端粒酶线粒体转位调控心肌肥厚的分子机制研究

Mitochondria dysfunction pathogenesis is involved in myocardial hypertrophy, and telomerase mitochondria translocation plays a key role in the regulation of mitochondrial function. However, whether or not telomerase mitochondria translocation affects myocardial hypertrophy is unclear. Uncoupling protein 2 (UCP2) is an important regulator for mitochondrial function. Our previous studies found UCP2 knockout led to myocardial hypertrophy, while UCP2 inhibited mammalian target of rapamycin (mTOR) and increased telomerase mitochondria translocation. And we also found the interaction between translocated telomerase reverse transcriptase (TERT) and mitochondrial elongation factor 4 (mtEF4) in mitochondria. Published data showed the myocardial hypertrophy in mtEF4 knockout mice. Therefore, we inferred that the inhibition of mTOR is decreased due to impaired UCP2, and suppressed the telomerase mitochondria translocation and interaction between TERT and mtEF4, and finally causes myocardial hypertrophy. To identify the hypothesis, the angiotensin II (Ang-II) induced myocardial hypertrophy model was performed and UCP2 or TERT knockout mice and primary cardiac myocyte was used to analysis the effect of decreased UCP2 function to mTOR activity, the role of increased mTOR activity in the inhibition of telomerase mitochondria translocation and the mechanism that decreased interaction between mitochondrial telomerase and mtEF4 is involved in mitochondria dysfunction and myocardial hypertrophy. This study provides mechanisms to clarity the pathogenesis of myocardial hypertrophy and theoretical foundation for therapy.

线粒体功能障碍参与了心肌肥厚发生。端粒酶线粒体转位是线粒体功能调节的重要新机制，但其与心肌肥厚关系不明。解偶联蛋白2（UCP2）同样是线粒体功能调节的重要蛋白。我们前期发现，UCP2敲除诱导心肌肥厚发生。UCP2具有抑制哺乳动物雷帕霉素靶蛋白（mTOR）的作用，而mTOR受抑促进端粒酶转位。我们还发现，转位的端粒酶催化亚基TERT与线粒体翻译延伸因子4（mtEF4）在线粒体存在共连接。文献报道mtEF4敲除小鼠表现出心肌肥厚。据此我们推测，UCP2受损使mTOR抑制减弱，端粒酶转位受抑，其与mtEF4的相互作用减弱，致心肌肥厚。本项目拟以血管紧张素Ⅱ诱导的心肌肥厚模型、UCP2及TERT敲除小鼠、原代心肌细胞为研究对象，分析UCP2功能减弱对mTOR活性的影响，明确mTOR对端粒酶线粒体转位的作用及其与mtEF4的相互作用在心肌肥厚发生中的分子机制。为阐明心肌肥厚的发生机制做出有益的尝试。

研究背景：体育运动对病理性心肌肥大有防治作用，但其中的分子机制尚不清楚。端粒酶逆转录酶（TERT）对线粒体功能失调和氧化应激具有保护作用，且运动可上调心肌TERT。本研究拟探讨端粒酶线粒体转位在运动抗心肌肥大中的作用及机制。结果：自主跑步运动上调心肌线粒体TERT，且该上调效应在主动脉弓缩窄（TAC）诱导的心肌肥大病理过程中依然维持。将线粒体定位序列N端与TERT编码序列融合构建线粒体靶向TERT（mito-TERT）过表达AAV9病毒使小鼠心肌过表达线粒体靶向TERT，可显著减轻TAC诱导的心肌肥大功能、病理和分子表型。进一步实验发现，mito-TERT过表达可显著缓解TAC诱导肥大心肌的线粒体功能紊乱并抑制氧化应激。同时，我们还发现mito-TERT过表达主要改善心肌线粒体呼吸链复合物（COX）I活性，且可能与促进抑制抑制素（prohibitin）的泛素化降解介导的COX I的亚基构成改善有关。最后，我们证实TERT激活剂TA-65可显著改善TAC诱导的心肌肥大功能、病理和分子表型，提示线粒体TERT的抗心肌肥大效应可能具有转化潜能。结论：运动上调心肌线粒体TERT，且该上调在心肌肥大病理过程中可维持，进而通过改善线粒体功能和抑制氧化应激发挥抗心肌肥大效应，因此，线粒体TERT可能是心肌肥大防治的新靶点。