Structure-Activity Studies Reveal the Molecular Basis for GABA B -Receptor Mediated Inhibition of High Voltage-Activated Calcium Channels by α-Conotoxin Vc1.1

Mahsa Sadeghi, Bodil Carstens, Brid Callaghan, James Daniel, Han-Shen Tae, Tracey O'Donnell, Joel Castro, Stuart Brierley, David Adams, David Craik, Richard Clark

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

α-Conotoxins are disulfide-bonded peptides from cone snail venoms and are characterized by their affinity for nicotinic acetylcholine receptors (nAChR). Several α-conotoxins with distinct selectivity for nAChR subtypes have been identified as potent analgesics in animal models of chronic pain. However, a number of α-conotoxins have been shown to inhibit N-type calcium channel currents in rodent dissociated dorsal root ganglion (DRG) neurons via activation of G protein-coupled GABA B receptors (GABA B R). Therefore, it is unclear whether activation of GABA B R or inhibition of α9α10 nAChRs is the analgesic mechanism. To investigate the mechanisms by which α-conotoxins provide analgesia, we synthesized a suite of Vc1.1 analogues where all residues, except the conserved cysteines, in Vc1.1 were individually replaced by alanine (A), lysine (K), and aspartic acid (D). Our results show that the amino acids in the first loop play an important role in binding of the peptide to the receptor, whereas those in the second loop play an important role for the selectivity of the peptide for the GABA B R over α9α10 nAChRs. We designed a cVc1.1 analogue that is >8000-fold selective for GABA B R-mediated inhibition of high voltage-activated (HVA) calcium channels over α9α10 nAChRs and show that it is analgesic in a mouse model of chronic visceral hypersensitivity (CVH). cVc1.1[D11A,E14A] caused dose-dependent inhibition of colonic nociceptors with greater efficacy in ex vivo CVH colonic nociceptors relative to healthy colonic nociceptors. These findings suggest that selectively targeting GABA B R-mediated HVA calcium channel inhibition by α-conotoxins could be effective for the treatment of chronic visceral pain.

Original languageEnglish
Pages (from-to)1577-1587
Number of pages11
JournalACS Chemical Biology
Volume13
Issue number6
DOIs
Publication statusPublished - 15 Jun 2018

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