线粒体转运停滞促进神经元线粒体自噬在缺血性脑损伤中的作用及机制研究

Our previous works indicated that mitophagy protected against ischemic brain injuyr, suggesting that mitophagy could be a potential drug target for stroke therapy. However, the intracellular process of mitophagy in neurons is far from being understood. Our preliminary data found that OGD-reperfusion induced mitochondrial transport stablization. By impairing the microtubes in neurons, our prelimary experiments suggested that mitochondrial stablization promotes mitophagy in ischemic neurons. The mechanisms underlying mitochondrial transport-induced mitophagy are not fully understood. Our previous investigation, as well as others, suggest that the endoplasmic reticulum functions are key factor in mitophagy regulation. We interestingly found that the ER protein Calreticulin may interact with the mitophagy receptor Nix and subsequently promote mitochondrial stablization. This process might be necessary for mitophagy induction in ischemic neurons. By employing multiple assays including virus-infected expression and optogenetic technology, we aimed to fully identify the acceleration effect of mitochondrial stablization on mitophagy induction. In addition, we intend to explore the mechanisms by which Calreticulin/Nix binding inducing mitochondrial transport stablazation. These investigations will provide a novel therapeutic target against ischemic stroke.

申请人的前期工作表明线粒体自噬在缺血性脑损伤过程中发挥重要神经保护作用，提示其是一种潜在的脑缺血药物治疗靶点。然而，神经元中线粒体自噬发生的胞内过程尚不清楚。我们的预实验研究发现，OGD复灌导致神经元线粒体转运停滞，并且通过破坏微管蛋白初步发现线粒体转运停滞促进了线粒体自噬。线粒体转运调控线粒体自噬的机制尚不清楚，文献报道及申请人的前期工作均提示内质网功能是影响线粒体自噬的重要因素。预实验有趣地发现，内质网蛋白Calreticulin可能通过与线粒体自噬蛋白Nix相互作用调控缺血复灌过程中的线粒体转运，进而促进线粒体自噬。因此，本研究拟利用Nix敲除小鼠，结合药理学、病毒转染表达、光遗传学技术等手段，充分明确脑缺血复灌过程中线粒体转运停滞对线粒体自噬的促进作用，并初步阐明Nix与Calreticulin的相互作用对线粒体转运的调控机制。研究结果有望为干预缺血性脑损伤提供一种新的药物靶点。

缺血性脑卒中过程伴有线粒体自噬激活，后者通过清除损伤线粒体发挥神经保护作用。然而脑缺血过程中神经元线粒体自噬发生的细胞内机制尚不清楚，这为基于线粒体自噬的抗脑卒中药物靶点发现带来了困难。尤其是，成熟神经元中约有一半以上的线粒体分布在较长的轴突内，这部分线粒体是否以及如何清除，一直是学界争议的焦点。本项目通过体外神经元原代培养，结合氧糖剥夺复灌模型，发现缺血神经元轴突中的线粒体没有发生原位的线粒体自噬，而是通过逆向转运运动至神经元胞体进而进行自噬降解。阻断轴突线粒体逆向转运阻碍了缺血神经元线粒体自噬发生，而增加轴突线粒体逆向转运则促进线粒体自噬，并且发减少缺血诱导的神经元凋亡，改善其能量代谢。本研究揭示了缺血神经元线粒体自噬调控的新规律，为寻找干预缺血性神经损伤的药物提供了新思路。