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Glycine receptor antibodies have been identified in a few patients with progressive encephalomyelitis with rigidity and myoclonus (PERM), a highly disabling disorder characterised by rigidity, spasm and brainstem symptomatology. The clinical characteristics of patients with glycine receptor antibodies have not yet been fully described and it is not clear whether GlyR-Abs are pathogenic or just an epiphenomenon. This study examined the clinical features and immunotherapy responses of 45 patients; characterised the GlyR-Ab pathogenicity, subunit specificity and binding to different brain region in vitro, and examined mice injected with GlyR-Abs to model the disease in vivo. Most of the patients were classified as PERM but some patients had symptomatology beyond the classical motor manifestations and there were four patients with tumours (thymomas and lymphomas). GlyR-Ab titres were varied in serum and CSF, but there was intrathecal synthesis in the six patients with suitable samples. Most patients were very disabled but almost all showed excellent responses to immunotherapies. The antibodies were mainly IgG1 and IgG3 subclasses, activated complement on glycine receptor-transfected HEK cells at room temperature, and caused internalisation and lysosomal degradation of the glycine receptors at 37°C. GlyR-Abs bound to rodent spinal cord and brainstem co-localising with monoclonal antibodies to GlyRα1 on the surface of neurons. GlyR-IgG injected intra-peritoneally led to impairment in forced walking ability, sensorimotor function and coordination. Analysis of the brain showed that animals injected with patients' IgG, but not control IgG, had antibodies bound to the brainstem, spinal cord, cerebellum and caudate, co-localising with GlyRα1 monoclonal antibody. Intra-cerebroventricular injection of GlyR-IgG caused an anxiety-like behaviour in mice but no evident motor disturbances. These results provide the first evidence of in vitro and in vivo pathogenicity of the GlyR-Abs, supporting the use of long term immunosuppression in these patients to provide them with a good prognosis.

The glycine receptor (GlyR) is a ligand-gated ion channel member of the cys-loop receptor superfamily, responsible for inhibitory neurotransmission in the brain and spinal cord. Both glycine and the partial agonist taurine act as endogenous ligands of the GlyR. Taurine-activated GlyR may have a role in the rewarding effects of drugs of abuse, such as ethanol. As a partial agonist, taurine has a decreased efficacy relative to glycine, resulting in a decreased maximum response. We investigated the effects of ethanol, anesthetics, inhalants, and zinc to determine if these allosteric modulators could increase the efficacy of the taurine-activated GlyR. Whole cell recordings of wild type GlyR revealed that each of the allosteric modulators potentiated currents generated by saturating concentrations of taurine but not glycine, implying an increase in efficacy. Zinc is found at GlyR-potentiating concentrations throughout the nervous system, so we examined the combinatorial effects of these allosteric modulators with zinc to mimic in vivo conditions. Whole cell recordings revealed that zinc potentiation of saturating taurine-generated currents decreased further potentiation by another allosteric modulator, indicating no synergistic effects on efficacy. We next investigated the actions of ethanol and isoflurane on the taurine-activated GlyR at the single channel level, finding that both allosteric modulators stabilized the channel open state, increasing the efficacy of the taurine-activated GlyR. We previously identified a mutation in the ligand-binding domain of the GlyR (D97R) that produces spontaneously activating channels, on which taurine has increased efficacy. We identified a residue, R131, as a possible binding partner of D97 in forming an electrostatic interaction that holds the channel in the closed state. We found that disruption of this interaction results in greatly increased taurine efficacy, indicating that efficacy for partial agonists may be determined by agonist ability to break this bond early in the activation process following binding. Thus we find differential mechanisms of allosteric modulation and efficacy determinations for the GlyR when activated by taurine vs. glycine. / text

The glycine receptor (GlyR) is a ligand-gated ion channel member of the cys-loop receptor superfamily, responsible for inhibitory neurotransmission in the brain and spinal cord. Both glycine and the partial agonist taurine act as endogenous ligands of the GlyR. Taurine-activated GlyR may have a role in the rewarding effects of drugs of abuse, such as ethanol. As a partial agonist, taurine has a decreased efficacy relative to glycine, resulting in a decreased maximum response. We investigated the effects of ethanol, anesthetics, inhalants, and zinc to determine if these allosteric modulators could increase the efficacy of the taurine-activated GlyR. Whole cell recordings of wild type GlyR revealed that each of the allosteric modulators potentiated currents generated by saturating concentrations of taurine but not glycine, implying an increase in efficacy. Zinc is found at GlyR-potentiating concentrations throughout the nervous system, so we examined the combinatorial effects of these allosteric modulators with zinc to mimic in vivo conditions. Whole cell recordings revealed that zinc potentiation of saturating taurine-generated currents decreased further potentiation by another allosteric modulator, indicating no synergistic effects on efficacy. We next investigated the actions of ethanol and isoflurane on the taurine-activated GlyR at the single channel level, finding that both allosteric modulators stabilized the channel open state, increasing the efficacy of the taurine-activated GlyR. We previously identified a mutation in the ligand-binding domain of the GlyR (D97R) that produces spontaneously activating channels, on which taurine has increased efficacy. We identified a residue, R131, as a possible binding partner of D97 in forming an electrostatic interaction that holds the channel in the closed state. We found that disruption of this interaction results in greatly increased taurine efficacy, indicating that efficacy for partial agonists may be determined by agonist ability to break this bond early in the activation process following binding. Thus we find differential mechanisms of allosteric modulation and efficacy determinations for the GlyR when activated by taurine vs. glycine. / text

Short-term synaptic plasticity results from use-dependent activity, lasts on the timescale of milliseconds to minutes, and is thought to underlie working memory and neuronal information processing. Here, we focus on two forms of short-term plasticity: 1) post-tetanic potentiation (PTP), which is induced by high-frequency stimulation, and 2) presynaptic ionotropic receptor-activated synaptic enhancement, which can be produced by the activation of presynaptic glycine receptors. Potentiation of evoked and spontaneous responses is thought to arise from elevations in presynaptic residual Ca2+, which activates one or more molecular targets to increase neurotransmitter release. However, the Ca2+ sensor protein has not yet been identified. The overall goal of this work is to elucidate the Ca2+-dependent mechanisms of short-term plasticity.

Au niveau de la synapse, la liaison des neurotransmetteurs aux récepteurs membranaires induit l’ouverture de canaux ioniques. Le Récepteur de la Glycine (RGly) est un récepteur ionotrope impliqué dans des troubles neuronaux tels que l’addiction, la douleur chronique, ou l’hyperekplexie ; pour cette raison il est important de développer des nouveaux traitements ciblant ce récepteur. Nous avons utilisé des simulations de Dynamiques Moléculaire (DM) et d’électrophysiologie numérique afin d’évaluer la fonction des structures du RGly disponibles et montré qu’aucune d’entre elles ne satisfait les propriétés fonctionnelles de l’état ouvert. Grâce aux simulations de DM, nous avons caractérisé une nouvelle conformation du RGly, qui est compatible avec cet état. Nous avons souligné le rôle majeur des portails latéraux pour la perméation des ions. Nous avons proposé un protocole, nommé pharmacologie dépendante de l’état, pour identifier des molécules modulatrices de protéines allostériques. / Signals within neurons are mostly transmitted through chemical synapses. Signal transduction arises from the binding of neurotransmitters to membrane receptors in order to open ion channels. The Glycine Receptor (GlyR) is an ionotropic receptor which is involved in several neurological disorders such as addiction, chronic pain, or hyperekplexia. Because of its implication in human diseases, it is interesting to design novel drugs targeting this receptor. We used Molecular Dynamics (MD) simulations and computational electrophysiology to probe the function of available GlyR structures. We showed that none of the experimental structures display the physiological behavior of the conductive state. Using MD simulations, we captured a novel conformation of the GlyR compatible with a conductive state and demonstrated the importance of lateral portals for ionic permeation. Lastly, we proposed an original protocol, named state-based pharmacology, to discover modulators of allosteric proteins.

No description available.

No description available.