αO-Conotoxin GeXIVA disulfide bond isomers exhibit differential sensitivity for various nicotinic acetylcholine receptors but retain potency and selectivity for the human α9α10 subtype

Abstract

Nicotinic acetylcholine receptor (nAChR) subtypes exhibit distinct neuropharmacological properties that are involved in a range of neuropathological conditions, including pain, addiction, epilepsy, autism, schizophrenia, Tourette’s syndrome, Alzheimer’s and Parkinson’s diseases, as well as many types of cancer. The α9α10 nAChR is a potential target in chronic pain, wound healing, the pathophysiology of the auditory system, and breast and lung cancers. αO-conotoxin GeXIVA is a potent antagonist of rat α9α10 nAChRs, with the ‘bead’ disulfide bond isomer displaying the lowest IC50 of the three possible isomers. In the rat chronic constriction injury model of neuropathic pain, this isomer reduced mechanical hyperalgesia without affecting motor performance. Here, we report the effects of the three disulfide bond isomers of GeXIVA on human α9α10 nAChRs, other human nAChR subtypes, various rat nAChR subtypes, and 10 rat α9α10 nAChR mutants. The three isomers displayed only ~5-fold difference in potency on the human vs rat α9α10 receptors and had similar affinities at wild-type rat α9α10 nAChRs and all 10 α9α10 receptor mutants. From these findings, the binding site and mechanism of action of GeXIVA on rat and human α9α10 nAChR was deduced to be different from that of other conotoxins targeting this nAChR subtype. GeXIVA is therefore a unique ligand that might prove useful for further probing of binding sites on the α9α10 nAChR.

Nicotinic acetylcholine receptors in neuropathic and inflammatory pain

“…As previously discussed, RgIA4 has been shown to be an effective analgesic and prophylactic in the oxaliplatin model of neuropathic pain . Additional conopeptides have also been recently discovered that selectively target α9‐containing nAChRs . These peptides are structurally unrelated to RgIA and Vc1.1 yet analgesic, further validating α9‐containing nAChRs as therapeutic targets for the treatment of neuropathic pain.…”

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

“…The previous research showed that GeXIVA[1,2] and GeXIVA[1,4] (Figure ) were the most active isomers with similar IC 50 s on rat and human α9α10 nAChRs, GeXIVA[1,3] was the least active isomer . GeXIVA[1,2] and GeXIVA[1,4] (Figure ) had a similar IC 50 of 4.6 and 7 n m at rat α9α10 nAChRs, respectively.…”

“…For human α9α10 nAChRs, GeXIVA[1,2] and GeXIVA[1,4] had a similar IC 50 of 20 and 47 n m , respectively. While GeXIVA[1,3] displayed the lowest potency with an IC 50 of 116 n m at human α9α10 nAChRs . The most potent isomer was found to be GeXIVA[1,2], which blocked human α9α10 nAChRs almost completely at 100 n m (~100% inhibition), GeXIVA[1,4] was the second with a 67% inhibition at 100 n m .…”

“…The most potent isomer was found to be GeXIVA[1,2], which blocked human α9α10 nAChRs almost completely at 100 n m (~100% inhibition), GeXIVA[1,4] was the second with a 67% inhibition at 100 n m . But GeXIVA[1,3] was the least potent with only a 43% inhibition at 100 n m . GeXIVA[1,2] and GeXIVA[1,4] showed analgesic effect in rat chronic constriction injury model, and they are potential pain relievers to treat neuropathic pain .…”

Influences of disulfide connectivity on structure and antimicrobial activity of tachyplesin I

“…The α‐conotoxin AuIB isomers have substantial difference in their secondary structures and bioactivity, especially in their way of inhibiting nicotinic acetylcholine receptors (nAChRs) . Structure and activity relationship for the disulfide isomers of αO‐conotoxin GeXIVA, μ‐conotoxins KIIIA, μ‐conotoxin KIIIB, μ‐conotoxin PIIIA, and α‐conotoxin GI has been investigated, and the results suggested that in some cases, certain disulfide isomers could retain the bioactivity of the native peptide despite of their significantly varied secondary structures.…”