Perverted responses of the human granulocyte-macrophage colony-stimulating factor receptor in mouse cell lines due to cross-species β-subunit association

Transfected murine cell lines are commonly used to study the function of many human cytokine or receptor mutants. This study reports the inappropriate activation of the human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor by the human GM-CSF antagonist, E21R, when the human receptor is introduced into the murine cell line BaF-B03. E21R-induced proliferation of the BaF-B03 cells is dependent on transfection with both hGM-CSF receptor α and β_c subunits. Studies on the underlying mechanism revealed constitutive association between human and mouse β_c and GM-CSF receptor-α, tyrosine phosphorylation of mouse and human β_c, and association of phosphorylated mouse β_c into an activated human GM-CSF receptor complex in response to E21R and GM-CSF. This interspecies receptor crosstalk of receptor signaling subunits may produce misleading results and emphasizes the need to use cell lines devoid of the cognate endogenous receptors for functional analysis of ligand and receptor mutants.