Biomechanical properties of actin stress fibers of non-motile cells

The structure of stress fibers, contractile actin bundles, differs between motile and non-motile cells, though the same term "stress fiber" is used to refer to the structurally as well as functionally different actin bundles. Stress fibers in non-motile cells run between separate focal adhesions, producing isometric tension due to actomyosin contraction. The stress fiber contraction is maintained through dynamic molecular exchanges between preformed and cytoplasmic components. This isometric contraction has been recognized as being essential for extracellular matrix assembly and resultant wound healing. In addition, there have recently been increasing data suggesting that stress fibers under contraction by themselves work as a mechanosensitive element. In this review we discuss, from molecular and physical viewpoints, biomechanical properties of the stress fiber of non-motile cells such as contraction force, resistance to stretching, and their roles in keeping a mechanical homeostasis, which play vital roles in the mechanosensing process.