PDF(Pubmed)
Abstract：
Metabolic rewiring during the proliferation-to-quiescence transition is poorly understood. Here, using a model of contact inhibition-induced quiescence, we conducted 13C-metabolic flux analysis in proliferating (P) and quiescent (Q) mouse embryonic fibroblasts (MEFs) to investigate this process. Q cells exhibit reduced glycolysis but increased TCA cycle flux and mitochondrial respiration. Reduced glycolytic flux in Q cells correlates with reduced glycolytic enzyme expression mediated by yes-associated protein (YAP) inhibition. The increased TCA cycle activity and respiration in Q cells is mediated by induced mitochondrial pyruvate carrier (MPC) expression, rendering them vulnerable to MPC inhibition. The malate-to-pyruvate flux, which generates NADPH, is markedly reduced by modulating malic enzyme 1 (ME1) dimerization in Q cells. Conversely, the malate dehydrogenase 1 (MDH1)-mediated oxaloacetate-to-malate flux is reversed and elevated in Q cells, driven by high mitochondrial-derived malate levels, reduced cytosolic oxaloacetate, elevated MDH1 levels, and a high cytoplasmic NAD+/NADH ratio. Transcriptomic analysis revealed large number of genes are induced in Q cells, many of which are associated with the extracellular matrix (ECM), while YAP-dependent and cell cycle-related genes are repressed. The results suggest that high TCA cycle flux and respiration in Q cells are required to generate ATP and amino acids to maintain de-novo ECM protein synthesis and secretion.
摘要：
对增殖到静止过渡期间的代谢重新布线知之甚少。这里,使用接触抑制诱导的静止模型，我们在增殖（P）和静止（Q）小鼠胚胎成纤维细胞（MEFs）中进行了13C代谢通量分析，以研究这一过程。Q细胞表现出减少的糖酵解但增加的TCA循环通量和线粒体呼吸。Q细胞中糖酵解通量降低与由Yes相关蛋白（YAP）抑制介导的糖酵解酶表达降低相关。Q细胞中TCA循环活性和呼吸的增加是通过诱导线粒体丙酮酸载体(MPC)的表达来介导的,使它们容易受到MPC抑制。苹果酸到丙酮酸的通量，产生NADPH，通过调节Q细胞中的苹果酸酶1（ME1）二聚化而显着降低。相反，苹果酸脱氢酶1（MDH1）介导的草酰乙酸至苹果酸的通量在Q细胞中逆转并升高，由线粒体衍生的苹果酸水平高驱动，减少的细胞溶质草酰乙酸，MDH1水平升高，和高的细胞质NAD+/NADH比率。转录组学分析显示，在Q细胞中诱导了大量基因，其中许多与细胞外基质（ECM）有关，而YAP依赖性和细胞周期相关基因被抑制。结果表明，Q细胞中的高TCA循环通量和呼吸是产生ATP和氨基酸以维持从头ECM蛋白合成和分泌所必需的。
