Impaired tyrosine phosphorylation and Ca2+ mobilization, but not degranulation, in lyn-deficient bone marrow-derived mast cells.

Signaling through the high affinity IgE receptor (Fc epsilon RI) on mast cells and basophils results in rapid increases in tyrosine phosphorylation on a number of proteins. Fc epsilon RI associates with two classes of the tyrosine kinases, the Src family kinases, such as Lyn, c-Yes, and c-Src, and the Syk kinase. In this work, using primary mast cells derived from wild-type (lyn +/+) and lyn-deficient (lyn -/-) mice, we report that Lyn plays a part in signaling via Fc epsilon RI. Unlike lyn +/+ mast cells, cross-linking of Fc epsilon RI in lyn -/- mast cells failed to induce protein-tyrosine phosphorylation of various substrates, and evoked a delayed and slow Ca2+ mobilization. However, degranulation, adhesion, and production of cytokines occurred normally in lyn -/- mast cells. Our data suggest that the activity of the other Src family kinases, such as c-Src, can complement the role of Lyn in inducing most, but not all, biologic and biochemical responses to Fc epsilon RI cross-linking.