Schwann cells were first maintained in defined media for 24hrs and then incubated with Cadm3-Fc (20 nM) for 30 min., before stimulation with rhNrg1-EGFD (Nrg1; 10 nM). Human IgG (hu-IgG) is used as a control for the specificity of the Cadm3-Fc interaction. ErbB3 immunoprecipitated complexes were then analyzed for the presence of ErbB2, Cadm3-Fc, Cadm1, Cadm4, and PTPN13. For each condition, three lanes were run: “in” represents the input lanes (2% of material use for IP), “Δ” represents the depleted material after IP (2% of material used for IP, after the IP), and “IP” represents the immunoprecipitated lanes. The solid triangle indicates Cadm4, whereas the open triangle corresponds to the heavy chain of the mouse anti-ErbB3 antibody used for the co-immunoprecipitation.