The complex of activated NTRK2 (TRKB) and activated FYN binds to the NMDA receptor complex subunit GRIN2B (also known as NR2B or GluN2B). The GRIN2A subunit of the NMDA receptor does not co-immunoprecipitate with activated FYN (Mizuno et al. 2003, Li et al. 2017). It is not clear whether FYN interacts with GRIN2B in the context of the NMDA receptor complex.