Pharmacological characterization of recombinant NR1/NR2A NMDA receptors with truncated and deleted carboxy termini expressed in Xenopus laevis oocytes.
OBJECTIVE
The carboxy terminal domain (CTD) of NR2 N-methyl-d-aspartate receptor (NMDAR) subunits interacts with numerous scaffolding and signal transduction proteins. Mutations of this region affect trafficking and downstream signalling of NMDARs. This study determines to what extent characteristic pharmacological properties of NR2A-containing NMDARs are influenced by this key functional domain.


METHODS
Using recombinant receptor expression in Xenopus laevis oocytes and two electrode voltage clamp recordings we characterized pharmacological properties of rat NR1/NR2A NMDARs with altered CTDs. We assessed the effects of truncating [at residue Iso1098; NR2A(trunC)] and deleting [from residue Phe822; NR2A(delC)] the CTD of NR2A NMDAR subunits on agonist potencies, channel block by Mg(2+) and memantine and potentiation of NMDAR-mediated responses by chelating contaminating divalent cations.


RESULTS
Truncation or deletion of the CTD of NR2A NMDAR subunits did not affect glutamate potency [EC(50) = 2.2 micromol.L(-1), NR2A(trunC); 2.7 micromol.L(-1), NR2A(delC) compared with 3.3 micromol.L(-1), NR2A(WT)] but did significantly increase glycine potency [EC(50) = 500 nmol.L(-1), NR2A(trunC); 900 nmol.L(-1), NR2A(delC) compared with 1.3 micromol.L(-1), NR2A(WT)]. Voltage-dependent Mg(2+) block of NR2A(WT)- and NR2A(trunC)-containing NMDARs was similar but low concentrations of Mg(2+) (1 micromol.L(-1)) potentiated NR1/NR2A(delC) NMDARs. Memantine block was not affected by changes to the structure of the NR2A CTD. EDTA-induced potentiation was similar at each of the three NMDAR constructs.


CONCLUSIONS
Of the parameters studied only minor influences of the CTD were observed; these are unlikely to compromise interpretation of studies that make use of CTD-mutated recombinant receptors or transgenic mice in investigations of the role of the CTD in NMDAR signalling.
Puddifoot
C A
CA
Centres for Integrative Physiology and Neuroscience Research, University of Edinburgh, UK.
Chen
P E
PE
Schoepfer
R
R
Wyllie
D J A
DJ
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D008274:Magnesium / Q000494:pharmacology; D008559:Memantine / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010957:Plasmids; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins; D015398:Signal Transduction / Q000187:drug effects; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology
C409466:NR1 NMDA receptor; C120997:NR2A NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D011994:Recombinant Proteins; D004492:Edetic Acid; D008274:Magnesium; D015032:Zinc; D008559:Memantine