(b) RagA/RagC and TSC1/TSC2 independently regulate S6K phosphorylation. HEK293 cells were transfected with 200 ng of each Rag and/or ′ constructs as indicated. Amino acid starvation for 1 h (-AA) is indicated. Phosphorylation and protein levels of the transfected proteins were determined by immunoblotting with appropriate antibodies, as indicated. 