Cloning, Synthesis and Functional Characterization of a Novel α-Conotoxin Lt1.3

• Published in: Marine drugs 2018-03, Vol.16 (4), p.112
• Main Authors: Chen, Jinqin, Liang, Li, Ning, Huying, Cai, Fengtao, Liu, Zhuguo, Zhang, Longxiao, Zhou, Liangyi, Dai, Qiuyun
• Format: Article
• Language: English
• Subjects: Acetylcholine receptors (nicotinic); Amino Acid Motifs; Amino Acid Sequence; Amino acids; Animals; Bridges; Calcium; Calcium Channel Blockers - chemistry; Calcium Channel Blockers - pharmacology; Calcium channels; Calcium channels (N-type); Calcium channels (voltage-gated); Calcium Channels, N-Type - metabolism; Cloning; Conotoxins; Conotoxins - chemistry; Conotoxins - pharmacology; Conus Snail - chemistry; Ducts; Electrophysiology; GABABR-coupled Cav2.2; HEK293 Cells; Humans; Inhibitory Concentration 50; Isomers; Lt1.3; Neurotransmitters; Nicotinic Antagonists - chemistry; Nicotinic Antagonists - pharmacology; Oceans and Seas; Oocytes; Organic chemistry; Patch-Clamp Techniques; Peptides; Receptors; Receptors, Nicotinic - metabolism; Structure-Activity Relationship; synthesis; Toxins; Venom; Xenopus; α-conotoxins; α3β2 nAChRs; γ-Aminobutyric acid B receptors
• ISSN: 1660-3397; 1660-3397
• DOI: 10.3390/md16040112

α-Conotoxins (α-CTxs) are small peptides composed of 11 to 20 amino acid residues with two disulfide bridges. Most of them potently and selectively target nicotinic acetylcholine receptor (nAChR) subtypes, and a few were found to inhibit the GABA receptor (GABA R)-coupled N-type calcium channels (Cav2.2). However, in all of α-CTxs targeting both receptors, the disulfide connectivity arrangement "C¹-C³, C²-C⁴" is present. In this work, a novel α4/7-CTx named Lt1.3 (GCCSHPACSGNNPYFC-NH₂) was cloned from the venom ducts of ( ) in the South China Sea. Lt1.3 was then chemically synthesized and two isomers with disulfide bridges "C¹-C³, C²-C⁴" and "C¹-C⁴, C²-C³" were found and functionally characterized. Electrophysiological experiments showed that Lt1.3 containing the common disulfide bridges "C¹-C³, C²-C⁴" potently and selectively inhibited α3β2 nAChRs and not GABA R-coupled Cav2.2. Surprisingly, but the isomer with the disulfide bridges "C¹-C⁴, C²-C³" showed exactly the opposite inhibitory activity, inhibiting only GABA R-coupled Cav2.2 and not α3β2 nAChRs. These findings expand the knowledge of the targets and selectivity of α-CTxs and provide a new structural motif to inhibit the GABA R-coupled Cav2.2.