Heterodimers of ERBB2 and ERBB3 are able to bind GRB7 (Fiddes et al. 1998) through phosphorylated tyrosine residues in the C-tail of ERBB3 (Y1199 and Y1262) (Fiddes et al. 1998), but the exact downstream signaling of this complex has not been elucidated. GRB7 can recruit SHC1 to the active ERBB2 complex, and contributes to ERBB2 signaling-induced RAS activation, which promotes cellular proliferation, but the exact mechanism has not been elucidated (Pradip et al. 2013). In addition, GRB7 can be phosphorylated by the integrin-activated PTK2 (FAK), leading to VAV2-dependent activation of RAC1 and promotion of cell migration. The exact mechanistic details of GRB7-induced RAC1 activation are not known (Pradip et al. 2013).