VRP stimulation induces tyrosine phosphorylation of Shc and its association with SOS and Grb2. HEL-JW cells unstimulated or stimulated with VRP for the indicated times were lysed in RIPA buffer and immunoprecipitated with anti-Shc antibody. (A) The immune complexes were resolved on 8% SDS-PAGE and immunoblotted with antiphosphotyrosine (upper panel), anti-Shc (middle panel), or anti-SOS (bottom panel) antibodies. (B) The immunocomplexes were resolved on 12% SDS-PAGE and immunoblotted with anti-Grb2 antibody (upper panel) or anti-Shc antibody (bottom panel). The changes in the association of SOS or Grb2 with Shc are indicated (by fold increase) based on the densitometry values. Normal rabbit IgG was used as a negative control for the immunoprecipitations.