SOCS2 effects are mediated through Tyr487 and Tyr595. (A) 293T cells were transfected with wild-type or mutated GH receptor constructs, then they were starved of (white bars) or stimulated with rpGH (black bars), and the luciferase activity from an LHRE-luciferase reporter was measured. Data were corrected for transfection efficiency by cotransfection of a β-galactosidase–expressing plasmid. *P < 0.05, significant difference between stimulated receptors. (B–D) 293T cells were transfected with wild-type GH receptor, (B) Y595F GH receptor, (C) Y487F GH receptor, or (D) Y487,595F GH receptor and increasing concentrations of SOCS2 plasmid (ng). Data were corrected for transfection efficiency by cotransfection of a β-galactosidase–expressing plasmid. Luciferase activity was corrected using values obtained in the absence of GH, then expressed as a percentage of wild-type GH receptor activity without SOCS2 expression, which was assigned a value of 100%. Experiments were performed in triplicate and data presented here are representative of 3 independent experiments. Expression of SOCS2 was confirmed by Western blotting of cell lysate with antibodies against the Flag epitope at the N terminus of the SOCS2 expression construct.