LGBC, CNRS UMR8159, Université Versailles-SQY, PRES Universud Paris, 45, avenue des Etats-Unis, 78035 Versailles, France.
Int J Biochem Cell Biol. 2010 May;42(5):623-9. doi: 10.1016/j.biocel.2009.12.024. Epub 2010 Jan 10.
The adenine nucleotide translocator (ANT) is a mitochondrial bi-functional protein, which catalyzes the exchange of ADP and ATP between cytosol and mitochondria and participates in many models of mitochondrial apoptosis. The human adenine nucleotide translocator sub-family is composed of four isoforms, namely ANT1-4, encoded by four nuclear genes, whose expression is highly regulated. Previous studies have revealed that ANT1 and 3 induce mitochondrial apoptosis, whereas ANT2 is anti-apoptotic. However, the role of the recently identified isoform ANT4 in the apoptotic pathway has not yet been elucidated. Here, we investigated the effects of stable heterologous expression of the ANT4 on proliferation, mitochondrial respiration and cell death in human cancer cells, using ANT3 as a control of pro-apoptotic isoform. As expected, ANT3 enhanced mitochondria-mediated apoptosis in response to lonidamine, a mitochondriotoxic chemotherapeutic drug, and staurosporine, a protein kinase inhibitor. Our results also indicate that the pro-apoptotic effect of ANT3 was accompanied by decreased rate of cell proliferation, alteration in the mitochondrial network topology, and decreased reactive oxygen species production. Of note, we demonstrate for the first time that ANT4 enhanced cell growth without impacting mitochondrial network or respiration. Moreover, ANT4 differentially regulated the intracellular levels of hydrogen peroxide without affecting superoxide anion levels. Finally, stable ANT4 overexpression protected cancer cells from lonidamine and staurosporine apoptosis in a manner independent of Bcl-2 expression. These data highlight a hitherto undefined cytoprotective activity of ANT4, and provide a novel dichotomy in the human ANT isoform sub-family with ANT1 and 3 isoforms functioning as pro-apoptotic while ANT2 and 4 isoforms render cells resistant to death inducing stimuli.
腺嘌呤核苷酸转位酶（ANT）是一种线粒体双功能蛋白，可催化细胞质和线粒体之间 ADP 和 ATP 的交换，并参与多种线粒体凋亡模型。人类腺嘌呤核苷酸转位酶亚家族由四个同工型组成，即 ANT1-4，由四个核基因编码，其表达受到高度调控。先前的研究表明，ANT1 和 3 诱导线粒体凋亡，而 ANT2 具有抗凋亡作用。然而，最近发现的同工型 ANT4 在凋亡途径中的作用尚未阐明。在这里，我们使用 ANT3 作为促凋亡同工型的对照，研究了稳定异源表达 ANT4 对人癌细胞增殖、线粒体呼吸和细胞死亡的影响。正如预期的那样，ANT3 增强了 lonidamine（一种线粒体毒性化疗药物）和 staurosporine（一种蛋白激酶抑制剂）诱导的线粒体介导的凋亡。我们的结果还表明，ANT3 的促凋亡作用伴随着细胞增殖率降低、线粒体网络拓扑改变和活性氧产生减少。值得注意的是，我们首次证明 ANT4 增强细胞生长而不影响线粒体网络或呼吸。此外，ANT4 可调节细胞内过氧化氢水平而不影响超氧阴离子水平。最后，稳定过表达 ANT4 可独立于 Bcl-2 表达保护癌细胞免受 lonidamine 和 staurosporine 凋亡。这些数据突出了 ANT4 迄今为止尚未定义的细胞保护活性，并为人类 ANT 同工型亚家族提供了一个新的二分法，即 ANT1 和 3 同工型作为促凋亡，而 ANT2 和 4 同工型使细胞对诱导死亡的刺激具有抗性。
