Modulation by zinc ions of native rat and recombinant human inhibitory glycine receptors.

Laube, Bodo; Kuhse, Jochen; Rundström, N.; Kirsch, Joachim; Schmieden, Volker; Betz, Heinrich

doi:10.1113/jphysiol.1995.sp020610

Cited by 165 publications

(178 citation statements)

References 18 publications

(28 reference statements)

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“…As demonstrated previously, the ␣ WT GlyR is highly sensitive to zinc inhibition. As expected from previous studies employing mutations at these positions (7,15,16,29), none of these mutations had dramatic effects on the glycine EC 50 , n H , or I max values. The inhibitory zinc dose responses for the ␣ H107A GlyR, the ␣ H109A GlyR, the double mutant ␣ H107A,H109A GlyR, and the co-expressed (␣ H107A ϩ ␣ H109A ) GlyR were measured in the presence of an EC 20 glycine concentration.…”

Section: Homology Modeling Indicates That Hissupporting

confidence: 59%

“…Several lines of evidence suggest that the glycine receptor chloride channel (GlyR), 1 which mediates inhibitory neurotransmission in the spinal cord and brainstem (6), may be a physiological target for zinc modulation. First, zinc exerts potent effects on the GlyR; low concentrations (0.01-10 M) potentiate glycinergic currents by increasing the apparent glycine affinity, whereas higher concentrations (Ͼ10 M) inhibit the current by reducing the apparent glycine affinity (7). Second, an ultrastructural study has found evidence for zinc and glycine co-localization in individual presynaptic terminals in the spinal cord (8).…”

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confidence: 99%

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Insights into the Structural Basis for Zinc Inhibition of the Glycine Receptor

Nevin

Cromer

Haddrill

et al. 2003

Journal of Biological Chemistry

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Histidines 107 and 109 in the glycine receptor (GlyR) ␣ 1 subunit have previously been identified as determinants of the inhibitory zinc-binding site. Based on modeling of the GlyR ␣ 1 subunit extracellular domain by homology to the acetylcholine-binding protein crystal structure, we hypothesized that inhibitory zinc is bound within the vestibule lumen at subunit interfaces, where it is ligated by His 107 from one subunit and His 109 from an adjacent subunit. This was tested by co-expressing ␣ 1 subunits containing the H107A mutation with ␣ 1 subunits containing the H109A mutation. Although sensitivity to zinc inhibition is markedly reduced when either mutation is individually incorporated into all five subunits, the GlyRs formed by the co-expression of H107A mutant subunits with H109A mutant subunits exhibited an inhibitory zinc sensitivity similar to that of the wild type ␣ 1 homomeric GlyR. This constitutes strong evidence that inhibitory zinc is coordinated at the interface between adjacent ␣ 1 subunits. No evidence was found for ␤ subunit involvement in the coordination of inhibitory zinc, indicating that a maximum of two zincbinding sites per ␣ 1 ␤ receptor is sufficient for maximal zinc inhibition. Our data also show that two zinc-binding sites are sufficient for significant inhibition of ␣ 1 homomers. The binding of zinc at the interface between adjacent ␣ 1 subunits could restrict intersubunit movements, providing a feasible mechanism for the inhibition of channel activation by zinc.

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Section: Homology Modeling Indicates That Hissupporting

confidence: 59%

mentioning

confidence: 99%

Insights into the Structural Basis for Zinc Inhibition of the Glycine Receptor

Nevin

Cromer

Haddrill

et al. 2003

Journal of Biological Chemistry

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“…For heterologous expression of NR1/NR3A receptors, 25 ng of cRNA was injected at an NR1/NR3 ratio of 1:2 into Xenopus laevis oocytes. Oocytes were isolated and maintained as detailed previously (36). Two-electrode voltage clamp recording of whole-cell currents was performed at holding potentials of Ϫ70 mV according to Laube et al (36).…”

Section: Methodsmentioning

confidence: 99%

Supralinear potentiation of NR1/NR3A excitatory glycine receptors by Zn ²⁺ and NR1 antagonist

Madry

Betz

Geiger

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Coassembly of the glycine-binding NMDA receptor subunits NR1 and NR3A results in excitatory glycine receptors of low efficacy. Here, we report that micromolar concentrations of the divalent cation Zn 2؉ produce a 10-fold potentiation of NR1/NR3A receptor responses, which resembles that seen upon antagonizing glycine binding to the NR1 subunit. Coapplication of both Zn 2؉ and NR1 antagonist caused a supralinear potentiation, resulting in a >120-fold increase of glycine-activated currents. At concentrations >50 M, Zn 2؉ alone generated receptor currents with similar efficacy as glycine, implying that NR1/NR3A receptors can be activated by different agonists. Point mutations in the NR1 and NR3A glycinebinding sites revealed that both the potentiating and agonistic effects of Zn 2؉ are mediated by the ligand-binding domain of the NR1 subunit. In conclusion, Zn 2؉ acts as a potent positive modulator and agonist at the NR1 subunit of NR1/NR3A receptors. Our results suggest that this unconventional member of the NMDA receptor family may in vivo be gated by the combined action of glycine and Zn 2؉ or a yet unknown second ligand.binding site ͉ ligand-gated ion channel ͉ NMDA receptor ͉ zinc N -methyl-D-aspartate receptors represent a complex family of the tetrameric ionotropic glutamate receptors that have attracted substantial interest because of their unique pharmacology and role in synaptic plasticity and memory formation (1, 2). The diversity of NMDA receptor subtypes derives from a multitude of receptor subunits, which are encoded by seven different genes that have been classified into three subfamilies (NR1, NR2A-D, and NR3A and NR3B) (3). Each subunit shares a common modular design characterized by the extracellular (i) N-terminal domain (NTD), (ii) the S1S2 ligand binding domain (LBD), (iii) an intramembrane region that forms the ion channel, and (iv) an extended intracellular C-terminal tail (4).Conventional NMDA receptors are composed of two glycinebinding NR1 subunits and two glutamate-binding NR2 subunits each (5) and are efficiently activated upon simultaneous binding of both glutamate and glycine (6). Coexpression of the glycinebinding NR3A or NR3B subunit with NR1 and NR2 subunits generates heteromeric receptors composed of NR1, NR2, and NR3 subunits, which also require glutamate and glycine for gating but exhibit altered biophysical properties (7-10). In contrast, recombinant NMDA receptors assembled from two NR1 and two NR3 subunits (11) do not respond to glutamate but are exclusively activated by glycine (''excitatory glycine receptors''; ref. 12). The glycine currents produced by these NR1/NR3 receptors are, however, rather small, although assembly and surface insertion occur with similar efficiency as that of conventional NR1/NR2 receptors (13). Recently, antagonists of the NR1 glycine-binding site were found to markedly enhance the glycine responses of NR1/NR3 receptors (13,14), presumably by preventing rapid receptor desensitization caused by glycine binding to the NR1 subunit.An important endogenou...

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“…For example, zinc depresses I gly in rat cerebellar granular cells (Virginio and Cherubini 1997) and rat septal cholinergic neurons (Kumamoto and Murata 1996). However, zinc modulation of I gly in rat embryonic spinal cord, human GlyR ␣1 and GlyR ␣2 expressed in HEK 293 cells and Xenopus oocytes (Bloomenthal et al 1994;Laube et al 1995) and isolated retinal cells (Han and Wu 1999) is bidirectional, eliciting facilitation and depression depending on the zinc concentration.…”

Section: Zinc Modulation Of Hippocampal Glyrsmentioning

confidence: 99%

“…Several studies show that GlyRs in forebrain regions are modulated by zinc. For example, zinc depresses I gly in cerebellar neurons (Virginio and Cherubini 1997) and septal cholinergic neurons (Kumamoto and Murata 1996), but bidirectionally modulates (facilitates as well as depresses) I gly , depending on the zinc concentration, in spinal cord neurons (Bloomenthal et al 1994;Laube et al 1995) and retinal ganglion cells (Han and Wu 1999). We sought to determine whether native GlyRs in hippocampus are modulated by zinc and to investigate whether the modulation of I gly by zinc is similar or different to the well-characterized zinc modulation of I NMDA .…”

Section: Bidirectional Modulation Of Hippocampal Glyrs By Zincmentioning

confidence: 99%

Pharmacological Characterization of Glycine-Gated Chloride Currents Recorded in Rat Hippocampal Slices

Chattipakorn

McMahon

2002

Journal of Neurophysiology

141

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Chattipakorn, Siriporn C. and Lori L. McMahon. Pharmacological characterization of glycine-gated chloride currents recorded in rat hippocampal slices. J Neurophysiol 87: 1515-1525, 2002; 10.1152/jn. 00365.2001. An inhibitory role for strychnine-sensitive glycine-gated chloride channels (GlyRs) in mature hippocampus has been overlooked, largely due to the misconception that GlyR expression ceases early during development and to few functional studies demonstrating their presence. As a result, little is known regarding the physiological and pharmacological properties of native GlyRs expressed by hippocampal neurons. In this study, we used pharmacological tools and whole cell patch-clamp recordings of CA1 pyramidal cells and interneurons in acutely prepared hippocampal slices from 3-to 4-wk old rats to characterize these understudied receptors. We show that glycine application to recorded pyramidal cells and interneurons elicited strychnine-sensitive chloride-mediated currents (I gly ) that did not completely desensitize in the continued presence of agonist but reached a steady state at 45-60% of the peak amplitude. Additionally, the inhibitory amino acid, taurine, which has been shown to activate GlyRs in other systems, activated GlyRs expressed by both pyramidal cells and interneurons, although with much less potency than glycine, having an EC 50 10-fold higher. To examine the potential subunit composition of hippocampal GlyRs, we tested the effect of the GABA A receptor antagonist, picrotoxin, on I gly recorded from both cell types. At low micromolar concentrations of picrotoxin (Յ100 M), which selectively block ␣ homomeric GlyRs, I gly was partially attenuated in both cell types, indicating that ␣ homomeric receptors are expressed by pyramidal cells and interneurons. At picrotoxin concentrations Յ1 mM, ϳ10 -20% of the whole cell current remained, suggesting that ␣␤ heteromeric GlyRs are also expressed because this subtype of GlyR is relatively resistant to picrotoxin antagonism. Finally, we examined whether hippocampal GlyRs are modulated by zinc. Consistent with previous reports in other preparations, zinc elicited a bidirectional modulation of GlyRs, with physiological zinc concentrations (1-100 M) increasing whole cell currents and concentrations Ͼ100 M depressing them. Furthermore, the same concentration of zinc that potentiates I gly suppressed currents mediated by the N-methyl-D-aspartate subtype of the glutamate receptor. Thus we provide a pharmacological characterization of native GlyRs expressed by both major neuron types in hippocampus and show that these receptors can be activated by taurine, an amino acid that is highly concentrated in hippocampus. Furthermore, our data suggest that at least two GlyR subtypes are present in hippocampus and that GlyR-mediated currents can be potentiated by zinc at concentrations that suppress glutamate-mediated excitability.

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Modulation by zinc ions of native rat and recombinant human inhibitory glycine receptors.

Cited by 165 publications

References 18 publications

Insights into the Structural Basis for Zinc Inhibition of the Glycine Receptor

Insights into the Structural Basis for Zinc Inhibition of the Glycine Receptor

Supralinear potentiation of NR1/NR3A excitatory glycine receptors by Zn ²⁺ and NR1 antagonist

Pharmacological Characterization of Glycine-Gated Chloride Currents Recorded in Rat Hippocampal Slices

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Modulation by zinc ions of native rat and recombinant human inhibitory glycine receptors.

Cited by 165 publications

References 18 publications

Insights into the Structural Basis for Zinc Inhibition of the Glycine Receptor

Insights into the Structural Basis for Zinc Inhibition of the Glycine Receptor

Supralinear potentiation of NR1/NR3A excitatory glycine receptors by Zn 2+ and NR1 antagonist

Pharmacological Characterization of Glycine-Gated Chloride Currents Recorded in Rat Hippocampal Slices

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Supralinear potentiation of NR1/NR3A excitatory glycine receptors by Zn ²⁺ and NR1 antagonist