TY - JOUR
T1 - Structure-Activity Studies Reveal the Molecular Basis for GABA
B -Receptor Mediated Inhibition of High Voltage-Activated Calcium Channels by α-Conotoxin Vc1.1
AU - Sadeghi, Mahsa
AU - Carstens, Bodil
AU - Callaghan, Brid
AU - Daniel, James
AU - Tae, Han-Shen
AU - O'Donnell, Tracey
AU - Castro, Joel
AU - Brierley, Stuart
AU - Adams, David
AU - Craik, David
AU - Clark, Richard
PY - 2018/6/15
Y1 - 2018/6/15
N2 -
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.
AB -
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.
UR - http://www.scopus.com/inward/record.url?scp=85046935767&partnerID=8YFLogxK
U2 - 10.1021/acschembio.8b00190
DO - 10.1021/acschembio.8b00190
M3 - Article
VL - 13
SP - 1577
EP - 1587
JO - ACS Chemical Biology
JF - ACS Chemical Biology
SN - 1554-8929
IS - 6
ER -