Organized Randomness: How Hierarchical Coupling of an Excitable System and a Bistable Switch Shape Spontaneous Cell Migration

-PTEN switch to stabilize cell polarity. The same Ras excitable network also drives constitutive macropinocytosis, revealing a shared mechanism for membrane protrusion and fluid uptake. This hierarchical excitable-bistable architecture, coupled with motile machinery, converts intrinsic molecular noise into structured, non-Brownian exploratory behavior, representing an adaptive strategy that enables cells to exploit stochasticity for navigation in complex natural environments.