Mutagenesis Reveals a Role for ABP/GRIP Binding to GluR2 in Synaptic Surface Accumulation of the AMPA Receptor

We studied the role of PDZ proteins GRIP, ABP, and PICK1 in GluR2 AMPA receptor trafficking. An epitope-tagged MycGluR2 subunit, when expressed in hippocampal cultured neurons, was specifically targeted to the synaptic surface. With the mutant MycGluR2delta1-10, which lacks the PDZ binding site, the overall dendritic intracellular transport and the synaptic surface targeting were not affected. However, over time, Myc-GluR2delta1-10 accumulated at synapses significantly less than MycGluR2. Notably, a single residue substitution, S880A, which blocks binding to ABP/GRIP but not to PICK1, reduced synaptic accumulation to the same extent as the PDZ site truncation. We conclude that the association of GluR2 with ABP and/or GRIP but not PICK1 is essential for maintaining the synaptic surface accumulation of the receptor, possibly by limiting its endocytotic rate.