YAP is a mechanosensitive transcriptional activator with a critical role in cancer, regeneration, and organ size control. Here, we show that force applied to the nucleus directly drives YAP nuclear translocation by decreasing the mechanical restriction of nuclear pores to molecular transport. Exposure to a stiff environment leads cells to establish a mechanical connection between the nucleus and the cytoskeleton, allowing forces exerted through focal adhesions to reach the nucleus. Force transmission then leads to nuclear flattening, which stretches nuclear pores, reduces their mechanical resistance to molecular transport, and increases YAP nuclear import. The restriction to transport is further regulated by the mechanical stability of the transported protein, which determines both active nuclear transport of YAP and passive transport of small proteins. Our results unveil a mechanosensing mechanism mediated directly by nuclear pores, demonstrated for YAP but with potential general applicability in transcriptional regulation.

Cell function depends on tissue rigidity, which cells probe by applying and transmitting forces to their extracellular matrix, and then transducing them into biochemical signals. Here we show that in response to matrix rigidity and density, force transmission and transduction are explained by the mechanical properties of the actin-talin-integrin-fibronectin clutch. We demonstrate that force transmission is regulated by a dynamic clutch mechanism, which unveils its fundamental biphasic force/rigidity relationship on talin depletion. Force transduction is triggered by talin unfolding above a stiffness threshold. Below this threshold, integrins unbind and release force before talin can unfold. Above the threshold, talin unfolds and binds to vinculin, leading to adhesion growth and YAP nuclear translocation. Matrix density, myosin contractility, integrin ligation and talin mechanical stability differently and nonlinearly regulate both force transmission and the transduction threshold. In all cases, coupling of talin unfolding dynamics to a theoretical clutch model quantitatively predicts cell response.

Biological processes in any physiological environment involve changes in cell shape, which must be accommodated by their physical envelope—the bilayer membrane. However, the fundamental biophysical principles by which the cell membrane allows for and responds to shape changes remain unclear. Here we show that the 3D remodelling of the membrane in response to a broad diversity of physiological perturbations can be explained by a purely mechanical process. This process is passive, local, almost instantaneous, before any active remodelling and generates different types of membrane invaginations that can repeatedly store and release large fractions of the cell membrane. We further demonstrate that the shape of those invaginations is determined by the minimum elastic and adhesive energy required to store both membrane area and liquid volume at the cell–substrate interface. Once formed, cells reabsorb the invaginations through an active process with duration of the order of minutes.

Plasma membrane tension regulates many key cellular processes. It is modulated by, and can modulate, membrane trafficking. However, the cellular pathway(s) involved in this interplay is poorly understood. Here we find that, among a number of endocytic processes operating simultaneously at the cell surface, a dynamin independent pathway, the CLIC/GEEC (CG) pathway, is rapidly and specifically upregulated upon a sudden reduction of tension. Moreover, inhibition (activation) of the CG pathway results in lower (higher) membrane tension. However, alteration in membrane tension does not directly modulate CG endocytosis. This requires vinculin, a mechano-transducer recruited to focal adhesion in adherent cells. Vinculin acts by controlling the levels of a key regulator of the CG pathway, GBF1, at the plasma membrane. Thus, the CG pathway directly regulates membrane tension and is in turn controlled via a mechano-chemical feedback inhibition, potentially leading to homeostatic regulation of membrane tension in adherent cells.

Pontes et al. show that plasma membrane mechanics exerts an upstream control during cell motility. Variations in plasma membrane tension orchestrate the behavior of the cell leading edge, with increase–decrease cycles in tension promoting adhesion row positioning.

clathrin-coated structures form gradually without a major structural rearrangement. Currently, the endocytosis field is literally split between these two models due to the lack of experimental and analytical approaches that allow real time detection of conformational changes in clathrin coats with high resolution. In this study, using structured illumination microscopy in the total internal reflection mode, we demonstrate that curvature generation by clathrincoated pits can be detected in real time within cultured cells and and tissues of developing fruit fly embryos. We found that the footprint of clathrin coats increase monotonically until the formation of curved pits. These results show that the proposed flat-to-curved transition is not the mechanism through which clathrin pits invaginate. On the contrary, clathrin coats gain curvature at very early stages of their formation. Therefore, curvature generation by clathrin coats does not necessitate a dynamically unstable clathrin lattice.

24Plasma membrane tension is an important factor that regulates many key 25 cellular processes. Membrane trafficking is tightly coupled to membrane tension 26 and can modulate the latter by addition or removal of the membrane. However, 27the cellular pathway(s) involved in these processes are poorly understood. Here 28 we find that, among a number of endocytic processes operating simultaneously 29 at the cell surface, a dynamin and clathrin-independent pathway, the 30 CLIC/GEEC (CG) pathway, is rapidly and specifically upregulated upon 31 reduction of tension. On the other hand, inhibition of the CG pathway results in 32 lower membrane tension, while up regulation significantly enhances membrane 33 tension. We find that vinculin, a well-studied mechanotransducer, mediates the 34 tension-dependent regulation of the CG pathway. Vinculin negatively regulates a 35 key CG pathway regulator, GBF1, at the plasma membrane in a tension 36 dependent manner. Thus, the CG pathway operates in a mechanochemical 37 feedback loop with membrane tension potentially leading to homeostatic 38 regulation of plasma membrane tension. 39