Reductive carboxylation supports redox homeostasis during anchorage-independent growth.
Reductive carboxylation supports redox homeostasis during anchorage-independent growth.
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DOI：
10.1038/nature17393
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发表时间：
2016-04-14
期刊：
影响因子：
64.8
通讯作者：
DeBerardinis RJ
中科院分区：
文献类型：
--
作者：
Jiang L;Shestov AA;Swain P;Yang C;Parker SJ;Wang QA;Terada LS;Adams ND;McCabe MT;Pietrak B;Schmidt S;Metallo CM;Dranka BP;Schwartz B;DeBerardinis RJ
上皮细胞通过附着到细胞外基质(ECM)来接受生长和生存刺激。克服对ECM诱导信号的上瘾是大多数恶性细胞的特性--锚定非依赖性生长所必需的。细胞外基质脱离与葡萄糖代谢改变引起的活性氧簇(ROS)增加有关。在这里，我们确定了一条非传统的途径，在适应锚地独立的过程中支持氧化还原平衡和生长。我们观察到，脱离单层培养和生长为不依赖于锚定的肿瘤球体伴随着葡萄糖和谷氨酰胺代谢的变化。具体地说，这两种营养物质的氧化在球体中被抑制，而谷氨酰胺还原生成柠檬酸盐被促进。还原型谷氨酰胺代谢高度依赖胞浆异柠檬酸脱氢酶-1(IDH1)，因为在IDH1纯合子缺失或用IDH1抑制剂处理的细胞中，该活性被抑制。这种活动是在没有缺氧的情况下发生的，缺氧是众所周知的还原代谢的诱因。相反，IDH1减轻了球体中线粒体的ROS，抑制IDH1通过一种需要线粒体ROS的机制减少了球体的生长。同位素示踪表明，在球体中，胞浆中还原产生的异柠檬酸/柠檬酸可以进入线粒体并参与氧化代谢，包括IDH2的氧化。这会在线粒体中产生NADPH，使细胞能够减轻线粒体的ROS，并最大限度地促进生长。IDH1和IDH2都不是单层生长所必需的，但缺失其中任何一个都会增强线粒体ROS并缩小球体大小，线粒体柠檬酸转运蛋白的缺失也是如此。综上所述，这些数据表明，适应锚定独立性需要从根本上改变柠檬酸代谢，这种改变由IDH1依赖的还原羧化启动，最终抑制线粒体ROS。
Epithelial cells receive growth and survival stimuli through their attachment to an extracellular matrix (ECM). Overcoming the addiction to ECM-induced signals is required for anchorage-independent growth, a property of most malignant cells. Detachment from ECM is associated with enhanced reactive oxygen species (ROS) due to altered glucose metabolism. Here we identify an unconventional pathway that supports redox homeostasis and growth during adaptation to anchorage independence. We observed that detachment from monolayer culture and growth as anchorage-independent tumor spheroids was accompanied by changes in both glucose and glutamine metabolism. Specifically, oxidation of both nutrients was suppressed in spheroids, whereas reductive formation of citrate from glutamine was enhanced. Reductive glutamine metabolism was highly dependent on cytosolic isocitrate dehydrogenase-1 (IDH1), because the activity was suppressed in cells homozygous null for IDH1 or treated with an IDH1 inhibitor. This activity occurred in absence of hypoxia, a well-known inducer of reductive metabolism. Rather, IDH1 mitigated mitochondrial ROS in spheroids, and suppressing IDH1 reduced spheroid growth through a mechanism requiring mitochondrial ROS. Isotope tracing revealed that in spheroids, isocitrate/citrate produced reductively in the cytosol could enter the mitochondria and participate in oxidative metabolism, including oxidation by IDH2. This generates NADPH in the mitochondria, enabling cells to mitigate mitochondrial ROS and maximize growth. Neither IDH1 nor IDH2 was necessary for monolayer growth, but deleting either one enhanced mitochondrial ROS and reduced spheroid size, as did deletion of the mitochondrial citrate transporter protein. Together, the data indicate that adaptation to anchorage independence requires a fundamental change in citrate metabolism, initiated by IDH1-dependent reductive carboxylation and culminating in suppression of mitochondrial ROS.