1
|
Xu J, Lei X, Li A, Li J, Li S, Chen L. Scalable production of recombinant three-finger proteins: from inclusion bodies to high quality molecular probes. Microb Cell Fact 2024; 23:48. [PMID: 38347541 PMCID: PMC10860255 DOI: 10.1186/s12934-024-02316-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 08/10/2022] [Indexed: 02/15/2024] Open
Abstract
BACKGROUND The three-finger proteins are a collection of disulfide bond rich proteins of great biomedical interests. Scalable recombinant expression and purification of bioactive three-finger proteins is quite difficult. RESULTS We introduce a working pipeline for expression, purification and validation of disulfide-bond rich three-finger proteins using E. coli as the expression host. With this pipeline, we have successfully obtained highly purified and bioactive recombinant α-Βungarotoxin, k-Bungarotoxin, Hannalgesin, Mambalgin-1, α-Cobratoxin, MTα, Slurp1, Pate B etc. Milligrams to hundreds of milligrams of recombinant three finger proteins were obtained within weeks in the lab. The recombinant proteins showed specificity in binding assay and six of them were crystallized and structurally validated using X-ray diffraction protein crystallography. CONCLUSIONS Our pipeline allows refolding and purifying recombinant three finger proteins under optimized conditions and can be scaled up for massive production of three finger proteins. As many three finger proteins have attractive therapeutic or research interests and due to the extremely high quality of the recombinant three finger proteins we obtained, our method provides a competitive alternative to either their native counterparts or chemically synthetic ones and should facilitate related research and applications.
Collapse
Affiliation(s)
- Jiang Xu
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
| | - Xiao Lei
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Ao Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Jun Li
- Institute of Clinical Medicine, The First Affiliated Hospital of University of South China, Hengyang, Hunan, 421001, People's Republic of China
| | - Shuxing Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Lin Chen
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
| |
Collapse
|
2
|
Abstract
The α7-type nicotinic acetylcholine receptor is one of the most unique and interesting of all the members of the cys-loop superfamily of ligand-gated ion channels. Since it was first identified initially as a binding site for α-bungarotoxin in mammalian brain and later as a functional homomeric receptor with relatively high calcium permeability, it has been pursued as a potential therapeutic target for numerous indications, from Alzheimer disease to asthma. In this review, we discuss the history and state of the art for targeting α7 receptors, beginning with subtype-selective agonists and the basic pharmacophore for the selective activation of α7 receptors. A key feature of α7 receptors is their rapid desensitization by standard "orthosteric" agonist, and we discuss insights into the conformational landscape of α7 receptors that has been gained by the development of ligands binding to allosteric sites. Some of these sites are targeted by positive allosteric modulators that have a wide range of effects on the activation profile of the receptors. Other sites are targeted by direct allosteric agonist or antagonists. We include a perspective on the potential importance of α7 receptors for metabotropic as well as ionotropic signaling. We outline the challenges that exist for future development of drugs to target this important receptor and approaches that may be considered to address those challenges. SIGNIFICANCE STATEMENT: The α7-type nicotinic acetylcholine receptor (nAChR) is acknowledged as a potentially important therapeutic target with functional properties associated with both ionotropic and metabotropic signaling. The functional properties of α7 nAChR can be regulated in diverse ways with the variety of orthosteric and allosteric ligands described in this review.
Collapse
Affiliation(s)
- Roger L Papke
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
| |
Collapse
|
3
|
Differential Expression of Nicotine Acetylcholine Receptors Associates with Human Breast Cancer and Mediates Antitumor Activity of αO-Conotoxin GeXIVA. Mar Drugs 2020; 18:md18010061. [PMID: 31963558 PMCID: PMC7024346 DOI: 10.3390/md18010061] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 01/13/2020] [Accepted: 01/14/2020] [Indexed: 12/14/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are membrane receptors and play a major role in tumorigenesis and cancer progression. Here, we have investigated the differential expression of nAChR subunits in human breast cancer cell lines and breast epithelial cell lines at mRNA and protein levels and the effects of the αO-conotoxin GeXIVA, antagonist of α9α10 nAChR, on human breast cancer cells. Reverse transcription polymerase chain reaction (PCR) demonstrated that all nAChR subunits, except α6, were expressed in the 20 tested cell lines. Real time quantitative PCR (QRT-PCR) suggested that the mRNA of α5, α7, α9 and β4 nAChR subunits were overexpressed in all the breast cancer cell lines compared with the normal epithelial cell line HS578BST. α9 nAChR was highly expressed in almost all the breast cancer cell lines in comparison to normal cells. The different expression is prominent (p < 0.001) as determined by flow cytometry and Western blotting, except for MDA-MB-453 and HCC1395 cell lines. αO-conotoxin GeXIVA that targeted α9α10 nAChR were able to significantly inhibit breast cancer cell proliferation in vitro and merits further investigation as potential agents for targeted therapy.
Collapse
|
4
|
Differential effects of α4β2 nicotinic receptor antagonists and partial-agonists on contextual fear extinction in male C57BL/6 mice. Psychopharmacology (Berl) 2018; 235:1211-1219. [PMID: 29383396 PMCID: PMC5871575 DOI: 10.1007/s00213-018-4837-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 01/19/2018] [Indexed: 02/06/2023]
Abstract
RATIONALE Numerous studies have attributed the psychopathology of post-traumatic stress disorder (PTSD) to maladaptive behavioral responses such as an inability to extinguish fear. While exposure therapies are mostly effective in treating these disorders by enhancing extinction learning, relapse of PTSD symptoms is common. Although several studies indicated a role for cholinergic transmission and nicotinic acetylcholine receptors (nAChRs) in anxiety and stress disorder symptomatology, very little is known about the specific contribution of nAChRs to fear extinction OBJECTIVES: In the present study, we examined the effects of inhibition and desensitization of α4β2 nAChRs via a full antagonist (Dihydro-beta-erythroidine (DhβE)) and two α4β2 nAChR partial-agonists (varenicline and sazetidine-A) on contextual fear extinction, locomotor activity, and spontaneous recovery of contextual fear in mice. METHODS We trained and tested the subjects in a contextual fear extinction as well as an open field paradigm and spontaneous recovery following injections of DhβE, varenicline, and sazetidine-A. RESULTS Our results demonstrated that lower doses of DhβE (1 mg/kg) and sazetidine-A (0.01 mg/kg) enhanced contextual fear extinction whereas higher doses of varenicline (0.1 mg/kg) and sazetidine-A (0.1 mg/kg) resulted in impaired contextual fear extinction. However, the higher dose of sazetidine-A (0.1 mg/kg) decreased locomotor activity, which may contribute to increased freezing response observed during fear extinction. Finally, we found that the low dose of DhβE, but not sazetidine-A, also decreased spontaneous recovery of contextual fear following fear extinction. CONCLUSIONS Overall, these results suggest that inhibition and desensitization of α4β2 nAChRs enhance extinction of contextual fear memories. This suggests that modulation of α4β2 nAChRs may be employed as an alternative pharmacological strategy to aid exposure therapies associated with PTSD by augmenting contextual fear extinction processes.
Collapse
|
5
|
Ponce D, López-Vera E, Aguilar MB, Sánchez-Rodríguez J. Preliminary results of the in vivo and in vitro characterization of a tentacle venom fraction from the jellyfish Aurelia aurita. Toxins (Basel) 2013; 5:2420-33. [PMID: 24322597 PMCID: PMC3873694 DOI: 10.3390/toxins5122420] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 11/01/2013] [Accepted: 11/04/2013] [Indexed: 11/16/2022] Open
Abstract
The neurotoxic effects produced by a tentacle venom extract and a fraction were analyzed and correlated by in vivo and in vitro approaches. The tentacle venom extract exhibited a wide range of protein components (from 24 to >225 kDa) and produced tetanic reactions, flaccid paralysis, and death when injected into crabs. Two chromatography fractions also produced uncontrolled appendix movements and leg stretching. Further electrophysiological characterization demonstrated that one of these fractions potently inhibited ACh-elicited currents mediated by both vertebrate fetal and adult muscle nicotinic acetylcholine receptors (nAChR) subtypes. Receptor inhibition was concentration-dependent and completely reversible. The calculated IC(50) values were 1.77 μg/μL for fetal and 2.28 μg/μL for adult muscle nAChRs. The bioactive fraction was composed of a major protein component at ~90 kDa and lacked phospholipase A activity. This work represents the first insight into the interaction of jellyfish venom components and muscle nicotinic receptors.
Collapse
Affiliation(s)
- Dalia Ponce
- Instituto de Ciencias del Mar y Limnología, Unidad Académica Puerto Morelos, Universidad Nacional Autónoma de México,77500 Cancún, Quintana Roo, Mexico; E-Mail:
- Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 Coyoacán, Distrito Federal, Mexico
| | - Estuardo López-Vera
- Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 Coyoacán, Distrito Federal, Mexico
| | - Manuel B. Aguilar
- Laboratorio de Neurofarmacología Marina, Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Juriquilla 76230, Querétaro, Mexico; E-Mail:
| | - Judith Sánchez-Rodríguez
- Instituto de Ciencias del Mar y Limnología, Unidad Académica Puerto Morelos, Universidad Nacional Autónoma de México,77500 Cancún, Quintana Roo, Mexico; E-Mail:
| |
Collapse
|
6
|
Miwa JM, Walz A. Enhancement in motor learning through genetic manipulation of the Lynx1 gene. PLoS One 2012; 7:e43302. [PMID: 23139735 PMCID: PMC3489911 DOI: 10.1371/journal.pone.0043302] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 07/18/2012] [Indexed: 11/18/2022] Open
Abstract
The cholinergic system is a neuromodulatory neurotransmitter system involved in a variety of brain processes, including learning and memory, attention, and motor processes, among others. The influence of nicotinic acetylcholine receptors of the cholinergic system are moderated by lynx proteins, which are GPI-anchored membrane proteins forming tight associations with nicotinic receptors. Previous studies indicate lynx1 inhibits nicotinic receptor function and limits neuronal plasticity. We sought to investigate the mechanism of action of lynx1 on nicotinic receptor function, through the generation of lynx mouse models, expressing a soluble version of lynx and comparing results to the full length overexpression. Using rotarod as a test for motor learning, we found that expressing a secreted variant of lynx leads to motor learning enhancements whereas overexpression of full-length lynx had no effect. Further, adult lynx1KO mice demonstrated comparable motor learning enhancements as the soluble transgenic lines, whereas previously, aged lynx1KO mice showed performance augmentation only with nicotine treatment. From this we conclude the motor learning is more sensitive to loss of lynx function, and that the GPI anchor plays a role in the normal function of the lynx protein. In addition, our data suggests that the lynx gene plays a modulatory role in the brain during aging, and that a soluble version of lynx has potential as a tool for adjusting cholinergic-dependent plasticity and learning mechanisms in the brain.
Collapse
Affiliation(s)
- Julie M Miwa
- California Institute of Technology, Pasadena, California, USA.
| | | |
Collapse
|
7
|
ORAL COMMUNICATIONS. Br J Pharmacol 2012. [DOI: 10.1111/j.1476-5381.1991.tb14725.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
|
8
|
|
9
|
Osipov AV, Rucktooa P, Kasheverov IE, Filkin SY, Starkov VG, Andreeva TV, Sixma TK, Bertrand D, Utkin YN, Tsetlin VI. Dimeric α-cobratoxin X-ray structure: localization of intermolecular disulfides and possible mode of binding to nicotinic acetylcholine receptors. J Biol Chem 2012; 287:6725-34. [PMID: 22223648 DOI: 10.1074/jbc.m111.322313] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In Naja kaouthia cobra venom, we have earlier discovered a covalent dimeric form of α-cobratoxin (αCT-αCT) with two intermolecular disulfides, but we could not determine their positions. Here, we report the αCT-αCT crystal structure at 1.94 Å where intermolecular disulfides are identified between Cys(3) in one protomer and Cys(20) of the second, and vice versa. All remaining intramolecular disulfides, including the additional bridge between Cys(26) and Cys(30) in the central loops II, have the same positions as in monomeric α-cobratoxin. The three-finger fold is essentially preserved in each protomer, but the arrangement of the αCT-αCT dimer differs from those of noncovalent crystallographic dimers of three-finger toxins (TFT) or from the κ-bungarotoxin solution structure. Selective reduction of Cys(26)-Cys(30) in one protomer does not affect the activity against the α7 nicotinic acetylcholine receptor (nAChR), whereas its reduction in both protomers almost prevents α7 nAChR recognition. On the contrary, reduction of one or both Cys(26)-Cys(30) disulfides in αCT-αCT considerably potentiates inhibition of the α3β2 nAChR by the toxin. The heteromeric dimer of α-cobratoxin and cytotoxin has an activity similar to that of αCT-αCT against the α7 nAChR and is more active against α3β2 nAChRs. Our results demonstrate that at least one Cys(26)-Cys(30) disulfide in covalent TFT dimers, similar to the monomeric TFTs, is essential for their recognition by α7 nAChR, although it is less important for interaction of covalent TFT dimers with the α3β2 nAChR.
Collapse
Affiliation(s)
- Alexey V Osipov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul Miklukho-Maklaya 16/10, Moscow 117997, Russia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Ho YS, Lee CH, Wu CH. The Alpha 9-Nicotinic Acetylcholine Receptor Serves as a Molecular Target for Breast Cancer Therapy. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.jecm.2011.10.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
|
11
|
From smoking to cancers: novel targets to neuronal nicotinic acetylcholine receptors. JOURNAL OF ONCOLOGY 2011; 2011:693424. [PMID: 21772846 PMCID: PMC3136181 DOI: 10.1155/2011/693424] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 02/18/2011] [Accepted: 03/17/2011] [Indexed: 12/11/2022]
Abstract
Cigarette smoking bears a strong etiological association with many neovascularization-related diseases, including cancer, cardiovascular disease, and age-related macular degeneration. Cigarette smoke is a complex mixture of many compounds, including nicotine, which is the major active and addictive component of tobacco. Nicotine and its specific metabolized carcinogens directly bind to nicotinic acetylcholine receptors (nAChRs) on cell membranes and trigger the nAChR signal cascade. The nAChRs were originally thought to be ligand-gated ion channels that modulate physiological processes ranging from neurotransmission to cancer signaling. For several decades, the nAChRs served as a prototypic molecule for neurotransmitter receptors; however, they are now important therapeutic targets for various diseases, including Alzheimer's and Parkinson's diseases, schizophrenia, and even cancer. This paper describes recent advances in our understanding of the assembly, activity, and biological functions of nicotinic receptors, as well as developments in the therapeutic application of nicotinic receptor ligands.
Collapse
|
12
|
Wu CH, Lee CH, Ho YS. Nicotinic acetylcholine receptor-based blockade: applications of molecular targets for cancer therapy. Clin Cancer Res 2011; 17:3533-41. [PMID: 21444681 DOI: 10.1158/1078-0432.ccr-10-2434] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The nicotinic acetylcholine receptor (nAChR) was first characterized in 1970 as a membrane receptor of a neurotransmitter and an ion channel. nAChRs have been shown to be involved in smoking-induced cancer formation in multiple types of human cancer cells. In vitro and in vivo animal studies have shown that homopentameric nAChR inhibitors, such as methyllycaconitine and α-Bgtx, can attenuate nicotine-induced proliferative, angiogenic, and metastatic effects in lung, colon, and bladder cancer cells. Recent publications have shown that α9-nAChR is important for breast cancer formation, and in many in vivo studies, α9-nAChR-specific antagonists (e.g., α-ImI, α-ImI, Vc1.1, RgIA, and It14a) produced an analgesic effect. Vc1.1 functions in a variety of animal pain models and currently has entered phase II clinical trials. For cancer therapy, natural compounds such as garcinol and EGCG have been found to block nicotine- and estrogen-induced breast cancer cell proliferation through inhibition of the α9-nAChR signaling pathway. A detailed investigation of the carcinogenic effects of nAChRs and their specific antagonists would enhance our understanding of their value as targets for clinical translation.
Collapse
Affiliation(s)
- Chih-Hsiung Wu
- Department of Surgery, School of Medicine, and Graduate Institute of Medical Sciences, College of Medicine, Taipei, Taiwan
| | | | | |
Collapse
|
13
|
Nasiripourdori A, Taly V, Grutter T, Taly A. From toxins targeting ligand gated ion channels to therapeutic molecules. Toxins (Basel) 2011; 3:260-93. [PMID: 22069709 PMCID: PMC3202823 DOI: 10.3390/toxins3030260] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/01/2011] [Accepted: 03/16/2011] [Indexed: 11/21/2022] Open
Abstract
Ligand-gated ion channels (LGIC) play a central role in inter-cellular communication. This key function has two consequences: (i) these receptor channels are major targets for drug discovery because of their potential involvement in numerous human brain diseases; (ii) they are often found to be the target of plant and animal toxins. Together this makes toxin/receptor interactions important to drug discovery projects. Therefore, toxins acting on LGIC are presented and their current/potential therapeutic uses highlighted.
Collapse
Affiliation(s)
| | - Valérie Taly
- Laboratory of Chemical Biology, Institut de Science et d'Ingénierie Supramoléculaires; ISIS/Université de Strasbourg, CNRS-UMR 7006, 8, allée Gaspard Monge, BP 70028, F-67083, Strasbourg Cedex, France;
| | - Thomas Grutter
- Laboratoire de Biophysicochimie des Récepteurs Canaux, UMR 7199 “Conception et Application de Molécules Bioactives” CNRS-Université de Strasbourg, 74 Route du Rhin-BP 60024, 67401 Illkirch Cedex, France;
| | - Antoine Taly
- Laboratoire de Biophysicochimie des Récepteurs Canaux, UMR 7199 “Conception et Application de Molécules Bioactives” CNRS-Université de Strasbourg, 74 Route du Rhin-BP 60024, 67401 Illkirch Cedex, France;
| |
Collapse
|
14
|
Ferchmin PA, Pagán OR, Ulrich H, Szeto AC, Hann RM, Eterović VA. Actions of octocoral and tobacco cembranoids on nicotinic receptors. Toxicon 2009; 54:1174-82. [PMID: 19281835 PMCID: PMC2783377 DOI: 10.1016/j.toxicon.2009.02.033] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Nicotinic acetylcholine receptors (AChRs) are pentameric proteins that form agonist-gated cation channels through the plasma membrane. AChR agonists and antagonists are potential candidates for the treatment of neurodegenerative diseases. Cembranoids are naturally occurring diterpenoids that contain a 14-carbon ring. These diterpenoids interact with AChRs in complex ways: as irreversible inhibitors at the agonist sites, as noncompetitive inhibitors, or as positive modulators, but no cembranoid was ever shown to have agonistic activity on AChRs. The cembranoid eupalmerin acetate displays positive modulation of agonist-induced currents in the muscle-type AChR and in the related gamma-aminobutyric acid (GABA) type A receptor. Moreover, cembranoids display important biological effects, many of them mediated by nicotinic receptors. Cembranoids from tobacco are neuroprotective through a nicotinic anti-apoptotic mechanism preventing excitotoxic neuronal death which in part could result from anti-inflammatory properties of cembranoids. Moreover, tobacco cembranoids also have anti-inflammatory properties which could enhance their neuroprotective properties. Cembranoids from tobacco affect nicotine-related behavior: they increase the transient initial ataxia caused by first nicotine injection into naive rats and inhibit the expression of locomotor sensitization to repeated injections of nicotine. In addition, cembranoids are known to act as anti-tumor compounds. In conclusion, cembranoids provide a promising source of lead drugs for many clinical areas, including neuroprotection, smoking-cessation, and anti-cancer therapies.
Collapse
Affiliation(s)
- P A Ferchmin
- Department of Biochemistry, Universidad Central del Caribe, Bayamon, PR, USA
| | | | | | | | | | | |
Collapse
|
15
|
|
16
|
Alpha-conotoxins as pharmacological probes of nicotinic acetylcholine receptors. Acta Pharmacol Sin 2009; 30:771-83. [PMID: 19448650 DOI: 10.1038/aps.2009.47] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cysteine-rich peptides from the venom of cone snails (Conus) target a wide variety of different ion channels. One family of conopeptides, the alpha-conotoxins, specifically target different isoforms of nicotinic acetylcholine receptors (nAChRs) found both in the neuromuscular junction and central nervous system. This family is further divided into subfamilies based on the number of amino acids between cysteine residues. The exquisite subtype selectivity of certain alpha-conotoxins has been key to the characterization of native nAChR isoforms involved in modulation of neurotransmitter release, the pathophysiology of Parkinson's disease and nociception. Structure/function characterization of alpha-conotoxins has led to the development of analogs with improved potency and/or subtype selectivity. Cyclization of the backbone structure and addition of lipophilic moieties has led to improved stability and bioavailability of alpha-conotoxins, thus paving the way for orally available therapeutics. The recent advances in phylogeny, exogenomics and molecular modeling promises the discovery of an even greater number of alpha-conotoxins and analogs with improved selectivity for specific subtypes of nAChRs.
Collapse
|
17
|
Kharrat R, Servent D, Girard E, Ouanounou G, Amar M, Marrouchi R, Benoit E, Molgó J. The marine phycotoxin gymnodimine targets muscular and neuronal nicotinic acetylcholine receptor subtypes with high affinity. J Neurochem 2008; 107:952-63. [PMID: 18990115 DOI: 10.1111/j.1471-4159.2008.05677.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
MESH Headings
- Acetylcholine/pharmacology
- Animals
- Behavior, Animal/drug effects
- Bivalvia/chemistry
- Bungarotoxins/metabolism
- Cells, Cultured
- Chromatography, High Pressure Liquid/methods
- Dose-Response Relationship, Drug
- Drug Interactions
- Electric Stimulation/methods
- Gene Expression/drug effects
- Heterocyclic Compounds, 3-Ring/analysis
- Heterocyclic Compounds, 3-Ring/chemistry
- Heterocyclic Compounds, 3-Ring/classification
- Heterocyclic Compounds, 3-Ring/pharmacology
- Humans
- Hydrocarbons, Cyclic/analysis
- Hydrocarbons, Cyclic/chemistry
- Hydrocarbons, Cyclic/classification
- Hydrocarbons, Cyclic/pharmacology
- Imines/analysis
- Imines/chemistry
- Imines/classification
- Imines/pharmacology
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Membrane Potentials/radiation effects
- Mice
- Mice, Inbred C57BL
- Muscle Cells/drug effects
- Muscle Cells/metabolism
- Neuromuscular Junction/drug effects
- Neuromuscular Junction/physiology
- Neuromuscular Junction/radiation effects
- Oocytes
- Patch-Clamp Techniques
- Protein Binding/drug effects
- Receptors, Nicotinic/metabolism
- Synaptic Transmission/drug effects
- Xenopus laevis
- alpha7 Nicotinic Acetylcholine Receptor
Collapse
Affiliation(s)
- Riadh Kharrat
- Laboratoire de Neurobiologie Cellulaire et Moléculaire-UPR9040, CNRS, Institut de Neurobiologie Alfred Fessard-FRC2118, Gif sur Yvette, France
| | | | | | | | | | | | | | | |
Collapse
|
18
|
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]
|
19
|
Hogg RC, Bertrand D. Neurotoxins acting at nicotinic receptors. FUTURE NEUROLOGY 2008. [DOI: 10.2217/14796708.3.4.463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Neurotoxins include, in the most general sense, all molecules that destroy or inhibit the proper functioning of the nervous system. Neurotoxins from animals and plants include alkaloids and peptides, many of which interact with physiological processes in a selective manner. The majority of neurotoxins disrupt the transmission of signals in the nervous system by interfering with synaptic transmission. Neurotoxins can act presynaptically to inhibit the release, uptake and recycling of neurotransmitters or postsynaptically, binding to receptors on the postsynaptic membrane and preventing their activation by neurotransmitters. A class of neurotoxins from plants and animals interact with nicotinic acetylcholine receptors, either at the neuromuscular junction, peripherally at neuronal ganglia or centrally, to produce neurotoxic effects. In this article we review current knowledge of some of these neurotoxins, their structure, pharmacology, importance as pharmaceutical tools as well as future prospects for the development of therapeutic molecules.
Collapse
Affiliation(s)
- Ron C Hogg
- University of Geneva, Department of Neurosciences Fondamentales, Faculty of Medicine, 1, rue Michel Servet, CH-1211 Geneva 4, Switzerland
| | - Daniel Bertrand
- University of Geneva, Department of Neurosciences Fondamentales, Faculty of Medicine, Switzerland
| |
Collapse
|
20
|
Osipov AV, Kasheverov IE, Makarova YV, Starkov VG, Vorontsova OV, Ziganshin RK, Andreeva TV, Serebryakova MV, Benoit A, Hogg RC, Bertrand D, Tsetlin VI, Utkin YN. Naturally occurring disulfide-bound dimers of three-fingered toxins: a paradigm for biological activity diversification. J Biol Chem 2008; 283:14571-80. [PMID: 18381281 DOI: 10.1074/jbc.m802085200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Disulfide-bound dimers of three-fingered toxins have been discovered in the Naja kaouthia cobra venom; that is, the homodimer of alpha-cobratoxin (a long-chain alpha-neurotoxin) and heterodimers formed by alpha-cobratoxin with different cytotoxins. According to circular dichroism measurements, toxins in dimers retain in general their three-fingered folding. The functionally important disulfide 26-30 in polypeptide loop II of alpha-cobratoxin moiety remains intact in both types of dimers. Biological activity studies showed that cytotoxins within dimers completely lose their cytotoxicity. However, the dimers retain most of the alpha-cobratoxin capacity to compete with alpha-bungarotoxin for binding to Torpedo and alpha7 nicotinic acetylcholine receptors (nAChRs) as well as to Lymnea stagnalis acetylcholine-binding protein. Electrophysiological experiments on neuronal nAChRs expressed in Xenopus oocytes have shown that alpha-cobratoxin dimer not only interacts with alpha7 nAChR but, in contrast to alpha-cobratoxin monomer, also blocks alpha3beta2 nAChR. In the latter activity it resembles kappa-bungarotoxin, a dimer with no disulfides between monomers. These results demonstrate that dimerization is essential for the interaction of three-fingered neurotoxins with heteromeric alpha3beta2 nAChRs.
Collapse
Affiliation(s)
- Alexey V Osipov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Blanchfield JT, Gallagher OP, Cros C, Lewis RJ, Alewood PF, Toth I. Oral absorption and in vivo biodistribution of alpha-conotoxin MII and a lipidic analogue. Biochem Biophys Res Commun 2007; 361:97-102. [PMID: 17640618 DOI: 10.1016/j.bbrc.2007.06.138] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Accepted: 06/28/2007] [Indexed: 11/26/2022]
Abstract
Conotoxins are highly constrained peptide toxins that exhibit pharmaceutically relevant biological activities. We herein report the extent of absorption and profile of distribution of a native alpha-conotoxin, MII and a lipophilic analogue of MII (N-LaaMII) after intravenous (iv) and oral administration to male Sprague-Dawley rats. N-LaaMII is formed by coupling 2-amino-D,L-dodecanoic acid (Laa) to the N-terminus of MII and has previously been shown to exhibit significantly improved permeability across Caco-2 cell monolayers compared to the native MII while maintaining the potency in inhibition of nAChRs of the parent peptide. Both peptides crossed the GI tract after oral administration (approximately 6% after 30 m). While Laa conjugation did not significantly improve absorption, it did greatly increase the accumulation of the compound in the liver after iv administration. Neither peptide crossed the blood-brain barrier to any significant extent. This is the first study of the in vivo biodistribution of an alpha-conotoxin after oral administration.
Collapse
Affiliation(s)
- Joanne T Blanchfield
- School of Molecular and Microbial Sciences, The University of Queensland, Brisbane 4072, Australia
| | | | | | | | | | | |
Collapse
|
22
|
McKay DB, Chang C, González-Cestari TF, McKay SB, El-Hajj RA, Bryant DL, Zhu MX, Swaan PW, Arason KM, Pulipaka AB, Orac CM, Bergmeier SC. Analogs of methyllycaconitine as novel noncompetitive inhibitors of nicotinic receptors: pharmacological characterization, computational modeling, and pharmacophore development. Mol Pharmacol 2007; 71:1288-97. [PMID: 17308033 DOI: 10.1124/mol.106.033233] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
As a novel approach to drug discovery involving neuronal nicotinic acetylcholine receptors (nAChRs), our laboratory targeted nonagonist binding sites (i.e., noncompetitive binding sites, negative allosteric binding sites) located on nAChRs. Cultured bovine adrenal cells were used as neuronal models to investigate interactions of 67 analogs of methyllycaconitine (MLA) on native alpha3beta4* nAChRs. The availability of large numbers of structurally related molecules presents a unique opportunity for the development of pharmacophore models for noncompetitive binding sites. Our MLA analogs inhibited nicotine-mediated functional activation of both native and recombinant alpha3beta4* nAChRs with a wide range of IC(50) values (0.9-115 microM). These analogs had little or no inhibitory effects on agonist binding to native or recombinant nAChRs, supporting noncompetitive inhibitory activity. Based on these data, two highly predictive 3D quantitative structure-activity relationship (comparative molecular field analysis and comparative molecular similarity index analysis) models were generated. These computational models were successfully validated and provided insights into the molecular interactions of MLA analogs with nAChRs. In addition, a pharmacophore model was constructed to analyze and visualize the binding requirements to the analog binding site. The pharmacophore model was subsequently applied to search structurally diverse molecular databases to prospectively identify novel inhibitors. The rapid identification of eight molecules from database mining and our successful demonstration of in vitro inhibitory activity support the utility of these computational models as novel tools for the efficient retrieval of inhibitors. These results demonstrate the effectiveness of computational modeling and pharmacophore development, which may lead to the identification of new therapeutic drugs that target novel sites on nAChRs.
Collapse
Affiliation(s)
- Dennis B McKay
- Division of Pharmacology, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Janhunen S, Ahtee L. Differential nicotinic regulation of the nigrostriatal and mesolimbic dopaminergic pathways: implications for drug development. Neurosci Biobehav Rev 2006; 31:287-314. [PMID: 17141870 DOI: 10.1016/j.neubiorev.2006.09.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 09/10/2006] [Accepted: 09/18/2006] [Indexed: 01/21/2023]
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) modulate dopaminergic function. Discovery of their multiplicity has lead to the search for subtype-selective nAChR agonists that might be therapeutically beneficial in diseases linked to brain dopaminergic pathways. The regulation and responses of the nigrostriatal and mesolimbic dopaminergic pathways are often similar, but some differences do exist. The cerebral distribution and characteristics of various nAChR subtypes differ between nigrostriatal and mesolimbic dopaminergic pathways. Comparison of nicotine and epibatidine, two nAChR agonists whose relative affinities for various nAChR subtypes differ, revealed differences in the nAChR-mediated regulation of dopaminergic activation between these dopamine systems. Nicotine preferentially stimulates the mesolimbic pathway, whereas epibatidine's stimulatory effect falls on the nigrostriatal pathway. Thus, it may be possible to stimulate the nigrostriatal pathway with selective nAChR agonists that do not significantly affect the mesolimbic pathway, and thus lack addictive properties. Furthermore, dopamine uptake inhibition revealed a novel inhibitory effect of epibatidine on accumbal dopamine release, which could form a basis for novel antipsychotics that could alleviate the elevated accumbal dopaminergic tone found in schizophrenia during the active psychotic state. Different regulation of nigrostriatal and mesolimbic dopaminergic pathways by nAChRs could be an important basis for developing novel drugs for treatment of Parkinson's disease and schizophrenia.
Collapse
Affiliation(s)
- Sanna Janhunen
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56 (Viikinkaari 5), Helsinki, FIN-00014, Finland.
| | | |
Collapse
|
24
|
Livett BG, Sandall DW, Keays D, Down J, Gayler KR, Satkunanathan N, Khalil Z. Therapeutic applications of conotoxins that target the neuronal nicotinic acetylcholine receptor. Toxicon 2006; 48:810-29. [PMID: 16979678 DOI: 10.1016/j.toxicon.2006.07.023] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pain therapeutics discovered by molecular mining of the expressed genome of Australian predatory cone snails are providing lead compounds for the treatment of neurological diseases such as multiple sclerosis, shingles, diabetic neuropathy and other painful neurological conditions. The high specificity exhibited by these novel compounds for neuronal receptors and ion channels in the brain and nervous system indicates the high degree of selectivity that this class of neuropeptides can be expected to show when used therapeutically in humans. A lead compound, ACV1 (conotoxin Vc1.1 from Conus victoriae), has entered Phase II clinical trials and is being developed for the treatment for neuropathic pain. ACV1 will be targeted initially for the treatment of sciatica, shingles and diabetic neuropathy. The compound is a 16 amino acid peptide [Sandall et al., 2003. A novel alpha-conotoxin identified by gene sequencing is active in suppressing the vascular response to selective stimulation of sensory nerves in vivo. Biochemistry 42, 6904-6911], an antagonist of neuronal nicotinic acetylcholine receptors. It has potent analgesic activity following subcutaneous or intramuscular administration in several preclinical animal models of human neuropathic pain [Satkunanathan et al., 2005. Alpha conotoxin Vc1.1 alleviates neuropathic pain and accelerates functional recovery of injured neurons. Brain. Res. 1059, 149-158]. ACV1 may act as an analgesic by decreasing ectopic excitation in sensory nerves. In addition ACV1 appears to accelerate the recovery of injured nerves and tissues.
Collapse
Affiliation(s)
- Bruce G Livett
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria 3010, Australia.
| | | | | | | | | | | | | |
Collapse
|
25
|
Kasheverov IE, Utkin IN, Tsetlin VI. [Natural alpha-conotoxins and their synthetic analogues in studies of nicotinic acetylcholine receptors]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2006; 32:115-29. [PMID: 16637282 DOI: 10.1134/s1068162006020014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
alpha-Conotoxins, peptide neurotoxins from poisonous marine snails of the genus Conus that highly specifically block nicotinic acetylcholine receptors (AChRs) of various types, are reviewed. Preliminarily, the structural organization of AChRs of the muscular and neuronal types, their involvement in physiological processes, and their role in various diseases are briefly discussed. In this connection, the necessity of quantitative determination of AChR subtypes using neurotoxins and other approaches is substantiated. The chemical structure, spatial organization, and specificity of alpha-conotoxins are mainly discussed, taking into consideration the recent results on the ability of alpha-conotoxins to interact with muscular or neuronal hetero- and homooligomeric AChRs exhibiting a high species specificity. Particular emphasis is placed upon a thorough characterization of the surfaces of interaction of alpha-conotoxins with AChRs using synthetic analogues of alpha-conotoxins, mutations in AChRs, and pairwise mutations in both alpha-conotoxins and AChRs. The discovery in 2001 of the acetylcholine-binding protein from the pond snail Lymnaea stagnalis and the determination of its crystalline structure led to rapid progress in understanding the structural organization of ligand-binding domains of AChRs with which alpha-conotoxins also interact. We discuss the interaction of various alpha-conotoxins with acetylcholine-binding proteins, the recently reported X-ray structure of the complex of the acetylcholine-binding protein from Aplysia californica with the alpha-conotoxin analogue PnIA, and the application of this structure to the modeling of complexes of alpha-conotoxins with various AChRs.
Collapse
|
26
|
Huang LZ, Hsiao SH, Trzeciakowski J, Frye GD, Winzer-Serhan UH. Chronic nicotine induces growth retardation in neonatal rat pups. Life Sci 2006; 78:1483-93. [PMID: 16324718 DOI: 10.1016/j.lfs.2005.07.047] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Accepted: 07/13/2005] [Indexed: 11/26/2022]
Abstract
In the United State, 20% of pregnant women smoke. One of the most consistent adverse outcomes is reduced birth weight in the off-spring. Animal studies using chronic nicotine, the major psychoactive tobacco ingredient, have shown conflicting results, questioning the role of nicotine in growth retardation. To evaluate the direct effects of nicotine during a period equivalent to the human third trimester, we developed an oral gastric intubation model using neonatal rat pups. Nicotine (6 mg/kg/day) was dissolve in milk-formula and delivered during three feedings daily from postnatal day (P)1 to P7. Nicotine immediately and significantly [P<0.05] decreased weight gain per day (WGD) by 13.5% (+/-) 1 day after onset of treatment in both genders and throughout the treatment period. This resulted in significantly lower body weight at P4 and P5 in male and female pups, respectively. After nicotine withdrawal, WGD returned to control level within 1 day, whereas total body weight recovered by P18. There were no long-term consequences on body weight or growth pattern in either gender. The nicotinic acetylcholine receptor (nAChR) antagonist dihydro-beta-erythroidine (DHbetaE) reversed nicotine's effects on WGD suggesting an involvement of heteromeric alpha4beta2, whereas methyllycaconitine (MLA) an antagonist for the homomeric alpha7-type receptor was ineffective. The immediate decrease of growth in neonatal pups suggests that nicotine's effect on birth weight results from direct anorexic rather then indirect effects due to placental dysfunction or increased fetal hypoxia. The postnatal oral gastric intubation model seems to accurately reflect the direct effects of nicotine in neonates.
Collapse
Affiliation(s)
- Luping Z Huang
- Department of Medical Pharmacology and Toxicology, College of Medicine, Texas A&M University System, Health Sciences Center, College Station, TX, USA
| | | | | | | | | |
Collapse
|
27
|
Sumithran SP, Crooks PA, Xu R, Zhu J, Deaciuc AG, Wilkins LH, Dwoskin LP. Introduction of unsaturation into the N-n-alkyl chain of the nicotinic receptor antagonists, NONI and NDNI: effect on affinity and selectivity. AAPS JOURNAL 2005; 7:E201-17. [PMID: 16146341 PMCID: PMC2751509 DOI: 10.1208/aapsj070119] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
N-n-octylnicotinium iodide (NONI) and N-n-decylnicotinium iodide (NDNI) are selective nicotinic receptor (nAChR) antagonists mediating nicotine-evoked striatal dopamine (DA) release, and inhibiting [3H]nicotine binding, respectively. This study evaluated effects of introducing unsaturation into the N-n-alkyl chains of NONI and NDNI on inhibition of [3H]nicotine and [3H]methyllycaconitine binding (alpha4beta2* and alpha7* nAChRs, respectively), (86)Rb+ efflux and [3H]DA release (agonist or antagonist effects at alpha4beta2* and alpha6beta2*-containing nAChRs, respectively). In the NONI series, introduction of a C3-cis- (NONB3c), C3-trans- (NONB3t), C7-double-bond (NONB7e), or C3-triple-bond (NONB3y) afforded a 4-fold to 250-fold increased affinity for [3H]nicotine binding sites compared with NONI. NONB7e and NONB3y inhibited nicotine-evoked 86Rb+ efflux, indicating alpha4beta2* antagonism. NONI analogs exhibited a 3-fold to 8-fold greater potency inhibiting nicotine-evoked [3H]DA overflow compared with NONI (IC50 = 0.62 microM; Imax = 89%), with no change in Imax, except for NONB3y (Imax = 50%). In the NDNI series, introduction of a C4-cis- (NDNB4c), C4-trans-double-bond (NDNB4t), or C3-triple-bond (NDNB3y) afforded a 4-fold to 80-fold decreased affinity for [3H]nicotine binding sites compared with NDNI, whereas introduction of a C9 double-bond (NDNB9e) did not alter affinity. NDNB3y and NDNB4t inhibited nicotine-evoked 86Rb+ efflux, indicating antagonism at alpha4beta2* nAChRs. Although NDNI had no effect, NDNB4t and NDNB9e potently inhibited nicotine-evoked [3H]DA overflow (IC50 = 0.02-0.14 microM, Imax = 90%), as did NDNB4c (IC50 = 0.08 microM; Imax = 50%), whereas NDNB3y showed no inhibition. None of the analogs had significant affinity for alpha7* nAChRs. Thus, unsaturated NONI analogs had enhanced affinity at alpha4beta2*- and alpha6beta2*-containing nAChRs, however a general reduction of affinity at alpha4beta2* and an uncovering of antagonist effects at alpha6beta2*-containing nAChRs were observed with unsaturated NDNI analogs.
Collapse
Affiliation(s)
| | - Peter A. Crooks
- College of Pharmacy, University of Kentucky, 40536-0082 Lexington, KY
| | - Rui Xu
- College of Pharmacy, University of Kentucky, 40536-0082 Lexington, KY
| | - Jun Zhu
- College of Pharmacy, University of Kentucky, 40536-0082 Lexington, KY
| | | | | | - Linda P. Dwoskin
- College of Pharmacy, University of Kentucky, 40536-0082 Lexington, KY
| |
Collapse
|
28
|
Daly JW. Nicotinic Agonists, Antagonists, and Modulators From Natural Sources. Cell Mol Neurobiol 2005; 25:513-52. [PMID: 16075378 DOI: 10.1007/s10571-005-3968-4] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Accepted: 04/14/2004] [Indexed: 10/25/2022]
Abstract
1. Acetylcholine receptors were initially defined as nicotinic or muscarinic, based on selective activation by two natural products, nicotine and muscarine. Several further nicotinic agonists have been discovered from natural sources, including cytisine, anatoxin, ferruginine, anabaseine, epibatidine, and epiquinamide. These have provided lead structures for the design of a wide range of synthetic agents. 2. Natural sources have also provided competitive nicotinic antagonists, such as the Erythrina alkaloids, the tubocurarines, and methyllycaconitine. Noncompetitive antagonists, such as the histrionicotoxins, various izidines, decahydroquinolines, spiropyrrolizidine oximes, pseudophrynamines, ibogaine, strychnine, cocaine, and sparteine have come from natural sources. Finally, galanthamine, codeine, and ivermectin represent positive modulators of nicotinic function, derived from natural sources. 3. Clearly, research on acetylcholine receptors and functions has been dependent on key natural products and the synthetic agents that they inspired.
Collapse
Affiliation(s)
- John W Daly
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892, USA.
| |
Collapse
|
29
|
Lin NH, Meyer MD. Recent developments in neuronal nicotinic acetylcholine receptor modulators. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.8.8.991] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
30
|
Dwoskin LP, Xu R, Ayers JT, Crooks PA. Recent developments in neuronal nicotinic acetylcholine receptor antagonists. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.10.10.1561] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
31
|
Dwoskin LP, Sumithran SP, Zhu J, Deaciuc AG, Ayers JT, Crooks PA. Subtype-selective nicotinic receptor antagonists: potential as tobacco use cessation agents. Bioorg Med Chem Lett 2004; 14:1863-7. [PMID: 15050617 DOI: 10.1016/j.bmcl.2003.10.073] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2003] [Indexed: 11/15/2022]
Abstract
N-n-Alkylpicolinium and N,N'-alkyl-bis-picolinium analogues were assessed in nicotinic receptor (nAChR) assays. The most potent and subtype-selective analogue, N,N'-dodecyl-bis-picolinium bromide (bPiDDB), inhibited nAChRs mediating nicotine-evoked [(3)H]dopamine release (IC(50)=5 nM; I(max) of 60%), and did not interact with alpha4beta2* or alpha7* nAChRs. bPiDDB represents the current lead compound for development as a tobacco use cessation agent.
Collapse
Affiliation(s)
- Linda P Dwoskin
- Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA.
| | | | | | | | | | | |
Collapse
|
32
|
Haberberger RV, Bernardini N, Kress M, Hartmann P, Lips KS, Kummer W. Nicotinic acetylcholine receptor subtypes in nociceptive dorsal root ganglion neurons of the adult rat. Auton Neurosci 2004; 113:32-42. [PMID: 15296793 DOI: 10.1016/j.autneu.2004.05.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Revised: 05/03/2004] [Accepted: 05/13/2004] [Indexed: 10/26/2022]
Abstract
Stimulation of nicotinic acetylcholine receptors (nAChR) excites peripheral sensory nerve fibres, but also exert antinociceptive effects. The differences in these nAChR-mediated effects could be related to the expression of different nAChR subtypes located on nociceptive neurons. In the present study, we focused on the recently described alpha 10-nAChR subunit, and on alpha 4 and alpha 7 subunits, which are the most abundant subunits in the central nervous system. In nociceptive neurons from thoracic and lumbar dorsal root ganglia (DRG), nAChR subunits were found at transcriptional (RT-PCR), translational (immunohistochemistry) and functional levels. Cultured DRG neurons express mRNA for the subunits alpha 2-7 and alpha 10. The alpha-subunit proteins 4, 7 and 10 were colocalised in virtually all nociceptive neurons that were identified by immunoreactivity for the vanilloid receptor TRPV-1. These findings were corroborated by current recordings and calcium measurements, which revealed excitatory inward currents and calcium responses in capsaicin sensitive neurons.
Collapse
Affiliation(s)
- Rainer Viktor Haberberger
- Institute for Anatomy and Cell Biology Justus Liebig University, Aulweg 123, D-35385 Giessen, Germany.
| | | | | | | | | | | |
Collapse
|
33
|
Nicotinic acetylcholine receptors in the nervous system. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s1569-2558(03)32012-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
|
34
|
Grinevich VP, Crooks PA, Sumithran SP, Haubner AJ, Ayers JT, Dwoskin LP. N-n-alkylpyridinium analogs, a novel class of nicotinic receptor antagonists: selective inhibition of nicotine-evoked [3H] dopamine overflow from superfused rat striatal slices. J Pharmacol Exp Ther 2003; 306:1011-20. [PMID: 12766255 DOI: 10.1124/jpet.103.051789] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Structural simplification of N-n-alkylnicotinium analogs, antagonists at neuronal nicotinic acetylcholine receptors (nAChRs), was achieved by removal of the N-methylpyrrolidino moiety affording N-n-alkylpyridinium analogs with carbon chain lengths of C1 to C20. N-n-Alkylpyridinium analog inhibition of [3H]nicotine and [3H]methyllycaconitine binding to rat brain membranes assessed interaction with alpha4beta2* and alpha7* nAChRs, respectively, whereas inhibition of nicotine-evoked 3H overflow from [3H]dopamine ([3H]DA)-preloaded rat striatal slices assessed antagonist action at nAChR subtypes mediating nicotine-evoked DA release. No inhibition of [3H]methyllycaconitine binding was observed, although N-n-alkylpyridinium analogs had low affinity for [3H]nicotine binding sites, i.e., 1 to 3 orders of magnitude lower than that of the respective N-n-alkylnicotinium analogs. These results indicate that the N-methylpyrrolidino moiety in the N-n-alkylnicotinium analogs is a structural requirement for potent inhibition of alpha4beta2* nAChRs. Importantly, N-n-alkylpyridinium analogs with n-alkyl chains < C10 did not inhibit nicotine-evoked [3H]DA overflow, whereas analogs with n-alkyl chains ranging from C10 to C20 potently and completely inhibited nicotine-evoked [3H]DA overflow (IC50 = 0.12-0.49 microM), with the exceptions of N-n-pentadecylpyridinium bromide (C15) and N-n-eicosylpyridinium bromide (C20), which exhibited maximal inhibition of approximately 50%. The mechanism of inhibition of a representative analog of this structural series, N-n-dodecylpyridinium iodide, was determined by Schild analysis. Linear Schild regression with slope not different from unity indicated competitive antagonism at nAChRs mediating nicotine-evoked [3H]DA overflow and a KB value of 0.17 microM. Thus, the simplified N-n-alkylpyridinium analogs are potent, selective, and competitive antagonists of nAChRs mediating nicotine-evoked [3H]DA overflow, indicating that the N-methylpyrrolidino moiety is not a structural requirement for interaction with nAChR subtypes mediating nicotine-evoked DA release.
Collapse
|
35
|
Sandall DW, Satkunanathan N, Keays DA, Polidano MA, Liping X, Pham V, Down JG, Khalil Z, Livett BG, Gayler KR. A novel alpha-conotoxin identified by gene sequencing is active in suppressing the vascular response to selective stimulation of sensory nerves in vivo. Biochemistry 2003; 42:6904-11. [PMID: 12779345 DOI: 10.1021/bi034043e] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe the identification of a conopeptide sequence in venom duct mRNA from Conus victoriae that suppresses a vascular response to pain in the rat. PCR-RACE was used to screen venom duct cDNAs for those transcripts that encode specific antagonists of vertebrate neuronal nicotinic acetylcholine receptors (nAChRs). One of these peptides, Vc1.1, was active as an antagonist of neuronal nAChRs in receptor binding and functional studies in bovine chromaffin cells. It also suppressed the vascular responses to unmyelinated sensory nerve C-fiber activation in rats. Such vascular responses are involved in pain transmission. Furthermore, its ability to suppress C-fiber function was greater than that of MVIIA, an omega-conotoxin with known analgesic activity in rats and humans. Vc1.1 has a high degree of sequence similarity to the alpha-conotoxin family of peptides and has the 4,7 loop structure characteristic of the subfamily of peptides that act on neuronal-type nAChRs. The results suggest that neuronal alpha-conotoxins should be further investigated with respect to their potential to suppress pain.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Cattle
- Chromaffin Cells/drug effects
- Chromaffin Cells/metabolism
- Conotoxins/genetics
- Conotoxins/pharmacology
- DNA, Complementary/genetics
- Dose-Response Relationship, Drug
- Male
- Molecular Sequence Data
- Nerve Fibers, Unmyelinated/drug effects
- Nerve Fibers, Unmyelinated/physiology
- Neuromuscular Junction/drug effects
- Neuromuscular Junction/physiology
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Nicotinic Antagonists/pharmacology
- Polymerase Chain Reaction/methods
- RNA, Messenger/genetics
- Rats
- Rats, Sprague-Dawley
- Receptors, Nicotinic/physiology
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- omega-Conotoxins/pharmacology
Collapse
Affiliation(s)
- D W Sandall
- Department of Biochemistry and Molecular Biology and National Ageing Research Institute, The University of Melbourne, Victoria 3010, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Lucas-Meunier E, Fossier P, Baux G, Amar M. Cholinergic modulation of the cortical neuronal network. Pflugers Arch 2003; 446:17-29. [PMID: 12690458 DOI: 10.1007/s00424-002-0999-2] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2002] [Indexed: 01/15/2023]
Abstract
Acetylcholine (ACh) is an important neurotransmitter of the CNS that binds both nicotinic and muscarinic receptors to exert its action. However, the mechanisms underlying the effects of cholinergic receptors have still not been completely elucidated. Central cholinergic neurons, mainly located in basal forebrain, send their projections to different structures including the cortex. The cortical innervation is diffuse and roughly topographic, which has prompted some authors to suspect a modulating role of ACh on the activity of the cortical network rather than a direct synaptic role. The cholinergic system is implicated in functional, behavioural and pathological states including cognitive function, nicotine addiction, Alzheimer's disease, Tourette's syndrome, epilepsies and schizophrenia. As these processes depend on the activation of glutamatergic and GABAergic systems, the cholinergic terminals must exert their effects via the modulation of excitatory and/or inhibitory neurotransmission. However, the understanding of cholinergic modulation is complex because it is the result of a mixture of positive and negative modulation, implying that there are various types, or even subtypes, of cholinergic receptors. In this review, we summarize the current knowledge on central cholinergic systems (projections and receptors) and then aim to focus on the implications for ACh in the modulation of cortical neuronal activity.
Collapse
Affiliation(s)
- E Lucas-Meunier
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, INAF-CNRS, 1 avenue de la Terrasse, 91198 Gif-sur-Yvette cedex, France.
| | | | | | | |
Collapse
|
37
|
Blanchfield JT, Dutton JL, Hogg RC, Gallagher OP, Craik DJ, Jones A, Adams DJ, Lewis RJ, Alewood PF, Toth I. Synthesis, structure elucidation, in vitro biological activity, toxicity, and Caco-2 cell permeability of lipophilic analogues of alpha-conotoxin MII. J Med Chem 2003; 46:1266-72. [PMID: 12646037 DOI: 10.1021/jm020426j] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The alpha-conotoxin MII is a two disulfide bridge containing, 16 amino acid long peptide toxin isolated from the marine snail Conus magus. This toxin has been found to be a highly selective and potent inhibitor of neuronal nicotinic acetylcholine receptors (nAChRs) of the subtype alpha3beta2. To improve the bioavailability of this peptide, two lipidic analogues of MII have been synthesized, the first by coupling 2-amino-d,l-dodecanoic acid (Laa) to the N terminus (LaaMII) and the second by replacing Asn5 in the MII sequence with this lipoamino acid (5LaaMII). Both lipidic linear peptides were then oxidized under standard conditions. (1)H NMR shift analysis of these peptides and comparison with the native MII peptide showed that the tertiary structure of the N-conjugated analogue, LaaMII, was consistent with that of the native conotoxin, whereas the 5LaaMII analogue formed the correct disulfide bridges but failed to adopt the native helical tertiary structure. The N terminus conjugate was also found to inhibit nAChRs of the subtype alpha3beta2 with equal potency to the parent peptide, whereas the 5LaaMII analogue showed no inhibitory activity. The active LaaMII analogue was found to exhibit significantly improved permeability across Caco-2 cell monolayers compared to the native MII, and both peptides showed negligible toxicity.
Collapse
Affiliation(s)
- Joanne T Blanchfield
- School of Pharmacy, Institute for Molecular Bioscience, and School of Biomedical Sciences, The University of Queensland, Brisbane 4072, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Wilkins LH, Grinevich VP, Ayers JT, Crooks PA, Dwoskin LP. N-n-alkylnicotinium analogs, a novel class of nicotinic receptor antagonists: interaction with alpha4beta2* and alpha7* neuronal nicotinic receptors. J Pharmacol Exp Ther 2003; 304:400-10. [PMID: 12490617 DOI: 10.1124/jpet.102.043349] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The current study demonstrates that N-n-alkylnicotinium analogs with increasing n-alkyl chain lengths from 1 to 12 carbons have varying affinity (Ki = 90 nM-20 microM) for S-(-)-[3H]nicotine binding sites in rat striatal membranes. A linear relationship was observed such that increasing n-alkyl chain length provided increased affinity for the alpha4beta2* nicotinic acetylcholine receptor (nAChR) subtype, with the exception of N-n-octylnicotinium iodide (NONI). The most potent analog was N-n-decylnicotinium iodide (NDNI; Ki = 90 nM). In contrast, none of the analogs in this series exhibited high affinity for the [3H]methyllycaconitine binding site, thus indicating low affinity for the alpha7* nAChR. The C8 analog, NONI, had low affinity for S-(-)-[3H]nicotine binding sites but was a potent inhibitor of S-(-)-nicotine-evoked [3H]dopamine (DA) overflow from superfused striatal slices (IC50 = 0.62 microM), thereby demonstrating selectivity for the nAChR subtype mediating S-(-)-nicotine-evoked [3H]DA overflow (alpha3alpha6beta2* nAChRs). Importantly, the N-n-alkylnicotinium analog with highest affinity for the alpha4beta2* subtype, NDNI, lacked the ability to inhibit S-(-)-nicotine-evoked [3H]DA overflow and, thus, appears to be selective for alpha4beta2* nAChRs. Furthermore, the present study demonstrates that the interaction of these analogs with the alpha4beta2* subtype is via a competitive mechanism. Thus, selectivity for the alpha4beta2* subtype combined with competitive interaction with the S-(-)-nicotine binding site indicates that NDNI is an excellent candidate for studying the structural topography of alpha4beta2* agonist recognition binding sites, for identifying the antagonist pharmacophore on the alpha4beta2* nAChR, and for defining the role of this subtype in physiological function and pathological disease states.
Collapse
Affiliation(s)
- Lincoln H Wilkins
- College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536-0082, USA.
| | | | | | | | | |
Collapse
|
39
|
Rashid MH, Ueda H. Neuropathy-specific analgesic action of intrathecal nicotinic agonists and its spinal GABA-mediated mechanism. Brain Res 2002; 953:53-62. [PMID: 12384238 DOI: 10.1016/s0006-8993(02)03270-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of the nicotinic acetylcholine receptor (nAChR) agonists at the spinal level has not been well studied in neuropathic states. In the present report, we demonstrate the efficacy of intrathecal nicotinic agonists in partial sciatic nerve injury-induced neuropathy model mice. Intrathecal (i.t.) administration of (-)nicotine and (+)epibatidine, at doses without undesirable effects, had no antinociceptive action in sham-operated mice. However, they completely reversed the thermal and mechanical hyperalgesia in partial sciatic nerve-injured mice. This neuropathy-specific analgesic action of i.t. (-)nicotine and (+)epibatidine is attributed to different subtypes of nAChRs at the spinal level. After antagonism experiments with mecamylamine, dihydro-beta-erythroidine and methyllycaconitine, it was observed that (-)nicotine-induced analgesia was mediated through the alpha4beta2 subtype of nAChR while the (+)epibatidine-induced one was mediated through non-alpha4beta2 subtype of nAChR. Moreover, i.t. pretreatment with NMDA receptor antagonist did not block nicotinic analgesia. Similar to nicotinic agonists, gamma-aminobutyric acid receptor (GABA(A)) agonist muscimol (i.t.) produced neuropathy-specific analgesic action giving analgesia only in nerve-injured mice. The GABA(A) antagonists bicuculline and picrotoxin significantly blocked the analgesic effects of muscimol as well as that of (-)nicotine and (+)epibatidine. On the other hand, i.t. injection of nicotinic antagonist mecamylamine and GABA(A) antagonist picrotoxin in sham-operated mice induced a thermal hyperalgesia without any effects in nerve-injured animals suggesting the presence of a tonic inhibitory tone on nociceptive transmission through the spinal cholinergic-GABAergic system. These results also suggest that the neuropathy-specific analgesic action of intrathecal nicotinic agonists was due to stimulation of this cholinergic-GABAergic system whose inhibitory tone had been reduced due to injury.
Collapse
Affiliation(s)
- Md Haronur Rashid
- Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
| | | |
Collapse
|
40
|
Miller DK, Sumithran SP, Dwoskin LP. Bupropion inhibits nicotine-evoked [(3)H]overflow from rat striatal slices preloaded with [(3)H]dopamine and from rat hippocampal slices preloaded with [(3)H]norepinephrine. J Pharmacol Exp Ther 2002; 302:1113-22. [PMID: 12183670 DOI: 10.1124/jpet.102.033852] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bupropion, an efficacious antidepressant and smoking cessation agent, inhibits dopamine and norepinephrine transporters (DAT and NET, respectively). Recently, bupropion has been reported to noncompetitively inhibit alpha3beta2, alpha3beta4, and alpha4beta2 nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes or established cell lines. The present study evaluated bupropion-induced inhibition of native alpha3beta2* and alpha3beta4* nAChRs using functional neurotransmitter release assays, nicotine-evoked [(3)H]overflow from superfused rat striatal slices preloaded with [(3)H]dopamine ([(3)H]DA), and nicotine-evoked [(3)H]overflow from hippocampal slices preloaded with [(3)H]norepinephrine ([(3)H]NE). The mechanism of inhibition was evaluated using Schild analysis. To eliminate the interaction of bupropion with DAT or NET, nomifensine or desipramine, respectively, was included in the superfusion buffer. A high bupropion concentration (100 microM) elicited intrinsic activity in the [(3)H]DA release assay. However, none of the concentrations (1 nM-100 microM) examined evoked [(3)H]NE overflow and, thus, were without intrinsic activity in this assay. Moreover, bupropion inhibited both nicotine-evoked [(3)H]DA overflow (IC(50) = 1.27 microM) and nicotine-evoked [(3)H]NE overflow (IC(50) = 323 nM) at bupropion concentrations well below those eliciting intrinsic activity. Results from Schild analyses suggest that bupropion competitively inhibits nicotine-evoked [(3)H]DA overflow, whereas evidence for receptor reserve was obtained upon assessment of bupropion inhibition of nicotine-evoked [(3)H]NE overflow. Thus, bupropion acts as an antagonist at alpha3beta2* and alpha3beta4* nAChRs in rat striatum and hippocampus, respectively, across the same concentration range that inhibits DAT and NET function. The combination of nAChR and transporter inhibition produced by bupropion may contribute to its clinical efficacy as a smoking cessation agent.
Collapse
Affiliation(s)
- Dennis K Miller
- College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA
| | | | | |
Collapse
|
41
|
Guo JZ, Chiappinelli VA. A novel choline-sensitive nicotinic receptor subtype that mediates enhanced GABA release in the chick ventral lateral geniculate nucleus. Neuroscience 2002; 110:505-13. [PMID: 11906789 DOI: 10.1016/s0306-4522(01)00579-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Nicotinic acetylcholine receptors modulate the release of GABA, glutamate, acetylcholine and dopamine in the brain. Here we describe a novel choline-sensitive nicotinic acetylcholine receptor that mediates enhanced GABA release in the chick ventral lateral geniculate nucleus. Whole-cell recordings in slices demonstrated that choline (0.03-10 mM), generally considered an alpha7-selective agonist, and carbachol (3-300 microM), a non-selective cholinergic agonist, both increased the frequency of spontaneous GABAergic events in ventral lateral geniculate nucleus neurons. Tetrodotoxin (0.5 microM) partially reduced responses to carbachol, but eliminated responses to choline. During long-term (5 min) exposure to choline the GABA enhancement was maintained until choline was washed out. Choline (300 microM) enhanced the frequency of spontaneous GABAergic events by 4.28-fold in control artificial cerebrospinal fluid. This choline-mediated enhancement was significantly reduced by the following nicotinic acetylcholine receptor antagonists: 1 microM dihydro-beta-erythroidine (1.49-fold increase, P<0.001), 1 microM methyllycaconitine (1.53-fold, P<0.001) and 0.2 microM alpha-conotoxin ImI (1.84-fold, P<0.001). In contrast, no significant change was seen in the presence of 0.1 microM dihydro-beta-erythroidine, 0.1 microM methyllycaconitine, 0.1 microM alpha-bungarotoxin, 0.1 microM alpha-conotoxin MII, 0.1 microM kappa-bungarotoxin, or 1 microM alpha-conotoxin AuIB. These results indicate that choline, at concentrations as low as 100 microM, activates a nicotinic acetylcholine receptor that is distinct from the classical alpha7 nicotinic acetylcholine receptors previously known to be activated by choline.
Collapse
Affiliation(s)
- J-Z Guo
- Department of Pharmacology, The George Washington University, School of Medicine and Health Sciences, 2300 Eye Street, N.W., Washington, DC 20037, USA.
| | | |
Collapse
|
42
|
Wilkins LH, Haubner A, Ayers JT, Crooks PA, Dwoskin LP. N-n-alkylnicotinium analogs, a novel class of nicotinic receptor antagonist: inhibition of S(-)-nicotine-evoked [(3)H]dopamine overflow from superfused rat striatal slices. J Pharmacol Exp Ther 2002; 301:1088-96. [PMID: 12023541 DOI: 10.1124/jpet.301.3.1088] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The structure of the S(-)-nicotine molecule was modified via N-n-alkylation of the pyridine-N atom to afford a series of N-n-alkylnicotinium iodide salts with carbon chain lengths varying between C(1) and C(12). The ability of these analogs to evoke [(3)H] overflow and inhibit S(-)-nicotine-evoked [(3)H] overflow from [(3)H]dopamine ([(3)H]DA)-preloaded rat striatal slices was determined. At high concentrations, analogs with chain lengths > or =C(6) evoked [(3)H] overflow. Specifically, N-n-decylnicotinium iodide (NDNI; C(10)) evoked significant [(3)H] overflow at 1 microM, and N-n-dodecylnicotinium iodide (NDDNI; C(12)) at 10 microM, whereas N-n-octylnicotinium iodide (NONI; C(8)), N-n-heptylnicotinium iodide (NHpNI; C(7)), and N-n-hexylnicotinium iodide (C(6)) evoked [(3)H] overflow at 100 microM. Thus, intrinsic activity at these concentrations prohibited assessment of inhibitory activity. The most potent N-n-alkylnicotinium analog to inhibit S(-)-nicotine-evoked [(3)H] overflow was NDDNI, with an IC(50) value of 9 nM. NHpNI, NONI, and N-n-nonylnicotinium iodide (C(9)) also inhibited S(-)-nicotine-evoked [(3)H] overflow with IC(50) values of 0.80, 0.62, and 0.21 microM, respectively. In comparison, the competitive neuronal nicotinic acetylcholine receptor (nAChR) antagonist, dihydro-beta-erythroidine, had an IC(50) of 1.6 microM. A significant correlation of N-n-alkyl chain length with analog-induced inhibition was observed, with the exception of NDNI, which was devoid of inhibitory activity. The mechanism of N-n-alkylnicotinium-induced inhibition of the high-affinity, low-capacity component of S(-)-nicotine-evoked [(3)H] overflow was determined via Schild analysis, using the representative analog, NONI. Linear Schild regression and slope not different from unity suggested that NONI competitively interacts with a single nAChR subtype to inhibit S(-)-nicotine-evoked [(3)H]DA release (K(i) value = 80.2 nM). Thus, modification of the S(-)-nicotine molecule converts this agonist into an antagonist at nAChRs, mediating S(-)-nicotine-evoked DA release in striatum.
Collapse
Affiliation(s)
- Lincoln H Wilkins
- College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA
| | | | | | | | | |
Collapse
|
43
|
Levin ED, Bradley A, Addy N, Sigurani N. Hippocampal alpha 7 and alpha 4 beta 2 nicotinic receptors and working memory. Neuroscience 2002; 109:757-65. [PMID: 11927157 DOI: 10.1016/s0306-4522(01)00538-3] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nicotine and other nicotinic receptor agonists have been found in a variety of studies to improve memory, while nicotinic receptor blockade can impair memory. The critical neural mechanisms for nicotinic involvement with memory are still under investigation. Initial evidence supports the involvement of the ventral hippocampus. Lesions in this area block nicotine-induced memory improvement and mecamylamine-induced impairment. Local ventral hippocampal application of the nicotinic channel blocker mecamylamine impairs memory in the 8-arm radial maze. Both alpha 4 beta 2 and alpha 7 nicotinic receptors seem to be involved. Ventral hippocampal infusions of high doses of the alpha 4 beta 2 nicotinic antagonist dihydro-beta-erythrodine (DH beta E) and the alpha 7 nicotinic antagonist methyllycaconitine (MLA) impair memory performance on the 8-arm radial maze. However, high doses of these drugs may limit specificity and they cause preconvulsant effects, which in themselves may affect memory. The current study used the more challenging 16-arm radial maze to determine the effects of lower doses of these drugs on memory and to differentiate effects on working and reference memory. Adult female Sprague-Dawley rats were trained on a working and reference memory task in the 16-arm radial maze and then were implanted with bilateral chronic guide cannulae directed to the ventral hippocampus. After recovery from surgery, the rats received acute intrahippocampal infusions of dose combinations of DH beta E and MLA. In the first study, DH beta E (0 and 6.75 microg/side) and MLA (0, 6.75, 13.5 and 27 microg/side) were administered in a counter-balanced order. In the second study, lower doses of DH beta E (0, 1.6375, 3.275 and 6.75 microg/side) were administered alone or with MLA (0 and 6.75 microg/side) in a counter-balanced order. In the first study, DH beta E caused a significant increase in both working and reference memory errors. MLA at a dose of 27 microg/side caused a significant increase in working memory errors, but this dose had no significant effect on reference memory errors. Interestingly, no additive effects were seen with combined administration of DH beta E and MLA in this study, and at the doses used, no effects were seen on response latency. In the second study, lower doses of DH beta E did not cause a significant deficit in working memory performance. Co-administration of MLA with these subthreshold doses did precipitate a memory impairment. The current results confirm the specificity of the memory deficits caused by these drugs. These results support the involvement of alpha 4 beta 2 and alpha 7 nicotinic receptors in the ventral hippocampus as being critical for memory function.
Collapse
Affiliation(s)
- E D Levin
- Department of Psychiatry and Behavioral Sciences, P.O. Box 3412, Duke University Medical Center, Durham, NC 27710, USA.
| | | | | | | |
Collapse
|
44
|
Smith AB, Hansen MA, Liu DM, Adams DJ. Pre- and postsynaptic actions of ATP on neurotransmission in rat submandibular ganglia. Neuroscience 2002; 107:283-91. [PMID: 11731102 DOI: 10.1016/s0306-4522(01)00347-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The pre- and postsynaptic actions of exogenously applied ATP were investigated in intact and dissociated parasympathetic neurones of rat submandibular ganglia. Nerve-evoked excitatory postsynaptic potentials (EPSPs) were not inhibited by the purinergic receptor antagonists, suramin and pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), or the desensitising agonist, alpha,beta-methylene ATP. In contrast, EPSPs were abolished by the nicotinic acetylcholine receptor antagonists, hexamethonium and mecamylamine. Focal application of ATP (100 microM) had no effect on membrane potential of the postsynaptic neurone or on the amplitude of spontaneous EPSPs. Taken together, these results suggest the absence of functional purinergic (P2) receptors on the postganglionic neurone in situ. In contrast, focally applied ATP (100 microM) reversibly inhibited nerve-evoked EPSPs. Similarly, bath application of the non-hydrolysable analogue of ATP, ATP gamma S, reversibly depressed EPSPs amplitude. The inhibitory effects of ATP and ATP gamma S on nerve-evoked transmitter release were antagonised by bath application of either PPADS or suramin, suggesting ATP activates a presynaptic P2 purinoceptor to inhibit acetylcholine release from preganglionic nerves in the submandibular ganglia. In acutely dissociated postganglionic neurones from rat submandibular ganglia, focal application of ATP (100 microM) evoked an inward current and subsequent excitatory response and action potential firing, which was reversibly inhibited by PPADS (10 microM). The expression of P2X purinoceptors in wholemount and dissociated submandibular ganglion neurones was examined using polyclonal antibodies raised against the extracellular domain of six P2X purinoceptor subtypes (P2X(1-6)). In intact wholemount preparations, only the P2X(5) purinoceptor subtype was found to be expressed in the submandibular ganglion neurones and no P2X immunoreactivity was detected in the nerve fibres innervating the ganglion. Surprisingly, in dissociated submandibular ganglion neurones, high levels of P2X(2) and P2X(4) purinoceptors immunoreactivity were found on the cell surface. This increase in expression of P2X(2) and P2X(4) purinoceptors in dissociated submandibular neurones could explain the increased responsiveness of the neurones to exogenous ATP. We conclude that disruption of ganglionic transmission in vivo by either nerve damage or synaptic blockade may up-regulate P2X expression or availability and alter neuronal excitability.
Collapse
Affiliation(s)
- A B Smith
- School of Biomedical Sciences, Department of Physiology and Pharmacology, University of Queensland, Brisbane, Qld 4072, Australia
| | | | | | | |
Collapse
|
45
|
Bryant DL, Free RB, Thomasy SM, Lapinsky DJ, Ismail KA, McKay SB, Bergmeier SC, McKay DB. Structure-activity studies with ring E analogues of methyllycaconitine on bovine adrenal alpha3beta4* nicotinic receptors. Neurosci Res 2002; 42:57-63. [PMID: 11814609 DOI: 10.1016/s0168-0102(01)00304-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The development of new agents that selectively interact with subtypes of neuronal nicotinic receptors (nAChRs) is of primary importance for the study of physiological processes and pathophysiological conditions involving these receptors. Our laboratory has evidence that simple ring E analogues of methyllycaconitine (MLA) act as antagonists to bovine adrenal alpha3beta4* nAChRs. The following studies were designed to characterize the concentration-response effects of several ring E analogues of MLA in order to assess structural requirements involved with their inhibitory activity on bovine adrenal alpha3beta4* nAChRs. Ring E analogues with various substitutions on the ring E nitrogen were tested for their ability to inhibit nicotinic stimulated adrenal catecholamine release and [3H]epibatidine binding to a bovine adrenal membrane preparation. Several N-alkyl derivatives inhibited secretion with IC50 values in the low micromolar range. The N-phenpropyl analogue was the most potent of the analogues tested (IC50, 11 microM) on adrenal secretion. Competition binding studies suggest a noncompetitive interaction of the analogues with bovine adrenal nAChRs. These studies identify several structural features of ring E analogues of MLA which significantly affect their inhibitory activity on bovine adrenal alpha3beta4* nAChRs.
Collapse
Affiliation(s)
- Darrell L Bryant
- Division of Pharmacology, The Ohio State University, College of Pharmacy, 500 West 12th Avenue, Columbus, OH 43210, USA
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Connolly JG, Kennedy C. The use of electrophysiology to improve understanding of drug-receptor interactions. J Recept Signal Transduct Res 2001; 21:191-214. [PMID: 11757683 DOI: 10.1081/rrs-100107428] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
47
|
Nayak SV, Dougherty JJ, McIntosh JM, Nichols RA. Ca(2+) changes induced by different presynaptic nicotinic receptors in separate populations of individual striatal nerve terminals. J Neurochem 2001; 76:1860-70. [PMID: 11259504 DOI: 10.1046/j.1471-4159.2001.00197.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Presynaptic nicotinic acetylcholine receptors likely play a modulatory role in the nerve terminal. Using laser-scanning confocal microscopy, we have characterized physiological responses obtained on activation of presynaptic nicotinic receptors by measuring calcium changes in individual nerve terminals (synaptosomes) isolated from the rat corpus striatum. Nicotine (500 nM) induced Ca(2+) changes in a subset (10-25%) of synaptosomes. The Ca(2+) responses were dependent on extracellular Ca(2+) and desensitized very slowly (several minutes) on prolonged exposure to agonist. The nicotine-induced Ca(2+) responses were dose-dependent and were completely blocked by dihydro-beta-erythroidine (5 microM), differentially affected by mecamylamine (10 microM) and alpha-conotoxin MII (100 nM), and not affected by alpha-bungarotoxin (500 nM). Immunocytochemical studies using well-characterized monoclonal antibodies revealed the presence of the alpha4 and alpha3/alpha5 nicotinic subunits. The nicotine-induced responses were unaffected by prior depolarization or by a mixture of Ca(2+) channel toxins including omega-conotoxin MVIIC (500 nM), omega-conotoxin GVIA (500 nM) and agatoxin TK (200 nM). Our results indicate that nicotinic receptors present on striatal nerve terminals induce Ca(2+) entry largely without involving voltage-gated Ca(2+) channels, most likely by direct permeation via the receptor channel itself. In addition, at least two subpopulations of presynaptic nicotinic receptors reside on separate terminals in the striatum, suggesting distinct modulatory roles.
Collapse
Affiliation(s)
- S V Nayak
- Department of Pharmacology and Physiology, Medical College of Pennsylvania/Hahnemann University, Philadelphia 19102, USA
| | | | | | | |
Collapse
|
48
|
Free RB, McKay DB. Receptor protection studies to characterize neuronal nicotinic receptors: tubocurarine prevents alkylation of adrenal nicotinic receptors. Brain Res 2001; 891:176-84. [PMID: 11164821 DOI: 10.1016/s0006-8993(00)03204-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Our laboratory has evidence that multiple nicotinic acetylcholine receptor subtypes regulate bovine adrenal catecholamine release. In the following studies, receptor protection assays were used to differentiate adrenal nicotinic receptor subpopulations. Under alkylating conditions, bromoacetylcholine (30 microM) reduced nicotinic receptor-stimulated adrenal catecholamine secretion by approximately 80%. When 100 microM tubocurarine was present during alkylation, nicotine-stimulated secretion was reduced by less than 30%. Hexamethonium (500 microM), decamethonium (500 microM), mecamylamine (50 microM), pentolinium (50 microM), adiphenine (50 microM), methyllycaconitine (1 microM) and alpha-bungarotoxin (1 microM) afforded no protection when present during alkylation. When the pharmacology of residual, tubocurarine-protected receptors was investigated, the EC50 value for nicotine's stimulatory effects on secretion significantly increased from 4.0 (2.5-6.5) microM in control cells to 9.1 (7.2-11.4) microM in tubocurarine-protected cells. In addition, the IC50 value for tubocurarine's inhibitory effects on release significantly decreased from 0.7 (0.5-0.9) microM in control cells to 0.3 (0.2-0.4) microM in tubocurarine-protected cells. These studies support the use of protection assays to characterize nicotinic receptor subpopulations.
Collapse
Affiliation(s)
- R B Free
- Division of Pharmacology, The Ohio State University, College of Pharmacy, 500 West 12th Avenue, Columbus, OH 43210, USA
| | | |
Collapse
|
49
|
Bancroft A, Levin ED. Ventral hippocampal alpha4beta2 nicotinic receptors and chronic nicotine effects on memory. Neuropharmacology 2000; 39:2770-8. [PMID: 11044746 DOI: 10.1016/s0028-3908(00)00099-x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chronic nicotine administration has been repeatedly shown to facilitate working memory function in rats on the radial-arm maze. The critical neural mechanisms for this effect are still being discovered. The nicotinic nature of the chronic nicotine induced memory improvement is supported by the finding that it is blocked by chronic mecamylamine co-infusion. The hippocampus also appears to be critically important. Hippocampal ibotenic acid lesions block the effect. Within the hippocampus, we have found that the alpha4beta2 nicotinic receptor subtype is involved in memory functioning. Acute ventral hippocampal infusions of the alpha4beta2 nicotinic antagonist dihydro-beta-erythroidine (DHbetaE) significantly decreased working memory performance in the radial-arm maze. The aim of the current study was to determine the importance of alpha4beta2 receptors within the ventral hippocampus for the memory enhancing effects of chronic nicotine treatment. Adult female Sprague-Dawley rats were trained on the 8-arm radial maze and were cannulated bilaterally in the ventral hippocampus. Osmotic minipumps administering chronic nicotine at a rate of 5 mg per kg per day were also implanted in the nicotine treatment rats. Control rats received saline-only minipumps. For a period of 4 weeks after surgery, each rat received bilateral hippocampal infusions of 0, 2, 6 and 18 microg per side of DHbetaE and tested for memory performance on the radial-arm maze. Radial-arm maze choice accuracy was impaired by acute hippocampal DHbetaE infusion in a dose-related fashion. This acute hippocampal DHbetaE-induced choice accuracy impairment was eliminated by chronic systemic nicotine infusion. Chronic nicotine in combination with acute vehicle hippocampal infusion was not seen to alter choice accuracy. Response latency was not found to be altered by acute hippocampal DHbetaE in the absence of chronic nicotine administration, but it did attenuate the response latency reduction induced by chronic nicotine infusion. Wet dog shakes were not found to be affected by hippocampal DHbetaE when given without chronic nicotine. Wet dog shakes were significantly increased by chronic nicotine infusion. Intra-hippocampal DHbetaE significantly potentiated this effect. The results from the current study reinforce the hypothesis that ventral hippocampal alpha4beta2 nicotinic receptors are important for memory function. These receptors may also have a role to play in the development of other aspects of behavior associated with chronic nicotine treatment.
Collapse
Affiliation(s)
- A Bancroft
- Neurobehavioral Research Laboratory, Box 3412, Department of Psychiatry, Duke University Medical Center, Durham, NC 27710, USA
| | | |
Collapse
|
50
|
McIntosh JM, Santos AD, Olivera BM. Conus peptides targeted to specific nicotinic acetylcholine receptor subtypes. Annu Rev Biochem 2000; 68:59-88. [PMID: 10872444 DOI: 10.1146/annurev.biochem.68.1.59] [Citation(s) in RCA: 252] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The venoms of predatory cone snails represent a rich combinatorial-like library of evolutionarily selected, neuropharmacologically active peptides. A major fraction of the venom components are conotoxins--small, disulfide-rich peptides that potently and specifically target components of the neuromuscular system, particularly ligand- and voltage-gated ion channels. This review focuses on Conus peptides, which act at nicotinic acetylcholine receptors. These nicotinic antagonist peptides from Conus are broadly divided into two groups: those that act at the neuromuscular junction and those that act at subtypes of neuronal nicotinic acetylcholine receptors. The latter include peptides specific for the alpha 7, alpha 3 beta 2, and alpha 3 beta 4 nicotinic receptor subtypes. The degree of specificity exhibited by these peptides is remarkable, particularly given their relatively small size. As a group the nicotinic acetylcholine receptor-targeted Conus peptides represent an increasingly well-defined set of tools for probing the structure, function, and physiological role of nicotinic acetylcholine receptors.
Collapse
Affiliation(s)
- J M McIntosh
- Department of Biology, University of Utah, Salt Lake City 84112-0840, USA.
| | | | | |
Collapse
|