(A) Amino acids differentially regulate the interaction of GATOR2 with the three CASTOR complexes. HEK-293T cells cotransfected with the indicated cDNAs were deprived of amino acids for 50 min or starved and restimulated with amino acids for 10 min. Anti-HA immunoprecipitates and cell lysates were analyzed by immunoblotting for levels of the indicated proteins.
(B) Endogenous CASTOR1, but not CASTOR2, associates with GATOR2 in an amino acid-sensitive manner. A HEK-293T cell line expressing endogenously FLAG-tagged WDR59 was treated as in (A) and anti-FLAG immunoprecipitates were analyzed by immunoblotting for the indicated proteins.
(C) Deprivation of arginine, but not leucine, promotes the interaction between the CASTOR1 homodimer and endogenous GATOR2. Cells were deprived of leucine, arginine, or all amino acids for 50 min, and restimulated for 10 min with the respective amino acids where indicated. Anti-HA immunoprecipitates were prepared and analyzed as in (A).
(D) Arginine disrupts the interaction between GATOR2 and CASTOR1-containing dimers in vitro. Anti-HA immunoprecipitates were prepared from HEK-293T cells expressing the indicated cDNAs and deprived of amino acids for 50 min. Indicated amino acids were added directly to the immunoprecipitates, which after re-washing, were analyzed as in (A).
(E) Arginine dose-dependently disrupts the interaction between GATOR2 and CASTOR1-containing dimers in vitro. The experiment was performed and analyzed as in (D), except using the indicated concentrations of arginine.
(F) Arginine regulates the interaction between the ACT domains of CASTOR1 but not CASTOR2 in cells. HEK-293T cells cotransfected with the indicated cDNAs in expression vectors were either deprived of arginine in the cell media for 50 min or starved and restimulated with arginine for 10 min. Anti-HA immunoprecipitates were prepared and analyzed as in (A).