28.6:
Cell-matrix’s Response to Mechanical Forces
Cell-matrix junctions such as focal adhesions are directly connected to a network of contractile proteins such as actin and myosin.
When mechanical forces pull the junctions away from a rigid extracellular matrix, the cell forms additional focal adhesions to withstand the tension.
A softer ECM generates less resistance, allowing the cell to respond according to the stiffness of ECMs in different tissues.
Such mechanosensing depends on junctional proteins such as talin and fibronectin that change their conformation when the junction is stretched.
As actin filaments get pulled by myosin, talin unfolds, exposing vinculin-binding sites. Vinculin recruits additional actin filaments to strengthen the junction.
On the ECM face, tension applied across the length of fibronectin during fibril matrix assembly exposes hidden binding sites for collagen.
Collagen binding reinforces the junction allowing cells to respond to mechanical forces from their environments.
28.6:
Cell-matrix’s Response to Mechanical Forces
In animal cells, the extracellular matrix allows cells within tissues to withstand external stresses and transmits signals from the outside of the cell to the inside. The extracellular matrix is extensive, and its composition varies between different types of tissues. For example, the reticular fibers and ground substance make up the ECM in loose connective tissue, while collagen and bone minerals make up the ECM of bone tissue.
Anchoring junctions mechanically attach a cell to the extracellular matrix or other cells. A cluster of anchoring junctions forms macromolecular complexes called focal adhesions or FAs. FAs regulate cell adhesion and mechanotransduction, which is the conversion of mechanical signals to chemical signals in the cell. FAs commonly occur on the lateral and basal surfaces of cells, providing strong and flexible connections. They were first recognized using an antitumor serum in Rous sarcoma virus-transformed rat kidney cells. Three proteins, talin, vinculin, and tensin, and their isoforms, link integrins to the cytoskeleton, thus strengthening the junction. Tension-dependent conformational changes activate talin and vinculin, thus suggesting their involvement in mechanosensing signals from their environment.
Adapted from section 4.2 Epithelial tissue- Anatomy and Physiology 2 e, Openstax
Suggested Reading
- Liu Z, Tan JL, Cohen DM, Yang MT, Sniadecki NJ, Ruiz SA, Nelson CM, Chen CS. Mechanical tugging force regulates the size of cell-cell junctions. Proceedings of the National Academy of Sciences. 2010 Jun 1;107(22):9944-9.
- David G. Menter, Raymond N. DuBois, "Prostaglandins in Cancer Cell Adhesion, Migration, and Invasion," International Journal of Cell Biology, vol. 2012, Article ID 723419, 21 pages, 2012. https://doi.org/10.1155/2012/723419
- Angulo-Urarte, A., van der Wal, T., & Huveneers, S. (2020). Cell-cell junctions as sensors and transducers of mechanical forces. Biochimica et Biophysica Acta (BBA)-Biomembranes, 1862(9), 183316.