1
|
Farzad R, Gholami A, Hayati Roodbari N, Shahbazzadeh D. The anti-rabies activity of Caspian cobra venom. Toxicon 2020; 186:175-181. [PMID: 32818494 DOI: 10.1016/j.toxicon.2020.08.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 08/10/2020] [Accepted: 08/15/2020] [Indexed: 12/28/2022]
Abstract
Rabies is acute encephalitis that continuously kills thousands of people annually. There is no clinical cure for rabies so far and its prevention is limited to sero-vaccinations based on standard WHO protocols. Certain compounds such as snake venoms contain active biological components with tendency toward acetylcholine receptors and ion channels at the cell surface. These compounds then are able to reduce aggregation of the virus in neuromuscular junction that may lead to inhibit the virus activity. In this study we worked on cytotoxicity and antiviral activity effects of Naja naja oxiana (Iranian Caspian cobra) snake venom components, on Rabies Lyssavirus (Rabies virus; RABV) infected mammalian cells. The concentration of 25 μg/ml F5 fraction separated by FPLC showed minor toxicity on BHK-21 cells by MTT test and high antiviral activity against infected cells by FAT assay. Further studies on F5 fractionation by HPLC showed that the proliferation of infected BHK-21 cells by rabies virus CVS-11 strain was decreased up to 80% by using 20 μg/ml P5 peak, after 48 h. We assume that P5-peptide (MW < 10 kDa) enters the cells through AChR receptors same as rabies virus without competition in binding to the cell receptors and is able to reduce the virus proliferation on post viral infection phase. This is the first report of the presence of an anti-rabies effect of Caspian cobra snake venom component. As per our results the P5 peak is a suitable candidate for further studies as a new agent to reduce CVS-11 rabies virus.
Collapse
Affiliation(s)
- Reza Farzad
- Biology Department, Science and Research Branch, Islamic Azad University, Tehran, Iran.
| | - Alireza Gholami
- Virology Department, Pasteur Institute of Iran, Tehran, Iran.
| | - Nasim Hayati Roodbari
- Biology Department, Science and Research Branch, Islamic Azad University, Tehran, Iran.
| | - Delavar Shahbazzadeh
- Biotechnology Research Center, Venom and Biotherapeutics Molecules Laboratory, Pasteur Institute of Iran, Tehran, Iran.
| |
Collapse
|
2
|
Loring RH. The Molecular Basis of Curaremimetic Snake Neurotoxin Specificity for Neuronal Nicotinic Receptor Subtypes. ACTA ACUST UNITED AC 2008. [DOI: 10.3109/15569549309033109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
3
|
Nirthanan S, Gwee MCE. Three-finger alpha-neurotoxins and the nicotinic acetylcholine receptor, forty years on. J Pharmacol Sci 2004; 94:1-17. [PMID: 14745112 DOI: 10.1254/jphs.94.1] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The discovery, about forty years ago, of alpha-bungarotoxin, a three-finger alpha-neurotoxin from Bungarus multicinctus venom, enabled the isolation of the nicotinic acetylcholine receptor (nAChR), making it one of the most thoroughly characterized receptors today. Since then, the sites of interaction between alpha-neurotoxins and nAChRs have largely been delineated, revealing the remarkable plasticity of the three-finger toxin fold that has optimally evolved to utilize different combinations of functional groups to generate a panoply of target specificities to discern subtle differences between nAChR subtypes. New facets in toxinology have now broadened the scope for the use of alpha-neurotoxins in scientific discovery. For instance, the development of short, combinatorial library-derived, synthetic peptides that bind with sub-nanomolar affinity to alpha-bungarotoxin and prevent its interaction with muscle nAChRs has led to the in vivo neutralization of experimental alpha-bungarotoxin envenomation, while the successful introduction of pharmatopes bearing "alpha-bungarotoxin-sensitive sites" into toxin-insensitive nAChRs has permitted the use of various alpha-neurotoxin tags to localize and characterize new receptor subtypes. More ambitious strategies can now be envisaged for engineering rationally designed novel activities on three-finger toxin scaffolds to generate lead peptides of therapeutic value that target the nicotinic pharmacopoeia. This review details the progress made towards achieving this goal.
Collapse
|
4
|
Lozzi L, Lelli B, Runci Y, Scali S, Bernini A, Falciani C, Pini A, Niccolai N, Neri P, Bracci L. Rational design and molecular diversity for the construction of anti-alpha-bungarotoxin antidotes with high affinity and in vivo efficiency. CHEMISTRY & BIOLOGY 2003; 10:411-7. [PMID: 12770823 DOI: 10.1016/s1074-5521(03)00094-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The structure of peptide p6.7, a mimotope of the nicotinic receptor ligand site that binds alpha-bungarotoxin and neutralizes its toxicity, was compared to that of the acetylcholine binding protein. The central loop of p6.7, when complexed with alpha-bungarotoxin, fits the structure of the acetylcholine binding protein (AChBP) ligand site, whereas peptide terminal residues seem to be less involved in toxin binding. The minimal binding sequence of p6.7 was confirmed experimentally by synthesis of progressively deleted peptides. Affinity maturation was then achieved by random addition of residues flanking the minimal binding sequence and by selection of new alpha-bungarotoxin binding peptides on the basis of their dissociation kinetic rate. The tetra-branched forms of the resulting high-affinity peptides were effective as antidotes in vivo at a significantly lower dose than the tetra-branched lead peptide.
Collapse
Affiliation(s)
- Luisa Lozzi
- Department of Molecular Biology, University of Siena, via Fiorentina 1, I-53100 Siena, Italy
| | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Moise L, Zeng H, Caffery P, Rogowski RS, Hawrot E. STRUCTURE AND FUNCTION OF α-BUNGAROTOXIN. ACTA ACUST UNITED AC 2002. [DOI: 10.1081/txr-120014407] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
6
|
Bracci L, Lozzi L, Pini A, Lelli B, Falciani C, Niccolai N, Bernini A, Spreafico A, Soldani P, Neri P. A branched peptide mimotope of the nicotinic receptor binding site is a potent synthetic antidote against the snake neurotoxin alpha-bungarotoxin. Biochemistry 2002; 41:10194-9. [PMID: 12162733 DOI: 10.1021/bi0256025] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We previously produced synthetic peptides mimicking the snake neurotoxin binding site of the nicotinic receptor. These peptide mimotopes bind the snake neurotoxin alpha-bungarotoxin with higher affinity than peptides reproducing native receptor sequences and inhibit toxin binding to nicotinic receptors in vitro; yet their efficiency in vivo is low. Here we synthesized one of the peptide mimotopes in a tetrabranched MAP form. The MAP peptide binds alpha-bungarotoxin in solution and inhibits its binding to the receptor with a K(A) and an IC(50) similar to the monomeric peptide. Nonetheless, it is at least 100 times more active in vivo. The MAP completely neutralizes toxin lethality when injected in mice at a dose compatible with its use as a synthetic antidote in humans. The in vivo efficacy of the tetrameric peptide cannot be ascribed to a kinetic and thermodynamic effect and is probably related to different pharmacokinetic behavior of the tetrameric molecule, with respect to the monomer. Our findings bring new perspectives to the therapeutic use of multimeric peptides.
Collapse
Affiliation(s)
- Luisa Bracci
- Department of Molecular Biology, Laboratory of Biotechnology, University of Siena, Italy.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Moise L, Piserchio A, Basus VJ, Hawrot E. NMR structural analysis of alpha-bungarotoxin and its complex with the principal alpha-neurotoxin-binding sequence on the alpha 7 subunit of a neuronal nicotinic acetylcholine receptor. J Biol Chem 2002; 277:12406-17. [PMID: 11790782 DOI: 10.1074/jbc.m110320200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report a new, higher resolution NMR structure of alpha-bungarotoxin that defines the structure-determining disulfide core and beta-sheet regions. We further report the NMR structure of the stoichiometric complex formed between alpha-bungarotoxin and a recombinantly expressed 19-mer peptide ((178)IPGKRTESFYECCKEPYPD(196)) derived from the alpha7 subunit of the chick neuronal nicotinic acetylcholine receptor. A comparison of these two structures reveals binding-induced stabilization of the flexible tip of finger II in alpha-bungarotoxin. The conformational rearrangements in the toxin create an extensive binding surface involving both sides of the alpha7 19-mer hairpin-like structure. At the contact zone, Ala(7), Ser(9), and Ile(11) in finger I and Arg(36), Lys(38), Val(39), and Val(40) in finger II of alpha-bungarotoxin interface with Phe(186), Tyr(187), Glu(188), and Tyr(194) in the alpha7 19-mer underscoring the importance of receptor aromatic residues as critical neurotoxin-binding determinants. Superimposing the structure of the complex onto that of the acetylcholine-binding protein (1I9B), a soluble homologue of the extracellular domain of the alpha7 receptor, places alpha-bungarotoxin at the peripheral surface of the inter-subunit interface occluding the agonist-binding site. The disulfide-rich core of alpha-bungarotoxin is suggested to be tilted in the direction of the membrane surface with finger II extending into the proposed ligand-binding cavity.
Collapse
Affiliation(s)
- Leonard Moise
- Department of Molecular Pharmacology, Brown University, Providence, Rhode Island 02912, USA
| | | | | | | |
Collapse
|
8
|
Bracci L, Lozzi L, Lelli B, Pini A, Neri P. Mimotopes of the nicotinic receptor binding site selected by a combinatorial peptide library. Biochemistry 2001; 40:6611-9. [PMID: 11380255 DOI: 10.1021/bi0023201] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Peptide libraries allow selecting new molecules, defined as mimotopes, which are able to mimic the structural and functional features of a native protein. This technology can be applied for the development of new reagents, which can interfere with the action of specific ligands on their target receptors. In the present study we used a combinatorial library approach to produce synthetic peptides mimicking the snake neurotoxin binding site of nicotinic receptors. On the basis of amino acid sequence comparison of different alpha-bungarotoxin binding receptors, we designed a 14 amino acid combinatorial synthetic peptide library with five invariant, four partially variant, and five totally variant positions. Peptides were synthesized using SPOT synthesis on cellulose membranes, and binding sequences were selected using biotinylated alpha-bungarotoxin. Each variant position was systematically identified, and all possible combinations of the best reacting amino acids in each variant position were tested. The best reactive sequences were identified, produced in soluble form, and tested in BIACORE to compare their kinetic constants. We identified several different peptides that can inhibit the binding of alpha-bungarotoxin to both muscle and neuronal nicotinic receptors. Peptide mimotopes have a toxin-binding affinity that is considerably higher than peptides reproducing native receptor sequences.
Collapse
Affiliation(s)
- L Bracci
- Department of Molecular Biology, Division of Biological Chemistry, University of Siena, Via Fiorentina 1, 53100 Siena, Italy.
| | | | | | | | | |
Collapse
|
9
|
Eastham HM, Lind RJ, Eastlake JL, Clarke BS, Towner P, Reynolds SE, Wolstenholme AJ, Wonnacott S. Characterization of a nicotinic acetylcholine receptor from the insect Manduca sexta. Eur J Neurosci 1998; 10:879-89. [PMID: 9753155 DOI: 10.1046/j.1460-9568.1998.00095.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Manduca sexta is a nicotine-insensitive insect, the larval form of which feeds on tobacco. It has been postulated that its nicotine insensitivity may reflect the presence of a modified nicotinic acetylcholine receptor whose alpha subunits lack the amino acid residues necessary for binding nicotine: we have performed ligand binding assays and molecular cloning to examine this hypothesis. [125I]alpha-bungarotoxin bound specifically to both larval and adult membranes, with Kd values of 7.6 and 6.5 nM and Bmax values of 119 and 815 fmol/mg protein, respectively. The pharmacological profile of [1251]alpha-bungarotoxin binding was similar in both tissues. In particular, nicotine (Ki values: 1.6 microM and 2 microM for larvae and adults, respectively) competed with an affinity similar to that found for nicotine-sensitive insects. No alpha-bungarotoxin-insensitive binding sites labelled by [3H]epibatidine could be detected. Using the alpha-like subunit from the locust Schistocerca gregaria to probe two cDNA libraries, and by inverse PCR on circularized genomic DNA from Manduca sexta, we have obtained overlapping cDNA clones that contain the complete coding sequence of a putative nicotinic subunit from Manduca sexta (MARA1). No other alpha-subunit cDNAs were isolated using this probe, although it hybridized to multiple bands on Southern blots. The sequence of MARA1 is consistent with an alpha-like subunit capable of binding alpha-bungarotoxin, and it retains all those amino acids implicated in nicotine binding to vertebrate nicotinic receptors. Taken together, these findings provide no support for the hypothesis that the nicotine insensitivity of Manduca sexta is the result of a nicotinic receptor with diminished nicotine binding.
Collapse
Affiliation(s)
- H M Eastham
- School of Biology and Biochemistry, University of Bath, UK
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Affiliation(s)
- J Lindstrom
- Department of Neuroscience, Medical School, University of Pennsylvania, Philadelphia 19104-6074, USA
| | | | | | | | | | | |
Collapse
|
11
|
Tornøe C, Bai D, Holden-Dye L, Abramson SN, Sattelle DB. Actions of neurotoxins (bungarotoxins, neosurugatoxin and lophotoxins) on insect and nematode nicotinic acetylcholine receptors. Toxicon 1995; 33:411-24. [PMID: 7570627 DOI: 10.1016/0041-0101(94)00163-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Neurotoxins of natural origin have proved to be of considerable value in the isolation and characterization of vertebrate muscle and neuronal nicotinic acetylcholine receptors (nAChRs). To date, they have been used less extensively in studies of invertebrate nAChRs. Here we examine how a variety of neurotoxins (the snake toxins alpha-bungarotoxin, alpha-BGT, and kappa-bungarotoxin, kappa-BGT, the molluscan toxin, neosurugatoxin, and the soft coral toxins, lophotoxin and bipinnatin-B) can be used to characterize nAChRs in an insect, Periplaneta americana, and in a parasitic nematode, Ascaris suum. The agonist profiles of these nAChRs are distinct, but the most striking differences are in the actions of antagonists. Whereas the insect nAChR is blocked by both alpha- and kappa-bungarotoxins, the nematode receptor is only blocked by kappa-BGT. Neosurugatoxin blocks nAChRs in both species, but the lophotoxins which block all nAChRs investigated to date are much less effective on the Ascaris muscle receptor.
Collapse
Affiliation(s)
- C Tornøe
- Babraham Institute Laboratory of Molecular Signalling, Department of Zoology, University of Cambridge, U.K
| | | | | | | | | |
Collapse
|
12
|
Gotti C, Moretti M, Longhi R, Briscini L, Balestra B, Clementi F. Expression of alpha-bungarotoxin receptor subtypes in chick central nervous system during development. JOURNAL OF RECEPTOR RESEARCH 1994; 14:335-46. [PMID: 7877133 DOI: 10.3109/10799899409101508] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Chick central nervous system (CNS) expresses alpha-bungarotoxin (alpha Bgtx) receptors. We have recently reported the purification and characterization of two alpha Bgtx receptor subtypes, alpha 7 and alpha 7-alpha 8 from chick optic lobe (COL). In order to study whether other alpha Bgtx receptor subtypes are present in other areas of the chick CNS, as well as their developmental expression, we used anti-alpha 7 and anti-alpha 8 subunit-specific antibodies to study alpha Bgtx receptors at different developmental stages in COL, brain and retina. We found that only the alpha 7 and alpha 7-alpha 8 subtypes are present at all developmental stages in chick COL and brain, where they represent 90% of all the alpha Bgtx receptors at embryonic day 19 and 1 day post hatching (D1). In chick retina, an alpha 8 subtype representing 50% of all alpha Bgtx receptors at D1 is present in addition to the alpha 7 and alpha 7-alpha 8 subtypes, and the expression of this alpha 8 subtype increases during neurodevelopment.
Collapse
Affiliation(s)
- C Gotti
- Department of Medical Pharmacology, University of Milano, Italy
| | | | | | | | | | | |
Collapse
|
13
|
Gotti C, Hanke W, Maury K, Moretti M, Ballivet M, Clementi F, Bertrand D. Pharmacology and biophysical properties of alpha 7 and alpha 7-alpha 8 alpha-bungarotoxin receptor subtypes immunopurified from the chick optic lobe. Eur J Neurosci 1994; 6:1281-91. [PMID: 7981870 DOI: 10.1111/j.1460-9568.1994.tb00318.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Two chick optic lobe alpha-bungarotoxin receptor subtypes (alpha 7 and alpha 7-alpha 8) were immunopurified using polyclonal antibodies raised against synthetic peptides of chick alpha 7 and alpha 8 alpha-bungarotoxin receptor subunits. The alpha 7 subtype contained the M(r) 57,000 alpha 7 subunit, and represented 60-70% of the alpha-bungarotoxin receptors; the alpha 7-alpha 8 subtype contained the M(r) 57,000 alpha 7 and alpha 8 subunits, and represented only 20-25% of the receptors. Both subtypes also had an additional M(r) 52,000 subunit. The affinity of these subtypes for alpha-bungarotoxin as well as antagonists was similar. However, the alpha 7-alpha 8 subtype displayed consistently higher affinities for agonists. When reconstituted in planar lipid bilayers, the alpha 7-alpha 8 subtype displayed several conductance states of 10-50 pS; the alpha 7 subtype had only one conductance state of 45 pS. The alpha 7-alpha 8 subtype was activated by lower agonist concentrations than the alpha 7 subtype. When expressed in Xenopus oocytes, the alpha 8 subunit formed functional homomeric receptors that desensitized rapidly. These channels were blocked by alpha-bungarotoxin and displayed a higher affinity for agonists than the alpha 7 homomeric receptor. Taken together, these data indicate that at least two alpha-bungarotoxin subtypes are present in the chick optic lobe. They operate as ligand-gated channels and display different agonist sensitivities and kinetics/conductance properties.
Collapse
Affiliation(s)
- C Gotti
- Department of Medical Pharmacology, University of Milan, Italy
| | | | | | | | | | | | | |
Collapse
|
14
|
Conti-Tronconi BM, McLane KE, Raftery MA, Grando SA, Protti MP. The nicotinic acetylcholine receptor: structure and autoimmune pathology. Crit Rev Biochem Mol Biol 1994; 29:69-123. [PMID: 8026215 DOI: 10.3109/10409239409086798] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The nicotinic acetylcholine receptors (AChR) are presently the best-characterized neurotransmitter receptors. They are pentamers of homologous or identical subunits, symmetrically arranged to form a transmembrane cation channel. The AChR subunits form a family of homologous proteins, derived from a common ancestor. An autoimmune response to muscle AChR causes the disease myasthenia gravis. This review summarizes recent developments in the understanding of the AChR structure and its molecular recognition by the immune system in myasthenia.
Collapse
Affiliation(s)
- B M Conti-Tronconi
- Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul 55108
| | | | | | | | | |
Collapse
|
15
|
Gotti C, Moretti M, Longhi R, Briscini L, Manera E, Clementi F. Anti-peptide specific antibodies for the characterization of different alpha subunits of alpha-bungarotoxin binding acetylcholine receptors present in chick optic lobe. JOURNAL OF RECEPTOR RESEARCH 1993; 13:453-65. [PMID: 8450500 DOI: 10.3109/10799899309073672] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Chick optic lobe express alpha-Bungarotoxin receptors. We have recently purified these receptors which, when reconstituted in a lipid bilayer, behave as functional acetylcholine gated channels. In order to characterize this purified preparation, we raised polyclonal antibodies against peptides obtained from the putative cytoplasmic domain between the hydrophobic sequence M3 and M4 of two previously cloned alpha-Bungarotoxin receptor subunits, alpha 7 and alpha 8. Both antibodies recognized the receptors present in the membrane extract and in the purified preparation, although the amount of the alpha-Bungarotoxin receptors precipitated by the two antibodies was quantitatively different. In Western blots of both purified and membrane-bound receptors, these antibodies specifically reacted with an M(r) 57000-55000 band. A study was also undertaken to quantify the receptors containing these subunits in different chick brain areas; it was found that the number of these subunits, as well as their ratio, was similar in all the tested areas. Furthermore, the alpha-Bungarotoxin receptors were present in at least two subtypes, one containing only the alpha 7 subunit and the other both alpha 7 and alpha 8 subunits.
Collapse
Affiliation(s)
- C Gotti
- Department of Medical Pharmacology, University of Milan, Italy
| | | | | | | | | | | |
Collapse
|
16
|
Quik M. Thymopoietin, a thymic polypeptide, potently interacts at muscle and neuronal nicotinic alpha-bungarotoxin receptors. Mol Neurobiol 1992; 6:19-40. [PMID: 1463587 DOI: 10.1007/bf02935565] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Current studies suggest that several distinct populations of nicotinic acetylcholine (ACh) receptors exist. One of these is the muscle-type nicotinic receptors with which neuromuscular nicotinic receptor ligands and the snake toxin alpha-bungarotoxin interact. alpha-Bungarotoxin potently binds to these nicotinic receptors and blocks their function, two characteristics that have made the alpha-toxin a very useful probe for the characterization of these sites. In neuronal tissues, several populations of nicotinic receptors have been identified which, although they share a nicotinic pharmacology, have unique characteristics. The alpha-bungarotoxin-insensitive neuronal nicotinic receptors, which may be involved in mediating neuronal excitability, bind nicotinic agonists with high affinity but do not interact with alpha-bungarotoxin. Subtypes of these alpha-toxin-insensitive receptors appear to exist, as evidenced by findings that some are inhibited by neuronal bungarotoxin whereas others are not. In addition to the alpha-bungarotoxin-insensitive sites, alpha-bungarotoxin-sensitive neuronal nicotinic receptors are also present in neuronal tissues. These latter receptors bind alpha-bungarotoxin with high affinity and nicotinic agonists with an affinity in the microM range. The function of the nicotinic alpha-bungarotoxin receptors are as yet uncertain. Thymopoietin, a polypeptide linked to immune function, appears to interact specifically with nicotinic receptor populations that bind alpha-bungarotoxin. Thus, in muscle tissue where alpha-bungarotoxin both binds to the receptor and blocks activity, thymopoietin also potently binds to the receptor and inhibits nicotinic receptors-mediated function. In neuronal tissues, thymopoietin interacts only with the nicotinic alpha-bungarotoxin site and not the alpha-bungarotoxin-insensitive neuronal nicotinic receptor population. These observations that thymopoietin potently and specifically interacts with nicotinic alpha-bungarotoxin-sensitive receptors in neuronal and muscle tissue, together with findings that thymopoietin is an endogenously occurring agent, could suggest that this immune-related polypeptide represents a ligand for the alpha-bungarotoxin receptors. The function of thymopoietin at the alpha-bungarotoxin receptor is as yet uncertain; however, a potential trophic, as well as other roles are suggested.
Collapse
Affiliation(s)
- M Quik
- Department of Pharmacology, McGill University, Montreal, Quebec, Canada
| |
Collapse
|
17
|
McLane KE, Fritzen M, Wu X, Diethelm B, Maelicke A, Conti-Tronconi BM. Species- and subtype-specific recognition by antibody WF6 of a sequence segment forming an alpha-bungarotoxin binding site on the nicotinic acetylcholine receptor alpha subunit. JOURNAL OF RECEPTOR RESEARCH 1992; 12:299-321. [PMID: 1507184 DOI: 10.3109/10799899209074798] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The monoclonal antibody WF6 competes with acetylcholine and alpha-bungarotoxin (alpha-BGT) for binding to the Torpedo nicotinic acetylcholine receptor (nAChR) alpha 1 subunit. Using synthetic peptides corresponding to the complete Torpedo nAChR alpha 1 subunit, we previously mapped a continuous epitope recognized by WF6, and the prototope for alpha-BGT, to the sequence segment alpha 1(181-200). Single amino acid substitution analogs have been used as an initial approach to determine the critical amino acids for WF6 and alpha-BGT binding. In the present study, we continue our analysis of the structural features of the WF6 epitope by comparing its cross-reactivity with synthetic peptides corresponding to the alpha 1 subunits from the muscle nAChRs of different species, the rat brain alpha 2, alpha 3, alpha 4 and alpha 5 nAChR subtypes, and the chick brain alpha-BGT binding protein subunits, alpha BGTBP alpha 1 and alpha BGTBP alpha 2. Our results indicate that WF6 is able to cross-react with the muscle alpha 1 subunits of different species by virtue of conservation of several critical amino acid residues between positions 190-198 of the alpha 1 subunit. These studies further define the essential structural features of the sequence segment alpha 1(181-200) required to form the epitope for WF6.
Collapse
Affiliation(s)
- K E McLane
- Department of Biochemistry, College of Biological Sciences, University of Minnesota St. Paul 55108
| | | | | | | | | | | |
Collapse
|