[3H]MDL 105,519 binds with equal high affinity to both assembled and unassembled NR1 subunits of the NMDA receptor.
[3H]MDL 105,519 (((E)-3-(2-phenyl-2-carboxyethenyl)-4,6-dichloro-1[3H]-indole-2-ca rboxylic acid) is a novel radioligand which binds with high affinity, Kd = 2.5 nM, to the glycine site of adult rodent forebrain, N-methyl-D-aspartate subtype of glutamate receptors. As with other glycine site antagonists, the major determinants for high-affinity binding of [3H]MDL 105,519 resides upon the NRI subunit, and not the NR2 subunits. [3H]MDL 105,519 binds with equal affinity, Kd = 3 nM, to both NR1-1a or NR1-4b splice variants, as well as the NRI-1a/NR2A receptor expressed in human embryonic kidney (HEK) 293 cells. One percent Triton X-100/1 M NaCl solubilises with a recovery of 15+/-3%, a mixed pool of assembled and unassembled forebrain NR1 subunit polypeptides. In this preparation, the recovery of [3H]MK801 ((+)-5-[3H]methyl-10,11-dihydrodibenzo[alpha,d]cyclohepten-5 ,10-imine binding activity (7+/-1%) reflects the amount of assembled NR1 subunits whereas [3H]MDL 105,519 binds quantitatively, with a recovery of 19+/-4% and Kd = 3 nM, to both assembled and unassembled NRI subunits. Therefore, [3H]MDL 105,519 should prove a useful ligand, in conjunction with immunopurification approaches, to address the question of NMDA receptor subunit stoichiometry.
Chazot
P L
PL
Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, London, UK.
Reiss
C
C
Chopra
B
B
Stephenson
F A
FA
D000818:Animals; D002460:Cell Line; D018691:Excitatory Amino Acid Antagonists / Q000378:metabolism*; D006801:Humans; D007211:Indoles / Q000378:metabolism*; D008024:Ligands; D008566:Membranes; D017830:Octoxynol; D016548:Prosencephalon / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012995:Solubility
D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D008024:Ligands; C101788:MDL 105519; D018009:Receptors, Glycine; D016194:Receptors, N-Methyl-D-Aspartate; D011994:Recombinant Proteins; D017830:Octoxynol