(A) Autophosphorylation of TrkB. NIH3T3 cells stably transfected with wild type and mutated TrkB were treated with/without 50ng of BDNF for one hour. Immunoprecipitaiton was performed with anti-panTrk antibody, and immunoblots were performed with the indicated antibodies. Densitometrical analysis was performed with GeneTools (Syngene, Frederick, MD). The experiments were repeated three times, and representative results are shown. Relative pTrk/TrkB ratios were indicated, non-treated NIH3T3/wild type TrkB as 1. Bars, standard deviation. (B) Activation of TrkB downstream signaling by BDNF. TrkB was stimulated as described above. Western blots were performed with the indicated antibodies. Relative expression levels of pAkt and pERK were indicated.