Biology subjects

Missirlis, D.

Publications and source records attributed to Missirlis, D..

4 recordsLinked to original sources

bioRxiv2026

Optogenetic cross-linking of the actin cytoskeleton using DARPins

Precise tools to control actin filament organization and dynamics are essential for studying how the actin cytoskeleton regulates fundamental cell processes, such as morphological changes, migration and intracellular transport. Here, we present an optogenetic system for the reversible, spatiotemporal manipulation of actin cross-linking in living cells. Our approach employs actin-binding Designed Ankyrin Repeat Proteins (DARPins) fused to the improved Light-Induced Dimer (iLID) system, enabling actin cross-linking upon light-triggered dimerization. Following validation of cross-linking of bifunctional DARPins in reconstituted networks, the iLID system was integrated to create light-controlled associations inside cells. Optogenetic DARPin dimerization is rapid, reversible, and locally inducible. Activation of the DARPin-based actin cross-linkers revealed significant inhibition of cell traction forces when triggered throughout the cell. Our findings establish a versatile tool for investigating cytoskeletal dynamics with high spatial and temporal precision, paving the way for controlled manipulation of cellular architecture and mechanics. Graphical Abstract/Table of Contents Figure O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/726659v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@c27701org.highwire.dtl.DTLVardef@112e82borg.highwire.dtl.DTLVardef@4892e4org.highwire.dtl.DTLVardef@a3d5a7_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2026

Ultrasound-cell interactions mediated by cell cortex biomechanics

Low- to moderate-intensity ultrasound (US) technologies are increasingly being used to non-invasively modulate biological function in both clinical and laboratory settings. Realizing the full potential of these approaches requires a detailed mechanistic understanding of how ultrasound interacts with living cells. Here, we developed a well-controlled experimental platform to expose adherent cells to ultrasound stimulation while monitoring cellular activation via calcium imaging. We show that cell activation is dependent on cell type and identify NIH3T3 fibroblasts as a particularly robust responder. Our findings indicate that acoustic streaming is the primary mechanism underlying ultrasound-induced activation in our in vitro experiments. Surprisingly, the investigation of calcium dynamics revealed that the observed cytoplasmic calcium elevation originates predominantly from intracellular stores rather than extracellular influx, with membrane ion channels not contributing directly to the response. Notably, the biomechanical property of the cell-cortex emerges as a critical determinant of the cells sensitivity to ultrasound. Overall, our results provide clear evidence that the underlying mechanistic response involves external and internal factors that modulate the ultrasound-cell interaction and highlight important mechanistic considerations for ultrasound-based strategies aimed at cellular stimulation.

biophysics↗

bioRxiv2026

Enzyme-functionalized microparticles to open the vitreoretinal interface

The transport of therapeutics and gene carriers to their site of action is often hindered by biological barriers, such as cell layers and basement membranes. Among these, the inner limiting membrane (ILM) represents a major barrier within the eye, separating the vitreous body from the retina. The ILM must be crossed, if for instance gene carriers are to reach retinal target cells following intravitreal administration. However, the ILM is a densely cross-linked basement membrane barrier, allowing only the smallest nanoparticles to pass. Here, we demonstrate that active micro-colloids decorated with enzymes can locally open the ILM and thereby facilitate the diffusion of passive carriers into retinal tissue. We utilize an ex vivo porcine eye model to determine the membrane permeability threshold using fluorescent nanoprobes. We further show that collagenase-decorated silica microparticles can facilitate the transport of nanoparticles, while exhibiting excellent biocompatibility with no adverse morphological or functional retinal effects over a six-week in vivo evaluation in a porcine model. Overall, our findings introduce a biocompatible and minimally invasive strategy to facilitate the targeted nanoparticle transport across biological barriers, which we demonstrate for retinal delivery enabled by active colloids.

bioengineering↗

bioRxiv2020

Substrate Resistance to Traction Forces Controls Fibroblast Polarization

The mechanics of fibronectin-rich extracellular matrix regulate cell physiology in a number of diseases, prompting efforts to elucidate cell mechanosensing mechanisms at the molecular and cellular scale. Here, the use of fibronectin-functionalized silicone elastomers that exhibit considerable frequency-dependence in viscoelastic properties unveiled the presence of two cellular processes that respond discreetly to substrate mechanical properties. Soft elastomers supported efficient focal adhesion maturation and fibroblast spreading due to an apparent stiff surface layer. However, soft elastomers did not enable cytoskeletal and fibroblast polarization; elastomers with high cross-linking and low deformability were required for polarization. The underlying reason for this behavior was the inability of soft elastomeric substrates to resist traction forces, rather than a lack of sufficient traction force generation; accordingly, mild inhibition of actomyosin contractility rescued fibroblast polarization even on the softer elastomers. Our findings help reconcile previously proposed local and global models of cell mechanosensing by demonstrating the differential dependence of substrate mechanics on distinct cellular processes. Statement of SignificanceThe mechanisms cells employ to sense and respond to the mechanical properties of their surroundings remain incompletely understood. In this study we used a commercial silicone elastomer formulation to prepare compliant, fibronectin-coated substrates and investigate the adhesion and polarization of human fibroblasts. Our results suggest the existence of at least two discrete mechanosensing processes regulated at different time and length (force) scales. Focal adhesion assembly and cell spreading were promoted by a stiff surface layer independent from bulk viscoelasticity, whereas effective cell polarization required elevated elastomer stiffness, sufficient to resist applied cell traction. The results presented here have implications on the use of elastomeric substrates as biomaterials for mechanosensing studies or clinical applications.

biophysics↗