New conopeptides of the D-superfamily selectively inhibiting neuronal nicotinic acetylcholine receptors

The venom of cone snails (Conus spp.) is a rich source of peptides exhibiting a wide variety of biological activities. Several of these conopeptides are neuronal nicotinic acetylcholine receptor (nAChR) antagonists and belong to the A-, M-, S-, C and the recently described D-superfamily (αD-conopeptides). Here we describe the discovery and characterization of two αD-conopeptides isolated from the venom of Conus mustelinus and Conus capitaneus. Their primary structure was determined by Edman degradation, MS/MS analysis and by a PCR based approach. These peptides show close structural homology to the αD-VxXIIA, -B and -C conopeptides from the venom of Conus vexillum and are dimers (about 11 kDa) of similar or identical peptides with 49 amino acid residues and a characteristic arrangement of ten conserved cysteine residues. These novel types of conopeptides specifically block neuronal nAChRs of the α7, α3β2 and α4β2 subtypes in nanomolar concentrations. Due to their high affinity, these new ligands may provide a tool to decipher the localisation and function of the various neuronal nAChRs.