We developed a temporal-fluxomics approach to derive a comprehensive and quantitative view of alterations in metabolic fluxes throughout the mammalian cell cycle (Ahn et al., Molecular Systems Biology, 2017). We developed a spatial-fluxomics approach to infer metabolic fluxes in mitochondria and cytosol, combining isotope tracing, rapid subcellular fractionation, LC-MS-based metabolomics, computational deconvolution, and metabolic network modeling (Lee et al., Nature Communications 2019.). Considering the technical complexity in performing rapid cell fractionation and optimizing the approach for specific cells of interest, we developed a complementary approach for inferring subcellular metabolic activities strictly based on measurements performed with intact cells under physiological conditions. A revision of our paper on this topic by Stern et al is under review in Nature Communications.
Performing temporal-fluxomics analysis of cultured HeLa cells shows, for the first time, that TCA cycle fluxes are rewired as cells progress through the cell cycle with complementary oscillations of glucose versus glutamine-derived fluxes. We applied our spatial-fluxomics method to investigate the interplay between mitochondrial, nuclear, and cytosolic reactions involved in the production of acetyl-CoA in cancer cell lines, an important metabolic precursor for energy production, fatty-acid biosynthesis, and protein acetylation.
We applied different variants of spatial-fluxomics analysis to analyze subcellular compartmentalized metabolic fluxes and their regulation in a folate acid metabolism across cancer cells. In one study, we revealed a novel dependence of cancer cells specifically on the cytosolic serine hydroxymethyltransferase (SHMT1) in cancer cells – in contrast to the acceptable view of the mitochondrial pathway serving as the as the major source of one-carbon units in cancer cells (Lee et al., Cell Metabolism 2021). In another study, we quantified flux through mitochondrial glycine -cleavage system in cancer cell lines (Mukha et al, Cell Metabolism 2022). We found substantial and previously uncharacterized high flux in hepatocellular carcinoma (HCC) cells, supporting nucleotide biosynthesis.