Grb2 binds directly to autophosphorylated Tie2 receptor. GRB2 also contains two SH3 domains, which bring various ligands to the sites of active signaling. One of the SH3 domains on Tie2-bound Grb2 recruits SOS1, an activating nucleotide exchange factor for Ras. This interaction of Sos1 to Grb2 brings Sos1 towards Ras molecules leading to Ras activation. Ras is implicated in the MAP kinase cascade, a pathway in cell growth stimulation, migration and differentiation.