Inactivation of the mitochondrial protease Afg3l2 results in severely diminished respiratory chain activity and widespread defects in mitochondrial gene expression.
Inactivation of the mitochondrial protease Afg3l2 results in severely diminished respiratory chain activity and widespread defects in mitochondrial gene expression.
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DOI：
10.1371/journal.pgen.1009118
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发表时间：
2020-10
期刊：
影响因子：
4.5
通讯作者：
Pallanck LJ
中科院分区：
文献类型：
--
作者：
Pareek G;Pallanck LJ
M-AAA蛋白水解酶在线粒体膜蛋白的蛋白稳定中起着至关重要的作用，而这些蛋白水解酶基因的突变会导致严重的无法治愈的神经系统疾病。为了进一步探讨m-AAA蛋白水解酶的生物学作用及其缺失的病理后果，我们利用遗传方法在果蝇黑腹果蝇中失活了编码m-AAA蛋白水解酶关键组成部分的ATPase家族基因3-like 2(AFG3L2)基因。我们发现果蝇AFG3L2的零等位基因在发育早期死亡，但使用RNAi部分灭活AFG3L2允许存活到发育的后期和成虫阶段。AFG3L2部分失活的果蝇表现出行为缺陷、神经变性、未折叠线粒体蛋白的积累和呼吸链(RC)活性降低。进一步的研究表明，RC活性的降低主要是线粒体转录和翻译严重减弱的结果。这些缺陷伴随着线粒体未折叠蛋白反应(mito-UPR)的激活和自噬。MITO-UPR组分的过表达部分挽救了AFG3L2缺陷的表型，表明蛋白质聚集是AFG3L2缺陷动物缺陷的部分原因。我们的工作表明，旨在激活线粒体应激途径和线粒体基因表达的策略可能对AFG3L2突变引起的疾病具有治疗作用。线粒体通过呼吸链(RC)复合体的作用产生几乎所有的细胞能量。然而，线粒体也对真核细胞的质量控制提出了挑战。特别是，RC复合体的生物发生依赖于核和线粒体编码亚基的协调表达，这一过程中的不平衡可能导致蛋白质聚集。此外，RC络合物作为其活性的副产品，会产生极具破坏性的活性氧物种。线粒体AAA+家族的蛋白被认为是抵御这些侮辱的第一道防线。蛋白水解酶家族的重要性最好的例证是由它们各自的基因突变引起的严重的神经退行性疾病。为了更好地了解AAA+酶的生物学作用，以及它们失活的生理后果，我们在果蝇中使用了一种遗传学方法来研究Afg3l2 AAA+酶。AFG3L2基因的部分失活导致线粒体功能缺陷、寿命缩短和神经变性。出乎意料的是，我们发现线粒体基因表达严重减弱，包括转录和翻译，这是这些表型的主要原因。基因表达的缺陷似乎是由于线粒体核糖体成熟和组装失败，以及可能是调节因子被隔离到不活跃的聚集体中所致。我们的工作表明，Afg3l2在降解未折叠的线粒体蛋白和调节线粒体基因表达方面发挥着关键作用，解决这些问题的策略可能对AFG3L2基因突变引起的疾病具有治疗作用。
The m-AAA proteases play a critical role in the proteostasis of inner mitochondrial membrane proteins, and mutations in the genes encoding these proteases cause severe incurable neurological diseases. To further explore the biological role of the m-AAA proteases and the pathological consequences of their deficiency, we used a genetic approach in the fruit fly Drosophila melanogaster to inactivate the ATPase family gene 3-like 2 (AFG3L2) gene, which encodes a critical component of the m-AAA proteases. We found that null alleles of Drosophila AFG3L2 die early in development, but partial inactivation of AFG3L2 using RNAi allowed survival to the late pupal and adult stages of development. Flies with partial inactivation of AFG3L2 exhibited behavioral defects, neurodegeneration, accumulation of unfolded mitochondrial proteins, and diminished respiratory chain (RC) activity. Further work revealed that the reduced RC activity was primarily a consequence of severely diminished mitochondrial transcription and translation. These defects were accompanied by activation of the mitochondrial unfolded protein response (mito-UPR) and autophagy. Overexpression of mito-UPR components partially rescued the AFG3L2-deficient phenotypes, indicating that protein aggregation partly accounts for the defects of AFG3L2-deficient animals. Our work suggests that strategies designed to activate mitochondrial stress pathways and mitochondrial gene expression could be therapeutic in the diseases caused by mutations in AFG3L2. Mitochondria produce virtually all of the cellular energy through the actions of the respiratory chain (RC) complexes. However, mitochondria also present a quality control challenge for the eukaryotic cell. In particular, biogenesis of the RC complexes depends on the coordinated expression of nuclear and mitochondrially encoded subunits and an imbalance in this process can cause protein aggregation. Moreover, the RC complexes produce highly damaging reactive oxygen species as a side product of their activity. The Mitochondrial AAA+ family of proteases are believed to provide the first line of defense against these insults. The importance of this protease family is best exemplified by the severe neurodegenerative diseases that are caused by mutations in their respective genes. To better understand the biological roles of the AAA+ proteases, and the physiological consequences of their inactivation we used a genetic approach in Drosophila to study the Afg3l2 AAA+ protease. Partial inactivation of the AFG3L2 gene resulted in mitochondrial functional deficits, shortened lifespan, and neurodegeneration. Unexpectedly, we found that severely diminished mitochondrial gene expression, including transcription, and translation, primarily accounts for these phenotypes. The defects in gene expression appear to be caused by a failure in mitochondrial ribosome maturation and assembly, and possibly, sequestration of regulatory factors into inactive aggregates. Our work indicates Afg3l2 plays critical roles in degrading unfolded mitochondrial proteins and regulating mitochondrial gene expression, and that strategies to address these matters could be therapeutic in the diseases caused by mutations in the AFG3L2 gene.
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影响因子：
12.8
作者：
Lee, Wan;Choi, Hyo-Im;Park, Seung-Yoon
通讯作者：
Park, Seung-Yoon
影响因子：
4.5
作者：
Bratic, Ana;Wredenberg, Anna;Larsson, Nils-Goeran
通讯作者：
Larsson, Nils-Goeran
影响因子：
5.3
作者：
Maltecca, Francesca;Magnoni, Raffaella;Casari, Giorgio
通讯作者：
Casari, Giorgio
内膜的四十千克蛋白是线粒体钙Uniporter。
影响因子：
64.8
作者：
De Stefani, Diego;Raffaello, Anna;Teardo, Enrico;Szabo, Ildiko;Rizzuto, Rosario
通讯作者：
Rizzuto, Rosario
影响因子：
5.3
作者：
Koppen, Mirko;Metodiev, Metodi D.;Langer, Thomas
通讯作者：
Langer, Thomas