PS1 mediates the neuroprotective functions of the ephrinB/EphB system

描述（由申请人提供）：兴奋毒性是一种由谷氨酸受体过度激活和氧化应激引起的神经元损伤形式，是阿尔茨海默病（AD）发病机制中涉及的神经元损伤机制。我们发现配体蛋白ephrinB家族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。ephrinB配体（ephrinBLs）的神经保护活性由其受体（EphB受体，EphBRs）介导，并依赖于PS1，一种参与家族性AD （FAD）的蛋白。有趣的是，ephrinB的神经保护作用取决于两个PS1等位基因，因为缺少一个等位基因（单倍功能不全）会导致ephrinB神经保护功能严重降低。此外，我们获得了PS1 FAD突变体干扰ephrinb依赖性神经保护的初步数据，并且-分泌酶活性可能参与了ephrinBL/EphBR系统的神经保护功能。在此，我们建议进一步研究PS1 FAD突变体和？-分泌酶对ephrinBLs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ephrinBLs与EphBRs的结合以及ephrinBLs诱导的EphB和NMDA受体的磷酸化。为此，我们将使用我们的PS1敲除和FAD突变敲入转基因小鼠菌落以及我们实验室提供的EphBR敲除菌落的皮质原代神经元培养物。我们还将使用我们的小鼠模型来检测体内ephriBL/EphBR系统的神经保护功能，并询问PS1 FAD突变是否会影响这种功能。最后，我们将探讨PS1的同系物PS2是否也参与了ephrinB的神经保护作用。公共卫生相关性：兴奋毒性和氧化应激是与阿尔茨海默病（AD）神经变性有关的神经毒性机制。我们发现一种叫做ephrinB的蛋白质具有神经保护功能，并能使神经元免于兴奋性毒性和氧化性死亡；ephrinB的这些神经保护作用依赖于PS1，一种与AD有关的蛋白质。我们的研究结果揭示了基因突变导致神经退行性变的机制，并可能为阿尔茨海默病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.