NTAL cooperates with LAT in mast cells to activate PI3K pathway and cytokine production through Grb2-associated binding protein 2 (GAB2) (Gonzalez-Espinosa et al. 2003). FCERI aggregation induced translocation of a significant fraction of GAB2 from the cytosol to the plasma membrane by binding GRB2. Two of the proline-rich motifs in GAB2 are binding sites for the SH3 of GRB2. GAB2 is also recruited to plasma membrane by binding to phosphatidylinositol-3,4,5-trisphosphate (PIP3) with its plecstrin homology (PH) domain. GAB2 can be recruited to FCERI indirectly through GRB2 bound SHC1. SHC1 is recruited to the FCERI beta chain through its SH2 domain and becomes tyrosyl-phosphorylated. Phosphorylated SHC provides a docking site for the GRB2 and this in turn recruits GAB2 (Yu et al. 2006). GAB2 and PI3K are required for FCERI-induced granule translocation.