In the hippocampus, ApoER2 is complexed with NMDA receptors through the PSD-95 adapter protein. When reelin binds ApoER2, it initiates tyrosine phosphorylation of NMDA receptors. This occurs through Dab-1 activation of Src family kinases, which have been shown to play a role in regulating synaptic plasticity. VLDLR also acts as a receptor coupled to ApoER2 as it does during development, but its role is not well understood. ApoER2 plays a more important role in this process, most likely due to its ability to bind the PSD-95 adapter protein through the 59 amino acid insert on its cytoplasmic tail. Studies with mice have shown that knocking out ApoER2 or just the alternatively spliced exon 19 causes a much greater impairment of LTP than knocking out VLDLR.