线粒体功能蛋白Tom70/MICU1在心肌缺血/再灌注损伤中的作用及机制研究

Myocardial ischemia/reperfusion (MI/R) injury is closely linked with the prognosis for ischemic heart disease patients. Ca2+ overload is a main contributor to mitochondria damage hence cardiomyocyte dysfunction in MI/R. Very recently, MICU1 has been identified as an important regulator of mitochondria Ca2+ homeostasis. Inhibition of mitochondrial MICU1 expression will lead to Ca2+ overload. However, the function of MICU1 in MI/R and its regulatory mechanism remain unidentified. Our previous studies suggested that MI/R caused significant reduction of MICU1 in mitochondria, but not in total cardiac tissues, indicating the underlying mechanism related to the mitochondrial translocation of MICU1 in MI/R. It is well known that the translocation of almost all the pre-proteins into mitochondria needs the recognition of Tom system, and Tom70 is one important importer receptor of this complex. However, whether Tom70 possesses critical roles in the mitochondrial translocation of MICU1 after MI/R is also far from clear. Interestingly, mitochondrial expression of Tom70 was markedly suppressed in MI/R, and Tom70 deficiency significantly reduced mitochondrial MICU1 content, revealing the critical role of Tom70 in the mitochondrial translocation of MICU1. With the co-immunoprecipitation assay, we also found that MICU1 could successfully bind to Tom70. Therefore, we speculate that MI/R significantly depresses mitochondrial expression of Tom70, consequently disturbing mitochondrial translocation of MICU1 and inhibiting its function, then leading to mitochondria Ca2+ overload, and ultimately inducing myocardial injury. By establishing MI/R mouse model and using genetic interference technology, we attempt to carry out the experimental studies on levels of body, cell and molecule. These will give us new ideas for exploring novel role of Tom70/MICU1 pathway and treatment of MI/R injury.

心肌缺血/再灌注（MI/R）与冠心病愈后紧密相关。Ca2+超载是再灌时线粒体损伤与细胞死亡重要原因。最新研究表明，MICU1是一种线粒体Ca2+稳态调节蛋白，MICU1缺失诱发Ca2+超载。申请人发现，MI/R并未影响心肌总的MICU1表达，却抑制了线粒体中MICU1含量，提示MI/R减少MICU1线粒体转运。前体蛋白进入线粒体需经Tom系统转运，Tom70是该复合物受体之一。申请人还发现，MI/R降低线粒体中Tom70表达，而Tom70缺失能够减少线粒体中MICU1含量。免疫共沉淀表明，Tom70能够结合MICU1。我们推测，MI/R抑制线粒体Tom70正常表达，干扰MICU1线粒体转运并抑制其功能，导致线粒体Ca2+超载，最终诱发心肌损伤。本项目以MI/R模型为平台，以基因技术为手段，通过整体、细胞与分子三层次研究阐明Tom70/MICU1在MI/R中作用，以期为冠心病防治提供新思路。

心肌缺血/再灌注（MI/R）与冠心病愈后紧密相关。研究发现，Ca2+超载是再灌时线粒体损伤与细胞死亡重要原因。最新研究表明，MICU1是一种线粒体Ca2+稳态调节蛋白，MICU1缺失诱发Ca2+超载。前体蛋白进入线粒体需经Tom系统转运，Tom70是该复合物受体之一。但是，MICU1和Tom70在MI/R中的作用及具体机制尚不清楚。围绕上述科学问题，本项目研究内容如下：一、MICU1在MI/R中的具体作用；二、Tom70在MI/R中的具体作用；三、Tom70与MICU1的调节关系及其对MI/R中的影响。本项目通过构建MI/R模型，运用基因干扰技术，从整体、细胞与分子三层次深入研究了Tom70/MICU1在MI/R中的具体作用。研究发现，MI/R并未影响心肌总的MICU1表达，却抑制了线粒体中MICU1含量。MI/R减少线粒体中Tom70表达，而Tom70缺失能够减少线粒体中MICU1含量。免疫共沉淀表明，Tom70能够结合MICU1。抑制Tom70或MICU1会加重线粒体Ca2+超载，进而加重MI/R损伤。基于上述结果可知，MI/R抑制线粒体Tom70正常表达，干扰MICU1线粒体转运并抑制其功能，导致线粒体Ca2+超载，最终诱发心肌损伤。本项目的开展为冠心病防治提供了新的理论依据，有利于合理指导临床治疗。