Actin Migration Driven by Directional Assembly and Disassembly of Membrane-Anchored Actin Filaments

Actin and actin-associated proteins migrate within various cell types. To uncover the mechanism of their migration, we analyzed actin waves, which translocate actin and actin-associated proteins along neuronal axons toward the growth cones. We found that arrays of actin filaments constituting waves undergo directional assembly and disassembly, with their polymerizing ends oriented toward the axonal tip, and that the lateral side of the filaments is mechanically anchored to the adhesive substrate. A combination of live-cell imaging, molecular manipulation, force measurement, and mathematical modeling revealed that wave migration is driven by directional assembly and disassembly of actin filaments and their anchorage to the substrate. Actin-associated proteins co-migrate with actin filaments by interacting with them. Furthermore, blocking this migration, by creating an adhesion-free gap along the axon, disrupts axonal protrusion. Our findings identify a molecular mechanism that translocates actin and associated proteins toward the cell's leading edge, thereby promoting directional cell motility.