Quantitative metabolic flux analysis reveals an unconventional pathway of fatty acid synthesis in cancer cells deficient for the mitochondrial citrate transport protein.
Quantitative metabolic flux analysis reveals an unconventional pathway of fatty acid synthesis in cancer cells deficient for the mitochondrial citrate transport protein.
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DOI：
10.1016/j.ymben.2016.11.004
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发表时间：
2017-09
影响因子：
8.4
通讯作者：
DeBerardinis RJ
中科院分区：
文献类型：
--
作者：
Jiang L;Boufersaoui A;Yang C;Ko B;Rakheja D;Guevara G;Hu Z;DeBerardinis RJ
由SLC 25 A1编码的线粒体柠檬酸盐转运蛋白（CTP）可调节线粒体和细胞质之间柠檬酸盐的双向运输，支持脂质生物合成和氧化还原稳态。遗传性CTP缺乏导致与L-和D-2-羟基谷氨酸积累相关的致命性神经发育综合征，CTP表达升高与几种类型癌症的预后不良相关，强调了这种转运蛋白在多种人类病理学中的重要性。在这里，我们描述了CTP缺陷在癌细胞中的代谢后果。如从CTP缺陷型人类的表型所预期的，癌细胞中的体细胞CTP损失诱导线粒体代谢的广泛失调，导致乳酸盐和2-羟基戊二酸（2 HG）的L-和D-对映异构体的积累以及TCA循环中间体的消耗。它还消除了线粒体从胞质中输入柠檬酸盐。为了量化CTP缺乏对代谢通量的影响，将细胞与一组13 C-葡萄糖和13 C-谷氨酰胺示踪剂一起培养，所得数据通过代谢通量分析（MFA）整合。CTP缺陷的细胞显示了一个主要的重组中心碳代谢，包括抑制丙酮酸脱氢酶（PDH）和诱导葡萄糖依赖性回补通过丙酮酸羧化酶（PC）。我们还观察到一种不寻常的脂肪生成途径，其中来自葡萄糖的碳供应α-酮戊二酸（AKG）的线粒体生产，然后将其运输到胞质溶胶并用于通过异柠檬酸脱氢酶1（IDH 1）提供还原性羧化。所得到的柠檬酸盐被裂解以产生脂肪生成乙酰辅酶A，从而完成葡萄糖依赖性还原羧化的新途径。在CTP缺陷细胞中，IDH 1抑制抑制来自葡萄糖或谷氨酰胺的脂肪生成，暗示IDH 1是CTP缺陷状态下脂肪酸合成的必需组分。
The mitochondrial citrate transport protein (CTP), encoded by SLC25A1, accommodates bidirectional trafficking of citrate between the mitochondria and cytosol, supporting lipid biosynthesis and redox homeostasis. Genetic CTP deficiency causes a fatal neurodevelopmental syndrome associated with the accumulation of L- and D-2-hydroxyglutaric acid, and elevated CTP expression is associated with poor prognosis in several types of cancer, emphasizing the importance of this transporter in multiple human pathologies. Here we describe the metabolic consequences of CTP deficiency in cancer cells. As expected from the phenotype of CTP-deficient humans, somatic CTP loss in cancer cells induces broad dysregulation of mitochondrial metabolism, resulting in accumulation of lactate and of the L- and D- enantiomers of 2-hydroxyglutarate (2HG) and depletion of TCA cycle intermediates. It also eliminates mitochondrial import of citrate from the cytosol. To quantify the impact of CTP deficiency on metabolic flux, cells were cultured with a set of 13C-glucose and 13C-glutamine tracers with resulting data integrated by metabolic flux analysis (MFA). CTP-deficient cells displayed a major restructuring of central carbon metabolism, including suppression of pyruvate dehydrogenase (PDH) and induction of glucose-dependent anaplerosis through pyruvate carboxylase (PC). We also observed an unusual lipogenic pathway in which carbon from glucose supplies mitochondrial production of alpha-ketoglutarate (AKG), which is then trafficked to the cytosol and used to supply reductive carboxylation by isocitrate dehydrogenase 1 (IDH1). The resulting citrate is cleaved to produce lipogenic acetyl-CoA, thereby completing a novel pathway of glucose-dependent reductive carboxylation. In CTP deficient cells, IDH1 inhibition suppresses lipogenesis from either glucose or glutamine, implicating IDH1 as a required component of fatty acid synthesis in states of CTP deficiency.