Sigma-1 Receptor Mediates BDNF-Dependent Trk B Receptor Signaling

Object: To investigate the effects of sigma-1 receptor on BDNF-Trk B receptor signaling pathway and the underlying molecular mechanisms.Methods: HEK293 T cells transfected with exogenous Trk B receptor plasmids were given 50 ng/mL BDNF and 10 μM BD1063 stimulation, then western blotting was used to detect phospho-GSK3β and phospho-ERK1/2 levels. Primarily cultured neurons treated with 50 ng/mL BDNF, 1 μM BD1047, 10 μM BD1063 and 100 nM K252 a, the levels of phospho-GSK3β and phospho-ERK1/2 were detected with western blotting.The BDNF-induced dendrite outgrowth was investigated in the primary neuron culture which was stimulated with BD1047 or BD1063. The levels of pERK1/2 and pS9-GSK3β were also detected by western blotting in primary cultured neurons that sigma-1 receptor was knocked out. The internalization of Trk B receptor in HEK293 T cells transfected with Trk B receptor plasmids was revealed by the immunostaining. The complex of sigma-1 receptor and Trk B recepror in HEK293 T cells and neurons was revealed by immunoprecipitation.Results: The BDNF-induced expression of pERK1/2 and pS9-GSK3β were reduced in HEK293 T cells and primary cultured neurons which were inhibited sigma-1receptor. Inhibition of sigma-1 receptor significantly reduced dendrite outgrowth in primary cultured neurons. In primary cultured neurons that sigma-1 receptor was knocked out, the BDNF-induced expression of pERK1/2, pS9-GSK3β and dendrite outgrowth reduced. Inhibition of sigma-1 receptor by BD1047 or BD1063 suppressed BDNF-induced Trk B receptor internalization. Besides, inhibition of sigma-1 receptor significantly altered the association between sigma-1 receptor and Trk B receptor.Conclusion: In nervous system, BDNF-Trk B receptor signaling pathway relays on the mudulation of sigma-1 receptor.