ARMS and Trk receptors interact. (A) ARMS interacts with Trk receptors. Lysates from HEK293 cells transfected with FLAG-ARMS and/or TrkA, B, or C receptor were immunoprecipitated with FLAG antibodies, followed by Western blotting by anti-Trk antisera. (B) Immunoprecipitated ARMS does not bind EGF receptors. Experiments were carried out in the same way as described in panel A, but EGF receptor was analyzed. (C) ARMS interacts with TrkB in primary cortical neurons. Cells were cultured for 8–12 DIV and crosslinked with the lipid-soluble compound DSP (Pierce), a thiol-cleavable reagent. Control rabbit IgG was used instead of anti-Trk to demonstrate the specificity of the Trk–ARMS interaction. (D) Co-localization of TrkB and ARMS in primary cortical neurons. Staining was carried out with affinity-purified rabbit polyclonal antibody 892 against ARMS (green; Kong et al, 2001) and the mouse monoclonal antibody B3 (Santa Cruz) against TrkB (red). Co-localization of both proteins is shown in yellow. Images were collected on a confocal microscope. An area within the cortical neuron was enlarged to highlight TrkB and ARMS colocalization. Scale bar=10 μm.