Conopeptide discovery through calcium imaging

Cone snail venoms contain numerous peptide toxins (conopeptides or conotoxins), many of which target voltage-gated and ligand-gated ion channels. Conotoxins are a diverse group of peptides that generally exhibit significant selectivity and affinity, making them useful experimental tools for discriminating between the myriad of ion channel isoforms and studying ion channel structure-function relationships. Researchers have used a variety of single-cell electrophysiological methods to characterize the activities of novel conotoxins. While single-cell techniques are useful for discovering activity against specific ion channels and receptors of interest, they capture only a limited portion of the biological activities elicited by conotoxins. My laboratory recently developed a new drug discovery strategy for venom components that target ion channels. I initially applied this strategy to primary cultures of rodent dorsal root ganglion (DRG) neurons. I used a calcium-imaging assay designed detect activity on any of the voltage-gated sodium, calcium or potassium channels expressed in a heterogeneous neuronal population. In this work, I demonstrate the efficacy of this approach with the purification of peptide toxins from the venoms of Conus musicus, Conus tessulatus, Conus caracteristicus, and Conus textile. I show that this discovery platform can aid in the prediction of a peptide's molecular target and mechanism of action. Further, genetic labeling can be paired with this drug discovery platform to identify peptide toxins with selectivity for specific neuronal subtypes.