Reversal of Cytosolic One-Carbon Flux Compensates for Loss of the Mitochondrial Folate Pathway

Ducker, Gregory S.; Chen, Li; Morscher, Raphael J.; Ghergurovich, Jonathan M.; Esposito, Mark; Teng, Xin; Kang, Yibin; Rabinowitz, Joshua D.

doi:10.1016/j.cmet.2016.09.011

Cited by 120 publications

(254 citation statements)

References 31 publications

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“…Similarly, in the Ras-driven lung cancer cell line A549, we obtain αoxPPP = 82±4%. In contrast, in the Ras-driven pancreatic cancer cell line 8988T, where both malic enzyme 1 14 and the folate enzyme MTHFD1 have been implicated as significant cytosolic NADPH producers 15 , and in differentiated 3T3-L1 adipocytes where malic enzyme is a major NADPH producer 16 , αoxPPP < 50%. In immortalized pluripotent stem cells, prior literature has reported > 50% NADPH labeling from 3- 2 H-glucose, suggesting slower exchange between water and NADPH in that cell type 17 .…”

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Chemical Basis for Deuterium Labeling of Fat and NADPH

et al. 2017

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Much understanding of metabolism is based on monitoring chemical reactions in cells with isotope tracers. For this purpose, 13C is well suited due to its stable incorporation into bio-molecules and minimal kinetic isotope effect. For redox reactions, however, deuterium tracing can provide valuable additional information. To date, studies examining NADPH production with deuterated carbon sources have failed to account for roughly half of NADPH’s redox active hydrogen. Here we show that the missing hydrogen is the result of enzyme-catalyzed H-D exchange between water and NADPH. While isolated NADPH does not undergo H-D exchange with water, such exchange is catalyzed by Flavin enzymes and occurs rapidly in cells. Correction for H-D exchange is required for accurate assessment of the biological sources of NADPH’s high energy electrons. Deuterated water (D2O) is frequently used to monitor fat synthesis in vivo, but the chemical pathway of the deuteron into fat remains unclear. We show that D2O labels fatty acids primarily via NADPH. Knowledge of this labeling route enables calculation, without any fitting parameters, of the mass isotope distributions of fatty acids from cells grown in D2O. Thus, knowledge of enzyme-catalyzed H-D exchange between water and NADPH enables chemically accurate interpretation of deuterium tracing studies of redox cofactor and fatty acid metabolism.

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Chemical Basis for Deuterium Labeling of Fat and NADPH

et al. 2017

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“…Methylene-THF reductase converts cytosolic CH 2 -THF into CH 3 -THF. However, in most proliferating cultured cells, the mitochondrial pathway is used (Ducker et al 2016). The one-carbon unit in mitochondrial CH 2 -THF can leave the mitochondrion as formate and enter the cytosolic folate cycle via N 10 -formyl-THF (10-fTHF) synthesis (Figs.…”

Section: Synthesis Of the Universal Methyl Donor Sammentioning

confidence: 99%

Undercover: gene control by metabolites and metabolic enzymes

2016

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To make the appropriate developmental decisions or maintain homeostasis, cells and organisms must coordinate the expression of their genome and metabolic state. However, the molecular mechanisms that relay environmental cues such as nutrient availability to the appropriate gene expression response remain poorly understood. There is a growing awareness that central components of intermediary metabolism are cofactors or cosubstrates of chromatin-modifying enzymes. As such, their concentrations constitute a potential regulatory interface between the metabolic and chromatin states. In addition, there is increasing evidence for a direct involvement of classic metabolic enzymes in gene expression control. These dual-function proteins may provide a direct link between metabolic programing and the control of gene expression. Here, we discuss our current understanding of the molecular mechanisms connecting metabolism to gene expression and their implications for development and disease.Metabolism and gene regulation are two fundamental biological processes that are essential to all living organisms. Homeostasis, cell growth, and differentiation all require the coordination of metabolic state and gene expression programs. Nevertheless, how expression of the genome adapts to metabolic state or environmental changes is not well understood. One level of regulation involves signal transduction pathways that control key transcription factors that act as master regulators of gene expression programs. In addition, post-translational modifications (PTMs) of chromatin play a major role in the activation or repression of gene transcription. These include acetylation, methylation, and phosphorylation of the histones and DNA methylation. Some of these chromatin modifications are involved in the maintenance of stable patterns of gene expression, usually referred to as epigenetic regulation. Pertinently, the activity of enzymes that modulate chromatin is critically dependent on central metabolites as cofactors or cosubstrates. Thus, the availability of metabolites that are required for the activity of histone-modifying enzymes may connect metabolism to chromatin structure and gene expression. Finally, selective metabolic enzymes act in the nucleus to adjust gene transcription in response to changes in metabolic state. Here, we review the interface between metabolism and gene transcription. We focus on the molecular mechanisms involved and discuss unresolved issues and implications for development and disease. The basics of metabolism and gene expression controlMetabolism is the total of all chemical reactions in cells and organisms that maintain life. Metabolism can be divided into two classes: catabolic processes (the breakdown of molecules that usually results in the release of energy) and anabolic processes (the synthesis of components such as proteins, lipids, and nucleic acids, which costs energy). Cellular (or intermediary) metabolism is organized in separate chemical pathways formed by a chain of linked enzymatic reactions in wh...

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“…Knockdown of MTHFD2 in breast cancer cells suppressed proliferation and induced apoptosis (20). Multiple studies indicated that the folate cycle is an important metabolic pathway crucial to cancer growth (11,20,(22)(23)(24). A recent study showed that the folate cycle, through NADPH production, enabled melanoma cells to endure oxidative stress during metastasis (25).…”

Section: Introductionmentioning

confidence: 99%