POSH在缺血性神经元损伤中的作用及分子机制

Stroke is a devastating condition that affects people’s wellbeing in China and the world. Understanding the underlying signaling mechanisms for N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity in stroke-related brain damage will not only shed light on the molecular basis for neuronal death after stroke, but also may provide a promising target for the therapy of stroke. POSH (Plenty of SH3s) is a scaffold protein of the JNK signaling pathway. It has been reported previously that infusion of POSH anti-sense oligodeoxynucleotides reduced global ischemic brain injury. However, the roles of POSH in ischemic neuronal injury, and especially in NMDA receptor-dependent physiologic and pathologic processes are still unclear. From our preliminary data, we found that POSH binds to NMDA receptor subunits, NR2A and a neuronal scaffolding protein, postsynaptic density (PSD)-95 in vivo. In this study, we aim to characterize the roles and the underlying molecular mechanisms of POSH in ischemic brain injury using POSH neural-specific knockout mice and both in vitro and in vivo stroke models. We would like to test our hypothesis that POSH recruits a multi-protein complex and plays a role in NR2A-containing NMDA receptor activation as well as JNK pathway activation. This study may also result in a clue in the development of a novel NMDA receptor-based therapy for stroke.

缺血性脑卒中严重危害国人健康。NMDA受体过度活化是缺血性脑损伤最早期发生的病理反应，阐明其中的分子机制有助于更好地理解缺血性脑损伤的致病机理，为临床诊治提供理论基础。有研究报道注射反义核苷酸抑制JNK信号通路支架蛋白POSH，可以减轻神经元缺血性损伤。然而POSH在缺血性脑损伤中的作用还缺乏确凿的体内证据，POSH是否参与调控NMDA受体活性也未见报道。我们前期研究发现POSH存在于成年鼠脑PSD组分中，并且能够与NMDA受体NR2A亚基及PSD95结合。本项目拟通过构建POSH神经系统特异性基因敲除小鼠，结合神经元原代培养及体内外脑缺血模型，研究POSH在缺血性脑损伤中的作用，并进一步利用分子生物学和生物化学手段，结合生物影像学技术，阐明其中的分子机制，探索是否存在一个以POSH为核心的复合体参与缺血后NMDA受体活性调节和JNK信号通路的激活，为临床发现有效的治疗靶点提供理论基础。