Biology subjects

Strale, P.-O.

Publications and source records attributed to Strale, P.-O..

4 recordsLinked to original sources

bioRxiv2024

Dissecting the binding mechanisms of synaptic membrane adhesion complexes using a micropattern based cellular model

The formation of adhesive cell-cell contacts is based on the intrinsic binding properties between specific transmembrane ligand-receptor pairs. In neurons, synaptic adhesion molecules provide a physical linkage between pre- and post-synaptic compartments, but the strength and the dynamic of these complexes in their actual membrane environments remain essentially unknown. To access such information, we developed a versatile assay to measure the affinity and binding kinetics of synaptic ligand-receptor interactions, based on the immobilization of Fc-tagged ligands on micropatterned substrates combined with live imaging of fluorescently-tagged counter receptors in heterologous cells. We applied this strategy to study the heterophilic complex formed between neurexin-1{beta} (Nrx1{beta}) and neuroligin-1 (Nlg1), compared to the homophilic SynCAM1 complex. First, the control of ligand density combined to the measurement of steady-state receptor enrichment at micropatterns demonstrates the high specificity of the matching molecular interactions and allows for the quantification of the two-dimensional affinity of the interaction in a membrane environment. Second, long-term FRAP experiments performed on the two molecular complexes and fitted with analytical models, demonstrate a diffusion-limited regime for SynCAM1 and a reaction-limited regime for Nlg1. This analysis provides a very long bond lifetime of the Nrx1{beta}-Nlg1 complex, which by comparison with a monomeric mutant of Nlg1, can be attributed to the constitutive dimerization of Nlg1. Finally, we used the stable Nrx1{beta}-Nlg1 complex as a pseudo-synaptic platform to analyze the rapid binding kinetics between the scaffolding protein PSD-95 and the intracellular domain of Nlg1, dissecting the contribution of the different PDZ domains through the use of specific PSD-95 point mutants.

neuroscience↗

bioRxiv2019

Different integrins mediate haptotaxis of T lymphocytes towards either lower or higher adhesion zones

Guidance of cells by molecules anchored on a substrate, known as haptotaxis, is arguably crucial in development, immunology and cancer, however the exact cues and mechanisms driving cell orientation in vivo are hardly identified. Adhesive haptotaxis has been described in the case of mesenchymatous cells that develop strong pulling forces with their substrates and orient via a tug of war mechanism - a competition between cells pulling edges. In the case of amoeboid cells that migrate with minimal interaction with their substrate, existence of adhesive haptotaxis remains unclear. Here, we studied the crawling of human T lymphocytes on substrates with spatially modulated adhesivity, and observed haptotaxis with surface concentrations of integrin ligands found on high endothelial veinules. Overexpression of ICAM-1 and VCAM-1 molecules observed in vivo at transmigration portals can therefore promote leukocyte recruitment. Mechanistically, we show that integrin-mediated haptotaxis of lymphocytes differ both from active chemotaxis, because no mechanotransduction was detected, and from the passive tug of war mechanism of mesenchymatous cells, because different integrins support opposite phenotypes. Cells favored more adherent zones with VLA-4 and, counterintuitively, less adherent zones with LFA-1. These results reveal that integrins control differential adhesive haptotaxis behaviors without mechanotransduction, and this smart capability may support unsuspected ways for cells path selection.

biophysics↗

bioRxiv2018

A generic widefield topographical and chemical photopatterning method for hydrogels.

3D cell culture aims at reconciliating the simplicity of in vitro models with the human like properties encountered in vivo. Soft permeable hydrogels have emerged as user-friendly materials to grow cells in more physiological conditions. With the intent on turning these homogeneous substrates into biomimetic templates, we introduce a generic solution compatible with the most biologically relevant and often frail materials. Here we take control of the chemical environment driving generic radical reactions to craft common gels with patterned light. In a simple microreactor, we harness the well-known inhibition of radicals by oxygen to enable topographical photopolymerization. Strikingly, by sustaining an oxygen rich environment, we can also induce hydrogel photo-scission which turns out to be a powerful and generic subtractive manufacturing method. We finally introduce a flexible patterned functionalization protocol based on available photo-linkers. Using these common tools on the most popular hydrogels, we tailored soft templates where cells grow or self-organize into standardized structures. The platform we describe has the potential to set a standard in future 3D cell culture experiments.

bioengineering↗

bioRxiv2017

Force-Dependent Binding Of Vinculin To α-Catenin Regulates Cell-Cell Contacts Stability And Collective Cell Behavior

The shaping of a multicellular body and repair of adult tissues require fine-tuning of cell adhesion, cell mechanics and intercellular transmission of mechanical load. Adherens junctions (AJs) are the major intercellular junctions by which cells sense and exert mechanical force on each other. However, how AJs adapt to mechanical stress and how this adaptation contributes to cell-cell cohesion and eventually to tissue-scale dynamics and mechanics remains largely unknown. Here, by analyzing the tension-dependent recruitment of vinculin, -catenin and F-actin as a function of stiffness, as well as the dynamics of GFP-tagged wild-type and mutated -catenins, altered for their binding capability to vinculin, we demonstrate that the force-dependent binding of vinculin stabilizes -catenin and is responsible for AJ adaptation to force. Challenging cadherin complexes mechanical coupling with magnetic tweezers, and cell-cell cohesion during collective cell movements, further highlight that tension-dependent adaptation of AJs regulates cell-cell contact dynamics and coordinated collective cell migration. Altogether, these data demonstrate that the force-dependent -catenin/vinculin interaction, manipulated here by mutagenesis and mechanical control, is a core regulator of AJ mechanics and long-range cell-cell interactions.\n\nSummary statementCombining cell biology and biomechanical analysis, we show here that the coupling between cadherin complexes and actin trough tension-dependent -catenin/vinculin association is regulating AJ stability and dynamics as well as tissue-scale mechanics.

cell biology↗