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. 2017 Jan;74(1-2):169-193.
doi: 10.1007/s00285-016-1027-z. Epub 2016 May 20.

Existence of and decay to equilibrium of the filament end density along the leading edge of the lamellipodium

Affiliations

Existence of and decay to equilibrium of the filament end density along the leading edge of the lamellipodium

Angelika Manhart et al. J Math Biol. 2017 Jan.

Abstract

A model for the dynamics of actin filament ends along the leading edge of the lamellipodium is analyzed. It contains accounts of nucleation by branching, of deactivation by capping, and of lateral flow along the leading edge by polymerization. A nonlinearity arises from a Michaelis-Menten type modeling of the branching process. For branching rates large enough compared to capping rates, the existence and stability of nontrivial steady states is investigated. The main result is exponential convergence to nontrivial steady states, proven by investigating the decay of an appropriate Lyapunov functional.

Keywords: Actin; Lamellipodium; Lyapunov function.

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Figures

Fig. 1
Fig. 1
Lateral flow. Solid and dashed lines represent the present and, respectively, a future state of filaments of the leading edge (drawing courtesy of J. Vic Small)
Fig. 2
Fig. 2
Illustration of the proof of Proposition 2
Fig. 3
Fig. 3
Approximate and numerical solution for α=10 and ε=0.1 with c(x) given by (26). The end density of the right moving filaments u is depicted in dark and light blue (dashed) and that of the left moving filaments v (solid) in red and orange. Thin lines (red and dark blue) are the asymptotic approximations, thick lines (orange and light blue) are the numerical solution of the time dependent problem after t=20 and the left y-axis applies. In green (dotted) the lateral flow c(x) is depicted, the values are in relation to the right y-axis
Fig. 4
Fig. 4
This figure shows the trajectories in (pq)-phase space of the stationary equation with constant c and (DBC). The orange, diagonal lines represent the boundary conditions q=-p at x=0 and q=p at x=1. Dashed curves represent (29) for different values of E0 and the blue lines the corresponding solutions curves fulfilling p(0)+q(0)=0. The red line is desired the solution satisfying both boundary conditions
Fig. 5
Fig. 5
Density distribution of filaments along the leading edge for Dirichlet boundary conditions as given in Eq. (2) using the equation prior to non-dimensionalization. Red-dotted and blue-dashed lines refer to right and left moving filaments respectively; the black-solid line shows the total filament end density. Parameters (not scaled): L=50μm, κbr=10/s, κcap=0.1/s, crec=9.1/(μms), c(x)0.305μm/s

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