Novel ω-Conotoxins from Conus catus Discriminate among Neuronal Calcium Channel Subtypes

• Published in: The Journal of biological chemistry 2000-11, Vol.275 (45), p.35335-35344
• Main Authors: Lewis, Richard J., Nielsen, Katherine J., Craik, David J., Loughnan, Marion L., Adams, Denise A., Sharpe, Iain A., Luchian, Tudor, Adams, David J., Bond, Trudy, Thomas, Linda, Jones, Alun, Matheson, Jodi-Lea, Drinkwater, Roger, Andrews, Peter R., Alewood, Paul F.
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Amino Acid Sequence; Animals; Base Sequence; Brain - metabolism; Calcium Channel Blockers - pharmacology; Calcium Channels - metabolism; Chromatography, High Pressure Liquid; Cloning, Molecular; conotoxins; Conus catus; DNA, Complementary - metabolism; Dose-Response Relationship, Drug; Electrophysiology; Hydrogen Bonding; Ions; Magnetic Resonance Spectroscopy; Male; Mass Spectrometry; Models, Molecular; Molecular Sequence Data; Neurons - metabolism; omega -Conotoxin; omega-Conotoxins - chemistry; omega-Conotoxins - genetics; omega-Conotoxins - metabolism; omega-Conotoxins - pharmacology; Oocytes - metabolism; Peptide Biosynthesis; Peptides - chemistry; Protein Binding; Protein Conformation; Protein Isoforms; Protein Structure, Secondary; Rats; Rats, Wistar; RNA, Messenger - metabolism; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; Snails; Time Factors; Vas Deferens - metabolism; Xenopus laevis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M002252200

ω-Conotoxins selective for N-type calcium channels are useful in the management of severe pain. In an attempt to expand the therapeutic potential of this class, four new ω-conotoxins (CVIA–D) have been discovered in the venom of the piscivorous cone snail, Conus catus, using assay-guided fractionation and gene cloning. Compared with other ω-conotoxins, CVID has a novel loop 4 sequence and the highest selectivity for N-type over P/Q-type calcium channels in radioligand binding assays. CVIA−D also inhibited contractions of electrically stimulated rat vas deferens. In electrophysiological studies, ω-conotoxins CVID and MVIIA had similar potencies to inhibit current through central (α1B-d) and peripheral (α1B-b) splice variants of the rat N-type calcium channels when coexpressed with rat β3 in Xenopus oocytes. However, the potency of CVID and MVIIA increased when α1B-d and α1B-b were expressed in the absence of rat β3, an effect most pronounced for CVID at α1B-d (up to 540-fold) and least pronounced for MVIIA at α1B-d (3-fold). The novel selectivity of CVID may have therapeutic implications. 1H NMR studies reveal that CVID possesses a combination of unique structural features, including two hydrogen bonds that stabilize loop 2 and place loop 2 proximal to loop 4, creating a globular surface that is rigid and well defined.