Abstract
It has been suggested that myosin II exerts traction forces at the posterior ends and retracting pseudopodia of migrating cells, but there is no direct evidence. Here, using a combination of total internal reflection fluorescence (TIRF) microscopy and force microscopy with a high spatial resolution of approximately 400 nm, we simultaneously recorded GFP-myosin II dynamics and traction forces under migrating Dictyostelium cells. Accumulation of filamentous myosin II and a subsequent increase in traction forces were detected in pseudopodia just before retraction. In the case of motorless myosin II, traction forces did not increase after accumulation, suggesting that the source of the retraction force is the motor activity of accumulated myosin II. Simultaneous recording of F-actin and traction forces revealed that traction forces were exerted under spot-like regions where F-actin accumulated. Cells migrated in a direction counter to the sum of the force vectors exerted at each spot, suggesting that the stress spots act as scaffolds to transmit the propulsive forces at the leading edge generated by actin polymerization.
Highlights
Cell migration plays an essential role during the development of most organisms
It is well known that cell migration is a complex process mediated by dynamic changes in the actinmyosin cytoskeleton
If this is the case, substratum contact sites in the anterior portions of migrating cells should function as anchorages or scaffolds to allow pushing of the leading edge
Summary
Cell migration plays an essential role during the development of most organisms (reviewed in Lauffenburger and Horwitz, 1996; Ridley et al, 2003; Raftopoupou and Hall, 2004). It is generally thought that actin polymerization at the leading edge provides a crucial driving force for extension of growth cones (Dent and Gertler, 2003; Kalil and Dent, 2005), keratocytes (Svitkina et al, 1997; Pollard and Borisy, 2003; Jurado et al, 2005), fibroblasts (Wang, 1985; Galbraith and Sheetz, 1997), neutrophils (Torres and Coates, 1999; Parent, 2004) and Dictyostelium cells (Yumura et al, 1984; Yumura, 1996a; Yumura and Fukui, 1998; Parent, 2004), whereas the detachment and retraction of the rear of the cell from the substratum is thought to be induced by contraction through myosin-II-dependent processes in Dictyostelium cells (Yumura et al, 1984; Yumura and KitanishiYumura, 1990; Yumura, 1993; Small, 1989; Jay and Elson, 1992; Jay et al, 1995; Uchida et al, 2003) and fibroblasts (Chen, 1981; Galbraith and Sheetz, 1997) If this is the case, substratum contact sites in the anterior portions of migrating cells should function as anchorages or scaffolds to allow pushing of the leading edge.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
