Subunit-specific regulation of NMDA receptor endocytosis.
At excitatory synapses, both NMDA and AMPA receptors are localized to the postsynaptic density (PSD). However, unlike AMPA receptors, synaptic NMDA receptors are stable components of the PSD. Even so, surface-expressed NMDA receptors undergo endocytosis, which is more robust early in development and declines during synaptic development. We investigated the subunit-specific contributions to NMDA receptor endocytosis, specifically defining the endocytic motifs and endocytic pathways preferred by the NR2A and NR2B subunits. We find that NR2A and NR2B have distinct endocytic motifs encoded in their distal C termini and that these interact with clathrin adaptor complexes with differing affinities. We also find that NR2A and NR2B sort into different intracellular pathways after endocytosis, with NR2B preferentially trafficking through recycling endosomes. In mature cultures, we find that NR2B undergoes more robust endocytosis than NR2A, consistent with previous studies showing that NR2A is more highly expressed at stable synaptic sites. Our findings demonstrate fundamental differences between NR2A and NR2B that help clarify developmental changes in NMDA receptor trafficking and surface expression.
Lavezzari
Gabriela
G
National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
McCallum
Jennifer
J
Dewey
Colleen M
CM
Roche
Katherine W
KW
D033962:Adaptor Protein Complex 2 / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D006367:HeLa Cells; D006624:Hippocampus / Q000166:cytology / Q000254:growth & development; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D025941:Protein Interaction Mapping; D021122:Protein Subunits; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D013569:Synapses / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques
D033962:Adaptor Protein Complex 2; D008562:Membrane Glycoproteins; C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; C072237:TGOLN2 protein, human; C513045:Tgoln2 protein, rat; C033652:postsynaptic density proteins