A novel µ-conopeptide, CnIIIC, exerts potent and preferential inhibition of NaV1.2/1.4 channels and blocks neuronal nicotinic acetylcholine receptors
Résumé
BACKGROUND AND PURPOSE The µ-conopeptide family is defined by its ability to block voltage-gated sodium channels (VGSCs), a property that can be used for the development of myorelaxants and analgesics. We performed a pharmacological characterisation of a new µ-conopeptide (μ-CnIIIC) on multiple preparations and molecular targets to gauge its potential as a myorelaxant. EXPERIMENTAL APPROACH The µ-CnIIIC was sequenced, synthesized, and characterized by its ability to block directly-elicited twitch tension in mouse skeletal muscle and action potentials in mouse sciatic and pike olfactory nerves. µ-CnIIIC was also studied on HEK-293 cells expressing various rodent VGSCs. Pharmacological investigations were extended to voltage-gated potassium channels and nAChRs to assess cross-interactions. Nuclear magnetic resonance (NMR) experiments were carried out for structural data. KEY RESULTS Synthetic μ-CnIIIC potently decreased twitch tension in mouse hemidiaphragms (IC(50) = 150 nM), and displayed a higher blocking effect in mouse extensor digitorum longus muscles (IC = 46 nM), as compared to µ-SIIIA, µ-SmIIIA and µ-PIIIA. μ-CnIIIC blocked Na(V) 1.4 (IC(50) = 1.3 nM) and Na(V) 1.2 in a long-lasting manner. Cardiac Na(V) 1.5 and DRG-specific Na(V) 1.8 were not blocked at 1 μM. An activity was unveiled on the α3β2 nAChR subtype (IC(50) = 450 nM) and, to a lesser extent, on the α7 and α4β2 subtypes. Structure determination of µ-CnIIIC revealed some similarities to α-conotoxins acting on nAChRs. CONCLUSION AND IMPLICATIONS μ-CnIIIC potently blocks VGSCs in skeletal muscle and nerve, and hence is applicable to myorelaxation. Its new atypical pharmacological profile suggests some common structural features between VGSCs and nAChR channels.