AEP酶底物Homer蛋白家族在脑缺血再灌注损伤中的作用及分子机制

Homer蛋白家族在中枢神经系统中具有非常重要的功能，是构成突触后密集区的主要成员，但其与脑卒中等疾病的关系尚不明确。前期研究通过质谱分析发现Homer可能是Asparagine Endopeptidase（AEP）的酶切底物，小鼠脑缺血再灌注损伤后AEP的表达和活性都有所增强，脑组织中的Homer蛋白发生了断裂，因此我们提出假设，在脑缺血再灌注后，细胞内的AEP酶发生活化，切割了包括Homer蛋白在内的酶底物，对疾病的发展造成影响。在本项目中，我们将在前期工作的基础上证实AEP对Homer蛋白的切割作用，鉴定酶切位点，分析该位点在Homer蛋白家族中的意义；探讨 Homer蛋白切割后细胞功能的改变，解释相关的分子机制；分析Homer蛋白切割在脑缺血再灌注损伤过程中所发挥的生物学功能。这些研究不仅有助于加深对Homer蛋白家族功能的理解，也为脑卒中等疾病的致病机制与治疗研究提供新的思路。

The Homer family proteins play important roles in central nervous system. Subcellularly in neurons, Homer is concentrated in postsynaptic structure and consist major part of postsynaptic density. However, their pathophysiological roles in brain stroke has not been clear. Our previous study showed that asparagine endopeptidase (AEP) expression, activation and many other related proteins' cleavage were increased under middle cerebral artery occlusion/reperfusion (MCAO/R). Further, mass spectrometric analysis proved Homer could be a potential enzyme substrate of AEP. In addition, we found that endogenous homer could be cleaved under MCAO/R. These results suggested a probable process in MCAO/R; the activation of AEP leads to the cleavage of its substrate proteins including Homer proteins. In this proposal, we will validate the cleavage of Homer by AEP, characterize the cleavage site(s), and analyze the significance of the sites on the functions of the Homer proteins. On the basis of the above works, we would perform in-depth studies on the biological functions of the Homer proteins and the related mechanisms in brain stroke. We expect this work would provide novel insight into the pathogenesis of stroke and may suggest new candidates for diagnosis and treatment.