The Regulation of Cell Motility Through an Excitable Network

Recent years have demonstrated that the actin cytoskeleton and other signaling elements in motile cells have many of the hallmarks of an excitable medium, including the presence of propagating waves, a refractory period, as well as a threshold for activation. Here we show how these behaviors can be explained by the presence of a signal transduction excitable network that integrates a number of signals and coordinates actin polymerization. In this model, spontaneous triggering of the excitable network accounts for the random migration of unstimulated cells. Moreover, internal and external signals both chemical and mechanical bias excitability spatially, thus providing a means by which cell motility is directed towards spatial cues. We also show how the model predicts that the set point of the excitable system can be altered by changing the threshold.