Quantitative determinants of aerobic glycolysis identify flux through the enzyme GAPDH as a limiting step.
Quantitative determinants of aerobic glycolysis identify flux through the enzyme GAPDH as a limiting step.
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DOI：
10.7554/elife.03342
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发表时间：
2014-07-09
期刊：
影响因子：
7.7
通讯作者：
Locasale JW
中科院分区：
文献类型：
--
作者：
Shestov AA;Liu X;Ser Z;Cluntun AA;Hung YP;Huang L;Kim D;Le A;Yellen G;Albeck JG;Locasale JW
有氧糖酵解或瓦尔堡效应（WE）的特征在于葡萄糖代谢为乳酸的增加。对于这种表型，代谢活性的什么样的定量变化是必要的和足够的，这仍然是未知的。我们开发了糖酵解的计算模型，并使用代谢控制分析（MCA），代谢组学数据和统计模拟进行了综合分析。我们确定并证实了一种新的有氧糖酵解特异性调节模式，其中通过GAPDH（分离上下糖酵解的酶）的通量是途径中的限速步骤，果糖（1，6）二磷酸（FBP）的水平可预测糖酵解的速率和控制点。引人注目的是，发现并证实了负通量控制的几个步骤被认为是糖酵解的限速。总之，这些发现列举了WE的生化决定因素，并提出了确定靶向糖酵解的药物可能最有效的背景的策略。http://dx.doi.org/10.7554/eLife.03342.001细胞通过糖酵解从一种叫做葡萄糖的糖中产生能量。这个过程涉及许多催化10种不同化学反应的酶，它基本上是将葡萄糖逐步转化为一种更简单的化学物质，称为丙酮酸。然后丙酮酸通常被运输到细胞内称为线粒体的结构中，在那里它被氧气进一步分解以释放更多能量。然而，在快速分裂的细胞中，丙酮酸被转化为另一种叫做乳酸的化学物质，乳酸释放能量的速度更快，但总的来说释放的能量更少。癌细胞通常将其大部分葡萄糖转化为乳酸，而不是在线粒体中分解丙酮酸：这一观察结果被称为“瓦尔堡效应”。虽然有许多因素影响细胞如何从丙酮酸释放能量，但仍不清楚是什么调节这些生化过程中哪一个在活细胞中最常见。在这项研究中，Shestov等人开发了一个糖酵解过程的计算模型，并使用该模型研究了瓦尔堡效应的原因。该模型基于酶的已知特性和每个步骤中涉及的化学反应。它预测，在糖酵解中进行第六步的GAPDH酶的活性在许多情况下会影响乳酸的产生量。这表明这种酶代表了途径中的瓶颈。接下来，Shestov等人进行了实验，他们使用药物阻断糖酵解途径的不同阶段，并证实GAPDH酶对调节活癌细胞中的这一途径也很重要。在这些处理过的细胞中，一种叫做果糖-1，6-二磷酸的化学物质（在葡萄糖和丙酮酸之间的途径中的一个步骤中产生）的水平要么非常高，要么非常低。Shestov等人提出，当途径中GAPDH上游的酶使用的化学物质（包括果糖-1，6-二磷酸）丰富时，通过糖酵解途径的化学物质流由GAPDH酶控制。然而，如果这些化学物质是有限的，其他参与途径早期步骤的酶会调节这一过程。Shestov等人的发现揭示了糖酵解的调节比以前认为的更复杂，并且当细胞经历瓦尔堡效应时也非常不同。在未来，这些发现可能有助于确定可以使用靶向糖酵解过程的药物有效治疗的癌症类型，这些药物目前正在临床前研究中进行测试。DOI：http://dx.doi.org/10.7554/eLife.03342.002网站
Aerobic glycolysis or the Warburg Effect (WE) is characterized by the increased metabolism of glucose to lactate. It remains unknown what quantitative changes to the activity of metabolism are necessary and sufficient for this phenotype. We developed a computational model of glycolysis and an integrated analysis using metabolic control analysis (MCA), metabolomics data, and statistical simulations. We identified and confirmed a novel mode of regulation specific to aerobic glycolysis where flux through GAPDH, the enzyme separating lower and upper glycolysis, is the rate-limiting step in the pathway and the levels of fructose (1,6) bisphosphate (FBP), are predictive of the rate and control points in glycolysis. Strikingly, negative flux control was found and confirmed for several steps thought to be rate-limiting in glycolysis. Together, these findings enumerate the biochemical determinants of the WE and suggest strategies for identifying the contexts in which agents that target glycolysis might be most effective. DOI: http://dx.doi.org/10.7554/eLife.03342.001 Cells generate energy from a sugar called glucose via a process called glycolysis. This process involves many enzymes that catalyze 10 different chemical reactions, and it essentially converts glucose step-by-step into a simpler chemical called pyruvate. Pyruvate is then normally transported into structures within the cell called mitochondria, where it is further broken down using oxygen to release more energy. However, in cells that are rapidly dividing, pyruvate is converted into another chemical called lactate—which releases energy more quickly, but releases less energy overall. Cancer cells often convert most of their glucose into lactate, rather than breaking down pyruvate in their mitochondria: an observation known as the ‘Warburg effect’. And while many factors affect how a cell releases energy from pyruvate, it remains unclear what regulates which of these biochemical processes is most common in a living cell. In this study, Shestov et al. have developed a computational model for the process of glycolysis and used this to investigate the causes of the Warburg Effect. The model was based on the known characteristics of the enzymes and chemical reactions involved at each step. It predicted that the activity of the enzyme called GAPDH, which carries out the sixth step in glycolysis, in many cases affects how much lactate is produced. This suggests that this enzyme represents a bottleneck in the pathway. Next, Shestov et al. performed experiments where they used drugs to block different stages of the glycolysis pathway, and confirmed that the GAPDH enzyme is important for regulating this pathway in living cancer cells too. In these treated cells, the levels of a chemical called fructose-1,6-biphosphate (which is made in a step in the pathway between glucose and pyruvate) were either very high or very low. Shestov et al. proposed that the flow of chemicals through the glycolysis pathway is controlled by the GAPDH enzyme when the chemicals used by the enzymes upstream of GAPDH in the pathway (which includes fructose-1,6-biphosphate) are plentiful. However, if these chemicals are limited, other enzymes that are involved in earlier steps of the pathway regulate the process instead. The findings of Shestov et al. reveal that the regulation of glycolysis is more complex than previously thought, and is also very different when cells are undergoing the Warburg Effect. In the future, these findings might help to identify the types of cancer that could be effectively treated using drugs that target the glycolysis process, which are currently being tested in pre-clinical studies. DOI: http://dx.doi.org/10.7554/eLife.03342.002