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型谷氨酸受体（iGluR）和调节细胞兴奋性的代谢型谷氨酸受体（mGluR）。iGluR门控细胞外钠和钙进入细胞，而I组mGluR（1，5）导致钙从细胞内储存释放。脑损伤如中风或缺血导致细胞外谷氨酸盐增加、iGluR和mGluR的不受控制的激活以及细胞内钙的毒性积累，这是细胞死亡的基本引发剂。因此，用于治疗脑缺血的治疗策略集中于使用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累，但这些化合物在临床试验中失败。类似地，I组mGluR拮抗剂在模拟缺血研究中具有神经保护性，这可能是由于抑制细胞内钙积累，但将大多数mGluR选择性化合物递送至脑是困难的。我们已经开始探索脑缺血的替代神经保护策略，使用蛋白质组学来鉴定通过在可接近的胞外氨基末端结构域的相互作用来调节I组mGluR信号传导的新蛋白质或肽。我们的第一个蛋白质组学研究集中在第一组mGluR亚型，mGluRS，并揭示了一种新的相互作用与最近克隆的细胞外蛋白，促进细胞存活，ADNP（活性依赖性神经保护蛋白）。ADNP含有8个氨基酸的肽序列（NAPVSIPQ; NAP），其被证明是ADNP中可以诱导神经保护的最小活性元件。临床前实验表明，NAP具有有效的神经保护，记忆增强和神经营养特性。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。本文提出的研究是重要的，因为1）它们开始描绘NAP（一种外源肽）和ADNP（一种内源蛋白）的神经保护机制，2）它们提供了通过胞外结构域的肽或蛋白相互作用对mGluR信号传导进行新调节的证据，以及3）它们提供了脑缺血治疗干预的新方法。

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.