Characterization of a Novel α-Conotoxin from Conus textile That Selectively Targets α6/α3β2β3 Nicotinic Acetylcholine Receptors

Abstract

α6β2 Nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic neurons in the CNS are potential therapeutic targets for the treatment of several neuropsychiatric diseases, including nicotine addiction and Parkinson disease. However, recent studies indicate that the α6 subunit can also associate with the β4 subunit to form α6β4 nAChRs that are difficult to pharmacologically distinguish from α6β2, α3β4, and α3β2 subtypes. The current study characterized a novel 16-amino acid α-conotoxin (α-CTx) TxIB from Conus textile whose sequence is GCCSDPPCRNKHPDLC-amide as deduced from gene cloning. The peptide and an analog with an additional C-terminal glycine were chemically synthesized and tested on rat nAChRs heterologously expressed in Xenopus laevis oocytes. α-CTx TxIB blocked α6/α3β2β3 nAChR with an IC50 of 28 nm. In contrast, the peptide showed little or no block of other tested subtypes at concentrations up to 10 μm. The three-dimensional solution structure of α-CTx TxIB was determined using NMR spectroscopy. α-CTx TxIB represents a uniquely selective ligand for probing the structure and function of α6β2 nAChRs.Background: Cone snails are a rich source of α-conotoxins that target nicotinic acetylcholine receptors (nAChR).Results: A new α-conotoxin TxIB potently blocked α6/α3β2β3 nAChRs with high selectivity.Conclusion: TxIB is an effective inhibitor of α6/α3β2β3 nAChRs. Its structure was determined by NMR.Significance: TxIB is a new, uniquely selective ligand for querying the structure and function of nAChRs and designing therapeutic drugs. α6β2 Nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic neurons in the CNS are potential therapeutic targets for the treatment of several neuropsychiatric diseases, including nicotine addiction and Parkinson disease. However, recent studies indicate that the α6 subunit can also associate with the β4 subunit to form α6β4 nAChRs that are difficult to pharmacologically distinguish from α6β2, α3β4, and α3β2 subtypes. The current study characterized a novel 16-amino acid α-conotoxin (α-CTx) TxIB from Conus textile whose sequence is GCCSDPPCRNKHPDLC-amide as deduced from gene cloning. The peptide and an analog with an additional C-terminal glycine were chemically synthesized and tested on rat nAChRs heterologously expressed in Xenopus laevis oocytes. α-CTx TxIB blocked α6/α3β2β3 nAChR with an IC50 of 28 nm. In contrast, the peptide showed little or no block of other tested subtypes at concentrations up to 10 μm. The three-dimensional solution structure of α-CTx TxIB was determined using NMR spectroscopy. α-CTx TxIB represents a uniquely selective ligand for probing the structure and function of α6β2 nAChRs. Background: Cone snails are a rich source of α-conotoxins that target nicotinic acetylcholine receptors (nAChR). Results: A new α-conotoxin TxIB potently blocked α6/α3β2β3 nAChRs with high selectivity. Conclusion: TxIB is an effective inhibitor of α6/α3β2β3 nAChRs. Its structure was determined by NMR. Significance: TxIB is a new, uniquely selective ligand for querying the structure and function of nAChRs and designing therapeutic drugs.