Dimerization of α-Conotoxins as a Strategy to Enhance the Inhibition of the Human α7 and α9α10 Nicotinic Acetylcholine Receptors

Abstract

The affinity of α-conotoxins, a class of nicotinic acetylcholine receptor (nAChR) peptide inhibitors, can be enhanced by dendrimerization. It has been hypothesized that this improvement arose from simultaneous binding of the α-conotoxins to several spatially adjacent sites. We here engineered several α-conotoxin dimers using a linker length compatible between neighboring binding sites on the same receptor. Remarkably, the dimer of α-conotoxin PeIA compared to the monomer displayed an increase in potency by 11-fold (IC50 = 1.9 nM) for the human α9α10 nAChR. The dimerization of α-conotoxin RgIA# resulted in a dual inhibitor that targets both α9α10 and α7 nAChR subtypes with an IC50 = ∼50 nM. The RgIA# dimer is therapeutically interesting because it is the first dual inhibitor that potently and selectively inhibits these two nAChR subtypes, which are both involved in the etiology of several cancers. We propose that the dimerization of α-conotoxins is a simpler and efficient alternative strategy to dendrimers for enhancing the activity of α-conotoxins.

COVID-19 and nicotine as a mediator of ACE-2

“…As an example, α7-nAChR antagonists for the purpose of smoking cessation have long been proposed [7] and the idea of potentially repurposing these compounds for a pandemic with few therapeutic options currently available is certainly appealing. Whether α7-nAChRselective antagonists such as methyllycaconitine [8] and α-conotoxin [9] can meaningfully alter ACE-2 expression to prevent SARS-CoV-2 entry into the airway epithelium seems the next logical investigation in our furious pursuit for better therapeutics.…”

α-Conotoxin Peptidomimetics: Probing the Minimal Binding Motif for Effective Analgesia

“…Dimers of Vc1.1, [des-R13]-RgIA analogues, and PeIA showed concentration-dependent inhibition of human α9α10 nAChR with potencies increased by~4-, 7-and 11-fold over native values, respectively. The dimers also displayed interesting activity at human α7 nAChR, a sub-type recently shown to be over-expressed in several types of cancer together with the α9 subunit [56,57].…”

“…Recently, an alternative strategy to improve the potency of α-conotoxins toward α9α10 nAChR by formation of dimeric peptides was reported [56]. α9α10 nAChR expressed from a high ratio of α9 and α10 mRNA contained two neighbouring binding sites for α-conotoxins that could be concomitantly targeted by a single dimeric conotoxin sequence and therefore improve binding affinity.…”

α9-Containing Nicotinic Receptors in Cancer

“…In order to differentiate or analyze the effects mediated only by α9 nAChRs, the further use of α9-selective antagonists such as α-conotoxin Vc1.1 (Indurthi et al, 2014), α-O-conotoxin GeXIVA (Luo et al, 2015), RgIA4 (Romero et al, 2017), and PeIA (Mcintosh et al, 2005;Yu et al, 2018) is crucial. Dimeric constructs of the toxins PeIA, Vc1.1, and RgIA# ([∆R13]RgIA) have recently been designed, and all three constructs are more potent than their monomeric counterparts in relation to human α9α10 nAChRs (Liang et al, 2020; see Table 1).…”