Oligo-basic amino acids, potential nicotinic acetylcholine receptor inhibitors

Oligo-basic amino acids have been extensively studied in molecular biology and pharmacology, but the inhibitory activity on nicotinic acetylcholine receptors (nAChRs) was unknown. In this study, the inhibitory activity of 8 oligopeptides, including both basic and acidic amino acids, was evaluated on 9 nAChR subtypes by a two-electrode voltage clamp (TEVC). Among them, the oligo-lysine K9, K12, d-K9, d-K9F, and oligo-arginine R9 showed nanomolar inhibitory activity on various nAChRs, especially for α7 and α9α10 nAChRs. d-K9 containing N-Fmoc protecting group (d-K9F) has an enhanced inhibitory activity on most of the nAChRs, including 47-fold promotion on α1β1δε nAChR. However, H9 and H12 only showed weak inhibitory activity on α9α10 and α1β1δε nAChRs, and the acidic oligopeptide D9 has no inhibitory activity on nAChRs. Flexible docking of K9 in α10(+) α9(-) and α7(+) α7(-) binding pockets showed particularly strong dipole-dipole interactions, which may be responsible for the inhibition of nAChRs. These results demonstrated that oligo-basic amino acids have the potential to be the lead compounds as selective nAChR subtype inhibitors, and oligo-lysines deserved to be modified for further exploitation and utilization. On the other hand, the toxicity and side effects of these nAChR inhibitory peptides should be contemplated in the application.