A novel ?4/7-conotoxin LvIA from Conus lividus that selectively blocks ?3?2 vs. ?6/?3?2?3 nicotinic acetylcholine receptors.

ABSTRACT: This study was performed to discover and characterize the first potent ?3?2-subtype-selective nicotinic acetylcholine receptor (nAChR) ligand. A novel ?4/7-conotoxin, ?-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. ?-CTx LvIA is a 16-aa C-terminally-amidated peptide with 2-disulfide bridges. Using rat subunits expressed in Xenopus oocytes, we found the highest affinity of ?-CTxLvIA was for ?3?2 nAChRs (IC50 8.7 nM), where blockade was reversible within 2 min. IC50 values were >100 nM at ?6/?3?2?3, ?6/?3?4, and ?3?4 nAChRs, and ?3 ?M at all other subtypes tested. ?3?2 vs. ?6?2 subtype selectivity was confirmed for human-subunit nAChRs with much greater preference (300-fold) for ?3?2 over ?6?2 nAChRs. This is the first ?-CTx reported to show high selectivity for human ?3?2 vs. ?6?2 nAChRs. ?-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, ?3?2 nAChR antagonist ?-CTx PeIA probably reside within the three residues, which differ in loop 2, given their otherwise similar 3D structures. ?4/7-CTx LvIA is a new, potent, selective ?3?2 nAChR antagonist, which will enable detailed studies of ?3?2 nAChR structure, function, and physiological roles.

SUBMITTER: Luo S 

PROVIDER: S-EPMC3963015 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature