Figure 2.

SH2-Bβ potentiates GH-induced tyrosyl phosphorylation of endogenous JAK2. COS cells were cotransfected with plasmid (5 μg) encoding GHR and either control plasmid (10 μg) or plasmid (10 μg) encoding SH2-Bβ. Twenty-four hours after transfection, cells were deprived of serum overnight and stimulated with 500 ng/ml GH for 10 min. Proteins (700 μg) in the lysates were immunoprecipitated with αJAK2 and immunoblotted with αPY. Levels of endogenous JAK2 in COS cells are too low to be detected by αJAK2 in immunoblots.