Early and Late Events Induced by PolyQ-expanded Proteins IDENTIFICATION OF A COMMON PATHOGENIC PROPERTY OF POLYQ-EXPANDED PROTEINS
Early and Late Events Induced by PolyQ-expanded Proteins IDENTIFICATION OF A COMMON PATHOGENIC PROPERTY OF POLYQ-EXPANDED PROTEINS
复制标题
DOI：
10.1074/jbc.m110.156521
复制
发表时间：
2011-02-01
影响因子：
4.8
通讯作者：
Avvedimento, Vittorio Enrico
中科院分区：
文献类型：
--
作者：
Bertoni, Alessandra;Giuliano, Paola;Avvedimento, Vittorio Enrico
为了找到由polyQ扩增蛋白诱导的共同致病性状，我们在PC 12细胞中使用了条件表达系统来调节这些蛋白的表达，并分析其表达的早期和晚期后果。我们发现，3小时的polyQ-扩展的蛋白质的表达刺激细胞活性氧（ROS）水平，并显着降低线粒体电化学梯度。24-36 h后，ROS诱导DNA损伤和检查点激酶ATM的激活。DNA损伤特征是可逆的，并且只要polyQ扩增的蛋白质被表达就持续存在。神经和应激反应基因的转录在这些细胞中下调。选择性抑制ATM或组蛋白去乙酰化酶可以挽救转录并恢复沉默基因的表达。最终，1周后，polyQ-扩展蛋白的表达也诱导内质网应激。至于负责ROS产生的主要机制，我们发现polyQ-扩展的蛋白质，包括天然的Ataxin-2和亨廷顿蛋白，被选择性地隔离在脂筏膜隔室中，并与膜NADPH氧化酶亚基gp 91相互作用。NADPH氧化酶的选择性抑制或H-Ras信号转导的沉默溶解聚集体并消除DNA损伤。我们认为，靶向的polyQ-扩展的蛋白质的脂筏激活居民NADPH氧化酶。这触发了连接H-Ras，ROS和ERK 1/2的信号，该信号维持并将ROS波传播到细胞核。这种机制可能代表了所有polyQ扩增蛋白的共同致病特征，与天然野生型蛋白的特定背景或功能无关。
To find a common pathogenetic trait induced by polyQ-expanded proteins, we have used a conditional expression system in PC12 cells to tune the expression of these proteins and analyze the early and late consequences of their expression. We find that expression for 3 h of a polyQ-expanded protein stimulates cellular reactive oxygen species (ROS) levels and significantly reduces the mitochondrial electrochemical gradient. 24-36 h later, ROS induce DNA damage and activation of the checkpoint kinase, ATM. DNA damage signatures are reversible and persist as long as polyQ-expanded proteins are expressed. Transcription of neural and stress response genes is down-regulated in these cells. Selective inhibition of ATM or histone deacetylase rescues transcription and restores the expression of silenced genes. Eventually, after 1 week, the expression of polyQ-expanded protein also induces endoplasmic reticulum stress. As to the primary mechanism responsible for ROS generation, we find that polyQ-expanded proteins, including native Ataxin-2 and Huntingtin, are selectively sequestered in the lipid raft membrane compartment and interact with gp91, the membrane NADPH-oxidase subunit. Selective inhibition of NADPH oxidase or silencing of H-Ras signaling dissolves the aggregates and eliminates DNA damage. We suggest that targeting of the polyQ-expanded proteins to the lipid rafts activates the resident NADPH oxidase. This triggers a signal linking H-Ras, ROS, and ERK1/2 that maintains and propagates the ROS wave to the nucleus. This mechanism may represent the common pathogenetic signature of all polyQ-expanded proteins independently of the specific context or the function of the native wild type protein.