Biology subjects

Fleuriot, L.

Publications and source records attributed to Fleuriot, L..

8 recordsLinked to original sources

bioRxiv2026

Ether lipid remodeling during neuronal differentiation prevents ferroptosis

Ferroptosis is a form of cell death driven by iron-dependent lipid peroxidation, with specific lipid species playing key roles in modulating susceptibility. Among these, ether lipids have shown conflicting effects, being linked to both protection and sensitization. Here, we dissect the relationship between lipid structure and ferroptosis sensitivity and explain how ether lipids exert context-dependent effects. Ether lipids can promote ferroptosis through a metabolic bias towards the accumulation of polyunsaturated acyl chains and ethanolamine head groups, whereas this pro-ferroptotic tendency is counterbalanced by the anti-ferroptotic vinyl ether moiety introduced by plasmanylethanolamine desaturase 1. We show that this protective effect is critical for preventing ferroptosis in hiPSC-derived neurons, which accumulate otherwise pro-ferroptotic ether lipids during differentiation. This effect is not solely due to its antioxidant properties but also stems from the reprogramming of mitochondrial respiration. The lack of vinyl ether bonds leads to multiple mitochondrial defects, including increased mitochondrial reactive oxygen species (ROS), lower membrane potential, and abnormal cristae structures. These findings indicate that vinyl ether bonds in ether lipids offer dual ferroptosis resistance by scavenging ROS and minimizing its production at the mitochondrial level. The disruption of this system in Caenorhabditis elegans leads to iron-induced death and impaired motility. Thus, our study reveals ether lipid structural remodeling as a key regulator of ferroptosis sensitivity in neurons.

cell biology↗

bioRxiv2025

Chain length defines the spatial segregation and metabolic fate of fatty acids in adipocytes

Adipocytes primarily store fatty acids (FAs) as triacylglycerols (TGs) within lipid droplets, releasing them through lipolysis to meet systemic energy demands. While the metabolism of long-chain fatty acids (LCFAs) in adipocytes has been extensively characterized, it remains ill-defined how adipocytes utilize fatty acids depending on chain length and structure. Our work demonstrates that short- and medium-chain fatty acids (SMCFAs) are esterified into TGs within lipid droplets, rather than being incorporated into other FA-containing lipid species. During lipolytic activation, TGs enriched in SMCFAs are hydrolysed more rapidly than those containing LCFAs. This accelerated mobilization is facilitated by the preferential localization of SMCFA-containing TGs at the lipid droplet surface, which enhances accessibility to adipose triglyceride lipase. Unlike LCFAs, which are efficiently released for utilization by peripheral tissues, SMCFAs are predominantly oxidized within adipocytes. These findings reveal a unique metabolic routing of SMCFAs, indicating their preferential intracellular oxidation to support adipocyte energy requirements.

biochemistry↗

bioRxiv2024

Acyltransferases in the first step of glycerophospholipid synthesis have redundant and non-redundant roles in sn-1 acyl chain regulation, ether lipid levels, and cell survival

The increased use of lipidomics analyses in biomedical research made it crucial to understand correctly how lipid compositions are regulated. Lipid acyl chains are important regulators of membrane physicochemical properties, and are incorporated by various acyltransferases. The acyltransferases implicated in the first step of glycerophospholipid synthesis, the GPATs and GNPAT, have distinct localizations and substrate preferences. This suggests that they have distinct roles on lipid regulation, but a complete understanding of their redundant and non-redundant functions is missing. We report here a comprehensive analysis of cells having mutations in GPATs and GNPAT, either alone or in combinations. Our results suggest that the balance between GPATs and GNPAT affect the levels of ether lipids, together with glycerophospholipid acyl chain length and unsaturation. In addition, we found that lipid synthesis initiated at peroxisomes, but not mitochondria, is sufficient to provide the lipid synthesis flux required for normal cell growth. Our study unveils the multifaceted roles of the first step of de novo glycerophospholipid synthesis, thus leading to a better understanding of how lipidomes are shaped.

cell biology↗

bioRxiv2023

FAO-supported OxPhos leukemic stem cells are sensitive to cold.

Targeting mitochondrial oxidative phosphorylation (OxPhos) metabolism has revealed a potential weakness for leukemic stem cells (LSCs) that can be exploited for therapeutic purposes. Fatty acids oxidation (FAO) is a crucial OxPhos-fueling catabolic pathway for some AML and for chemotherapy-resistant AML cells. Here, we identified cold sensitivity at 4{degrees}C (cold killing challenge: CKC4), as a novel vulnerability that selectively kills FAO-supported OxPhos LSCs in Acute Myeloid Leukemia while sparing normal hematopoietic stem cells (HSCs). Cell death of OxPhos leukemic cells was induced by membrane permeabilization at 4{degrees}C while by sharp contrast, leukemic cells relying on glycolysis were resistant. Forcing glycolytic cells into OxPhos metabolism sensitized them to CKC4. We show using lipidomic and proteomic analyzes that OxPhos shapes the composition of the plasma membrane and introduce variation of 22 lipid subfamilies between cold-sensitive and cold-resistant cells. Cold sensitivity is a potential OxPhos biomarker. SignificanceThis study reveals that mitochondrial energetics fueled by FAO metabolism introduces membrane fragility upon cold exposure in OxPhos-driven AMLs and in LSCs. This novel physical property of Leukemic cells and LSCs opens new avenues for biomarker and diagnostics as well as for anti-OxPhos drug screening and LSCs targeting. One Sentence SummaryOxPhos leukemic cells die at 4{degrees}C

cancer biology↗

bioRxiv2022

VAP-A intrinsically disordered regions enable versatile tethering at membrane contact sites

Membrane contact sites (MCSs) between organelles are heterogeneous in shape, composition and dynamics. Despite this diversity, VAP proteins act as receptors for multiple FFAT motif-containing proteins and drive the formation of most MCSs involving the endoplasmic reticulum (ER). Although the VAP-FFAT interaction is well characterized, no model explains how VAP adapts to its partners in various MCSs. We report here that VAP-A localization to different MCSs depends on its intrinsically disordered regions (IDRs). We show that VAP-A interaction with PTPIP51 and VPS13A at ER-mitochondria MCS conditions mitochondria fusion by promoting lipid transfer and cardiolipin buildup. VAP-A also enables lipid exchange at ER-Golgi MCS by interacting with OSBP and CERT. However, removing IDRs from VAP-A restricts its distribution and function to ER- mitochondria MCS, at the expense of ER-Golgi MCS. Our data suggest that IDRs of VAP-A do not modulate its preference towards specific partners, but adjust its geometry to the constraints linked to different MCS organization and lifetime. Thus, VAP-A conformational flexibility mediated by its IDRs ensures membrane tethering plasticity and efficiency.

cell biology↗

bioRxiv2021

OSBP-mediated cholesterol transfer determines epithelial polarity and associated cargo secretion

Golgi lipid environment regulates sorting and cargo secretion. However, the mechanisms that spatiotemporally control the lipid composition of the secretory membranes to drive cargo trafficking are poorly understood. Lipid transfer proteins regulate the concentration of specific lipids at membrane contact sites. We hypothesised that by catalysing cholesterol/PI(4)P exchange at ER-trans-Golgi membrane contact sites the lipid transfer protein oxysterol binding protein (OSBP) affects the secretion of a subset of cargoes. Here, we report that OSBP is a major epithelial protein as its inhibition leads to complete loss of apico-basal polarity. By mapping the OSBP proximity proteome with the biotin ligase TurboID, we found that OSBP controls the secretion of multiple membrane associated proteins, including key polarity determinants such as E-cadherin. Mechanistically, we established that OSBP contributes to E-cadherin secretion by supplying cholesterol to post-Golgi membranes. Importantly, when cells downregulate cell-cell junctions upon epithelial-to-mesenchymal transition, they re-wire their lipid homeostasis and downregulate OSBP as well, thus altering the trafficking of the OSBP-dependent secretory cargoes.

cell biology↗

bioRxiv2019

Molecular and cellular dissection of the OSBP cycle through a fluorescent inhibitor

ORPphilins, natural molecules that strongly and selectively inhibit the growth of some cancer cell lines, are proposed to target intracellular lipid-transfer proteins of the Oxysterol-binding protein (OSBP) family. These conserved proteins exchange key lipids, such as cholesterol and phopsphatidylinositol-4-phosphate (PI(4)P), between organelle membranes. Among ORPphilins, molecules of the schweinfurthin family interfere with intracellular lipid distribution and metabolism, but their functioning at the molecular level is poorly understood. We report here that cell line sensitivity to schweinfurthin G (SWG) is inversely proportional to cellular level of OSBP. By taking advantage of the intrinsic fluorescence of SWG, we follow its fate in cell cultures and show that its incorporation at the TGN depends on OSBP cellular abundance. We report that SWG inhibits specifically the lipid exchange cycle of OSBP. As a consequence, post-Golgi trafficking, membrane cholesterol levels and PI(4)P turnover are affected. Finally, we demonstrate the direct binding of SWG into OSBP lipid-binding cavity by intermolecular FRET. Collectively these data describe for the first time a specific and intrinsically fluorescent pharmacological tool to dissect OSBP properties at the cellular and molecular levels.

cell biology↗

bioRxiv2019

Fat food exacerbates post-prandial hypothalamic inflammation involving GFAP+ cells and microglia

In humans, obesity was associated with brain inflammation and glial cell proliferation. Studies in rodents showed that glial cell proliferation occurs within 24 hours of high-fat diet (HFD) consumption, before obesity development. This proliferation was mainly observed in the hypothalamus (HT), a crucial brain structure for controlling body weight. Therefore, we sought to characterize the post-prandial HT inflammatory response to 1-3-6 hours exposure to a standard diet and HFD. HFD exposure increased gene expression of astrocyte and microglial marker (GFAP and Iba1) compare to standard treated mice and induced morphological modifications of microglial cells in HT. This remodeling was associated with higher expression of inflammatory genes and differential activation of hypothalamic neuropeptides involved in energy balance regulation. DREADD and PLX5622 technologies, used to modulate GFAP-positive or microglial cells activity respectively, showed that both glial cell types are involved in hypothalamic post-prandial inflammation, but in a different time frame and with a diet specificity Thus, an exacerbated post-prandial inflammation in brain might predispose individuals to obesity and needs to be characterized to address this worldwide crisis.

neuroscience↗