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

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Abstract
Purified rat serosal mast cells were sensitized with mouse 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 s at 37.degree. C, the cells were extacted with nonionic detergent. IgE receptors were purified by repetitive affinity chromatography and were analyzed by sodium dodecyl sulfate/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 .alpha. component of the IgE receptor. Phosphorylation of the 33,000 MW .beta. component of the IgE receptor was not altered significantly by antigen stimulation. Apparently, the selective increase in phosphorylation of the IgE receptor .alpha. component may be part of the physiologic mediator secretion process triggered by antigen.