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Cells change direction of migration by sensing rigidity of environment and traction force, yet its underlying mechanism is unclear. Here we show that tip actin barbed ends serve as an active 'force sensor' at the leading edge. We established a method to visualize intracellular single-molecule fluorescent actin through an elastic culture substrate. We found that immediately after cell edge stretch, actin assembly increased specifically at the lamellipodium tip. The rate of actin assembly increased with increasing stretch speed. Furthermore, tip actin polymerization remained elevated at the subsequent hold step, which was accompanied by a decrease in the load on the tip barbed ends. Stretch-induced tip actin polymerization was still observed without either the WAVE complex or Ena/VASP proteins. The observed relationships between forces and tip actin polymerization are consistent with a force-velocity relationship as predicted by the Brownian ratchet mechanism. Stretch caused extra membrane protrusion with respect to the stretched substrate and increased local tip polymerization by >5% of total cellular actin in 30 sec. Our data reveal that augmentation of lamellipodium tip actin assembly is directly coupled to the load decrease, which may serve as a force sensor for directed cell protrusion.
This article was published in the following journal.
Name: Genes to cells : devoted to molecular & cellular mechanisms
The assembly of protein actin into double-helical filaments promotes many eukaryotic cellular processes that are regulated by actin binding proteins (ABPs). Actin filaments can adopt multiple conforma...
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An actin capping protein that binds to the barbed-ends of ACTIN filaments. It is a heterodimer consisting of an alpha and a beta subunit. It regulates actin assembly by stabilizing actin oligomers for elongation. In SKELETAL MUSCLE, CapZ is localized to the Z-disk.
Actin capping proteins are cytoskeletal proteins that bind to the ends of ACTIN FILAMENTS to regulate actin polymerization.
One of the minor protein components of skeletal muscle. Its function is to serve as the calcium-binding component in the troponin-tropomyosin B-actin-myosin complex by conferring calcium sensitivity to the cross-linked actin and myosin filaments.
A neuronal calcium sensor protein that is expressed as several isoforms and can interact with ACTIN; TUBULIN; and CLATHRIN.
A family of low MOLECULAR WEIGHT actin-binding proteins found throughout eukaryotes. They remodel the actin CYTOSKELETON by severing ACTIN FILAMENTS and increasing the rate of monomer dissociation.