Design and synthesis of α‐conotoxin GID analogues as selective α4β2 nicotinic acetylcholine receptor antagonists

Abstract

The α4β2 nicotinic acetylcholine receptor (nAChR) is an important target for currently approved smoking cessation therapeutics. However, the development of highly selective α4β2 nAChR antagonists remains a significant challenge. α-Conotoxin GID is an antagonist of α4β2 nAChRs, though it is significantly more potent toward the α3β2 and α7 subtypes. With the goal of obtaining further insights into α-conotoxin GID/nAChR interactions that could lead to the design of GID analogues with improved affinity for α4β2 nAChRs, we built a homology model of the GID/α4β2 complex using an X-ray co-crystal structure of an α-conotoxin/acetylcholine binding protein (AChBP) complex. Several additional interactions that could potentially enhance the affinity of GID for α4β2 nAChRs were observed in our model, which led to the design and synthesis of 22 GID analogues. Seven analogues displayed inhibitory activity toward α4β2 nAChRs that was comparable to GID. Significantly, both GID[A10S] and GID[V13I] demonstrated moderately improved selectivity toward α4β2 over α3β2 when compared with GID, while GID[V18N] exhibited no measurable inhibitory activity for the α3β2 subtype, yet retained inhibitory activity for α4β2. In this regard, GID[V18N] is the most α4β2 nAChR selective α-conotoxin analogue identified to date.

Stoichiometry dependent inhibition of rat α3β4 nicotinic acetylcholine receptor by the ribbon isomer of α-conotoxin AuIB

“…TxID Ser4 was suggested to have no interaction with the receptor using molecular modeling, explaining that its substitution to Ala was innocuous [45]. In contrast, a molecular model of the complexes involving GID* and the α4β2 nAChR suggested that the Ser side chain potentially forms a hydrogen bond with an Asp residue in the F-loop of the receptor [52], similar to our model of the rAuIB/α3β4 nAChR complex.…”

Effects of serum, enzyme, thiol, and forced degradation on the stabilities of αO‐Conotoxin GeXIVA[1,2] and GeXIVA [1,4]

“…The final fully folded GeXIVA[1,2], GeXIVA[1,3], and GeXIVA[1,4] peptides were analyzed by RP‐UPLC. Analytical liquid chromatography–ESI‐mass spectrometry (LC‐ESI‐MS) was used to monitor the reaction progress and measure the peptide molecular mass …”

“…Analytical liquid chromatography-ESI-mass spectrometry (LC-ESI-MS) was used to monitor the reaction progress and measure the peptide molecular mass. [3,13]…”

Conotoxins Targeting Nicotinic Acetylcholine Receptors: An Overview

“…An entire alanine scan of all non-cysteine residues revealed that most analogs had at least a 10-fold reduced activity at the α 4 β 2 subtype, which implies a highly specific interaction of all the amino acids and their charges with the receptor [93]. Recently, Banerjee and colleagues (2014) [94] provided more insight into α-conotoxin GID/nAChR interactions by designing the most α 4 β 2 selective conotoxin analogue identified to date, namely [V18N]GID. The authors observed a potential hydrogen bond interaction between the amide functionality of Asn 18 in [V18N]GID and the hydroxyl group of Y 195 of α 4 β 2 nAChRs, but not in the α 3 β 2 subtype.…”