Conantokin-T: A γ-carboxyglutamate containing peptide with N-methyl-D-aspartate antagonist activity (original) (raw)
Related papers
Novel Conantokins from Conus parius Venom Are Specific Antagonists of N-Methyl-D-aspartate Receptors
Journal of Biological Chemistry, 2007
We report the discovery and characterization of three conantokin peptides from the venom of Conus parius. Each peptide (conantokin-Pr1, -Pr2, and -Pr3) contains 19 amino acids with three ␥-carboxyglutamate (Gla) residues, a post-translationally modified amino acid characteristic of conantokins. The new peptides contain several amino acid residues that differ from previous conantokin consensus sequences. Notably, the new conantokins lack Gla at the 3rd position from the N terminus, where the Gla residue is replaced by either aspartate or by another post-translationally modified residue, 4-trans-hydroxyproline. Conantokin-Pr3 is the first conantokin peptide to have three different post-translational modifications. Conantokins-Pr1 and -Pr2 adopt ␣-helical conformations in the presence of divalent cations (Mg 2؉ and Ca 2؉ ) but are generally unstructured in the absence of divalent cations. Conantokin-Pr3 adopts an ␣-helical conformation even in the absence of divalent cations. Like other conantokins, the new peptides induced sleep in young mice and hyperactivity in older mice upon intracranial injection. Electrophysiological assays confirmed that conantokins-Pr1, -Pr2, and -Pr3 are N-methyl-Daspartate (NMDA) receptor antagonists, with highest potency for NR2B-containing NMDA receptors. Conantokin-Pr3 demonstrated ϳ10-fold selectivity for NR2B-containing NMDA receptors. However, conantokin-Pr2 showed minimal differences in potency between NR2B and NR2D. Conantokins-Pr1, -Pr2, and -Pr3 all demonstrated high specificity of block for NMDA receptors, when tested against various ligand-gated ion channels. Conus parius conantokins allow for a better definition of structural and functional features of conantokins as ligands targeting NMDA receptors.
A sleep-inducing peptide from Conus geographus venom
Toxicon : official journal of the International Society on Toxinology, 1985
A novel peptide toxin, which causes a sleep-like state upon intracerebral injection in mice, has been purified to homogeneity from the venom of the piscivorous marine snail Conus geographus L. It elicits no obvious effects when injected i.p. into either mice or fish. The purified toxin is a highly acidic heptadecapeptide with no cystine residues (Lys1, Arg1, Asx2, Ser1, Glx7-8, Gly1, Ile1, Leu2). This composition is in marked contrast to those of other conotoxins, which are basic and disulphide-bridged. The N-terminal residue is Gly and the COOH-terminal sequence is Ser-Asn-NH2.
Conantokin-L, a new NMDA receptor antagonist: determinants for anticonvulsant potency
Epilepsy Research, 2002
Conantokins are N -methyl-D-aspartate receptor antagonist peptides found in the venoms of marine cone snails. Current intense interest in this peptide family stems from the discovery of their therapeutic potential as anticonvulsants. It was recently reported that conantokin-R is a highly potent anticonvulsant compound, with a protective index of 17.5 when tested in the audiogenic mouse model of epilepsy. Conantokin-L was characterized from Conus lynceus and found to have extensive homology with conantokin-R, except For the C-terminal amino acids. Although conantokin-L appears almost as potent as conantokin-R in standard in vivo assays for conantokins and NMDA receptor binding assays, it is far less potent as an anticonvulsant, with a protective index of 1.2 in the audiogenic mouse model. The results suggest that the C-terminal sequences of conantokin-R and conantokin-L are a major determinant of their anticonvulsant potency. #
Biochemistry, 2016
Conantokins (con) are short γ-carboxyglutamate (Gla)-containing polypeptides expressed by marine snails that function as antagonists of N-methyl-Daspartate receptor (NMDAR) ion channels. The Gla residues govern structural conformations and antagonistic activities of the conantokins. In addition to Gla, some conantokins, e.g., conRl-B, also contain a hydroxyproline (HyP or O) residue, which in this case is centrally located in the peptide at position 10. Because conRl-B specifically inhibits ion channels of GluN2B subunit-containing heterotetrameric NMDARs, we evaluated the unusual role of HyP 10 in this effect. To accomplish this goal, we examined synthetic variants of conRl-B in which HyP 10 was either deleted (conRl-B[ΔO 10 ]) or replaced with alanine (conRl-B[O 10 A]) or proline (conRl-B[O 10 P]). The solution structures of these variants were determined by nuclear magnetic resonance spectroscopy. Deletion of HyP 10 , or replacement of HyP 10 with Ala 10 , attenuated the distortion in the central region of the apo-conRl-B helix and allowed Mg 2+-complexed end-to-end α-helix formation. The inhibitory properties of these variants were assessed by measuring NMDA/Gly-stimulated intracellular Ca 2+ influx in mice neurons. ConRl-B[O 10 P] retained its NMDAR ion channel inhibitory activity in wild-type (WT) neurons but lost its GluN2B specificity, whereas conRl-B[ΔO 10 ] showed overall diminished inhibitory function. ConRl-B[O 10 A] showed attenuated inhibitory function but retained its GluN2B specificity. Thus, HyP 10 plays a critical role in maintaining the structural integrity of conRl-B, which can be correlated with its GluN2B subunit-selective inhibition. Weakened inhibition by conRl-B was also observed in neurons lacking either the GluN2C or GluN2D subunit, compared to WT neurons. This suggests that GluN2C and GluN2D are also required for inhibition by conRl-B. M arine snails belonging to the Conus species produce a cocktail of peptides in their venoms, viz., conotoxins, that inhibit various receptors of the nervous system, such as Ca 2+ , Na + , and acetylcholine channels. 1 These neuroactive peptides of ∼20−30 amino acid residues experience extensive post-translational modifications that include disulfide bonds, epimerized leucine, brominated tryptophan, hydroxylated proline, and C-terminal amidation. 2 Subsets of conotoxins, viz., the conantokins, contain γ-carboxyglutamate (Gla) residues and generally lack disulfide bonds. These peptides function as allosteric inhibitors of the ion channels of N-methyl-D-aspartate receptors (NMDARs). Appropriately spaced Gla residues play an integral role in conferring well-defined structural and antagonistic properties to these peptides. Some conantokins (con), e.g., con-T, con-R, and con-Pr3, 3−5 are inherently helical in nature, whereas con-G, con-Pr1, and con-Pr2 are unstructured but adopt α-helical structures in the presence of Ca 2+ or Mg 2+. 5,6 As functional inhibitors of the NMDAR, which consists of various types of subunits, the nature of which depends on their locations and the developmental status of neuronal cells, several of the conantokins show subunit-specific antagonistic activity and have been exploited as neuroprotective agents.
Carboxyglutamate in a Neuroactive Toxin
The venom of a fish-hunting cone snail (Conus geo-graphus) contains a novel toxin, the "sleeper" peptide, which induces a sleep-like state in mice when injected intracerebrally. We demonstrate that this peptide contains 5 mol of 'Y-carboxyglutamate (Gla) in 17 amino acids. We have described the isolation and properties of a variety of peptide toxins from the venoms of two piscivorous snails, Conus geographus Linn. and C. magus Linn. (1-4)Y Most recently we reported 3 the purification of a peptide from C. geographus that has a most remarkable biological activity, i.e. intracerebral injection of submicrogram amounts into young mice induces a prolonged sleep-like state. Unlike the other toxins we have found, this peptide lacks disulfide bridges and is extremely acidic rather than basic. We report here the complete amino acid sequence of the sleeper peptide, conotoxin GV, which is as remarkable as the biological activity; it contains five residues of 'Y-carboxyglu-tama...
Gamma-carboxyglutamate in a neuroactive toxin
Journal of Biological Chemistry, 1984
The venom of a fish-hunting cone snail (Conus geographus) contains a novel toxin, the "sleeper" peptide, which induces a sleep-like state in mice when injected intracerebrally. We demonstrate that this peptide contains 5 mol of y-carboxyglutamate (Gla) in 17 amino acids. The amino acid sequence of the sleeper peptide is
European Journal of Pharmacology: Molecular Pharmacology, 1992
The conantokins arc a family of pcptides isolated from the venom of prcdatmy marine ,~nails of the genus Crmus. Here we demonstrate that one of these peptides, conantokin-G, specifically inhibits the N-methyI-D-aspartate (NMDA) subtype of glutamate receptors that are expressed in mouse brain mRNA-injected Xenopus oocytes. Increasing the concentration of conantokin-G causes the NMDA dose-response curvc to shift to progressively higher concenlratk-ns. Wc lhercforc conclude that conantokin-G interacts with the glutamate binding site of the receptor. In contrast, the pcptide does not compete with glycine, and this indicates thai conantokin-G does not act at the binding sil¢ of this co-agonist of the NMDA receptor. Furlhcrnmrc, the inhibitory effects of conanlokin-G appear to be insensitive to membrane potential. NMDA receptor; Oocytes (XenOlmS): Conantokin
PLoS ONE, 2013
Three members of a family of small neurotoxic peptides from the venom of Conus parius, conantokins (Con) Pr1, Pr2, and Pr3, function as antagonists of N-methyl-D-aspartate receptors (NMDAR). We report structural characterizations of these synthetic peptides, and also demonstrate their antagonistic properties toward ion flow through NMDAR ion channels in primary neurons. ConPr1 and ConPr2 displayed moderate increases in α-helicity after addition of Mg 2+. Native apo-ConPr3 possessed an α-helical conformation, and the helicity increased only slightly on addition of Mg 2+. Additionally, these peptides diminished NMDA/Gly-mediated currents and intracellular Ca 2+ (iCa 2+) influx in mature rat primary hippocampal neurons. Electrophysiological data showed that these peptides displayed slower antagonistic properties toward the NMDAR than conantokins from other species of cone snails, e.g., ConT and ConG. Furthermore, to demonstrate selectivity of the C. parius-derived conantokins towards specific NMDAR subunits, cortical neurons from GluN2A-/-and GluN2B-/-mice were utilized. Robust inhibition of NMDARmediated stimulation in GluN2A-/-derived mouse neurons, as compared to those isolated from GluN2B-/-mouse brains, was observed, suggesting a greater selectivity of these antagonists towards the GluN2B subunit. These C. parius conantokins mildly inhibited NMDAR-induced phosphorylation of CREB at Ser 133 , suggesting that the peptides modulated iCa 2+ entry and, thereby, activation of CREB, a transcription factor that is required for maintaining longterm synaptic activity. Our data mechanistically show that while these peptides effectively antagonize NMDARdirected current and iCa 2+ influx, receptor-coupled CREB signaling is maintained. The consequence of sustained CREB signaling is improved neuronal plasticity and survival during neuropathologies.