Involved in FCER1 (high affinity immunoglobulin epsilon receptor)-mediated signaling in mast cells. May also be involved in BCR (B-cell antigen receptor)-mediated signaling in B-cells and FCGR1 (high affinity immunoglobulin gamma Fc receptor I)-mediated signaling in myeloid cells. Couples activation of these receptors and their associated kinases with distal intracellular events through the recruitment of GRB2 (By similarity). When phosphorylated, interacts with GRB2. May also interact with SOS1, GAB1 and CBL (By similarity). Present in lipid rafts. Phosphorylated on tyrosines following cross-linking of BCR in B-cells, high affinity IgG receptor (FCGR1) in myeloid cells, or high affinity IgE receptor (FCER1) in mast cells; which induces the recruitment of GRB2.