Novel omega-conotoxins from Conus catus discriminate among neuronal calcium channel subtypes.
omega-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 omega-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 omega-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, omega-conotoxins CVID and MVIIA had similar potencies to inhibit current through central (alpha(1B-d)) and peripheral (alpha(1B-b)) splice variants of the rat N-type calcium channels when coexpressed with rat beta(3) in Xenopus oocytes. However, the potency of CVID and MVIIA increased when alpha(1B-d) and alpha(1B-b) were expressed in the absence of rat beta(3), an effect most pronounced for CVID at alpha(1B-d) (up to 540-fold) and least pronounced for MVIIA at alpha(1B-d) (3-fold). The novel selectivity of CVID may have therapeutic implications. (1)H 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.
Centre for Drug Design and Development (3D Centre), Institute for Molecular Bioscience, Department of Physiology and Pharmacology, CSIRO Tropical Agriculture, and Queensland Agricultural Biotechnology Centre (QDPI), Australia. r.lewis@mailbox.uq.edu.au
R J
RJ
Lewis
K J
KJ
Nielsen
D J
DJ
Craik
M L
ML
Loughnan
D A
DA
Adams
I A
IA
Sharpe
T
T
Luchian
D J
DJ
Adams
T
T
Bond
L
L
Thomas
A
A
Jones
J L
JL
Matheson
R
R
Drinkwater
P R
PR
Andrews
P F
PF
Alewood
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006860:Hydrogen Bonding; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010452:Peptide Biosynthesis; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D020033:Protein Isoforms; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012908:Snails; D013997:Time Factors; D014649:Vas Deferens / Q000378:metabolism; D014982:Xenopus laevis; D020960:omega-Conotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018076:DNA, Complementary; D007477:Ions; D010455:Peptides; D020033:Protein Isoforms; D012333:RNA, Messenger; D020960:omega-Conotoxins; C078452:ziconotide