Figure 3. GH induces Jak2 phosphorylation and release from the GHR.

A. IM9 cells were treated with GH for 1 h at 37°C as indicated, followed by cell fractionation. Membrane (M) and cytosol (C) fractions were immunoprecipitated for Jak2 and analysed with the indicated antibodies. The ratio of phosphorylated Jak2 (pJak2) and total Jak2 was calculated for each fraction. Total cell lysates were analysed for Hsp90, a cytosolic marker. B. IM9 cells were pretreated with vehicle (dimethylsulfoxide), staurosporin or MG132 for 1 h and stimulated with GH at 37°C as indicated. Total cell lysates (TCL) and GHR immunoprecipitations were analysed on western blot with the indicated antibodies. C. IM9 cells were pretreated with staurosporin (Stau) for 1 h followed by incubation with GH at 37°C as indicated. Jak2 immunoprecipitations were analysed with the indicated antibodies. Data in A, B, and C are representative of three independent experiments.