Figure 1.

Overview of the model and modeling approach. A schematic of the mutual antagonism, autoactivation, and biochemical conservation Rac and Rho GTPase signaling model investigated here is shown. Rac and Rho GTPases exist in active, membrane-bound, slowly diffusing forms and in inactive, cytosolic, quickly diffusing forms. For this model, we analyze the types of spatial GTPase activation profiles (regulatory phenotypes) that arise from PDE simulations (shown in the six plots in the dashed box). We do not explicitly model cytoskeletal remodeling or 2D cell morphology. Rather, we rely on prior literature that has demonstrated links between cell shapes and GTPase signaling through cytoskeletal regulation. For example, Rac-dominated cells expand and protrude because of actin assembly, Rho-dominated cells contract because of myosin-based contraction, and spatially organized Rac and Rho signals lead to polarized cells. The bottom row of cartoons depicts different shapes that would naturally be linked to different GTPase signaling profiles. The box around the GTPase model and spatial activation profiles indicates that this is the focus of this article, whereas the shape morphologies outside of this box are inferred and not directly modeled. To see this figure in color, go online.