A residue in the middle of the M2‐M3 loop of the β<sub>4</sub> subunit specifically affects gating of neuronal nicotinic receptors

Rovira, José Carlos; Ballesta, Juan J.; Vicente-Agullo, Francisco; Campos‐Caro, Antonio; Criado, Manuel; Sala, Francisco; Sala, Salvador

doi:10.1016/s0014-5793(98)00889-8

Cited by 34 publications

(41 citation statements)

References 25 publications

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“…As the expression of native and mutated receptors at the oocyte surface was similar, the alteration in macroscopic currents produced by the mutation could be due to an impairment of the coupling between agonist binding and channel activation or modification of single channel properties. It was not possible to rule out any of these possibilities given that no single channel currents of mutated receptors could be detected, although in R3 4 receptors measurements of single channel currents are feasible (15).…”

Section: Resultsmentioning

confidence: 99%

Multiple Roles of the Conserved Key Residue Arginine 209 in Neuronal Nicotinic Receptors

et al. 2001

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We have examined the role of a highly conserved arginine (R209), which flanks the M1 transmembrane segment of nAChRs, in the biogenesis and function of neuronal nAChRs. Point mutations revealed that, in alphaBgtx-sensitive neuronal alpha7 nAChRs, the conserved arginine is required for the transport of assembled receptors to the cell surface. By contrast, R209 does not play any role in the transport of assembled alpha-Bgtx-insensitive neuronal alpha3beta4 nAChRs to the cell surface. However, a basic residue at this position of alpha3 and beta4 subunits is necessary for either synthesis, folding, or assembly of alpha3beta4 receptors. Moreover, electrophysiological experiments revealed that in alpha3beta4 receptors the conserved arginine of the alpha3 subunit is involved in either coupling agonist binding to the channel or regulating single channel kinetics.

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Section: Resultsmentioning

confidence: 99%

Multiple Roles of the Conserved Key Residue Arginine 209 in Neuronal Nicotinic Receptors

et al. 2001

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“…In principle, such effects could result from structural alterations to the glycine-binding site or to the receptor gating mechanism. However, because strong evidence implicates the M2-M3 loop as a transduction element (Kusama et al, 1994;Rajendra et al, 1995a;Campos-Caro et al, 1996;Lynch et al, 1997;Fisher and Macdonald, 1998;Lewis et al, 1998;Rovira et al, 1998Rovira et al, , 1999Grosman et al, 2000a,b), it is likely that MTS modification primarily affects the gating mechanism. If so, the increase in ligand affinity indicates a bias in the conformational equilibrium toward the high-affinity activated state.…”

Section: Effects Of Covalent Modificationmentioning

confidence: 99%

“…From this it was inferred that the loops were components of the receptor gating process. Recent evidence from the nicotinic acetylcholine receptor cation channel (Campos-Caro et al, 1996;Rovira et al, 1998Rovira et al, , 1999Grosman et al, 2000a,b), the GABA c receptor Cl Ϫ channel (Kusama et al, 1994), and the GABA A receptor Cl Ϫ channel (Fisher and Macdonald, 1998; suggests that this domain also comprises a gating control element in other members of the ligand-gated ion channel superfamily. By demonstrating that the surface accessibility of the M2-M3 loop is increased in the glycine-bound state, the present study provides evidence for an external conformational change that accompanies channel activation and places constraints on structural models of ligand-gated ion channels.…”

Section: Comparison With Other Studiesmentioning

confidence: 99%

The Surface Accessibility of the Glycine Receptor M2–M3 Loop Is Increased in the Channel Open State

et al. 2001

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Mutations in the extracellular M2-M3 loop of the glycine receptor (GlyR) ␣1 subunit have been shown previously to affect channel gating. In this study, the substituted cysteine accessibility method was used to investigate whether a structural rearrangement of the M2-M3 loop accompanies GlyR activation. All residues from R271C to V277C were covalently modified by both positively charged methanethiosulfonate ethyltrimethylammonium (MTSET) and negatively charged methanethiosulfonate ethylsulfonate (MTSES), implying that these residues form an irregular surface loop. The MTSET modification rate of all residues from R271C to K276C was faster in the glycine-bound state than in the unliganded state. MTSES modification of A272C, L274C, and V277C was also faster in the glycine-bound state. These results demonstrate that the surface accessibility of the M2-M3 loop is increased as the channel transitions from the closed to the open state, implying that either the loop itself or an overlying domain moves during channel activation.

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“…Our laboratory previously used this approach to demonstrate a glycine-induced increase in the surface exposure of six continuous residues (Arg 271 -Lys 276 ) in the GlyR M2-M3 linker domain (14). These residues lie mid-way between the binding site and the activation gate (7), and it is now well established that they experience a conformational change that is crucial for the activation of GlyRs (14 -18), ␥-aminobutyric acid, type A receptors (19 -24), and nAChRs (7,(25)(26)(27). A structural study of the Torpedo nAChR has shown recently (4) that these residues form an extramembranous extension to the M2 ␣-helix.…”

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Comparison of Taurine- and Glycine-induced Conformational Changes in the M2-M3 Domain of the Glycine Receptor

Han

Clements

Lynch

2004

Journal of Biological Chemistry

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In the ionotropic glutamate receptor, the global conformational changes induced by partial agonists are smaller than those induced by full agonists. However, in the pentameric ligand-gated ion channel receptor family, the structural basis of partial agonism is not understood. This study investigated whether full and partial agonists induce different conformation changes in the glycine receptor chloride channel (GlyR). A substituted cysteine accessibility analysis demonstrated previously that glycine binding induced an increase in surface accessibility of all residues from Arg 271 to Lys 276 in the M2-M3 domain of the homomeric ␣1 GlyR. Here we compare the surface accessibility changes induced by the full agonist, glycine, and the partial agonist, taurine. In GlyRs incorporating the A272C, S273C, L274C, or P275C mutation, the reaction rate of the cysteine-specific compound, methanethiosulfonate ethyltrimethylammonium, depended on how strongly the receptors were activated but was agonist-independent. Reaction rates could not be compared in the R271C and K276C mutant GlyRs because methanethiosulfonate ethyltrimethylammonium did not modify the extremely small currents induced by saturating taurine or equivalent low glycine concentrations. The results indicate that bound taurine and glycine molecules impose identical conformational changes to the M2-M3 domain. We therefore conclude that the higher efficacy of glycine is due to an increased ability to stabilize a common activated configuration.The glycine receptor chloride channel (GlyR) 1 mediates fast inhibitory neurotransmission in the vertebrate central nervous system (1, 2). It belongs to the family of pentameric ligandgated ion channels (LGICs) that includes the nicotinic acetylcholine receptor (nAChR) as its prototypical member (3). Each subunit incorporates a large N-terminal extracellular domain and four ␣-helical membrane-spanning domains. The second membrane-spanning (M2) domains curve radially so as to form a tapering, water-filled pore with a hydrophobic barrier (or channel gate) at either its mid-point (4) or intracellular boundary (5). The N-terminal domains contain the agonist-binding sites and a disulfide loop that is an invariant feature of LGIC receptors (6). Agonists binding in the N-terminal domain initiate conformational changes that propagate as a wave toward the channel gate (7). Different agonists induce these conformational changes with different efficacies (where efficacy is the ability of an agonist to open the channel once bound to the receptor). If the efficacy of an agonist is sufficiently low, it will behave as a partial agonist (8). The structural basis of differential agonist efficacy is not yet understood for any member of the LGIC family.Partial agonism could be caused by one, or a combination, of the following two sharply contrasting mechanisms. First, it is possible that different agonists induce different structural changes throughout the protein. A clear example of this has been characterized recently (9 -11) in the ionotropic g...

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A residue in the middle of the M2‐M3 loop of the β₄ subunit specifically affects gating of neuronal nicotinic receptors

Cited by 34 publications

References 25 publications

Multiple Roles of the Conserved Key Residue Arginine 209 in Neuronal Nicotinic Receptors

Multiple Roles of the Conserved Key Residue Arginine 209 in Neuronal Nicotinic Receptors

The Surface Accessibility of the Glycine Receptor M2–M3 Loop Is Increased in the Channel Open State

Comparison of Taurine- and Glycine-induced Conformational Changes in the M2-M3 Domain of the Glycine Receptor

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A residue in the middle of the M2‐M3 loop of the β4 subunit specifically affects gating of neuronal nicotinic receptors

Cited by 34 publications

References 25 publications

Multiple Roles of the Conserved Key Residue Arginine 209 in Neuronal Nicotinic Receptors

Multiple Roles of the Conserved Key Residue Arginine 209 in Neuronal Nicotinic Receptors

The Surface Accessibility of the Glycine Receptor M2–M3 Loop Is Increased in the Channel Open State

Comparison of Taurine- and Glycine-induced Conformational Changes in the M2-M3 Domain of the Glycine Receptor

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A residue in the middle of the M2‐M3 loop of the β₄ subunit specifically affects gating of neuronal nicotinic receptors