β_c phosphorylated in response to GM-CSF, IL-3, or IL-5 is immunoprecipitable by anti-GMRα antibody. (A) Mo7e cells were starved overnight and then treated with either 6 nmol/L GM-CSF, IL-3, or medium for 5 minutes at 4°C and then immunoprecipitated with either anti–IL-3Rα (9F5), anti-GMRα (8G6), or anti-β_c (8E4) antibody. (B) TF-1.8 cells were starved overnight and then treated with either 6 nmol/L GM-CSF, IL-3, or IL-5 or medium for 5 minutes at 4°C and then immunoprecipitated with either anti-GMRα (8G6) or anti-β_c (8E4) antibody. Immunoprecipitated proteins were separated on 7.5% SDS-PAGE, Western transferred, and then immunoblotted with antiphosphotyrosine antibody (PY20).