NTF3-induced dimerization of the receptor tyrosine kinase NTRK2 (TRKB) leads to trans-autophosphorylation of NTRK2 on evolutionarily conserved tyrosine residues in the cytoplasmic tail of NTRK2. Phosphorylation of NTRK2 at Y817 and in the region containing residues Y702, Y706 and Y707 in response to NTF3 stimulation was demonstrated with recombinant human NTF3 and recombinant rat Ntrk2. Residues Y702, Y706, Y707 and Y817 of the full-length human NTRK2 correspond to residues Y670, Y674, Y675 and Y785 of the mature rat Ntrk2 (Middlemas et al. 1994). Phosphorylation at Y516 of NTRK2 has not been examined but is assumed. NTRK2 is a low affinity receptor for NTF3, and NTF3 preferentially signals through NTRK3 (TRKC) (Marsh and Palfrey 1996).