Distinct role of Neurabin and Spinophilin in Synaptic Transmission and Plasticity

描述（由申请人提供）：大量证据表明，突触功能在阿尔茨海默病和其他神经退行性疾病中严重受损，甚至在这些疾病的早期阶段就导致认知缺陷。众所周知，蛋白磷酸酶-1 （PP1）在突触功能中起着关键作用。然而，我们的初步数据表明，至少有两个突触PP1群体可以在突触传递中发挥不同的功能。我们的直接目标是阐明这两种突触PP1群体的不同靶向和信号传导机制。我们的长期目标是应用这些知识来理解如何在疾病中预防突触功能中PP1信号的损伤。我们新获得的初步数据表明，两个不同的PP1库，可能分别被神经滨素和嗜脊髓蛋白靶向，在突触传递中具有相反的功能，在长期抑郁（LTD）中发挥不同的作用。在这个提议中，我们假设神经素和嗜脊髓蛋白可以通过微靶向它们的载物（PP1）到突触内不同的微室，分别作用于不同的底物，即PKC1上的Ser657（间接作用于GluR2上的Ser880）和GluR1上的Ser831，对基础突触传递（Aim 1）发挥相反的作用。为了响应LTD刺激（Aim2），我们提出验证我们的假设，即神经滨素会转运到PSD部分使GSK32去磷酸化，导致突触抑制，而嗜脊髓素在这一过程中没有发挥作用。在这两个目标中，神经素和嗜脊髓素介导其不同作用的关键区域将通过电生理记录和最先进的分子替代方法的结合来阐明。在Aim3中，我们将假设神经滨素而非嗜脊髓蛋白在LTP表达中起负向作用。我们建议确定LTP刺激利用神经素磷酸化机制来克服Nrb/PP1复合物对正常LTP发生的抑制作用。最后，我们还将验证Nrb/PP1修饰CaMKII和/或GSK32在LTP中的抑制功能的假设。从这些研究中获得的结果将更好地理解以下生物学机制：(1)调节PP1与不同结合蛋白相互作用的差异底物特异性；(2)神经滨素和嗜脊髓蛋白在突触功能中的关键功能的结构基础；(3)为神经退行性疾病患者认知缺陷的治疗提供新的见解。公共卫生相关性：大量证据表明，突触功能在阿尔茨海默病和其他神经退行性疾病中严重受损，甚至在这些疾病的早期阶段就导致认知缺陷。我们提出的研究是检查磷酸酶信号机制的突触功能。从这些研究中获得的结果将为神经退行性疾病患者认知缺陷的治疗提供分子见解。

DESCRIPTION (provided by applicant): Considerable evidence suggests that synaptic function is severely compromised in Alzheimer's disease and other neurodegenerative diseases, leading to cognitive defects even during the early stages of these diseases. It is well known that protein phosphatase-1 (PP1) plays a critical role in synaptic function. However, our preliminary data indicates that there are at least two synaptic PP1 populations which can exert differential functions on synaptic transmission. Our immediate goal is to elucidate the differential targeting and signaling mechanisms underlying these two synaptic PP1 populations. Our longer-term goal is to apply this knowledge in understanding how impairment of PP1 signaling in synaptic function can be prevented in diseases. Our newly acquired preliminary data suggest that two distinct pools of PP1, probably targeted respectively by neurabin and spinophilin, have opposite functions in synaptic transmission and play differential roles in long term depression (LTD). In this proposal, we hypothesize that neurabin and spinophilin can exert their opposite effects on basal synaptic transmission (Aim 1) through micro-targeting their cargoes (PP1) to distinct micro-compartments within synapses, acting on different substrates, i.e. Ser657 on PKC1 (and indirectly on Ser880 on GluR2) and Ser831 on GluR1, respectively. In response to LTD stimulus (Aim2), we propose to test our hypothesis that neurabin will traffic to PSD fraction to dephosphorylate GSK32, leading to synaptic depression while spinophilin does not play a role in this process. Critical domains on neurabin and spinophilin mediating their distinct effects will be elucidated in these two aims by a combination of electrophysiological recording and the state-of-the-art molecular replacement approach. In Aim3, we will hypothesize that neurabin, but not spinophilin, plays a negative role in LTP expression. We propose to determine the phosphorylation mechanism on neurabin by which LTP stimulus uses to overcome the inhibitory effects of Nrb/PP1 complex for normal LTP to occur. Finally we will also test the hypotheses that Nrb/PP1 modifies CaMKII and/or GSK32 for its inhibitory function in LTP. The results obtained from these studies will provide a better understanding of biological mechanisms that (1) regulate PP1 interaction with different binding proteins for differential substrate specificity, (2) structural basis for the critical functions of neurabin and spinophilin in synaptic functions; and (3) provide insights into therapeutic cures for the cognitive defects in patients with neurodegenerative diseases. PUBLIC HEALTH RELEVANCE: Considerable evidence suggests that synaptic function is severely compromised in Alzheimer's disease and other neurodegenerative diseases, leading to cognitive defects even during the early stages of these diseases. Our proposed study is to examine the phosphatases signaling mechanisms underlying synaptic functions. The results obtained from these studies will provide molecular insights into therapeutic cures for the cognitive defects in patients with neurodegenerative diseases.