Kulawiec Mariola, Arnouk Hilal, Desouki Mohamed Mokhtar, Kazim Latif, Still Ivan, Singh Keshav K
Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York, USA.
Cancer Biol Ther. 2006 Aug;5(8):967-75. doi: 10.4161/cbt.5.8.2880. Epub 2006 Aug 2.
All tumors examined to date contain mutations in mitochondrial DNA (mtDNA). In addition, depletion of mtDNA is reported in a variety of tumors. Mitochondrial dysfunction resulting from changes in mtDNA invokes mitochondria-to-nucleus retrograde response in human cells. To identify proteins involved in retrograde response and their potential role in tumorigenesis, we carried out a comparative proteomic analysis using a cell line in which the mitochondrial genome was completely depleted (rho(0) cells lacking all mtDNA-encoded protein subunits), a cybrid cell line in which mtDNA was restored, and the parental cell line. Our comparative proteomic approach revealed marked changes in the cellular proteome and led us to identify quantitative changes in expression of several proteins. We found that subunits of complex I and complex III, molecular chaperones, and a protein involved in cell cycle control were downregulated and Inosine 5'-monophosphate dehydrogenase type 2 (IMPDH2) involved in nucleotide biosynthesis was upregulated in rho(0) cells. Our findings demonstrate that the expression of proteins is restored to wild type level by transfer of wild type mitochondria to rho(0) cells, suggesting that these proteins play key roles in retrograde response. To determine a potential role for identified retrograde responsive proteins in tumorigenesis, we analyzed the expression of UQCRC1 gene (encoding ubiquinol cytochrome-c reductase core protein I) in breast and ovarian tumors. We found that (1) UQCRC1 was highly expressed in breast (74%) and ovarian tumors (34%) and (2) the expression positively correlated with cytochrome c-oxidase (COXII) encoded by mtDNA. Our study opens an avenue for identification of retrograde proteins as potential tumor suppressors or oncogenes involved in carcinogenesis.
迄今为止，所有检测的肿瘤细胞中线粒体DNA（mtDNA）均存在突变。此外，多种肿瘤中均有mtDNA缺失的报道。mtDNA改变导致的线粒体功能障碍可引发人类细胞中的线粒体到细胞核的逆行反应。为了鉴定参与逆行反应的蛋白质及其在肿瘤发生中的潜在作用，我们使用了一种线粒体基因组完全缺失的细胞系（缺乏所有mtDNA编码蛋白亚基的ρ⁰细胞）、一种恢复了mtDNA的胞质杂种细胞系以及亲代细胞系进行了比较蛋白质组学分析。我们的比较蛋白质组学方法揭示了细胞蛋白质组的显著变化，并使我们鉴定出几种蛋白质表达的定量变化。我们发现，ρ⁰细胞中复合物I和复合物III的亚基、分子伴侣以及一种参与细胞周期调控的蛋白质表达下调，而参与核苷酸生物合成的2型肌苷5'-单磷酸脱氢酶（IMPDH2）表达上调。我们的研究结果表明，通过将野生型线粒体转移到ρ⁰细胞中，蛋白质的表达可恢复到野生型水平，这表明这些蛋白质在逆行反应中起关键作用。为了确定已鉴定的逆行反应相关蛋白在肿瘤发生中的潜在作用，我们分析了乳腺癌和卵巢癌中UQCRC1基因（编码泛醇细胞色素c还原酶核心蛋白I）的表达。我们发现：（1）UQCRC1在乳腺癌（74%）和卵巢癌（34%）中高表达；（2）其表达与mtDNA编码的细胞色素c氧化酶（COXII）呈正相关。我们的研究为鉴定作为参与致癌作用的潜在肿瘤抑制因子或癌基因的逆行蛋白开辟了一条途径。
