1
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Fiorotti HB, Figueiredo SG, Campos FV, Pimenta DC. Cone snail species off the Brazilian coast and their venoms: a review and update. J Venom Anim Toxins Incl Trop Dis 2023; 29:e20220052. [PMID: 36756364 PMCID: PMC9897318 DOI: 10.1590/1678-9199-jvatitd-2022-0052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 12/14/2022] [Indexed: 01/31/2023] Open
Abstract
The genus Conus includes over 900 species of marine invertebrates known as cone snails, whose venoms are among the most powerful described so far. This potency is mainly due to the concerted action of hundreds of small bioactive peptides named conopeptides, which target different ion channels and membrane receptors and thus interfere with crucial physiological processes. By swiftly harpooning and injecting their prey and predators with such deadly cocktails, the slow-moving cone snails guarantee their survival in the harsh, competitive marine environment. Each cone snail species produces a unique venom, as the mature sequences of conopeptides from the venoms of different species share very little identity. This biochemical diversity, added to the numerous species and conopeptides contained in their venoms, results in an immense biotechnological and therapeutic potential, still largely unexplored. That is especially true regarding the bioprospection of the venoms of cone snail species found off the Brazilian coast - a region widely known for its biodiversity. Of the 31 species described in this region so far, only four - Conus cancellatus, Conus regius, Conus villepinii, and Conus ermineus - have had their venoms partially characterized, and, although many bioactive molecules have been identified, only a few have been actually isolated and studied. In addition to providing an overview on all the cone snail species found off the Brazilian coast to date, this review compiles the information on the structural and pharmacological features of conopeptides and other molecules identified in the venoms of the four aforementioned species, paving the way for future studies.
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Affiliation(s)
- Helena B. Fiorotti
- Laboratory of Biochemistry and Biophysics, Butantan Institute, São
Paulo, SP, Brazil.,Graduate Program in Biochemistry, Laboratory of Protein Chemistry
(LQP), Federal University of Espírito Santo, Vitória, ES, Brazil
| | - Suely G. Figueiredo
- Graduate Program in Biochemistry, Laboratory of Protein Chemistry
(LQP), Federal University of Espírito Santo, Vitória, ES, Brazil
| | - Fabiana V. Campos
- Laboratory of Biochemistry and Biophysics, Butantan Institute, São
Paulo, SP, Brazil.,Graduate Program in Biochemistry, Laboratory of Protein Chemistry
(LQP), Federal University of Espírito Santo, Vitória, ES, Brazil
| | - Daniel C. Pimenta
- Laboratory of Biochemistry and Biophysics, Butantan Institute, São
Paulo, SP, Brazil.,Correspondence:
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2
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Conus regius-Derived Conotoxins: Novel Therapeutic Opportunities from a Marine Organism. Mar Drugs 2022; 20:md20120773. [PMID: 36547920 PMCID: PMC9783627 DOI: 10.3390/md20120773] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 12/03/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022] Open
Abstract
Conus regius is a marine venomous mollusk of the Conus genus that captures its prey by injecting a rich cocktail of bioactive disulfide bond rich peptides called conotoxins. These peptides selectively target a broad range of ion channels, membrane receptors, transporters, and enzymes, making them valuable pharmacological tools and potential drug leads. C. regius-derived conotoxins are particularly attractive due to their marked potency and selectivity against specific nicotinic acetylcholine receptor subtypes, whose signalling is involved in pain, cognitive disorders, drug addiction, and cancer. However, the species-specific differences in sensitivity and the low stability and bioavailability of these conotoxins limit their clinical development as novel therapeutic agents for these disorders. Here, we give an overview of the main pharmacological features of the C. regius-derived conotoxins described so far, focusing on the molecular mechanisms underlying their potential therapeutic effects. Additionally, we describe adoptable chemical engineering solutions to improve their pharmacological properties for future potential clinical translation.
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3
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Synthesis and evaluation of disulfide-rich cyclic α-conotoxin [S9A]TxID analogues as novel α3β4 nAChR antagonists. Bioorg Chem 2021; 112:104875. [PMID: 33823404 DOI: 10.1016/j.bioorg.2021.104875] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 03/25/2021] [Accepted: 03/25/2021] [Indexed: 12/30/2022]
Abstract
Head-to-tail cyclization is an effective strategy to improve the biological stability of peptides. The α-conotoxin [S9A]TxID is a peptide that inhibits α3β4 nAChR with high activity and selectivity. Herein, we established a method for cyclizing and oxidative folding of [S9A]TxID, and six cyclic analogues of [S9A]TxID were chemically synthesized with various linker lengths. We used the electrophysiology assay to measure activity values of these cyclic analogues, and obtained the most potent analogue c[S9A]TxID-6, which was more stable than native [S9A]TxID against proteinase K.
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4
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Kennedy AC, Belgi A, Husselbee BW, Spanswick D, Norton RS, Robinson AJ. α-Conotoxin Peptidomimetics: Probing the Minimal Binding Motif for Effective Analgesia. Toxins (Basel) 2020; 12:E505. [PMID: 32781580 PMCID: PMC7472027 DOI: 10.3390/toxins12080505] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 07/29/2020] [Accepted: 08/03/2020] [Indexed: 12/18/2022] Open
Abstract
Several analgesic α-conotoxins have been isolated from marine cone snails. Structural modification of native peptides has provided potent and selective analogues for two of its known biological targets-nicotinic acetylcholine and γ-aminobutyric acid (GABA) G protein-coupled (GABAB) receptors. Both of these molecular targets are implicated in pain pathways. Despite their small size, an incomplete understanding of the structure-activity relationship of α-conotoxins at each of these targets has hampered the development of therapeutic leads. This review scrutinises the N-terminal domain of the α-conotoxin family of peptides, a region defined by an invariant disulfide bridge, a turn-inducing proline residue and multiple polar sidechain residues, and focusses on structural features that provide analgesia through inhibition of high-voltage-activated Ca2+ channels. Elucidating the bioactive conformation of this region of these peptides may hold the key to discovering potent drugs for the unmet management of debilitating chronic pain associated with a wide range of medical conditions.
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Affiliation(s)
- Adam C. Kennedy
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| | - Alessia Belgi
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| | - Benjamin W. Husselbee
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
| | - David Spanswick
- Biomedicine Discovery Institute and the Department of Physiology, Monash University, Victoria 3800, Australia;
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
- NeuroSolutions Ltd., Coventry CV4 7AL, UK
| | - Raymond S. Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Science, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia;
- ARC Centre for Fragment-Based Design, Monash University, Parkville, Victoria 3052, Australia
| | - Andrea J. Robinson
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia; (A.C.K.); (A.B.); (B.W.H.)
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5
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Muttenthaler M, Nevin ST, Inserra M, Lewis RJ, Adams DJ, Alewood P. On-resin strategy to label α-conotoxins: Cy5-RgIA, a potent α9α10 nicotinic acetylcholine receptor imaging probe. Aust J Chem 2019; 73:327-333. [PMID: 32394983 PMCID: PMC7212043 DOI: 10.1071/ch19456] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
In-solution conjugation is the most commonly used strategy to label peptides and proteins with fluorophores. However, lack of site-specific control and high costs of fluorophores are recognised limitations of this approach. Here, we established facile access to grams of Cy5-COOH via a two-step synthetic route, demonstrated that Cy5 is stable to HF treatment and therefore compatible with Boc-SPPS, and coupled Cy5 to the N-terminus of α-conotoxin RgIA while still attached to the resin. Folding of the two-disulfide containing Cy5-RgIA benefitted from the hydrophobic nature of Cy5 resulting in only the globular disulfide bond isomer. In contrast, wild-type α-RgIA folded into the inactive ribbon and bioactive globular isomer under the same conditions. Labelled α-RgIA retained its ability to inhibit acetylcholine(100 μM)-evoked current reversibly with an IC50 of 5.0 nM (Hill coefficient = 1.7) for α-RgIA and an IC50 of 1.6 (Hill coefficient = 1.2) for Cy5-RgIA at the α9α10 nicotinic acetylcholine receptors (nAChRs) heterologeously expressed in Xenopus oocytes. Cy5-RgIA was then used to successfully visualise nAChRs in RAW264.7 mouse macrophage cell line. This work introduced not only a new and valuable nAChR probe, but also a new versatile synthetic strategy that facilitates production of milligram to gram quantities of fluorophore-labelled peptides at low cost, which is often required for in vivo experiments. The strategy is compatible with Boc- and Fmoc-chemistry, allows for site-specific labelling of free amines anywhere in the peptide sequence, and can also be used for the introduction of Cy3/Cy5 FRET pairs.
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Affiliation(s)
- Markus Muttenthaler
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
- Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Simon T Nevin
- Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia
| | - Marco Inserra
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Richard J Lewis
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
| | - Paul Alewood
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
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6
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Zouridakis M, Papakyriakou A, Ivanov IA, Kasheverov IE, Tsetlin V, Tzartos S, Giastas P. Crystal Structure of the Monomeric Extracellular Domain of α9 Nicotinic Receptor Subunit in Complex With α-Conotoxin RgIA: Molecular Dynamics Insights Into RgIA Binding to α9α10 Nicotinic Receptors. Front Pharmacol 2019; 10:474. [PMID: 31118896 PMCID: PMC6504684 DOI: 10.3389/fphar.2019.00474] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 04/15/2019] [Indexed: 12/20/2022] Open
Abstract
The α9 subunit of nicotinic acetylcholine receptors (nAChRs) exists mainly in heteropentameric assemblies with α10. Accumulating data indicate the presence of three different binding sites in α9α10 nAChRs: the α9(+)/α9(−), the α9(+)/α10(−), and the α10(+)/α9(−). The major role of the principal (+) side of the extracellular domain (ECD) of α9 subunit in binding of the antagonists methyllylcaconitine and α-bungarotoxin was shown previously by the crystal structures of the monomeric α9-ECD with these molecules. Here we present the 2.26-Å resolution crystal structure of α9-ECD in complex with α-conotoxin (α-Ctx) RgIA, a potential drug for chronic pain, the first structure reported for a complex between an nAChR domain and an α-Ctx. Superposition of this structure with those of other α-Ctxs bound to the homologous pentameric acetylcholine binding proteins revealed significant similarities in the orientation of bound conotoxins, despite the monomeric state of the α9-ECD. In addition, ligand-binding studies calculated a binding affinity of RgIA to the α9-ECD at the low micromolar range. Given the high identity between α9 and α10 ECDs, particularly at their (+) sides, the presented structure was used as template for molecular dynamics simulations of the ECDs of the human α9α10 nAChR in pentameric assemblies. Our results support a favorable binding of RgIA at α9(+)/α9(−) or α10(+)/α9(−) rather than the α9(+)/α10(−) interface, in accordance with previous mutational and functional data.
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Affiliation(s)
- Marios Zouridakis
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
| | | | - Igor A Ivanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Igor E Kasheverov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Moscow, Russia
| | - Victor Tsetlin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,PhysBio of MEPhI, Moscow, Russia
| | - Socrates Tzartos
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece.,Department of Pharmacy, University of Patras, Patras, Greece
| | - Petros Giastas
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
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7
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Ren J, Zhu X, Xu P, Li R, Fu Y, Dong S, Zhangsun D, Wu Y, Luo S. d-Amino Acid Substitution of α-Conotoxin RgIA Identifies its Critical Residues and Improves the Enzymatic Stability. Mar Drugs 2019; 17:md17030142. [PMID: 30823399 PMCID: PMC6472032 DOI: 10.3390/md17030142] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 02/17/2019] [Accepted: 02/22/2019] [Indexed: 12/22/2022] Open
Abstract
α-Conotoxin RgIA is a selective and potent competitive antagonist of rat α9α10 nicotinic acetylcholine receptors (nAChR), but it is much less potent towards human α9α10 nAChR. Furthermore, RgIA is susceptible to proteolytic degradation due to containing four arginine residues. These disadvantages greatly limit its use for clinical applications. The purpose of this research was to identify critical stereocenters of RgIA and discover more stable analogues, enhancing its bioavailability by using the d-amino acid scan method. The activity of each variant was investigated against rat and human α9α10 nAChRs, which were expressed in Xenopus oocytes. Experimental assays showed that 14 out of 15 analogues had a substantial reduction in potency towards rat α9α10 nAChR. Noticeably, analogue 13 retained full biological activity compared with RgIA. Meanwhile, two other analogues, 14 and 15, of which l-Args were substituted with d-Args, exhibited a significantly increased potency towards human α9α10 nAChR, although these analogues showed decreased activities against rat α9α10 nAChR. Additionally, these three analogues exhibited a high resistance against enzymatic degradation in human serum and simulated intestinal fluid (SIF). Collectively, our findings suggest that a d-amino acid scan is a useful strategy for investigating how the side-chain chirality of amino acids affects the structure and function of peptides and may facilitate the development of more stable analogues to increase therapeutic potential.
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Affiliation(s)
- Jie Ren
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Xiaopeng Zhu
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Pan Xu
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Rui Li
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Ying Fu
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Shuai Dong
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Dongting Zhangsun
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Yong Wu
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
| | - Sulan Luo
- Key Laboratory of Tropical Biological Resources, Ministry of Education, Key Lab for Marine Drugs of Haikou, Hainan University, Haikou 570228, China.
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8
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Kryukova EV, Ivanov IA, Lebedev DS, Spirova EN, Egorova NS, Zouridakis M, Kasheverov IE, Tzartos SJ, Tsetlin VI. Orthosteric and/or Allosteric Binding of α-Conotoxins to Nicotinic Acetylcholine Receptors and Their Models. Mar Drugs 2018; 16:md16120460. [PMID: 30469507 PMCID: PMC6315749 DOI: 10.3390/md16120460] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 11/09/2018] [Accepted: 11/20/2018] [Indexed: 12/19/2022] Open
Abstract
α-Conotoxins from Conus snails are capable of distinguishing muscle and neuronal nicotinic acetylcholine receptors (nAChRs). α-Conotoxin RgIA and αO-conotoxin GeXIVA, blocking neuronal α9α10 nAChR, are potential analgesics. Typically, α-conotoxins bind to the orthosteric sites for agonists/competitive antagonists, but αO-conotoxin GeXIVA was proposed to attach allosterically, judging by electrophysiological experiments on α9α10 nAChR. We decided to verify this conclusion by radioligand analysis in competition with α-bungarotoxin (αBgt) on the ligand-binding domain of the nAChR α9 subunit (α9 LBD), where, from the X-ray analysis, αBgt binds at the orthosteric site. A competition with αBgt was registered for GeXIVA and RgIA, IC50 values being in the micromolar range. However, high nonspecific binding of conotoxins (detected with their radioiodinated derivatives) to His6-resin attaching α9 LBD did not allow us to accurately measure IC50s. However, IC50s were measured for binding to Aplysia californica AChBP: the RgIA globular isomer, known to be active against α9α10 nAChR, was more efficient than the ribbon one, whereas all three GeXIVA isomers had similar potencies at low µM. Thus, radioligand analysis indicated that both conotoxins can attach to the orthosteric sites in these nAChR models, which should be taken into account in the design of analgesics on the basis of these conotoxins.
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Affiliation(s)
- Elena V Kryukova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Igor A Ivanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Dmitry S Lebedev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Ekaterina N Spirova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Natalia S Egorova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Marios Zouridakis
- Department of Neurobiology, Hellenic Pasteur Institute, 127, Vas. Sofias ave., Athens 115 21, Greece.
| | - Igor E Kasheverov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
- Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Trubetskaya Street 8, bld. 2, 119991 Moscow, Russia.
| | - Socrates J Tzartos
- Department of Neurobiology, Hellenic Pasteur Institute, 127, Vas. Sofias ave., Athens 115 21, Greece.
| | - Victor I Tsetlin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
- PhysBio of MEPhI, Kashirskoye Ave., 31, 115409 Moscow, Russia.
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9
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Prashanth JR, Dutertre S, Jin AH, Lavergne V, Hamilton B, Cardoso FC, Griffin J, Venter DJ, Alewood PF, Lewis RJ. The role of defensive ecological interactions in the evolution of conotoxins. Mol Ecol 2016; 25:598-615. [PMID: 26614983 DOI: 10.1111/mec.13504] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 11/23/2015] [Accepted: 11/24/2015] [Indexed: 10/22/2022]
Abstract
Venoms comprise of complex mixtures of peptides evolved for predation and defensive purposes. Remarkably, some carnivorous cone snails can inject two distinct venoms in response to predatory or defensive stimuli, providing a unique opportunity to study separately how different ecological pressures contribute to toxin diversification. Here, we report the extraordinary defensive strategy of the Rhizoconus subgenus of cone snails. The defensive venom from this worm-hunting subgenus is unusually simple, almost exclusively composed of αD-conotoxins instead of the ubiquitous αA-conotoxins found in the more complex defensive venom of mollusc- and fish-hunting cone snails. A similarly compartmentalized venom gland as those observed in the other dietary groups facilitates the deployment of this defensive venom. Transcriptomic analysis of a Conus vexillum venom gland revealed the αD-conotoxins as the major transcripts, with lower amounts of 15 known and four new conotoxin superfamilies also detected with likely roles in prey capture. Our phylogenetic and molecular evolution analysis of the αD-conotoxins from five subgenera of cone snails suggests they evolved episodically as part of a defensive strategy in the Rhizoconus subgenus. Thus, our results demonstrate an important role for defence in the evolution of conotoxins.
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Affiliation(s)
- J R Prashanth
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - S Dutertre
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia.,Institut des Biomolécules Max Mousseron, UMR 5247, Université Montpellier-CNRS, Place Eugène Bataillon, 34095, Montpellier Cedex 5, France
| | - A H Jin
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - V Lavergne
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - B Hamilton
- Pathology, Mater Health Services, Raymond Terrace, South Brisbane, Qld, 4101, Australia.,Mater Research Institute, The University of Queensland, St. Lucia, Qld, 4072, Australia
| | - F C Cardoso
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - J Griffin
- ACRF Microscopy Facility, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - D J Venter
- Pathology, Mater Health Services, Raymond Terrace, South Brisbane, Qld, 4101, Australia.,Mater Research Institute, The University of Queensland, St. Lucia, Qld, 4072, Australia.,School of Medicine, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - P F Alewood
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
| | - R J Lewis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld, 4072, Australia
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10
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Muttenthaler M, Albericio F, Dawson PE. Methods, setup and safe handling for anhydrous hydrogen fluoride cleavage in Boc solid-phase peptide synthesis. Nat Protoc 2015; 10:1067-83. [PMID: 26086408 DOI: 10.1038/nprot.2015.061] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Solid-phase peptide synthesis (SPPS) using tert-butyloxycarbonyl (Boc)/benzyl (Bzl) chemistry is an indispensable technique in many laboratories around the globe, and it provides peptides to the pharmaceutical industry and to thousands of scientists working in basic research. The Boc/Bzl strategy has several advantages, including reliability in the synthesis of long and difficult polypeptides, alternative orthogonality regarding protecting groups and ease of producing C-terminal thioesters for native chemical ligation applications. In this process, anhydrous hydrogen fluoride (HF) is used to remove the side chain protecting groups of the assembled peptide and to release the peptide from the resin, a process typically described as 'HF cleavage'. This protocol describes the general methodology, apparatus setup and safe handling of HF, with the aim of providing comprehensive information on the safe use of this valuable, well-studied and validated cleavage technique. We explain the cleavage mechanism, the physicochemical properties and risks of HF, first aid measures and the correct use of the apparatus. In addition, we provide advice on scavenger selection, as well as a troubleshooting section and video material illustrating key steps of the procedure. The protocol comprises precleavage sample preparation (30 min-2.5 h), complete HF cleavage procedure (2 h) and reaction workup (30 min).
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Affiliation(s)
- Markus Muttenthaler
- 1] Institute for Research in Biomedicine Barcelona, Barcelona, Spain. [2] Department of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
| | - Fernando Albericio
- 1] Institute for Research in Biomedicine Barcelona, Barcelona, Spain. [2] The Biomedical Research Networking center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona Science Park, Barcelona, Spain. [3] Department of Organic Chemistry, University of Barcelona, Barcelona, Spain. [4] School of Chemistry, Yachay Tech, Yachay City of Knowledge, Urcuqui, Ecuador
| | - Philip E Dawson
- The Scripps Research Institute, Department of Chemistry, La Jolla, California, USA
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11
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Chhabra S, Belgi A, Bartels P, van Lierop BJ, Robinson SD, Kompella SN, Hung A, Callaghan BP, Adams DJ, Robinson AJ, Norton RS. Dicarba analogues of α-conotoxin RgIA. Structure, stability, and activity at potential pain targets. J Med Chem 2014; 57:9933-44. [PMID: 25393758 DOI: 10.1021/jm501126u] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
α-Conotoxin RgIA is both an antagonist of the α9α10 nicotinic acetylcholine receptor (nAChR) subtype and an inhibitor of high-voltage-activated N-type calcium channel currents. RgIA has therapeutic potential for the treatment of pain, but reduction of the disulfide bond framework under physiological conditions represents a potential liability for clinical applications. We synthesized four RgIA analogues that replaced native disulfide pairs with nonreducible dicarba bridges. Solution structures were determined by NMR, activity assessed against biological targets, and stability evaluated in human serum. [3,12]-Dicarba analogues retained inhibition of ACh-evoked currents at α9α10 nAChRs but not N-type calcium channel currents, whereas [2,8]-dicarba analogues displayed the opposite pattern of selectivity. The [2,8]-dicarba RgIA analogues were effective in HEK293 cells stably expressing human Cav2.2 channels and transfected with human GABAB receptors. The analogues also exhibited improved serum stability over the native peptide. These selectively acting dicarba analogues may represent mechanistic probes to explore analgesia-related biological receptors.
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Affiliation(s)
- Sandeep Chhabra
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia
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12
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Huynh TG, Cuny H, Slesinger PA, Adams DJ. Novel Mechanism of Voltage-Gated N-type (Cav2.2) Calcium Channel Inhibition Revealed through α-Conotoxin Vc1.1 Activation of the GABAB Receptor. Mol Pharmacol 2014; 87:240-50. [DOI: 10.1124/mol.114.096156] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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Akondi KB, Muttenthaler M, Dutertre S, Kaas Q, Craik DJ, Lewis RJ, Alewood PF. Discovery, synthesis, and structure-activity relationships of conotoxins. Chem Rev 2014; 114:5815-47. [PMID: 24720541 PMCID: PMC7610532 DOI: 10.1021/cr400401e] [Citation(s) in RCA: 232] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | | | - Sébastien Dutertre
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072, Australia
| | - Quentin Kaas
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072, Australia
| | - David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072, Australia
| | - Richard J Lewis
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072, Australia
| | - Paul F Alewood
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072, Australia
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Optimal cleavage and oxidative folding of α-conotoxin TxIB as a therapeutic candidate peptide. Mar Drugs 2013; 11:3537-53. [PMID: 24048271 PMCID: PMC3806463 DOI: 10.3390/md11093537] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 08/16/2013] [Accepted: 08/19/2013] [Indexed: 12/19/2022] Open
Abstract
Alpha6beta2 nicotinic acetylcholine receptors (nAChRs) are potential therapeutic targets for the treatment of several neuropsychiatric diseases, including addiction and Parkinson’s disease. Alpha-conotoxin (α-CTx) TxIB is a uniquely selective ligand, which blocks α6/α3β2β3 nAChRs only, but does not block the other subtypes. Therefore, α-CTx TxIB is a valuable therapeutic candidate peptide. Synthesizing enough α-CTx TxIB with high yield production is required for conducting wide-range testing of its potential medicinal applications. The current study optimized the cleavage of synthesized α-CTx TxIB resin-bounded peptide and folding of the cleaved linear peptide. Key parameters influencing cleavage and oxidative folding of α-CTx TxIB were examined, such as buffer, redox agents, pH, salt, co-solvent and temperature. Twelve conditions were used for cleavage optimization. Fifty-four kinds of one-step oxidative solution were used to assess their effects on each α-CTx TxIB isomers’ yield. The result indicated that co-solvent choices were particularly important. Completely oxidative folding of globular isomer was achieved when the NH4HCO3 or Tris-HCl folding buffer at 4 °C contained 40% of co-solvent DMSO, and GSH:GSSG (2:1) or GSH only with pH 8~8.7.
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α -RgIB: A Novel Antagonist Peptide of Neuronal Acetylcholine Receptor Isolated from Conus regius Venom. INTERNATIONAL JOURNAL OF PEPTIDES 2013; 2013:543028. [PMID: 23533449 PMCID: PMC3600190 DOI: 10.1155/2013/543028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 01/16/2013] [Accepted: 01/16/2013] [Indexed: 11/18/2022]
Abstract
Conus venoms are rich sources of biologically active peptides that act specifically on ionic channels and metabotropic receptors present at the neuromuscular junction, efficiently paralyzing the prey. Each species of Conus may have 50 to 200 uncharacterized bioactive peptides with pharmacological interest. Conus regius is a vermivorous species that inhabits Northeastern Brazilian tropical waters. In this work, we characterized one peptide with activity on neuronal acetylcholine receptor (nAChR). Crude venom was purified by reverse-phase HPLC and selected fractions were screened and sequenced by mass spectrometry, MALDI-ToF, and ESI-Q-ToF, respectively. A new peptide was identified, bearing two disulfide bridges. The novel 2,701 Da peptide belongs to the cysteine framework I, corresponding to the cysteine pattern CC-C-C. The biological activity of the purified peptide was tested by intracranial injection in mice, and it was observed that high concentrations induced hyperactivity in the animals, whereas lower doses caused breathing difficulty. The activity of this peptide was assayed in patch-clamp experiments, on nAChR-rich cells, in whole-cell configuration. The peptide blocked slow rise-time neuronal receptors, probably α3β4 and/or α3β4α5 subtype. According to the nomenclature, the new peptide was designated as α-RgIB.
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Azam L, McIntosh JM. Molecular basis for the differential sensitivity of rat and human α9α10 nAChRs to α-conotoxin RgIA. J Neurochem 2012; 122:1137-44. [PMID: 22774872 DOI: 10.1111/j.1471-4159.2012.07867.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The α9α10 nicotinic acetylcholine receptor (nAChR) may be a potential target in pathophysiology of the auditory system, chronic pain, and breast and lung cancers. Alpha-conotoxins, from the predatory marine snail Conus, are potent nicotinic antagonists, some of which are selective for the α9α10 nAChR. Here, we report a two order of magnitude species difference in the potency of α-conotoxin RgIA for the rat versus human α9α10 nAChR. We investigated the molecular mechanism of this difference. Heterologous expression of the rat α9 with the human α10 subunit in Xenopus oocytes resulted in a receptor that was blocked by RgIA with potency similar to that of the rat α9α10 nAChR. Conversely, expression of the human α9 with that of the rat α10 subunit resulted in a receptor that was blocked by RgIA with potency approaching that of the human α9α10 receptor. Systematic substitution of residues found in the human α9 subunit into the homologous position in the rat α9 subunit revealed that a single point mutation, Thr56 to Ile56, primarily accounts for this species difference. Remarkably, although the α9 nAChR subunit has previously been reported to provide the principal (+) binding face for binding of RgIA, Thr56 is located in the (-) complementary binding face.
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Affiliation(s)
- Layla Azam
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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17
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Cuny H, de Faoite A, Huynh TG, Yasuda T, Berecki G, Adams DJ. γ-Aminobutyric acid type B (GABAB) receptor expression is needed for inhibition of N-type (Cav2.2) calcium channels by analgesic α-conotoxins. J Biol Chem 2012; 287:23948-57. [PMID: 22613715 DOI: 10.1074/jbc.m112.342998] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
α-Conotoxins Vc1.1 and RgIA are small peptides isolated from the venom of marine cone snails. They have effective anti-nociceptive actions in rat models of neuropathic pain. Pharmacological studies in rodent dorsal root ganglion (DRG) show their analgesic effect is mediated by inhibition of N-type (Ca(v)2.2) calcium channels via a pathway involving γ-aminobutyric acid type B (GABA(B)) receptor. However, there is no direct demonstration that functional GABA(B) receptors are needed for inhibition of the Ca(v)2.2 channel by analgesic α-conotoxins. This study examined the effect of the GABA(B) agonist baclofen and α-conotoxins Vc1.1 and RgIA on calcium channel currents after transient knockdown of the GABA(B) receptor using RNA interference. Isolated rat DRG neurons were transfected with small interfering RNAs (siRNA) targeting GABA(B) subunits R1 and R2. Efficient knockdown of GABA(B) receptor expression at mRNA and protein levels was confirmed by quantitative real time PCR (qRT-PCR) and immunocytochemical analysis, respectively. Whole-cell patch clamp recordings conducted 2-4 days after transfection showed that inhibition of N-type calcium channels in response to baclofen, Vc1.1 and RgIA was significantly reduced in GABA(B) receptor knockdown DRG neurons. In contrast, neurons transfected with a scrambled nontargeting siRNA were indistinguishable from untransfected neurons. In the HEK 293 cell heterologous expression system, Vc1.1 and RgIA inhibition of Ca(v)2.2 channels needed functional expression of both human GABA(B) receptor subunits. Together, these results confirm that GABA(B) receptors must be activated for the modulation of N-type (Ca(v)2.2) calcium channels by analgesic α-conotoxins Vc1.1 and RgIA.
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Affiliation(s)
- Hartmut Cuny
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia
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18
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Halai R, Callaghan B, Daly NL, Clark RJ, Adams DJ, Craik DJ. Effects of Cyclization on Stability, Structure, and Activity of α-Conotoxin RgIA at the α9α10 Nicotinic Acetylcholine Receptor and GABAB Receptor. J Med Chem 2011; 54:6984-92. [DOI: 10.1021/jm201060r] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Brid Callaghan
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia
| | | | | | - David J. Adams
- Health Innovations Research Institute, RMIT University, Melbourne, Victoria 3083, Australia
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19
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Peng C, Chen W, Sanders T, Chew G, Liu J, Hawrot E, Chi C. Chemical synthesis and characterization of two α4/7-conotoxins. Acta Biochim Biophys Sin (Shanghai) 2010; 42:745-53. [PMID: 20801929 DOI: 10.1093/abbs/gmq074] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
α-Conotoxins are small disulfide-constrained peptides that act as potent and selective antagonists on specific subtypes of nicotinic acetylcholine receptors (nAChRs). We previously cloned two α-conotoxins, Mr1.1 from the molluscivorous Conus marmoreus and Lp1.4 from the vermivorous Conus leopardus. Both of them have the typical 4/7-type framework of the subfamily of α-conotoxins that act on neuronal nAChRs. In this work, we chemically synthesized these two toxins and characterized their functional properties. The synthetic Mr1.1 could primarily inhibit acetylcholine (ACh)-evoked currents reversibly in the oocyte-expressed rat α7 nAChR, whereas Lp1.4 was an unexpected specific blocker of the mouse fetal muscle α1β1γδ receptor. Although their inhibition affinities were relatively low, their unique receptor recognition profiles make them valuable tools for toxin-receptor interaction studies. Mr1.1 could also suppress the inflammatory response to pain in vivo, suggesting that it should be further investigated with respect to its molecular role in analgesia and its mechanism or therapeutic target for the treatment of pain.
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Affiliation(s)
- Can Peng
- Institute of Protein Research, Tongji University, Shanghai, China
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20
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McIntosh JM, Absalom N, Chebib M, Elgoyhen AB, Vincler M. Alpha9 nicotinic acetylcholine receptors and the treatment of pain. Biochem Pharmacol 2009; 78:693-702. [PMID: 19477168 PMCID: PMC2739401 DOI: 10.1016/j.bcp.2009.05.020] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 01/16/2023]
Abstract
Chronic pain is a vexing worldwide problem that causes substantial disability and consumes significant medical resources. Although there are numerous analgesic medications, these work through a small set of molecular mechanisms. Even when these medications are used in combination, substantial amounts of pain often remain. It is therefore highly desirable to develop treatments that work through distinct mechanisms of action. While agonists of nicotinic acetylcholine receptors (nAChRs) have been intensively studied, new data suggest a role for selective antagonists of nAChRs. alpha-Conotoxins are small peptides used offensively by carnivorous marine snails known as Conus. A subset of these peptides known as alpha-conotoxins RgIA and Vc1.1 produces both acute and long lasting analgesia. In addition, these peptides appear to accelerate the recovery of function after nerve injury, possibly through immune mediated mechanisms. Pharmacological analysis indicates that RgIA and Vc1.1 are selective antagonists of alpha9alpha10 nAChRs. A recent study also reported that these alpha9alpha10 antagonists are also potent GABA-B agonists. In the current study, we were unable to detect RgIA or Vc1.1 binding to or action on cloned GABA-B receptors expressed in HEK cells or Xenopus oocytes. We review the background, findings and implications of use of compounds that act on alpha9* nAChRs.(1).
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Affiliation(s)
- J Michael McIntosh
- Department of Psychiatry, University of Utah, Salt Lake City, UT 84132, USA.
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21
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Nicotinic receptors: allosteric transitions and therapeutic targets in the nervous system. Nat Rev Drug Discov 2009; 8:733-50. [PMID: 19721446 DOI: 10.1038/nrd2927] [Citation(s) in RCA: 521] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nicotinic receptors - a family of ligand-gated ion channels that mediate the effects of the neurotransmitter acetylcholine - are among the most well understood allosteric membrane proteins from a structural and functional perspective. There is also considerable interest in modulating nicotinic receptors to treat nervous-system disorders such as Alzheimer's disease, schizophrenia, depression, attention deficit hyperactivity disorder and tobacco addiction. This article describes both recent advances in our understanding of the assembly, activity and conformational transitions of nicotinic receptors, as well as developments in the therapeutic application of nicotinic receptor ligands, with the aim of aiding novel drug discovery by bridging the gap between these two rapidly developing fields.
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22
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Kasheverov IE, Zhmak MN, Fish A, Rucktooa P, Khruschov AY, Osipov AV, Ziganshin RH, D'hoedt D, Bertrand D, Sixma TK, Smit AB, Tsetlin VI. Interaction of alpha-conotoxin ImII and its analogs with nicotinic receptors and acetylcholine-binding proteins: additional binding sites on Torpedo receptor. J Neurochem 2009; 111:934-44. [PMID: 19712060 DOI: 10.1111/j.1471-4159.2009.06359.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
alpha-Conotoxins interact with nicotinic acetylcholine receptors (nAChRs) and acetylcholine-binding proteins (AChBPs) at the sites for agonists/competitive antagonists. alpha-Conotoxins blocking muscle-type or alpha7 nAChRs compete with alpha-bungarotoxin. However, alpha-conotoxin ImII, a close homolog of the alpha7 nAChR-targeting alpha-conotoxin ImI, blocked alpha7 and muscle nAChRs without displacing alpha-bungarotoxin (Ellison et al. 2003, 2004), suggesting binding at a different site. We synthesized alpha-conotoxin ImII, its ribbon isomer (ImIIiso), 'mutant' ImII(W10Y) and found similar potencies in blocking human alpha7 and muscle nAChRs in Xenopus oocytes. Both isomers displaced [(125)I]-alpha-bungarotoxin from human alpha7 nAChRs in the cell line GH(4)C(1) (IC(50) 17 and 23 microM, respectively) and from Lymnaea stagnalis and Aplysia californica AChBPs (IC(50) 2.0-9.0 microM). According to SPR measurements, both isomers bound to immobilized AChBPs and competed with AChBP for immobilized alpha-bungarotoxin (K(d) and IC(50) 2.5-8.2 microM). On Torpedo nAChR, alpha-conotoxin [(125)I]-ImII(W10Y) revealed specific binding (K(d) 1.5-6.1 microM) and could be displaced by alpha-conotoxin ImII, ImIIiso and ImII(W10Y) with IC(50) 2.7, 2.2 and 3.1 microM, respectively. As alpha-cobratoxin and alpha-conotoxin ImI displaced [(125)I]-ImII(W10Y) only at higher concentrations (IC(50)> or = 90 microM), our results indicate that alpha-conotoxin ImII and its congeners have an additional binding site on Torpedo nAChR distinct from the site for agonists/competitive antagonists.
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Affiliation(s)
- Igor E Kasheverov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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Abstract
Venomous marine cone snails harbour a variety of small disulfide-rich peptides called conotoxins, which target a broad range of ion channels, membrane receptors, and transporters. More than 700 species of Conus are thought to exist, each expressing a wide array of different peptides. Within this large repertoire of toxins, individual conotoxins are able to discriminate between different subtypes and isoforms of ion channels, making them valuable pharmacological probes or leads for drug design. This review gives a brief background to the discovery of conotoxins and describes their sequences, biological activities, and applications in drug design.
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Affiliation(s)
- Reena Halai
- The University of Queensland, Institute for Molecular Bioscience, Brisbane, Queensland 4072, Australia
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Huang F, Du W. Solution structure of Hyp10Pro variant of conomarphin, a cysteine-free and d-amino-acid containing conopeptide. Toxicon 2009; 54:153-60. [DOI: 10.1016/j.toxicon.2009.03.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 03/23/2009] [Accepted: 03/24/2009] [Indexed: 10/20/2022]
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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.
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Halai R, Clark RJ, Nevin ST, Jensen JE, Adams DJ, Craik DJ. Scanning mutagenesis of alpha-conotoxin Vc1.1 reveals residues crucial for activity at the alpha9alpha10 nicotinic acetylcholine receptor. J Biol Chem 2009; 284:20275-84. [PMID: 19447885 DOI: 10.1074/jbc.m109.015339] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vc1.1 is a disulfide-rich peptide inhibitor of nicotinic acetylcholine receptors that has stimulated considerable interest in these receptors as potential therapeutic targets for the treatment of neuropathic pain. Here we present an extensive series of mutational studies in which all residues except the conserved cysteines were mutated separately to Ala, Asp, or Lys. The effect on acetylcholine (ACh)-evoked membrane currents at the alpha9alpha10 nicotinic acetylcholine receptor (nAChR), which has been implicated as a target in the alleviation of neuropathic pain, was then observed. The analogs were characterized by NMR spectroscopy to determine the effects of mutations on structure. The structural fold was found to be preserved in all peptides except where Pro was substituted. Electrophysiological studies showed that the key residues for functional activity are Asp(5)-Arg(7) and Asp(11)-Ile(15), because changes at these positions resulted in the loss of activity at the alpha9alpha10 nAChR. Interestingly, the S4K and N9A analogs were more potent than Vc1.1 itself. A second generation of mutants was synthesized, namely N9G, N9I, N9L, S4R, and S4K+N9A, all of which were more potent than Vc1.1 at both the rat alpha9alpha10 and the human alpha9/rat alpha10 hybrid receptor, providing a mechanistic insight into the key residues involved in eliciting the biological function of Vc1.1. The most potent analogs were also tested at the alpha3beta2, alpha3beta4, and alpha7 nAChR subtypes to determine their selectivity. All mutants tested were most selective for the alpha9alpha10 nAChR. These findings provide valuable insight into the interaction of Vc1.1 with the alpha9alpha10 nAChR subtype and will help in the further development of analogs of Vc1.1 as analgesic drugs.
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Affiliation(s)
- Reena Halai
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia
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Analgesic alpha-conotoxins Vc1.1 and Rg1A inhibit N-type calcium channels in rat sensory neurons via GABAB receptor activation. J Neurosci 2008; 28:10943-51. [PMID: 18945902 DOI: 10.1523/jneurosci.3594-08.2008] [Citation(s) in RCA: 135] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
alpha-Conotoxins Vc1.1 and Rg1A are peptides from the venom of marine Conus snails that are currently in development as a treatment for neuropathic pain. Here we report that the alpha9alpha10 nicotinic acetylcholine receptor-selective conotoxins Vc1.1 and Rg1A potently and selectively inhibit high-voltage-activated (HVA) calcium channel currents in dissociated DRG neurons in a concentration-dependent manner. The post-translationally modified peptides vc1a and [P6O]Vc1.1 were inactive, as were all other alpha-conotoxins tested. Vc1.1 inhibited the omega-conotoxin-sensitive HVA currents in DRG neurons but not those recorded from Xenopus oocytes expressing Ca(V)2.2, Ca(V)2.1, Ca(V)2.3, or Ca(V)1.2 channels. Inhibition of HVA currents by Vc1.1 was not reversed by depolarizing prepulses but was abolished by pertussis toxin (PTX), intracellular GDPbetaS, or a selective inhibitor of pp60c-src tyrosine kinase. These data indicate that Vc1.1 does not interact with N-type calcium channels directly but inhibits them via a voltage-independent mechanism involving a PTX-sensitive, G-protein-coupled receptor. Preincubation with a variety of selective receptor antagonists demonstrated that only the GABA(B) receptor antagonists, [S-(R*,R*)][-3-[[1-(3,4-dichlorophenyl)ethyl]amino]-2-hydroxy propyl]([3,4]-cyclohexylmethyl) phosphinic acid hydrochloride (2S)-3[[(1S)-1-(3,4-dichlorophenyl)-ethyl]amino-2-hydroxypropyl](phenylmethyl) phosphinic acid and phaclofen, blocked the effect of Vc1.1 and Rg1A on Ca2+ channel currents. Together, the results identify Ca(V)2.2 as a target of Vc1.1 and Rg1A, potentially mediating their analgesic actions. We propose a novel mechanism by which alpha-conotoxins Vc1.1 and Rg1A modulate native N-type (Ca(V)2.2) Ca2+ channel currents, namely acting as agonists via G-protein-coupled GABA(B) receptors.
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28
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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.
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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
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