Distinct role of Neurabin and Spinophilin in Synaptic Transmission and Plasticity

描述(申请人提供)：大量证据表明，阿尔茨海默病和其他神经退行性疾病的突触功能严重受损，即使在这些疾病的早期阶段也会导致认知缺陷。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种群可以在突触传递中发挥不同的功能。我们的近期目标是阐明这两个突触PP1群体背后的不同靶向和信号机制。我们的长期目标是将这一知识应用于理解如何在疾病中预防突触功能中PP1信号的损害。我们新获得的初步数据表明，两个不同的PP1池，可能分别以神经肽和亲脊髓蛋白为靶点，在突触传递中具有相反的功能，并在长期抑郁(LTD)中发挥不同的作用。在这一建议中，我们假设神经肽和亲棘素可以通过微靶向突触内不同的微室(PP1)作用于突触内不同的微室，对基础突触传递(AIM 1)发挥相反的作用，分别作用于不同的底物，即PKC1上的Ser657(GluR2上的Ser880)和GluR1上的Ser831。为了响应LTD刺激(AIM2)，我们建议验证我们的假设，即Neurabin将流量到PSD部分，使GSK32去磷酸化，导致突触抑制，而亲脊髓蛋白在这一过程中不起作用。我们将结合电生理记录和最先进的分子置换方法，阐明神经肽和亲棘素的关键结构域在这两个目标中的不同作用。在Aim3中，我们将假设Neurabin，而不是Spin，在LTP的表达中起负面作用。我们建议确定LTP刺激用来克服NRB/PP1复合体对正常LTP发生的抑制作用的Neurabin上的磷酸化机制。最后，我们还将验证NRB/PP1修饰CaMKII和/或GSK32的假设，以实现其在LTP中的抑制功能。这些研究的结果将有助于更好地理解以下生物学机制：(1)调节PP1与不同结合蛋白的相互作用以实现不同底物的特异性；(2)神经肽和亲脊髓蛋白在突触功能中关键功能的结构基础；(3)为治疗神经退行性疾病患者的认知缺陷提供见解。与公共卫生相关：大量证据表明，阿尔茨海默病和其他神经退行性疾病的突触功能严重受损，即使在这些疾病的早期阶段也会导致认知缺陷。我们建议的研究是为了研究突触功能背后的磷酸酶信号机制。这些研究的结果将为治疗神经退行性疾病患者的认知缺陷提供分子方面的见解。

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.