Lim Lab | Papers

Mapping the functional versatility and fragility of Ras GTPase signaling circuits through in vitro network reconstitution

Scott Coyle, Wendell A. Lim.
eLife 2016

The Ras-superfamily GTPases are central controllers of cell proliferation and morphology. Ras signaling is mediated by a system of interacting molecules: upstream enzymes regulate Ras's ability to recruit multiple competing downstream effectors. We developed a dynamic in vitro reconstitution of H-Ras signaling systems. By including upstream regulators and downstream effectors, we mapped how different network configurations shaped the timing and amplitude of outputs. Distortion by oncogenic Ras alleles was dependent on the balance of positive (GEF) and negative (GAP) regulators in the system. Different effectors interpreted the same input with distinct dynamics, enabling a Ras system to encode multiple temporal responses to a single input. Different Ras-to-GEF positive feedback mechanisms reshaped output dynamics in distinct ways, such as amplification or overshoot-minimization. This work provides a design manual for programming these systems to produce an array of dynamic signaling behaviors and reveals numerous paths to altered signaling behaviors associated with disease.