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A Conus regularis Conotoxin with a Novel Eight-Cysteine Framework Inhibits CaV2.2 Channels and Displays an Anti-Nociceptive Activity
Molecular Immunology and Biotoxins Laboratory, Marine Biotechnology Department, Scientific Research and High Education Center from Ensenada (CICESE), Carretera Ensenada-Tijuana #3918, Zona Playitas, Ensenada 22860, Mexico
Chemistry Biomacromolecules Department, Chemistry Institute, National Autonomous University of Mexico, Av. Universidad 3000, Ciudad Universitaria, PO BOX 70-213, D.F. 04510, Mexico
Physiology Department, Medicine Faculty, National Autonomous University of Mexico, Av. Universidad 3000, Ciudad Universitaria, PO BOX 70-250, D.F. 04510, Mexico
Department of Molecular Medicine and Bioprocesses, National Autonomous University of Mexico, Av. Universidad 2001, C.P. 510-3, Cuernavaca 61500, Mexico
* Author to whom correspondence should be addressed.
Received: 7 February 2013; in revised form: 5 March 2013 / Accepted: 18 March 2013 / Published: 8 April 2013
Abstract: A novel peptide, RsXXIVA, was isolated from the venom duct of Conus regularis, a worm-hunting species collected in the Sea of Cortez, México. Its primary structure was determined by mass spectrometry and confirmed by automated Edman degradation. This conotoxin contains 40 amino acids and exhibits a novel arrangement of eight cysteine residues (C-C-C-C-CC-CC). Surprisingly, two loops of the novel peptide are highly identical to the amino acids sequence of ω-MVIIA. The total length and disulfide pairing of both peptides are quite different, although the two most important residues for the described function of ω-MVIIA (Lys2 and Tyr13) are also present in the peptide reported here. Electrophysiological analysis using superior cervical ganglion (SCG) neurons indicates that RsXXIVA inhibits CaV2.2 channel current in a dose-dependent manner with an EC50 of 2.8 μM, whose effect is partially reversed after washing. Furthermore, RsXXIVA was tested in hot-plate assays to measure the potential anti-nociceptive effect to an acute thermal stimulus, showing an analgesic effect in acute thermal pain at 30 and 45 min post-injection. Also, the toxin shows an anti-nociceptive effect in a formalin chronic pain test. However, the low affinity for CaV2.2 suggests that the primary target of the peptide could be different from that of ω-MVIIA.
Keywords: Conus regularis; nociceptive; calcium channel; eight-cysteine toxin and conotoxins
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Bernáldez, J.; Román-González, S.A.; Martínez, O.; Jiménez, S.; Vivas, O.; Arenas, I.; Corzo, G.; Arreguín, R.; García, D.E.; Possani, L.D.; Licea, A. A Conus regularis Conotoxin with a Novel Eight-Cysteine Framework Inhibits CaV2.2 Channels and Displays an Anti-Nociceptive Activity. Mar. Drugs 2013, 11, 1188-1202.
Bernáldez J, Román-González SA, Martínez O, Jiménez S, Vivas O, Arenas I, Corzo G, Arreguín R, García DE, Possani LD, Licea A. A Conus regularis Conotoxin with a Novel Eight-Cysteine Framework Inhibits CaV2.2 Channels and Displays an Anti-Nociceptive Activity. Marine Drugs. 2013; 11(4):1188-1202.
Bernáldez, Johanna; Román-González, Sergio A.; Martínez, Oscar; Jiménez, Samanta; Vivas, Oscar; Arenas, Isabel; Corzo, Gerardo; Arreguín, Roberto; García, David E.; Possani, Lourival D.; Licea, Alexei. 2013. "A Conus regularis Conotoxin with a Novel Eight-Cysteine Framework Inhibits CaV2.2 Channels and Displays an Anti-Nociceptive Activity." Mar. Drugs 11, no. 4: 1188-1202.