Mitochondrial protein import clogging as a mechanism of disease.
Mitochondrial protein import clogging as a mechanism of disease.
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DOI：
10.7554/elife.84330
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发表时间：
2023-05-02
期刊：
影响因子：
7.7
通讯作者：
Chen XJ
中科院分区：
文献类型：
--
作者：
Coyne LP;Wang X;Song J;de Jong E;Schneider K;Massa PT;Middleton FA;Becker T;Chen XJ
线粒体生物发生需要从胞质溶胶输入> 1，000个线粒体前蛋白。大多数关于线粒体蛋白质输入的研究都集中在核心输入机制上。底物前蛋白的生物物理性质是否以及如何影响总体输入效率尚不清楚。在这里，我们表明，进入线粒体的蛋白质交通可以被破坏的氨基酸取代在一个单一的底物前蛋白。ADP/ATP移位酶1（ANT 1）及其酵母同系物ADP/ATP载体2（Aac 2）中的致病性错义突变导致蛋白质沿蛋白质输入途径沿着积累，从而阻碍一般蛋白质移位到线粒体中。这损害线粒体呼吸、胞质蛋白质稳态和细胞活力，而不依赖于ANT 1的核苷酸转运活性。这些突变协同作用，因为双突变体Aac 2/ANT 1主要在外膜（TOM）复合物的移位酶处引起严重堵塞。这赋予酵母极端的毒性。在小鼠中，一种超级阻塞物ANT 1变体的表达导致神经退行性变和一种年龄依赖性显性肌病，这种肌病与ANT 1诱导的人类疾病表型相似，表明阻塞是疾病的一种机制。更广泛地说，这项工作意味着线粒体载体蛋白存在未表征的氨基酸需求，以避免堵塞和随后的疾病。在我们的细胞内，被称为线粒体的隔间产生生命过程展开所需的化学能。在线粒体中发现的大多数蛋白质是在细胞的另一部分（称为胞质溶胶）中制造的，然后在专业机器的帮助下输入。例如，TOM和TIM 22通道为蛋白质提供了一条穿过两个膜屏障的途径，这两个膜屏障将胞质溶胶与细胞内分隔开。ANT 1是一种在人类线粒体内发现的蛋白质，在那里它充当细胞能量货币的运输系统。编码ANT 1的基因中的特定突变与影响肌肉和大脑的退行性疾病有关。然而，目前还不清楚这些突变如何导致疾病。为了解决这个问题，Coyne等人在编码ANT 1的酵母等同物（称为Aac 2）的基因中重新创建了一些突变。在携带这些突变的酵母细胞中进行的实验表明，Aac 2蛋白在TOM和TIM 22通道中积累，形成了一个“堵塞”，阻止其他必需蛋白到达线粒体。结果，酵母细胞死亡。人类ANT 1蛋白的突变形式也以类似的方式堵塞了人类细胞的TOM和TIM 22通道。进一步的实验集中在基因工程小鼠上，这些小鼠产生了相当于ANT 1的“超级阻塞者”版本。这些动物很快就出现了与ANT 1相关的人类疾病相似的肌肉和神经系统疾病。Coyne等人的研究结果表明，编码ANT 1蛋白的基因中的某些遗传突变通过阻断其他蛋白质向线粒体的转运而引起疾病，而不是直接影响ANT 1在细胞中的核苷酸转运作用。这重新定义了我们对线粒体蛋白相关疾病的理解，可能会改变这些疾病的治疗方法。
Mitochondrial biogenesis requires the import of >1,000 mitochondrial preproteins from the cytosol. Most studies on mitochondrial protein import are focused on the core import machinery. Whether and how the biophysical properties of substrate preproteins affect overall import efficiency is underexplored. Here, we show that protein traffic into mitochondria can be disrupted by amino acid substitutions in a single substrate preprotein. Pathogenic missense mutations in ADP/ATP translocase 1 (ANT1), and its yeast homolog ADP/ATP carrier 2 (Aac2), cause the protein to accumulate along the protein import pathway, thereby obstructing general protein translocation into mitochondria. This impairs mitochondrial respiration, cytosolic proteostasis, and cell viability independent of ANT1’s nucleotide transport activity. The mutations act synergistically, as double mutant Aac2/ANT1 causes severe clogging primarily at the translocase of the outer membrane (TOM) complex. This confers extreme toxicity in yeast. In mice, expression of a super-clogger ANT1 variant led to neurodegeneration and an age-dependent dominant myopathy that phenocopy ANT1-induced human disease, suggesting clogging as a mechanism of disease. More broadly, this work implies the existence of uncharacterized amino acid requirements for mitochondrial carrier proteins to avoid clogging and subsequent disease. Inside our cells, compartments known as mitochondria generate the chemical energy required for life processes to unfold. Most of the proteins found within mitochondria are manufactured in another part of the cell (known as the cytosol) and then imported with the help of specialist machinery. For example, the TOM and TIM22 channels provide a route for the proteins to cross the two membrane barriers that separate the cytosol from the inside of a mitochondrion. ANT1 is a protein that is found inside mitochondria in humans, where it acts as a transport system for the cell’s energy currency. Specific mutations in the gene encoding ANT1 have been linked to degenerative conditions that affect the muscles and the brain. However, it remains unclear how these mutations cause disease. To address this question, Coyne et al. recreated some of the mutations in the gene encoding the yeast equivalent of ANT1 (known as Aac2). Experiments in yeast cells carrying these mutations showed that the Aac2 protein accumulated in the TOM and TIM22 channels, creating a ‘clog’ that prevented other essential proteins from reaching the mitochondria. As a result, the yeast cells died. Mutant forms of the human ANT1 protein also clogged up the TOM and TIM22 channels of human cells in a similar way. Further experiments focused on mice genetically engineered to produce a “super-clogger” version of the mouse equivalent of ANT1. The animals soon developed muscle and neurological conditions similar to those observed in human diseases associated with ANT1. The findings of Coyne et al. suggest that certain genetic mutations in the gene encoding the ANT1 protein cause disease by blocking the transport of other proteins to the mitochondria, rather than by directly affecting ANT1’s nucleotide trnsport role in the cell. This redefines our understanding of diseases associated with mitochondrial proteins, potentially altering how treatments for these conditions are designed.
DOI：
10.1083/jcb.200706195
发表时间：
2007-09-24
期刊：
The Journal of cell biology
影响因子：
--
作者：
Hwang DK;Claypool SM;Leuenberger D;Tienson HL;Koehler CM
通讯作者：
Koehler CM