A 4/8 Subtype α-Conotoxin Vt1.27 Inhibits N-Type Calcium Channels With Potent Anti-Allodynic Effect

A novel 4/8 subtype alpha-conotoxin, Vt1.27 (NCCMFHTCPIDYSRFNC-NH2), was identified from Conus vitulinus in the South China Sea by RACE methods. The peptide was synthesized and structurally characterized. Similar to other alpha-conotoxins that target neuronal nicotinic acetylcholine receptor (nAChR) subtypes, Vt1.27 inhibited the rat alpha 3 beta 2 nAChR subtype (IC50 = 1160 nM) and was inactive at voltage-gated sodium and potassium channels in rat sensory neurons. However, Vt1.27 inhibited high voltage-activated N-type (Ca(V)2.2) calcium channels expressed in HEK293T cells with an IC50 of 398 nM. An alanine scan of the peptide showed that residues Phe(5), Pro(9), Ile(10), and Ser(13) contribute significantly to the inhibitory activity of Vt1.27. The molecular dockings indicate that Vt1.27 inhibits the transmembrane region of Ca(V)2.2, which is different from that of omega-conotoxins. Furthermore, Vt1.27 exhibited potent anti-allodynic effect in rat partial sciatic nerve injury (PNL) and chronic constriction injury (CCI) pain models at 10 nmol/kg level with the intramuscular injection. The pain threshold elevation of Vt1.27 groups was higher than that of alpha-conotoxin Vc1.1 in CCI rat models. These findings expand our knowledge of targets of alpha-conotoxins and potentially provide a potent, anti-allodynic peptide for the treatment of neuropathic pain.

Automated summary

A novel alpha-conotoxin, Vt1.27, was identified from Conus vitulinus in the South China Sea, showing inhibitory effects on rat alpha 3 beta 2 nAChR subtype and Ca(V)2.2 calcium channels. Specific residues were found to significantly contribute to its inhibitory activity. It also exhibited potent anti-allodynic effect in pain models.