Biology subjects

Lebeau, J.

Publications and source records attributed to Lebeau, J..

7 recordsLinked to original sources

bioRxiv2024

G-quadruplex ligand RHPS4 compromises cellular radio-resistance by blocking the increase in mitochondrial mass and activity induced by ionising irradiation.

A major challenge in radiotherapy is to enhance tumor cell sensitivity to radiation while minimizing damage to healthy tissues. Ionising radiation (IR) induces mitochondrial DNA (mtDNA) alterations that can impair mitochondrial function and cell survival. Since mitochondria play a key role in tumor cell proliferation, they represent a promising therapeutic target for cancer treatment. In this study, we characterized the impact of different IR sources on mitochondrial function in radioresistant cancer cells. Our findings revealed several adaptive responses that may contribute to radioresistance, including increased mtDNA content, mitochondrial mass, enhanced activity, and hyperfusion of the mitochondrial network. Notably, the use of mitochondrial-targeted G-quadruplex (G4) ligands, which block mtDNA replication and transcription, disrupted these responses, reducing cancer cell survival in an mtDNA-dependent manner. These results demonstrate that mitochondrial adaptations contribute to radioresistance and highlight mitochondria as a novel target for the radiosensitizing effects of G4-ligands, extending their potential beyond telomere destabilization.

cell biology↗

bioRxiv2022

Loss of CD24 promotes radiation- and chemo-resistance by inducing stemness properties associated with a hybrid E/M state in breast cancer cells

There is compelling evidence that cancer stem cells (CSCs) play an essential role in failure of conventional antitumor therapy. In breast cancer, CD24-/low/CD44+ phenotype as well as a high aldehyde dehydrogenase activity (ALDH+) are widely associated with CSC subtypes. Furthermore, CD24-/low/CD44+ pattern is also characteristic of the mesenchymal cells generated by an epithelial-mesenchymal transition (EMT). CD24 is a surface marker expressed in many tumor types, however, its biological functions and role in cancer progression and treatment resistance remain poorly documented. We have previously shown that loss of CD24 expression in breast cancer cells is associated with radiation resistance, in relationship with the control of oxidative stress. Because ROS are known to mediate the effects of anticancer drugs as well as ionizing radiation, we investigated if CD24 could be defined as an actor of both radiation- and chemo-resistance of breast cancer cells. Using the HMLE breast cancer cell model, we observed that loss of CD24 expression induces stemness properties associated with the acquisition of a hybrid E/M phenotype. The CD24-/low cells were intrinsically more resistant than CD24+ cells. The resistance was linked to a lower level of ROS, and CD24 controlled ROS levels through the regulation of mitochondrial functions independently of antioxidant activity. Together, these results suggest a key role of CD24 in de-differentiation process of breast cancer cells, promoting acquisition of therapeutic resistance properties.

cancer biology↗

bioRxiv2022

PERK Signaling Promotes Mitochondrial Elongation By Remodeling Membrane Phosphatidic Acid

Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are linked in the onset and pathogenesis of numerous diseases. This has led to considerable interest in defining the mechanisms responsible for regulating mitochondria during ER stress. The PERK signaling arm of the unfolded protein response (UPR) has emerged as a prominent ER stress-responsive signaling pathway that regulates diverse aspects of mitochondrial biology. Here, we show that PERK activity also promotes adaptive remodeling of mitochondrial membrane phosphatidic acid (PA) to induce protective mitochondrial elongation during ER stress. We find that PERK activity is required for ER stress-dependent increases in both cellular PA and YME1L-dependent degradation of the intramitochondrial PA transporter PRELID1. Together, these processes lead to the accumulation of PA on the outer mitochondrial membrane where it induces mitochondrial elongation by inhibiting mitochondrial fission. Our results establish a new role for PERK in the adaptive remodeling of mitochondrial phospholipids and demonstrate that PERK-dependent PA regulation functions to adapt organellar shape in response to ER stress.

cell biology↗

bioRxiv2020

Two-stage Dynamic Deregulation of Metabolism Improves Process Robustness & Scalability in Engineered E. coli.

We report improved strain and bioprocess robustness as a result of the dynamic deregulation of central metabolism using two-stage dynamic control. Dynamic control is implemented using combinations of CRISPR interference and controlled proteolysis to reduce levels of central metabolic enzymes in the context of a standardized two-stage bioprocesses. Reducing the levels of key enzymes alters metabolite pools resulting in deregulation of the metabolic network. The deregulated network is more robust to environmental conditions improving process robustness, which in turn leads to predictable scalability from high throughput small scale screens to fully instrumented bioreactors as well as to pilot scale production. Additionally, as these two-stage bioprocesses are standardized, a need for traditional process optimization is minimized. Predictive high throughput approaches that translate to larger scales are critical for metabolic engineering programs to truly take advantage of the rapidly increasing throughput and decreasing costs of synthetic biology. In this work we demonstrate that the improved robustness of E. coli strains engineered for the improved scalability of the important industrial chemicals alanine, citramalate and xylitol, from microtiter plates to pilot reactors.

synthetic biology↗

bioRxiv2020

The E. coli Cas1/2 endonuclease complex reduces CRISPR/Cascade guide array stability

CRISPR based interference has become common in various applications from genetic circuits to dynamic metabolic control. In E. coli the native CRISPR Cascade system can be utilized for silencing by deletion of the cas3 nuclease along with expression of guide RNA arrays, where multiple genes can be silenced from a single transcript. We notice the loss of protospacer sequences from guide arrays utilized for dynamic silencing. We report that unstable guide arrays are due to expression of the Cas1/2 endonuclease complex. A cas1 deletion improves guide array stability. We propose a model wherein basal Cas1/2 endonuclease activity results in the loss of protospacers from guide arrays. Subsequently, mutant guide arrays can be amplified through selection. Replacing a constitutive promoter driving Cascade complex expression with a tightly controlled inducible promoter improves guide array stability, while minimizing leaky gene silencing. HighlightsO_LICas1/2 endonuclease complex mediates CRISPR/Cascade protospacer loss in E. coli C_LIO_LITightly controlled Cascade operon expression increases guide array stability. C_LI

synthetic biology↗

bioRxiv2020

Dynamic control over feedback regulation improves stationary phase fluxes in engineered E. coli.

We demonstrate the use of two-stage dynamic metabolic control to manipulate feedback regulation in central metabolism and improve stationary phase biosynthesis in engineered E. coli. Specifically, we report the impact of dynamic control over two enzymes: citrate synthase, and glucose-6-phosphate dehydrogenase, on stationary phase fluxes. Firstly, reduced citrate synthase levels lead to a reduction in -ketoglutarate, which is an inhibitor of sugar transport, resulting in increased stationary phase glucose uptake and glycolytic fluxes. Reduced glucose-6-phosphate dehydrogenase activity activates the SoxRS regulon and expression of pyruvate-ferredoxin oxidoreductase, which is in turn responsible for large increases in acetyl-CoA production. The combined reduction in citrate synthase and glucose-6-phosphate dehydrogenase, leads to greatly enhanced stationary phase metabolism and the improved production of citramalic acid enabling titers of 126{+/-}7g/L. These results identify pyruvate oxidation via the pyruvate-ferredoxin oxidoreductase as a "central" metabolic pathway in stationary phase E. coli, which coupled with ferredoxin reductase comprise a pathway whose physiologic role is maintaining NADPH levels. HighlightsO_LIDynamic reduction in -keto-glutarate pools alleviate inhibition of PTS dependent transport improving stationary phase sugar uptake. C_LIO_LIDynamic reduction in glucose-6-phosphate dehydrogenase activates pyruvate flavodoxin/ferredoxin oxidoreductase and improves stationary acetyl-CoA flux. C_LIO_LIPyruvate flavodoxin/ferredoxin oxidoreductase is responsible for large stationary phase acetyl-CoA fluxes under aerobic conditions. C_LIO_LIProduction of citramalate to titers 126 {+/-} 7g/L at > 90 % of theoretical yield. C_LI

bioengineering↗

bioRxiv2020

Form, function, and divergence of a generic fin shape in small cetaceans

Tail flukes as well as the dorsal fin are the apomorphic traits of cetaceans appeared during evolutionary process of adaptation to the aquatic life. Both appendages present a generic wing-like shape associated with lift generation and low drag. Variability of the form of appendages was studied in seven species of cetaceans having different body size, external morphology, and specialization. Hydrodynamic performance of the fin cross-sections was examined with the CFD software and compared with similar engineered airfoils. Affinity of hydrodynamic design of both appendages was found in a wing-like planform and cross-sectional design optimized for lift generation. Distinctions in the planform and cross-sections were found related with the fin specialization in thrust production or swimming stability control. Cross-sectional design of the dorsal fin was found to be optimized for the narrow range of small angles of attack. Cross-sections of tail flukes were found to be more stable for higher angles of attack and had gradual stall characteristics that is associated with their propulsive efficiency as oscillating foils. The results obtained are the evidence of divergent evolutionary pathways of a generic wing-like shape of the fins of cetaceans under specific demands of thrust production and swimming stability control.

evolutionary biology↗