title: NMDA receptor desensitization regulated by direct binding to PDZ1-2 domains of PSD-95.
abstract: Regulation of N-methyl-d-aspartate receptor (NMDAR) activity by desensitization is important in physiological and pathological states; NMDAR desensitization contributes in shaping synaptic responses and may be protective by limiting calcium influx during sustained glutamate insults. We previously reported that glycine-independent desensitization decreases during hippocampal neuronal development, correlating with NMDAR synaptic localization and association with postsynaptic density 95 (PSD-95). PSD-95/Discs large/zona occludens (PDZ)-1,2 domains of PSD-95 bind to the C-terminus of NMDAR NR2 subunits. The role of PSD-95 in anchoring signaling proteins near NMDARs is well documented. To determine if PSD-95-induced changes in NMDAR desensitization occur because of direct binding to NR2 or due to recruitment of regulatory proteins, we tested the effects of various PSD-95 constructs on NMDAR currents in human embryonic kidney 293 (HEK293) cells and neurons. In HEK cells, wild-type PSD-95 significantly reduced wild-type NMDAR desensitization without altering currents of NMDARs containing NR2A-S1462A, a mutation that abolishes PSD-95 binding. The PSD-95 N-terminus truncated after the PDZ1-2 domains was sufficient for this effect in neurons with low endogenous PSD-95 levels; in NMDAR-expressing HEK cells, the effect persisted when PSD-95 multimerization was eliminated. Moreover other PSD-95 family members with highly homologous PDZ1-2 domains significantly reduced NMDAR desensitization. In mature neurons, disruption of PSD-95/NMDAR interaction through protein kinase C (PKC) activation increased desensitization to levels found in immature neurons, and this effect was not due to PKC direct regulation of NMDAR activity. We conclude that direct binding of PSD-95 increases stability of NMDAR responses to agonist exposure in neuronal and nonneuronal cells.
authors.affiliation: Graduate Program in Neuroscience, University of British Columbia, 4N3-2255 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada.
authors.forename: Lavan
authors.initials: L
authors.lastname: Sornarajah
authors.forename: Oana Cristina
authors.initials: OC
authors.lastname: Vasuta
authors.forename: Lily
authors.initials: L
authors.lastname: Zhang
authors.forename: Christine
authors.initials: C
authors.lastname: Sutton
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Alaa
authors.initials: A
authors.lastname: El-Husseini
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Raymond
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D000076122:Disks Large Homolog 4 Protein; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D051528:Guanylate Kinases; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008565:Membrane Proteins / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D010703:Phorbol Esters / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D013997:Time Factors; D014162:Transfection; D062826:Zonula Occludens-1 Protein
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010703:Phorbol Esters; D010750:Phosphoproteins; D016194:Receptors, N-Methyl-D-Aspartate; C569042:TJP1 protein, human; C569043:Tjp1 protein, mouse; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; D049452:Green Fluorescent Proteins; D015763:2-Amino-5-phosphonovalerate; D051528:Guanylate Kinases; D005998:Glycine