Marambio Paola, Toro Barbra, Sanhueza Carlos, Troncoso Rodrigo, Parra Valentina, Verdejo Hugo, García Lorena, Quiroga Clara, Munafo Daniela, Díaz-Elizondo Jessica, Bravo Roberto, González María-Julieta, Diaz-Araya Guilermo, Pedrozo Zully, Chiong Mario, Colombo María Isabel, Lavandero Sergio
Centro FONDAP Estudios Moleculares de la Celula, Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Santiago 838-0492, Chile.
Biochim Biophys Acta. 2010 Jun;1802(6):509-18. doi: 10.1016/j.bbadis.2010.02.002. Epub 2010 Feb 20.
Aggresomes are dynamic structures formed when the ubiquitin-proteasome system is overwhelmed with aggregation-prone proteins. In this process, small protein aggregates are actively transported towards the microtubule-organizing center. A functional role for autophagy in the clearance of aggresomes has also been proposed. In the present work we investigated the molecular mechanisms involved on aggresome formation in cultured rat cardiac myocytes exposed to glucose deprivation. Confocal microscopy showed that small aggregates of polyubiquitinated proteins were formed in cells exposed to glucose deprivation for 6 h. However, at longer times (18 h), aggregates formed large perinuclear inclusions (aggresomes) which colocalized with gamma-tubulin (a microtubule-organizing center marker) and Hsp70. The microtubule disrupting agent vinblastine prevented the formation of these inclusions. Both small aggregates and aggresomes colocalized with autophagy markers such as GFP-LC3 and Rab24. Glucose deprivation stimulates reactive oxygen species (ROS) production and decreases intracellular glutathione levels. ROS inhibition by N-acetylcysteine or by the adenoviral overexpression of catalase or superoxide dismutase disrupted aggresome formation and autophagy induced by glucose deprivation. In conclusion, glucose deprivation induces oxidative stress which is associated with aggresome formation and activation of autophagy in cultured cardiac myocytes.
当泛素-蛋白酶体系统被易于聚集的蛋白质淹没时，会形成应激颗粒，这是一种动态结构。在这个过程中，小的蛋白质聚集体会被主动运输到微管组织中心。也有人提出自噬在清除应激颗粒中具有功能性作用。在本研究中，我们调查了培养的大鼠心肌细胞在葡萄糖剥夺条件下形成应激颗粒所涉及的分子机制。共聚焦显微镜显示，在葡萄糖剥夺6小时的细胞中形成了多泛素化蛋白质的小聚集体。然而，在更长时间（18小时）时，聚集体形成了大的核周包涵体（应激颗粒），这些包涵体与γ-微管蛋白（一种微管组织中心标记物）和热休克蛋白70共定位。微管破坏剂长春花碱可阻止这些包涵体的形成。小聚集体和应激颗粒都与自噬标记物如绿色荧光蛋白-微管相关蛋白1轻链3和Rab24共定位。葡萄糖剥夺会刺激活性氧（ROS）的产生并降低细胞内谷胱甘肽水平。用N-乙酰半胱氨酸或通过腺病毒过表达过氧化氢酶或超氧化物歧化酶抑制ROS，会破坏葡萄糖剥夺诱导的应激颗粒形成和自噬。总之，葡萄糖剥夺会诱导氧化应激，这与培养的心肌细胞中应激颗粒的形成和自噬的激活有关。
