Coimmunoprecipitation of GMRα and β_c from Mo7e and hGMRα/hβ_c -expressing Ba/F-3 cells. (A) Mo7e cells were starved overnight and ¹²⁵I–surface-labeled and treated with (+) or without (−) GM-CSF (6 nmol/L) for 5 minutes and immunoprecipitation was performed either with anti-GMRα MoAb (8G6) or anti-β_c MoAb (4F3). Immunoprecipitated proteins were separated on 7.5% SDS-PAGE under reducing conditions and the gel was exposed to phosphorimager. (B) hGMRα/hβ_c -expressing Ba/F-3 cells were starved overnight and ¹²⁵I–surface-labeled and treated with (+) or without (−) GM-CSF (6 nmol/L) for 5 minutes and immunoprecipitation was performed with anti-GMRα MoAb (8G6). Immunoprecipitated proteins were separated on 7.5% SDS-PAGE under reducing conditions and the gel was exposed to phosphorimager. (C) Proteins immunoprecipitated from hGMRα/hβ_c -expressing Ba/F-3 cells with anti-GMRα MoAb (8G6) either in the presence (+) or absence (−) of GM-CSF were subjected to Western transfer and immunoblotted using anti-β_c antibody 1C1 (upper panel) or antiphosphotyrosine antibody PY20 (lower panel).