Gab1 and Gab2 are substrates for SHP-2 in vitro. Tyrosine-phosphorylated Gab1 and STAT3 were isolated by immunoprecipitation from IL-6–stimulated HepG2 cells. Tyrosine-phosphorylated Gab2 was isolated from IL-3–stimulated BAF-B03 cells. These proteins were incubated with a GST fusion protein containing the catalytic domain of SHP-2 (GST-SHP-2 WT) or the catalytic inactive mutant (GST-SHP-2 C/S). Dephosphorylation of these proteins was determined by immunoblotting with anti-phosphotyrosine antibody (upper panel). The amounts of these proteins were analyzed by immunoblotting with anti-Gab1, anti-Gab2, and anti-STAT3 antibodies (lower panel), respectively.