Rag C also known as GTR2, RRAGC is a member of the GTR/RAG GTP-binding protein family. Rag C is a monomeric guanine nucleotide-binding protein which forms a heterodimer with RagA or RagB to couple intracellular amino acid availability to mTORC1 recruitment and activation at the lysosome. Through interactions with the Ragulator complex and downstream mTORC1 effectors, Rag C helps regulate protein synthesis, autophagy, lysosome biogenesis, and metabolic reprogramming in response to nutrient cues. Dysregulated Rag GTPase signaling can perturb nutrient-sensing checkpoints and has been implicated in phenotypes relevant to proliferative control, immune cell function, and cellular stress adaptation.