Site within<i>N</i>-Methyl-d-aspartate Receptor Pore Modulates Channel Gating

Chen, Nansheng; Li, Bo; Murphy, Timothy H.; Raymond, Lynn A.

doi:10.1124/mol.65.1.157

Cited by 28 publications

(22 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As shown in Fig. 5, A and B, we found, somewhat unexpectedly but similar to previously reported results (24), that the mutations, especially N616Q, made the resulting receptors more sensitive to agonists. The mean EC 50 values for glutamate and glycine were 0.19 and 0.33 µM (N616Q) and 1.1 and 0.73 µM (N616R), respectively.…”

Section: +supporting

confidence: 91%

Direct Inhibition of N-Methyl-D-Aspartate (NMDA)-Receptor Function by Antiglaucomatous β-Antagonists

et al. 2008

View full text Add to dashboard Cite

Abstract. In the present study, we investigated the direct effects of antiglaucoma drugs (timolol, betaxolol, pilocarpine, and latanoprost) on N-methyl-D-aspartate (NMDA)-receptor function using a Xenopus oocytes expression system and electrophysiological techniques. In oocytes expressing wild-type NMDA (NR1a / NR2A) receptors, timolol and betaxolol significantly inhibited glutamate-evoked currents, whereas less inhibition was obtained with pilocarpine, and latanoprost had few effects. Moreover, the effect of timolol and betaxolol was noncompetitive with respect to glutamate. Mutations that changed Asn616 of the NR1a subunit, a critical residue for Mg 2+ blocking of NMDA receptors, to Arg (N616R) or Gln (N616Q) almost eliminated the inhibitory effects of timolol and betaxolol, as well as the blocking effect of Mg 2+. Experiments were also carried out to examine the protective effects of timolol and betaxolol against death of oocytes expressing NMDA receptors. During incubation of oocytes, especially in Mg 2+ -free medium, cell death was induced by addition of glutamate because of the continuous activation of the NMDA receptors expressed. Timolol and betaxolol significantly improved oocyte viability when they were added during the incubation period. These results suggest that timolol and betaxolol may have an additional role that they directly inhibit NMDA-receptor function, possibly via N616 of the NR1a subunit.

show abstract

Section: +supporting

confidence: 91%

Direct Inhibition of N-Methyl-D-Aspartate (NMDA)-Receptor Function by Antiglaucomatous β-Antagonists

et al. 2008

View full text Add to dashboard Cite

show abstract

“…These regions include the LIVBP-like domain, the pre-M1 region, the lurcher site in the third transmembrane domain, and a methionine (Met823) in the fourth transmembrane domain (Krupp et al, 1998;Villarroel et al, 1998;Kohda et al, 2000;Zheng et al, 2001;Ren et al, 2003). Similar results have been obtained by introducing mutations in the P-loop (Asn598) or the lurcher site of NR1 (Kohda et al, 2000;Chen et al, 2004). The pre-M1 region of NR2A is a particularly attractive candidate for coupling ligand binding to channel gating because it links the glutamate-binding S1 domain to the channel.…”

supporting

confidence: 61%

ProbingN-Methyl-d-aspartate Receptor Desensitization with the Substituted-Cysteine Accessibility Method

Thomas¹,

Krupp²,

Bagley³

et al. 2005

Mol Pharmacol

View full text Add to dashboard Cite

Several forms of macroscopic N-methyl-D-aspartate (NMDA) receptor desensitization affect the amplitude and duration of postsynaptic responses. In addition to its functional significance, desensitization provides one means to examine the conformational coupling of ligand binding to channel gating. Segments flanking the ligand binding domain in the extracellular N terminus of the NMDA receptor NR2 subunit influence the glycine-independent form of desensitization. The NR2A pre-M1 region, the linker between the glutamate binding domain and the channel pore, plays a critical role in desensitization. Thus, we used the substituted-cysteine accessibility method to scan the accessibility of residues in the pre-M1 region and the first transmembrane domain (M1) of NR2A. Cysteine mutants were expressed with NR1 in human embryonic kidney 293 cells and were assayed by whole-cell recording. With activation of the receptor by glutamate and glycine, only a single mutant, V557C, which is located at the beginning of M1, led to irreversible inhibition by the methanethiosulfonate derivative methanethiosulfonate ethyltrimethylammonium (MTSET). The NR2 ligand glutamate was insufficient on its own to induce modification of V557C by MTSET, suggesting that the change in accessibility required channel gating. The rate of MTSET modification of the homologous residue on NR1 (NR1-1a L562C / NR2A) was much slower than V557C. We also substituted cysteine in the V557 site of mutant subunits that exhibit either enhanced or reduced desensitization. Modification by MTSET correlated with the degree of desensitization for these subunits, suggesting that V557C is a sensitive detector of desensitization gating.The kinetics of NMDA receptors play an important role in shaping postsynaptic responses (Lester and Jahr, 1992;Jones and Westbrook, 1996;Qian and Johnson, 2002). Although intrinsically silent, desensitized states can have significant actions on receptor gating (Jones and Westbrook, 1996). NMDA receptor desensitization can be divided into three forms with distinct underlying mechanisms: calciumdependent, glycine-dependent, and glycine-independent (McBain and Mayer, 1994). Depending on the kinetics, desensitization can either accelerate or prolong the duration of a synaptic response. We focus here on the glycine-independent form. NMDA receptor channels are believed to desensitize directly from the closed, agonist-bound state (Colquhoun and Hawkes, 1995); thus, glycine-independent desensitization represents a separate closed, bound conformation. This form of desensitization contributes to the decay of excitatory postsynaptic currents and reduces NMDA receptor-mediated responses during high-frequency synaptic stimulation (Lester and Jahr, 1992). Thus, understanding the conformational changes associated with desensitization is ultimately important for understanding synaptic signaling.NMDA receptors are tetramers composed of two glycinebinding NR1 and two glutamate binding NR2 (A-D) sub-

show abstract

“…In spite of the minor increase in glutamate potency, the rise time of glutamate-activated currents was slower in the presence of NR1(R), indicating that NR1(R) probably did not increase the glutamate binding rate. A concurrently performed study on recombinant NR1(R)/NR2A receptors observed very similar changes on kinetics and glutamate potency (Chen et al 2004). In this study, a kinetic model explained the leftward shift in the glutamate dose-response curve by a about 10-fold reduction in the channel closing rate, even without any modification in ligand binding and unbinding rates.…”

Section: Figure 1 I-v Relationships Of Nmda Currents Under Physiologsupporting

confidence: 50%

Impaired synaptic scaling in mouse hippocampal neurones expressing NMDA receptors with reduced calcium permeability

Pawlak

Schupp

Single

et al. 2005

The Journal of Physiology

View full text Add to dashboard Cite

NMDA receptors (NMDARs) play a crucial role for the acquisition of functional AMPARs duringHebbian synaptic plasticity at cortical and hippocampal synapses over a short timescale of seconds to minutes. In contrast, homeostatic synaptic plasticity can occur over longer timescales of hours to days. The induction mechanisms of this activity-dependent synaptic scaling are poorly understood but are assumed to be independent of NMDAR signalling in the cortex. Here we investigated in the hippocampus a potential role of NMDAR-mediated Ca 2+ influx for synaptic scaling of AMPA currents by genetic means. The Ca 2+ permeability of NMDARs was reduced by selective postnatal expression in principal neurones of mouse forebrain half of the NR1 subunits with an amino acid substitution at the critical channel site (N598R). This genetic manipulation did not reduce the total charge transfer via NMDARs in nucleated patches (somatic) and at synaptic sites. In contrast, the current amplitude and the charge carried through AMPARs were substantially reduced at somatic and synaptic sites in juvenile and adult mutants, indicating persistent downscaling of AMPA responses. Smaller and less frequent AMPA miniature currents in the mutant demonstrated a postsynaptic locus of this down-regulation. Afferent innervation and release probability were unchanged at CA3-to-CA1 synapses of mutants, as judged from input-output and minimal stimulation experiments. Our results indicate that NMDAR-mediated Ca 2+ signalling is important for synaptic scaling of AMPA currents in the hippocampus in vivo.

show abstract

Site withinN-Methyl-d-aspartate Receptor Pore Modulates Channel Gating

Cited by 28 publications

References 38 publications

Direct Inhibition of N-Methyl-D-Aspartate (NMDA)-Receptor Function by Antiglaucomatous β-Antagonists

Direct Inhibition of N-Methyl-D-Aspartate (NMDA)-Receptor Function by Antiglaucomatous β-Antagonists

ProbingN-Methyl-d-aspartate Receptor Desensitization with the Substituted-Cysteine Accessibility Method

Impaired synaptic scaling in mouse hippocampal neurones expressing NMDA receptors with reduced calcium permeability

Contact Info

Product

Resources

About