Differential binding of the AP-2 adaptor complex and PSD-95 to the C-terminus of the NMDA receptor subunit NR2B regulates surface expression.
NMDA receptor expression on the plasma membrane and at synaptic sites is tightly regulated. We have recently shown that the NMDA receptor subunit NR2B has an endocytic motif contained within its C-terminus. We now identify this motif as a consensus tyrosine-based motif (YEKL) and demonstrate that this sequence binds directly to the medium chain of the AP-2 adaptor, a protein complex that links internalized proteins to clathrin. Although the AP-2 binding site on NR2B is adjacent to the PSD-95 binding site, it is distinct, as mutation of tyrosine 1472 of the endocytic motif disrupts AP-2 binding but not binding to PSD-95. Internalization assays reveal that like PSD-95, both SAP97 and PSD-93 inhibit NR2B-mediated endocytosis. Furthermore, we find that co-expression of a PSD-95 mutant that is unable to cluster NMDA receptors also inhibits NR2B-mediated endocytosis. Together, these data demonstrate that AP-2 and PSD-95 bind to unique sites on the C-terminus of NR2B and have antagonistic functional consequences that are independent of the ability of the PSD-95 to cluster receptors on the plasma membrane.
Lavezzari
Gabriela
G
National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 36, Room 5B20, 9000 Rockville Pike, Bethesda, MD 20892, USA.
McCallum
Jennifer
J
Lee
Robert
R
Roche
Katherine W
KW
D033962:Adaptor Protein Complex 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D000076122:Disks Large Homolog 4 Protein; D005786:Gene Expression Regulation / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D033962:Adaptor Protein Complex 2; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C501451:Mpp2 protein, rat; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D016194:Receptors, N-Methyl-D-Aspartate; C033652:postsynaptic density proteins