A theoretical approach to actin filament dynamics

Dynamic control of the actin network in eukaryotic cells plays an essential role in their movement, but to date our understanding of how the network properties are controlled in space and time is still rudimentary. For example, how the cell maintains the pools of monomeric actin needed for a rapid response to signals, how the filament length distribution is controlled, and how the actin network properties are modulated by various bundling and severing proteins to produce the mechanical response is not known. Here we address the simplest aspect of this, which is to understand the temporal evolution of the length distribution in vitro in order to understand what the relevant time scales are for establishment of a time-invariant distribution. Surprisingly, we find that there are very long-lived intermediate length distributions that are not exponential. The results shed light on the time scale needed to observe genuine steady-state distributions, and emphasize the necessity of control molecules for modulating the time scale.