Exploring the modulation of synaptic/extrasynaptic NMDAR balance as a novel therapeutic strategy in Alzheimer's disease and other neurodegenerations

兴奋性毒性被定义为由过量的多巴胺能神经递质引起的神经元功能/结构的恶化。 刺激.它是许多神经退行性疾病（ND）的共同主要病理标志，包括 阿尔茨海默氏病（AD）、亨廷顿氏病（HD）和肌萎缩侧索硬化症（ALS）。兴奋性毒性是 主要由NMDA型谷氨酸受体（NMDAR）的激活介导。然而，NMDAR 功能对于正常的神经元功能是必不可少的。这一难题的解释是， 分离在两个群体中：突触（sNMDAR）和突触外（exNMDAR）。虽然sNMDAR是 与促存活信号传导相关，exNMDAR的过度活化触发兴奋性毒性。因此，exNMDAR是 在广泛的ND中具有明显的药理学靶点，事实上，强烈阻断NMDAR活性 改善AD和HD小鼠模型中的认知缺陷。然而，exNMDAR的选择性抑制是不可能的。 具有挑战性，并且绝大多数NMDAR拮抗剂在临床上由于由NMDAR介导的副作用而失败。 SNMDAR阻断。我们建议测试一种新的治疗策略，其基础是s-和exNMDAR 不是独立的群体。相反，s-和exNMDAR池在生理上通过以下方式连接： 横向扩散我们推测，将s/exNMDAR平衡向突触表达转移将是 有益的双重（i）促进存活级联（sNMDAR介导的）和（ii）减少促死亡信号传导 （exNMDAR介导的）。我们非常适合测试这种策略，因为我们以前已经确定了几个 控制s/exNMDAR平衡的机制。这些包括不同的蛋白质相互作用， NMDAR的GluN 2B亚基和GluN 2B上促进sNMDAR的特定磷酸化（在S1480处） 突触外位点的清除和受体稳定。该提案的目的是验证通过阻止sNMDAR清除和/或促进exNMDAR重新插入来减少兴奋性毒性的原理证明。 是一种有效的治疗方法。在目标1中，我们将评估新的分子工具， 调节培养物和体内s/exNMDAR平衡，包括（i）小干扰肽（sIP）和（ii） 药理学调节GluN 2B磷酸化。我们的研究包括重新利用一种抗肿瘤药物 目前处于临床试验的1/2期。此外，我们将使用蛋白质组学来比较翻译后修饰 的s-vs. exNMDAR谱，旨在确定调节平衡的新机制。在目标2中，我们 评估该策略作为ND常见治疗策略的适用性。首先，我们将测试 我们的工具，在改善兴奋性毒性介导的病理结果，在几个模型的AD，无论是在文化 和体内。最后，我们将在HD模型（与兴奋性毒性相关）的原代培养物中使用我们的策略。 和帕金森病（兴奋性毒性不是主要的病理机制）。如果成功的话，这项建议，根据 通过调节NMDAR运输而不是通过抑制NMDAR功能来减少兴奋性毒性，将具有 开创性的翻译影响的识别创新疗法的广泛的ND。

Excitotoxicity is defined as the deterioration of neuronal function/structure caused by excessive glutamatergic stimulation. It is a shared major pathological hallmark in many neurodegenerative diseases (ND), including Alzheimer’s disease (AD), Huntington’s disease (HD), and Amyotrophic Lateral Sclerosis (ALS). Excitotoxicity is mostly mediated by the activation of the NMDA-type of glutamate receptors (NMDARs). However, the NMDAR function is indispensable for normal neuronal function. This conundrum is explained by the fact that NMDARs are segregated in two populations: synaptic (sNMDARs) and extrasynaptic (exNMDARs). While sNMDARs are linked to pro-survival signaling, over-activation of exNMDARs triggers excitotoxicity. Therefore, exNMDAR are obvious pharmacological targets in a broad range of ND and, in fact, blocking NMDAR activity strongly ameliorates cognitive defects in AD and HD mouse models. However, selective inhibition of exNMDARs is challenging, and the vast majority of NMDAR antagonists have failed in clinic due to side effects mediated by sNMDAR blockade. We propose to test a novel therapeutic strategy based on the fact that s- and exNMDARs are not independent populations. On the contrary, s- and exNMDARs pools are physiologically connected via lateral diffusion. We hypothesize that shifting the s/exNMDAR balance towards synaptic expression would be beneficial two-folds (i) promoting survival cascades (sNMDAR-mediated) and (ii) decreasing pro-death signaling (exNMDAR-mediated). We are ideally suited to test this strategy because we have previously identified several of the mechanisms controlling s/exNMDAR balance. Those include different protein interactions with the GluN2B-subunit of NMDARs and a particular phosphorylation on GluN2B (at S1480) that promotes sNMDAR clearance and receptor stabilization at extrasynaptic sites. The goal of this proposal is to validate the proof-of-principle that reducing excitotoxicity by preventing sNMDAR clearance and/or promoting exNMDAR reinsertion into synaptic sites is an effective therapeutic strategy in ND. In Aim 1, we will evaluate novel molecular tools to modulate s/exNMDAR balance in culture and in vivo, including (i) small interfering peptides (sIPs) and (ii) pharmacology to modulate GluN2B phosphorylation. Our study includes the repurposing of an anti-tumoral drug currently in phase 1/2 of clinical trial. Also, we will use proteomics to compare the posttranslational modification profile of s- vs. exNMDARs, aiming to identify novel mechanisms regulating the balance. In Aim 2, we will evaluate the suitability of this strategy as a common therapeutic strategy in ND. First, we will test the efficacy of our tools in ameliorating excitotoxicity-mediated pathological outcomes in several models of AD, both in culture and in vivo. Finally, we will use our strategy in primary cultures from models of HD (associated by excitotoxicity) and Parkinson’s disease (excitotoxicity is not a primary pathomechanism). If successful, this proposal, based on reducing excitotoxicity by regulating NMDAR trafficking but not by inhibiting NMDAR function, will have a groundbreaking translational impact on the identification of innovative therapeutics for a wide range of ND.