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Cys loop receptor

Daniel T Baptista-Hon, Simona Gulbinaite, Tim G Hales
The modification of Cys residues (substituted for D43 and T47) by 2-aminoethyl methanethiosulfonate in the GABAA α1 subunit loop G impairs activation of α1β2γ2 receptors by GABA and propofol (Baptista-Hon et al. 4). While the T47C substitution had no significant effect, non-conservative substitution of either residue (D43C and T47R) reduced the apparent potency of GABA. Propofol (1 μm), which potentiates sub-maximal, but not maximal GABA-evoked currents mediated by α1β2γ2 receptors, also potentiated maximal currents mediated by α1(D43C)β2γ2 and α1(T47R)β2γ2 receptors...
December 16, 2016: Journal of Physiology
Brian T Welsh, Jelena Todorovic, Dean Kirson, Hunter M Allen, Michelle D Bayly, S John Mihic
Partial agonists have lower efficacies than compounds considered 'full agonists', eliciting submaximal responses even at saturating concentrations. Taurine is a partial agonist at the glycine receptor (GlyR), a member of the cys-loop ligand-gated ion channel superfamily. The molecular mechanisms responsible for agonism are not fully understood but evidence suggests that efficacy at these receptors is determined by conformational changes that occur early in the process of receptor activation. We previously identified a residue located near the human α1 glycine binding site (aspartate-97; D97) that, when mutated to arginine (D97R), results in GlyR channels opening spontaneously with a high open probability, mimicking the effects of saturating glycine concentrations on wildtype GlyR...
December 3, 2016: Brain Research
Constanza Alcaino, Maria Musgaard, Teresa Minguez, Simone Mazzaferro, Manuel Faundez, Patricio Iturriaga-Vasquez, Philip C Biggin, Isabel Bermudez
Allosteric modulators of pentameric ligand gated ion channels (pLGICs) are thought to act on elements of the pathways that couple agonist binding to channel gating. Using α4β2 nicotinic acetylcholine receptors (nAChRs) and the α4β2-selective positive modulators 17β-estradiol (βEST) and desformylflustrabromine (dFBr), we have identified pathways that link the binding sites for these modulators to the Cys loop, a region that is critical for channel gating in all pLGICs. Previous studies have shown that the binding site for potentiating βEST is in the C-terminal (post-M4 region) of the α4 subunit...
November 18, 2016: Journal of Biological Chemistry
Anna E Lohning, Wolfgang Marx, Liz Isenring
Gingerols and shogaols are the primary non-volatile actives within ginger (Zingiber officinale). These compounds have demonstrated in vitro to exert 5-HT3 receptor antagonism which could benefit chemotherapy-induced nausea and vomiting (CINV). The site and mechanism of action by which these compounds interact with the 5-HT3 receptor is not fully understood although research indicates they may bind to a currently unidentified allosteric binding site. Using in silico techniques, such as molecular docking and GRID analysis, we have characterized the recently available murine 5-HT3 receptor by identifying sites of strong interaction with particular functional groups at both the orthogonal (serotonin) site and a proposed allosteric binding site situated at the interface between the transmembrane region and the extracellular domain...
November 2016: Journal of Molecular Graphics & Modelling
Mieke Nys, Eveline Wijckmans, Ana Farinha, Özge Yoluk, Magnus Andersson, Marijke Brams, Radovan Spurny, Steve Peigneur, Jan Tytgat, Erik Lindahl, Chris Ulens
Pentameric ligand-gated ion channels or Cys-loop receptors are responsible for fast inhibitory or excitatory synaptic transmission. The antipsychotic compound chlorpromazine is a widely used tool to probe the ion channel pore of the nicotinic acetylcholine receptor, which is a prototypical Cys-loop receptor. In this study, we determine the molecular determinants of chlorpromazine binding in the Erwinia ligand-gated ion channel (ELIC). We report the X-ray crystal structures of ELIC in complex with chlorpromazine or its brominated derivative bromopromazine...
October 25, 2016: Proceedings of the National Academy of Sciences of the United States of America
Seika Takayanagi-Kiya, Keming Zhou, Yishi Jin
Presynaptic ligand-gated ion channels (LGICs) have long been proposed to affect neurotransmitter release and to tune the neural circuit activity. However, the understanding of their in vivo physiological action remains limited, partly due to the complexity in channel types and scarcity of genetic models. Here we report that C. elegans LGC-46, a member of the Cys-loop acetylcholine (ACh)-gated chloride (ACC) channel family, localizes to presynaptic terminals of cholinergic motor neurons and regulates synaptic vesicle (SV) release kinetics upon evoked release of acetylcholine...
October 26, 2016: ELife
Mona A Alqazzaz, Kerry L Price, Sarah C R Lummis
Cys-loop receptors play important roles in signal transduction in multicellular organisms, but similar proteins exist in prokaryotes, the best studied of which is the Gloeobacter ligand-gated ion channel (GLIC). GLIC is activated by protons with 50% activation (pH50) at pH 5.5, and while a histidine residue in its pore-forming α-helix (M2) is known to be involved in gating, there is also evidence of a proton-sensitive region in the extracellular domain. However, this proton-sensitive region does not appear to be located in the region of GLIC equivalent to the agonist binding site in related proteins...
October 14, 2016: Biochemistry
Claudio L Morales-Perez, Colleen M Noviello, Ryan E Hibbs
Nicotinic acetylcholine receptors are ligand-gated ion channels that mediate fast chemical neurotransmission at the neuromuscular junction and have diverse signalling roles in the central nervous system. The nicotinic receptor has been a model system for cell-surface receptors, and specifically for ligand-gated ion channels, for well over a century. In addition to the receptors' prominent roles in the development of the fields of pharmacology and neurobiology, nicotinic receptors are important therapeutic targets for neuromuscular disease, addiction, epilepsy and for neuromuscular blocking agents used during surgery...
October 20, 2016: Nature
Andrew D Powell, Gillian Grafton, Alexander Roberts, Shannon Larkin, Nathanael O'Neill, Josephine Palandri, Reka Otvos, Alison J Cooper, Chris Ulens, Nicholas M Barnes
BACKGROUND AND PURPOSE: The 5-HT3 receptor is a prototypical member of the Cys-loop ligand-gated ion channel (LGIC) superfamily and an established therapeutic target. In addition to activation via the orthosteric site, receptor function can be modulated by allosteric ligands. We have investigated the pharmacological action of Cl-indole upon the 5-HT3 A receptor and identified that this positive allosteric modulator possesses a novel mechanism of action for LGICs. EXPERIMENTAL APPROACH: The impact of Cl-indole upon the 5-HT3 receptor was assessed using single cell electrophysiological recordings and [(3) H]-granisetron binding in HEK293 cells stably expressing the 5-HT3 receptor...
December 2016: British Journal of Pharmacology
Prashant Kumar, Anisha Ashokan, Gopala Krishna Aradhyam
BACKGROUND: Human APJ receptor (APJR), a rhodopsin family G-Protein Coupled Receptor (GPCR), activated by isoforms of peptide ligand apelin causing potent inotropic effect, is involved in cardiac function, angiogenesis and maintenance of fluid homeostasis. APJR is expressed in various organs e.g., heart, brain, kidney, muscles, etc. Hence, problems in APJR signaling lead to severe dysregulation in the pathophysiology of an organism. METHODS: Based on multiple sequence alignment of receptors from various organisms, we observe a large number of conserved residues in the extracellular side...
December 2016: Biochimica et Biophysica Acta
Akash Pandhare, Aneesh Satya Pappu, Henrik Wilms, Michael Paul Blanton, Michaela Jansen
The FDA-approved antidepressant and smoking cessation drug bupropion is known to inhibit dopamine and norepinephrine reuptake transporters, as well as nicotinic acetylcholine receptors (nAChRs) which are cation-conducting members of the Cys-loop superfamily of ion channels, and more broadly pentameric ligand-gated ion channels (pLGICs). In the present study, we examined the ability of bupropion and its primary metabolite hydroxybupropion to block the function of cation-selective serotonin type 3A receptors (5-HT3ARs), and further characterized bupropion's pharmacological effects at these receptors...
February 2017: Neuropharmacology
Hongxia Liu, Andrew S French, Päivi H Torkkeli
The spider, Cupiennius salei, central and peripheral nervous system transcriptomes have 15 Cys-loop receptor subunits and an acetylcholine binding protein (AChBP). Twelve subunits are predicted to form anion channels gated by γ-aminobutyric acid (GABA), glutamate, histamine or changes in pH, and three are putative ACh gated cation channels. Spiders have a variety of mechanosensilla and proprioceptive organs that are innervated by efferents in their peripherally located parts, and efferents also innervate muscle fibers...
September 21, 2016: Journal of Comparative Neurology
Dinesh C Indurthi, Trevor M Lewis, Philip K Ahring, Thomas Balle, Mary Chebib, Nathan L Absalom
The α4β2 nicotinic acetylcholine receptor (nAChR) is the most abundant subtype in the brain and exists in two functional stoichiometries: (α4)3(β2)2 and (α4)2(β2)3. A distinct feature of the (α4)3(β2)2 receptor is the biphasic activation response to the endogenous agonist acetylcholine, where it is activated with high potency and low efficacy when two α4-β2 binding sites are occupied and with low potency/high efficacy when a third α4-α4 binding site is occupied. Further, exogenous ligands can bind to the third α4-α4 binding site and potentiate the activation of the receptor by ACh that is bound at the two α4-β2 sites...
2016: PloS One
G Faure, I V Shelukhina, D Porowinska, M A Shulepko, E N Lyukmanova, D A Dolgikh, E N Spirova, I E Kasheverov, Yu N Utkin, J-P Corringer, V I Tsetlin
With the use of surface plasmon resonance (SPR) it was shown that ws-Lynx1, a water-soluble analog of the three-finger membrane-bound protein Lynx1, that modulates the activity of brain nicotinic acetylcholine receptors (nAChRs), interacts with the acetylcholine-binding protein (AChBP) with high affinity, K D = 62 nM. This result agrees with the earlier demonstrated competition of ws-Lynx1 with radioiodinated α-bungarotoxin for binding to AChBP. For the first time it was shown that ws-Lynx1 binds to GLIC, prokaryotic Cys-loop receptor (K D = 1...
May 2016: Doklady. Biochemistry and Biophysics
Clara Stead, Adam Brown, Cathryn Adams, Sarah J Nickolls, Gareth Young, Juha Kammonen, David Pryde, Darren Cawkill
Glycine receptor 3 (GlyRα3) is a ligand-gated ion channel of the cys-loop family that plays a key role in mediating inhibitory neurotransmission and regulation of pain signaling in the dorsal horn. Potentiation of GlyRα3 function is therefore of interest as a putative analgesic mechanism with which to target new therapeutics. However, to date, positive allosteric modulators (PAMs) of this receptor with sufficient selectivity to enable target validation studies have not been described. To address this lack of pharmacological tools, we developed a suite of in vitro assays comprising a high-throughput fluorescent membrane potential screen and a medium-throughput electrophysiology assay using IonFlux HT together with conventional manual patch clamp...
July 7, 2016: Journal of Biomolecular Screening
Carlos F Burgos, Gonzalo E Yévenes, Luis G Aguayo
Glycine receptors (GlyR) are inhibitory Cys-loop ion channels that contribute to the control of excitability along the central nervous system (CNS). GlyR are found in the spinal cord and brain stem, and more recently they were reported in higher regions of the CNS such as the hippocampus and nucleus accumbens. GlyR are involved in motor coordination, respiratory rhythms, pain transmission, and sensory processing, and they are targets for relevant physiologic and pharmacologic modulators. Several studies with protein crystallography and cryoelectron microscopy have shed light on the residues and mechanisms associated with the activation, blockade, and regulation of pentameric Cys-loop ion channels at the atomic level...
September 2016: Molecular Pharmacology
Tommy S Tillman, Frances J D Alvarez, Nathan J Reinert, Chuang Liu, Dawei Wang, Yan Xu, Kunhong Xiao, Peijun Zhang, Pei Tang
Human Cys-loop receptors are important therapeutic targets. High-resolution structures are essential for rational drug design, but only a few are available due to difficulties in obtaining sufficient quantities of protein suitable for structural studies. Although expression of proteins in E. coli offers advantages of high yield, low cost, and fast turnover, this approach has not been thoroughly explored for full-length human Cys-loop receptors because of the conventional wisdom that E. coli lacks the specific chaperones and post-translational modifications potentially required for expression of human Cys-loop receptors...
August 26, 2016: Journal of Biological Chemistry
Roshan Puthenkalam, Marcel Hieckel, Xenia Simeone, Chonticha Suwattanasophon, Roman V Feldbauer, Gerhard F Ecker, Margot Ernst
Atomic resolution structures of cys-loop receptors, including one of a γ-aminobutyric acid type A receptor (GABAA receptor) subtype, allow amazing insights into the structural features and conformational changes that these pentameric ligand-gated ion channels (pLGICs) display. Here we present a comprehensive analysis of more than 30 cys-loop receptor structures of homologous proteins that revealed several allosteric binding sites not previously described in GABAA receptors. These novel binding sites were examined in GABAA receptor homology models and assessed as putative candidate sites for allosteric ligands...
2016: Frontiers in Molecular Neuroscience
Heather D Snell, Eric B Gonzales
Guanidine compounds act as ion channel modulators. In the case of Cys-loop receptors, the guanidine compound amiloride antagonized the heteromeric GABA-A, glycine, and nicotinic acetylcholine receptors. However, amiloride exhibits characteristics consistent with a positive allosteric modulator for the human GABA-A (hGABA-A) ρ1 receptor. Site-directed mutagenesis revealed that the positive allosteric modulation was influenced by the GABA-A ρ1 second transmembrane domain 15' position, a site implicated in ligand allosteric modulation of Cys-loop receptors...
November 2016: Channels
Nuriya Mukhtasimova, Corrie J B daCosta, Steven M Sine
The acetylcholine receptor (AChR) from vertebrate skeletal muscle initiates voluntary movement, and its kinetics of activation are crucial for maintaining the safety margin for neuromuscular transmission. Furthermore, the kinetic mechanism of the muscle AChR serves as an archetype for understanding activation mechanisms of related receptors from the Cys-loop superfamily. Here we record currents through single muscle AChR channels with improved temporal resolution approaching half an order of magnitude over our previous best...
July 2016: Journal of General Physiology
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