JAB/SOCS1/SSI-1 associates with IL-2Rβ.

293T⁺ cells were transiently transfected with JAB/SOCS1/SSI-1^WT and either WT IL-2Rβ or IL-2Rβ internal deletion mutants, IL-2RβΔA and IL-2RβΔS (A) or the indicated C-terminal truncation mutants (B), or the indicated tyrosine mutants (C). Lysates were immunoprecipitated with anti-IL-2Rβ or anti-Myc epitope antibody 9E10 and then Western blotted with the indicated antibodies. (D) 293T⁺ cells were transfected with WT IL-2Rβ or IL-2RβΔA, γ_c, Jak3, β-casein–luciferase reporter construct and the pRL-TK reporter construct, with or without 20-1000 ng of the JAB/SOCS1/SSI-1^WT expression vector. After 24 hours, cells were split and plated in duplicate and stimulated with 20 nM IL-2 for another 24 hours or left untreated. Activity of the β-casein–luciferase reporter construct was normalized against pRL-TK control luciferase. The data shown are the mean ± SD of 6 experiments.