Point mutation of glycine receptor α1 subunit in the <i>spasmodic</i> mouse affects agonist responses

Saul, Brigitta; Schmieden, Volker; Kling, Claudia; Mülhardt, Cornel; Gass, Peter; Kuhse, Jochen; Becker, Cord‐Michael

doi:10.1016/0014-5793(94)00736-5

Cited by 98 publications

(98 citation statements)

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“…We propose that conformational changes occur in the spasmodic loop and Cys-loop of the GlyR upon ligand binding that are an important part of the process linking ligand binding to channel gating. This is consistent with the previous demonstration that the spasmodic mutation results in impaired receptor gating but does not affect ligand binding (19,20), and the M2-M3 linker is involved in channel gating (12)(13)(14).…”

Section: Discussionsupporting

confidence: 93%

“…Loop 2 is also a flexible loop, which in a LGIC receptor subunit is proposed to be in a position to interact with the transmembrane domains. Alignment of the AChBP and GlyR ␣1-subunit sequences shows that loop 2 corresponds to the location of the A52S mutation in spasmodic mice (19,20). The effect of this mutation is to impair the GlyR activation (19,20), resulting in an exaggerated startle phenotype, which suggests that loop 2 might also be involved in gating of the GlyR.…”

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confidence: 99%

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Role of Charged Residues in Coupling Ligand Binding and Channel Activation in the Extracellular Domain of the Glycine Receptor

Absalom

Lewis

Kaplan

et al. 2003

Journal of Biological Chemistry

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The glycine receptor is a member of the ligand-gated ion channel receptor superfamily that mediates fast synaptic transmission in the brainstem and spinal cord. Following ligand binding, the receptor undergoes a conformational change that is conveyed to the transmembrane regions of the receptor resulting in the opening of the channel pore. Using the acetylcholine-binding protein structure as a template, we modeled the extracellular domain of the glycine receptor ␣1-subunit and identified the location of charged residues within loops 2 and 7 (the conserved Cys-loop). These loops have been postulated to interact with the M2-M3 linker region between the transmembrane domains 2 and 3 as part of the receptor activation mechanism. Charged residues were substituted with cysteine, resulting in a shift in the concentration-response curves to the right in each case. Covalent modification with 2-(trimethylammonium) ethyl methanethiosulfonate was demonstrated only for K143C, which was more accessible in the open state than the closed state, and resulted in a shift in the EC 50 toward wild-type values. Charge reversal mutations (E53K, D57K, and D148K) also impaired channel activation, as inferred from increases in EC 50 values and the conversion of taurine from an agonist to an antagonist in E53K and D57K. Thus, each of the residues Glu-53, Asp-57, Lys-143, and Asp-148 are implicated in channel gating. However, the double reverse charge mutations E53K:K276E, D57K:K276E, and D148K:K276E did not restore glycine receptor function. These results indicate that loops 2 and 7 in the extracellular domain play an important role in the mechanism of activation of the glycine receptor although not by a direct electrostatic mechanism.Fast synaptic transmission in the central nervous system is mediated by members of the ligand-gated ion channel (LGIC) 1 receptor superfamily. The glycine receptor (GlyR) is a member of the nicotinic-like LGIC superfamily that includes the nicotinic acetylcholine (nAChR), serotonin type 3 (5-HT 3 R), and ␥-aminobutyric acid (GABA A R) receptors (1, 2). Each of these receptors are pentameric complexes arranged around a central ion conducting pore. Individual subunits share a similar membrane topology, with hydropathy analysis predicting a large extracellular domain at the N terminus and four putative transmembrane domains (M1-M4) (1). A key characteristic of these receptors is the integral ion channel that is opened following ligand binding. The extracellular domain contains the ligand binding site, which is spatially separate from the M2 domain that lines the ion channel pore of these receptors (3, 4). While there is an accumulated body of data on the structures involved in ligand binding (2) and the ion channel pore (2-4), relatively little is known about the structures that may link these two spatially separate domains to effect receptor activation.Inherited mutations located in the regions flanking the M2 domain of the GlyR ␣1-subunit are associated with human startle disease (hyperekplexia) (5) and start...

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Section: Discussionsupporting

confidence: 93%

mentioning

confidence: 99%

Role of Charged Residues in Coupling Ligand Binding and Channel Activation in the Extracellular Domain of the Glycine Receptor

Absalom

Lewis

Kaplan

et al. 2003

Journal of Biological Chemistry

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“…The disorder is associated with mutations of the GLRA1 gene (Rees et al, 1994;Becker et al, 2006Becker et al, , 2008, the ␤ subunit gene GLRB , and the gene encoding the glycine transporter GlyT2 (Eulenburg et al, 2006;Rees et al, 2006). The mouse mutants oscillator (Glra1 spd-ot ) Kling et al, 1997) and spasmodic (Glra1 spd ) (Ryan et al, 1994;Saul et al, 1994) carry orthologous mutations in the Glra1 gene, whereas the spastic (Glrb spa ) mouse carries a ␤ subunit mutation (Becker et al, 1992;Kingsmore et al, 1994;Mülhardt et al, 1994). Two weeks after birth, oscillator mice develop a progressively worsening tremor and muscle spasms, resulting in death at the age of 3 weeks Büsselberg et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Functional Complementation ofGlra1^spd-ot, a Glycine Receptor Subunit Mutant, by Independently Expressed C-Terminal Domains

Villmann¹,

Oertel²,

Ma-Högemeier³

et al. 2009

J. Neurosci.

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The oscillator mouse (Glra1 spd-ot ) carries a 9 bp microdeletion plus a 2 bp microinsertion in the glycine receptor ␣1 subunit gene, resulting in the absence of functional ␣1 polypeptides from the CNS and lethality 3 weeks after birth. Depending on differential use of two splice acceptor sites in exon 9 of the Glra1 gene, the mutant allele encodes either a truncated ␣1 subunit (spd ot -trc) or a polypeptide with a C-terminal missense sequence (spd ot -elg). During recombinant expression, both splice variants fail to form ion channels. In complementation studies, a tail construct, encoding the deleted C-terminal sequence, was coexpressed with both mutants. Coexpression with spd ot -trc produced glycine-gated ion channels. Rescue efficiency was increased by inclusion of the wild-type motif RRKRRH. In cultured spinal cord neurons from oscillator homozygotes, viral infection with recombinant C-terminal tail constructs resulted in appearance of endogenous ␣1 antigen. The functional rescue of ␣1 mutants by the C-terminal tail polypeptides argues for a modular subunit architecture of members of the Cys-loop receptor family.

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“…Homozygous spasmodic mice have a missense mutation in the α1 subunit gene that reduces the sensitivity, but minimally affects the number, of glycine receptors (Ryan et al 1994;Saul et al 1994;Graham et al 2006). The phenotype of affected homozygous mice includes light tremor at rest and increased tremor during movements, clenching of rear legs when suspended by the tail, an impaired righting reflex when placed on their backs and a tendency to walk with an arched back and extended wrist and ankle joints.…”

Section: Subjectsmentioning

confidence: 99%

Glycine Receptor Deficiency and Its Effect on the Horizontal Vestibulo-ocular Reflex: a Study on the SPD1J Mouse

Hübner

Lim

Brichta

et al. 2013

JARO

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Inhibition is critical in the pathways controlling the vestibulo-ocular reflex (VOR) and plays a central role in the precision, accuracy and speed of this important vestibular-mediated compensatory eye movement. While γ-aminobutyric acid is the common fast inhibitory neurotransmitter in most of the VOR microcircuits, glycine is also found in key elements. For example, the omnidirectional pause neurons (OPNs) and inhibitory burst neurons in the horizontal VOR both use glycine as their preferred inhibitory neurotransmitter. Determining the precise contribution of glycine to the VOR pathway has been difficult due to the lack of selective tools; however, we used spasmodic mice that have a naturally occurring defect in the glycine receptor (GlyR) that reduces glycinergic transmission. Using this animal model, we compared the horizontal VOR in affected animals with unaffected controls. Our data showed that initial latency and initial peak velocity as well as slow-phase eye movements were unaffected by reduced glycinergic transmission. Importantly however, there were significant effects on quick-phase activity, substantially reducing their number (30-70 %), amplitude (~55 %) and peak velocity (~38 %). We suggest that the OPNs were primarily responsible for the reduced quick-phase properties, since they are part of an unmodifiable, or more 'hard-wired', microcircuit. In contrast, the effects of reduced glycinergic transmission on slowphases were likely ameliorated by the intrinsically modifiable nature of this pathway. Our results also suggested there is a 'threshold' in GlyR-affected animals, below which the effects of reduced glycinergic transmission were undetected.

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Point mutation of glycine receptor α1 subunit in the spasmodic mouse affects agonist responses

Cited by 98 publications

References 32 publications

Role of Charged Residues in Coupling Ligand Binding and Channel Activation in the Extracellular Domain of the Glycine Receptor

Role of Charged Residues in Coupling Ligand Binding and Channel Activation in the Extracellular Domain of the Glycine Receptor

Functional Complementation ofGlra1^spd-ot, a Glycine Receptor Subunit Mutant, by Independently Expressed C-Terminal Domains

Glycine Receptor Deficiency and Its Effect on the Horizontal Vestibulo-ocular Reflex: a Study on the SPD1J Mouse

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Point mutation of glycine receptor α1 subunit in the spasmodic mouse affects agonist responses

Cited by 98 publications

References 32 publications

Role of Charged Residues in Coupling Ligand Binding and Channel Activation in the Extracellular Domain of the Glycine Receptor

Role of Charged Residues in Coupling Ligand Binding and Channel Activation in the Extracellular Domain of the Glycine Receptor

Functional Complementation ofGlra1spd-ot, a Glycine Receptor Subunit Mutant, by Independently Expressed C-Terminal Domains

Glycine Receptor Deficiency and Its Effect on the Horizontal Vestibulo-ocular Reflex: a Study on the SPD1J Mouse

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Functional Complementation ofGlra1^spd-ot, a Glycine Receptor Subunit Mutant, by Independently Expressed C-Terminal Domains