Rapid phosphorylation of a 92,000 MW protein on activation of rat basophilic leukaemia cells for histamine release.

Many cellular functions are modulated by phosphorylation of proteins. The IgE- or ionophore-mediated activation of rat basophilic leukaemia cells (RBL-2H3) was accompanied by the prominent phosphorylation of a 92,000 molecular weight (MW) cellular component. The degree of phosphorylation of this component correlated with the extent of histamine release from the cells. This phosphorylation was rapid, reaching a maximum 2-5 min following the addition of the ionophore or antigen, and decreasing to background by 30 min. In contrast, histamine release is a much slower process. Although the phosphorylation required the presence of Ca2+ in the medium, it was not inhibited by La3+, which blocks the stimulated entry of Ca2+. Therefore, the stimulation of a Ca2+-dependent kinase is an early event in the activation of the rat basophilic leukaemia cells.