ABSTRACT
In the original publication of the article the keywords are incorrectly online published. The correct keywords should read as α-Conotoxin; Nicotinc acetylcholine receptor; Acetylcholine binding protein; X-ray crystallography".
ABSTRACT
AIM:To compared the differential sensitivity of nicotinic acetycholine receptors (nAChRs) consisting of α and β subunits with different ratios.METHODS:The cRNA of α and β subunits was obtained by in vitro transcription.The α3β2 and α3β4 nAChR subtypes were expressed in Xenopus laevis oocytes by microinjection of cRNA coding α and β subunits at α∶β ratios of 1∶10, 1∶1 and 10∶1.The pharmacological activities of nAChRs to agonist acetycholine (ACh) and antagonist α-conotoxin (CTx) RegⅡA were investigated by two-electrode voltage-clamp techniques.RESULTS:For α3β2 nAChR expressed at the ratios of 1∶10, 1∶1 and 10∶1, the EC50 values of ACh were 91.2 μmol/L, 104.4 μmol/L and 130.6 μmol/L, respectively, while the IC50 values of α-CTx RegⅡA were 40.2 nmol/L, 36.4 nmol/L and 42.3 nmol/L, respectively.For α3β4 nAChR at the ratios of 1∶10, 1∶1 and 10∶1, the EC50 values of ACh were 44.0 μmol/L, 110.0 μmol/L and 230.0 μmol/L, respectively, while the IC50 values of α-CTx RegⅡA were 226.8 nmol/L, 71.5 nmol/L and 49.4 nmol/L, respectively.CONCLUSION:The results imply that the α3 and β4 subunit stoichiometry can change the structure and pharmacological activity of α3β4 nAChR, but the stoichiometry of α3 and β2 subunits has no effect on α3β2 nAChR.
ABSTRACT
The α3* nAChRs, which are considered to be promising drug targets for problems such as pain, addiction, cardiovascular function, cognitive disorders etc., are found throughout the central and peripheral nervous system. The α-conotoxin (α-CTx) LvIA has been identified as the most selective inhibitor of α3β2 nAChRs known to date, and it can distinguish the α3β2 nAChR subtype from the α6/α3β2β3 and α3β4 nAChR subtypes. However, the mechanism of its selectivity towards α3β2, α6/α3β2β3, and α3β4 nAChRs remains elusive. Here we report the co-crystal structure of LvIA in complex with Aplysia californica acetylcholine binding protein (Ac-AChBP) at a resolution of 3.4 Å. Based on the structure of this complex, together with homology modeling based on other nAChR subtypes and binding affinity assays, we conclude that Asp-11 of LvIA plays an important role in the selectivity of LvIA towards α3β2 and α3/α6β2β3 nAChRs by making a salt bridge with Lys-155 of the rat α3 subunit. Asn-9 lies within a hydrophobic pocket that is formed by Met-36, Thr-59, and Phe-119 of the rat β2 subunit in the α3β2 nAChR model, revealing the reason for its more potent selectivity towards the α3β2 nAChR subtype. These results provide molecular insights that can be used to design ligands that selectively target α3β2 nAChRs, with significant implications for the design of new therapeutic α-CTxs.