Neuroprotection by Novel Regulators of mGluR Signaling

描述（由申请人提供）：谷氨酸激活介导快速突触传递的离子性谷氨酸受体（iGluRs）和调节细胞兴奋性的代谢性谷氨酸受体（mGluRs）。iGluRs阻止细胞外钠和钙进入细胞，而I组mGluRs（1,5）导致钙从细胞内储存的释放。脑损伤如中风或缺血导致细胞外谷氨酸增加，iGluRs和mGluRs的不受控制的激活，以及细胞内钙的毒性积累，这是细胞死亡的重要发起者。因此，治疗脑缺血的治疗策略集中在使用iGluR和I组mGluR拮抗剂上。虽然iGluR拮抗剂在模拟缺血研究中具有神经保护作用，可能是由于抑制细胞内钙积聚，但这些化合物在临床试验中失败了。类似地，I组mGluR拮抗剂在模拟缺血研究中具有神经保护作用，可能是由于抑制细胞内钙积累，但大多数mGluR选择性化合物递送到大脑很困难。我们已经开始探索脑缺血的替代神经保护策略，使用蛋白质组学来识别通过药理学上可达的细胞外氨基末端区域的相互作用调节I组mGluR信号的新蛋白质或肽。我们的第一个蛋白质组学研究集中在I组mGluR亚型，mGluRS，并揭示了与最近克隆的促进细胞存活的细胞外蛋白ADNP（活性依赖性神经保护蛋白）的新的相互作用。ADNP含有一个8个氨基酸的肽序列（NAPVSIPQ； NAP），这是ADNP中能诱导神经保护的最小活性元素。临床前实验表明，NAP具有有效的神经保护、增强记忆和神经营养作用。然而，NAP或ADNP的神经保护机制尚不清楚。我们的初步数据表明，NAP和ADNP的神经保护机制之一是调节I组mGluR信号。本文提出的研究很重要，因为1)它们开始描述外源性肽NAP和内源性蛋白ADNP的神经保护机制，2)它们为细胞外区域肽或蛋白相互作用对mGluR信号的新调控提供了证据，3)它们为脑缺血的治疗干预提供了新的方法。

DESCRIPTION (provided by applicant): Glutamate activates ionotropic glutamate receptors (iGluRs) that mediate fast synaptic transmission, and metabotropic glutamate receptors (mGluRs) that modulate cell excitability. The iGluRs gate extracellular sodium and calcium entry into the cell, while the Group I mGluRs (1, 5) lead to the release of calcium from intracellular stores. Brain injury such as stroke or ischemia leads to increased extracellular glutamate, uncontrolled activation of iGluRs and mGluRs, and the toxic accumulation of intracellular calcium that is an essential initiator of cell death. Thus therapeutic strategies for the treatment of brain ischemia have focused on the use of iGluR and Group I mGluR antagonists. While iGluR antagonists are neuroprotective in modeled ischemia studies, likely due to inhibition of intracellular calcium accumulation, these compounds have failed in clinical trials. Similarly, Group I mGluR antagonists are neuroprotective in modeled ischemia studies, likely due to inhibition of intracellular calcium accumulation, yet delivery of most mGluR-selective compounds to the brain is difficult. We have begun to explore alternative neuroprotective strategies for brain ischemia using proteomics to identify novel proteins or peptides that modulate Group I mGluR signaling via interactions at the pharmacologically accessible extracellular amino terminal domain. Our first proteomic studies focused on the Group I mGluR subtype, mGluRS, and revealed a novel interaction with a recently cloned extracellular protein that promotes cell survival, ADNP (activity-dependent neuroprotective protein). ADNP contains an eight amino acid peptide sequence (NAPVSIPQ; NAP) that was shown to be the smallest active element of ADNP that can induce neuroprotection. Preclinical experiments show that NAP has potent neuroprotective, memory enhancing and neurotrophic properties. However, the mechanisms that underlie neuroprotection by NAP or ADNP are not known. Our preliminary data suggest that one mechanism of neuroprotection by NAP and ADNP is to regulate Group I mGluR signaling. The research studies proposed herein are important because 1) they begin to delineate the mechanisms of neuroprotection by NAP, an exogenous peptide, and ADNP, an endogenous protein, 2) they provide evidence for the novel regulation of mGluR signaling by peptide or protein interactions at the extracellular domain, and 3) they offer new approaches for therapeutic intervention in brain ischemia.