Analgesic Effect of the Lysine-Containing Short Peptide Is Due to Modulation of the Na_V1.8 Channel Activation Gating System

The present work continues our recent series of articles that aim to elucidate the ligand-receptor binding mechanism of short cationic peptides to the Na(V)1.8 channel in the nociceptive neuron. The applied methodological approach has involved several methods: the patch-clamp experimental evaluation of the effective charge of the Na(V)1.8 channel activation gating system, the organotypic tissue culture method, the formalin test, and theoretical conformational analysis. The lysine-containing short peptide Ac-KEKK-NH2 has been shown to effectively modulate the Na(V)1.8 channel activation gating system. As demonstrated by the organotypic tissue culture method, the studied short peptide does not trigger the downstream signaling cascades controlling neurite outgrowth and should not be expected to evoke adverse side effects. Conformational analysis of the Ac-KEKK-NH2 molecule has revealed that the distances between the positively charged amino groups of the lysine side chains are equal to 11-12 angstrom. According to the previously suggested mechanism of ligand-receptor binding of short peptides to the Na(V)1.8 channel molecule, Ac-KEKK-NH2 should exhibit an analgesic effect, which has been confirmed by the formalin test. The data obtained unequivocally indicate that the studied lysine-containing short peptide is a promising candidate for the role of a novel analgesic medicinal substance.