Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA; MD-PhD Combined Degree Program, University of Texas Medical Branch, Galveston, TX, 77555, USA.
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
Anal Biochem. 2019 Feb 1;566:1-9. doi: 10.1016/j.ab.2018.10.026. Epub 2018 Oct 26.
A major hallmark of cancer is a perturbed metabolism resulting in high demand for various metabolites, glucose being the most well studied. While glucose can be converted into pyruvate for ATP production, the serine synthesis pathway (SSP) can divert glucose to generate serine, glycine, and methionine. In the process, the carbon unit from serine is incorporated into the one-carbon pool which makes methionine and maintains S-adenosylmethionine levels, which are needed to maintain the epigenetic landscape and ultimately controlling what genes are available for transcription. Alternatively, the carbon unit can be used for purine and thymidylate synthesis. We present here an approach to follow the flux through this pathway in cultured human cells using stable isotope enriched glucose and gas chromatography mass spectrometry analysis of serine, glycine, and methionine. We demonstrate that in three different cell lines this pathway contributes only 1-2% of total intracellular methionine. This suggests under high extracellular methionine conditions, the predominance of carbon units from this pathway are used to synthesize nucleic acids.
癌症的一个主要特征是代谢失调，导致对各种代谢物的高需求，葡萄糖是研究得最多的一种。虽然葡萄糖可以转化为丙酮酸来产生 ATP，但丝氨酸合成途径（SSP）可以将葡萄糖转化为丝氨酸、甘氨酸和蛋氨酸。在此过程中，丝氨酸的碳单位被纳入一碳池，用于合成蛋氨酸并维持 S-腺苷甲硫氨酸水平，这对于维持表观遗传景观以及最终控制哪些基因可用于转录是必需的。或者，该碳单元可用于嘌呤和胸苷酸的合成。我们在这里提出了一种使用稳定同位素标记的葡萄糖并通过气相色谱-质谱分析丝氨酸、甘氨酸和蛋氨酸来跟踪培养的人细胞中该途径通量的方法。我们证明，在三种不同的细胞系中，该途径仅贡献总细胞内蛋氨酸的 1-2%。这表明在高细胞外蛋氨酸条件下，该途径的碳单位主要用于合成核酸。
