Pharmacologically diverse antidepressant drugs disrupt the interaction of BDNF receptor TRKB and the endocytic adaptor AP-2

Antidepressant drugs activate TRKB (tropomyosin-related kinase B), however it remains unclear whether these compounds employ a common mechanism for achieving this effect. We found by using mass spectrometry that the interaction of several proteins with TRKB was disrupted in the hippocampus of fluoxetine-treated animals (single intraperitoneal injection), including members of the AP-2 complex (adaptor protein complex-2) involved in vesicular endocytosis. The interaction of TRKB with the cargo-docking mu subunit of the AP-2 complex (AP2M) was disrupted by both acute and repeated fluoxetine treatment. However, while the coupling between full length TRKB and AP2M was disrupted by fluoxetine, the interaction between AP2M and the TRKB C-terminal peptide was resistant to this drug, indicating that the binding site targeted by fluoxetine must lie outside of the TRKB:AP2M interface. In addition to fluoxetine, other pharmacologically diverse antidepressants imipramine, rolipram, phenelzine, ketamine, and the ketamine metabolite 2R,6R-hydroxynorketamine (RR-HNK) also decreased the interaction between TRKB:AP2M in vitro, as measured by ELISA. Silencing the expression of AP2M in MG87.TRKB cell line led to increased surface positioning of TRKB and to a higher response to BDNF (brain-derived neurotrophic factor), observed as the levels of active TRKB. Moreover, animals haploinsufficient for the Ap2m1 gene displayed increased levels of active TRKB in vivo, as well as an enhanced cell surface expression of the receptor in cultured hippocampal neurons.\n\nTaken together, our data suggests that disruption of the TRKB:AP2M interaction is an effect shared by several antidepressants with diverse chemical structures and canonical modes of action.