FIG. 7.

(A) Schematic representation of point mutations affecting individual amino acid residues within the extracellular region of TrkA. (B) Expression and ligand-independent phosphorylation of mutant TrkA receptors in stably transfected Rat-1 cell lines. Immunoprecipitation (IP) was performed on total cell extracts (2 mg of protein) using the anti-203 pan-Trk antiserum, followed by Western blot with either anti-203 antiserum (upper panel) or 4G10 antiphosphotyrosine monoclonal antibody (lower panel). Expression of TrkA in PC-12 cells (2 mg of protein) is shown for comparison. Sizes are shown in kilodaltons. (C) [³H]thymidine incorporation by Rat-1 cell lines stably expressing mutant TrkA receptors in the absence of serum. Values are the means from at least five experiments performed with two independent clones of each mutant. Data are normalized relative to the [³H]thymidine incorporated by the cells in the presence of serum and expressed as a percentage of the incorporation measured in cells expressing the trk-5 oncogene (100%). Means and SD are shown.