Abstract
Recently, extensive researches have reported that intracellular contractile forces play pivotal roles in cell functions, such as morphogenesis, differentiation and homeostasis. Actin stress fibers are the main contractile force generator in non-muscle cells. Actin stress fibers have a less-organized sarcomeric structure constituted of actin, myosin, α-actinin, and other contraction-associated proteins. Their localization and activity of cytoskeletal molecules are highly regulated in a spatiotemporal manner. Moreover, dynamics and contractile properties of actin stress fibers are thought to be regulated by physical cues, for example, the tension externally applied to the actin stress fibers and internally generated by actomyosin contraction. To shed light on contractile properties and dynamics of actin stress fibers, we employed an in vitro experimental system for measurement of contractile properties of individual stress fibers isolated from non-muscle cells. The stall force of actin stress fibers was 10 nN order of magnitude at physiological level of MgATP concentration. The contractile speed was steeply decreased once the tension was acting on the stress fibers.
