Fig. 3. Stat3 tyrosine phosphorylation is independent of nuclear translocation and receptor endocytosis. Western blot analyses were performed using antibodies to phosphoY⁷⁰⁵-Stat3 or total Stat3 protein to probe immunoprecipitates prepared with antibodies to total Stat3 protein from lysates of either EGF-treated NIH-3T3/EGFR (A) or PDGF-BB-treated Balb/c-3T3 (B) cells. Cells were treated with the endocytosis inhibitors followed by growth factor stimulation for the indicated times.