Figure 2.

Amino acid signaling in eukaryotes. In mammals, amino acids (red) are monitored by multiple sensors (orange) that engage transducers (blue) at multiple steps in the GATOR2–GATOR1–Ragulator–Rag GTPase signaling cascade to coordinate TOR (teal) activity at the surface of the lysosome. Very few of these signaling components are conserved in plants (gray indicates not conserved in plants). Sar1b and LARS, which have essential roles in membrane trafficking and tRNA synthesis, respectively, were exapted as amino acid sensors in the animal lineage and may not act as amino acid sensors in plants.