FIG. 3.

Ligand-independent dimerization of TrkA deletion mutants. (A) Schematic representation of HA- and Myc-tagged wild-type TrkA receptors. These epitopes were introduced in the same position within the different TrkA mutants. (B) Dimerization analysis in HEK293 cells transiently transfected with the following pairs of expression vectors: HA-TrkA and Myc-TrkA; HA-TrkA-ΔIg1 and Myc-TrkA-ΔIg1; HA-TrkA-ΔIg2 and Myc-TrkA-ΔIg2; and HA-TrkA-ΔIg1,2 and Myc-TrkA-ΔIg1,2. As a positive control, we used HA-TrkA- and Myc-TrkA-transfected cells treated with NGF (100 ng/ml) for 5 min. Two days after transfection, cells were lysed and immunoprecipitations (IP) were performed using the 12CA5 anti-HA antibody. Western blot was done with either 9E10 anti-Myc antibody (upper panel) or anti-203 pan-Trk antiserum (bottom panel). (C) Western blot of whole-cell extracts (40 μg of total protein) done with either 203 antiserum, 9E10, or 12CA5. Immunoreactive protein bands were detected by chemiluminescence. Sizes are shown in kilodaltons.