| Abstrakt: |
This study was performed to discover and characterize the first potent α3ß2-subtype-selective nicotinic acetylcholine receptor (nAChR) ligand. A novel α4/7-conotoxin, α-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. α-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 a-CTxLvIA was for α3ß2 nAChRs (IC50 8.7 nM), where blockade was reversible within 2 min. IC50 values were >100 nM at α6/α3ß2ß3, α?/ α3ß4, and α3ß4 nAChRs, and >3 pM at all other subtypes tested. α3ß2 vs. α6ß2 subtype selectivity was confirmed for human-subunit nAChRs with much greater preference (300-fold) for α3ß2 over α6ß2 nAChRs. This is the first a-CTx reported to show high selectivity for human α3ß2 vs. α6ß2 nAChRs. α-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, α3ß2 nAChR antagonist α-CTx PeIA probably reside within the three residues, which differ in loop 2, given their otherwise similar 3D structures. α4/7 - C Tx LvIA is a new, potent, selective α3ß2 nAChR antagonist, which will enable detailed studies of α3ß2 nAChR structure, function, and Conus lividus that selectively blocks studies of a3ß2 nAChR structure, function, and physiological roles.--Luo, S., Zhangsun, D., Schroeder, C. I., Zhu, X., Hu, Y., Wu, Y., Weltzin, M. M., Eberhard, S., Raas, Q., Craik, D. J., Mcintosh, J. M., Whiteaker, P. A novel α4/7-conotoxin LvIA from Conus lividus that selectively blocks α3ß2 vs. α3ß2ß3 nicotinic acetylcholine receptors. [ABSTRACT FROM AUTHOR] |
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