Biophysical Society Thematic Meeting | Riga 2026

Active and Responsive Soft Matter: From Biological to Engineered Systems

Monday Speaker Abstracts

DYNAMICS OF CYTOSKELETAL FILAMENTS INSIDE CELLULAR TETHERS Sarah Keary 1 ; Antonin Marteau 1 ; Benjamin Bouchet 2 ; Anna Akhmanova 2 ; Patricia Bassereau 1 ; 1 Institut Curie, CNRS UMR168, Physics of Cells and cancer, Paris, France 2 University of Utrecht, Faculty of Science, Utrecht, The Netherlands Pulling membrane tethers from cells and measuring the associated force—e.g., using a bead trapped with optical tweezers—is a widely used method to probe plasma membrane tension. However, actin filaments can grow within these nanotubes, whereas microtubules have not been observed inside them under normal conditions. When actin filaments reach the tip of the nanotube, they change the tether force either by pushing on the bead through polymerization or by pulling due to retrograde flow in the cortex. We will discuss the parameters that govern the dynamics of the tether forces under normal conditions and upon actin depolymerization, where we evidence that microtubules can grow inside them. INTEGRIN ADHESION COMPLEXES SENSING SUBSTRATE NANO-TOPOGRAPHY Alexander D. Bershadsky 1,2 1 Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore. 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel. While role of focal adhesions in cell mechanosensitivity is well documented and intensely studied, the mechanisms of adhesion dependent topography sensing are insufficiently understood. Here we compare and contrast focal adhesions and two other major types of integrin-mediated cell-matrix adhesions – fibrillar adhesions and podosomes - and demonstrate that, unlike focal adhesions, both can recognize and selectively adhere to the matrix nano topographical features. Fibrillar adhesions are associated with cell-derived fibrils containing protein fibronectin and are required for fibrillogenesis. They rapidly align along pre-existing fibrous cell-derived matrix or electrospun nanofibers and can then template new fibronectin fibrils. Topography- induced fibrillar adhesions depend primarily on α5β1 -integrin clustering and disassemble upon excessive activation of myosin IIA or increase of membrane tension. We propose a generic theoretical model where the adhesion receptor favors the membrane and substrate planes to be tilted relative to each other. This model matches experimental observations of preferential α5β1 -integrin clustering along nanofibers and high curvature concave edges of micro-ridges. Podosomes, micron-sized dynamic adhesive membrane protrusions, also demonstrate sensitivity to myosin IIA activation and membrane tension and strong preference to the substrate features of high negative curvature. Podosome-forming cells are accumulated on substrate covered with nanopillars assembling collar adhesions consisting of 2-4 podosomes around the pillar base. Switching from podosome to focal adhesion formation by activation of Rho/ROCK/myosin IIA pathway switches cell preference from pillar-covered to flat substrate. Thus, both fibrillar adhesions and podosomes, despite compositional and structural differences, share the ability to sense substrate topography, essential for their biological functions.

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