Figure 1. Membrane proximal Toll-like Receptor 2 signaling in response to Francisella tularensis: Ligand bound TLR2 () signaling leads to the sequential activation of Rac and Ras GTPases.

Rac and Ras cooperate to activate Raf which leads to ERK activation, while Rac stimulates the PI3K/Akt pathway which antagonizes ERK by inhibiting Raf. The lipid product of PI3K, PIP3, also recruits positive (Vav) and negative (GAP) regulators of Ras and Rac to the immunological synapse. (Red arrows denote inhibition, black arrows denote stimulation.)