Characterization of a T-superfamily conotoxin TxVC from Conus textile that selectively targets neuronal nAChR subtypes

T-superfamily conotoxins have a typical cysteine pattern of CC-CC, and are known to mainly target calcium or sodium ion channels. Recently, we screened the targets of a series of T-superfamily conotoxins and found that a new T-superfamily conotoxin TxVC (KPCCSIHDNSCCGL-NH2) from the venom of Conus textile. It selectively targeted the neuronal nicotinic acetylcholine receptor (nAChR) subtypes alpha 4 beta 2 and alpha 3 beta 2, with IC50 values of 343.4 and 1047.2 nM, respectively, but did not exhibit obvious pharmacological effects on voltage-gated potassium, sodium or calcium channel in DRG cells, the BK channels expressed in HEK293 cells, or the Kv channels in L beta T2 cells. The changes in the inhibitory activities of its Ala mutants, the NMR structure, and molecular simulation results based on other conotoxins targeting nAChR alpha 4 beta 2, all demonstrated that the residues Ile(6) and Leu(14) were the main hydrophobic pharmacophores. To our best knowledge, this is the first T-superfamily conotoxin that inhibits neuronal nAChRs and possesses high binding affinity to alpha 4 beta 2. This finding will expand the knowledge of the targets of T-superfamily conotoxins and the motif information could help the design of new nAChR inhibitors. (C) 2014 Elsevier Inc. All rights reserved.