The Fc(epsilon)RIbeta subunit functions as an amplifier of Fc(epsilon)RIgamma-mediated cell activation signals.

The high affinity IgE receptor (Fc(epsilon)RI) plays a central role in the initiation of allergic responses. Fc(epsilon)RI is multimeric and is expressed as either (alpha)(gamma2) trimers or (alpha)(beta)(gamma2) tetramers. Recently, polymorphisms of the beta chain gene have been associated with the development of various allergic phenotypes. Until now, the role of beta in Fc(epsilon)RI-dependent signaling was largely unknown. For that reason, we compared the signaling characteristics of various wild-type and mutant (alpha)(gamma2) and (alpha)(beta)(gamma2) Fc(epsilon)RI complexes. These studies demonstrate that the gamma dimer functions as an autonomous activation module, while beta functions as an amplifier that provides a gain of 5- to 7-fold, as measured by Syk activation and calcium mobilization.