ATRA mechanically reprograms pancreatic stellate cells to suppress matrix remodelling and inhibit cancer cell invasion.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a dismal survival rate. Persistent activation of pancreatic stellate cells (PSCs) can perturb the biomechanical homoeostasis of the tumour microenvironment to favour cancer cell invasion. Here we report that ATRA, an active metabolite of vitamin A, restores mechanical quiescence in PSCs via a mechanism involving a retinoic acid receptor beta (RAR-β)-dependent downregulation of actomyosin (MLC-2) contractility.

Vinculin phosphorylation at residues Y100 and Y1065 is required for cellular force transmission.

The focal adhesion protein vinculin connects the actin cytoskeleton, through talin and integrins, with the extracellular matrix. Vinculin consists of a globular head and tail domain, which undergo conformational changes from a closed auto-inhibited conformation in the cytoplasm to an open conformation in focal adhesions. Src-mediated phosphorylation has been suggested to regulate this conformational switch.

Vinculin E29R mutation changes cellular mechanics.

We investigated the effect of the point mutation E29R on vinculin under cell mechanical aspects. MEFvcl KO cells were transfected with intact eGFP-vinculin (rescue) or mutant E29R vinculin. Cellular stiffness and adhesion strength of mutant E29R vinculin were considerably higher compared to rescue and MEFvcl KO cells.

Serine phosphorylation on position 1033 of vinculin impacts cellular mechanics.

This study evaluates the influence of S1033 vinculin phosphorylation on the mechanical properties of cells. We demonstrate that MEFvcl KO cells transfected with the non-phosphorylatable eGFP-vinculin mutant S1033A are of lower stiffness compared to MEFvcl Rescue and phospho-mimicking mutant S1033D cells, which were of similar stiffness. Analogous, 2D traction microscopy indicates that MEFvcl Rescue and MEF mutant S1033D cells generate similar strain energy, but mutant S1033A cells display ∼50% less strain energy.

Biomembrane-mimicking lipid bilayer system as a mechanically tunable cell substrate.

Cell behavior such as cell adhesion, spreading, and contraction critically depends on the elastic properties of the extracellular matrix. It is not known, however, how cells respond to viscoelastic or plastic material properties that more closely resemble the mechanical environment cells encounter in the body. In this report, we employ viscoelastic and plastic biomembrane-mimicking cell substrates.

CAS directly interacts with vinculin to control mechanosensing and focal adhesion dynamics.

Focal adhesions are cellular structures through which both mechanical forces and regulatory signals are transmitted. Two focal adhesion-associated proteins, Crk-associated substrate (CAS) and vinculin, were both independently shown to be crucial for the ability of cells to transmit mechanical forces and to regulate cytoskeletal tension. Here, we identify a novel, direct binding interaction between CAS and vinculin.

Influence of focal adhesion kinase on the mechanical behavior of cell populations.

Mechanical forces play an important role in the organization, growth, maturation, and function of living tissues. At the cellular level, the transmission of forces from outside the cell through cell-matrix and cell-cell contacts are believed to control spreading, motility, maturation as well as intracellular signaling cascades that may change many characteristics in cells. We looked at cell populations of mouse embryonic fibroblasts that are deficient of focal adhesion kinase (FAK) and examined their mechanical profile.

Vinculin, cell mechanics and tumour cell invasion.

The focal adhesion protein, vinculin, is important for transmitting mechanical forces and orchestrating mechanical signalling events. Deregulation of vinculin results in altered cell adhesion, contractility, motility and growth, all of which are important processes in cancer metastasis. This review summarises recent reports on the role of vinculin in cellular force generation and signalling, and discusses implications for a role of vinculin in promoting cancer cell migration in 3D environments.

Head/tail interaction of vinculin influences cell mechanical behavior.

This study evaluates the influence of vinculin in closed conformation on the mechanical properties of cells. We demonstrate that MEFvin(-/-) cells transfected with the eGFP-vinculin mutant A50I (talin-binding-deficient-vinculin in a constitutively closed conformation) show 2-fold lower stiffness and focal adhesion density compared to MEFvin(+/+) and MEF(Rescue) cells. MEF(A50I) cells are as stiff as MEFvin(-/-) cells with similar focal adhesion density.