Biology subjects

Le Saux, G.

Publications and source records attributed to Le Saux, G..

5 recordsLinked to original sources

bioRxiv2025

Heterogeneity in environmental stiffness alone can guide cells and shape tissues

While topographical and chemical cues are well known to regulate cell shape and function, the role of stiffness heterogeneity has remained unclear. Here, we demonstrate - for the first time to our knowledge - that cells can be guided solely by the stiffness heterogeneity of their environment. To that end, we engineered a cell-guiding platform with abrupt, subcellular stiff and soft domains, whose flatness and uniform chemistry eliminated confounding cues. Cells elongate and align along stiff regions, sensing soft domains as barriers when wider than 2 microns. Perturbated myosin activity, cortical tension, and elasticity contrast reveal distinct biomechanical contributions, while a probabilistic model integrating adhesion, contractility, and cortical tension extracts key mechanical parameters characterizing the cellular state. Finally, experiments and dissipative particle dynamics demonstrate collective stiffness-based contact guidance. This work identifies stiffness heterogeneity as a fundamental regulator of cell and tissue organization and provides a framework for designing mechanoregulatory biomaterials.

biophysics↗

bioRxiv2024

Deciphering the role of the nanoscale clustering of activating and costimulatory antibodies on T cell activation

In a joint experimental and a modeling effort, we explored the regulation of T cell activation and cytotoxicity by the nanoscale clustering and surface density of activating and costimulatory antibodies. Specifically, we simulated T cells on nanolithographically patterned arrays of clusters of these antibodies, systematically varying the cluster size from intermediate to large and overall antibody density. We found that T-cell activation correlated more with global antibody density than with cluster size, such that at low density arrays were inefficient in activation, while high density arrays saturated the signal. However, when T-cells were exposed to patterns of low global densities but small, very dense clusters, full activation of T cells was achieved. These results could be rationalized using the membrane-fluctuation-model that integrates the cooperative effects between bonds with mechanical feedback from the cell activation. This insight into the spatial organization of activating ligands provides an important understanding of the mechanism of T cell activation and allows for the design of more effective T cell activation platforms for immunotherapy.

immunology↗

bioRxiv2024

Effect of the Environmental Mechanical Heterogeneity on T Cell Function

T cells, key players in the immune system, recognize antigens via T-cell receptors (TCRs) and require additional costimulatory and cytokine signals for full activation. Beyond biochemical signals, T cells also respond to mechanical cues such as tissue stiffness. Traditional ex-vivo mechanostimulating platforms, however, present a uniform mechanical environment, unlike the heterogeneous conditions T cells encounter in-vivo. This work introduces a novel mechanically heterogeneous environment, with alternating soft and stiff microdomains, to mimic the complex mechanical signals T cells face. Results show that T cells exposed to this heterogeneous environment do not average the mechanical signals but instead respond similarly to those on a homogeneously soft surface, leading to lower activation compared to those on a stiff surface. Interestingly, long-term exposure to these patterns enhances the proliferation of central memory and effector T cell phenotypes, similar to stiff environments. These findings reveal the non-linear nature of T cell mechanosensing and suggest that mechanical heterogeneity plays a critical role in modulating T cell responses, providing new insights into T cell activation and potential implications for immunotherapies.

immunology↗

bioRxiv2020

Molecular Scale Spatio-Chemical Control of the Activating-Inhibitory Signal Integration in NK Cells

The role of the spatial juxtaposition between activating and inhibitory receptors in cytotoxic lymphocytes has been strongly debated in the context of the inhibition of immune signaling. The challenge in addressing this problem was so far a lack of experimental tools which can simultaneously manipulate different signaling molecules. Here, we circumvent this challenge by introducing a nanoengineered multifunctional cell niche, in which activating and inhibitory ligands are positioned with molecular-scale variability and control, and applied it to elucidate the role of the spatial juxtaposition between ligands for NKG2D and KIR2DL1 - activating and inhibitory receptors in Natural Killer (NK) cells - in KIR2DL1-mediated inhibition of NKG2D signaling. We realized the niche by a nanopatterning of nanodots of different metals with molecular scale registry in one lithographic step, followed by a novel ternary functionalization of the fabricated bi-metallic pattern and its background to with three distinct biochemical moieties. We found, that within the probed range, the 40 nm gap between the activating and inhibitory ligands provided an optimal inhibition condition. Supported by theoretical modeling and simulations we interpret these findings as a consequence of the size and conformational flexibility of the ligands in their spatial interaction. Our findings provide an important insight onto the spatial mechanism of the inhibitory immune checkpoints, whose understanding is both fundamentally important, and essential for the rational design of future immunotherapies. Furthermore, our approach is highly versatile and paves the way to numerous complex molecular platforms aimed at revealing molecular mechanisms through which receptors integrate their signals.

immunology↗

bioRxiv2020

Mechanical Regulation of the Cytotoxic Activity of Natural Killer Cells

Mechanosensing has been recently explored for T cells and B cells and is believed to be part of their activation mechanism. Here, we explore the mechanosensing of the third type of lymphocytes - Natural Killer (NK) cells, by showing that they modulate their immune activity in response to changes in the stiffness of a stimulating surface. Interestingly, we found that this immune response is bell-shaped, and peaks for a stiffness of a few hundreds of kPa. This bell-shape behavior was observed only for surfaces functionalized with the activating ligand MHC class I polypeptide-related sequence A (MICA), but not for control surfaces lacking immunoactive functionalities. We found that stiffness does not affect uniformly all cells but increases the size of a little group of extra-active cells, which in turn contribute to the overall activation effect of the entire cell population. We further imaged the clustering of costimulatory adapter protein DAP10 on NK cell membrane and found that it shows the same bell -shape dependence to surface stiffness. Based on these findings, we propose a catch-bond-based model for the mechanoregulation of NK cell cytotoxic activity, through interaction of NKG2D activating receptors with MICA. Our findings reveal what seems to be "the tip of iceberg" of mechanosensation of NK cells, and provides an important insight on the mechanism of their immune signaling. Statement of SignificanceThe mechanical sensing of immune lymphocytes was recently demonstrated for T cells and B cells, but not for the third type of lymphocytes - Natural Killer (NK) cells. Interestingly, previous reports on lymphocyte mechanosensing were controversial, and showed either positive or negative changes in their immune activity with environmental stiffness, depending on the stiffness range. In this paper, we directly demonstrated that NK cells modulate their response with the stiffness of the stimulating surface, and this modulation has a bell-shape trend. We found that there is a strong correlation between the response to stiffness and clustering of adaptor proteins. Upon this correlation, we proposed a mechanosensing model based on the catch-bond nature of activating ligand-receptor complexes in NK cells.

immunology↗