Neuroprotection by Novel Regulators of mGluR Signaling

描述(申请人提供)：谷氨酸激活离子型谷氨酸受体(IGluRs)和代谢型谷氨酸受体(MGluRs)，前者介导快速突触传递，后者调节细胞兴奋性。IGluRs使细胞外的钠和钙进入细胞内，而I组的mGluRs(1，5)则导致细胞内的钙释放。脑损伤，如中风或脑缺血，导致细胞外谷氨酸增加，不受控制地激活iGluRs和mGluRs，并导致细胞内钙的有毒积累，这是细胞死亡的重要启动因素。因此，治疗脑缺血的治疗策略主要集中在使用iGluR和I组mGluR拮抗剂。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，可能是由于抑制了细胞内钙积聚，但大多数mGluR选择性化合物很难被输送到大脑。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新的蛋白质或肽，这些蛋白质或肽通过药物上可访问的细胞外氨基末端区域的相互作用来调节I组mGluR信号。我们最初的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胞外蛋白ADNP(活性依赖神经保护蛋白)之间的一种新的相互作用。ADNP含有一个8个氨基酸的肽序列(NAPVSIPQ；NAP)，它是ADNP中具有神经保护作用的最小活性成分。临床前实验表明，NAP具有强大的神经保护、增强记忆和神经营养作用。然而，NAP或ADNP保护神经的机制尚不清楚。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。本文提出的研究具有重要意义，因为1)它们开始阐明外源性多肽NAP和内源性蛋白质ADNP的神经保护机制；2)它们为细胞外区域多肽或蛋白质相互作用调节mGluR信号提供了证据；3)它们为脑缺血的治疗干预提供了新的途径。

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.