Beijing Institute of Biotechnology, Beijing 100071, China.
Institute of Physical Science and Information Technology, Anhui University, Hefei 236041, China.
Mar Drugs. 2018 Mar 31;16(4):112. 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 (GABAR)-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 GABAR-coupled Cav2.2. Surprisingly, but the isomer with the disulfide bridges "C¹-C⁴, C²-C³" showed exactly the opposite inhibitory activity, inhibiting only GABAR-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 GABAR-coupled Cav2.2.
α- 芋螺毒素（α-CTxs）是由 11 到 20 个氨基酸残基组成的小肽，具有两个二硫键。它们中的大多数能够强烈且选择性地靶向烟碱型乙酰胆碱受体（nAChR）亚型，而少数则被发现抑制 GABA 受体（GABAR）-偶联的 N 型钙通道（Cav2.2）。然而，在所有靶向这两种受体的 α-CTxs 中，二硫键连接方式“C¹-C³、C²-C⁴”都是存在的。在这项工作中，一种新型的 α4/7-CTx，命名为 Lt1.3（GCCSHPACSGNNPYFC-NH₂），从南海的毒液管中克隆出来。然后对 Lt1.3 进行化学合成，并发现了两种具有二硫键“C¹-C³、C²-C⁴”和“C¹-C⁴、C²-C³”的异构体，并对其进行了功能表征。电生理实验表明，含有常见二硫键“C¹-C³、C²-C⁴”的 Lt1.3 能够强烈且选择性地抑制 α3β2 nAChR，而不抑制 GABA 受体偶联的 Cav2.2。令人惊讶的是，但是具有二硫键“C¹-C⁴、C²-C³”的异构体则表现出完全相反的抑制活性，只抑制 GABA 受体偶联的 Cav2.2，而不抑制 α3β2 nAChR。这些发现扩展了 α-CTxs 的靶标和选择性的知识，并提供了一个新的结构基序来抑制 GABA 受体偶联的 Cav2.2。
