In mature neurons, postsynaptic NMDARs are segregated into two populations, synaptic and extrasynaptic NMDARs, which differ in localization, function, and associated intracellular cascades. These two pools are connected via lateral diffusion, and receptor exchange between them modulates synaptic NMDAR content (NMDAR-plasticity). Here, we identify the phosphorylation of the PDZ-ligand of...