THE BETA-SUBUNIT OF THE FC-EPSILON-RI IS ASSOCIATED WITH THE FC-GAMMA-RIII ON MAST-CELLS

Fc-epsilon-RI ia tetrameric receptor, composed of a ligand recognition subunit, alpha, a beta-chain, and dimeric gamma-chains. Previous studies have indicated that the dimeric gamma-chain is associated with Fc-gamma-RIIIA (CD16) on natural killer cells and macrophages as well as the clonotypic T cell receptor. Here we show that in mast cells, in addition to the dimeric gamma-chains, the beta-subunit is associated not only with Fc-epsilon-RI, but also with Fc-gamma-RIIIA. Functional reconstitution studies with a mastocytoma cell line indicate that Fc-gamma-RIIIA composed of alpha, beta, and gamma-subunits has the capacity for signal transduction. These studies suggest that through the association of alternative ligand recognition subunits (alpha(epsilon), alpha(gamma)), a common signal transduction complex (beta-gamma-2) mediates similar biochemical and effector functions in response to immunoglobulin G (IgG) and IgE.