The Medical Research Council Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom.
The Medical Research Council Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom
Proc Natl Acad Sci U S A. 2017 Mar 28;114(13):3409-3414. doi: 10.1073/pnas.1702357114. Epub 2017 Mar 13.
The permeability transition in human mitochondria refers to the opening of a nonspecific channel, known as the permeability transition pore (PTP), in the inner membrane. Opening can be triggered by calcium ions, leading to swelling of the organelle, disruption of the inner membrane, and ATP synthesis, followed by cell death. Recent proposals suggest that the pore is associated with the ATP synthase complex and specifically with the ring of c-subunits that constitute the membrane domain of the enzyme's rotor. The c-subunit is produced from three nuclear genes, , , and , encoding identical copies of the mature protein with different mitochondrial-targeting sequences that are removed during their import into the organelle. To investigate the involvement of the c-subunit in the PTP, we generated a clonal cell, HAP1-A12, from near-haploid human cells, in which , , and were disrupted. The HAP1-A12 cells are incapable of producing the c-subunit, but they preserve the characteristic properties of the PTP. Therefore, the c-subunit does not provide the PTP. The mitochondria in HAP1-A12 cells assemble a vestigial ATP synthase, with intact F-catalytic and peripheral stalk domains and the supernumerary subunits e, f, and g, but lacking membrane subunits ATP6 and ATP8. The same vestigial complex plus associated c-subunits was characterized from human 143B ρ cells, which cannot make the subunits ATP6 and ATP8, but retain the PTP. Therefore, none of the membrane subunits of the ATP synthase that are involved directly in transmembrane proton translocation is involved in forming the PTP.
人线粒体的通透性转变是指内膜中一种非特异性通道（称为通透性转变孔道，PTP）的打开。这种打开可以被钙离子触发，导致细胞器肿胀、内膜破裂和 ATP 合成，随后是细胞死亡。最近的提议表明，该孔道与 ATP 合酶复合物有关，特别是与构成酶转子膜域的 c 亚基环有关。c 亚基由三个核基因 、 、 和 产生，它们编码成熟蛋白的相同拷贝，但具有不同的线粒体靶向序列，这些序列在它们被导入细胞器时被去除。为了研究 c 亚基在 PTP 中的参与，我们从近单倍体人细胞中生成了一个克隆细胞 HAP1-A12，其中 、 、 和 被破坏。HAP1-A12 细胞不能产生 c 亚基，但它们保留了 PTP 的特征性质。因此，c 亚基不是 PTP。HAP1-A12 细胞中的线粒体组装了一个残余的 ATP 合酶，具有完整的 F-催化和外周茎结构域以及多余的亚基 e、f 和 g，但缺乏膜亚基 ATP6 和 ATP8。同样的残余复合物加上相关的 c 亚基从不能制造 ATP6 和 ATP8 亚基的人 143B ρ细胞中被表征，但保留了 PTP。因此，直接参与跨膜质子转运的 ATP 合酶的膜亚基都没有参与形成 PTP。
