Host nutrient milieu drives an essential role for aspartate biosynthesis during invasiveStaphylococcus aureusinfection

The bacterial pathogenStaphylococcus aureusis capable of infecting a broad spectrum of host tissues, in part due to flexibility of metabolic programs.S. aureus, like all organisms, requires essential biosynthetic intermediates to synthesize macromolecules. We therefore sought to determine the metabolic pathways contributing to synthesis of essential precursors during invasiveS. aureusinfection. We focused specifically on staphylococcal infection of bone, one of the most common sites of invasiveS. aureusinfection and a unique environment characterized by dynamic substrate accessibility, infection-induced hypoxia, and a metabolic profile skewed toward aerobic glycolysis. Using a murine model of osteomyelitis, we examined survival ofS. aureusmutants deficient in central metabolic pathways, including glycolysis, gluconeogenesis, the tricarboxylic acid (TCA) cycle, and amino acid synthesis/catabolism. Despite the high glycolytic demand of skeletal cells, we discovered thatS. aureusrequires glycolysis for survival in bone. Furthermore, the TCA cycle is dispensable for survival during osteomyelitis, andS. aureusinstead has a critical need for anaplerosis. Bacterial synthesis of aspartate in particular is absolutely essential for staphylococcal survival in bone, despite the presence of an aspartate transporter, which we identified as GltT and confirmed biochemically. This dependence on endogenous aspartate synthesis derives from the presence of excess glutamate in infected tissue, which inhibits aspartate acquisition byS. aureus. Together, these data elucidate the metabolic pathways required for staphylococcal infection within bone and demonstrate that the host nutrient milieu can determine essentiality of bacterial nutrient biosynthesis pathways despite the presence of dedicated transporters.

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Metabolic Constants and Plasticity of Cancer Cells in a Limiting Glucose and Glutamine Microenvironment—A Pyruvate Perspective

Frontiers in Oncology ◽

10.3389/fonc.2020.596197 ◽

2020 ◽

Vol 10 ◽

Author(s):

Angela M. Otto

Keyword(s):

Cancer Cells ◽

Metabolic Network ◽

Metabolic Pathways ◽

Cancer Cell Line ◽

Tca Cycle ◽

Reaction Rates ◽

Diagnostic Methods ◽

Metabolic Reprogramming ◽

Amino Acid Synthesis ◽

The Tca Cycle

The metabolism of cancer cells is an issue of dealing with fluctuating and limiting levels of nutrients in a precarious microenvironment to ensure their vitality and propagation. Glucose and glutamine are central metabolites for catabolic and anabolic metabolism, which is in the limelight of numerous diagnostic methods and therapeutic targeting. Understanding tumor metabolism in conditions of nutrient depletion is important for such applications and for interpreting the readouts. To exemplify the metabolic network of tumor cells in a model system, the fate 13C6-glucose was tracked in a breast cancer cell line growing in variable low glucose/low glutamine conditions. 13C-glucose-derived metabolites allowed to deduce the engagement of metabolic pathways, namely glycolysis, the TCA-cycle including glutamine and pyruvate anaplerosis, amino acid synthesis (serine, glycine, aspartate, glutamate), gluconeogenesis, and pyruvate replenishment. While the metabolic program did not change, limiting glucose and glutamine supply reduced cellular metabolite levels and enhanced pyruvate recycling as well as pyruvate carboxylation for entry into the TCA-cycle. Otherwise, the same metabolic pathways, including gluconeogenesis, were similarly engaged with physiologically saturating as with limiting glucose and glutamine. Therefore, the metabolic plasticity in precarious nutritional microenvironment does not require metabolic reprogramming, but is based on dynamic changes in metabolite quantity, reaction rates, and directions of the existing metabolic network.

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Accelerated Metabolite Levels of Aerobic Glycolysis and the Pentose Phosphate Pathway Are Required for Efficient Replication of Infectious Spleen and Kidney Necrosis Virus in Chinese Perch Brain Cells

Biomolecules ◽

10.3390/biom9090440 ◽

2019 ◽

Vol 9 (9) ◽

pp. 440

Author(s):

Xixi Guo ◽

Shiwei Wu ◽

Ningqiu Li ◽

Qiang Lin ◽

Lihui Liu ◽

...

Keyword(s):

Pentose Phosphate Pathway ◽

Late Stage ◽

Metabolic Pathways ◽

Aerobic Glycolysis ◽

Tca Cycle ◽

Pentose Phosphate ◽

Infection Cycle ◽

Necrosis Virus ◽

The Tca Cycle ◽

Chinese Perch

Glucose is a main carbon and energy source for virus proliferation and is usually involved in the glycolysis, pentose phosphate pathway (PPP), and tricarboxylic acid cycle (TCA cycle) pathways. In this study, we investigated the roles of glucose-related metabolic pathways during the replication of infectious spleen and kidney necrosis virus (ISKNV), which has caused serious economic losses in the cultured Chinese perch (Siniperca chuatsi) industry. We found that ISKNV infection enhanced the metabolic pathways of the PPP and the TCA cycle at the early stage of the ISKNV infection cycle and enhanced the glycolysis pathway at the late stage of the ISKNV infection cycle though the comprehensive analysis of transcriptomics, proteomics, and metabolomics. The advanced results proved that ISKNV replication induced upregulation of aerobic glycolysis at the late stage of ISKNV infection cycle and aerobic glycolysis were required for ISKNV multiplication. In addition, the PPP, providing nucleotide biosynthesis, was also required for ISKNV multiplication. However, the TCA cycle involving glucose was not important and necessary for ISKNV multiplication. The results reported here provide new insights into viral pathogenesis mechanism of metabolic shift, as well as antiviral treatment strategies.

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Yeast Aconitase in Two Locations and Two Metabolic Pathways: Seeing Small Amounts Is Believing

Molecular Biology of the Cell ◽

10.1091/mbc.e04-11-1028 ◽

2005 ◽

Vol 16 (9) ◽

pp. 4163-4171 ◽

Cited By ~ 87

Author(s):

Neta Regev-Rudzki ◽

Sharon Karniely ◽

Nitzan Natani Ben-Haim ◽

Ophry Pines

Keyword(s):

Metabolic Pathways ◽

Tca Cycle ◽

Tricarboxylic Acid ◽

Glyoxylate Shunt ◽

Mitochondrial Matrix ◽

Hybrid Gene ◽

Subcellular Compartments ◽

The Tca Cycle ◽

Dual Distribution ◽

Fundamental Process

The distribution of identical enzymatic activities between different subcellular compartments is a fundamental process of living cells. At present, the Saccharomyces cerevisiae aconitase enzyme has been detected only in mitochondria, where it functions in the tricarboxylic acid (TCA) cycle and is considered a mitochondrial matrix marker. We developed two strategies for physical and functional detection of aconitase in the yeast cytosol: 1) we fused the α peptide of the β-galactosidase enzyme to aconitase and observed α complementation in the cytosol; and 2) we created an ACO1-URA3 hybrid gene, which allowed isolation of strains in which the hybrid protein is exclusively targeted to mitochondria. These strains display a specific phenotype consistent with glyoxylate shunt elimination. Together, our data indicate that yeast aconitase isoenzymes distribute between two distinct subcellular compartments and participate in two separate metabolic pathways; the glyoxylate shunt in the cytosol and the TCA cycle in mitochondria. We maintain that such dual distribution phenomena have a wider occurrence than recorded currently, the reason being that in certain cases there is a small fraction of one of the isoenzymes, in one of the locations, making its detection very difficult. We term this phenomenon of highly uneven isoenzyme distribution “eclipsed distribution.”

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Identification of two [4Fe–4S]-cluster-containing hydro-lyases from Pyrococcus furiosus

Microbiology ◽

10.1099/mic.0.030320-0 ◽

2009 ◽

Vol 155 (9) ◽

pp. 3015-3020 ◽

Cited By ~ 14

Author(s):

Barbara M. A. van Vugt-Lussenburg ◽

Laura van der Weel ◽

Wilfred R. Hagen ◽

Peter-Leon Hagedoorn

Keyword(s):

Pyrococcus Furiosus ◽

Tca Cycle ◽

Acid Synthesis ◽

Tricarboxylic Acid ◽

Energy Transduction ◽

Amino Acid Synthesis ◽

Tca Cycle Enzymes ◽

Pyrococcus Abyssi ◽

Fumarate Hydratases

The hyperthermophilic archaeon Pyrococcus furiosus is a strict anaerobe. It is therefore not expected to use the oxidative tricarboxylic acid (TCA) cycle for energy transduction. Nonetheless, its genome encodes more putative TCA cycle enzymes than the closely related Pyrococcus horikoshii and Pyrococcus abyssi, including an aconitase (PF0201). Furthermore, a two-subunit fumarase (PF1755 and PF1754) is encoded on the Pyr. furiosus genome. In the present study, these three genes were heterologously overexpressed in Escherichia coli to enable characterization of the enzymes. PF1755 and PF1754 were shown to form a [4Fe–4S]-cluster-containing heterodimeric enzyme, able to catalyse the reversible hydratation of fumarate. The aconitase PF0201 also contained an Fe–S cluster, and catalysed the conversion from citrate to isocitrate. The fumarase belongs to the class of two-subunit, [4Fe–4S]-cluster-containing fumarate hydratases exemplified by MmcBC from Pelotomaculum thermopropionicum; the aconitase belongs to the aconitase A family. Aconitase probably plays a role in amino acid synthesis when the organism grows on carbohydrates. However, the function of the seemingly metabolically isolated fumarase in Pyr. furiosus has yet to be established.

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The Metabolic Fates of Pyruvate in Normal and Neoplastic Cells

Cells ◽

10.3390/cells10040762 ◽

2021 ◽

Vol 10 (4) ◽

pp. 762

Author(s):

Edward V. Prochownik ◽

Huabo Wang

Keyword(s):

Metabolic Pathways ◽

Redox State ◽

Pyruvate Dehydrogenase Complex ◽

Tca Cycle ◽

Vascular Supply ◽

Extrinsic Factors ◽

The Tca Cycle ◽

Initial Substrate ◽

Numerous Cell ◽

Bio Synthesis

Pyruvate occupies a central metabolic node by virtue of its position at the crossroads of glycolysis and the tricarboxylic acid (TCA) cycle and its production and fate being governed by numerous cell-intrinsic and extrinsic factors. The former includes the cell’s type, redox state, ATP content, metabolic requirements and the activities of other metabolic pathways. The latter include the extracellular oxygen concentration, pH and nutrient levels, which are in turn governed by the vascular supply. Within this context, we discuss the six pathways that influence pyruvate content and utilization: 1. The lactate dehydrogenase pathway that either converts excess pyruvate to lactate or that regenerates pyruvate from lactate for use as a fuel or biosynthetic substrate; 2. The alanine pathway that generates alanine and other amino acids; 3. The pyruvate dehydrogenase complex pathway that provides acetyl-CoA, the TCA cycle’s initial substrate; 4. The pyruvate carboxylase reaction that anaplerotically supplies oxaloacetate; 5. The malic enzyme pathway that also links glycolysis and the TCA cycle and generates NADPH to support lipid bio-synthesis; and 6. The acetate bio-synthetic pathway that converts pyruvate directly to acetate. The review discusses the mechanisms controlling these pathways, how they cross-talk and how they cooperate and are regulated to maximize growth and achieve metabolic and energetic harmony.

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Comprehensive Plasma Metabolomic Profile of Patients with Advanced Neuroendocrine Tumors (NETs). Diagnostic and Biological Relevance

Cancers ◽

10.3390/cancers13112634 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2634

Author(s):

Beatriz Soldevilla ◽

Angeles López-López ◽

Alberto Lens-Pardo ◽

Carlos Carretero-Puche ◽

Angeles Lopez-Gonzalvez ◽

...

Keyword(s):

Metabolic Pathways ◽

Metabolic Networks ◽

Tca Cycle ◽

Metabolomic Profile ◽

Diagnostic Potential ◽

The Tca Cycle ◽

Novel Biomarkers ◽

Potential Methods ◽

Clinical Potential ◽

First Time

Purpose: High-throughput “-omic” technologies have enabled the detailed analysis of metabolic networks in several cancers, but NETs have not been explored to date. We aim to assess the metabolomic profile of NET patients to understand metabolic deregulation in these tumors and identify novel biomarkers with clinical potential. Methods: Plasma samples from 77 NETs and 68 controls were profiled by GC−MS, CE−MS and LC−MS untargeted metabolomics. OPLS-DA was performed to evaluate metabolomic differences. Related pathways were explored using Metaboanalyst 4.0. Finally, ROC and OPLS-DA analyses were performed to select metabolites with biomarker potential. Results: We identified 155 differential compounds between NETs and controls. We have detected an increase of bile acids, sugars, oxidized lipids and oxidized products from arachidonic acid and a decrease of carnitine levels in NETs. MPA/MSEA identified 32 enriched metabolic pathways in NETs related with the TCA cycle and amino acid metabolism. Finally, OPLS-DA and ROC analysis revealed 48 metabolites with diagnostic potential. Conclusions: This study provides, for the first time, a comprehensive metabolic profile of NET patients and identifies a distinctive metabolic signature in plasma of potential clinical use. A reduced set of metabolites of high diagnostic accuracy has been identified. Additionally, new enriched metabolic pathways annotated may open innovative avenues of clinical research.

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Intracellular Fate of Universally Labelled 13C Isotopic Tracers of Glucose and Xylose in Central Metabolic Pathways of Xanthomonas oryzae

Metabolites ◽

10.3390/metabo8040066 ◽

2018 ◽

Vol 8 (4) ◽

pp. 66 ◽

Cited By ~ 4

Author(s):

Manu Shree ◽

Shyam K. Masakapalli

Keyword(s):

Amino Acids ◽

Metabolic Pathways ◽

Metabolic Networks ◽

Tca Cycle ◽

Xanthomonas Oryzae ◽

Flux Analysis ◽

Isotopic Tracers ◽

Feeding Experiments ◽

The Tca Cycle ◽

Metabolic Route

The goal of this study is to map the metabolic pathways of poorly understood bacterial phytopathogen, Xanthomonas oryzae (Xoo) BXO43 fed with plant mimicking media XOM2 containing glutamate, methionine and either 40% [13C5] xylose or 40% [13C6] glucose. The metabolic networks mapped using the KEGG mapper and the mass isotopomer fragments of proteinogenic amino acids derived from GC-MS provided insights into the activities of Xoo central metabolic pathways. The average 13C in histidine, aspartate and other amino acids confirmed the activities of PPP, the TCA cycle and amino acid biosynthetic routes, respectively. The similar labelling patterns of amino acids (His, Ala, Ser, Val and Gly) from glucose and xylose feeding experiments suggests that PPP would be the main metabolic route in Xoo. Owing to the lack of annotated gene phosphoglucoisomerase in BXO43, the 13C incorporation in alanine could not be attributed to the competing pathways and hence warrants additional positional labelling experiments. The negligible presence of 13C incorporation in methionine brings into question its potential role in metabolism and pathogenicity. The extent of the average 13C labelling in several amino acids highlighted the contribution of pre-existing pools that need to be accounted for in 13C-flux analysis studies. This study provided the first qualitative insights into central carbon metabolic pathway activities in Xoo.

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Gluconeogenesis from labeled carbon: estimating isotope dilution

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1986.250.3.e296 ◽

1986 ◽

Vol 250 (3) ◽

pp. E296-E305 ◽

Cited By ~ 3

Author(s):

J. K. Kelleher

Keyword(s):

Steady State ◽

Isotope Dilution ◽

Experimental Tests ◽

Tca Cycle ◽

Tricarboxylic Acid ◽

Complex Model ◽

Acetyl Coa ◽

The Tca Cycle ◽

Carbon Compounds ◽

Mathematical Techniques

To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoA and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA.

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KSHV Reprogramming of Host Energy Metabolism for Pathogenesis

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.621156 ◽

2021 ◽

Vol 11 ◽

Author(s):

Xiaoqing Liu ◽

Caixia Zhu ◽

Yuyan Wang ◽

Fang Wei ◽

Qiliang Cai

Keyword(s):

Energy Metabolism ◽

Metabolic Pathways ◽

B Lymphocyte ◽

Aerobic Glycolysis ◽

Cell Metabolism ◽

Acid Synthesis ◽

Central Carbon Metabolism ◽

Central Carbon ◽

Cell Energy ◽

Infected Cells

Reprogramming of energy metabolism is a key for cancer development. Kaposi’s sarcoma-associated herpesvirus (KSHV), a human oncogenic herpesvirus, is tightly associated with several human malignancies by infecting B-lymphocyte or endothelial cells. Cancer cell energy metabolism is mainly dominated by three pathways of central carbon metabolism, including aerobic glycolysis, glutaminolysis, and fatty acid synthesis. Increasing evidence has shown that KSHV infection can alter central carbon metabolic pathways to produce biomass for viral replication, as well as the survival and proliferation of infected cells. In this review, we summarize recent studies exploring how KSHV manipulates host cell metabolism to promote viral pathogenesis, which provides the potential therapeutic targets and strategies for KSHV-associated cancers.

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Staphylococcus epidermidis Polysaccharide Intercellular Adhesin Production Significantly Increases during Tricarboxylic Acid Cycle Stress

Journal of Bacteriology ◽

10.1128/jb.187.9.2967-2973.2005 ◽

2005 ◽

Vol 187 (9) ◽

pp. 2967-2973 ◽

Cited By ~ 71

Author(s):

Cuong Vuong ◽

Joshua B. Kidder ◽

Erik R. Jacobson ◽

Michael Otto ◽

Richard A. Proctor ◽

...

Keyword(s):

Staphylococcus Epidermidis ◽

Tricarboxylic Acid Cycle ◽

Tca Cycle ◽

Redox Status ◽

Tricarboxylic Acid ◽

Polysaccharide Intercellular Adhesin ◽

Low Oxygen ◽

Acid Cycle ◽

The Tca Cycle ◽

High Concentrations

ABSTRACT Staphylococcal polysaccharide intercellular adhesin (PIA) is important for the development of a mature biofilm. PIA production is increased during growth in a nutrient-replete or iron-limited medium and under conditions of low oxygen availability. Additionally, stress-inducing stimuli such as heat, ethanol, and high concentrations of salt increase the production of PIA. These same environmental conditions are known to repress tricarboxylic acid (TCA) cycle activity, leading us to hypothesize that altering TCA cycle activity would affect PIA production. Culturing Staphylococcus epidermidis with a low concentration of the TCA cycle inhibitor fluorocitrate dramatically increased PIA production without impairing glucose catabolism, the growth rate, or the growth yields. These data lead us to speculate that one mechanism by which staphylococci perceive external environmental change is through alterations in TCA cycle activity leading to changes in the intracellular levels of biosynthetic intermediates, ATP, or the redox status of the cell. These changes in the metabolic status of the bacteria result in the attenuation or augmentation of PIA production.

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