Influence of a threonine residue in the S2 ligand binding domain in determining agonist potency and deactivation rate of recombinant NR1a/NR2D NMDA receptors. / Chen, P. E.; Johnston, A. R.; Mok, M. H.; Schoepfer, R.; Wyllie, D. J.

In: Journal of Physiology, Vol. 558, No. Pt 1, 2004, p. 45-58.

Research output: Contribution to journalArticlepeer-review

Published
  • P. E. Chen
  • A. R. Johnston
  • M. H. Mok
  • R. Schoepfer
  • D. J. Wyllie

Abstract

NR1/NR2D NMDA receptors display unusually slow deactivation kinetics which may be critical for their role as extrasynaptic receptors. A threonine to alanine point mutation has been inserted at amino acid position 692 of the NR2D subunit (T692A). Recombinant NR1a/NR2D(T692A) NMDA receptors have been expressed in Xenopus laevis oocytes and their pharmacological and single-channel properties examined using two-electrode voltage-clamp and patch-clamp recording techniques. Glutamate dose-response curves from NR1a/NR2D(T692A) receptor channels produced an approximately 1600-fold reduction in glutamate potency compared to wild-type NR1a/NR2D receptors. There was no change in Hill slopes or gross reduction in mean maximal currents recorded in oocytes expressing either wild-type or mutant receptors. The mutation did not affect the potency of the co-agonist glycine. The shifts in potency produced by NR2D(T692A) containing receptors when activated by other glutamate-site agonists such as aspartate or NMDA were 30- to 60-fold compared to wild-type. Single-channel conductance levels of NR1a/NR2D(T692A) mutant receptors were indistinguishable from wild-type NR2D-containing channels. Additionally NR1a/NR2D(T692A) receptors showed the transitional asymmetry that is characteristic of NR2D-containing NMDA receptors. Rapid applications of glutamate on outside-out patches containing NR1a/NR2D(T692A) receptors produced macroscopic current deactivations that were about 60-fold faster than wild-type NR1a/NR2D receptors. Our results suggest that this conserved threonine residue plays a crucial role in ligand binding to NMDA NR2 receptor subunits and supports the idea that the slow decay kinetics associated with NR1a/NR2D NMDA receptors can be explained by the slow dissociation of glutamate from this NMDA receptor subtype.
Original languageEnglish
Pages (from-to)45-58
Number of pages14
JournalJournal of Physiology
Volume558
Issue numberPt 1
Publication statusPublished - 2004

ID: 1143934