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Cell Metabolism Nov 2023Emerging studies have addressed the tumor-promoting role of fructose in different cancers. The effects and pathological mechanisms of high dietary fructose on...
Emerging studies have addressed the tumor-promoting role of fructose in different cancers. The effects and pathological mechanisms of high dietary fructose on hepatocellular carcinoma (HCC) remain unclear. Here, we examined the effects of fructose supplementation on HCC progression in wild-type C57BL/6 mice using a spontaneous and chemically induced HCC mouse model. We show that elevated uridine diphospho-N-acetylglucosamine (UDP-GlcNAc) and O-GlcNAcylation levels induced by high dietary fructose contribute to HCC progression. Non-targeted metabolomics and stable isotope tracing revealed that under fructose treatment, microbiota-derived acetate upregulates glutamine and UDP-GlcNAc levels and enhances protein O-GlcNAcylation in HCC. Global profiling of O-GlcNAcylation revealed that hyper-O-GlcNAcylation of eukaryotic elongation factor 1A1 promotes cell proliferation and tumor growth. Targeting glutamate-ammonia ligase or O-linked N-acetylglucosamine transferase (OGT) remarkably impeded HCC progression in mice with high fructose intake. We propose that high dietary fructose promotes HCC progression through microbial acetate-induced hyper-O-GlcNAcylation.
Topics: Mice; Animals; Carcinoma, Hepatocellular; Liver Neoplasms; Mice, Inbred C57BL; Cell Proliferation; Uridine Diphosphate; N-Acetylglucosaminyltransferases; Acetylglucosamine; Protein Processing, Post-Translational
PubMed: 37797623
DOI: 10.1016/j.cmet.2023.09.009 -
Science (New York, N.Y.) Feb 2024The identification of mechanisms to store glucose carbon in the form of glycogen rather than fat in hepatocytes has important implications for the prevention of...
The identification of mechanisms to store glucose carbon in the form of glycogen rather than fat in hepatocytes has important implications for the prevention of nonalcoholic fatty liver disease (NAFLD) and other chronic metabolic diseases. In this work, we show that glycogenesis uses its intermediate metabolite uridine diphosphate glucose (UDPG) to antagonize lipogenesis, thus steering both mouse and human hepatocytes toward storing glucose carbon as glycogen. The underlying mechanism involves transport of UDPG to the Golgi apparatus, where it binds to site-1 protease (S1P) and inhibits S1P-mediated cleavage of sterol regulatory element-binding proteins (SREBPs), thereby inhibiting lipogenesis in hepatocytes. Consistent with this mechanism, UDPG administration is effective at treating NAFLD in a mouse model and human organoids. These findings indicate a potential opportunity to ameliorate disordered fat metabolism in the liver.
Topics: Animals; Humans; Male; Mice; Carbon; Glucose; HEK293 Cells; Hepatocytes; Lipogenesis; Liver; Liver Glycogen; Mice, Inbred C57BL; Non-alcoholic Fatty Liver Disease; Proprotein Convertases; Serine Endopeptidases; Sterol Regulatory Element Binding Protein 1; Uridine Diphosphate Glucose
PubMed: 38359126
DOI: 10.1126/science.adi3332 -
Nature Nov 2023Identifying metabolic steps that are specifically required for the survival of cancer cells but are dispensable in normal cells remains a challenge. Here we report a...
Identifying metabolic steps that are specifically required for the survival of cancer cells but are dispensable in normal cells remains a challenge. Here we report a therapeutic vulnerability in a sugar nucleotide biosynthetic pathway that can be exploited in cancer cells with only a limited impact on normal cells. A systematic examination of conditionally essential metabolic enzymes revealed that UXS1, a Golgi enzyme that converts one sugar nucleotide (UDP-glucuronic acid, UDPGA) to another (UDP-xylose), is essential only in cells that express high levels of the enzyme immediately upstream of it, UGDH. This conditional relationship exists because UXS1 is required to prevent excess accumulation of UDPGA, which is produced by UGDH. UXS1 not only clears away UDPGA but also limits its production through negative feedback on UGDH. Excess UDPGA disrupts Golgi morphology and function, which impedes the trafficking of surface receptors such as EGFR to the plasma membrane and diminishes the signalling capacity of cells. UGDH expression is elevated in several cancers, including lung adenocarcinoma, and is further enhanced during chemoresistant selection. As a result, these cancer cells are selectively dependent on UXS1 for UDPGA detoxification, revealing a potential weakness in tumours with high levels of UGDH.
Topics: Humans; Neoplasms; Signal Transduction; Uridine Diphosphate Glucuronic Acid; Uridine Diphosphate Xylose; Adenocarcinoma of Lung; Lung Neoplasms
PubMed: 37880368
DOI: 10.1038/s41586-023-06676-3 -
Accounts of Chemical Research May 2024In 1960, Weber prophesied that "There are many ways in which the properties of the excited state can be utilized to study points of ignorance of the structure and...
In 1960, Weber prophesied that "There are many ways in which the properties of the excited state can be utilized to study points of ignorance of the structure and function of proteins". This has been realized, illustrating that an intrinsic and highly responsive fluorophore such as tryptophan can alter the course of an entire scientific discipline. But what about RNA and DNA? Adapting Weber's protein photophysics prophecy to nucleic acids requires the development of intrinsically emissive nucleoside surrogates as, unlike Trp, the canonical nucleobases display unusually low emission quantum yields, which render nucleosides, nucleotides, and oligonucleotides practically dark for most fluorescence-based applications.Over the past decades, we have developed emissive nucleoside surrogates that facilitate the monitoring of nucleoside-, nucleotide-, and nucleic acid-based transformations at a nucleobase resolution in real time. The premise underlying our approach is the identification of minimal atomic/structural perturbations that endow the synthetic analogs with favorable photophysical features while maintaining native conformations and pairing. As illuminating probes, the photophysical parameters of such isomorphic nucleosides display sensitivity to microenvironmental factors. Responsive isomorphic analogs that function similarly to their native counterparts in biochemical contexts are defined as isofunctional.Early analogs included pyrimidines substituted with five-membered aromatic heterocycles at their 5 position and have been used to assess the polarity of the major groove in duplexes. Polarized quinazolines have proven useful in assembling FRET pairs with established fluorophores and have been used to study RNA-protein and RNA-small-molecule binding. Completing a fluorescent ribonucleoside alphabet, composed of visibly emissive purine (A, G) and pyrimidine (U, C) analogs, all derived from thieno[3,4-]pyrimidine as the heterocyclic nucleus, was a major breakthrough. To further augment functionality, a second-generation emissive RNA alphabet based on an isothiazolo[4,3-]pyrimidine core (A, G, U, and C) was fabricated. This single-atom "mutagenesis" restored the basic/coordinating nitrogen corresponding to N7 in the purine skeleton and elevated biological recognition.The isomorphic emissive nucleosides and nucleotides, particularly the purine analogs, serve as substrates for diverse enzymes. Beyond polymerases, we have challenged the emissive analogs with metabolic and catabolic enzymes, opening optical windows into the biochemistry of nucleosides and nucleotides as metabolites as well as coenzymes and second messengers. Real-time fluorescence-based assays for adenosine deaminase, guanine deaminase, and cytidine deaminase have been fabricated and used for inhibitor discovery. Emissive cofactors (e.g., SAM), coenzymes (e.g., NAD), and second messengers (e.g., c-di-GMP) have been enzymatically synthesized, using NTPs and native enzymes. Both their biosynthesis and their transformations can be fluorescently monitored in real time.Highly isomorphic and isofunctional emissive surrogates can therefore be fabricated and judiciously implemented. Beyond their utility, side-by-side comparison to established analogs, particularly to 2-aminopurine, the workhorse of nucleic acid biophysics over 5 decades, has proven prudent as they refined the scope and limitations of both the new analogs and their predecessors. Challenges, however, remain. Associated with such small heterocycles are relatively short emission wavelengths and limited brightness. Recent advances in multiphoton spectroscopy and further structural modifications have shown promise for overcoming such barriers.
Topics: Fluorescent Dyes; Nucleosides; RNA; DNA
PubMed: 38613490
DOI: 10.1021/acs.accounts.4c00042 -
Neuropharmacology Mar 2024The function of almost all cells of the human and animal body is synchronized by purinergic/pyrimidinergic extracellular signalling molecules. This network activity is...
The function of almost all cells of the human and animal body is synchronized by purinergic/pyrimidinergic extracellular signalling molecules. This network activity is especially efficient in the central and peripheral nervous systems, driven by secretion of the (co)transmitter ATP (including its enzymatic degradation products ADP, AMP, and adenosine), as well as ATP/UTP (including UDP) released from the cytoplasm by either Ca-dependent vesicular exocytosis or by non-exocytotic pathways via a family of diverse channels. It must be pointed out that neural cells (neurons, astrocytes, and oligodendrocytes) are equal sources of nucleotides/nucleosides, as non-neural cells (e.g. the endothelium of small blood vessels). A whole plethora of purinergic receptors responding to the endogenously released purine and pyrimidine nucleotides as well as to adenosine, are instrumental in providing the structural basis for cell stimulation. The present collection of papers summarizes current knowledge and recent findings in the medicinal chemistry, electrophysiology, neuropharmacology and neurobiology of purinergic transmission. Accruing evidence supports the key role of extracellular nucleotides and nucleosides in neuroinflammation, neurodegeneration, and in neuropsychiatric diseases, thus paving the way for pharmacological intervention thanks to the development of novel brain-permeant, drug-like, purinergic ligands. We are confident that these therapies will open a new avenue for the treatment of so far uncurable diseases of the central and peripheral nervous systems.
Topics: Animals; Humans; Nucleotides; Signal Transduction; Adenosine; Receptors, Purinergic; Adenosine Triphosphate
PubMed: 38135034
DOI: 10.1016/j.neuropharm.2023.109826 -
Science (New York, N.Y.) Mar 2024Cellular purines, particularly adenosine 5'-triphosphate (ATP), fuel many metabolic reactions, but less is known about the direct effects of pyrimidines on cellular...
Cellular purines, particularly adenosine 5'-triphosphate (ATP), fuel many metabolic reactions, but less is known about the direct effects of pyrimidines on cellular metabolism. We found that pyrimidines, but not purines, maintain pyruvate oxidation and the tricarboxylic citric acid (TCA) cycle by regulating pyruvate dehydrogenase (PDH) activity. PDH activity requires sufficient substrates and cofactors, including thiamine pyrophosphate (TPP). Depletion of cellular pyrimidines decreased TPP synthesis, a reaction carried out by TPP kinase 1 (TPK1), which reportedly uses ATP to phosphorylate thiamine (vitamin B1). We found that uridine 5'-triphosphate (UTP) acts as the preferred substrate for TPK1, enabling cellular TPP synthesis, PDH activity, TCA-cycle activity, lipogenesis, and adipocyte differentiation. Thus, UTP is required for vitamin B1 utilization to maintain pyruvate oxidation and lipogenesis.
Topics: Adenosine Triphosphate; Lipogenesis; Pyrimidines; Pyruvates; Thiamine; Thiamine Pyrophosphate; Uridine Triphosphate; Oxidation-Reduction; Citric Acid Cycle; Protein Kinases; Humans; HeLa Cells; Pyruvate Dehydrogenase Complex
PubMed: 38547260
DOI: 10.1126/science.adh2771 -
Trends in Cell Biology Nov 2023Nucleotides are the foundational elements of life. Proliferative cells acquire nutrients for energy production and the synthesis of macromolecules, including proteins,... (Review)
Review
Nucleotides are the foundational elements of life. Proliferative cells acquire nutrients for energy production and the synthesis of macromolecules, including proteins, lipids, and nucleic acids. Nucleotides are continuously replenished through the activation of the nucleotide synthesis pathways. Despite the importance of nucleotides in cell physiology, there is still much to learn about how the purine and pyrimidine synthesis pathways are regulated in response to intracellular and exogenous signals. Over the past decade, evidence has emerged that several signaling pathways [Akt, mechanistic target of rapamycin complex I (mTORC1), RAS, TP53, and Hippo-Yes-associated protein (YAP) signaling] alter nucleotide synthesis activity and influence cell function. Here, we examine the mechanisms by which these signaling networks affect de novo nucleotide synthesis in mammalian cells. We also discuss how these molecular links can be targeted in diseases such as cancers and immune disorders.
PubMed: 36967301
DOI: 10.1016/j.tcb.2023.03.003 -
Molecules (Basel, Switzerland) May 2024Azido-modified nucleosides have been extensively explored as substrates for click chemistry and the metabolic labeling of DNA and RNA. These compounds are also of... (Review)
Review
Azido-modified nucleosides have been extensively explored as substrates for click chemistry and the metabolic labeling of DNA and RNA. These compounds are also of interest as precursors for further synthetic elaboration and as therapeutic agents. This review discusses the chemistry of azidonucleosides related to the generation of nitrogen-centered radicals (NCRs) from the azido groups that are selectively inserted into the nucleoside frame along with the subsequent chemistry and biological implications of NCRs. For instance, the critical role of the sulfinylimine radical generated during inhibition of ribonucleotide reductases by 2'-azido-2'-deoxy pyrimidine nucleotides as well as the NCRs generated from azidonucleosides by radiation-produced (prehydrated and aqueous) electrons are discussed. Regio and stereoselectivity of incorporation of an azido group ("radical arm") into the frame of nucleoside and selective generation of NCRs under reductive conditions, which often produce the same radical species that are observed upon ionization events due to radiation and/or other oxidative conditions that are emphasized. NCRs generated from nucleoside-modified precursors other than azidonucleosides are also discussed but only with the direct relation to the same/similar NCRs derived from azidonucleosides.
Topics: Nucleosides; Azides; Nitrogen; Free Radicals; Click Chemistry
PubMed: 38792171
DOI: 10.3390/molecules29102310 -
Genes & Diseases Nov 2023nucleotide biosynthetic pathway is a highly conserved and essential biochemical pathway in almost all organisms. Both purine nucleotides and pyrimidine nucleotides are... (Review)
Review
nucleotide biosynthetic pathway is a highly conserved and essential biochemical pathway in almost all organisms. Both purine nucleotides and pyrimidine nucleotides are necessary for cell metabolism and proliferation. Thus, the dysregulation of the nucleotide biosynthetic pathway contributes to the development of many human diseases, such as cancer. It has been shown that many enzymes in this pathway are overactivated in different cancers. In this review, we summarize and update the current knowledge on the nucleotide biosynthetic pathway, regulatory mechanisms, its role in tumorigenesis, and potential targeting opportunities.
PubMed: 37554216
DOI: 10.1016/j.gendis.2022.04.018