molecular mechanisms of synaptic stability and plasticity. Moreover, multiple lines of evidence are pointing to an important role for Par polarity proteins in neuropsychiatric disorders, including schizophrenia, autism, major depressive disorder and bipolar disorder. Thus, our studies will provide mechanistic insight into synaptic plasticity and stability and may shed light on several devastating abnormalities that affect the human brain.