ATP13A2通过调节锌离子稳态参与线粒体内Aβ产生和聚集的机制研究

β-淀粉样蛋白(Aβ)在线粒体内沉积是导致阿尔茨海默病(AD)脑内神经元死亡及其功能障碍的重要原因之一。研究表明，细胞内锌离子稳态失衡是导致线粒体电子传递链损伤，诱发氧化应激，并促进Aβ的聚集的关键因素。因此，调控细胞内锌离子稳态成为抑制Aβ在线粒体内沉积的有效途径。新近研究表明，ATP13A2具有维持细胞内锌离子的稳态、保护线粒体的重要功能。我们前期研究发现，ATP13A2在AD脑内及体外培养的AD细胞模型中均显著升高，但其是否参与AD病理过程及其具体机制尚未见报道。本项目拟采用ATP13A2基因敲除的APP/PS1转基因小鼠，以及体外构建的ATP13A2基因缺失的神经元为研究对象，旨在阐明“ATP13A2调控细胞内锌离子稳态→减少线粒体内Aβ的聚集→稳定线粒体功能→改善AD病理进程”的具体机制，为确立ATP13A2作为AD防治的新靶点提供充分的理论和实验依据。

Alzheimer’s disease (AD) pathogenesis is believed to be triggered by the amyloid-β (Aβ) accumulation. Overproduction of Aβ and the failure of Aβ clearance have been observed in mitochondria of AD brains. Mitochondrial Aβ presence causes oxidative damage and mitochondrial respiratory dysfunction, activating a cascade of events leading to neurodegeneration. Zinc binding with Aβ induces aggregation and extracellular plaque formation. More importantly, a role for cytosolic zinc with Aβ accumulation has been shown to correlate with reactive oxygen species (ROS) production rates, and alters mitochondrial membrane potential, which results in mitochondrial dysfunction and fragmentation. Recently, ATP13A2 is found to be associated with zinc homeostasis and remediates mitochondrial dysfunction. An increased accumulation of failing mitochondria in ATP13A2−/− cells in conditions of zinc exposure may contribute to the increased sensitivity of zinc. ATP13A2, a transmembrane protein of 1180 amino acids, belongs to the P5 type pump ATPases and is highly expressed in the brain. The promoter region of the human ATP13A2 gene contains hypoxia response elements, which can bind to the transcription factor hypoxia inducible factor1α (HIF-1α). Hypoxic conditions up-regulate transcription of the ATP13A2 gene. Several physical interactors of ATP13A2 are involved inregulation of mitochondrial bioenergetics, and evidence from genetic interaction studies in yeast also provides a link between YPK9 and mitochondrial clearance. Therefore, in the present project, we would like to generate new animal models, ATP13A2 conditional-knockout and human APP/PS1 transgenic (ATP13A2flox/flox:CAMKII/APP/PS1) mice, to analyze whether ATP13A2 could maintain the balance of zinc in cytoplasm to protect the mitochondrial function and inhibit Aβ accumulation. In addition, we will use genome editing technology to knockdown ATP13A2 in familial Alzheimer’s disease (fAD) iPSC-derived neurons and explore the mechanism of the ATP13A2 involved in zinc transport and Aβ accumulation/clearance in mitochondria. This study will be helpful to understand whether ATP13A2 is involved in brain zinc metabolism and to provide a clue for ATP13A2 to AD prevention and therapy.