[Protein phosphorylations in granulocyte/macrophage colony-stimulating factor-stimulated human peripheral blood...

Peripheral blood eosinophils from normal healthy subjects were isolated on a Percoll gradient and were incubated with [32P] orthophosphoric acid. 32P-labeled eosinophils were washed and stimulated with GM-CSF under different conditions. After reaction was stopped, SDS/PAG electrophoresis was performed along with autoradiographs to determine the incorporation of 32P into proteins. GM-CSF-stimulated eosinophils produced an increase of 32P incorporation into the bands in the 31 kDa and 35 kDa areas after 30 sec and 1 min of stimulation. The increase of 32P incorporation was dependent on Mg2+ concentration and temperature, suggesting that proteins in the eosinophils with apparent molecular weights of 31 kDa and 35 kDa can be phosphorylated with the stimulation of GM-CSF.