A Novel Î±4/7-Conotoxin Lvia From Conus Lividus That Selectively Blocks Î±3Î²2 Vs. Î±6/Î±3Î²2Î²3 Nicotinic Acetylcholine Receptors
This study was performed to discover and characterize the first potent Î±3Î²2-subtype-selective nicotinic acetylcholine receptor (nAChR) ligand. A novel Î±4/7-conotoxin, Î±-CTxLvIA, was cloned from Conus lividus. Its pharmacological profile at Xenopus laevis oocyte-expressed rat nAChR subtypes was determined by 2-electrode voltage-clamp electrophysiology, and its 3-dimensional (3D) structure was determined by NMR spectroscopy. Î±-CTx LvIA is a 16-aa C-terminallyamidated peptide with 2-disulfide bridges. Using rat subunits expressed in Xenopus oocytes, we found the highest affinity of Î±-CTxLvIA was for Î±3Î²2 nAChRs (IC50 8.7 nM), where blockade was reversible within 2 min. IC50 values were >100 nM at Î±6/Î±3Î²2Î²3, Î±6/ Î±3Î²4, and Î±3Î²4 nAChRs, and â‰¥3 Î¼M at all other subtypes tested. Î±3Î²2 vs. Î±6Î²2 subtype selectivity was confirmed for human-subunit nAChRs with much greater preference (300-fold) for Î±3Î²2 over Î±6Î²2 nAChRs. This is the first Î±-CTx reported to show high selectivity for human Î±3Î²2 vs. Î±6Î²2 nAChRs. Î±-CTxLvIA adopts two similarly populated conformations water: one (assumed to be bioactive) is highly structured, whereas the other is mostly random coil in nature. Selectivity differences with the similarly potent, but less selective, Î±3Î²2 nAChR antagonist Î±-CTx PeIA probably reside within the three residues, which differ in loop 2, given their otherwise similar 3D structures. Î±4/7-CTx LvIA is a new, potent, selective Î±3Î²2 nAChR antagonist, which will enable detailed studies of Î±3Î²2 nAChR structure, function, and physiological roles. Â© FASEB.
Digital Object Identifier (DOI)
Luo, Sulan; Zhangsun, Dongting; Schroeder, Christina I.; Zhu, Xiaopeng; Hu, Yuanyan; Wu, Yong; Weltzin, Maegan M.; Eberhard, Spencer; Kaas, Quentin; Craik, David J.; McIntosh, J. Michael; and Whiteaker, Paul, "A Novel Î±4/7-Conotoxin Lvia From Conus Lividus That Selectively Blocks Î±3Î²2 Vs. Î±6/Î±3Î²2Î²3 Nicotinic Acetylcholine Receptors" (2014). Neurobiology. 378.