Respiratory chain supercomplexes set the threshold for respiration defects in human mtDNA mutant cybrids
Respiratory chain supercomplexes set the threshold for respiration defects in human mtDNA mutant cybrids
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DOI：
10.1093/hmg/ddl141
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发表时间：
2006-07-01
影响因子：
3.5
通讯作者：
Manfredi, Giovanni
中科院分区：
文献类型：
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作者：
D'Aurelio, Marilena;Gajewski, Carl D.;Manfredi, Giovanni
线粒体DNA （mtDNA）突变导致人类异质性疾病。MtDNA在每个细胞中存在多个拷贝，突变需要积累超过一个临界阈值才能导致疾病，因为共存的野生型MtDNA可以补充遗传缺陷。更好地了解mtDNA分子间功能互补的分子决定因素可以帮助我们揭示线粒体疾病中mtDNA突变表型表达的调节机制。我们通过融合两种细胞系来研究人类细胞中的mtDNA互补，其中一种细胞系含有呼吸链复合体IV （COX I）亚基的同质突变，另一种细胞系III（细胞色素b）亚基的明显同质突变。细胞融合后，杂交细胞中的呼吸恢复，表明线粒体融合并交换遗传和蛋白质物质。线粒体功能性互补频繁发生，但效率不一。我们用天然凝胶电泳研究了互补杂交细胞中线粒体呼吸链的分子结构。我们发现，线粒体呼吸的恢复与含有复合体I、III和IV的超分子结构（超复合体）的存在相关。我们认为，为了形成超复合体并提供线粒体功能互补，需要临界量的复合体III或IV。根据这些发现，超复合体组装是呼吸的必要步骤，其缺陷设置了mtDNA突变细胞呼吸损伤的阈值。
Mitochondrial DNA (mtDNA) mutations cause heterogeneous disorders in humans. MtDNA exists in multiple copies per cell, and mutations need to accumulate beyond a critical threshold to cause disease, because coexisting wild-type mtDNA can complement the genetic defect. A better understanding of the molecular determinants of functional complementation among mtDNA molecules could help us shedding some light on the mechanisms modulating the phenotypic expression of mtDNA mutations in mitochondrial diseases. We studied mtDNA complementation in human cells by fusing two cell lines, one containing a homoplasmic mutation in a subunit of respiratory chain complex IV, COX I, and the other a distinct homoplasmic mutation in a subunit of complex III, cytochrome b. Upon cell fusion, respiration is recovered in hybrids cells, indicating that mitochondria fuse and exchange genetic and protein materials. Mitochondrial functional complementation occurs frequently, but with variable efficiency. We have investigated by native gel electrophoresis the molecular organization of the mitochondrial respiratory chain in complementing hybrid cells. We show that the recovery of mitochondrial respiration correlates with the presence of supramolecular structures (supercomplexes) containing complexes I, III and IV. We suggest that critical amounts of complexes III or IV are required in order for supercomplexes to form and provide mitochondrial functional complementation. From these findings, supercomplex assembly emerges as a necessary step for respiration, and its defect sets the threshold for respiratory impairment in mtDNA mutant cells.