The Arrangement and Functions of the Chains of the Acetylcholine Receptor of Torpedo Electric Tissue

Karlin, Arthur; Cox, Robert N.; Kaldany, Rashad‐Rudolf J.; Lobel, Peter; Holtzman, Eric

doi:10.1101/sqb.1983.048.01.003

Cited by 45 publications

(27 citation statements)

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“…The subunit average qS (6) for g(-90)/g(+30) is nearly zero, with four positive and four negative values; but the four most voltage-sensitive combinations involving 6M also involve t~M, and the four least voltage-sensitive combinations involving ~M also involve /3T. This/3-6 interaction is consistent with the suggestion that the/3 and 6 subunits contact each other in the receptor oligomer (Karlin et al, 1983).…”

Section: Blockade By D-tubocurarine Is Roughly As Expectedsupporting

confidence: 74%

Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes.

Yoshii

Mayne

et al. 1987

The Journal of General Physiology

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A B S T R A C T This study used messenger RNA encoding each subunit (a, fl, % and 6) of the nicotinic acetylcholine (ACh) receptor from mouse BC3H-1 cells and from Torpedo electric organ. The mRNA was synthesized in vitro by transcription with SP6 polymerase from cDNA clones. All 16 possible combinations that include one mRNA for each of a, fl, % and ~ were injected into oocytes. After allowing 2-8 d for translation and assembly, we assayed each oocyte for (a) receptor assembly, measured by the binding of [12sI]a-bungarotoxin to the oocyte surface, and (b) ACh-induced conductance, measured under voltage clamp at various membrane potentials. All combinations yielded detectable assembly (30-fold range among different combinations) and ACh-induced conductances (>l,000-fold range at 1 #M). On double-logarithmic coordinates, the dose-response relations all had a slope near 2 for low concentrations of ACh. Data were corrected for variations in efficiency of translation among identically injected oocytes by expressing ACh-induced conductance per femtomole of a-bungarotoxin-binding sites. Five combinations were tested for dtubocurarine inhibition by the dose-ratio method; the apparent dissociation constant ranged from 0.08 to 0.27 #M. Matched responses and geometric means are used for describing the effects of changing a particular subunit (mouse vs. Torpedo) while maintaining the identity of the other subunits. A dramatic subunit-specific effect is that of the fl subunit on voltage sensitivity of the response: gACh(--90 mV)/gAch(+30 mV) is always at least 1, but this ratio increases by an average of 3.5-fold if fl~a replaces fiT. Also, combinations including "YT or 6M usually produce greater receptor assembly than combinations including the homologous subunit from the other species. Finally, EACh is defined as the concentration of ACh inducing 1 #S/fmol at -60 mV; EACh is consistently lower for am. We conclude that receptor assembly, voltage sensitivity, and EACh are governed by different properties.

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Section: Blockade By D-tubocurarine Is Roughly As Expectedsupporting

confidence: 74%

Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes.

Yoshii

Mayne

et al. 1987

The Journal of General Physiology

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“…The elucidation of the subunit arrangement in the ␣ 4 ␤ 3 ␦ subtype provides an opportunity to develop similar models for this receptor subtype, the importance of which in the control of neuronal excitability is becoming increasingly recognized (Farrant and Nusser, 2005). As for the ␣ 1 ␤ 2 ␥ 2 GABA A receptor (Baumann et al, 2002;Baur et al, 2006), the Torpedo californica nicotinic receptor (Karlin et al, 1983) and the 5-HT 3 receptor (Barrera et al, 2005a), the subunits of the ␣ 4 ␤ 3 ␦ receptor are apparently arranged in a preferred order to produce an assembled receptor. In contrast, it is possible to change the subunit stoichiometry of the ␣ 4 ␤ 2 nicotinic receptor (Zwart and Vijverberg, 1998;Nelson et al, 2003) and the trimeric P2X 2/6 receptor heteromer (Barrera et al, 2007) by manipulating subunit expression levels.…”

Section: Discussionmentioning

confidence: 99%

Atomic Force Microscopy Reveals the Stoichiometry and Subunit Arrangement of the α₄β₃δ GABA_AReceptor

Barrera

Betts

You³

et al. 2007

Mol Pharmacol

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The GABA A receptor is a chloride-selective ligand-gated ion channel of the Cys-loop superfamily. The receptor consists of five subunits arranged pseudosymmetrically around a central pore. The predominant form of the receptor in the brain contains ␣ 1 -, ␤ 2 -, and ␥ 2 -subunits in the arrangement ␣␤␣␥␤, counter-clockwise around the pore. GABA A receptors containing ␦-instead of ␥-subunits, although a minor component of the total receptor population, have interesting properties, such as an extrasynaptic location, high sensitivity to GABA, and potential association with conditions such as epilepsy. They are therefore attractive targets for drug development. Here we addressed the subunit arrangement within the ␣ 4 ␤ 3 ␦ form of the receptor. Different epitope tags were engineered onto the three subunits, and complexes between receptors and anti-epitope antibodies were imaged by atomic force microscopy. Determination of the numbers of receptors doubly decorated by each of the three antibodies revealed a subunit stoichiometry of 2␣:2␤:1␦. The distributions of angles between pairs of antibodies against the ␣-and ␤-subunits both had peaks at around 144°, indicating that these pairs of subunits were nonadjacent. Decoration of the receptor with ligands that bind to the extracellular domain (i.e., the lectin concanavalin A and an antibody that recognizes the ␤-subunit N-terminal sequence) showed that the receptor preferentially binds to the mica extracellular face down. Given this orientation, the geometry of complexes of receptors with both an antibody against the ␦-subunit and Fab fragments against the ␣-subunits indicates a predominant subunit arrangement of ␣␤␣␦␤, counter-clockwise around the pore when viewed from the extracellular space.

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“…The stoichiometry of the neuromuscular nAChR was the first to be determined, and revealed that four different subunits formed a functional pentameric receptor with the stoichiometry a 2 bcd (Karlin et al 1983). Determining the stoichiometry of other receptors has proved to be more problematic, as there are large numbers of subunits that could potentially contribute (e.g.…”

Section: Subunit Stoichiometrymentioning

confidence: 99%

The structural basis of function in Cys-loop receptors

Thompson

Lester

Lummis

2010

Quart. Rev. Biophys.

326

398

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Abstract. Cys-loop receptors are membrane-spanning neurotransmitter-gated ion channels that are responsible for fast excitatory and inhibitory transmission in the peripheral and central nervous systems. The best studied members of the Cys-loop family are nACh, 5-HT 3 , GABA A and glycine receptors. All these receptors share a common structure of five subunits, pseudo-symmetrically arranged to form a rosette with a central ion-conducting pore. Some are cation selective (e.g. nACh and 5-HT 3 ) and some are anion selective (e.g. GABA A and glycine). Each receptor has an extracellular domain (ECD) that contains the ligand-binding sites, a transmembrane domain (TMD) that allows ions to pass across the membrane, and an intracellular domain (ICD) that plays a role in channel conductance and receptor modulation. Cys-loop receptors are the targets for many currently used clinically relevant drugs (e.g. benzodiazepines and anaesthetics). Understanding the molecular mechanisms of these receptors could therefore provide the catalyst for further development in this field, as well as promoting the development of experimental techniques for other areas of neuroscience.In this review, we present our current understanding of Cys-loop receptor structure and function. The ECD has been extensively studied. Research in this area has been stimulated in recent years by the publication of high-resolution structures of nACh receptors and related proteins, which have permitted the creation of many Cys loop receptor homology models of this region. Here, using the 5-HT 3 receptor as a typical member of the family, we describe how homology modelling and ligand docking can provide useful but not definitive information about ligand interactions. We briefly consider some of the many Cys-loop receptors modulators. We discuss the current understanding of the structure of the TMD, and how this links to the ECD to allow channel gating, and consider the roles of the ICD, whose structure is poorly understood. We also describe some of the current methods that are beginning to reveal the differences between different receptor states, and may ultimately show structural details of transitions between them.

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The Arrangement and Functions of the Chains of the Acetylcholine Receptor of Torpedo Electric Tissue

Cited by 45 publications

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Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes.

Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes.

Atomic Force Microscopy Reveals the Stoichiometry and Subunit Arrangement of the α₄β₃δ GABA_AReceptor

The structural basis of function in Cys-loop receptors

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The Arrangement and Functions of the Chains of the Acetylcholine Receptor of Torpedo Electric Tissue

Cited by 45 publications

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Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes.

Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes.

Atomic Force Microscopy Reveals the Stoichiometry and Subunit Arrangement of the α4β3δ GABAAReceptor

The structural basis of function in Cys-loop receptors

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Atomic Force Microscopy Reveals the Stoichiometry and Subunit Arrangement of the α₄β₃δ GABA_AReceptor