The mechanism of dynamic steady states in lamellipodia
Fig 2
The dynamic steady state of the branched network under the reference condition.
(A) Snapshots of networks taken at 0 s, 150 s, and 300 s. The network was homogeneous and maintained continuity regardless of time points. (B) Snapshot showing links (green circles) formed in the focal adhesion region (y = 0.81 - 1.69 µm) and forces acting on the underlying substrate via color scaling (red: high force, white: low force) taken at 300 s. (C) Time evolution of the number of the links formed between the substrate and the network. (D) The total substrate force exerted by the network via the links as a function of time. (E) Time evolution of retrograde flow speed. (F) Kymograph of flow speed as a function of y position and time. Quantities shown in (C-F) change more at t < 100 s but exhibit smaller fluctuations around average values after 100 s. (G) Kymograph of actin density as a function of y position and time. Low actin density at y < 0.1 μm between 50 s and 100 s is indicative of the lack of overlap between F-actins and motors. Thus, it took more time for motors to bind and walk along F-actins to recover the retrograde flow, which explains large fluctuations shown in (C-F). Under this reference condition, key parameter values are k+,A = 12 µM-1s-1, RACP = 0.04, RArp2/3 = 0.01, k-,A = 6 s-1, k0,sev = 10-45 s-1, λsev = 1.0 deg-1, RM = 0.004, k20 = 17 s-1, and AFA = 0.35.