Chloride Ions in the Pore of Glycine and GABA Channels Shape the Time Course and Voltage Dependence of Agonist Currents

Moroni, Mirko; Bíró, István; Giugliano, Michèle; Vijayan, Ranjit; Biggin, Philip C.; Beato, Marco; Sivilotti, Lucia G.

doi:10.1523/jneurosci.1985-11.2011

Cited by 40 publications

(44 citation statements)

References 56 publications

(84 reference statements)

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“…It has been recently demonstrated that intracellular chloride ions bind to specific sites in the GABA A R pore affecting the receptor gating2122. Our observations further extend the hypothesis that [Cl − ] i acts as a intracellular messenger exerting a feedback control on GABA A currents not only by interfering with GABA A R gating, but also by modulating the expression of GABA A R subunits.…”

Section: Discussionsupporting

confidence: 83%

Intracellular chloride concentration influences the GABAA receptor subunit composition

Succol

Fiumelli²,

Benfenati

et al. 2012

Nat Commun

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GABAA receptors (GABAARs) exist as different subtype variants showing unique functional properties and defined spatio-temporal expression pattern. The molecular mechanisms underlying the developmental expression of different GABAAR are largely unknown. The intracellular concentration of chloride ([Cl−]i), the main ion permeating through GABAARs, also undergoes considerable changes during maturation, being higher at early neuronal stages with respect to adult neurons. Here we investigate the possibility that [Cl−]i could modulate the sequential expression of specific GABAARs subtypes in primary cerebellar neurons. We show that [Cl−]i regulates the expression of α3-1 and δ-containing GABAA receptors, responsible for phasic and tonic inhibition, respectively. Our findings highlight the role of [Cl−]i in tuning the strength of GABAergic responses by acting as an intracellular messenger.

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Section: Discussionsupporting

confidence: 83%

Intracellular chloride concentration influences the GABAA receptor subunit composition

Succol

Fiumelli²,

Benfenati

et al. 2012

Nat Commun

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“…This phenomenon was absent in other patches. In wild-type receptors, the amplitude of this fast sag is correlated to the magnitude of the current (Pitt et al, 2008), suggesting it is an artifact related either to channel density effects on desensitization (Legendre et al, 2002) or to changes in chloride gradient (Moroni et al, 2011).…”

Section: Methodsmentioning

confidence: 99%

The α1K276E Startle Disease Mutation Reveals Multiple Intermediate States in the Gating of Glycine Receptors

Lape

Plested²,

Moroni³

et al. 2012

J. Neurosci.

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Loss-of-function mutations in human glycine receptors cause hyperekplexia, a rare inherited disease associated with an exaggerated startle response. We have studied a human disease mutation in the M2-M3 loop of the glycine receptor ␣1 subunit (K276E) using direct fitting of mechanisms to single-channel recordings with the program HJCFIT. Whole-cell recordings from HEK293 cells showed the mutation reduced the receptor glycine sensitivity. In single-channel recordings, rat homomeric ␣1 K276E receptors were barely active, even at 200 mM glycine. Coexpression of the ␤ subunit partially rescued channel function. Heteromeric mutant channels opened in brief bursts at 300 M glycine (a concentration that is near-maximal for wild type) and reached a maximum one-channel open probability of about 45% at 100 mM glycine (compared to 96% for wild type). Distributions of apparent open times contained more than one component in high glycine and, therefore, could not be described by mechanisms with only one fully liganded open state. Fits to the data were much better with mechanisms in which opening can also occur from more than one fully liganded intermediate (e.g., "primed" models). Brief pulses of glycine (ϳ3 ms, 30 mM) applied to mutant channels in outside-out patches activated currents with a slower rise time (1.5 ms) than those of wild-type channels (0.2 ms) and a much faster decay. These features were predicted reasonably well by the mechanisms obtained from fitting single-channel data. Our results show that, by slowing and impairing channel gating, the K276E mutation facilitates the detection of closed reaction intermediates in the activation pathway of glycine channels.

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“…time course and decay half time of desensitization underlie large cell-to-cell variability (20) due to many different parameters that may influence the kinetics, such as ligand concentration (16), the phosphorylation state of the intracellular TM3-TM4 loop (16,20), or the membrane potential (1,21,22). GlyR are basically selective for Cl Ϫ but also permeable to other anions and even to cations (23)(24)(25)(26)(27)(28).…”

mentioning

confidence: 99%

Electrophysiological Signature of Homomeric and Heteromeric Glycine Receptor Channels

Raltschev

Hetsch

Winkelmann

et al. 2016

Journal of Biological Chemistry

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Glycine receptors are chloride-permeable, ligand-gated ion channels and contribute to the inhibition of neuronal firing in the central nervous system or to facilitation of neurotransmitter release if expressed at presynaptic sites. Recent structure-function studies have provided detailed insights into the mechanisms of channel gating, desensitization, and ion permeation. However, most of the work has focused only on comparing a few isoforms, and among studies, different cellular expression systems were used. Here, we performed a series of experiments using recombinantly expressed homomeric and heteromeric glycine receptor channels, including their splice variants, in the same cellular expression system to investigate and compare their electrophysiological properties. Our data show that the current-voltage relationships of homomeric channels formed by the ␣2 or ␣3 subunits change upon receptor desensitization from a linear to an inwardly rectifying shape, in contrast to their heteromeric counterparts. The results demonstrate that inward rectification depends on a single amino acid (Ala 254 ) at the inner pore mouth of the channels and is closely linked to chloride permeation. We also show that the current-voltage relationships of glycine-evoked currents in primary hippocampal neurons are inwardly rectifying upon desensitization. Thus, the alanine residue Ala 254 determines voltage-dependent rectification upon receptor desensitization and reveals a physio-molecular signature of homomeric glycine receptor channels, which provides unprecedented opportunities for the identification of these channels at the single cell level.

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Chloride Ions in the Pore of Glycine and GABA Channels Shape the Time Course and Voltage Dependence of Agonist Currents

Cited by 40 publications

References 56 publications

Intracellular chloride concentration influences the GABAA receptor subunit composition

Intracellular chloride concentration influences the GABAA receptor subunit composition

The α1K276E Startle Disease Mutation Reveals Multiple Intermediate States in the Gating of Glycine Receptors

Electrophysiological Signature of Homomeric and Heteromeric Glycine Receptor Channels

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