PS1 mediates the neuroprotective functions of the ephrinB/EphB system

描述(申请人提供)：兴奋性毒性，一种由于谷氨酸受体过度激活和氧化应激而导致的神经元损伤形式，是阿尔茨海默病(AD)发病机制中涉及的神经元损伤机制。我们发现，ewitinB家族的配体蛋白可以保护原代培养的神经元免受谷氨酸和氧化应激诱导的死亡。EphinB配体的神经保护作用由其受体(EphB受体，EphBRs)介导，并依赖于参与家族性AD(FAD)的蛋白PS1。有趣的是，eaffinB的神经保护作用依赖于两个PS1等位基因，因为缺乏一个等位基因(单倍体功能不全)会导致eaffinB神经保护的严重降低。此外，我们还获得了PS1的FAD突变体干扰eaffinB依赖的神经保护作用的初步数据，该分泌酶活性可能参与了ewitinBL/EphBR系统的神经保护功能。在这里，我们建议进一步研究PS1 FAD突变体和β-分泌酶对ewitinBls神经保护功能的影响，并阐明PS1介导这一功能的分子机制。我们将探讨PS1是否调节EphBRs与ePhinBls的结合，以及ewitinBL诱导的EphB和NMDA受体的磷酸化。为此，我们将使用我们的PS1基因敲除和FAD突变敲入转基因小鼠群体以及我们实验室提供的EphBR基因敲除群体的皮质原代神经元培养。我们还将使用我们的小鼠模型在体内检测EphriBL/EphBR系统的神经保护功能，并询问PS1 FAD突变是否影响这一功能。最后，我们将询问PS2，也参与FAD的PS1的同源物，是否也可能参与ewitinB的神经保护。公共卫生相关性：兴奋性毒性和氧化应激是导致阿尔茨海默病(AD)神经退行性变的神经毒性机制。我们发现，一种名为ewitinB的蛋白质具有神经保护功能，可以将神经元从兴奋性毒性和氧化死亡中拯救出来；ewitinB的这些神经保护作用依赖于PS1，一种与AD有关的蛋白质。我们的发现对基因突变导致神经变性的机制有影响，并可能为AD的治疗干预提供新的靶点。

DESCRIPTION (provided by applicant): Excitotoxicity, a form of neuronal damage due to excessive activation of glutamate receptors and oxidative stress are mechanisms of neuronal injury implicated in the pathogenesis of Alzheimer's disease (AD). We found that the ephrinB family of ligand proteins protects primary neuronal cultures from both glutamate- and oxidative stress- induced death. The neuroprotective activities of ephrinB ligands (ephrinBLs) are mediated by their receptors (EphB receptors, EphBRs) and depend on PS1, a protein involved in familial AD (FAD). Interestingly, the neuroprotective effect of ephrinB depends on both PS1 alleles because absence of one allele (haploinsufficiency) results in severe reduction of the ephrinB neuroprotection. Furthermore, we obtained preliminary data that FAD mutants of PS1 interfere with the ephrinB-dependent neuroprotection and that -secretase activity may be involved in the neuroprotective functions of the ephrinBL/EphBR system. Here we propose to further investigate the effects of PS1 FAD mutants and ?-secretase on the neuroprotective function of ephrinBLs and to elucidate molecular mechanisms by which PS1 mediates this function. We will explore whether PS1 regulates the binding of ephrinBLs to EphBRs and the ephrinBL-induced phosphorylation of both EphB and NMDA receptors. To this end we will use cortical primary neuronal cultures from our PS1 knockout and FAD mutant knock-in transgenic mouse colonies as well as EphBR knock-out colonies available in our laboratory. We will also use our mouse models to examine the neuroprotective function of the ephriBL/EphBR system in vivo and to ask whether PS1 FAD mutations affect this function. Finally, we will ask whether PS2, a homologue of PS1 also involved in FAD, may also be involved in the ephrinB neuroprotection. PUBLIC HEALTH RELEVANCE: Excitotoxicity and oxidative stress are neurotoxic mechanisms implicated in the neurodegeneration of Alzheimer's disease (AD). We found that a protein called ephrinB, has neuroprotective functions and rescues neurons from excitotoxic and oxidative death; these neuroprotective effects of ephrinB depend on PS1, a protein involved in AD. Our findings have implications for the mechanisms by which genetic mutations cause neurodegeneration and may provide novel targets for therapeutic intervention in AD.