Selective phosphorylation of the IgE receptor in antigen-stimulated rat mast cells

Purified rat serosal mast cells were sensitized with mouse immunoglobulin E (IgE) anti-2,4-dinitrophenyl antibody, partially depleted of phosphate, labeled with [³²P]orthophosphate, and stimulated with dinitrophenylated bovine serum albumin or control protein. After 15-120 seconds at 37°C, the cells were extracted with nonionic detergent. IgE receptors were purified by repetitive affinity chromatography and were analyzed by NaDodSO₄/polyacrylamide gel electrophoresis and radioautography. Antigenic stimulation of intact rat mast cells produced a rapid and marked increase in the phosphorylation of the surface-exposed α component of the IgE receptor. However, phosphorylation of the 33,000 M(r) β component of the IgE receptor was not altered significantly by antigen stimulation. This suggests that the selective increase in phosphorylation of the IgE receptor α component may be part of the physiologic mediator secretion process triggered by antigen.