28 December, 2004
Elan Receives FDA Approval for PRIALT (Ziconotide Intrathecal Infusion) for Severe Chronic Pain
PRIALT(R) [other names: Ziconotide, SNX-111, omega-Conotoxin MVIIA] was approved today by the Federal Drug Administration, FDA, for the management of severe chronic pain:
- Novel Non-Narcotic Treatment Based on Marine Snail Peptide Blocks Pain Signals
- PRIALT(R) is Approved for use only in the Medtronic SynchroMed(R) EL, SynchroMed(R) II Infusion System and Simms Deltec Cadd Micro(R) External Microinfusion Device and Catheter
- Approval Based on Results From Three Pivotal Trials
Dec. 28, 2004--Elan Corporation, plc (NYSE:ELN): Elan Corporation, plc today announced that the U.S. Food and Drug Administration (FDA) has approved PRIALT(R) (ziconotide intrathecal infusion) for the management of severe chronic pain in patients for whom intrathecal (IT) therapy is warranted, and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies or IT morphine. FDA approval of PRIALT was based on the treatment of more than 1,200 patients and three Phase III clinical trials, which evaluated the efficacy and safety of IT PRIALT in patients with severe chronic pain that was not adequately managed despite a regimen of systemic and/or IT analgesic and other drugs.
- For further details of this long-awaited and important announcemement read the Press Release from Elan Corp.
- A brief summary of the information is available from the Doctors Guide
- Detailed Product Information about PRIALT(R) is also available.
- Information about PRIALT, including prescribing information and comprehensive support services, is available through a toll-free number, 1-888-PRIALT-1, and at www.PRIALT.com.
23 December, 2004
Seven new species of Conus described in VISAYA II
VISAYA II
In this second issue of Visaya: E. L. Heiman, Felix Lorenz, Manuel J. Tenorio & Carlos M. L. Afonso, Gabriella Raybaudi Massilia, Eva Pip and Guido T. Poppe contributed with 6 articles containing descriptions of several new species.
- Lorenz, F. (2004). "Two New Species of CONIDAE from Southern Madagascar". pp.19-23.
- Tenorio, M.J. and Alfonso, C.M. (2004). "Description of Four New Species of Conus from the Cape Verde Islands". pp. 24-37.
- Raybaudi Massilia, G. (2004). "An 'Old' New Species of Conus from the Philippines". pp. 38-41.
Other articles are: "Conchological Treasures from the Philippines" and "Intraspecific Variation in mauritia arabica". Visaya is printed in color from cover to cover.
There are 7 Newly described species of Conus in this issue: Conus medoci sp. nov.; Conus chiapponorum sp. nov.; Conus vulcanus n. sp.; Conus claudiae n. sp.; Conus isabelarum n. sp.; Conus crioulus n. sp.; and Conus suduirauti n. sp.Another 3 new species Conus frausseni n. sp.; Conus grohi n. sp.; and Conus terryni n. sp. were described in the first issue of the journal, VASAYA I (see entry below for 9 August 2004).
For information about VISAYA click here.
Conus imperialis alpha-toxins ImI and ImII target separate inhibitory sites on the alpha7 nicotinic receptor
Ellison, M., Gao, F., Wang, H.L., Sine, S.M., McIntosh, J.M. and Olivera, B.M. (2004) alpha-Conotoxins ImI and ImII Target Distinct Regions of the Human alpha7 Nicotinic Acetylcholine Receptor and Distinguish Human Nicotinic Receptor Subtypes. Biochemistry. 43:16019-16026.
Departments of Biology and Psychiatry, University of Utah, Salt Lake City, Utah 84112, and Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota 55905.
Abstract: The Conus peptides alpha-conotoxin ImI (alpha-ImI) and ImII (alpha-ImII) differ by only three of 11 residues in their primary sequences and yet are shown to inhibit the human alpha7 nicotinic acetylcholine receptor (nAChR) by targeting different sites. Mutations at both faces of the classical ligand binding site of the alpha7 nAChR strongly affect antagonism by alpha-ImI but not alpha-ImII. The effects of the mutations on alpha-ImI binding and functional antagonism are explained by computational docking of the NMR structure of alpha-ImI to a homology model of the ligand binding domain of the alpha7 nAChR. A distinct binding site for alpha-ImII is further demonstrated by its weakened antagonism for a chimeric receptor in which the membrane-spanning domains and intervening linkers of the alpha7 nAChR are replaced with the corresponding sequence from the serotonin type-3 receptor (5HT(3)). The two toxins also discriminate between different subtypes of human nicotinic receptors; alpha-ImII most strongly blocks the human alpha7 and alpha1beta1deltaepsilon receptor subtypes, while alpha-ImI most potently blocks the human alpha3beta2 subtype. Collectively, the data show that while alpha-ImI targets the classical competitive ligand binding site in a subtype selective manner, alpha-ImII is a probe of a novel inhibitory site in homomeric alpha7 nAChRs.
Conotoxins from Conus magus and Conus imperialis used to distinguish different nicotinic receptor subtypes involved in dopamine release.
Cao, Y.J., Surowy, C.S., Puttfarcken, P.S. (2005) Different nicotinic acetylcholine receptor subtypes mediating striatal and prefrontal cortical [(3)H]dopamine release. Neuropharmacology. 48:72-79.
Neurological Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6125, USA.
Different nicotinic acetylcholine receptor subtypes appear to modulate dopamine release from the striatum and prefrontal cortex. In this study a combination of subtype-selective antagonists and agonists were used to extensively characterize the nAChRs involved in dopamine release from slice preparations of these two brain regions. alpha-conotoxin-MII inhibited nicotine-evoked [(3)H]dopamine (DA) release from striatum by 45%, but did not affect cortical dopamine release. Neither methyllycaconitine, alpha-bungarotoxin, nor alpha-conotoxin-ImI affected nicotine-evoked [(3)H]DA release from either striatum or prefrontal cortex. MG 624, a novel selective nAChR antagonist, inhibited cortical [(3)H]DA by 53%, but had no effect on striatal release. Compared to nicotine, (+/-)-UB-165 showed less efficacy with respect to dopamine release from striatum, and had no effect on cortical dopamine release. (+/-)-UB-165-evoked striatal dopamine release was completely blocked by mecamylamine, partially blocked (up to 55%) by alpha-conotoxin-MII, and unaffected by methyllycaconitine or alpha-conotoxin-ImI. alpha4beta2* and alpha6beta2beta3* nAChRs appear to play a role in striatal dopamine release, whereas alpha4beta2* nAChRs modulate release from prefrontal cortex. alpha7* nAChRs do not appear to play a role in nAChR-mediated dopamine release from either brain region.
21 December, 2004
Conotoxin tx5a from Conus textile: a heavily post-translationally modified glycopeptide
Kang, J., Low, W., Norberg, T., Meisenhelder, J., Hansson, K., Stenflo, J., Zhou, G.P., Imperial, J., Olivera, B.M., Rigby, A.C. and Craig, A.G. (2004) Total chemical synthesis and NMR characterization of the glycopeptide tx5a, a heavily post-translationally modified conotoxin, reveals that the glycan structure is alpha-d-Gal-(1-->3)-alpha-d-GalNAc Eur J Biochem. 271:4939-4949.
The Clayton Foundation Laboratories for Peptide Biology, The Salk Institute, La Jolla, CA, USA.
Abstract: The 13-amino acid glycopeptide tx5a (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* = 6-bromotryptophan and Thr* = Gal-GalNAc-threonine), isolated from Conus textile, causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationally modified residues: four cysteine residues, two gamma-carboxyglutamic acid residues, and one residue each of 6-bromotryptophan, 4-trans-hydroxyproline and glycosylated threonine. The chemical nature of each of these has been determined with the exception of the glycan linkage pattern on threonine and the stereochemistry of the 6-bromotryptophan residue. Previous investigations have demonstrated that tx5a contains a disaccharide composed of N-acetylgalactosamine (GalNAc) and galactose (Gal), but the interresidue linkage was not characterized. We hypothesized that tx5a contained the T-antigen, beta-d-Gal-(1-->3)-alpha-d-GalNAc, one of the most common O-linked glycan structures, identified previously in another Conus glycopeptide, contalukin-G. We therefore utilized the peracetylated form of this glycan attached to Fmoc-threonine in an attempted synthesis. While the resulting synthetic peptide (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* =6-bromotryptophan and Thr* = beta-d-Gal-(1-->3)-alpha-d-GalNAc-threonine) and the native peptide had almost identical mass spectra, a comparison of their RP-HPLC chromatograms suggested that the two forms were not identical. Two-dimensional (1)H homonuclear and (13)C-(1)H heteronuclear NMR spectroscopy of native tx5a isolated from Conus textile was then used to determine that the glycan present on tx5a indeed is not the aforementioned T-antigen, but rather alpha-d-Gal-(1-->3)-alpha-d-GalNAc.
19 December, 2004
omega-conotoxin MVIIA structure and functions
Contoxin MVIIA from Conus magus 
Other names: SNX111, Ziconotide, Prialt. from database PubChem compound. Small molecule chemical structures.
- View list of published pharmacological articles about omega-conotoxin MVIIA (SNX-111,Ziconotide, Prialt) on Toxline.
- View latest Clinical Trials of Ziconotide as listed on NIH ClinicalTrials.gov.
- 3 key articles on Conotoxin MVIIA structure and function (from TOXLINE SPECIAL).
- Mitchell, S.S., Shon, K.J., Olivera, B., Ireland, C.M. (1996) NMR structures of conotoxins. J. Natural Toxins 5: 191-208
Abstract: This review discusses the methodology, structural details, and biological implications regarding NMR structures of conotoxins. NMR and molecular modeling techniques have improved to the point that three-dimensional structures of conotoxins can now be determined with a significant degree of confidence. At the same time, biochemical techniques have made important progress in disseminating critical areas of the toxin receptors. As the two areas of research converge, they can begin to explain the extraordinary selectivity of conotoxin binding on a molecular level. An understanding of how molecular interactions between the toxins and their receptors leads to binding specificity should have broad applications in many fields. NMR structures of conotoxins have now been published for each of the major toxin classes. This review includes a brief discussion on the NMR and modeling techniques used for each of the published conotoxin structures to date.
- Norton, R.S. (1996) Structure and function of peptide and protein toxins from marine organisms. J. Toxicology Toxin Reviews 17: 99-130.
Abstract: This literature review discusses sea anemones, snakes, cone snails and other marine organisms with respect to the toxicology and biophysics of their protein toxins. It includes a discussion of analytical methods, amino acid sequence, three-dimensional structure of the peptide toxins and their related ion channel proteins, receptor binding sites, X-ray crystallography, NMR spectroscopy of alpha-conotoxins, and neurotoxins that act as sodium channel modulators and potassioum channel blockers. there is also discussion of cytolysins.
- West, D.J., Andrews, E.B., Bowman, D., McVean, A.R., Thorndyke, M.C.(1998) Toxins from some poisonous and venomous marine snails. J. Comp Biochem Physiol C. Pharmacol. Toxicol and Endocrinol. 113: 1-10.
Abstract: This literature review discusses conotoxins from Conus venom that act as calcium channel blockers.
17 December, 2004
Chinese bird spider toxin, a more potent analgesic than omega-conotoxin MVIIA
Chen, J.Q., Zhang, Y.Q., Dai, J., Luo, Z.M. and Liang, S.P. (2005) Antinociceptive effects of intrathecally administered huwentoxin-I, a selective N-type calcium channel blocker, in the formalin test in conscious rats. Toxicon. 45:15-20.
Biochemistry Department, College of Life Sciences, Hunan Normal University, Changsha, Hunan 410081, People's Republic of China.
Abstract: The present study was undertaken to elucidate the antinociceptive effect of intrathecal administration of huwentoxin-I (HWTX-I), a N-type calcium channel blocker from the venom of the Chinese bird spider Ornithoctonus huwena (Wang) [=Selenocosmia huwena wang], by comparison with omega-Conotoxin-MVIIA (omega-CTX-MVIIA) and morphine hydrochloride in the formalin test in conscious rats. Similar to omega-CTX-MVIIA and morphine, intrathecal pre-treatment with HWTX-I resulted in suppression of nociceptive behavior in a dose-dependent manner. The ED(50) values of HWTX-I and omega-CTX-MVIIA were 0.28 and 0.19mug/kg, respectively. It was also found that, at lower doses (0.1 and 0.5mug/kg), the antinociceptive effect of HWTX-I was identical to that of omega-CTX-MVIIA, while omega-CTX-MVIIA acted more remarkably than HWTX-I at higher dose (1.0mug/kg). However, the antinociception induced by omega-CTX-MVIIA were companied with motor dysfunction, and these side-effects became more evident with the doses of omega-CTX-MVIIA increasing. In contrast, HWTX-I did not show these side-effects at the doses of 0.5-1.0mug/kg. Compared with HWTX-I and omega-CTX-MVIIA, the analgesic effect of intrathecal morphine hydrochloride was initiated faster, but lasted for a shorter time (about 2-3h at 1.0mug/kg) than that of HWTX-I and omega-CTX-MVIIA (about 4-5h at 1.0mug/kg). Therefore, the present results show that, like omega-CTX-MVIIA, the intrathecal administration of HWTX-I is effective in antinociception in the rat model of the formalin test.
15 December, 2004
Conotoxins as tools for invetigating sodium channels
French, R.J. and Terlau, H. (2004) Sodium channel toxins--receptor targeting and therapeutic potential. Curr Med Chem. 11: 3053-3064.
Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, T2N 4N1, Canada. french@ucalgary.ca
Abstract: Sodium channels underlie propagated electrical signalling in most excitable cells, including neurons and the myocytes of skeletal muscle and heart. These proteins are targeted by a variety of current therapeutic drugs to combat such maladies as pain, myotonias, epilepsies and cardiac arrhythmias. Typically, these problems are associated with overactivity of sodium channels leading to hyperexcitability in the relevant tissue. More than ten distinct but closely related molecular isoforms of mammalian sodium channel are now known to be specifically expressed in different cell types and tissues. Therapeutic attenuation of sodium channel activity must be effected with great precision in both targeting and the degree of reduction in channel activity if a malfunction is to be corrected without introducing deleterious or even catastrophic side effects. Numerous natural toxins have evolved to target sodium channels, either by blocking current through the pore or by modifying channel gating. Among the well studied toxins, the peptide conotoxins from cone snail venoms show a remarkable ability to discriminate among closely related forms of sodium channel, as well as exhibiting a variety of modes of action. Here, we examine the molecular basis of action of different Na channel targeted conotoxins and explore their potential as models for the future design of more specifically targeted drugs.
9 December, 2004
Conantokins - a REVIEW
Layer RT, Wagstaff JD, White HS. (2004) Conantokins: peptide antagonists of NMDA receptors. Curr Med Chem. 11: 3073-3084.
Cognetix, Inc. 421 Wakara Way, Suite 201, Salt Lake City, UT 84108, USA. rlayer@cognetix.com
Abstract: Conantokins are small peptides (17-27 amino acids) found in the venoms of cone snails (Conus sp.) that inhibit the activity of N-methyl-D-aspartate (NMDA) receptors. Unlike most of the peptides characterized from cone snail venom that contain multiple disulfide bridges, conantokins are linear peptides that possess a high degree of alpha-helicity in the presence of divalent cations, and contain gamma-carboxyglutamic acid residues. Four naturally occurring conantokins have been identified and characterized to date, conantokin-G, conantokin-T, conantokin-R, and conantokin-L. The most extensively characterized, conantokin-G, is selective for subtypes of NMDA receptors containing the NR2B subunit. The conantokins have been synthesized and characterized in a number of animal models of human pathologies including pain, convulsive disorders, stroke, and Parkinson's disease. The potential pharmacological selectivity of the conantokins, coupled with their efficacy in preclinical models of disease and favorable safety profiles indicate that these peptides represent both novel probes for NMDA receptor function as well as an important class of compounds for continued investigation as human therapeutics.
8 December, 2004
Novel conotoxin rg11a from Conus regius
Vianna Braga, M.C., Konno, K., Portaro, F.C., Carlos de Freitas, J., Yamane, T., Olivera, B.M. and Pimenta, D.C. (2005) Mass spectrometric and high performance liquid chromatography profiling of the venom of the Brazilian vermivorous mollusk Conus regius: feeding behavior and identification of one novel conotoxin. Toxicon. 45 :113-122
Department of Physiology, Bioscience Institute, University of Sao Paulo, Sao Paulo, SP, Brazil.
Abstract: Carnivorous mollusks belonging to the genus Conus paralyze their prey by injecting a rich mixture of biologically active peptides. Conus regius is a vermivorous member of this genus that inhabits Brazilian tropical waters. Inter-, intra-species and individual variations of cone snail venom have been previously reported. In order to investigate intra-specific differences in C. regius venom, its feeding behavior and the correlation between these two factors, animals were pooled according to gender, size and season of collection, and their venom composition was compared by high performance liquid chromatography (HPLC). Both the whole venom and one specific peak were monitored by HPLC. Chromatographic profiles revealed no significant differences in their peak areas, indicating that the venom composition, based solely in the presence or absence of the major peaks, is stable regardless of season, gender and size. Therefore, analysis of one given toxin, eluting in one of the major peaks, is representative among the population. Moreover, this work presents the identification of one novel conotoxin (rg11a), which amino acid sequence was deduced by mass spectrometry.
Live Conus regius with a fire-worm (from a series by David Touitou from Martinique).
Note: the above paper by Braga and colleagues includes images showing the envenomation of a fire-worm E. complanata by the vermivorous carnivor, Conus regius. It was observed that the prey's body changed colour after venom inoculation, from reddish to purple. The authors speculate that besides paralysis, "there might be some secondary effect on the fire-worm's clotting cascade". They also note that when provided with a variety of prey (fish, marine worms, other molluscs), the cone snail extended its proboscis only towards the correct prey, the fire-worm. None of the 30 specimens of Conus regius observed extented their proboscis towards fish or molluscs. Paralysis of the fire-worms took longer than did paralysis of fish by piscivorous cones such as Conus ermineus, studied in parallel. Statistical analysis comparison of the chromatographic profiles of pooled venom from different specimens taken at different locations, of different size groups, male or female, and from different locations, did not reveal a significant pattern of variation, even though visual interpretation of the chromatographic profiles indicate some differences.
The deduced amino acid sequence of peak 54, the novel conopeptide rg11a,
CQAYGESCSAVVRCCDPNAVCCQYPEDAVCVTRGYCRPPATVLT reveals a peptide with a new characterized pattern (C-C-CC-CC-C-C-) from the I-superfamily of conotoxins. This peptide has some sequence homology to other conotoxins that are known to interact with vertebrate K+ channels. The pre-peptide sequence, cysteine bridging pattern, and functional properties are under investigation to confirm the assignment of rg11a to a superfamily. The authors comment that "without proper profiling and normalization of any possible intraspecific variation in the venom composition, one cannot state that a novel toxin is a constitutive component of the venom rather than the product of gender, season or size variation".
28 November, 2004
Coneshell update
Giancarlo Paganelli has updated his Cone Shells collection (currently more than 1175 images).
Conus araneosus HWASS in BRUGUIÈRE, 1792
Sri Lanka - 67.8 mm, with periostracum;
Conus austini REHDER & ABBOTT, 1951
Venezuela, Gulf of Venezuela, Los Monges - 52.1 mm;
Conus brunneus, WOOD, 1828
Mexico, Oaxaca, Puerto Angel - 45.6 mm ;
Conus capricorni Van Mol, Tursch & Kempf, 1967
Brazil, Vitoria, Espiritu Santo - 60.1 mm;
Conus ermineus BORN, 1778
Senegal, Gorée Is. - 67.1 mm;
Conus genuanus LINNAEUS, 1758
Gabon, Port Gentil - 54.6 mm;
Conus princeps LINNAEUS, 1758
Mexico, Oaxaca, Puerto Angel - 41.0 mm, and
Conus spurius GMELIN, 1791
Venezuela, Gulf of Venezuela, Los Monges - 50.7 mm.
27 November, 2004
Conotoxin r11a from Conus radiatus exhibits L-D amino acid isomerization
Buczek, O., Yoshikami, D., Bulaj, G., Jimenez, E.C. and Olivera, B.M. (2004) Posttranslational amino acid isomerization: A functionally important D-amino acid in an excitatory peptide. J Biol Chem.280 : 4247-4253.
Biology, University of Utah, Salt Lake City, UT 84112-0840.
Abstract: The posttranslational modification of an L- to a D-amino acid has been documented in relatively few gene products, mostly in small peptides under 10 AA in length. In this report, we demonstrate that a 46-amino-acid polypeptide toxin has one D-phenylalanine at position 44, and that the epimerization from an L-Phe to a D-Phe has a dramatic effect on the excitatory effects of the peptide. In one electrophysiological assay carried out, the D-Phe-containing peptide was extremely potent, while the unmodified polypeptide had no biological activity, demonstrating that the chirality of the posttranslationally modified amino acid is functionally significant. The peptide toxin analyzed, r11a, belongs to the I-gene superfamily of conotoxins that has four disulfide crosslinks. The D-Phe in r11a is at the third amino acid from the C-terminus, the same relative position from the C-terminal end as the D-amino acid in omega-agatoxin TK from a spider, an unrelated peptide. Thus, although posttranslational amino acid isomerization appears to have no strong specificity for the chemical nature of the amino acid side chain, the few peptides where this modification has been established suggest that there may be favored positions near the N- or C-terminus that are preferential sites for isomerization to a D-amino acid.
See also Jimenez et al (2003) J. Neurochem 85: 610-621.
23 November 2004
Conus victoriae duct venom yields over 40 novel conotoxins
Jakubowski, J.A. and Sweedler, J.V. (2004) Sequencing and mass profiling highly modified conotoxins using global reduction/alkylation followed by mass spectrometry. Anal Chem. 76: 6541-6547.
Department of Chemistry and the Beckman Institute, University of Illinois, Urbana, Illinois 61801.
Abstract: A novel high-throughput method for characterizing heavily modified peptides from cone snail venom is described. Unpurified cone snail duct venom, consisting primarily of multiply disulfide-bonded peptides, is reduced and alkylated using a global procedure in order to simultaneously reduce and derivatize dozens of disulfide-bonded peptides. Samples of Conus victoriae venom are analyzed by online liquid chromatography-electrospray ionization-ion trap-mass spectrometry (LC-ESI-MS) with collisionally induced dissociation (CID). Comparison of the mass profiles of peptides and CID spectra before and after the global reduction and alkylation enables cysteine-containing conopeptides to be ascertained. In this case, over 40 conotoxins are characterized based on only two LC-ESI-MS experiments in terms of mass, number of disulfide-linked cysteine residues (and hence, potential toxin superfamilies), relative hydrophobicity, and other posttranslational modifications. Using this technique, over half of the amino acids (by mass) of several peptides are defined prior to any detailed sequencing studies. Further comparison of the mass data with previously published genetic information allows sequence verification of three novel peptides, termed vc5b, vc6b and vc6c, based on both LC-ESI-MS CID and nanoelectrospray ionization-ion trap-mass spectrometry (nanoESI-MS) experiments. This global method is ideally suited to the use of larger genetic databases in order to efficiently sequence peptides in Conus venoms and is also applicable to analysis of other disulfide-rich classes of peptides such as defensins, chemokines, and snake, spider, or other venoms.
Conus toxins and their targets: A Review
Heading, C.E. (2004) Conus toxins: Targets and properties. IDrugs. 7: 1011-1016.
The Open University, Department of Biological Sciences, Walton Hall, Milton Keynes, MK7 6AA UK. moore11@globalnet.co.uk.
Abstract: The venoms from Conus snails are rich in peptides with potent specificity for mammalian receptor sites. Each venom typically contains up to 100 conopeptides, and with approximately 500 species of Conus snail, the number of active peptides is considerable. The receptor sites targeted appear to be mostly linked to ion channels, with voltage-gated, ligand-gated and G-protein linked sites identified. Both the central and peripheral nervous system present possible physiological targets for therapeutic products derived from the venoms, although the molecules in the most advanced development target the central nervous system. In turn, this presents problems of bioavailability, while the potency is a potential source of toxicity.
The I-superfamily of conopeptides is widespread
Kauferstein, S., Huys, I., Kuch, U., Melaun, C., Tytgat, J. and Mebs, D. (2004) Novel conopeptides of the I-superfamily occur in several clades of cone snails. Toxicon 44: 539 - 548.
Zentrum der Rechtsmedizin, University of Frankfurt, Kennedyallee 104, D-60596 Frankfurt am Main, Germany. kauferstein@em.uni-frankfurt.de
Abstract: The I-superfamily of conotoxins represents a new class of peptides in the venom of some Conus species. These toxins are characterized by four disulfide bridges and inhibit or modify ion channels of nerve cells. When testing venoms from 11 Conus species for a functional characterization, blocking activity on potassium channels (like Kv1.1 and Kv1.3 channels, but not Kv1.2 channels) was detected in the venom of Conus capitaneus, Conus miles, Conus vexillum and Conus virgo. Analysis at the cDNA level of these venoms using primers designed according to the amino acid sequence of a potassium channel blocking toxin (ViTx) from C. virgo confirmed the presence of structurally homologous peptides in these venoms. Moreover, peptides belonging to the I-superfamily, but with divergent amino acid sequences, were found in Conus striatus and Conus imperialis. In all cases, the sequences of the precursors' prepro-regions exhibited high conservation, whereas the sequences of the mature peptides ranged from almost identical to highly divergent between species. We then performed phylogenetic analyses of new and published mitochondrial 16S rDNA sequences representing 104 haplotypes from these and numerous other Conus species, using Bayesian, maximum-likelihood, maximum-parsimony and neighbor-joining methods of inference. Cone snails known to possess I-superfamily toxins were assigned to five different major clades in all of the resulting gene trees. Moreover, I-superfamily conopeptides were detected both in vermivorous and piscivorous species of Conus, thus demonstrating the widespread presence of such toxins in this speciose genus beyond evolutionary and ecological groups.
22 November, 2004
Conus peptides - a REVIEW
Wang, C.Z. and Chi, C.W. (2004) Conus peptides - a rich pharmaceutical treasure. Acta Biochim Biophys Sin (Shanghai) 36: 713-723.
Institute of Biochemistry and Cell Biology, Shanghai Institute of Biological Sciences, the Chinese Academy of Sciences, Shanghai 200031 China; Institute of Neuroscience, the Chinese Academy of Sciences, Shanghai 200031, China; Institute of Protein Research, Tongji University, Shanghai 200092, China.
Abstract Marine predatory cone snails (genus Conus) with over 500 species represent what is arguably the largest single genus of marine animals alive today. All Conus are venomous and utilize a complex mixture of Conus peptides to capture their preys and for other biological purposes. Each component of Conus peptides selectively targets a specific subtype of ion channels, neurotransmitter receptors or transporters. Owing to their diversity, more than 50,000 distinct active peptides are theoretically estimated in Conus venoms. These diversified toxins are generally categorized into several superfamilies and/or families based on their characteristic arrangements of cysteine residues and pharmacological actions. Some mechanisms underlying the remarkable diversity of Conus peptides have been postulated: the distinctive gene structure, gene duplication and/or allelic selection, genus speciation, and sophisticated expression pattern and post-translational modification of these peptides. Due to their highly pharmacological potency and target selectivity, Conus peptides have attracted extensive attention with their potentials to be developed as new research tools in neuroscience field and as novel medications in clinic for pain, epilepsy and other neuropathic disorders. Several instructive lessons for our drug development could be also learnt from these neuropharmacological "expertises". Conus peptides comprise a rich resource for neuropharmacologists, and most of them await to be explored.
Click here for the full text of this REVIEW.
18 November, 2004
Prialt (Ziconotide, SNX-111, omega-conotoxin MVIIA) given European "approval" for human use.
PRIALT -Ziconotide- Receives Positive CHMP Recommendation for Intrathecal Treatment of Severe Chronic Pain Media Announcement: Elan Corporation, plc announced that PRIALT(TM) (ziconotide) has received a positive recommendation from the European Committee for Medicinal Products for Human Use (CHMP), the human medicines scientific body of the European Medicines Agency. The CHMP has recommended that Prialt be indicated for the treatment of severe, chronic pain in patients who require intrathecal (IT) analgesia. The CHMP's positive recommendation will now be proposed for final marketing approval by the European Commission. Final approval customarily follows the CHMP's recommendation in approximately three months.
13 November, 2004
Decreased [(125)I]-alpha-Conotoxin MII binding to thalamic nuclei in dementia with impaired consciousness
Ray, M., Bohr, I., McIntosh, J.M., Ballard, C., McKeith, I., Chalon, S., Guilloteau, D., Perry, R., Perry, E., Court, J.A. and Piggott, M. (2004) Involvement of alpha6/alpha3 neuronal nicotinic acetylcholine receptors in neuropsychiatric features of Dementia with Lewy bodies: [(125)I]-alpha-conotoxin MII binding in the thalamus and striatum.Neurosci Lett. 372: 220-225.
Institute for Ageing and Health, University of Newcastle upon Tyne, MRC Building, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE, UK
Abstract: Dementia with Lewy bodies (DLB) is a neurodegenerative disease associated with a range of neuropsychiatric symptoms and reduced expression of neuronal nicotinic acetylcholine receptors (nAChRs) in neocortex, hippocampus, thalamus and basal ganglia. To determine whether there are selective associations between alterations in alpha6/alpha3 neuronal nicotinic acetylcholine receptors (nAChRs) and the two key neuropsychiatric features of DLB, impaired consciousness (IC) and visual hallucinations (VH), quantitative [(125)I]-alpha-conotoxin MII ([(125)I]-alpha-Ctx MII) autoradiography was undertaken on 28 people with DLB and 15 control cases from the Newcastle Brain Bank. There was a highly significant overall trend for reduced thalamic [(125)I]-alpha-Ctx MII binding in DLB (p<0.001), with significant deficits in the centromedian, ventral lateral and ventroposterior medial thalamic nuclei (p<0.05), together with caudate and putamen (p<0.001). [(125)I]-alpha-Ctx MII binding was significantly lower in DLB cases with IC than without IC in the putamen (p<0.05), however there was no significant association between [(125)I]-alpha-Ctx MII binding and VH. Reductions in [(125)I]-alpha-Ctx MII binding in caudate and putamen were paralleled by similar reductions in [(125)I]PE2I binding. [(125)I]PE2I binding was also significantly lower in DLB cases with IC than without IC in the caudate (p<0.05) and putamen (p<0.001). These results demonstrate that deficits in alpha6/alpha3 nAChRs occur in specific brain regions in DLB, may in part be related to the loss of dopaminergic neurons and may contribute to the development of impaired consciousness in the disorder.
Conotoxins and nicotinic ligands distinguish dopamine and noradrenaline release in the hippocampus
Cao, Y.J., Surowy, C. and Puttfarcken, P.S. (2004) Nicotinic Acetylcholine Receptor-Mediated [3H]-Dopamine Release from Hippocampus.J. Pharmacol. Exp. Ther. (in press). 2004 Nov 12; [Epub ahead of print]
Abbott Laboratories.
Abstract: The mechanism of nicotinic acetylcholine receptor (nAChR)-induced hippocampal dopamine (DA) release was investigated using rat hippocampal slices. nAChRs involved in hippocampal DA and norepinephrine (NE) release were investigated using prototypical agonists and antagonists, as well as several relatively novel compounds, ABT-594, +/-UB-165, and MG 624. +/--Epibatidine (EB), +/--UB-165, anatoxin-a, ABT-594, (-)-nicotine, 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP), and (-)-cytisine (in decreasing order of potency) evoked [(3)H]-DA release in a mecamylamine-sensitive manner. Aside from +/--UB-165, all agonists displayed full efficacy relative to 100 microM (-)-nicotine in [(3)H]-DA release. In contrast, +/--UB-165 was a partial agonist, evoking 58% of 100 microM (-)-nicotine response. Mecamylamine (Mec), MG 624, hexamethonium (Hex), d-Tubocurare (d-TC), and dihydro-beta-erythroidine (DHbetaE) (in decreasing order of potency), but not alpha-conotoxin-MII (alpha-CtxMII), methyllycaconitine (MLA), alpha-conotoxin-ImI (alpha-CtxImI) or alpha-bungarotoxin (alpha-BTX), attenuated 100 microM (-)-nicotine -evoked [(3)H]-DA release in a concentration-dependent manner. +/--UB-165, ABT-594 and MG 624 exhibited different pharmacological profiles in the [(3)H]-NE release assay when compared to their effect on [(3)H]-DA release. ABT-594 was 4.5-fold more potent, and +/--UB-165 was a full agonist, in contrast to its partial agonism in [(3)H]-DA release. MG 624 potently and completely blocked NE release evoked by 100 microM (-)-nicotine, and 10 microM +/--UB-165, whereas it only partially inhibited (-)-nicotine -evoked [(3)H]-DA release. In conclusion, we provide evidence that [(3)H]-DA can be evoked from the hippocampus, and that the pharmacological profile for nAChR-evoked hippocampal [(3)H]-DA release suggests involvement of alpha3beta4* and at least one other nAChR subtype, thus distinguishing it from that of nAChR-evoked hippocampal [(3)H]-NE release.
[See also Neuropharmacology. 48:72-79, listed above].
18 November, 2004
IUCN REDLIST of ENDANGERED SPECIES
A total of 15,589 species face extinction (including 7 Conus species), according to the 2004 IUCN Red List of Threatened Species. One in three amphibians and almost half of all freshwater turtles are threatened, on top of the one in eight birds and one in four mammals known to be in jeopardy. No new species of Conus have been added to the list since the previous listing in 1996
Conus africanus, Kiener 1845, Angola.
Conus cepasi,Trovao, 1975. Angola
Conus kohni, McLean & Nybakken, 1979, Ecuador (Galápagos).
Conus kohni
McLean & Nybakken, 1979: The Veliger 22(2):140-142, figs. 4, 24.
HOLOTYPE: LACM 1885 (shell dry, animal wet)
18-37 m, Caleta Tagus, Isla Isabela (Albemarle), Islas Galapagos (0° 24.5' S, 90° 23' W)
Leg.: Gerald Wellington, 15 JAN 1975
Conus nobrei, Trovao, 1975, Angola.
Conus zebroides, Kiener, 1845,
Angola.
13 November, 2004
Ziconotide (omega-conotoxin MVIIA): Clinical trials for refractory pain in Cancer and AIDS
Doggrell, S.A. (2004) Intrathecal ziconotide for refractory pain. Expert Opin Investig Drugs13 : 875-877.
Doggrell Biomedical Communications, 47 Caronia Crescent, Lynfield, Auckland, New Zealand. s.doggrell@xtra.co.nz
Abstract: For cancer and AIDS patients, 10-30% of pain is refractory to strong opioids, requiring intraspinal administration for pain management. Ziconotide is a selective N-type calcium channel blocker, which inhibits neurotransmitter release, and following intrathecal administration will affect primary nociceptive afferents. In 108 patients with previously unmanaged refractory pain despite the use of systemic or intrathecal opioids, in the initial titration phase, the mean Visual Analogue Scale of Pain Intensity scores improved more in the ziconotide group (53%) than the placebo group (18%). Serious adverse effects were more common in the ziconotide group (31%) than placebo group (10%) in the initial titration phase. In the 48 patients receiving Ziconotide, who proceeded to the maintenance phase, the benefit of Ziconotide was continued. Until a new approach with a better effectiveness/adverse effects profile than ziconotide for refractory pain emerges, further optimisation of Ziconotide for use in the treatment of refractory pain should be undertaken.
7 November, 2004
Cone shells in the Read Shell Collection 1845-1928
For a glimpse into the past at an impressive shell collection, take a look at The Victorian Shell Collection 1845-1928 of Ella and Clara Read.
Drawer 34
Drawer 35
Drawer 36
The Read Family Shell Collection: Evolution of A Passion
History (Extract): "What began as a simple gift of seashells was to evolve into an intricately organized collection of some 30,000 sea, land and freshwater shells gathered from all parts of the globe, including all coastlines of the U.S. (including Hawaii, Alaska, Puerto Rico), Mexico and South America, the Mediterranean, East and South Africa, Australia, New Zealand, Indonesia, and many islands along the Pacific Rim. Each shell, preserved in it’s original state, was individually labled and catalogued according to its family, Latin classification, place of origin preserved in its original state. The shells were then stored in small spool-and-thread boxes manufactured by Joseph Reades textile mill, which were then organized into fifty-two 16’’x24’’ mahogany drawers.Having remained completely in tact for over a century, The Read Family Shell Collection provides a rare view of the intersection of natural history and human history as seen through the fascinated eyes of two Victorian women". (Prints are available - Click here. For cone shells select Drawers 34, 35 and 36)
3 November, 2004
alpha-conotoxin BuIA from Conus bullatus distinguishes beta2- from beta4-containing nAChRs
Azam, L., Dowell, C., Watkins, M., Stitzel, J.A., Olivera, B.M., McIntosh, J.M. (2004) alpha-conotoxin BuIA, a novel peptide from Conus bullatus distinguishes among neuronal nicotinic acetylcholine receptors. J Biol Chem. 2004 Nov 1 [Epub ahead of print]
Departments of Psychiatry and Biology, University of Utah, Salt Lake City, UT 84112.
alpha 4/4 BuIA GCCSTPPCAVLYC*
Conus bullatus (from which the sequence of BuIA, a 13 amino acid amidated alpha-conopeptide, was obtained)
Abstract: Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. alpha subunits, together with beta2 and/or beta4 subunits, form ligand-binding sites at alpha/beta subunit interfaces. Predatory marine snails of the genus Conus are a rich source of nAChR-targeted peptides. Using conserved features of the alpha-conotoxin signal sequence and 3' untranslated sequence region, we have cloned a novel gene from the fish-eating snail, Conus bullatus; the gene codes for a previously unreported alpha-conotoxin with unusual 4/4 spacing of amino acids in the two disulfide loops. Chemical synthesis of the predicted mature toxin was performed. The resulting peptide, alpha-conotoxin BuIA, was tested on cloned nAChRs expressed in Xenopus oocytes. The peptide potently blocks numerous rat nAChR subtypes, with highest potency for alpha3- and chimeric alpha6-containing nAChRs; BuIA blocks alpha6/alpha3beta2 nAChRs with a 40,000-fold lower IC50 than alpha4beta2 nAChRs. The kinetics of toxin unblock are dependent on the beta subunit. nAChRs with a beta4 subunit have very slow off-times, compared to the corresponding beta2 subunit-containing nAChR. In each instance, rat alphaxbeta4 may be distinguished from rat alphaxbeta2 by the large difference in time to recover from toxin block. Similar results are obtained when comparing mouse alpha3beta2 to mouse alpha3beta4, and human alpha3beta2 to human alpha3beta4, indicating that the beta subunit dependence extends across species. Thus, alpha-conotoxin BuIA also represents a novel probe for distinguishing between beta2- and beta4-containing nAChRs.
30 October, 2004
Farming Killer Cone Snails a Risky Affair
Associated Press Writer ALICIA CHANG has penned a feature article about Jon-Paul Bingham's cone shell milking of venoms. The article syndicated worldwide is accesible here.
Extract: POTSDAM, N.Y. (AP) Oct 30, 10:02 PM EDT -- Jon-Paul Bingham puts his life on the line every week for the sake of science. One wrong move, and he could become the hapless victim of a snail attack that could kill him. Bingham, a biochemist at Clarkson University, is a self-described "conehead" whose livelihood depends on scuba diving for tropical marine cone snails and coaxing them to discharge their venom in his laboratory.
"It's like snake-charming," he said with a grin.......
26 October, 2004
Conus catus envnomates a fish ( + video)
Schulz, J.R., Norton,A.G. and Gilly, W.F. (2004). The projectile tooth of a fish-hunting cone snail: Conus catus injects venom into fish prey using a high-speed ballistic mechanism. Biol. Bull. 207:77-79
Abstract: The sequence of stills in this video illustrates the mechanism of prey-capture by a fish-hunting cone snail (Conus catus). The action is taking place in a chamber 1.2 mm high. The cone snail's proboscis approaches from the left, and the fish is positioned at the right side of the chamber. The times before (-ms) and after (+ms) the release of the snail's harpoon-shaped radular tooth are indicated in the upper left corner of the video frame. In the final few milliseconds before the radular tooth is released (-7 to -3 ms), the base of the tooth is propelled up against a constriction within the proboscis. The first frame after the release of the tooth occurs at 0 ms. The movie ends (at +200 ms) with the cone snail's proboscis holding the base of the radular tooth, which is impaling the fish. The video was constructed of stills from a high-speed video clip (1000 frames/s); the clip is available from the corresponding author (Email: jschulz@oxy.edu).
VIDEO (Requires Quicktime)
ARTICLE
Fastest Gun in the Sea Science Now, Daily News, 19 October, 2004
Fish-hunting cone snail uses unique mechanism to capture prey.
by David Grim
"One of the sea's slowest creatures may also be its fastest hunter. A new study reveals that the fish-hunting cone snail immobilizes passing fish by firing a harpoonlike tooth at them. The entire process--from detecting the prey to stunning it--takes less than 300 milliseconds, making it one of the quickest captures known. Quick draw. The fish-hunting cone snail fires a harpoon-shaped tooth from its proboscis (inset) to capture prey". [CREDIT: JOSEPH SCHULZ]
"Scientists have long been interested in the deadly toxins cone snails use to paralyze their prey, exploiting them for neuroscience research and drug development. But little was known about how the snails get this venom into their victims and how they stop fish dead in their tracks. To address these questions, a team of researchers from Stanford University's Hopkins Marine Station in Pacific Grove, California, constructed a setup that would give them a view to a kill. They attached a fish and an underwater high-speed video camera to one end of a small acrylic trough. When a Conus catus snail at the opposite end of the trough sensed the fish, it guided its translucent proboscis down the trough's furrow until it touched the fish. Then, in less than a third of a second, the camera recorded the proboscis constricting, launching a hollow harpoon-shaped tooth into the fish, and injecting venom through the tooth into the fish. The base of the tooth is gripped by the proboscis during the entire event--so it never actually leaves the snail's body--and is used as a hook to draw the fish in, the team reports in the October issue of The Biological Bulletin 207:77-79.".
"The incredible speed of this ballistic method of prey capture explains how these snails can capture such fast prey, says lead researcher Joseph Schulz, now at Occidental College in Los Angeles. He notes that it is still unclear how the constriction of the proboscis readies the tooth for launch, but he believes it may somehow build up pressure at the base of the tooth."
" 'This is a really good piece of work,' says Jon-Paul Bingham, a biochemist and cone snail farmer at Clarkson University in Potsdam, New York. The trick used by the fish-hunting cone snail is "extremely unique" in the animal kingdom, he says, and may have evolved to allow these creatures to expand their diet."
The original article in Biological Bulletin by Schulz, and colleagues was commented upon above by -- DAVID GRIMM in Science Magazine, 22 October 2004, Vol. 306 No. 5696.
Related sites: (Video of cone snail shooting its prey; Study collaborator William Gilly's site; Further information on cone snails)
See also: Article by Jeff Hecht "Venomous snails with lightning strikes", in NewScientist.com news service, 15 October 2004.
25 October, 2004
Conchological Iconography (Part10). Conidae
Monteiro, A., Tenorio, M. J. & Poppe, G. T. (2004) The genus Conus of West Africa and the Mediterranean (with a foreword by Dieter Röckel and a contribution on the radulae by E. Rolan). - 2+102 pp., 10 numbered and 108 unnumbered text-figs, 98 maps, 4 b/w + 164 col. pls., loose-leaf 4to [US$136]
Description: That 10th part of the Conchological Iconography is the first devoted to the vast family of Conidae. The West-Ethiopian and Mediterranean Provinces house nearly 100 (excactly 99) species and subspecies of which most are endemic to very restricted areas, mainly in the Cape Verde Islands (48), Angola (25) and Senegal & Guinea (12). Also the Conus-fauna of the Madeiras, Canaries and St. Helena is included in that part. One new species to science is described . The text gives a short history of the scientific approach to the fauna, but also shows nice collectibles from West African countries. The 4 pages with the Systematic List are followed by 62 pages of a commented Taxa List which gives detailed descriptions of animal and shell and information on synonymy, distribution (with detailed map) habitat and biology. The description of each species is attached to a figure showing a typical specimen in ventral and dorsal view. 11 pages focus the interest on the radulae of West African cones and a Selected Bibliography of nearly 100 titles is followed by an Alphabetical Index.
The perfect colour-figures show roughly 1,300 shells, so covering all the high variability of the fauna. Five plates illustrate live animals and their habitats, the last four plates exhibit a very useful determination tool.
A further part on the South-Ethiopian Province is in preparation by the same author-team.
22 October, 2004
Biosynthesis of conotoxins: Role of propeptide and protein disulfide isomerase
Buczek, O., Goodsell, I., Garrett, J., Buczek, P., Olivera, B.M. and Bulaj, G. (2004) Role of Propeptide and Protein Disulfide Isomerase in the Oxidative Folding of Conotoxins. Poster.
Abstract: Conotoxins are a diverse set of peptide neurotoxins from Conus snail venoms, most of which contain multiple disulfide bonds. These peptides are initially translated as precursors, consisting of an N-terminal signal sequence, an intervening propeptide region and the C-terminal mature conotoxin. Formation of the native disulfide bonds during the oxidative folding of conotoxins is prerequisite to proper biological function, but numerous in vitro folding experiments with mature conotoxins have suggested a lack of specificity in the formation of native Cys-Cys connectivities. To explore the function of propeptide sequence in the maturation of conotoxins, we studied the oxidative folding of two conotoxin precursors, namely pro-GI and pro-PVIA, belonging to alpha- and delta-conotoxin families, respectively. The results indicate that the propeptide sequence does not strongly affect folding kinetics and thermodynamics. However, when oxidative folding is catalyzed by protein disulfide isomerase (PDI), the early steps in the folding of precursor were more efficient compared to the mature conotoxin alone. In addition, we present the cloning and recombinant expression of the Conus PDI, a major protein component of the venom duct from Conus textile. Taken together, our data are suggestive that the propeptide and protein disulfide isomerase may play an important role in the biosynthesis of conotoxins.
REVIEW: Nicotinic ligands for the treatment of pain
In this article the potential of nicotinic receptor ligands in the treatment of pain is discussed focussing on the perceived advantages and disadvantages of non-selective and subtype-selective agonists, peripherally acting agonists and, more speculatively, whether a disease-specific approach or nicotinic modulators or antagonists (including alpha-conotoxins such as AuI, MII, PIA and Vc1.1) might offer possibilities for treatment of pain.
Rueter, L.E., Decker, M.W. and Bitner, R.S. (2004)Improving the therapeutic window in the treatment of pain with nicotinic ligands. Drug Discovery Today: Therapeutic Strategies - Pain and anethesia. 1:(1),89-96.
Abbott Laboratories, Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Park, IL, USA.
Abstract: ALthough the analgesic properties of nicotine have been known for many years, the pharmaceutical exploration of nicotinic acetylcholine recetpors (nAChR) ligands for the treatment of pain has really only developed during the past 10 years. In that time, it has become apparent that the greates hurdle in the development of nAChR ligands is the therapeutic window, specifically separating analgesia from nAChR-mediated adverse effects on the gastrointestinal, cardiovascular, respiratory and central nervous systems. We discuss here five strategies designed to improve the therapeutic window. The grewatest chances for the successful development of a nAChR analgesic will probably be through combinations of these strategies, such as selective recetpor subunit agonist developed for a specific type of pain.
See also:
Decker, M.W., Rueter, L.E. and Bitner, R.S. (2004) Nicotinic acetylcholine receptor agonists: a potential new class of analgesics. Curr Top Med Chem. 4:369-84. Review.
Abstract: Current analgesics, such as opioids and nonsteroidal anti-inflammatory drugs (NSAIDs), are largely refinements of approaches available for more than 100 years and have critical liabilities and limitations. A number of new molecular targets for analgesia have been proposed in recent years, including the neuronal nicotinic acetylcholine receptor (nAChR). Agonists at neuronal nAChRs have antinociceptive effects in a variety of preclinical pain models. Moreover, nicotine can decrease experimentally-induced pain in humans without disrupting normal tactile sensation. These data from both experimental animals and humans suggest that compounds targeting neuronal nAChRs may represent a new class of analgesic agents. In this paper, we provide brief overviews of the physiology of pain, the animal models used to assess potential analgesics preclinically, and the biology of nAChRs. We then provide a review of preclinical data on the antinociceptive effects of a variety of neuronal nAChR agonists and a discussion of potential mechanisms, including evidence that antinociception is mediated by activation of brainstem nuclei with descending inhibitory inputs to the spinal cord. An evaluation of the clinical potential of this approach must also consider potential side effects. Undesirable side effects of nicotine are well known, but as we will discuss in detail, these effects are not produced by all neuronal nAChR agonists and the existence of neuronal nAChR subtypes may provide a basis for separating therapeutic effects from toxicities.
Bunelle, W.H. and Decker,, M.W. (2003) Neuronal nicotinic acetylcholine receptors ligands as potential analgesics. Expert Opin. Ther. Patents 13: 1003-1021.
13 October, 2004
Assembly of conantokins
Dai, Q., Castellino, F.J., Prorok, M. (2004) A single amino acid replacement results in the Ca2+-induced self-assembly of a helical conantokin-based peptide. Biochemistry 43:13225-13232.
Department of Chemistry and Biochemistry and the W. M. Keck Center for Transgene Research, University of Notre Dame, Notre Dame, Indiana 46556.
Abstract: Conantokins are short (17-27 amino acid residues), gamma-carboxyglutamate (Gla)-rich peptide components of the venoms of marine snails of the genus Conus. They display high apo and/or Ca2+-induced helicity and act as potent and selective inhibitors of the N-methyl-d-aspartate receptor (NMDAR). We have previously established that one of the conantokins, conantokin-G (con-G), self-associates in the presence of Ca2+ with high specificity for antiparallel chain orientation [Dai, Q., Prorok, M., and Castellino, F. J. (2004) J. Mol. Biol. 336, 731-744]. The dimerization appears to be driven by interhelical Ca2+ coordination between the following residue pairings: Gla(3)-Gla(14)('), Gla(7)-Gla(10)('), Gla(10)-Gla(7)('), and Gla(14)-Gla(3)('). A second member of the conantokin family, conantokin-T (con-T), shares sequence identity with con-G at 8 of 21 amino acids, including 4 Gla residues. These similarities notwithstanding, several primary and secondary structural differences exist between con-T and con-G. Particularly notable is that con-T contains a Lys, rather than a Gla, at position 7. Moreover, unlike con-G, con-T does not undergo Ca+ -triggered self-assembly. In the present study, sedimentation equilibrium ultracentrifugation is employed to demonstrate that a single amino acid replacement analogue of con-T, con-T[K7gamma], assumes a dimeric superstructure in the presence of Ca2+ at pH values consistent with the ionization of Gla carboxylate groups. Furthermore, HPLC-monitored thiol-disulfide folding and rearrangement assays with Cys-containing con-T variants suggest that the relative chain alignment preference in the noncovalent complex is antiparallel. Our results suggest that interchain Ca+ coordination in con-T[K7gamma] is incumbent upon an "i, i + 4, i +7, i +11" arrangement of Gla residues, as occurs in native con-G.
Conus pappiliferus live - a small Australian cone shell.
7 October, 2004
w-Conotoxin GVIA reveals N-type calcium channels in dorsal horn of spinal cord
Murakami, M., Nakagawasai, O., Suzuki, T., Mobarakeh, II., Sakurada, Y., Murata, A., Yamadera, F., Miyoshi, I., Yanai, K., Tan-No, K., Sasano, H., Tadano, T. and Iijima, T. (2004) Antinociceptive effect of different types of calcium channel inhibitors and the distribution of various calcium channel alpha(1) subunits in the dorsal horn of spinal cord in mice. Brain Res.1024:122-129.
Department of Pharmacology, Akita University School of Medicine, 1-1-1 Hondoh, Akita 010-8543, Japan.
Abstract: To understand better which voltage-dependent calcium channels (VGCCs) are involved in nociceptive neurotransmission, we investigated the pharmacological properties and distribution of VGCCs in the mouse spinal cord. A behavioral assay revealed that intrathecal injections of omega-agatoxin TK, omega-agatoxin IVA, omega-conotoxin GVIA, and SNX-482, which block P/Q-, P/Q-, N-, and R-type calcium channels, respectively, produced analgesic effects, while an L-type channel blocker had no such effect. An electrophysiological study demonstrated the presence of various types of VGCCs within dorsal root ganglion (DRG) neurons. Immunohistochemistry revealed distinct localization of P/Q-, N-, L-, and R-type calcium channel subunits to the dorsal horn of the spinal cord. The results of this study revealed the localization and functions of several calcium channels that are involved in nociceptive neurotransmission within the dorsal horn of the mouse spinal cord.
25 September, 2004
'Light sleeper' peptide from Conus radiatus
Olivera and colleagues have isolated a novel
“light sleeper peptide”, conotoxin r7a, from Conus radiatus venom.
WFGHÊÊCTYWLGPCÊVDDTCCSASCÊSKFCGLW^
(W = 6-bromotryptophan; Ê = gamma-carboxyglutamate; ^ = C-terminal free acid)
This is the third peptide from Conus radiatus venom that induces a sleep-like state. This highly posttranslationally modified peptide is distinctly different from two other sleeper peptides characterized previously from this venom:
Jimenez, E.C., Watkins, M. and Olivera, B.M. (2004) Multiple 6-bromotryptophan residues in a sleep-inducing peptide. Biochemistry 43: 12343-12348.
Departments of Biology and Pathology, University of Utah, Salt Lake City, Utah 84112, and Department of Physical Sciences, College of Science, University of the Philippines Baguio, Baguio City, Philippines.
Abstract: We have characterized a novel sleep-inducing peptide comprising 33 amino acids with three residues of the unusual posttranslationally modified amino acid, 6-bromotryptophan. The peptide, termed "light sleeper" or the r7a conotoxin, was purified from the venom of the fish-hunting Conus radiatus. The light sleeper peptide has additional notable biochemical properties; it equilibrates slowly between two distinct conformers, and has four gamma-carboxyglutamate residues. The pattern of posttranslational bromination in the light sleeper peptide suggests that tryptophan residues at N- and C-termini may be preferential sites for posttranslational bromination.
15 September, 2004
Review: Conus peptides - and video clip of envenomation
Cruz, LJ and Jimenez, EC (2004) Conus venom neuropeptides Encyclopedia of Neuroscience 3rd Edition, Edited by George Adelman and Barry H. Smith, CD-ROM,p.291 ISBN: 0444514325, Elsevier, BV.
Includes video clip showing envenomation of a small fish by a piscivorous cone shell.
Conus textile envenomating a marine snail
In issue #32 of Marine Life, Guido Poppe and Philippe Poppe have a nice photo of a Conus textile in the act of envenomating a small snail on Cabilao Island in the Philippines.
10 September, 2004
{alpha}5 Subunit of nicotinic receptor contributes to native alpha6*-nAChR-like pharmacology with high affinity for alpha-conotoxin MII
Grinevich, V.P., Letchworth, S.R., Lendenberger, K.A., Menager, J., Mary, V., Sadieva, K.A., Buhlman, L., Bohme, G.A., Pradier, L., Benavides, J., Lukas, R.J. and Bencherif, M. (2004) Heterologous Expression of Human {alpha}6{beta}4{beta}3{alpha}5 Nicotinic Acetylcholine Receptors: Binding Properties Consistent with Their Natural Expression Require Quaternary Subunit Assembly Including the {alpha}5 Subunit. J Pharmacol Exp Ther. 2004 Sep 8 [Epub ahead of print]
Division of Neurobiology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, Arizona 85013, USA. rlukas@chw.edu
Abstract: Heterologous expression and lesioning studies were conducted to identify possible subunit assembly partners for nicotinic acetylcholine receptors (nAChR) containing alpha6 subunits (alpha6*-nAChR). SH-EP1 human epithelial cells were transfected with the requisite subunits to achieve stable expression of human alpha6beta2-, alpha6beta4-, alpha6beta2beta3-, alpha6beta4beta3-, or alpha6beta4beta3alpha5-nAChR. Cells expressing subunits needed to form alpha6beta4beta3alpha5-nAChR exhibited saturable [(3)H]-epibatidine binding (Kd = 95.9 +/- 8.3 pM and Bmax = 84.5 +/- 1.6 fmol/mg protein). The rank order of binding competition potency (Ki) for prototypical nicotinic compounds was alpha-conotoxin MII (6 nM) > nicotine (156 nM) approximately methyllycaconitine (200 nM) > alpha-bungarotoxin (>10 mM), similar to that for nAChR in dopamine neurons displaying a distinctive pharmacology. 6-Hydroxydopamine lesioning studies indicated that beta3 and alpha5 subunits are likely partners of the alpha6 subunits in nAChR expressed in dopaminergic cell bodies. Similar to findings in rodents, quantitative real-time RT-PCR of human brain indicated that alpha6 subunit mRNA expression was 13-fold higher in the substantia nigra than in the cortex or the rest of the brain. Thus, the human alpha5 subunit makes a critical contribution to alpha6beta4beta3alpha5-nAChR assembly into a ligand-binding form with native alpha6*-nAChR-like pharmacology and of potential physiological and pathophysiological relevance.
3 September, 2004
Different sensitivity of two classes of DRG neurons to contoxin GVIA
In this study, Drs Wu and Pan found that block of N-type Ca2+ channels with omega-conotoxin GVIA produced a significantly greater reduction of Ca+ currents in IB(4)-positive than in the smaller IB(4)-negative DRG neurons. They also suggest that IB(4)-positive neurons have a higher density of N-type calcium channels than the smaller IB(4)-negative DRG neurons.These differences may contribute to the different function of these two classes of nociceptive neurons.
Wu, Z.Z. and Pan, H.L. (2004). High voltage-activated Ca+ channel currents in isolectin B(4)-positive and -negative small dorsal root ganglion neurons of rats. Neurosci Lett. 368: 96-101.
Department of Anesthesiology, The Pennsylvania State University College of Medicine, The Milton S. Hershey Medical Center, Hershey, PA 17033, USA.
Abstract: Voltage-gated Ca+ channels in the primary sensory neurons are important for neurotransmitter release and regulation of nociceptive transmission. Although multiple classes of Ca channels are expressed in the dorsal root ganglion (DRG) neurons, little is known about the difference in the specific channel subtypes among the different types of DRG neurons. In this study, we determined the possible difference in high voltage-activated Ca+ channel currents between isolectin B(4) (IB(4))-positive and IB(4)-negative small-sized (15-30microm) DRG neurons. Rat DRG neurons were acutely isolated and labeled with IB(4) conjugated to a fluorescent dye. Whole-cell patch clamp recordings of barium currents flowing through calcium channels were performed on neurons with and without IB(4). The peak current density of voltage-gated Ca2+ currents was not significantly different between IB(4)-positive and IB(4)-negative neurons. Also, both nimodipine and omega-agatoxin IVA produced similar inhibitory effects on Ca2+ currents in these two types of neurons. However, block of N-type Ca+ channels with omega-conotoxin GVIA produced a significantly greater reduction of 2Ca2+currents in IB(4)-positive than IB(4)-negative neurons. Furthermore, the IB(4)-positive neurons had a significantly smaller residual Ca2+ currents than IB(4)-negative neurons. These data suggest that a higher density of N-type Ca2+ channels is present in IB(4)-positive than IB(4)-negative small-sized DRG neurons. This differential expression of the subtypes of high voltage-activated Ca+ channels may contribute to the different function of these two classes of nociceptive neurons.
29 August, 2004
MOLLUSK - a Conotoxin sequence database
MOLLUSK is an integrated database of conotoxin sequence information, focusing on the molecular components of conotoxin sequences. MOLLUSK is meant to provide a unique source of information, data retrieval and analysis tools on conotoxin sequences. All records are fully referenced.
MOLLUSK facilitates:
- Keyword search - enables search for entries from the entire database using keywords, ion channel, superfamily and family
- Alignments - contains alignments of protein sequences and superfamilies
- BLAST Mollusk - a query amino acid or nucleotide sequence can be compared against all known sequences available in the database using BLAST.
- Download FASTA - enables the downloading of fasta-formatted files of amino acids and nucleotide sequences.
- Annotate Mollusk - analyse and generates putative functional annotation for the query sequence
- Mollusk Structures - display 3-D structures of conotoxin from PDB and the homology models of toxins whose structures have not been solved as yet.
(Source: The Institute for Infocomm Research (I²R), Singapore. The Institute for Infocomm Research (I²R) integrates R&D in communications and information technology to develop holistic solutions across the ICT value chain. The Institute's research capabilities are in wireless and optical communications, and information technology and science. I²R seeks to enable technologies and processes that will drive new and enhanced services for Singapore's knowledge-based economy. Dr. Vladimir Brusic and Dr. Rekha Pillai, coordinators, last updated this database on October 10, 2003).
27 August, 2004
The Shell Collector: A tale of a blind professor who collects cones
THE SHELL COLLECTOR by Anthony Doerr, Paperback: 224 pages ; Dimensions (in inches): 0.59 x 7.94 x 5.10 Publisher: Penguin Books; Reissue edition (February 1, 2003) ISBN: 0142002968
The Shell Collector, Anthony Doerr's first collection of stories, ranges from Liberia and Tanzania to Montana and Maine. This short story collection was named winner of bookseller Barnes and Noble's 10th Annual "Discover Great New Writers Awards" in the fiction category on March 5, 2003. The Shell Collector is Doerr's first work of fiction, and it is the first short-story collection to receive the Discover Award (Doerr received a cash prize of $10,000 and a full year of additional marketing and advertising support). Traversing the vast terrain of the world, Doerr shows an extraordinary empathy in stories that most often concern themselves with the interaction between humans and nature. In the title story he applies his empathy to a retired professor ("The Shell Collector"), a lyrical and somber tale constructed of achingly beautiful, precise language. Synopsis: The shell collector is a blind former professor who at age 63 is attempting a retreat from the human world by retiring to the coast of Tanzania to live out his days wading in a quiet lagoon and collecting shells with fingers that seem to see. His world is simple and empirical: "Ignorance was, in the end, and in so many ways, a privilege: to find a shell, to feel it, to understand only on some unspeakable level why it bothered to be so lovely. What joy he found in that, what utter mystery." Yet the world intrudes on the shell collector, asking him to be a father, a guide, and a savior; reluctantly, and with devastating and then surprisingly hopeful consequences, he is drawn in. Doerr's greatest gift is to see an equal humanity in people belonging to all ages, cultures, and countries. "Doerr's proze dazzles, his sinewy sentences blending the naturalist's unswerving gaze with the poet's gift for metaphore." - New York Times Book Review. Stories include a winner of the O. Henry Award and two finalists for the National Magazine Award.
Dextral or Sinistral ?
Wandelt, J. and Nagy, L.M. (2004) Left-right asymmetry: more than one way to coil a shell. Curr Biol. 14: R654-656.
Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA.
Abstract:Snail shells can be left-handed or right-handed, sometimes within one species. For over a century, it has commonly been assumed that mirror-image shell coiling in snails is correlated with a mirror- image reversal of early spindle orientation and cleavage. The results of an exciting and elegant new study refute this model, showing that right doesn't have to be the mirror image of left.
26 August, 2004
Synthesis of cis-Pro isomer analogs of delta-Conotoxin EVIA from Conus erminius
Chierici, S., Jourdan, M., Figuet, M. and Dumy, P. (2004) A case study of 2,2-dimethylthiazolidine as locked cis proline amide bond: synthesis, NMR and molecular modeling studies of a [small delta]-conotoxin EVIA peptide analog. Org Biomol Chem. 2: 2437-2441. Epub 2004 Aug 05.
LEDSS UMR 5616 & ICMG-FR2607, Universite Joseph Fourier, BP 53, 38041, Grenoble cedex 9, France. pascal.dumy@ujf-grenoble.fr
Abstract:The delta-conotoxin EVIA from the Conus ermineus venom, a recently characterized toxin, exhibits cis-trans isomerism of the Leu(12)-Pro(13) bond associated with the triggering of its biological activity. In this paper we use the pseudoproline concept to target the presumed bioactive cis conformation. We report the design and the synthesis of loop 2 analogs from residue 8 to 18 containing either the cis-inducing Cys(Psi(Me,Me)Pro)(13) unit or the natural proline residue. NMR studies in water and molecular modeling allowed us to identify the amide bond "locked" in a cis conformation for as in the suggested bioactive form of the natural toxin.
24 August, 2004
Conotoxin-receptor interactions aid drug discovery
Grant, M.A., Morelli, X.J. and Rigby, A.C. (2004) Conotoxins and structural biology: a prospective paradigm for drug discovery. Curr Protein Pept Sci. 5: 235-248.
Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, 41 Avenue Louis Pasteur, Boston, MA 02115, USA. arigby@bidmc.harvard.edu
Abstract: Understanding the interactions between activating or antagonizing ligands and their cognate receptors at a molecular level offers promise for the development of pharmacological therapeutics for CNS disorders. The discovery of novel molecules that are capable of discriminating between the varied molecular subunits or isoforms of ion channels should provide a more detailed understanding of the pathophysiology of many CNS disorders. Abundant natural sources of pharmacologically active agents that demonstrate this refined selectivity and specificity are found in the animal toxins of venomous species including: snakes, spiders and the marine snail of the genus Conus. The uniquely fascinating combinatorial ability of the marine snail, genus Conus to modify the pharmacological properties of these neurotoxins or conopeptides within its venom is depicted throughout this review. The myriad of posttranslational modifications and disulfide bonded architectures that have been identified in the conopeptides, are described with an emphasis on the unique pharmacological properties and receptor target specificities that have been ascribed to each of these modifications. The ability of NMR spectroscopy to provide three-dimensional structural information within the interaction interface for both the ligand and target protein following complex formation and its application to conopeptide drug discovery are discussed. Similarly, the strength of merging NMR spectroscopy data with ab initio "restrained soft-docking" for rational pharmacophore design and the identification of lead compounds from in silico library screens will also be discussed. The initial phases of this stratagem are illustrated using two toxin antagonists and the recently determined structure of the KcsA potassium channel. These data exemplify the utility of this approach in elucidating important molecular interfaces of specific toxin-receptor/ion channel complexes, which can be further exploited in drug discovery initiatives.
Cone snail venom toxins and neuroprotection
Rajendra W, Armugam A, Jeyaseelan K.(2004) Neuroprotection and peptide toxins. Brain Res Brain Res Rev. 45: 125-141. Review.
Department of Biochemistry, Faculty of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.
Abstract: Neurodegeneration induced by excitatory neurotransmitter glutamate is considered to be of particular relevance in several types of acute and chronic neurological impairments ranging from cerebral ischaemia to neuropathological conditions such as motor neuron disease, Alzheimer's, Parkinson's disease and epilepsy. The hyperexcitation of glutamate receptors coupled with calcium overload can be prevented or modulated by using well-established competitive and non-competitive antagonists targeting ion/receptor channels. The exponentially increasing body of pharmacological evidence over the years indicates potential applications of peptide toxins, due to their exquisite subtype selectivity on ion channels and receptors, as lead structures for the development of drugs for the treatment of wide variety of neurological disorders. This review comprehensively highlights the overview of the diversity in the molecular as well as neurobiological mechanisms of different peptide toxins derived from venomous animals [for conotoxins see pp. 130-135] with particular reference to neuroprotection. In addition, the potential applications of peptide toxins in the diagnosis and treatment of neurological disorders such as neuromuscular disorders, epilepsy, Alzheimer's and Parkinson's diseases, gliomas and ischaemic stroke and their future prospects in the diagnosis as well as in the therapy are addressed.
Clinical applications of conotoxins in pain and inflammation
Rajendra, W., Armugam, A. and Jeyaseelan, K. (2004) Toxins in anti-nociception and anti-inflammation. Toxicon 44: 1-17.
Department of Biochemistry, Faculty of Medicine, National University of Singapore, 8, Medical Drive, Singapore, Singapore 117597.
Abstract: The use of toxins as novel molecular probes to study the structure-function relationship of ion-channels and receptors as well as potential therapeutics in the treatment of wide variety of diseases is well documented. The high specificity and selectivity of these toxins have attracted a great deal of interest as candidates for drug development. This review highlights the involvement of the proteins and peptide toxins as well as non-proteinaceous compounds derived from both venomous and non-venomous animals, in anti-nociception and anti-inflammation. The possible mechanisms of these potential therapeutic agents and possible clinical applications in the treatment of pain and inflammation are also summarized.
20 August, 2004
Biotinylated mu-Conotoxin GIIIA probes sodium channels
Nakamura M, Ishida Y, Kohno T, Sato K, Oba Y, Nakamura H. (2004) Effects of modification at the fifth residue of mu-conotoxin GIIIA with bulky tags on the electrically stimulated contraction of the rat diaphragm. J Pept Res. 64: 110-117.
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601, Japan.
Abstract: mu-conotoxin GIIIA, a peptide toxin from the cone snail, blocks muscle-type sodium channels. Thr-5 of mu-conotoxin GIIIA, located on the opposite side of the active site in the globular molecule, was replaced by Cys to which the bulky tags were attached. The tagged mu-conotoxin GIIIA derivatives, except for the phospholipid-tagged one, exerted the biological activity with a potency slightly weaker than natural mu-conotoxin GIIIA. When the biotinylated tags of various lengths were added, the presence of avidin suppressed the action of the biotinylated toxins of <4 nm, but not with 5 nm. The bulky biotinylated tags are useful as a caliper to measure the depth of receptor sites in the channels.
19 August, 2004
alpha6-containing nicotinic receptors mediate dopamine release
Azam, L. and McIntosh, J.M. (2004) Effect of novel {alpha}-conotoxins on nicotine-stimulated [3H]dopamine release from rat striatal synaptosomes. J Pharmacol Exp Ther. 2004 Aug 17 [Epub ahead of print]
Abstract:Nicotine's action on the midbrain dopaminergic neurons is mediated by nicotinic acetylcholine receptors (nAChRs) that are present on the cell bodies and the terminals of these neurons. Previously, it was suggested that one of the nAChR subtypes located on striatal dopaminergic terminals may be an alpha3beta2 subtype, based on partial inhibition of nicotine-stimulated [(3)H]dopamine release by alpha-conotoxin MII, a potent inhibitor of heterologously expressed alpha3beta2 nAChRs. More recent studies indicated that alpha-conotoxin MII also potently blocks alpha6-containing nAChRs. In the present study, we have examined the nAChR subtype(s) modulating [(3)H]dopamine release from striatal terminals by using novel alpha-conotoxins that have 37-78 fold higher selectivity for alpha6- vs. alpha3-containing nAChRs. All of the peptides partially (20-35%) inhibit nicotine-stimulated [(3)H]dopamine release with IC50s consistent with those obtained with heterologously expressed rat alpha6-containing nicotinic acetylcholine receptors. These results, together with previous studies by others, further support the idea that alpha6-containing nicotinic receptors modulate nicotine-stimulated dopamine release from rat striatal synaptosomes.
13 August, 2004
Evolution of Conus feeding modes
Duda Jr TF, Palumbi SR. (2004) Gene expression and feeding ecology: evolution of piscivory in the venomous gastropod genus Conus. Proc R Soc Lond B Biol Sci. 271: 1165-1174.
Naos Marine Laboratory, Smithsonian Tropical Research Institute, Box 2072, Balboa, Ancon, Republic of Panama.
Abstract:Differential expression of gene-family members is typically associated with the specific development of certain tissues and organs, but its importance in the ecological adaptation of organisms has rarely been investigated. Several specialized feeding modes have evolved within the predatory marine gastropod genus Conus, including molluscivory and piscivory. Based on phylogenetic investigations of Conus species, it has been concluded that piscivory arose at least twice in this genus. Moreover, molecular analyses of conotoxin mRNA transcripts reveal that piscivores from independent evolutionary lineages express the same subset of four-loop conotoxins, contrary to phylogenetic expectations. These results demonstrate that differential expression of gene-family members can play a key role in adaptive evolution, particularly during shifts to new ecological niches.
11 August, 2004
9 August, 2004
3 New species of Conus described in VISAYA
VISAYA is a new malacological journal with taxonomical and nomenclatoral articles. In the first issue Guido T. Poppe, Manuel J. Tenorio, Carlos M. L. Afonso and Koen Fraussen have contributed with 5 articles containing 9 descriptions of new species of molluscs including 3 new species of Conus (Conus frausseni, Conus grohi and Conus terryni). Conus cuneolus and its relatives of Sal has been revised and documented. VISAYA, in A4, is printed in colour from cover to cover, the number 1 has 52 pages and 16 full page coloured plates. Numerious in text figures and maps.VISAYA is an occasional publication and will be published as manuscripts become available. Authors are invited to submit articles for publication.
9 August, 2004
Review: mu-Conotoxins, sodium channel antagonists
Li, R.A. and Tomaselli, G.F. (2004) Using the deadly micro-conotoxins as probes of voltage-gated sodium channels. Toxicon 44: 117-122.
The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Ross 871, Baltimore, MD 21205, USA.
Abstract:micro-Conotoxins (micro-CTX) are potent Na channel inhibitory peptides isolated from the venom of the predatory marine snail Conus geographus. micro-CTXs exert their biological action by physically occluding the ion-conducting pore of voltage-gated Na (Na(v)) channels with a 1:1 stoichiometry in an all-or-none fashion. This article reviews our current knowledge of the mechanism of micro-CTX and the associated structural and functional insights into its molecular target-Na(v) channels.
3 August, 2004
Review: Conopeptides as potential therapeutics
Livett, B.G., Gayler, K.R., Khalil, Z. (2004) Drugs from the sea: conopeptides as potential therapeutics. Curr Med Chem. 11: 1715-1723.
Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, 3010, Australia.
Abstract:Marine cone snails from the genus Conus are estimated to consist of up to 700 species. These predatory molluscs have devised an efficient venom apparatus that allows them to successfully capture polychaete worms, other molluscs or in some cases fish as their primary food sources. The toxic venom used by the cone shells contains up to 50 different peptides that selectively inhibit the function of ion channels involved in the transmission of nerve signals in animals. Each of the 700 Conus species contains a unique set of peptides in their venom. Across the genus Conus, the conotoxins represent an extensive array of ion channel blockers each showing a high degree of selectivity for particular types of channels. We have undertaken a study of the conotoxins from Australian species of Conus that have the capacity to inhibit specifically the nicotinic acetylcholine receptors in higher animals. These conotoxins have been identified by mass spectroscopy and their peptide sequences in some cases deduced by the application of modern molecular biology to the RNA extracted from venom ducts. The molecular biological approach has proven more powerful than earlier protein/peptide based technique tor the detection of novel conotoxins [1,2]. Novel conotoxins detected in this way have been further screened for their abilities to modify the responses of tissues to pain stimuli as a first step in describing their potential as lead compounds for novel drugs. This review describes the progress made by several research groups to characterise the properties of conopeptides and to use them as drug leads for the development of novel therapeutics for the treatment of a range of neurological conditions.
Peptide "turritoxins" from Turrids
Lopez-Vera, E., Heimer de la Cotera, E.P., Maillo, M., Riesgo-Escovar, J.R., Olivera B.M. and Aguilar, M.B. (2004) A novel structural class of toxins: the methionine-rich peptides from the venoms of turrid marine snails (Mollusca, Conoidea). Toxicon.43: 365-374.
Laboratory of Marine Neuropharmacology, Institute for Neurobiology, Universidad Nacional Autonoma de Mexico, Queretaro 76230, Mexico.
Abstract:The objective of this investigation was to purify and characterize polypeptides from the venom ducts of the turrid snails Polystira albida and Gemmula periscelida (superfamily: Conoidea, family: Turridae), collected in Mexican waters. Venoms of other groups in the superfamily (family: Conidae, genus: Conus) have peptide toxins ('conotoxins'), but no venom components have been characterized from any turrid species. Crude venoms were fractionated using reversed-phase high performance liquid chromatography, and one major component from each venom was characterized. In contrast to most conotoxins, the polypeptides characterized contain a high proportion of Met, Tyr and Arg residues, and few, if any, Cys residues. The two peptides had some regions of homology, but were not significantly similar to other peptides. Both peptides are predicted to contain alpha-helical structures, and the peptide from P. albida is predicted to form a coiled-coil motif. This structural motif could provide conformational stability for these turrid venom components ("turritoxins"), which in the case of conotoxins is primarily achieved by disulfide bonds. Thus, the first turritoxins characterized are strikingly different from the conotoxins, suggesting divergent biochemical strategies in the venoms of different major groups included in the superfamily Conoidea.
28 July, 2004
D'Alessandro, M., Paci, M. and Amadei, A. (2004) Characterization of the conformational behavior of peptide Contryphan Vn: a theoretical study. Biopolymers 74: 448-456.
Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy.
Abstract: In this work we report the study of a peptide, the Contryphan Vn produced by Conus ventricosus, a vermivorous cone snail living in the temperate Mediterranean sea. This cyclic peptide of nine residues is a ring closed by a Cys-Cys (Cys: cysteine) disulfide bond containing two proline (Pro) residues and two tryptophans (Trp), one of them being a D-Trp. We present a statistical mechanical characterization of the peptide, simulated in water for about 200 ns with classical molecular dynamics (MD). In recent years there has been a growing interest in the study of the mechanics and dynamics of biological molecules, and in particular for proteins and peptides, about the relationship between collective motions and the active conformations which exert the biological function. To this aim we used the essential dynamics analysis on the MD trajectory and extracted, from the total fluctuations of the molecule, the dominant dynamical modes responsible of the principal conformational transitions. The Contryphan Vn small size allowed us to investigate in details the all-atoms dynamics and the corresponding thermodynamics in conformational space defined by the most significant intramolecular motions.
Conotoxin GVIA- and CVID-sensitive N-type calcium channels in terminals of sacral preganglionic neurons.
Jobling, P., Gibbins, I.L., Lewis, R.J. and Morris, J.L. (2004) Differential expression of calcium channels in sympathetic and parasympathetic preganglionic inputs to neurons in paracervical ganglia of guinea-pigs. Neuroscience 127: 455-466.
Department of Anatomy and Histology, Centre for Neuroscience, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.
Abstract: Neurons in pelvic ganglia receive nicotinic excitatory post-synaptic potentials (EPSPs) from sacral preganglionic neurons via the pelvic nerve, lumbar preganglionic neurons via the hypogastric nerve or both. We tested the effect of a range of calcium channel antagonists on EPSPs evoked in paracervical ganglia of female guinea-pigs after pelvic or hypogastric nerve stimulation. omega-conotoxin GVIA (CTX GVIA, 100 nM) or the novel N-type calcium channel antagonist, CTX CVID (100 nM) reduced the amplitude of EPSPs evoked after pelvic nerve stimulation by 50-75% but had no effect on EPSPs evoked by hypogastric nerve stimulation. Combined addition of CTX GVIA and CTX CVID was no more effective than either antagonist alone. EPSPs evoked by stimulating either nerve trunk were not inhibited by the P/Q calcium channel antagonist, omega-agatoxin IVA (100 nM), nor the L-type calcium channel antagonist, nifedipine (30 microM). SNX 482 (300 nM), an antagonist at some R-type calcium channels, inhibited EPSPs after hypogastric nerve stimulation by 20% but had little effect on EPSPs after pelvic nerve stimulation. Amiloride (100 microM) inhibited EPSPs after stimulation of either trunk by 40%, while nickel (100 microM) was ineffective. CTX GVIA or CTX CVID (100 nM) also slowed the rate of action potential repolarization and reduced afterhyperpolarization amplitude in paracervical neurons. Thus, release of transmitter from the terminals of sacral preganglionic neurons is largely dependent on calcium influx through N-type calcium channels, although an unknown calcium channel which is resistant to selective antagonists also contributes to release. Release of transmitter from lumbar preganglionic neurons does not require calcium entry through either conventional N-type calcium channels or the variant CTX CVID-sensitive N-type calcium channel and seems to be mediated largely by a novel calcium channel.
Xenome announce Phase I clinical trial for Xen2174
In a Media Release, 20 July 2004, Xenome announced commencement of a Phase I clinical trial on its lead analgesic compound, Xen2174 (a chi-conotoxin that acts as a noradrenaline reuptake inhibitor). This Phase I trial is a randomised, placebo-controlled, double blind, dose-escalating study involving up to 20 healthy male volunteers. The primary purpose of this trial is to evaluate the safety and tolerability of Xen2174 following intravenous administration. "Additional information on the pharmacokinetics and potential anti-nociceptive effects of Xen2174 will also be examined during the trial", commented Xenome's Head of Drug Development, Dr Michael Thurn.
13 July, 2004
A novel alphaA((1-3))-conotoxin OIVA from milked venom of Conus obscurus
Teichert, R.W., Rivier, J., Dykert, J., Cervini, L., Gulyas, J., Bulaj, G., Ellison, M. and Olivera, B.M. (2004) alphaA-Conotoxin OIVA defines a new alphaA-conotoxin subfamily of nicotinic acetylcholine receptor inhibitors. Toxicon 44: 207-214.
Department of Biology, University of Utah, 254 South 1400 East, Salt Lake City, UT 84112, USA.
Abstract:The venoms of cone snails are rich in multiply disulfide-crosslinked peptides, the conotoxins. Conotoxins are grouped into families on the basis of shared cysteine patterns and homologous molecular targets. For example, both the kappaA- and alphaA-conotoxin families share the same Class IV Cys pattern (-CC-C-C-C-C-), but differ in their molecular targets. The kappaA-conotoxins are excitatory toxins that purportedly block potassium channels, while the alphaA-conotoxins are paralytic conotoxins that inhibit nicotinic acetylcholine receptors (nAChRs). In this work, we describe the isolation and characterization of a novel Conus peptide from venom milked from Hawaiian specimens of Conus obscurus. This peptide shares the Class IV Cys pattern but differs from both previously characterized alphaA- and kappaA-conotoxins in the spacing of amino acids between Cys resides. However, the peptide is similar to previously characterized alphaA-conotoxins in its paralytic effects on fish and its antagonist activity on the neuromuscular nAChR. Unexpectedly, the peptide differs in its disulfide bonding from alphaA-conotoxin PIVA. We have named this unique peptide alphaA-conotoxin OIVA, and we consider it the defining member of a subfamily of alphaA-conotoxins that we designate the alphaA((1-3))-conotoxins to identify them by their unique disulfide bonding framework. These results indicate that the alphaA-conotoxin family is both more structurally diverse and broadly distributed than previously believed.
A benzothiazole-derived mimetic of omega-conotoxin GVIA
Baell, J.B., Duggan, P.J., Forsyth, S.A., Lewis, R.J., Phei Lok, Y. and Schroeder, C.I. (2004) Synthesis and biological evaluation of nonpeptide mimetics of omega-conotoxin GVIA. Bioorg Med Chem.12: 4025-4037.
School of Chemistry, Monash University, Clayton, Vic 3800, Australia.
Abstract: A benzothiazole-derived compound (4a) designed to mimic the C(alpha)-C(beta) bond vectors and terminal functionalities of Lys2, Tyr13 and Arg17 in omega-conotoxin GVIA was synthesised, together with analogues (4b-d), which had each side-chain mimic systematically truncated or eliminated. The affinity of these compounds for rat brain N-type and P/Q-type voltage gated calcium channels (VGCCs) was determined. In terms of N-type channel affinity and selectivity, two of these compounds (4a and 4d) were found to be highly promising, first generation mimetics of omega-conotoxin. The fully functionalised mimetic (4a) showed low microM binding affinity to N-type VGCCs (IC(50)=1.9microM) and greater than 20-fold selectivity for this channel sub-type over P/Q-type VGCCs, whereas the mimetic in which the guanidine-type side chain was truncated back to an amine (4d, IC(50)= 4.1microM) showed a greater than 25-fold selectivity for the N-type channel.
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