Probing Mechanical Interactions between Lamellipodia and Surrounding Mechanical Environments

Lamellipodia are quasi-two-dimensional actin projection formed on the leading edge of the cell, playing an important role in sensing surrounding mechanical environments via focal adhesions. Although molecular players, architecture, and dynamics of the lamellipodia have been investigated extensively during recent decades, it still remains elusive how the lamellipodia mechanically interact with an underlying substrate via sparsely distributed focal adhesion points. To better understand the mechanical interactions, we developed an agent-based model of a branched actin network consisting of F-actin and Arp2/3 with myosin motors and an underlying substrate. Using the model, we demonstrated how each parameter affects force development/relaxation, actin retrograde flow, substrate deformation, traction force, and focal adhesion dynamics. We found that mechanical interactions between lamellipodia and the substrate are very different from those between finger-like projection called filopodia and the substrate, which have been probed actively by various modeling studies recently. We also identified conditions under which a dynamic steady state emerges for actin retrograde flow.