ATP9A与ARF1相互作用调控内吞体运输维持神经元功能的机制研究

Endocytosis maintains the homeostasis of intracellular substances and signaling, and abnormalities in this function can lead to many neurological disorders. For the first time, we have identified nonsense mutations in the ATP9A gene from patients and animal models as novel pathogenic factors in neurological inherited diseases such as mental retardation, but the pathogenesis mechanism is not yet clear. Our recent experiments have shown that the deletion or mutations of ATP9A can cause severe neurites damage and low cell viability in the cortical neurons, while its pathogenic mutants has altered intracellular localization and led to abnormal endosomal morphology. By using biochemical and mass spectrometry analysis, we found that ARF1, a vesicle transport associated protein, interacts with ATP9A. Therefore, we hypothesize that ATP9A regulates endosomal trafficking to maintain the morphology and survival of cortical neurons through interacting with ARF1, and the deletion or mutations of ATP9A may lead to abnormal endosomal vesicle transport, which may ultimately cause neurotoxicity. This project aims to investigate the effects of ATP9A deletion or mutations on endosomal transport at animal, cellular and molecular levels, to obtain direct evidence of ATP9A regulation of ARF1, and to elucidate the mechanism of their interactions on endosomal trafficking, neural morphology and survival. It will provide insights for revealing the pathogenesis and potential therapeutic targets of ATP9A mutation in nervous system diseases.

内吞作用维持细胞内物质和信号传递的稳态，该功能异常可导致多种神经系统疾病。我们在前期临床研究和动物模型中首次发现ATP9A基因无义突变是智力障碍等神经系统遗传性疾病的新致病因素，但致病机制尚不明确。近期预实验表明，ATP9A的缺失或突变能够引起大脑皮质神经元突起受损和细胞活力降低，而其致病突变体在细胞内定位发生改变并导致内吞体形态异常，利用生化结合质谱分析筛选出囊泡转运相关蛋白ARF1与ATP9A互作，因此我们推测ATP9A通过ARF1调控内吞体运输维持皮质神经元的形态和存活，其缺失或突变可能导致内吞体囊泡转运异常从而引发神经毒性。本项目拟在动物、细胞和分子层面研究ATP9A缺失或突变对内吞体运输的影响，获得ATP9A调控ARF1的直接证据，并阐明二者的互作对内吞体运输及神经元形态和存活的调控机制，为揭示ATP9A突变在神经系统疾病中的致病机理和潜在治疗靶点提供科学依据。

ATP9A是II类P4-ATPases的磷脂翻转酶，主要参与细胞囊泡运输。我们在前期临床研究和动物模型中首次发现ATP9A基因无义突变是智力障碍等神经系统遗传性疾病的新致病因素，但致病机制尚不明确。预实验表明，ATP9A的缺失引起大脑皮质神经元突起受损和细胞活力降低，而其致病突变体在细胞内定位发生改变并导致内吞体形态异常。利用生化结合质谱分析筛选出囊泡转运相关蛋白ARF1与ATP9A互作，因此我们推测ATP9A通过ARF1调控内吞体运输维持皮质神经元的形态和存活，其缺失或突变可能导致内吞体囊泡转运异常从而引发神经毒性。. 本项目通过细胞内吞实验探索ATP9A缺失和突变对内吞运输影响，确定了ATP9A主要调控神经细胞的内吞循环运输。既往研究表明ATP9A与ARF1互作，但实验发现其对ARF1的表达和活性并无影响；结合文献报道ARF1主要介导高尔基体的逆向运输过程，而ATP9A不与高尔基体共定位也不影响逆向运输。因此ATP9A不是通过ARF1调控内吞体运输并维持神经元功能的，新的调控机制亟待于进一步探索。. 本项目后续在动物组织、细胞和分子层面发现ATP9A能够调节早期和循环内吞体上RAB5和RAB11的活性，并确立了ATP9A在RAB5和RAB11活性依赖性内吞循环途径和神经系统疾病中的调控新机制，为揭示ATP9A突变在神经系统疾病中的致病机理和潜在治疗靶点提供科学依据。