Kinase activation through the high-affinity receptor for immunoglobulin E

The high-affinity receptor for IgE (Fc epsilon RI) belongs to a class of multimeric receptors associated with nonreceptor tyrosine kinases. It has been assumed that Fc epsilon RI beta and gamma chains, which have extensive cytoplasmic domains, play an important, although undefined role in coupling the receptor to signal transduction mechanisms. The results reviewed here suggest a synergistic effect of these two chains in the initiation of Fc epsilon RI signaling. According to our model, receptor engagement can activate kinase(s), such as lyn, already bound to the receptor under resting conditions. The receptor phosphorylation following this activation can be responsible for recruitment and activation of other signaling molecules, such as syk, which can then activate downstream effector molecules. This model could be extended to include other multimeric receptors, such as the T- and B-cell receptors and the low-affinity receptor for IgG (Fc gamma RIII), that control the activation of cytoplasmic tyrosine kinases.