Balancing at the edge of excitability: Implications for cell movement

Abstract

Cells rely on the ability to sense and respond to small spatial differences in chemoattractant concentrations for survival. There is growing evidence that this is accomplished by setting the signaling system near the threshold for activation in an excitable system and using the spatial heterogeneities to alter the threshold thereby biasing cell activity in the direction of the gradient. Here we consider a scheme by which the set point is adaptively set near the bifurcation point, but without explicit knowledge of this point. Through simulation, we show that the method would improve chemotactic efficiency of cells. The results of this paper are based on pioneering work by Eduardo Sontag and coworkers, to whom this paper is dedicated in honor of his 70th birthday.

A Compartmentalized Model to Directional Sensing: How can an Amoeboid Cell Unify Pointwise External Signals as an Integrated Entity?

“…Moreover, in the model, we benefit from a switch-like threshold δ between excited and resting states. This algorithm not only provides both simplicity and efficient numerical implementation [22], but also suggests a methodical way for including activation-bias and adaptation capability in an excitable system based on spatial heterogeneities [31]. In this model, we took advantage of a "mean-reverting" process to provide the included noise in the system dynamic [24].…”