Publications

Cells are subjected to multiple mechanical inputs throughout their lives. Their ability to detect these environmental cues is called mechanosensing, a process in which integrins play an important role. During cellular mechanosensing, plasma membrane (PM) tension is adjusted to mechanical stress through the buffering action of caveolae; however, little is known about the role of caveolae in early integrin mechanosensing regulation. Here, we show that Cav1KO fibroblasts increase adhesion to FN-coated beads when pulled with magnetic tweezers, as compared to wild type fibroblasts. This phenotype is Rho-independent and mainly derived from increased active b1-integrin content on the surface of Cav1KO fibroblasts. FRAP analysis and endocytosis/recycling assays revealed that active b1-integrin is mostly endocytosed through the CLIC/GEEC pathway and is more rapidly recycled to the PM in Cav1KO fibroblasts, in a Rab4 and PM tension-dependent manner. Moreover, the threshold for PM tension-driven b1-integrin activation is lower in Cav1KO MEFs than in wild type MEFs, through a mechanism dependent on talin activity. Our findings suggest that caveolae couple mechanical stress to integrin cycling and activation, thereby regulating the early steps of the cellular mechanosensing response.© 2022, Lolo et al.

JTD Keywords: adhesion, alpha-v-beta-3, cell, integrin activation, internalization, kinase, mechanosensing, mediated endocytosis, mouse, stiffness, talin, trafficking, Animals, Caveolae, Cell adhesion, Cell biology, Fibroblasts, Integrin activation, Integrin beta1, Integrin recycling, Integrins, Mechanosensing, Membrane tension, Mice, Mouse, Stress, mechanical

Cell response to force regulates essential processes in health and disease. However, the fundamental mechanical variables that cells sense and respond to remain unclear. Here we show that the rate of force application (loading rate) drives mechanosensing, as predicted by a molecular clutch model. By applying dynamic force regimes to cells through substrate stretching, optical tweezers, and atomic force microscopy, we find that increasing loading rates trigger talin-dependent mechanosensing, leading to adhesion growth and reinforcement, and YAP nuclear localization. However, above a given threshold the actin cytoskeleton softens, decreasing loading rates and preventing reinforcement. By stretching rat lungs in vivo, we show that a similar phenomenon may occur. Our results show that cell sensing of external forces and of passive mechanical parameters (like tissue stiffness) can be understood through the same mechanisms, driven by the properties under force of the mechanosensing molecules involved. Cells sense mechanical forces from their environment, but the precise mechanical variable sensed by cells is unclear. Here, the authors show that cells can sense the rate of force application, known as the loading rate, with effects on YAP nuclear localization and cytoskeletal stiffness remodelling.

JTD Keywords: Actin cytoskeleton, Actin filament, Actin-filament, Adhesion, Animal, Animals, Atomic force microscopy, Breathing, Cell, Cell adhesion, Cell culture, Cell nucleus, Cells, cultured, Cytoplasm, Extracellular-matrix, Fibroblast, Fibroblasts, Fibronectin, Frequency, Gene knockdown, Gene knockdown techniques, Genetics, Germfree animal, Integrin, Intracellular signaling peptides and proteins, Knockout mouse, Lung, Male, Mechanotransduction, Mechanotransduction, cellular, Metabolism, Mice, Mice, knockout, Microscopy, atomic force, Mouse, Optical tweezers, Paxillin, Physiology, Primary cell culture, Pxn protein, mouse, Rat, Rats, Rats, sprague-dawley, Respiration, Signal peptide, Softening, Specific pathogen-free organisms, Sprague dawley rat, Stress, Substrate, Substrate rigidity, Talin, Talin protein, mouse, Tln2 protein, mouse, Traction, Transmission, Ultrastructure, Yap1 protein, rat