Biology subjects

TeSlaa, T.

Publications and source records attributed to TeSlaa, T..

7 recordsLinked to original sources

bioRxiv2026

Flexibility of systemic one-carbon metabolism partially buffers dietary methyl donor deficiency

Choline is a methyl-rich nutrient used in lipid synthesis and catabolized to support one-carbon metabolism. Choline consumption in most humans remains less than the suggested adequate intake, yet how systemic metabolism compensates for choline deficiency is not fully described. Here, we use in vivo stable isotope tracing to explore the fate of choline in mammalian tissues. We find that choline is catabolized in the liver to support both the methionine cycle and the mitochondrial folate cycle in addition to its role in lipid synthesis. When dietary methyl donors are deficient, surprisingly, we find maintained systemic choline and methionine fluxes, but diminished contribution of choline to the folate cycle. To compensate for dietary methyl deficiency, systemic flux of serine is doubled by increased kidney synthesis which supplies one-carbon units for increased methionine synthesis in the liver. Our study suggests that systemic one-carbon flexibility can compensate for nutritional methyl deficiency by inter-organ nutrient exchange.

physiology↗

bioRxiv2026

Illuminating spatial dynamics of glutamine metabolism with a sensitive genetically encoded biosensor

Glutamine is the most abundant amino acid in serum, used as a key nutrient by cells for protein synthesis, energy production, carbon and nitrogen metabolism, and cellular redox balance. The use of glutamine in the cell is highly compartmentalized, but the dynamics of glutamine metabolism across organelles and individual cells are not fully understood. To illuminate subcellular glutamine dynamics, we developed a green fluorescent protein-based intracellular glutamine optical reporter, iGlo. We find iGlo is sensitive and specific for glutamine and can be used to measure glutamine uptake, production, and consumption with high spatiotemporal resolution in multiple cell types. Furthermore, multiplexed imaging of iGlo with a lactate biosensor in single cells reveals the temporal crosstalk between glucose and glutamine metabolism to maintain energy homeostasis. Thus, iGlo enables the sensitive and precise study of compartmentalized glutamine dynamics and represents a new and enhanced tool for studying the spatiotemporal dynamics and regulation of metabolism.

biochemistry↗

bioRxiv2025

Spatial regulation of AMPK activity under oxidative stress requires LKB1

AMP-activated protein kinase (AMPK) is a central regulator of cellular energy homeostasis, with over 100 identified downstream targets throughout the cell. In response to cellular stress, including energetic stress, AMPK is activated via binding of AMP and phosphorylation by upstream kinases, including liver kinase B1 (LKB1). We and others have found that the activation of AMPK in response to cellular stress has distinct subcellular mechanisms, indicating compartmentalized regulation of AMPK signaling. Oxidative stress is known to stimulate AMPK activity, but how AMPK is spatially regulated by oxidative stress is underexplored. Using a single-fluorophore excitation-ratiometric AMPK activity reporter (ExRai AMPKAR), we find that oxidative stress induced by hydrogen peroxide (H2O2) results in AMPK activity with distinct spatiotemporal dynamics. We found that in the cytoplasm, nucleus, outer mitochondrial membrane, and cytosolic lysosomal surface, phosphorylation of AMPK by LKB1 is required for AMPK activity. Using a biosensor for ATP, we found at the cytoplasm and lysosome local ATP depletion dictates kinetics of AMPK activity. Using a multi- omics approach, we discover that in response to oxidative stress, AMPK mediates significant metabolic and gene expression changes, including upregulation of oxidative stress response through nuclear factor erythroid 2-related factor 2 (NRF2). Expanding on this identified mechanism, we find that non-small cell lung cancers harboring Kelch-like ECH-associated protein 1 (KEAP1) mutations have a functionally deficient LKB1-AMPK signaling network in response to oxidative stress. Altogether, this work provides new insights into how the subcellular environment influences localized AMPK activity, and identifies how AMPK regulates the cellular response to oxidative stress.

biochemistry↗

bioRxiv2024

A Genetically Encoded Fluorescent Biosensor for Intracellular Measurement of Malonyl-CoA

Malonyl-CoA is the essential building block of fatty acids and regulates cell function through protein malonylation and allosteric regulation of signaling networks. Accordingly, the production and use of malonyl-CoA is finely tuned by the cellular energy status. Most studies of malonyl-CoA dynamics rely on bulk approaches that take only a snapshot of the average metabolic state of a population of cells, missing out on dynamic changes in malonyl-CoA and fatty acid biosynthesis that could be occurring within a single cell. To overcome this limitation, we have developed a genetically encoded fluorescent protein-based biosensor for malonyl-CoA that can be used to capture malonyl-CoA dynamics in single cells. This biosensor, termed Malibu (malonyl-CoA intracellular biosensor to understand dynamics), exhibits an excitation-ratiometric change in response to malonyl-CoA binding. We first used Malibu to monitor malonyl-CoA dynamics during inhibition of fatty acid biosynthesis using cerulenin in E. coli, observing an increase in Malibu response in a time- and dose-dependent manner. In HeLa cells, we used Malibu to monitor the impact of fatty acid biosynthesis inhibition on malonyl-CoA dynamics in single cells, finding that two inhibitors of fatty acid biosynthesis, cerulenin and orlistat, which inhibit different steps of fatty acid biosynthesis, increase malonyl-CoA levels. Altogether, we have developed a new genetically encoded biosensor for malonyl-CoA, which can be used to sensitively study malonyl-CoA dynamics in single cells, providing an unparalleled view into fatty acid biosynthesis.

biochemistry↗

bioRxiv2021

Slow TCA flux implies low ATP production in tumors

The tricarboxylic acid (TCA) cycle oxidizes carbon substrates to carbon dioxide, with the resulting high energy electrons fed into the electron transport chain to produce ATP by oxidative phosphorylation. Healthy tissues derive most of their ATP from oxidative metabolism, and the remainder from glycolysis. The corresponding balance in tumors remains unclear. Tumors upregulate aerobic glycolysis (the Warburg effect), yet they also typically require an intact TCA cycle and electron transport chain1-6. Recent studies have measured which nutrients contribute carbon to the tumor TCA metabolites7,8, but not tumor TCA flux: how fast the cycle turns. Here, we develop and validate an in vivo dynamic isotope tracing-mass spectrometry strategy for TCA flux quantitation, which we apply to all major mouse organs and to five tumor models. We show that, compared to the tissue of origin, tumor TCA flux is markedly suppressed. Complementary glycolytic flux measurements confirm tumor glycolysis acceleration, but the majority of tumor ATP is nevertheless made aerobically, and total tumor ATP production is suppressed compared to healthy tissues. In murine pancreatic cancer, this is accommodated by downregulation of the major energy-using pathway in the healthy exocrine pancreas, protein synthesis. Thus, instead of being hypermetabolic as commonly assumed, tumors apparently make ATP at a lower than normal rate. We propose that, as cells de-differentiate into cancer, they eschew ATP-intensive processes characteristic of the host tissue, and that the resulting suppressed ATP demand contributes to the Warburg effect and facilitates cancer growth in the nutrient-poor tumor microenvironment.

cancer biology↗

bioRxiv2021

Serine catabolism generates NADPH to support hepatic lipogenesis

Carbohydrate can be converted into fat by de novo lipogenesis1,2. This process is known to occur in adipose and liver, and its activity is upregulated in fatty liver disease3. Chemically, de novo lipogenesis involves polymerization and reduction of acetyl-CoA, using NADPH as the electron donor1. While regulation of the responsible enzymes has been extensively studied, the feedstocks used to generate acetyl-CoA and NADPH remain unclear. Here we show that, while de novo lipogenesis in adipose is supported by glucose and its catabolism via the pentose phosphate pathway to make NADPH, liver makes fat without relying on glucose. Instead, liver derives acetyl-CoA from acetate and lactate, and NADPH from folate-mediated serine catabolism. Such NADPH generation involves the cytosolic serine pathway running in liver in the opposite direction observed in most tissues and tumors4,5, with NADPH made by the SHMT1-MTHFD1-ALDH1L1 reaction sequence. Thus, specifically in liver, folate metabolism is wired to support cytosolic NADPH production for lipogenesis. More generally, while the same enzymes are involved in fat synthesis in liver and adipose, different substrates are utilized, opening the door to tissue-specific pharmacological interventions.

biochemistry↗

bioRxiv2020

Quantitative fluxomics of circulating metabolites

Mammalian organs are nourished by nutrients carried by the blood circulation. These nutrients originate from diet and internal stores, and can undergo various interconversions before their eventual use as tissue fuel. Here we develop isotope tracing, mass spectrometry, and mathematical analysis methods to determine the direct sources of circulating nutrients, their interconversion rates, and eventual tissue-specific contributions to TCA cycle metabolism. Experiments with fifteen nutrient tracers enabled extensive accounting both for circulatory metabolic cycles and tissue TCA inputs, across fed and fasted mice on either high carbohydrate or ketogenic diet. We find that a majority of circulating carbon flux is carried by two major cycles: glucose-lactate and triglyceride-glycerol-fatty acid. Futile cycling through these pathways is prominent when dietary content of the associated nutrients is low, rendering internal metabolic activity robust to food choice. The presented in vivo flux quantification methods are broadly applicable to different physiological and disease states.

systems biology↗