1
|
Pursuing High-Resolution Structures of Nicotinic Acetylcholine Receptors: Lessons Learned from Five Decades. Molecules 2021; 26:molecules26195753. [PMID: 34641297 PMCID: PMC8510392 DOI: 10.3390/molecules26195753] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/19/2021] [Accepted: 09/20/2021] [Indexed: 01/04/2023] Open
Abstract
Since their discovery, nicotinic acetylcholine receptors (nAChRs) have been extensively studied to understand their function, as well as the consequence of alterations leading to disease states. Importantly, these receptors represent pharmacological targets to treat a number of neurological and neurodegenerative disorders. Nevertheless, their therapeutic value has been limited by the absence of high-resolution structures that allow for the design of more specific and effective drugs. This article offers a comprehensive review of five decades of research pursuing high-resolution structures of nAChRs. We provide a historical perspective, from initial structural studies to the most recent X-ray and cryogenic electron microscopy (Cryo-EM) nAChR structures. We also discuss the most relevant structural features that emerged from these studies, as well as perspectives in the field.
Collapse
|
2
|
Leite JF, Cascio M. Structure of ligand-gated ion channels: critical assessment of biochemical data supports novel topology. Mol Cell Neurosci 2001; 17:777-92. [PMID: 11358478 DOI: 10.1006/mcne.2001.0984] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rapid signaling across the synaptic junction is partially mediated by the ligand-gated ion channel superfamily (LGICS), which includes inhibitory glycine and GABA receptors and excitatory acetylcholine and serotonin receptors. The glycine receptor (GlyR) can assemble as homopentamers of alpha subunits, and baculovirus expression systems are capable of overexpressing large quantities of active receptors. Limited proteolysis coupled to mass spectrometry on reconstituted alpha1 GlyR homopentamers identified proteolytic cleavages within proposed transmembrane domains postulated to fold as bilayer-spanning alpha helices in the "classical" model and identified unexpected membrane-associated regions in the N-terminal domain (J. F. Leite et al., 2000, J. Biol. Chem. 275, 13683-13689). In this review, optimized sequence alignments were used to integrate these proteolysis data with biochemical information determined in studies of all the LGICS members in order to construct a novel topological model.
Collapse
Affiliation(s)
- J F Leite
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | | |
Collapse
|
3
|
Gotter AL, Kaetzel MA, Dedman JR. Electrophorus electricus as a model system for the study of membrane excitability. Comp Biochem Physiol A Mol Integr Physiol 1998; 119:225-41. [PMID: 11253789 DOI: 10.1016/s1095-6433(97)00414-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The stunning sensations produced by electric fish, particularly the electric eel, Electrophorus electricus, have fascinated scientists for centuries. Within the last 50 years, however, electric cells of Electrophorus have provided a unique model system that is both specialized and appropriate for the study of excitable cell membrane electrophysiology and biochemistry. Electric tissue generates whole animal electrical discharges by means of membrane potentials that are remarkably similar to those of mammalian neurons, myocytes and secretory cells. Electrocytes express ion channels, ATPases and signal transduction proteins common to these other excitable cells. Action potentials of electrocytes represent the specialized end function of electric tissue whereas other excitable cells use membrane potential changes to trigger sophisticated cellular processes, such as myofilament cross-bridging for contraction, or exocytosis for secretion. Because electric tissue lacks these functions and the proteins associated with them, it provides a highly specialized membrane model system. This review examines the basic mechanisms involved in the generation of the electrical discharge of the electric eel and the membrane proteins involved. The valuable contributions that electric tissue continues to make toward the understanding of excitable cell physiology and biochemistry are summarized, particularly those studies using electrocytes as a model system for the study of the regulation of membrane excitability by second messengers and signal transduction pathways.
Collapse
Affiliation(s)
- A L Gotter
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, OH 45267-0576, USA
| | | | | |
Collapse
|
4
|
Affiliation(s)
- J Lindstrom
- Department of Neuroscience, Medical School of the University of Pennsylvania, Philadelphia 19104-6074, USA
| |
Collapse
|
5
|
Abstract
The past year has seen remarkable progress in defining the structure of various ligand-gated ion channels. Images of opened and closed nicotinic acetylcholine receptors at 9 A resolution have now made it easier to identify the conformational changes underlying gating. In addition, recent studies on glutamate receptors have led to a radical revision of their postulated transmembrane topology: models for agonist-binding and allosteric domains now use sites previously thought to lie in cytoplasmic loops. Other areas that are being actively pursued include identification of the amino acids lining the ion channels, accurate measurements of Ca2+ fluxes, and tests of transmembrane topology in kainate receptor subunits.
Collapse
Affiliation(s)
- J A Dani
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
| | | |
Collapse
|
6
|
Bennett JA, Dingledine R. Topology profile for a glutamate receptor: three transmembrane domains and a channel-lining reentrant membrane loop. Neuron 1995; 14:373-84. [PMID: 7857646 DOI: 10.1016/0896-6273(95)90293-7] [Citation(s) in RCA: 240] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We investigated the transmembrane topology of the GluR3 subunit that was translated in rabbit reticulocytes supplemented with microsomal membranes. A prolactin reporter epitope was fused to GluR3 at six locations, bracketing each of the proposed transmembrane domains. The sidedness of the epitope in the microsomal membrane was then assessed by proteinase K sensitivity. The N terminus and the entire region between M3 and M4 was extracellular, and the C terminus was intracellular by this method. Four native N-linked glycosylation sites in the amino terminus and one introduced site between M3 and M4 were utilized, confirming the extracellular location of these regions. Epitopes inserted upstream and downstream of M2 were protease sensitive and thus intracellular. Our results support a topological model for glutamate receptor subunits that consists of three transmembrane domains, M1, M3, and M4, and another domain, the proposed channel-lining M2, which forms a reentrant membrane segment with both ends facing the cytoplasm.
Collapse
Affiliation(s)
- J A Bennett
- Department of Pharmacology, Emory University, Atlanta, Georgia 30322
| | | |
Collapse
|
7
|
Abstract
The location, with respect to the membrane, of Lys 165 in the folded beta polypeptide of native nicotinic acetylcholine receptor has been determined by site-directed immunochemistry. Sealed, right-side-out vesicles rich in acetylcholine receptor were modified with pyridoxal phosphate and sodium [3H]-borohydride. Saponin was added to one portion of the vesicles to make them permeable to the pyridoxal phosphate and sodium borohydride; the other portion was modified in the absence of saponin. Both samples were then exhaustively succinylated and digested with trypsin and thermolysin to produce the peptide LDAKGER, which contains Lys beta 165. The digests were passed over an immunoadsorbent specific for peptides with the sequence LDAXGER, where X represents any modified or unmodified amino acid, and specifically bound peptides were eluted with 0.1 M sodium phosphate, pH 2.5. The eluates were submitted to high-pressure liquid chromatography, and two peptides, N epsilon-phospho[3H]pyridoxalLDAKGER and N epsilon-succinylLDAKGER, modified at the epsilon amino group of lysine with pyridoxal phosphate and sodium [3H]-borohydride or succinic anhydride, respectively, were identified by comparison to standards. The relative specific radioactivity of N epsilon-phospho[3H]pyridoxalLDAKGER modified in the presence or absence of saponin, respectively, was 0.9 +/- 0.4. The incorporation of phospho[3H]pyridoxyl groups into Lys alpha 380, a residue located on the cytoplasmic surface of acetylcholine receptor, was also monitored. The relative specific radioactivity of the peptide that contains the modified Lys alpha 380, N epsilon-phospho[3H]pyridoxalGVKYIAE, increased 3.6-fold when the modification was performed in the presence of saponin. This result verifies that the vesicles used in these experiments were sealed and right-side-out. Because the incorporation of [3H]pyridoxyl groups into Lys beta 165 is the same in the presence or absence of saponin, Lys beta 165 must have been located on the outside surface of the sealed, right-side-out vesicles, and therefore on the extracytoplasmic surface of native acetylcholine receptor.
Collapse
Affiliation(s)
- K L Ewalt
- Department of Chemistry, University of California, San Diego, La Jolla 92093-0506
| |
Collapse
|
8
|
Borjigin J, Nathans J. Insertional mutagenesis as a probe of rhodopsin's topography, stability, and activity. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36684-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
9
|
Schröder B, Reinhardt-Maelicke S, Schrattenholz A, McLane K, Kretschmer A, Conti-Tronconi B, Maelicke A. Monoclonal antibodies FK1 and WF6 define two neighboring ligand binding sites on Torpedo acetylcholine receptor alpha-polypeptide. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)34075-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
|
10
|
Narayanaswami V, Kim J, McNamee MG. Protein-lipid interactions and Torpedo californica nicotinic acetylcholine receptor function. 1. Spatial disposition of cysteine residues in the gamma subunit analyzed by fluorescence-quenching and energy-transfer measurements. Biochemistry 1993; 32:12413-9. [PMID: 8241131 DOI: 10.1021/bi00097a020] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The nicotinic acetylcholine receptor from Torpedo californica was labeled with a fluorescent, lipophilic probe, N-(1-pyrenyl)maleimide, specific for sulfhydryls in a hydrophobic environment, and was found to alkylate Cys 416, Cys 420 and Cys 451 in the gamma subunit [Li, L., Schuchard, M., Palma, A., Pradier, L., & McNamee, M.G. (1990) Biochemistry 29, 5428-5436]. The spatial disposition of the acetylcholine receptor-bound pyrene with respect to the membrane bilayer was assessed by a combination of fluorescence-quenching and resonance energy transfer measurements, under conditions of selective labeling of the gamma subunit. Quenching of pyrene fluorescence by spin-labeled fatty acids with the doxyl group at positions C-5 and C-12 revealed that the former was more effective, with a Stern-Volmer quenching constant of 0.187 compared to 0.072 for the latter, suggesting that the fluorophore(s) are located closer to the membrane-water interface rather than the hydrophobic interior. Energy transfer was found to occur from tryptophan in the acetylcholine receptor to cysteine-bound pyrene with a distance of separation of approximately 18 A. However, there was no energy transfer when pyrene-labeled AChR was reconstituted into membranes containing brominated phospholipids and cholesterol, suggesting that the fluorophore(s) responsible for energy transfer are located in the membrane domain. Thus, the N-(1-pyrenyl)maleimide can be used to monitor lipid-protein interactions of the AChR.
Collapse
Affiliation(s)
- V Narayanaswami
- Section of Molecular and Cellular Biology, University of California, Davis 95616
| | | | | |
Collapse
|
11
|
Kusiak JW, Norton DD. A splice variant of the N-methyl-D-aspartate (NMDAR1) receptor. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1993; 20:64-70. [PMID: 8255182 DOI: 10.1016/0169-328x(93)90110-b] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A splice variant of the NMDA receptor (NMDAR1) was discovered containing a deletion of 37 amino acids near the carboxyl tail and has been designated NMDAR1b. The 111 nucleotides corresponding to the deleted amino acid sequence were found in a separate exon bounded by consensus intron/exon junction sequences in rat genomic DNA. A partial restriction map of genomic DNA bounding this region placed the deleted exon approximately 600 base pairs (bp) downstream of the upstream exon. RT/PCR analysis of RNA from different brain regions showed that the deletion variant is more abundantly expressed in the brain stem and cerebellum while the full-length form is expressed more abundantly in the olfactory bulb, striatum, hippocampus, and cortex. Northern analysis of poly(A)+ RNA from different brain regions with probes specific for the deleted exon (i.e., full-length form) and for the splice junction (deletion form) indicated approximately 4.4 kb transcripts. The probe for the deleted exon hybridized to transcripts in olfactory bulb, cortex, striatum, and hippocampus while the splice junction probe hybridized most strongly to transcripts in cerebellum. The results suggest an interesting rostral to caudal shift in the expression of splice variants of the NMDAR1 which may signify important functional differences in native forms of NMDA receptors.
Collapse
Affiliation(s)
- J W Kusiak
- Molecular Neurobiology Unit, National Institute on Aging, NIH, F.S. Key Medical Center, Baltimore, MD 21224
| | | |
Collapse
|
12
|
Anand R, Bason L, Saedi MS, Gerzanich V, Peng X, Lindstrom J. Reporter epitopes: a novel approach to examine transmembrane topology of integral membrane proteins applied to the alpha 1 subunit of the nicotinic acetylcholine receptor. Biochemistry 1993; 32:9975-84. [PMID: 7691173 DOI: 10.1021/bi00089a013] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The development of a novel immunological method called the "reporter epitope" technique to probe the transmembrane topology of integral membrane proteins is described. Using this method, synthetic oligonucleotides encoding epitopes (reporter epitopes) for well characterized monoclonal antibodies (reporter mAbs) were inserted at various locations within the human acetylcholine receptor (AChR) alpha 1 subunit cDNA. The engineered subunits were then expressed along with Torpedo beta 1, gamma, and delta subunits in Xenopus oocytes, and the transmembrane location of the site of insertion was determined by the binding of the 125I-labeled reporter mAbs to whole oocytes. Control reporter epitope insertions at alpha 347 exhibited the expected cytoplasmic location. Reporter epitopes inserted at alpha 429 are located on the extracellular surface. Reporter epitopes that are 16-48 amino acids long do not disrupt assembly or function of hybrid AChRs when inserted near the carboxy terminus (at alpha 429) or in the large cytoplasmic domain (at alpha 347). However, because two reporter epitopes inserted at alpha 157 obliterated subunit assembly and a third reporter epitope when tolerated at this position was inaccessible from the extracellular surface and only marginally accessible after detergent solubilization of the AChRs, a definitive transmembrane location for this region was not possible. Nonetheless, the use of this approach has been successfully demonstrated, and it may be generally applicable to the study of other integral membrane proteins.
Collapse
Affiliation(s)
- R Anand
- Department of Neuroscience, University of Pennsylvania, Philadelphia 19104-6074
| | | | | | | | | | | |
Collapse
|
13
|
Butler DH, McNamee MG. FTIR analysis of nicotinic acetylcholine receptor secondary structure in reconstituted membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1150:17-24. [PMID: 8392868 DOI: 10.1016/0005-2736(93)90116-h] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Using Fourier-transform infrared resonance spectroscopy, we examined the structure of the purified Torpedo californica nicotinic acetylcholine receptor in reconstituted dioleoylphosphatidylcholine membranes in H2O and D2O. Using the amide-I band, we calculated the secondary structure of nAChR in H2O to be approx. 19% alpha-helix, 42% beta-structure, 24% turns and 15% unordered. The secondary structure content in D2O was estimated to be 14% alpha-helix, 37% beta-structure, 29% turns and 20% unordered. In the presence of phosphatidic acid the beta-structure content in D2O increased significantly from 37% to 42%. This suggests that an ionic interaction between negatively-charged lipid head groups and positively-charged peptide side chains may stabilize a beta-structure conformation that is necessary for receptor function. The inclusion of cholesterol in the reconstituted membranes significantly increased the alpha-helix content from 14% to 17%. These results support the hypothesis that cholesterol may induce a transmembrane region to undergo a unordered-to-helix transition which is necessary to maintain the integrity of the ion channel. Additionally, we found that nAChR did not undergo major secondary structure changes when subjected to conditions that induce desensitization. This is consistent with the view that the mechanism of desensitization consists of small quaternary rearrangements of the subunits rather than large changes in receptor secondary structure.
Collapse
Affiliation(s)
- D H Butler
- Department of Biochemistry and Biophysics, University of California, Davis 95616
| | | |
Collapse
|
14
|
Fairclough RH, Josephs R, Richman DP. Imaging ligand binding sites on the Torpedo acetylcholine receptor. Ann N Y Acad Sci 1993; 681:113-25. [PMID: 7689302 DOI: 10.1111/j.1749-6632.1993.tb22878.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- R H Fairclough
- Department of Neurology, University of Chicago, Illinois 60637
| | | | | |
Collapse
|
15
|
Abstract
Nicotinic acetylcholine (ACh) receptors convert the binding of ACh into the opening of a cation-conducting channel. New information about the regions of the receptor most immediately involved in its function, namely the ACh-binding sites, the gate and the channel, has come from two approaches. One is the identification by labelling and by mutagenesis of residues contributing to these regions. Another is the determination of the three-dimensional structure of the receptor by electron microscopy. Although the identification of functionally relevant residues is incomplete and residues cannot yet be resolved in the three-dimensional structure, the two approaches are converging. There is still room in the gap for speculation.
Collapse
Affiliation(s)
- A Karlin
- Center for Molecular Recognition, College of Physicians and Surgeons, Columbia University, New York, NY 10032
| |
Collapse
|
16
|
Krikorian J, Bloch R. Treatments that extract the 43K protein from acetylcholine receptor clusters modify the conformation of cytoplasmic domains of all subunits of the receptor. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50397-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
17
|
McLane KE, Wu X, Lindstrom JM, Conti-Tronconi BM. Epitope mapping of polyclonal and monoclonal antibodies against two alpha-bungarotoxin-binding alpha subunits from neuronal nicotinic receptors. J Neuroimmunol 1992; 38:115-28. [PMID: 1374423 DOI: 10.1016/0165-5728(92)90096-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Recently, cDNAs for alpha subunits of two different neuronal alpha-bungarotoxin-binding proteins (alpha BgtBP) were isolated from chick brain, designated alpha BgtBP alpha 1 and alpha BgtBP alpha 2. These are now also referred to as subunits alpha 7 and alpha 8, respectively. Expression studies in Xenopus oocytes have indicated that alpha 7 subunits are able to form cation channels that are sensitive to nicotinic ligands, and therefore represent bona fide nicotinic acetylcholine receptor subunits. Polyclonal and monoclonal antibodies (mAbs) have been produced against: (i) affinity-purified chick brain alpha BgtBP; and (ii) fusion proteins containing the unique cytoplasmic sequences alpha 7(327-412) and alpha 8(293-435). Here, synthetic overlapping peptides corresponding to their deduced amino acid sequences are used to map the epitopes recognized by the different antibodies. The polyclonal response to affinity-purified alpha BgtBPs and the fusion proteins indicates that sequence segments 290-420 of both subunits contain several major and minor epitopes. mAbs selected for their ability to bind both native and denatured alpha BgtBPs isolated from chick brain also recognize subunit-specific sequential epitopes within the sequence segment 290-420. The epitopes recognized by the mAbs correspond to the minor epitopes defined using antisera. The mAbs characterized in these studies will provide useful probes for further studies of alpha BgtBP structure and histological localization.
Collapse
Affiliation(s)
- K E McLane
- Department of Biochemistry, College of Biological Sciences, University of Minnesota St. Paul 55108
| | | | | | | |
Collapse
|
18
|
Bahouth SW, Wang HY, Malbon CC. Immunological approaches for probing receptor structure and function. Trends Pharmacol Sci 1991; 12:338-43. [PMID: 1659002 DOI: 10.1016/0165-6147(91)90593-h] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Molecular cloning has revealed the primary sequence of numerous membrane receptors, and this information catalysed two important efforts: modeling of receptor structure by hydropathy analysis and generating sequence-specific immunological probes with which these models can be tested experimentally. Craig Malbon and his colleagues outline the recent advances that illustrate how anti-peptide antibodies raised to synthetic sequences of membrane receptor have generated new information on the topology, functional domains and cellular localization of transmembrane signaling elements. They focus on two examples, the G protein-linked beta-adrenoceptor, and the nicotinic acetylcholine receptor, an intrinsic ion channel receptor. These two classes of receptor provide templates for the analysis of topographical models of membrane proteins with immunological probes, especially anti-peptide antibodies, and demonstrate how these results complement those obtained from molecular, biochemical and biophysical techniques. Although this powerful strategy is not without faults, it is likely to continue to be applied successfully to the analysis of the structure and function of receptors, ion channels and other membrane proteins.
Collapse
Affiliation(s)
- S W Bahouth
- Department of Pharmacology, College of Medicine, University of Tennessee, Memphis 38163
| | | | | |
Collapse
|
19
|
Chavez R, Hall Z. The transmembrane topology of the amino terminus of the alpha subunit of the nicotinic acetylcholine receptor. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98649-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
20
|
Anand R, Conroy W, Schoepfer R, Whiting P, Lindstrom J. Neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes have a pentameric quaternary structure. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99147-7] [Citation(s) in RCA: 221] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
21
|
Dwyer BP. Topological dispositions of lysine alpha 380 and lysine gamma 486 in the acetylcholine receptor from Torpedo californica. Biochemistry 1991; 30:4105-12. [PMID: 1902116 DOI: 10.1021/bi00230a041] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The locations have been determined, with respect to the plasma membrane, of lysine alpha 380 and lysine gamma 486 in the alpha subunit and the gamma subunit, respectively, of the nicotinic acetylcholine receptor from Torpedo californica. Immunoadsorbents were constructed that recognize the carboxy terminus of the peptide GVKYIAE released by proteolytic digestion from positions 378-384 in the amino acid sequence of the alpha subunit of the acetylcholine receptor and the carboxy terminus of the peptide KYVP released by proteolytic digestion from positions 486-489 in the amino acid sequence of the gamma subunit. They were used to isolate these peptides from proteolytic digests of polypeptides from the acetylcholine receptor. Sealed vesicles containing the native acetylcholine receptor were labeled with pyridoxal phosphate and sodium [3H]-borohydride. Saponin was added to a portion of the vesicles prior to labeling to render them permeable to pyridoxal phosphate. The effect of saponin on the incorporation of pyridoxamine phosphate into lysine alpha 380 and lysine gamma 486 from the acetylcholine receptor in these vesicles was assessed with the immunoadsorbents. The peptides bound and released by the immunoadsorbents were positively identified and quantified by high-pressure liquid chromatography. Modification of lysine alpha 380 in the native acetylcholine receptor in sealed vesicles increased 5-fold in the presence of saponin, while modification of lysine gamma 486 was unaffected by the presence of saponin. The conclusions that follow from these results are that lysine alpha 380 is on the inside surface of a vesicle and lysine gamma 486 is on the outside surface.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- B P Dwyer
- Department of Chemistry, University of California, San Diego, La Jolla 92093
| |
Collapse
|
22
|
Blount P, Merlie JP. Chapter 8 Biogenesis of the Mouse Muscle Nicotinic Acetylcholine Receptor. CURRENT TOPICS IN MEMBRANES 1991. [DOI: 10.1016/s0070-2161(08)60806-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
23
|
Tzartos SJ, Barkas T, Cung MT, Kordossi A, Loutrari H, Marraud M, Papadouli I, Sakarellos C, Sophianos D, Tsikaris V. The main immunogenic region of the acetylcholine receptor. Structure and role in myasthenia gravis. Autoimmunity 1991; 8:259-70. [PMID: 1718457 DOI: 10.3109/08916939109007633] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Auto-antibodies to the nicotine acetylcholine receptor (AChR) cause the disease myasthenia gravis (MG). Animals immunized with AChR or receiving anti-AChR antibodies acquire MG symptoms. The majority of the monoclonal antibodies (mAbs) raised in rats against intact AChR bind to a region on the extracellular side of the AChR's alpha-subunit, the main immunogenic region (MIR). The major loop of the overlapping epitopes for several anti-MIR mAbs has been localised between residues 67-76 of the alpha-subunit. Anti-MIR mAbs are very potent in accelerating AChR degradation (antigenic modulation) in muscle cell cultures and transferring experimental MG in animals. Fab fragments of single anti-MIR mAbs when bound to the AChR inhibit two-thirds of the MG patients' antibodies from binding and from inducing antigenic modulation of the AChR. This suggest that the majority of the human MG antibodies are also directed against the MIR. It has however to be verified by direct experiments.
Collapse
Affiliation(s)
- S J Tzartos
- Dept. of Biochemistry, Hellenic Pasteur Institute, Athens, Greece
| | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Lindstrom J, Schoepfer R, Conroy W, Whiting P, Das M, Saedi M, Anand R. The nicotinic acetylcholine receptor gene family: structure of nicotinic receptors from muscle and neurons and neuronal alpha-bungarotoxin-binding proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1991; 287:255-78. [PMID: 1759611 DOI: 10.1007/978-1-4684-5907-4_22] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- J Lindstrom
- Salk Institute for Biological Studies, San Diego, CA 92138
| | | | | | | | | | | | | |
Collapse
|