Fig. 1. Activated FGFR phosphorylates hSpry2 Y55 in an FRS2-dependent manner. (A) hSpry2 was tyrosine-phosphorylated downstream of the active FGFR. Wild-type hSpry2 (hSpry2WT) was co-transfected into 293T cells with either constitutively active FGFR1 (FcFGFR1/FA/VT+), kinase dead FGFR1 (FcFGFR1/FD) or truncated FcFGFR1 (FcFGFR1/FT). FGFR constructs were immunoprecipitated by protein A (IP:Fc) and either immunoblotted with anti-IgG Fc or anti-phosphotyrosine antibodies. Similarly, hSpry2 was immunoprecipitated and immunoblotted with either anti-hSpry2 antibody or anti-phosphotyrosine antibodies (IP:hSpry2). (B) Selective phosphorylation of hSpry2 on Y55 by the FGFR1/VT+ splice isoform (FcFGFR1/FA/VT+). 293T cells were either stimulated with FGF2 (30 minutes) or transfected with either FcFGFR1/FA/VT+ or VT-isoforms in the presence of either hSpry2WT or hSpry2Y55A. hSpry2 was immunoprecipitated and immunoblotted with anti-hSpry2 antibody and anti-phosphotyrosine antibodies (IP:hSpry2). FGFR constructs were immunoprecipitated by protein A and immunoblotted with anti-IgG Fc (IP:Fc).