Biology subjects

Letellier, E.

Publications and source records attributed to Letellier, E..

4 recordsLinked to original sources

bioRxiv2023

PKM2 diverts glycolytic flux in dependence on formate overflow

Throughout the metastatic cascade, cancer cells are faced with harsh metabolic environments and nutritional stresses which apply selection pressure leaving only the most metabolically resilient cells to survive and form metastases. Metabolic characterisation of such cell populations in vitro is currently challenging. Using galactose as a tool compound to mimic glycolytic limitation within the tumour microenvironment of primary and secondary neoplastic sites, we were able to uncover metabolic flexibility and plasticity of cancer cells in vitro. In contrast to the established idea that high glycolytic flux and expression of dimeric PKM2 redirects carbons towards anabolic routes such as the pentose phosphate pathway and serine synthesis pathway (SSP), we have discovered by using stable-isotope tracing that also glycolytic limitation results in metabolic rewiring. Surprisingly, despite limited carbon availability and energetic stress, cells induce a near complete block of pyruvate kinase isozyme M2 (PKM2) to divert carbons towards SSP. Simultaneously, TCA cycle flux is sustained and oxygen consumption is increased, both supported by glutamine. Glutamine not only supports TCA cycle flux but also SSP via distinct mechanisms. Due to PKM2 block, malic enzyme exclusively supports TCA cycle flux while mitochondrial phosphoenolpyruvate carboxykinase supports SSP. Moreover, by using genetic modifications of different one-carbon (1C) cycle enzymes, we are able to reverse the PKM2 block suggesting a link between mitochondrial 1C cycle and pyruvate kinase. Thus we show that PKM2 inhibition acts as a branching point to direct glycolytic and glutamine carbons into distinct routes, overall supporting the metabolic plasticity and flexibility of cancer cells.

cancer biology↗

bioRxiv2022

Adaptation to ER-stress via serine glycine metabolism licences STING signalling and CMV control in intestinal epithelial cells

Inflammatory bowel diseases (IBD) are characterized by chronic relapsing inflammation of the gastrointestinal tract. While the molecular causality between endoplasmic reticulum (ER) stress and intestinal inflammation is widely accepted, the metabolic consequences of chronic ER-stress on the pathophysiology of IBD remain unclear. By using in vitro, ex vivo, in vivo mouse models and patient datasets, we identified a distinct polarisation of the mitochondrial one-carbon (1C) metabolism and a fine-tuning of the amino acid uptake in intestinal epithelial cells tailored to support GSH and NADPH metabolism upon chronic ER-stress. This metabolic phenotype strongly correlates with IBD severity and therapy-response. Mechanistically, we uncover that both chronic ER-stress and serine limitation disrupt cGAS/STING-signalling, impairing the epithelial response against viral and bacterial infection, fuelling experimental enteritis. Consequently, antioxidant treatment restores STING function and virus control. Collectively, our data highlight the importance of the plasticity of serine metabolism to allow proper cGAS/STING-signalling and innate immune responses upon chronic inflammation in the gut.

cell biology↗

bioRxiv2022

Highly multiplexed targeted plasma proteomics quantifies several hundred blood proteins in serum from colorectal carcinoma patients

The rapid analysis of human serum and plasma can provide deep insights into changes of the blood proteome in response to different patient treatments or diseases. Targeted proteomics techniques, like SRM and PRM, can be utilized to monitor proteins at high sensitivitym but so far were limited to smaller protein panels, which can be monitored in one experiment. The recently, on a Bruker tims-TOF pro mass spectrometer, developed parallel reaction monitoring-parallel accumulation - serial fragmentation (prm-PASEF) method expands the standard PRM method by using ion-mobility. The use of ion mobility as a fourth separation dimension increases the proteome coverage while reducing the length of the necessary chromatogeaphic separation. By combining an isotope-labeled reference standard, which covers 579 plasma proteins, we were able to quantify 565 proteins in plasma using prm-PASEF, with the least abundant protein being quantified at 7 amol. We continued the analysis by combining the isotype-labeled reference standard with dia-PASEF, which allowed the quantification of 549 proteins. Both methods were used to analyze 20 patient plasma samples from a colorectal cancer (CRC) cohort. The analysis identified 16 differentially regulated proteins between the CRC patient and control individual plasma samples. 15 of the 16 proteins showed a high correlation to the mRNA expression in CRC tumor samples, showing the technique s potential for the rapid identification of potential biomarkers in larger cohorts, abolishing the need for preselection of potential biomarker proteins. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=68 SRC="FIGDIR/small/486663v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@eda5d4org.highwire.dtl.DTLVardef@220b01org.highwire.dtl.DTLVardef@1008757org.highwire.dtl.DTLVardef@1b56665_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2021

Mitochondrial One-Carbon Flux has a Growth-Independent Role in Promoting Breast Cancer Metastasis

Progression of primary cancer to metastatic disease is the most common cause of death in cancer patients with minimal treatment options available. Canonical drugs target mainly the proliferative capacity of cancer cells, which often leaves slow-proliferating, persistent cancer cells unaffected. Metabolic determinants that contribute to growth-independent functions supporting resistance and metastatic dissemination are still poorly understood. In the present study, we revealed that antifolate treatment results in an uncoupled and autarkic mitochondrial one-carbon (1C) metabolism allowing sustained serine catabolism and formate overflow when cytosolic 1C metabolism is impaired. Interestingly, antifolate dependent growth-arrest did not correlate with decreased migration capacity. Therefore, using the antifolate Methotrexate as a tool compound allowed us to disentangle proliferation and migration to profile the metabolic phenotype of migrating (growth-arrested) cells. Supported by an increased NAD/NADH ratio, we observed increased serine de novo synthesis and increased serine catabolism to formate. Consequently, inhibition of serine de novo synthesis using the competitive PHGDH-inhibitor BI-4916 or direct inhibition of mitochondrial 1C metabolism reduced cancer cell migration. Using an orthotopic breast cancer model, we show that sole inhibition of mitochondrial serine catabolism does not affect primary tumor growth but strongly inhibits pulmonary metastasis. We conclude that mitochondrial 1C metabolism, despite being dispensable for proliferative capacities, confers an advantage to cancer cells by supporting their motility potential. Our results improve our understanding of 1C metabolism and of metabolic determinants that support the process of cancer cell migration and metastasis.

cancer biology↗