Activates both Ras-dependent and Ras-independent migratory pathways in melanomas. Contributes to the early phases of agrin-induced tyrosine phosphorylation of CHRNB1. Interacts (via PID domain) with phosphorylated MUSK (via NPXY motif); undergoes tyrosine phosphorylation downstream of activated MUSK. Interacts with GRB2; the interaction is dependent of Tyr-422 phosphorylation and increased by EGF (By similarity). Colocalized with MUSK at the neuromuscular junction. Expressed in both brain and skeletal muscle; widely expressed in brain namely olfactory bulb, cortex, hippocampus, striatum, thalamus, and brain stem (at protein level). Only expressed in melanomas. Weakly expressed in normal melanocytes and benign nevi. Highly expressed at the transition from radial growth phase to vertical growth phase and metastatic melanomas, when tumor cells acquire migratory competence and invasive potential. Phosphorylated; the phosphorylation is enhanced by EGF. Phosphorylation at Tyr-422 is required for the interaction with GRB2 (By similarity).