Biology subjects

Ledoux, B.

Publications and source records attributed to Ledoux, B..

5 recordsLinked to original sources

bioRxiv2026

Growth bistability in small bacterial populations exposed to antibiotics

With the development of microfluidics, it has now become possible to assess the susceptibility of bacteria to antibiotics at the single-cell level instead of relying on population measurements. Such studies are particularly relevant when the growth of bacterial population in the presence of antibiotics is heterogeneous. Here, we build a model to describe such a case, and apply it to experimental measurements on a small population of E. Coli exposed to ciprofloxacin, a drug which is well known for triggering a bistable response.

biophysics↗

bioRxiv2026

Compositional memory matters for early molecular systems

The error catastrophe refers to the proliferation of non-functional molecules in conditions where molecular replication has low accuracy, which is likely to correspond to conditions present at the Origin of Life. This error catastrophe can be avoided thanks to transient compartmentalization, provided that the compartments are sufficiently tight to prevent molecular leakage. Typically, transient compartmentalization models assume that the content of the compartments is completely pooled periodically, resulting in the complete loss of the compositional memory of the compartment. Furthermore, previous models that include the possibility of ecological interactions between molecular parasites and replicators within compartments generally do not study the effect of transient compartmentalization on their coevolution. To address both issues, we develop a framework that accounts for the coevolution of molecular replicators and parasites, along with specific compartmentalization dynamics that are transient yet partial, allowing compositional memory to accumulate from one round of compartmentalization to the next. We benchmark our model with a serial dilution experiment that displays complex oscillatory dynamics among four well-characterized RNA replicators. We also perform experiments to quantify the level of mixing in compartments when stronger stirring tends to homogenize their composition. We then model stirring-induced mixing and show how stirring alters the dynamics of compartmentalized replicators. We conclude that compositional memory arising from transient compartmentalization plays a major role in the dynamics of early molecular systems.

biophysics↗

bioRxiv2024

Clathrin-independent endocytosis and retrograde transport in cancer cells promote cytotoxic CD8 T cell activation

Endophilin A3-mediated clathrin-independent endocytosis (EndoA3-mediated CIE) contributes to the internalization of immunoglobulin-like proteins, including key immune synapse components. Here, we identify ICAM1 as a novel EndoA3-dependent cargo, alongside ALCAM. We demonstrate that both proteins subsequently follow retromer-dependent retrograde transport to the trans-Golgi network (TGN) in cancer cells. From there, we propose that they undergo polarized redistribution to the plasma membrane, where they contribute to immune synapse formation between cancer cells and cytotoxic CD8 T cells. Disruption of EndoA3 or retromer components significantly affects the response of autologous cytotoxic CD8 T cells, as evidenced by reduced cytokine production and secretion, but increased lytic activity, while proliferation and later activation marker expression remain intact. This is accompanied by diminished ICAM1 density at the immune synapse, where we observe it arriving via polarized vesicular transport, indicating altered synapse organization. Indeed, cancer cells lacking EndoA3-mediated CIE or retromer form enlarged immune synapses that fail to sustain full T cell cytokine secretion, suggesting a compensatory attempt by T cells to overcome the defective synapse, while likely promoting more transient contacts that potentially favor serial killing. Together, these findings reveal that EndoA3-mediated CIE and retrograde transport act in concert in cancer cells to relocate immune synapse components via the Golgi, thereby fine-tuning the balance between cytotoxic T cell cytokine secretion and lytic activity. These insights contribute to a better understanding of the mechanisms governing immune synapse formation and organization, providing a necessary foundation for the long-term identification of new strategies to enhance T cell-mediated anti-tumor immunity. Significance StatementThis study uncovers a novel mechanism by which clathrin-independent endocytosis (CIE) and retrograde transport collaborate to regulate immune synapse dynamics in cancer cells. We identify ICAM1 as a new cargo of Endophilin A3-mediated CIE, highlighting its role in the polarized redistribution of immune synapse components critical for cytotoxic CD8 T cell activation. By linking a specific CIE mechanism and retrograde transport to immune synapse function, our findings provide new insights into cancer-immunity interactions and suggest potential therapeutic strategies to enhance immune responses by targeting protein trafficking pathways.

cell biology↗

bioRxiv2024

In-depth study of MPV17: a molecular travel unveiling a mitochondrial calcium regulation function

Mitochondrial DNA depletion syndromes are severe genetic disorders associated with mutations in a variety of genes including MPV17, encoding a protein of the inner mitochondrial membrane with an unclear function. In this study, using BioID technology, we identified MPV17 interacting partners among which proteins from the MICOS complex. However, MPV17 knockout did not impact mitochondrial ultrastructure, but led to increased mitochondria-derived vesicles formation and altered mitochondrial permeability transition pore. Furthermore, MPV17 KO cells exhibited higher mitochondrial calcium levels and reactive oxygen species, leading to mtDNA degradation, a phenomenon prevented by blocking mitochondrial calcium entry or treating cells with antioxidant. We thus propose a function for MPV17 as a potential additional member of the mitochondrial permeability transition pore, whereas in the absence of the protein, the build-up of calcium inside the mitochondria would lead to mtDNA degradation caused by increased oxidative damages.

cell biology↗

bioRxiv2022

Plasma membrane nanodeformations promote actin polymerisation through CIP4/CDC42 recruitment and regulate type II IFN signaling

In their environment, cells have to cope with mechanical stresses constantly. Among those, nanoscale deformations of plasma membrane induced by substrate nanotopography are now largely accepted as a biophysical stimulus influencing cell behaviour and function. However, the mechanotransduction cascades involved and their precise molecular effects on cellular physiology are still poorly understood. Here, using homemade fluorescent nanostructured cell culture surfaces, we explored the role of Bin/Amphiphysin/Rvs (BAR) domain proteins as mechanosensors of plasma membrane geometry. Our data reveal that distinct subsets of BAR proteins bind to plasma membrane deformations in a membrane curvature radius-dependent manner. Furthermore, we show that membrane curvature promotes the formation of dynamic actin structures mediated by the Rho GTPase CDC42, the F-BAR protein CIP4 and the presence of PI(4,5)P2, independently of clathrin. In addition, these actin-enriched nanodomains can serve as platforms to regulate receptor signaling as they appear to contain Interferon {gamma} receptor (IFN{gamma}-R) and to lead to the partial inhibition of IFN{gamma}-induced Janus-activated tyrosine kinase/signal transducer and activator of transcription (JAK/STAT) signaling.

cell biology↗